Batteries!

[chandalen]

Batteries definitely need to be in parallel, voltage stays the same, amperage increases. Series, amperage stays the same, voltage increases. I would imaging if you left all the batteries in parallel, and connected a battery charger to each battery, there would be issues.

My understanding is that the charger need only be powerful enough to charge multiple batteries. ie a a 1.5a charger isn't going to handle 2 batteries, where a 15a should.

I like the car and golf cart references... 1 battery charger is in effect charging several batteries at once.

I think im going to try this, my only problem is i need to bridge the + terminals while charging / maintaining the batteries, and remove the bridge when actually using them, or im rendering the '1 BOTH 2' switch useless. I was really hoping that just putting the batteries to BOTH would charge them both, but it does not. I'll need a wiring diagram to find out why.

 

[doug5790]

I have 3 batteries total. one on the port side, two on the starboard. 1995 290 Sundancer. Which is house? which is port motor, which is starboard motor? My port motor battery is going dead. Out for a cruise, I can watch the port gauge slowly go from 12v to 11v to 10v and then not enough to crank the port motor. Will start with "emergency" jump switch. All three batteries were just replaced. I need to find a loose connection, or wire not connected. Which battery should I look at?

 

[Creekwood]

Just to add fuel to the fire, each battery in in fact a set of six 2 volt batteries wired in series since each cell is in fact a stand alone battery. When you buy a battery, all six cells are close to the same. If a cell goes bad, then the battery is 10v max, and, a non-smart charger will boil out the remaining 5 cells trying to get the thing up to over 12v. Not good and not safe, which is one reason why you should frequently check your battery water levels. A smart charger will not even try to charge a battery that puts out less than 10v (for that reason).

Almost every boat made has batteries wired in parallel (or both parallel and series in the case of 24v systems). So its not "wrong" to do so, its actually necessary. But.... you do want to have each battery in a bank of batteries, to be of the same type, brand, and same age. They need to be as close as possible to each other so they discharge and charge at as close to the same rate as each other. This will minimize the issues with one battery draining or causing overcharging of others in the same bank.

As for the battery switch question and whether you should leave them on 1, 2, or both, its a bit complex.

If you have an isolator between the banks (which you should get if you don't have one already), I would say just leave it on both since the isolator takes care of balancing the charge between the two and wont let one bank draw down the other on discharge. If you have a stock multi-bank charger and multi-bank set up, you probably have an isolator.

If you don't have an isolator, then you should not leave the switch on both while the charger. Generally you can turn the switch off if you are leaving the boat since the charger (and the bilge pumps) should be wired on the battery side of the switch (meaning they re always connected regardless of switch position).

 

[AMFM3]

I have 3 batteries total. one on the port side, two on the starboard. 1995 290 Sundancer. Which is house? which is port motor, which is starboard motor? My port motor battery is going dead. Out for a cruise, I can watch the port gauge slowly go from 12v to 11v to 10v and then not enough to crank the port motor. Will start with "emergency" jump switch. All three batteries were just replaced. I need to find a loose connection, or wire not connected. Which battery should I look at?

In my 95 370, Port is the starting battery and starboard is house. I turn Port on when I'm leaving the dock and while cruising.

Mark