RV Batteries Questions and Answers

RV batteries are critical to most RVers, who should understand the basics about types and maintenance. Most of the lights, refrigerator mother boards, A/C control boards, furnace/water heater control boards in our RV’s rely on the best RV battery to provide a constant 12 volts. A weak or discharged battery can adversely affect the performance and longevity of the appliances they control. And improperly maintained batteries can mean unnecessary expenses to replace them before the end of their normal life cycle.

A weak battery will also need constant charging – putting an additional load on the charging system and if severe enough, will divert power needed for other applications. 

We rely on our batteries to provide power when boondocking and when otherwise without power. We have learned to love them and care for them. Battery power is an integral part of RV operating systems, so treat them right. 


There are three major type of batteries: flooded lead acid batteries, Absorbed Glass Mat (AGM) batteries, and Gel Cell batteries. We will only address the first two, since the Gel Cell batteries are no longer used much as RV batteries. 

There is an additional subdivision of whether the battery is a starting battery or a deep cycle battery. The difference between a starting and deep cycle battery is the way it is used. A starting battery will be rated in Cold Cranking Amps (CCA) and a deep cycle battery will be rated in Amp Hours (Ah). There is a drastic difference in how these batteries are built. The starting battery has many thin plates that provide a high rate of power over short periods of time, which is what you need to start an engine. A deep cycle battery has fewer plates but are much larger and thicker to provide power over an extended period of time. Because of this difference in design you should use the correct battery to fit the application. While you can use them interchangeably they work best when used correctly.

The primary enemy of any battery is sulfation of the plates caused by improper charging, lack of charging after use, or loss of water over the plates. Sulfation happens when sulfur molecules crystallize and form a coating over the lead plates. Sulfated plates are a triple whammy: sulfation causes quick discharge of a battery, decreases the life of the battery and prevents the complete charging of the battery. And according to one manufacturer is the primary reason why batteries fail.

Flooded Cell Lead Acid Batteries:

These are the batteries we grew up with. They require maintenance on a monthly basis to make sure they do not run out of water. Distilled water is what is recommended by battery manufacturers so you should never add tap water to these batteries. As part of the monthly maintenance, also check that the battery connections are tight and are corrosion free.

You can clean the battery casing with a solution of distilled water and baking soda. You can coat the battery posts and connectors with an anti-corrosion product that will help minimize the formation of corrosion.

Maintenance is required whether the battery is a deep cycle or starting battery. Unfortunately, many people don’t do much maintenance until they have a problem. By then it is usually too late to save the battery.

AGM Batteries:

These batteries typically cost twice as much as a flooded cell lead acid battery. However, you do get what you pay for.

They do not require you to add water because they are sealed. They also will last longer than a lead acid battery because they can be recharged more times (cycled) and can be discharged more deeply without damage. Maintenance of posts and terminals are the same as a lead acid battery.

Application – House Batteries:

AGM and Flooded Cell Lead Acid Deep cycle batteries come in two flavors: 12-volt and 6-volt (golf cart batteries). These batteries are what allow you to use your RV while not connected to power (we call this boondocking).

These batteries are commonly found in RVs to deliver power to the house part of the RV : things such as internal lights, vent fans, furnace fans, control boards on refrigerators/furnaces/air conditioners any other 12 Volt appliance residing in the RV (house). Because of this they are typically called house batteries.

House batteries take hours to fully charge. When they go bad, they appear to charge quickly and just as quickly loose the ability to deliver power.

Learn about RV Batteries

Here is an easy way to learn about battery ratings, types, sizes and configurations, battery maintenance, testing, charging, storage and more. Whether you own an RV or a boat you can watch this video as often as you need, making care and maintenance simple.

deep cycle batteries dvd
  In most cases, problems related to deep cycle batteries are usually a result of not understanding what is involved to properly maintain and care for lead acid batteries. 85% of all 12-volt batteries manufactured in the United States die before they should. This Deep Cycle Battery Care & Maintenance DVD was designed to help extend the life of your deep cycle batteries and to save you money. With a little routine preventive maintenance your deep cycle batteries can and will last as long as they should.

BUY RV Batteries Video

There is a lot to learn about RVs, and mistakes can be costly. Try to make the time to learn as much as you can about operating your RV, troubleshooting and resolving problems. You will find that as you learn about one topic, you learn something about other aspects of RVs.

