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Starting Dual purpose batteries

neversummer

Regular Contributor
"I know this issue has been di

"I know this issue has been discussed already but I am still unclear about the best type of batteries for my 1989 Maxum 2300 with 5.0 sterndrive. I have always used two batteries with a perko selector switch but need to replace them for this coming season. Should I go with two new "cranking" batteries or do I need the "dual purpose" batteries that West Marine sells? I do not require heavy electrical loads when the engine is off, I only use VHF, GPS, and occasionally the CD player (no baitwell, trolling motor". I plan to connect these batteries in parallel to increase amperage. Thanks"
 
"If you connect them in series

"If you connect them in series you will increase your collection of burned out electronics.

It depends on your application. I really see no reason not to use automotive batteries if they fit, have the same or better cranking capacity and the terminals are compatible. On the other hand, automotive batteries are much less forgiving of deep cycling. If you use the battery for cranking only and are able to maintain its charge when the boat is stored you may be able to save some money. Also (high quality)automotive batteries ususally have a much better warranty. You have to weigh these factors against the possibility of a dead battery in the middle of the lake or not being able to hold a charge because you cycled it too much. You could also use one battery for starting and a deep cycle for running auxiliary equipment with the engine off."
 
"Capt Ted, Sounds like Crankin

"Capt Ted, Sounds like Cranking will work for you I would continue to use the perko switch, clean and protect your connections. Cranking/Deep Cycle batteries will take longer to recharge, upto double the time. I'd stick with the marine batteries perosnally."
 
"My preferred setup for a sing

"My preferred setup for a single engined boat is to use a main battery that is a marine start cycle battery and a secondary one that is start/deep cycle. Connect all the electronics to the start/deep cycle battery...including your bilge pump.

Use an A/B/Both/Off switch as follows:
Start/run on A most of the time
Start/run on B to recharge the start/deep cycle battery every other trip or so.

If you have trouble starting the boat on the B start/deep cycle battery doing this, then buy a simple diode type charge splitter... and still start and run on the B battery every once in a while since the simple charge splitters won't charge the B battery 100%

If you want a more elegant (and expensive) solution that will keep the B battery up to 100%, there are intellegent charge splitters that will keep both batteries 100%.

Now...as to the "Both" position. This should only be used in an emergency to start the boat if neither the A nor the B battery will start the engine. NEVER run for prolonged periods of time on BOTH. Its a good way to shorten battery life. You could get away with using BOTH IF...
1) Two identical batteries with the same date code were fully charged and then installed on the boat on the same day.
2) You only ever used OFF or BOTH settings on the switch."
 
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