SeaWeasel

I have a standard 2 battery set-up on a single off-1-both-2 switch. One battery is starting and other is "house" (deep cycle). I am going to add another house battery. Can I just wire 'em up and go or should I be concerned about the switch or anything else? Thanks.

BadDog

Not sure where I saw it but consider this. If you are running an amp as the voltage drops the current will increase, same with any load. By hard wiring the two deep cycles together you will keep the voltage up longer and possibly get more use being wired together rather than running one down and then switching to the other. Bass boaters routinely hard wire batteries together for trolling motors. As long as they are of the same type and capacity and general health you should be OK wiring the deep cycles together on #2 and starting battery on #1.

If your alternator allows you to switch while running put the house batteries on #2 and starting on #1 depending upon the style of switch. If the house batteries go dead you want to start on #1 then switch to all to let the house batteries get a little charge then #2 to charge them back up. The reason for the order is there is less of a chance of turning the switch OFF accidentally if #1 is starting. My switch is 1, ALL, 2 rotating CC. If you had it the other way (#1 house, #2 start) you could over rotate the switch in the dead house battery scenario and turn the switch off.

Tim T.

Lmarth

Bad Dog-- I tend to agree with the first part of your post based on the way Hustler wired the batteries in my Slingshot. It has two batteries (starting type) that are wired in series. I think I have the terminology right. If wired in parallel, you'd have 24 volts, right? Anyway, when cranking you have the reserve of both batteries simultaneously. The Shorepower charger charges both simultaneously as do the boat's alternators. The only problem this presents is that if one of the batteries has a weak/dead cell, the good battery will mask the problem. If you put a meter across either battery, you'll get a higher value than if the bad battery was disconnected from the circuit. How do I know this? Cause I just went through this. The starters would pull in, but crank slowly. The switchable volt meter on the boat showed 12+ volts for each battery. When I removed them, the one showed 6 volts and a 50 amp load test showed essentially no voltage. The reason I'm explaining this is to alert others who might start changing starters,etc where one of their batteries was bad. For what it's worth.

BadDog

Lmarth,
Series would give you 24, parallel doubles capacity. You are correct that if you have a bad cell they can run each other down. I keep a battery acid tester in my kit and check them periodically. If I were to have a bad cell I think (hope) I would notice a change in the capacity or run time for amp, fridge etc. In this case I could always go back to my #1 battery to get going again or drop the wing-nuts that connect the two number bank together once I isolated the bad one. The way I have my grounds wired I can isolate any battery in a moment or two. You could always put a second switch in but it would be difficult to explain to you crew how to operate them and it would introduce a bunch of extra connections, wire etc.

Lmarth

Bad Dog-- Thanks for the clarification. The fridge,TV/VCR, 6CD player, etc run off my starting batteries when I'm not using Shorepower. Fortunately, I don't run that stuff when I'm out on the water making lots of noise and burning buckets of 93 Octane. I change the batteries every two years and do try to keep a close eye and ear on them as I do with everything else on my money eater. I crank on the starters to get oil pressure before cracking the throttles to start the motors. When up to temperature these blower motors start at the touch of the key. My simplistic electrical knowledge tells me that if I can crank the motors, get it started and the alternators show I'm charging, then I should be OK out on the water. I appreciate the feedback! Lou

BadDog

Lou, I am running a blower motor also. If you can get the engine to turn over 180 degrees it will light off like a cannon! I usually pull my lanyard and crank for a 5 seconds then drop the lanyard back in. This helps get a little oil flowing around. One time when batteries were almost dead it would not roll over at all. Pulled lanyard and cranked for 1 second, pushed it back in and it started. I have upgraded to a 135 amp alternator. It needs the voltage regulator adjusted though.

BadDog

SeaWeasel, welcome to the board. Any sea's in Kansas? Must be a story behind that name. Anyway, I think you will be OK wiring the two deep cycles together. Find someone who has a clamp on DC ammeter and see what your alternator is putting out when charging those two together.

Sydwayz

iTrader: (1)

My Sonic had two batteries and one switch. 1 Both 2 Off

I don't have the wiring diagram, but you should be able to wire your new battery in with attaching the ground to the motor and the positive to the #2 Post on your battery switch. As long as the switch is set to both, you will be in parallel, and your alternator should charge both. Can anyone confirm my instructions?

SeaWeasel

I think the solution is to wire them up in parallel (which I always get swapped with series- I think parallel is + to + and - to - . . . right?) and leave them as "2" on the switch. The reason for the extra battery is voltage problem running subs. I don't use these for anything else, so I think I will be cool. And, thanks for all the info.

SonicBoom

Another way to recharge multiple batteries with on engine is an isolator. Engine wiring goes to this and then from the isolator your wires to all the batteries. You can still use multiple switches to control what battery you want to draw power from but the isolator decides what needs to be charged.