RV Battery Not Charging

by Martin (Nebraska)

Question: I have a 2001 Gulfstream Class A motorhome and I’m having trouble charging the batteries while on shore power. I replaced the batteries already, so I know that is not the problem. The batteries also charge fine while the motor is running, or when I put the charger on them while on shore power. But they will not stay charged if I remove charger. So it seems that the problem is in the charger not working when plugged in,so what do I check now?

Answer: Based on your description, it seems that the problem is in the charging system that is supposed to operate while plugged into shore power. It could be the onboard charger itself, a relay/solenoid, a wiring problem into or out of the charger or perhaps an inline fuse.

You could try to look for loose connections or a blown fuse. It is worth a call to the RV manufacturer to see if they can help you troubleshoot and resolve the problem yourself. You will probably have to take the motorhome to an RV repair shop to diagnose and resolve the issue.

In the meantime, you could continue to use an external charger to recharge your batteries. However, there will be some challenges if you travel a lot. A heavy-duty charger is heavy and bulky and should be protected from the elements. In addition, not all campgrounds provide more that one power outlet.

Regarding charging systems in general, note that for lead acid batteries, you should use a three-phase charger that can automatically switch from bulk to taper to float charge. For AGM batteries, we recommend that use of an intelligent charger that not only does a three-phase charge but also has an AGM battery voltage setting.

Improving Battery Charging

by John

Question: I have a truck camper with two 12-volt 95 amp hour batteries. I would like to improve my battery charging. Mainly make it faster.
What I currently have are a 95 watt Go Power solar panel with a 25 amp regulator. Also there is the 45 amp converter. Neither of these really meet my dry camping needs. I also have a built in Onan 2500 watt generator.

What I am thinking about doing is adding something like a Samlex 12 volt 60 amp 2 bank automatic smart charger directly to the batteries. What I am not sure about is how this will effect the already existing 45 amp converter – which I still need since that has all the circuits. How do I disconnect the converter’s battery charging side and still be able to utilize the shore power converter side for all my circuits?

Thank you for your consideration of my question.

Answer: You should probably contact the manufacturer of the converter to see if they can offer you any suggestions. We really can’t speculate ourselves. We are also posting your question so that others may provide you with input.

RV Battery Dead

by Jim (Rochester, NY)

Question: I am new to RVs. I just bought a 2005 Forest River Sunseeker 2900 and had problems with the one side of the motorhome where you plug in the TV and DVD player and a few other electric outlets on the same side not working while plugged into my house or with the generator on.

So I checked the two 12-volt batteries and I had to add a lot of water to them both. After that, the generator wouldn’t start up either. So I plugged it into my house and the TV and DVD started working again. And the generator only starts while plugged in. I don’t know anything about motorhomes and am very confused.

Anyone have any ideas?


We will go out on a limb and say that your problem is that your batteries are dead and will need to be replaced. This is based on the situation your described. Once you added water to the batteries and connected to house power, the outlets started to work and the generator started. The charging system is providing some juice to the batteries and is allowing the generator to start and has enough power left over to power the outlets. The fact that the batteries were dry was causing the charging system to divert most of its power in an attempt to recharge the batteries.

There is a lot to learn about RVs, and trial and error could prove to be costly. You may find your best option is to take the RV to a qualified RV service center where they can diagnose and resolve your current problem. If you have the time and inclination, then you can learn as much as you can about operating your RV, troubleshooting and resolving problems. You will find that as you learn about one topic, you learn something about other aspects of RVs.

Charging Do’s and Don’ts:

  • Use a good quality three stage charger to charge your battery. If you have an AGM battery, make sure the charger has an AGM setting. If your charger does not have an AGM setting, consider not buying an AGM battery. Shortening the life of an expensive battery is not in your best interest.
  • Always fully charge a battery after use.
  • Don’t skip battery maintenance.
  • Never add tap water. If you have to add water, use distilled water only.
  • Don’t mix old batteries with new ones on a battery bank. A battery bank is one or more batteries connected in a common circuit.
  • If you store the RV without being connected to power, you may want to disconnect the batteries. The decision to disconnect the battery depends on how long you plan to store the RV, and phantom loads that draw down your batteries. In our coach, these phantom loads consist of a number of things that run in the background. Examples include engine and transmission ECMs (electronic control modules), LEDs, the electronics for the refrigerator and other things we probably are not even aware of. We have added solar panels which serve to keep batteries charged when storing the RV in the sunshine.If you decide to disconnect your batteries, use your battery disconnect switch if you have one. You could then use a clamp-on amp-meter to check that there were no remaining draws that might discharge the batteries. If you do not have a battery disconnect switch or want to be sure the batteries are completely disconnected, the proper sequence is to first disconnect the negative terminal, then the positive. When reconnecting, connect the positive, first then the negative. If you have multiple batteries, you might want to take a picture or draw a diagram before you start disconnecting things, as a reminder for when you hook things back up.If you are going to store the RV for a long period of time with disconnected batteries, it is best if you take out the batteries and put them on a charger. A fully charged battery not connected to a charger will self discharge 1-15% per month.
  • If your charger has a setting for equalization use this setting as recommended by the battery manufacturer. Periodic equalization helps to break up sulfation of battery plates and will improve the overall performance of the battery.

