Connecting a second 12VDC battery

Boomerweps wrote:
Trailer and battery brand new two weeks ago. Got it. Just hook 'em up in parallel. (I do have a bit of electrical training but I was overthinking things, I guess ;(
I keep looking at solar but I haven't even taken the camper out of the yard, yet ;)

Unfortunately you haven't told us just which battery you have but if it's a garden variety G24 that most dealers would supply with any new trailer unless the purchaser indicates otherwise you might want to ask if you can return it and buy two 12 volt G31s or two 6 volt GC-2s, either combination of which would provide ~ 220 AH of reserve capacity. You also really need to investigate just which converter is in this trailer 'cause if it's a WFCO you'd probably want to replace it right from the get go ... good enough for those who normally camp on electric sites but certainly far less than ideal for those who dry camp, especially those with $$$ invested in substantial battery reserve. ;)

Agree with:
Cabling as twice-pictured above
12's MUST be very much alike! They DO NOT play well together. I bought a C with 2 new Diehard deep cycles and could NOT keep both alive. Gave up and went to just one.
To add, I think the quality of your Converter/Charger can marginally improve or reduce the results.

Trailer and battery brand new two weeks ago. Got it. Just hook 'em up in parallel. (I do have a bit of electrical training but I was overthinking things, I guess ;(
I keep looking at solar but I haven't even taken the camper out of the yard, yet ;)

http://www.batterytender.com/connecting-chargers#two-batteries-parallel-one-charger

add solar to maintain the connected pair

let us know in 15-20 yrs how this 'age mismatched' pair compared to a replacement age matched pair.

BFL13 wrote:
Use the diagram shown above. Note that you get more than twice the time at the same amps draw by having that second battery used together. So don't use them one at a time. (Peukert works for you!)

SoundGuy wrote:
OTOH if the OP's original battery has been in use for awhile but he still wants the benefit of having two batteries available for dry camping then he should use them separately to avoid the old original from degrading the newly purchased battery. He can easily accomplish this by wiring the batteries with a dual battery disconnect switch such as the Blue Sea m-Series 6007.

BFL13 wrote:
True. However you can get away with using two dissimilar batteries together for a few days camping, but then be sure to separate them at home to recharge each to its own True Full.

Ever the more reason for the OP to invest in a Blue Sea #6007. ;)

To the OP
People here try to make your question complicated.
Just exclude the fanatical comments, and parallel your 2 batteries together.
There is only 1 important requirement, and that is that your existing battery is in good condition, and if it is a typical lead acid, the other one must be also. It will more than double your AH capacity.
Do not use them separately.

SoundGuy wrote:

BFL13 wrote:
Use the diagram shown above. Note that you get more than twice the time at the same amps draw by having that second battery used together. So don't use them one at a time. (Peukert works for you!)

OTOH if the OP's original battery has been in use for awhile but he still wants the benefit of having two batteries available for dry camping then he should use them separately to avoid the old original from degrading the newly purchased battery. He can easily accomplish this by wiring the batteries with a dual battery disconnect switch such as the Blue Sea m-Series 6007.

True. However you can get away with using two dissimilar batteries together for a few days camping, but then be sure to separate them at home to recharge each to its own True Full.

Once each is full, the safe thing is to also Float them separately. Time2roll says the single float charger will supply enough to each to "float all boats", but other advice warns about eddy currents even so. I don't know how that really works, so I opt for separate floats to be safe.

BFL13 wrote:
Use the diagram shown above. Note that you get more than twice the time at the same amps draw by having that second battery used together. So don't use them one at a time. (Peukert works for you!)

OTOH if the OP's original battery has been in use for awhile but he still wants the benefit of having two batteries available for dry camping then he should use them separately to avoid the old original from degrading the newly purchased battery. He can easily accomplish this by wiring the batteries with a dual battery disconnect switch such as the Blue Sea m-Series 6007.

This is what is balanced and best for twin twelve volt batteries.



As it often doesn't cost a dime more to do this, I think it is worth the trouble.

If you wish to understand the "why" surf here:

correctly interconnecting multiple twelve volt batteries

Others may say it doesn't matter--but unless there is a compelling reason to not optimize charging and discharging why not do it the best possible way?

Use the diagram shown above. Note that you get more than twice the time at the same amps draw by having that second battery used together. So don't use them one at a time. (Peukert works for you!)

Charging them both back at once takes no longer, and even might help if you have one of those WFCOs that has a hard time getting to 14.4 instead of staying at 13.6. (Doing two lowers your charging rate for the same amps perhaps letting it see the 13.2 trigger)