Adding another 12 volt battery

Dakzuki wrote:
1) Convert to 6 volt true deep cycle (like GC) batteries (virtually all 12V wet cell batteries are not true deep cycle).

2) Get a multi stage converter. Most RVs are still coming with single stage converters that charge slowly and are not good for leaving your RV plugged in for extended periods. A multi stage unit like what Progressive Dynamics offers will charge faster and can be left hooked up indefinitely.

3) Convert to LED lighting.

4) Add solar. This will keep the batteries charging during the day, all day (if you are in the open).

5) One can also go a little nuts and install AGM batteries. They are sealed, charge faster than wet batteries (if your charger can supply the current), and are better at deep discharges. Down side is they are expensive.....like 3X. I did it anyway.

I agree with exception to to 3x the price mentioned in #5. Sam's Club HERE offers the standard 6V GC2 wet acid for $85 per battery and the sealed AGM for $180. I bought two AGMs because the increased height of the 6V batteries in my particular battery compartment, made checking fluid levels extremely difficult. I gave up my battery tray to gain the required height as shown below. It has also been very nice not to handle the batteries in that manner any longer, checking & adding distilled water, cleaning terminals and all that. Now I only pay attention when it's time to recharge. As mentioned in other replies, I also changed our converter/inverter settings to AGM charging.

Here is our twin 12V Battery Compartment with 6V batteries installed. I removed the battery tray to gain the extra height needed.


Here is our original 12V setup with the tray.



I installed a 3-function monitor on our control panel which displays battery voltage, clock, and temperature. It helps to have a constant reminder in our face to tell us when to recharge.

1) Convert to 6 volt true deep cycle (like GC) batteries (virtually all 12V wet cell batteries are not true deep cycle).

2) Get a multi stage converter. Most RVs are still coming with single stage converters that charge slowly and are not good for leaving your RV plugged in for extended periods. A multi stage unit like what Progressive Dynamics offers will charge faster and can be left hooked up indefinitely.

3) Convert to LED lighting.

4) Add solar. This will keep the batteries charging during the day, all day (if you are in the open).

5) One can also go a little nuts and install AGM batteries. They are sealed, charge faster than wet batteries (if your charger can supply the current), and are better at deep discharges. Down side is they are expensive.....like 3X. I did it anyway.

Here's a nice illustration of wiring 12v in parallel vs 6v in series. Extremely useful site. See like at bottom



12 volt side of life

We switched from a pair of 12V batteries in parallel to 6V batteries in series in hopes they will perform better and share the load better. It seemed with our two different sets of 12Vs, one battery always worked harder, drained faster, charged harder, then died sooner with acid boil-overs all along the way. Yes I wired them to share the load properly. And yes I always replaced them as a matched pair, not just one.

I hope the 6Vs will work more like batteries stacked inside a flashlight. They share the load much better, they drain in unison, and they last longer as a working pair. I also hope they will charge at about the same rate together, not one getting over-charged.

Beware though if changing 12V to 6V. 6Vs are taller and their foot print is not the same either. Read the specs on 6V batteries and compare them to 12Vs. They might not fit in your battery compartment.

I also agree about converting to LED lighting. That helps a lot with battery reserves. I converted all our lighting from incandescent & florescent to LED and noticed a big difference right away. We travel exclusively without ever hooking up to shore power so it is a big deal for us.

RedRocket204 wrote:
OP,

Keep in mind that if your current battery is older, and it sounds like it might be based upon non-specific time of "does not last long", you would be better off replacing the current battery and maybe considering adding a second battery. Do not just add a fresh, new battery in parallel to an old, failing battery as it will negatively impact the new battery. Likewise, both batteries should really be identical, including length of service, for maximum usage of both batteries.

Excellent advice for anyone going from one to two batteries! ;)

And not that it makes much difference as far as the answers go but this thread is in the CLASS C forum but you seem to have a 5th wheel.

First, have your present battery tested.
Then have the converter/ charger tested.
If either of those fail, fixing that might solve the problem.
But converting the lighting to LED is still a good idea.

If it ends up that you do need extra battery capacity, two 6 volts in series is a little better than a second 12 in parallel.

OP,

Keep in mind that if your current battery is older, and it sounds like it might be based upon non-specific time of "does not last long", you would be better off replacing the current battery and maybe considering adding a second battery. Do not just add a fresh, new battery in parallel to an old, failing battery as it will negatively impact the new battery. Likewise, both batteries should really be identical, including length of service, for maximum usage of both batteries.

Another thing you can do is replace the automotive incandescent lights with LEDs,,, They will burn at the same brightness but will draw much less power. You can save around 80% of DC power from your battery just doing this...

It all kinda depends what you want to do when camping. If you want to do alot of OFF-ROAD camping with no hookups then you need to plan out what you want to do when you are camping like this and change around your DC system accordingly.

We camp all the time OFF-GRID and get by just fine with around 255AHs of DC power...

Our concept is to run all the things we want to have on from the battery bank and only allow it to discharge down to its 50% charge state (Around 12.0VDC) by 8AM the next morning. Then when allowed we can fire up the 2KW generator and connect the trailer shore power cable to it and be able to use the on-board converter/charger unit to recharge our battery bank back up to its 90% charge state. This will give almost full performance out of the battery bank again so we can do all of this all over again the next day/night run off the batteries. We can do around 12-14 50% to 90% charge cycles before we have to do a full 100% charge state. This will take us around 12 hours to complete running our 0n-board converter/charger unit with shore power or generator connected. Since this is usually not allowed at camp site to run a generator that long this is when we usually head for the house and it there...

Been doing this idea for us since early 2009 and it works out just fine for us...

If you just want to run some lights over night of course you won't have to do all of this. I imagine once you start camping off the power grid you will fall in love with it and want to be able to run more things off your battery bank...

We do just about everything we would want to do at an Electric site running almost all of the things off of the battery bank with the exception of the High Wattage Air Conditioner and High Wattage Microwave unit. Everything else is fair game..

It is all in the planning...

Roy Ken

A better approach, but more expensive, is to replace the 12v battery with 2 6 volt deep cycle batteries in series.

This would be better than 2 12V in parallel? I'm assuming you're talking about what are commonly referred to as golf cart batteries?

Thanks!

Rich

Your single battery is a 12v battery. If you add another 12v battery in series it would be a 24 volt battery bank and it would kill almost everything in the RV.

If you want to add another battery, add it in parallel, pos to pos, neg to neg. Batteries in series add the voltage of the batteries, in parallel the available current is added.

Adding another identical 12v battery in parallel would not cause any problems and last twice as long. Depending on your converter it might take twice as long to recharge the batteries. It may also be desirable to increase the size of the wiring between the battery and the converter.

A better approach, but more expensive, is to replace the 12v battery with 2 6 volt deep cycle batteries in series.

Another approach to make the lighting last longer on batteries is to change the incandescent light bulbs to LEDs.