Wiring Batteries

by Brandon (NY)

Question: A little new to the travel trailer scene. I have a 29 ft. 2008 Keystone Hornet 26BH. My wife and I do a lot of dry camping at state campgrounds and really enjoy our trailer. However, at the current time we don’t have the funds for a good, quiet generator, but are saving for a nice quiet inverter and generator.

Anyhow, because of this I recently wired a second 12 volt deep cell marine battery in parallel with the deep cell battery that came with our trailer. I have the trailer plugged into our house by way of 200ft extension cord.

I wired it and had it unplugged and the battery meter on the trailer didn’t register a charge. It has been plugged in for a little over 24 hours and when I checked I had just wired the second battery. Is this a wiring problem or a battery problem or am I missing something? Any help is good help. Thanks.


There are several things that come to mind in trying to help you diagnose the charging problem.

Let’s start with the correct way to connect a charger to the 2 batteries you connect in parallel. Here is a link that shows how to connect a charger for your specific configuration: http://www.batterytender.com/Connecting-Chargers/. Go to #9 that shows 2 batteries in parallel being charged by a single charger. If you are not connected as shown then you need to correct the wiring.

Other things to check:

Have you verified that the fuse or breaker for the on board charger is good?
Have you checked all your battery connections to make sure they are good and tight and there is no corrosion?
If everything is connected correctly and the charger is good then it is time to look at your extension cord. We suspect that your 200 ft. extension cord could be the problem, unless your extension is 10 gauge or better. With such a long run you may be losing too much amperage due to resistance.

We hope this has helped. Please let us know what the outcome is, as we are very interested in your attempt to extend you dry camping capability.

Update From Reader: Okay so after camping for the weekend back in the beginning of August, I found the cause was not the cord at all, but rather, the circuit breaker on the outside of of the TT. So I replaced this and got a deep cycle battery and essentially had no further problems…Just wanted to give you guys a heads up. 

It appears that the cord would be the issue. I have the trailer plugged into the cord – it appears that it can run the light, but not much else. So it seems to me, as you suggested, the power coming that far on a series of extension cords has lowered the available watts to power things and isn’t charging the batteries.

I will run the generator that I do have (FrankenGenerator = Very loud) to see how that recharges them. Furthermore, I will be off to go camping tomorrow and will be driving about 2 hours or so which should charge them pretty good as well. Thanks for the help – much appreciated.

Replacing Batteries

by Allison (Baltimore, MD)

Question: Yesterday my batteries were stolen from my RV. Unfortunately, I do not know what batteries were on the camper, so I am not sure what to buy. Looking at the manual and online have not provided me any useful information.

I have a 2004 Four Winds Toy Hauler, a 23SRVT. Also, the jerks cut the wires to my jack, so any suggestions for repairs?

I am new to the world of RVs. I just purchased this camper in June but I have been on three trips so far. I have been told I don’t need two batteries – is this true for the model I have? I know I need a 12- volt deep cycle but I do not know what amperage to get? Please help!

Sorry to hear of your bad luck on the theft. If we were in your position, we would first contact the manufacturer to ask what they suggest. There are so many variables that that it is difficult to be specific about what your camper needs. (Input welcome from anyone with the same brand and model RV!)

If you cannot get assistance from the manufacturer, then here is how to figure out what you need:

Start by determining the capacity of your charger and converter, so you can determine the maximum safe load on the converter and charger.

This will in turn let you determine the maximum sized battery(s) that the charger and converter can support. Converters are rated in amps and watts. Deep cycle batteries are rated in amp hours.

