Charging 2 aux battery’s

[russ1]

Hi guys.
Hoping for some advice, at present I have a voltage sensitive relay as a split charge set up charging an 100ah aux battery, now I am looking at adding a second aux battery again another 100ah.
Can I just tie the two aux battery’s together and use the one split charge relay or would I be better adding a second split charge system.
Also looking at adding a solar setup to aid charging when parked up for extended periods of time.
Thanks in advance.

 

[john61ct]

A single house bank plus a starter batt is best for simplicity.

But ideally all the batts in a bank are the same, including mfg date.

If the older one is in excellent shape, residual capacity say 95%, then likely only a minor hit on overall longevity

 

[john61ct]

The latter means lower total capacity, greater voltage drop and shorter lifespans.

 

[CaliMobber]

Hi guys.
Hoping for some advice, at present I have a voltage sensitive relay as a split charge set up charging an 100ah aux battery, now I am looking at adding a second aux battery again another 100ah.
Can I just tie the two aux battery’s together and use the one split charge relay or would I be better adding a second split charge system.
Also looking at adding a solar setup to aid charging when parked up for extended periods of time.
Thanks in advance.

Yes you can, as stated above the only issue you will have is the used battery with drain the new battery down to the old battery state(when the cars off and the batteries settle). I added a new optimum battery ( same size) to my system a year or two later with now issues. Lasted 7 more years.

 

[Steve_P]

If the batteries are going to share loads I would wire them parallel and use a single relay. If they are to be used for separate loads you will need to charge them separately. I have an aux battery in my truck, and when I plug in my camper you could say I'm charging 2 separate aux battery banks.

The camper battery gets more charge from the solar panel on the roof than from the truck but the truck provides enough boost for cloudy days.

 

[john61ct]

If they are to be used for separate loads you will need to charge them separately.

Not true. You just need a VSR (combiner, whatever) designed to be robust enough to handle the (minor) initial current inrush across the device when a full batt is paralleled with an empty one.

Those designed for self-jumping the starter from House when needed are bulletproof.

Or use a DCDC charger between them, if the distance would otherwise require an impractically high gauge wire between the two banks.