Batteries in Parallel

[leemedic]

How many here have at least 2-12v batteries on their Montana in parallel? What would be the advantages and disadvantages?

[bncinwv]

Although not truly in parallel, I do have two 12v batteries installed with a marine-type selector switch that enables me to use one or the other or both batteries. Our primary use is to isolate one battery when we are cooling the fridge overnight before a trip (rig is housed in mini-storage). When the battery draws down overnight, I can switch to the other battery to start the generator, then switch back to charge the low battery. System works well for us, but as discussed our needs may not be the same as others.
Bingo

[Phil P]

Hi

The advantage would be longer lasting 12V system when not connected to shore power. The only disadvantage would be the loss of room in the battery storage location.

I have considered it but on doing some checking on amp-hour ratings I find that 2 6V golf cart batteries in series would be as good as or better than 2 12V batteries in parallel and would take very little more space than the present 12V battery.

Phil P

[1retired06]

Advantage: more 12V capacity. Disadvantage: little more weight and cost of second battery.

[DQDick]

We had that system for a couple of years and it's nice to be able to spend a night or two without power and not have to worry about drawing enough to damage the battery. Now we have solar and six golf cart batteries and as Bingo says "our uses and needs are now different".

[H. John Kohl]

You have received the answer in the above replies. As a "techie" I like numbers so I have a Bogart TM-2025RV monitoring system.
It tells me the Amp Hours available. Think of it as the gallons available on a fuel tank.

Once you know your usage especially if boon docking then you can properly size your battery needs as well as source requirements.

Good luck and safe travels.

[Irlpguy]

I switched from 2 - 12V batteries to 2 - 6V Golf cart type batteries when one of my 12V was failing. As indicated I believe that the 2 - 6V provide somewhat more capacity than does 2 - 12V, however they take up at least as much room as the 2 - 12V did, they are big heavy batteries.

There should be no worries about space for an extra battery whether you decide to add an additional 12V or go to the 6V in series.

It is not wise to add an additional new battery to a augment an existing batter unless that battery is also near new, having them replaced at the same time is best.

Either way you will gain more capacity which is always nice if you are away from power for a couple of days.

Good luck with your decision.

[Bigboomer]

As stated the answers above are all you need to decide, regardless of what you decide if you add a second battery that you need to add another vented battery box unless you go with AGM batteries. If you go with flood batteries they will off gas explosive Hydrogen gas so beware.

[boat391]

We use 4 6volts and 99%of our camping is dry camping have plenty of battery's to run the inverter just need to hook up to the gen. For charging up.Very happy with our set up. We have one battery box vented for off gassing just went to wal- mart and bought a plastic storage box big enough to house the 4 battery's and cut a vent hole both top and bottom and hooked up the flex hose that came with the Monty works great and seals tight. 4-6's gives us a ton of amp hours for dry camping. Hope this helps a little happy camping....

[Hooker]

As noted above, two 6v batteries are better than two 12v batteries.

[Lenny K]

I think that 6v batteries are the way to go as they accept many more deep discharges than a 12v. We have four 6v and used with our solar allows us to use everything except the AC and that big microwave which is useless as we also dry camp 99%.

[DQDick]

I will admit to having 6, 6v's and solar but you can use the microwave and the convection oven as long as you manage your other usage throughout the day and night. The microwave and convection oven's beginning draw is scary, but the microwave doesn't run for all that long and the convection oven uses much less once it's heated up. You just need to be able to closely monitor things and have a lot of sun where you are and have a generator if you really need it.

[Trailer Trash 2]

I have 2 12volt optima's and there heavy but there about the same as the 2 golf cart batteries in weight 75 lbs. each I used to have. I use them because I had them before and had good results with them along with no maintenance or venting. I would not worry about there weight because most compartments are capable of mounting a 5 KW generator in them that's much more than another battery. I don't have solar as most of the others that dry camp it, so the use of the big 6's are needed with them charging most of the time and high use.

[Lenny K]

quote:Originally posted by DQDick

I will admit to having 6, 6v's and solar but you can use the microwave and the convection oven as long as you manage your other usage throughout the day and night. The microwave and convection oven's beginning draw is scary, but the microwave doesn't run for all that long and the convection oven uses much less once it's heated up. You just need to be able to closely monitor things and have a lot of sun where you are and have a generator if you really need it.

I found that on my other 5th wheels that the microwave never seemed to put out a 100% when using an inverter and we're concerned about the microwave being damaged because of that.
I do have a trimetric so I'm able to monitor my batteries. As far as sun, we winter in Quartzsite and last year we used the generator twice. My batteries very seldom go less than 80% full and we use lots of power.

[DQDick]

My guess would be it depends on the inverter. Ours draws the same and seems to produce the same on inverter of shore power.

[7.3Ford]

Inverter rule of thumb is for every Amp AC, pulls 10 Amps of battery. Example, frig pulls about 2.5 Amps AC, and puts a battery load of 25 Amps.

The 30" microwave pulls around 14 to 18 Amps (from EMS 50 monitor), and the drain on the battery is around 140-180 Amps.

Here is my home built battery box, with vented cover.



When wiring your batteries make sure you pull the positive and negative off of opposite ends, or you first battery will be depleted at high rate instead of equally. John Kohl has a post on this somewhere, and a little research proved him 100% right. I had to redo where I pull the positive power.

Drawing below is for four Six Volts, but same applies for two or three 12 volts.

[Bigboomer]

Nice clean box John. I like where you have the shunt for the EMS.

Planning is everything when boondocking and using the inverter for the HD draw appliances. If you are sitting in full sun all day and the DW needs to cook in the MW you just need to pay attention to the battery draw down.

I added the wind turbine as an added measure for those windy nights and stormy days....just in case which should work well in the desert.

In general it is managing your lifestyle while boondocking and not expecting more than what you system can handle.

Like anything else in life, subscribe to the 6P's Rule (Proper Planning Prevents P*#s Poor Performance)!

[boat391]

7.3 Ford what a great post this is what I have only with 4 6's but same idea great post. Explains everything quite well.

[Lenny K]

quote:Originally posted by Lenny K

I think that 6v batteries are the way to go as they accept many more deep discharges than a 12v. We have four 6v and used with our solar allows us to use everything except the AC and that big microwave which is useless as we also dry camp 99%.

I got my trimetric hooked up today so I checked out how many amps the microwave would draw. It drew 112 amps which isn't so bad as my smaller microwave in my SOB drew 95 amps.
I was worried about nothing!

[poloace]

We have 2 12volt. Works great. We have a 80watt solor panel that keeps them charged.
As stated above, make sure both batteries are equal strength. As if you have 1 weak battery, it will bring the good one down with it.