Lets say you had two batteries that were rated at 210 amp hours and were connected in parallel. There is a rule of thumb that says divide the amp hours by 5 to get the charging amps required. Since the batteries are in parallel you take 210 and divide by 5 for a result of about 40 amps. This means that your inverter/charger would have to provide a minimum of 40 amps to safely charge your batteries.

You also need to consider how much reserve battery power you need for those times that you will be boondocking. That may be the reason that you had two batteries.

Regarding the wiring to a the jacks, we suggest you look for a qualified RV facility in your area, perhaps ask the manufacturer for a recommendation.

Hope this is of some help. Please let us know the final outcome. Other input welcome.

Search our Site for other related topics, such as battery, power, electricity, converter, inverter, amp and so on.

Update: My husband and I ended up going to our local battery warehouse and they directed us with the correct battery and supplies needed for the repair and replacement. They were very helpful and we had the camper up and running for the following weekend. Unfortunately we found out, while making the police report, that there is an ongoing problem with batteries being stolen from boats and campers in our area. Therefore, we found a battery case locking system to protect our new battery. Spending an additional $25 for the battery protector is worth it since one battery costs roughly $190. We ended up only buying one battery because we figured out that is all we needed, as we usually camp where there is power supplied. The battery gets the most use from the automatic jack. We appreciate your response, you supplied a lot of useful information. For anyone who is interested in buying a battery lock I am including their information. B&D RV BATTERY LOCK website: www.b-drvbatterylock.com email: fox@b-rvbatterylock.com Phone: 801-897-0625. Thanks for your input!

5th Wheel RV Batteries

by Kim (Punta Gorda, FL)

Question: What should I use for batteries? I need to replace my battery in my 5th wheel. I have heard about using golf cart batteries. Should I use 2 or 4?, and what should I use to connect them? Or should I use 2 RV/Marine batteries? Any help appreciated.

Answer: Replacing your battery can be simple or complex. You can go the easy way and replace the current battery with a like product or you can upgrade the batteries and type depending on how you plan to use the RV.

Certainly golf cart batteries would work fine. If you have one 12 volt battery now, you will need two 6-volt batteries. You just have to have the room for two batteries and to have them installed correctly. An advantage is that golf cart batteries are deep cycle batteries. You will have to make sure that your battery charging system is up to the challenge of charging deep cycle batteries and can provide a three stage charge to prolong their life cycle.

As for connecting them, the connections are simple enough. You will need good quality battery cables and connectors – these you can get from any battery or golf cart supply center. If you are familiar with battery wiring and are comfortable working on live batteries, then you can do all the work yourself. Here is a link that will show how to connect the batteries: http://www.zbattery.com/Connecting-Batteries-in-Series-or-Parallel.

However, if you are not comfortable working with live circuits leave this to the professionals. A small mistake can be very costly so do not be pennywise and dollar foolish.

Another option, if you have the room and charging capacity is to install two deep cycle 12-volt batteries. This is a good option if you do a fair amount of boon docking between connections to the grid.

As for marine or RV batteries that is just a general classification as to their application. When I buy batteries for my RV I look for deep cycle batteries from a reputable manufacturer that makes deep cycle batteries. You can buy a marine battery and it may or may not be a deep cycle battery, ditto for any “RV” battery. Be aware that deep cycle batteries are rated in Amp Hours not CCAs (cold cranking amps).

Another discussion is what type of battery, lead acid (flooded cell) or AGM. Flooded cell batteries require periodic maintenance (adding distilled water). AGM batteries do not require maintenance other than keeping the terminals clean and tight just like the lead acid batteries.

There are advantage and disadvantages to both. Lead acid batteries are old technology but are much less costly than the AGMs of similar capacity. AGM batteries can be discharged deeper without damage and will recharge faster but are twice as costly as their lead acid counterparts.

House Battery Charger

by Chris (Petersburg, VA)

Question: I have a 2001 Thor Hurricane 32ft. The coach has 3 house batteries which I just replaced. After about 1 day of use running heater and lights the batteries have been drained.

I have looked through the coach trying to find a charger. The coach has not been used in a while but I do not ever recall having these batteries drain on me like this. Is there a onboard charger? Any trouble shooing advice?

You did not mention if you were plugged into external power while you were running the heat and lights. If you were plugged into power, then you have a charging system problem.

If you were not, then it does not surprise me that your batteries are dead. If I used the heating system and lights on a cold day my batteries would be drained too – if I were unplugged from power.

