Re: Battery question
I just posted a similar thread (accidentally) on the general forum, but I'll move my question over here since it is similar...<br /><br />I am thinking of a new setup for my two battery system on my 17' whaler w/ 90hp johnson. <br /><br />What I have now is a 1/2/Both/Off switch. As I understand it from all the posts I have read, the propper way to use this switch is to set it to 1 for starting, then to Both while running to charge both batteries, then to 2 while stopped to preserve the charging battery while running accessories. Only draw current on Both if the starting battery is too weak to start and you want to use the house battery for this purpose.<br /><br />Everyone seems to recommend balancing the batteries (using both that have about the same charge characteristics), but this doesn't make sense for mine and many other installations since I have different needs from each. <br /><br />One battery is a starting battery, the other is a gel cell. The boat sits in the water, unused for long periods of time, so the gel cell is to run the bilge pump. Currently, everything is hooked to the output of the switch, so I have to switch between Both for charging while running to 2 for accessories while fishing to 1 for starting and... see the problem? It is too easy to leave the switch in the wrong place, try to start from the depleted gel cell and have a dead battery that puts a big load on the charging system. Or to leave it on the starting battery, run the electronics and not have the juice to start easily.<br /><br />What I am thinking of doing is following the advice in the West Marine catalog -- they suggest using 3 on/off switches, one to connect 1 battery to the accessories, one to connect the other battery to the engine and the third as an emergency bridge to use the house battery for starting. In order to charge both, they recommend using a battery combiner device... something that works like a couple of diodes but without the voltage drop so that both batteries charge when the motor is running but don't drain one into the other if they have imballanced charge. Diodes are much simpler and cheaper, but then neither battery gets properly charged.<br /><br />What do people think of this setup? Does anyone see any problems with this (other than the expense of 3 new switches and a battery combiner)? Suggestions on how to accomplish the same thing for less money? I have seen advice to join them with a solenoid switch and a push-button, but this seems to be a bit more complicated and only saves the danger of leaving them bridged accidentally.