Trailer battery charging while towing

ekirkland wrote:
Would 2-3 hrs. fully recharge?

Not even close. you'd be lucky to return 30AH to them in 3 hours of driving over the stock 7 pin charge path.

With high amperage applied, one can quickly return a battery to 80% charged, but that last 20% is going to take about 4 hours, and that is IF absorption voltage in the mid 14 range, is held for those 4 hours.

Your distant house batteries will never get to absorption voltage unless you drive for 24 hours. the voltage drop would never allow it until the batteries could not accept more than 2 or 3 amps.

Some solutions to faster recharging are an inverter hardwired to engine battery, feeding an household AC extension cord to a higher amp charger on the trailer.

One could beef up the original circuit, or better yet add A much thicker copper circuit between alternator and trailer battery through a Burly connector.

I achieved 100+ amps into a distant healthy group31 AGM battery over~30 feet total circuit length of 2awg and a '500 amp' winch connector.

Here is a 6awg kit ready to go which will drastically improve charging amps into depleted trailer batteries compared to just the 7 pin connector:

http://www.amazon.com/Keeper-KTA14128-Trailer-Harness-Connect/dp/B008N8IMI8/ref=pd_sim_263_1?ie=UTF8&refRID=147ND97WNXYBJX94R5M6


Thicker copper will allow one to get upto 80% much quicker, but that last 20% to a true 100% charge, is going to take hours, about 4, when the batteries are still healthy. If older and partially sulfated, expect absorption times to increase well beyond 4 hours until specific gravity maxes out at which point the flooded battery can be considered fully charged.

But they are just batteries and rented so perhaps 92% will give you an adequate rental contract.
I seek 100% asap, aoap, and this takes time at absorption voltage with no way to bypass the time required.