I am assuming that you do not have an owners manual which tells you if you have an on board charger. I visited the Thor website and looked for an owners manual for your year coach – unfortunately I was only able to locate a manual from 1996 and one from 2007. However, both refer to a charger, so I can only surmise that you also have a charger. (You might try contacting Thor to ask for an owners manual).

From your question, I can’t tell if you have a generator; or if you replaced the original batteries with the same amp hour ratings; if the new batteries are deep cycle AGM or flooded lead acid batteries (there is a difference in charge rates); or if the batteries were recharged successfully after they went dead. So I will make some assumptions and try to provide some general assistance.

Caution: If you are not familiar or comfortable working on live circuits do not attempt to go any further. Please take the RV to a repair facility. You do not want to take any chances and create a bigger problem than you already have. If you feel comfortable please read on just be careful, the life you save maybe your own.


Your flooded lead acid batteries are still dead.
The RV has not been plugged into power.
The RV engine has not been started.
If you have a generator, it has not been started to recharge your batteries.
You have a volt meter that can read DC voltages in the range of 0 – 24 volts

Trouble shooting the charger:

Make sure all of your battery connections are clean and tight and the water level is adequate. Do not add water at this time unless the plates are showing. Add water (distilled only) only after the batteries have been fully charged. It may take hours or days depending on the charge rate and the batteries to reach a full charge.
Locate you charger and associated wiring and fuses. Contact Thor Industries, as they may help you identify where you can find the charger.
Make sure all wiring, fuses and or circuit breakers associated with the charger are good.
While unplugged from power and with the RV’s engine stopped, take a reading of the state of each of your batteries. They should read at least 10.5 volts. If they are lower than 10.5 volts you may have damaged the batteries and they may never recover.
If the batteries are at 10.5 volts, start your engine and take another reading. Each battery should now read at least 13.6 volts or there is a problem with the engine charging system. Do the same test with engine off and plugged into outside power (Ditto on the readings).
If you have a generator start it and perform the same test. The idea is to try to isolate the problem. If one or more of the charging systems are good then that should point you to the faulty charging system. If all the charging systems are good then it is time to take your RV to a service center to have them help isolate the problem.

Please let us know the outcome, as it may help other RVers.

Heat pump use on battery

Question: Can I run my heat pump on battery?

Answer: Probably not. We assume your heat pump is part of a combined unit with your air conditioner. We have two roof-top AC/heat pump units. Our RV is not even wired to allow us to try run them off the battery/inverter. If we are boondocking and need to use the AC or heat pump, we turn on our generator.

It’s likely that your RV is not configured to allow running the AC/heat pump from battery power. Even if you can do it, it would probably deplete your battery bank very quickly. But who knows, perhaps your RV is non-typical in this regard. If so, we suggest you contact your manufacturer for their take on the subject.

The following chart provides some information on electrical draws of various appliances.

Appliance Wattage and Amperage Consumption (Approximate)
Appliance Watts*   Amps*
Air Conditioner 13,500 Btu 1700
Air Conditioner 15,000 Btu 1950   16
Blender 300   2.5
Coffeemaker 900   7.5
Computer (desktop) 100   8
Computer (printer) 240   2.0
Converter (30 amp) 550   4.5
Converter (40 amp) 650   5.5
Converter (75 amp) 1050   8.5
Heater (electric) **   12.5
Hair Dryer 1200   10.0
Iron 1200   10.5
Microwave 450 Watt 900   7.5
Microwave 650 Watt 1,300   10.5
Refrig/Freezer 600   5-8
TV 100   .75
TV Satellite & Receiver 170   1.5
VCR 90   .75
Washer/Dryer (RV type) 1900   16.0

* Normal running operation amps/watts; start up may draw more power
** See wattage info for your specific heater

Dead Batteries

by Gordon (Baton Rouge, LA)

Question: I have a 1998 Gulfstream Scenic Cruiser that works fine when plugged in to a power source and also works fine when the generator is running. But when I turn off the generator, the power panel shows that the batteries are dead and nothing works including restarting the generator.

If it is plugged into a power source when the generator is shut off, the power panel shows the same but in a short while (20-30 minutes) it shows the batteries are good again. Please help.

Answer: You may have multiple problems so let’s address them one at a time.


A badly sulfated battery will appear to recharge within 20 – 30 minutes. This means that it is only accepting a surface charge. That is why your battery(s) appear to recharge in such a short period. If my batteries are at half capacity (about 12.2 volts), it usually takes anywhere from two to four hours to reach a float charge. By the way, we had two deep cycle AGM 8D batteries that started to do this and eventually had to replace them.

