How do I conect 3 batteries?

[Guest]

How do I connect 3 batteries in my boat and have them work as well as being charged by the alt.? Please, wiring diagrams very much welcomed! Thanks.

 

[LippCJ7]

Re: How do I conect 3 batteries?

Need a bit more info eric, do you want all three batteries as one unit supplying 12 volts, do you have a battery switch?

 

[2 Eagles]

Re: How do I conect 3 batteries?

Here hope this helps.

 

[Silvertip]

Re: How do I conect 3 batteries?

Here hope this helps.

At this point we have no idea what these batteries are being used for. Let's figure that out first. Besides, if this is an outboard, there is a good chance he cannot keep all three batteries charged due to the lack of alternator capacity. If the three batteries happen to be used to power a 36 volt trolling motor they will be wired in series and cannot be charged from a 12 volt system.

 

[Guest]

Re: How do I conect 3 batteries?

Sorry guys I forgot to add a little more info for you. I have a 2 way switch and want to add the extra battery for safety but also want to keep it charged up with the alt. it will primarily be used as a back up in case of failure of either one or both of the other ones. I don't have a lot of electronics on board just a FF and VHF the radio is crap so I don't use it. I just don't want to get out in Lake Erie with no comunications or engine not starting. As I have identical twin grandsons that want to go fishing with Papa and sure don't want us stranded for any reason what so ever as that might tramatize them for going out again. I love the outdoors and fishing as do my own 2 sons, I want that trend to go on down the line with them! thanks.

Boat is an 87 Doral Tara 24' with cuddy, V6 4bbl Chev OMC, Cobra I/O

 

[LippCJ7]

Re: How do I conect 3 batteries?

ok chose which battery you wish to add the backup battery to, then all you have to do is wire positive to positive and negative to negative, thats called parallel wiring between the batteries on the side you want to add the backup to. Use a fairly sizable wire I prefer 4 gauge and seal the connectors properly with heat shrink that has heat activated glue. when I do this I use batteries of the same age in a bank(two or more batteries wired in parallel is a bank) but others do not its your choice. Your done, now either switch batteries while running to recharge the batteries or run in the both position again your choice.

Probably more info then you wanted but if you were to use a jumper between one batteries positive to the other batteries negative and then your load lines to the other ends of the batteries would be series wiring and be 24 volts but you have no use for 24 volts in your application

Also your charging system is fine for this application but without the added information we have no way of knowing that we are giving you the proper advice for your boat, as Silvertip alluded to

 

[sschefer]

Re: How do I conect 3 batteries?

LippCJ7 gave you the right advice. Please take note his mention of batteries of the same age. I will further that with the fact that they should be identical in manufacturer, size and ratings.

For instance, if you parallel wire your two starting batteries and add a third deep cycle for running accessories with the engine off you can run into problems when you switch to both for charging purposes. To rectify this you can purchase a battery isolator that will correct voltage/current for the different battery types and allow them to charge evenly and correctly.

I destroyed two banks of expensive Group 27 Marine Deep Cycle batteries before I realized what was happening.

The isolators come with concise wiring diagrams and are very easy to install. Done right it can be a vacation saver for sure.

 

[Silvertip]

Re: How do I conect 3 batteries?

Isolators are old-school. ACR's are far more effective devices. There is also no need to have parallel wired batteries from the same manufacturer or for that matter, don't have to be the same capacity. the charging system monitors "system" voltage and cannot distinguish between batteries. It is certainly best to not mix battery technology and it is recommended that the batteries be roughly the same age and capacity but that is not an absolute. Fact is, you can have two identical batteries and they will not have the same identical capacity as indicated on the label. So the weaker of the two will always draw down the stronger until the two equalize.

Don't know what the issue is with have two batteries paralleled on one side of a dual battery switch and one deep cycle on the other. Both are wet cells and will charge properly on the BOTH setting. Charge profiles are nearly the same.

 

[jhebert]

Re: How do I conect 3 batteries?

Here hope this helps.

I found your electrical diagram confusing and completely lacking in detail about the connection and function of the battery switch.