Friday, May 16, 2003 at 21:09
Brett anything is possible and you can, but do not expect it to perform to anywhere near expectations.
1) these batteries are not of identical type (and/or should not be)
2) these batteries are at distance from each other
3) the auxiliary batteries are to be used independently
4) having two auxiliary batteries connected in parallel when one could be flat and the other fully charged and you only drive a short distance then you will end up with two half charged batteries with little capacity. Remembering here there is a large distance by 12 volt standards between the two of the three batteries.
5) loss of charging voltage arises because of the different temperature of batteries and alternator. Consider the difference of the battery in the engine compartment to the one down the back of his vehicle and the one in the camper trailer.
6) the main battery should ideally be a maintenance free and the auxiliary batteries should preferably be standard wet cell type deep cycle. That would allow the regulator to be set at 14.6 for the maintenance free and would be better for the cable loss to the auxiliary batteries only requiring 14.2 thus bringing the auxiliary batteries up to full capacity.
7) never seen the setup of a main battery and two auxiliary batteries at a distance to each other charge to full capacity. At best you would expect to get 75% battery capacity. Work out the resistance between the batteries assuming the correct size cable and you will see my approximation of 75% is on or close to the mark.
8) to get a main and two auxiliary batteries to charge fully you would need to have the auxiliary batteries of both the same type and size next to each other and would need to discharge them together.
Capacity of the alternator is not relevant except to speed of charging.
FollowupID:
12968