OK, here's my first question: My boat has two batteries (that seem to have at least one dead cell apiece). The batteries are connected in parallel to a large On/Off power switch. This boat has a Mercruiser 4-cylinder (actually based on 1/2 of a Ford 6 liter). Is it common for an engine of this size to need the level of cranking amps provided by two batteries in parallel? I've been told that boats capable of going offshore normally have two starting batteries but they are not connected in parallel. Any ideas? :?:
Batteries
- Thread starter mainexile
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plymouthgrady
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My 1st suggestion is to get new batteries. A strong battery won't bring a weak one up, a weak one will draw a strong one down
Rule of thumb for batteries- you need 1 mca for every CID.
Most batteries have ample cranking amps.
Don't start the engine w/ batt. selector on 'both". They will draw off of each other.
The main reason the boat has 2 batteries is because of the amount of electronics and the chance that one batt. could die (among other reasons- house batt, etc).
Others will disagree but my experience and my advice is the heavier, the better. Starting batteries will give you plenty of mca's but you'll piss right through the RC. I recommend matching dual purpose-plenty of mca's, reserve capacity and designed for multiple charge/discharge cycles.
Rule of thumb for batteries- you need 1 mca for every CID.
Most batteries have ample cranking amps.
Don't start the engine w/ batt. selector on 'both". They will draw off of each other.
The main reason the boat has 2 batteries is because of the amount of electronics and the chance that one batt. could die (among other reasons- house batt, etc).
Others will disagree but my experience and my advice is the heavier, the better. Starting batteries will give you plenty of mca's but you'll piss right through the RC. I recommend matching dual purpose-plenty of mca's, reserve capacity and designed for multiple charge/discharge cycles.
PlymouthGrady:
Thanks for the reply, but I don't think I made my question clear enough. I don't have the option of selecting one or the other of the batteries; they are connected together in parallel which adds together the amperage. The switch is simply an on/off for the two battery configuration.
Thanks for the reply, but I don't think I made my question clear enough. I don't have the option of selecting one or the other of the batteries; they are connected together in parallel which adds together the amperage. The switch is simply an on/off for the two battery configuration.
I would buy two new batteries and a switch that says off, 1, 2, both. Not advisable to use both unless you know they are good and you need to charge them both. Use 1 or 2 when motoring or trolling, especially when you have electrical loads on.
On the larger boat I have four 8 d's. Two for starting the diesels, two for house loads. I have a combiner/ isolater that keeps the batteries charged but seperates the loads. I also have a guage on the dash that tells me how far the house batteries are discharged so I know when to remove the loads or start the gen set. This is a great set up but overkill for a smaller boat.
On the larger boat I have four 8 d's. Two for starting the diesels, two for house loads. I have a combiner/ isolater that keeps the batteries charged but seperates the loads. I also have a guage on the dash that tells me how far the house batteries are discharged so I know when to remove the loads or start the gen set. This is a great set up but overkill for a smaller boat.
Thanks for the advice guys. I'll definitely separate the batteries with a one/other/both switch, and I'm looking at replacing these lead acid slugs with a couple of Optima blue-top dual purpose. Any opinions on the optimas would be greatly appreciated.
I had the Optimas on my previous Boston Whaler Outrage w/ 200 HP Optimax and they gave me great service. As far as I know the curretn owner is still using them. Also consider Odyssey AGM as well. They are more conventionally sized in their dimensions than Optima. The AGMs are great because there is nothing to spill and you can mount them anyway you like.
jehines3,
If my charger needs a special profile for AGM batteries, will they recharge properly from my alternator?
If my charger needs a special profile for AGM batteries, will they recharge properly from my alternator?
AGMS are much less worrisome than Gel. For a gel you should upgrade to include a special regulator.