Diagnosing the batteries

Start by cleaning your battery terminals, and check that the battery connections are tight. With the generator and shore power off, take a voltmeter and read your voltage directly from your battery terminals.

If the voltage is under 11.8 volts, your batteries may not be salvageable. Take your batteries to a trustworthy battery shop to have them load tested. If they are the lead acid type, also have them check each cell with a hydrometer to see if there is a bad cell. You could do this yourself with the proper equipment, but it is easier to have a trusted professional do this.

If the voltage is over 12 Volts or better than there is hope to save the batteries. You may have to equalize the batteries several times to clear the sulfated crystals from the battery plates. Caution: if you are using AGM batteries read your battery manufacturers’ recommendation on equalization, since they may recommend that you do not equalize an AGM battery.

Put a load on the batteries (no shore or generator power) and wait till the voltage drops to about 12.2 Volts. Plug the RV back into shore power and see how long the battery(s) takes to recharge from your shore power. If it now takes hours then you have successfully eliminated the sulfated battery problem.

Generator system:

When your generator is operating, it should be charging your batteries. From the information given, it appears that the generator is producing power but the power is not getting to the charging circuit.

Diagnosing the Generator System:

If you have not done so, check the circuit breakers on the generator and reset them. While you are at the generator, take a voltage and amperage reading while the generator is operating and shore power is off. You should see 120 Volts. See your generator specs for proper amperage output.

Next, start by checking connections between the generator and the inverter/charger or converter. Look for a blown fuse, loose or broken wires. If you have not already done so, clean your battery terminals and check that the battery connections are tight.

Go to the battery compartment and with the generator and shore power off, take a voltmeter and read your voltage directly from your battery terminals. As previously stated, the voltage on a good battery should be above 11.8 Volts.

With the shore power off, have someone start the generator (you may have to charge the batteries to do this) and take voltage readings directly from the battery terminals. You should see at least 13.2 volts.

If you do not see a jump in voltage after a few seconds (10-20 seconds), then you have a problem in one of the following components: generator, wiring or one of the components between the generator and the batteries. The typical components you might find are an in-line fuse, power transfer switch, relay, diode or solenoid, and charger/inverter or converter. Your particular unit may have one or more of these components.

Good luck in diagnosing the problem. Please let us know the outcome.

Charge Batteries over the Winter

by Greg (Mechanicsburg, PA)

Question: I have a Freedom 458 series COMBI inverter/charger Model 15D, with 4 marine type batteries wired in series. I would like to keep the batteries in the RV and simply keep them charged via 120AC but my used RV dealer says I should either take them out or start the generator and engine once a month to keep them charged.

Is it possible to keep it plugged into AC with this type of charger/inverter? I’m wondering if this unit will automatically stop charging when the batteries are fully charged and then start up again when they run down?

Answer: The best information I can give you is a link to the owners manual for the Freedom 458 series combo inverter/charger Model 15D. I read the manual and the good news is that if your inverter/charger is correctly programmed and working properly, it will keep your batteries properly charged while plugged into 120 Volt AC.

I don’t know why the dealer said to take the batteries out or run the generator or engine to charger them. Unless he knows that your particular RV’s inverter/charger is not working properly.

To learn everything you need too know about your inverter/charger please go to this link: www.serenitysys.com/beaver/archives/FREEDOM_%20458%20Series_COMBI_Inverter_%20Manual.pdf.

Keep in mind is that unless you have AGM batteries you will have to check the water in the batteries once a month to make sure that they do not run out of water. Please remember that if you need to add water, it must be distilled water. Tap water will destroy batteries over time.

While you check water levels also inspect the battery terminals for corrosion and tightness. If you see corrosion you will need to remove it using a commercial product for that purpose or use a baking soda and water solution with a soft non-metallic bristled brush to remove the corrosion.

Reader: Thanks for the info. I kind of thought that was the case but the documentation was not clear to me (a novice). I really appreciate your response.

Battery Power to Camper

by JMK (Davidsville, PA)

Question: My battery is fully charged and the inside lights work when I plug into AC power, but not off straight battery power. Fuses look fine.

Answer: Lets start with the most obvious problems. First, do you have a battery disconnect switch? Is it activated to shut off power from the battery? If it is, then turn it off and you should have your lighting back.

