Two Battery Set-ups in Parallel

[smashdn]

I run two batteries on my boat hooked up in parallel. For those of you that are also doing that are you using two multipurpose batteries or a combination of deep cycle and starting?

I have my big motor connected to one battery by itself (but that battery is connected to the other). And then have all my other stuff (TM, electronics, bilge, etc.) on the other (but connected).

In this manner does it matter whether one battery is starting or deep cycle or not? Whatever set-up I am using is working but am contemplating getting fresh new batteries and getting some battery boxes to tidy everything up back there.

I noticed in wal marks the other day that you can get 2 ga battery cables for 11 bucks. Right now I am using some lighter gauge wire for connecting the two batteries. I think I will upgrade there as well.

[CatFan]

You want them to be the same type and size of battery if you connect in parallel.

[SeaRay]

If your 2 batteries are tied together then every thing you connect to either one is in effect connected to both, unless you have some type of diode in line to prevent current flow in one direction.
When you hook 2 batteries in parallel you basically have one BIG 12 volt battery and it does not matter where you connect things to it.
Both batteries need to be as close as possible in type, size, and age. If they aren't you get uneven discharge over the two batteries.
I ran 2 deep cycle batteries in parallel on my motor home so I got to learn all kind of stuff, some the hard way.

[Cray]

Help us out here just a bit, besides cranking what all do you have hooked to this setup? If just a couple of finders, bilge, lights, livewell pump, areator just normal stuff. I see no need for 2 batteries. Just one good deep cycle group 27 would work just fine. And if you were worried at all a group 29.

["G"]

Well....the battery your TM is on should be a deep cycle because of deep discharging and recharging....deep cycles are made for this. Regular batteries are not made to withstand deep discharges and therefor would have a short life. I recommend you put your big motor on a a battery of its own and connect your bilge pump....live well and electronics to it. and Get a deep cycle battery for your TM only....if you want more run time on TM then get a group 31 deep cycle for it and run nothing but the trolling motor with it.

[doggone]

I am thinking you want the two batteries matched for capacity and construction. Sort of like having matched horses on a yoke. So the power is as evenly distributed as possible. If you go ahead and get the dual purpose type then supposedly the quick amp draw of the starter and long duration draw of the other stuff will be okay. I would watch the amp hour and reserve rating and try to get the highest I could. Two 27 class would be better than two 24 and so on and so forth. But the weight difference and price has to be considered. I would think two 27 class dual purpose with high ratings would do it for the average guy. A short wire will carry more than a long wire. I think anything over a 6 gauge on a crossover wire of a few inches may be a little overkill.

Your gonna want to charge that with a 12 to 15 amp charger at least I think.

[smashdn]

Help us out here just a bit, besides cranking what all do you have hooked to this setup? If just a couple of finders, bilge, lights, livewell pump, areator just normal stuff. I see no need for 2 batteries. Just one good deep cycle group 27 would work just fine. And if you were worried at all a group 29.

Cranking
Trolling Motor
Unit at Console
Unit on front deck
Running lights
Bilge pump
Aerator pump to nowhere (no live well but I can fill my boat with water if I want)
Spot light for running the river in the winter

Boat always had tow batteries in it. One for cranking and one for other stuff. I guess the last time I had to buy a battery I bought two multipurpose batteries and tied them together.

It is probably 70% a duck hunting boat so I suppose I felt like I needed all the juice I could muster to turn the motor over when it is really cold out.


I had a little folding cash in my pocket so I thought it might be a good time to re-do the bilge area and clean it up with battery boxes and while I was at it get some fresh batteries and clean up some of the wiring. It is bird's nest at the moment. The engineer in me hates it.

[Cray]

Do yourself a great big favor. Put 2 batteries in. One for trolling and accessories and one just for cranking and electronics. The reason for putting electronics on cranking is sometimes you get interference when hooked to trolling battery. That way if you did have a cranking problem you could always jump to trolling battery. Several ways to accomplish that. Could just move motor cables or rig a jumper of heavy cable between batteries. I do not like jumper cables in boat around gas tank for safety reasons. Just me I guess but fire in boat is scary.

[fishervet]

Well....the battery your TM is on should be a deep cycle because of deep discharging and recharging....deep cycles are made for this. Regular batteries are not made to withstand deep discharges and therefor would have a short life. I recommend you put your big motor on a a battery of its own and connect your bilge pump....live well and electronics to it. and Get a deep cycle battery for your TM only....if you want more run time on TM then get a group 31 deep cycle for it and run nothing but the trolling motor with it.

how many hours will the group 31 run...on almost full speed?

["G"]

Depends on boat hull size and total boat weight with persons and gear etc......also depends on what trolling motor you have on mine full speed is about 3 mph....Two group 31 in series for 24 volts will run my 80 lb. Terrova 8 hrs. with power left at a continious 1.7-1.8 mph. This is with just a slight wind......If your trolling head on into much wind it will make a difference in your run time also.