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post #2 of Old 07-10-2008
Once known as Hartley18
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Originally Posted by MrSeaDragon View Post
Hi, I'm a bit of a novice and have been trying to get my head around what I should do for a new battery setup on my Compass 29 (yes I'm in Australia !).
Compass 29.. a nice boat. Welcome to Sailnet, Greg.

Originally Posted by MrSeaDragon View Post
Hypothetical: I have a 1 smallish starting battery and 1 largish house battery bank. I'm out for the weekend and have run my house bank down very low over night powering the ESKY My starting battery is all but fully charged as its only started the engine once on the way out. I start the engine in the morning and the alternator kicks in.

Questions : Regardless of how my batteries are combined the alternator will at some point be charging 1 almost full battery and 1 almost empty battery bank, so what charge level (voltage?) does it use to determine its output ?

Taking this to the nth degree, would it be possible/better to have a regulator/controler for each battery bank, rather than for each charging source ?
To answer your question directly: it depends how you have the charging set up. The simplest setup usually has a couple of diodes connected - one to each battery - allowing current to flow to each with the most discharged getting the benefit, as Jody pointed out. The problem with this sort of setup is that there is not really anything stopping the full battery being overcharged.

A better setup would be to have a regulator/controller for each bank. This allows the regulator to either trickle-charge or float-charge each battery independently. Have a look at the Blue Seas web site for ideas.

Hope this helps.

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