Next, is the lack of 12 volt power just at the lights or are all 12 volt appliances not operating (i.e., fans etc.)?

The next few steps require some knowledge and comfort working on a live 12 volt circuit. If you do not have experience or are uncomfortable then take your rig to a qualified repair facility. If you attempt to go further and you make a mistake then you could be letting yourself in for a very costly repair and or injury to yourself or others. Please do not proceed unless you have experience with trouble shooting 12 volt systems and have physically disconnected from shore power.

Are you battery connections clean and tight? If not, then clean the connections and tighten the cables. Did that fix the problem?

The next step is to trace the 12 volt wiring from the battery to the converter:

Are there broken wires (positive or ground) from the battery that would affect all lights? This step will require that you trace the positive and ground leads from the battery to the fuse or fuses. Your best option is to use a volt meter and test until you do not get a reading.

The power leads will eventually go back to your converter and the DC breaker box. Have you ever seen the inside of a converter? Can you identify the battery connections. If not, take your rig to a repair facility. If you have seen the inside of a converter and are comfortable working on a live 12 volt circuit then proceed to see if you have 12 volt power at the converter.

The converter is the common point from where 12 volt battery or 120 volt power is distributed to your lights and appliances. If you have 12 volt power at the DC breaker box connections and the converter, then the converter is faulty. There are several components in the converter that can go bad.

So here is a link to a very experienced RV’er that has taken the time to download diagrams, trouble shooting and repair information on his particular brand of converter and another brand. Since different converters generally do the same thing, most of what is in the link will suffice for other brands as well. Here is the link.

You can also Search our Site for other posts related to batteries, electric power, converters, generators and so on.

Battery Help

Question: I have a 1997 Coachmen Catalina Sport. Everything that runs on 12-volt makes the battery low. I have to start the engine for a while and it charges, but in a little while I have to do it all over again. I’ve had the battery checked and was told it’s okay.

Answer: Without more detail it is difficult to give a simple or specific answer, but here are a few thoughts and speculations on the subject.

Just because your battery tests OK, it does not mean that it is OK for the power demands you place on it. From you description of the problem and how you recharge the battery, I suspect that the battery is not being fully charged before you start drawing power again.

If the battery is in fact good, then it must be that the power demands you are placing on it are too great for that battery. So many things can affect the usable energy stored in a battery that it is not possible to explore all the reasons. But perhaps some of this will point you in the right direction.

Possible problem 1: Battery not good:

Since you are running your engine and using your alternator to charge your battery I can only speculate that you are not running the engine long enough and that the battery is only being partially charged. I also have to speculate that you are using the 12-Volt appliances because you are not plugged into power.

The engine and alternator must run at a fast idle and for as long as it takes to cover the equivalent of twenty to thirty miles for the battery to be fully charged, and much longer if the battery is a deep cycle battery. What you seem to be doing is only giving the battery what is called a surface charge. This surface charge only lasts a few minutes and the battery soon starts to deplete its power reserves.

If you do this long enough the battery will become sulfated and its useful life will be shorter and shorter with each partial charge. In the end you will not be able to recharge the battery and you will have to replace it.

You said the battery tested OK but how far did you drive to have the battery tested? If you drove more than thirty miles, you may have recharged that battery sufficiently to have it test OK. Did the shop do a load test on the battery? Did they test each cell to make sure the battery did not have a dead cell? All food for thought. You may need to get a new battery.

Possible problem 2: Charging System not working correctly

If you are plugged into power and the 12-Volt appliances are running your battery down, then you have a charging system problem. More specifically, the charger that is supposed to charge your house battery while you are plugged into power is not operating properly. You should probably go to a qualified RV shop that specializes in RV electrical systems.

Possible problem 3: Battery not adequate for power needs

The other possibility is that the battery is not capable of providing all of the power you need or for as long as you need it. You need to check the battery’s load capacity to see how it compares to the power requirements placed on it. If you have not already done so, I suggest that you make a list of each of the 12-Volt appliances that run off your battery while the engine is off. Then calculate how much each appliance draws on an hourly basis in AMPS.

Determine how many hours you expect to use each appliance. Once you have all this data you can calculate how many total AMP hours are required for your needs. The number of AMP hours calculated will allow you to determine if your battery has sufficient Reserve Capacity (RC) to accommodate all of the power requirements.

The solution may be as complex as redesigning your 12-Volt system to accommodate more/bigger batteries or as simple as just managing your power needs to match the battery’s power capacity.

