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macduff 07-11-2009 07:43 PM

Light indicator circuit needed when using starter battery

I have a switch on my sailboat which has four positions: Off, 1, Both, 2. 1 refers to battery bank 1, 2 refers to battery bank 2. The batteries are charged via the engine alternator. The main cable attached to the centre of the switch goes to the starter and feeds all the other circuits, i.e. either bank 1 or bank 2 can be used to start the engine and power the circuits. Another main cable goes to the earth of the engine block. Another main cable is attached to the alternator and to bank 1. There is a battery combiner between bank 1 and bank 2, i.e. amps coming from the alternator will go to both batteries or which ever battery needs charging. My usual mode of practice is to use bank 1 for starting the engine, then turn off the engine and start sailing, then switch (going through Both) to Bank 2. Bank 1 is a starting type battery (thin plates). Bank 2 is a deep cycle battery (thick plates). My problem is that sometimes I forget to switch to Bank 2 !! This can run down Bank 1, which I need to preserve for just starting. I wondered if a circuit could be designed that would power a warning light all the time I was using Bank 1 ? I could install this warning light in the cockpit.

scottyt 07-11-2009 10:03 PM

mcduff go read this post it will tell you how to do some simple rewiring to avoid the problems you are having. it looks like you might already have all the parts you need. you will need to relocate the wire from the starter to the common terminal straight to the starting battery, or to terminal one. the better way is to get a new cable to run straight from the starter to the starter battery, then disconnect the old one from both the switch and starter ( this leaves the stock wiring in place incase you want to undo it )

macduff 07-12-2009 01:25 PM

Hmmm ! Good suggestion, but wouldn't this destroy my ability to use bank 2 (deep cycle batteries) as a backup for starting ?
I read somewhere I could use Zircoff's equations ? Thanks for help so far.

scottyt 07-12-2009 11:51 PM

nope you can still use both to start the engine. read the later posts carefully we discussed it

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