Can 3 batteries be charged with one alternator

[sebas54]

Hi, I have a 75 or 85 amp alternator and 2 starting batteries.

I would like to install a thrid deep cycle battery for all my excesories.

Can I hook up three batteries on a single alternator?

Will they get enough charge?

Thank you

 

[Silvertip]

Re: Can 3 batteries be charged with one alternator

Can you charge three batteries from a single alternator -- YES
Will it get enough charge? -- We don't know. They will get charged, but how much depends on how long you run, how fast you run, and how deeply discharged the batteries are. Keep in mind the voltage regulator monitors the "average" of the entire system so unless all three batteries are identical, one or two of them may never be fully charged and one or two of them may be over-charged.

 

[Boatist]

Re: Can 3 batteries be charged with one alternator

You can charge many batteries with a 75 amp alternator. All the alternator does is produce a DC Voltage in the in the 13.8 to 15 volt range. Then with that voltage each battery will charge up. As the battery charges it will reduce the amount of current it takes. Now maintenance free batteries can be charged at a slightly higher voltage because it is sealed and the water will not boil away.

Lots of ways to charge, I like a battery isolator and with 3 batteries you can use a 3 battery isolator. This work best if your alternator has an external Voltage regulator.

 

[sebas54]

Re: Can 3 batteries be charged with one alternator

Thanks for all the replies.

I have 2 starting batteries(identical) that I want to use and hook up in parallel and one deep cycle battery that I want to hook up to all my accessories.

I have a battery switch that I will hook up both starting batteries to #1 and the deep cycle to #2. Is this a good way of doing it.

I have been running my accessories on one of the starting batteries and it loses power too quickly.

 

[PondTunes]

Re: Can 3 batteries be charged with one alternator

You could use the starting batteries in parallel but I would say that is a bit overkill. Your starting battery is designed for high current draw and doesn't like to be deeply discharged over and over. You would probably be just as happy replacing the second starting battery with the biggest deep cycle you can fit/afford. Run your high draw electronics such as a stereo system or trolling motor and keep your starter and other critical systems attached to battery #1. If you have to have two starting batteries to crank your engine something is wrong!

If you still wish to have two starting batteries wired in parallel just hook it up pos - pos, neg - neg and wire as if it were one large battery.

Note: There are a couple of ways to accomplish what you're trying to do so if isolators aren't your thing because of the voltage drop you could always pick up an automatic charging relay that auto senses voltage and would charge the deep cycle whenever a charge from the alternator is present.

 

[Boatist]

Re: Can 3 batteries be charged with one alternator

I am not a fan of batteries in Parallel. To me it just means you will be buying 3 times as many batteries.

First batteries wired in Parallel will only be as good as the weaakest battery.
Batteries need to be the same type and age and even then one battery will be a little better than the other.
The weaker battery will draw current from the stronger battery and that will weaken the stronger battery.

I would use one starting and one deep cycle or isolate all three batteries and hook up specific thing to each battery.