P.S. Just FYI in case you are using a car battery: Car batteries, also called starter batteries, are rated in Cold Cranking AMPS (CCA) and do not have sufficient reserve capacity to run 12-Volt appliances for very long. This could be your problem.

Reader Comments: I second Smokey’s comments and thought I would add a little myself. First off, they are referring to the Battery? If it is truly just one deep cycle battery, that sounds like an issue in itself. My current class-C coach came with 2 deep cycle coach batteries and I added a third. Knowing that I do a ton of NF camping (with no Hookups)I opted to add the 3rd battery, 280 watts of solar panels and a good charge controller. This gets me about 4 hours of TV/satellite a night with a 2000 watt inverter and a full night of heat at just under freezing temps. 2 to 3 hours on genie (55 amp charger) in the am and the sunshine the rest of the day brings me back to full charge. The main thing to remember is deep discharged deep cycle batteries, take a deep long charge to recover. Running the main engine for 30 min. or even a couple hours will never fully charge a deep cycle battery. Once the main engine battery is at full charge the charge amperage drops off to all batteries.

Question: My batteries acted like they were dead and indicated by the monitor panel. Of course plugged into 110 lights and everything works fine.. But when disconnected and I turn on a 12 volt light on or pump, it goes on momentarily then goes off and everything is dead. Obviously I charged the batteries independently, one would not come up to full charge so I replaced them. I still have same problem when turning light on, goes off and everything is dead. Also the propane monitor beeps when you turn on and off a light. Any ideas??

Answer: Since you have replaced the batteries and you are still experiencing the same problem we suggest that you take the RV to a service center to identify the problem. Although, we could make guesses at what is wrong your best course is to seek professional help. We do know that the problem is on the 12 volt side since things work when plugged into shore power.

Here are a few things to think about:

Have the new batteries load tested to ensure you did not get a bad set also check the connections to make sure they are properly connected (+, -) at the battery terminals
You might have a faulty ground connection – I recently discovered a bad ground that was causing one of my heater fans, a light and the propane detector to fail.
Your inverter/converter could have a bad connection on the 12 volt side.

Reader Update:

Did everything you said pretty much before I sent my message to you. I checked all main 12v circuits for shorts, none. Disconnected Every 12 volt device I could (i.e… Water heater, pump, propane detector, converter, a few lights…then I took every fuse out of fuse panel and started putting them back in until the problem surfaced again.

I discovered the 2 of the main lighting circuits would recreate the problem if I turn something , anything on. Then I got to thinking, everything worked on the shore power side through the converter….and my old batteries were not getting a charge, so I found a 40 amp auto resetting circuit breaker under the trailer at tongue.

It was energized by the battery then lead to the converter, scratched my head and can’t ever remember ever having to replace an auto circuit breaker in any vehicle I have ever owned. Had a new one on hand, disconnected the old one, re hooked everything up and ALL IS WELL, works fine now. So obviously the breaker had weakened and gone bad. Made sense when I thought about it, allows converter to energize 12 volt system cause it has its own fuse. But when you try to draw power from batter, it tripped – go figure.

Well after a day and a half of fretting and taking a 3rd of the trailers electrical system apart. I learned a lot and saved a few bucks I’m sure. Thanks for your response again and I hope no one else ever has the problem but Maybe my experience will help if they have a similar problem.


Reader Comment: I want to take a moment and hopefully fill in a little as I feel that there are still missing parts to your explanation for this person; I feel that this person was not only asking what you wonderfully explained, but also that this person does not understand HOW to use their 12 volts system.

This person needs to understand that if they want to only use their 12 volt system they are going to have this same issue forever, meaning that the 12 volts system in most rv’s does not last that long (as long as his question feels to me) as when you use your lighting, the fridge, the hot water heater, and so on you will run your batteries down rather quickly in most RV’s. And like most – if they want to boondock will need to do some major upgrades to their battery system to get it where it might work, the batteries would most likely need to be replaced (not enough info).

The issue with running the engine will not work (as you state) because it will take hours to charge a rundown battery in this manner, and most likely will never be fully charged. The charging system will need upgrades (solar, converter) and also might still need a portable generator to still make up the difference (again I am guessing because of lack of information). By in my option this person needs to fully understand the sum of the batteries is much bigger than just the batteries! So I hope this might fill in more holes for this person and they can better enjoy their camping experience.