12V Batteries Combined in SERIES - Different Size/Capacity OK?

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SoCalAngler
Posts: 26
Joined: Sat Mar 30, 2013 6:58 pm

12V Batteries Combined in SERIES - Different Size/Capacity OK?

Postby SoCalAngler » Thu Aug 23, 2018 12:41 pm

Found a great deal on 2 Optima Blue top batteries from a private seller. Great price....new, never used, two months old.

The sizes are D31M and a D27M

Combining them in SERIES for 24volts.....

Does this pose any problem running my Motorguide 24V trolling motor, in terms of amps, capacity, etc?
How about with my ProMariner 20PLUS battery charger....issues with charging?

Batteries:

https://www.optimabatteries.com/en-us/b ... d-starting

Thanks!

Kanbass
Posts: 5
Joined: Tue Oct 30, 2018 4:55 am

Re: 12V Batteries Combined in SERIES - Different Size/Capacity OK?

Postby Kanbass » Fri Dec 21, 2018 9:04 am

I do not understand, do you advertise batteries or ask for advice? :mrgreen:

Kinzun
Posts: 2
Joined: Thu Dec 06, 2018 8:58 am

Re: 12V Batteries Combined in SERIES - Different Size/Capacity OK?

Postby Kinzun » Fri Dec 21, 2018 9:09 am

Kanbass wrote:I do not understand, do you advertise batteries or ask for advice? :mrgreen:

Did you see the date? I think the question is irrelevant. But still;)

User avatar
JoeLanghans
Posts: 301
Joined: Wed Aug 03, 2016 8:47 pm

Re: 12V Batteries Combined in SERIES - Different Size/Capacity OK?

Postby JoeLanghans » Fri Dec 21, 2018 10:19 am

I don’t think you’ll have any issues since they’re both 12 volt. The size 31 battery will take longer to charge, but it’s charge will last a tag bit longer.

Bassfishman
Posts: 92
Joined: Sat Jan 23, 2016 9:50 am

Re: 12V Batteries Combined in SERIES - Different Size/Capacity OK?

Postby Bassfishman » Thu Dec 27, 2018 10:19 am

Combining multiple batteries that are different sizes in series is a very bad idea. Could even be dangerous. The problem will be when you are using the batteries on your trolling motor. The smaller battery will completely discharge before the bigger battery does and could go into reverse voltage. That's the concern. Same size batteries discharge equally as their voltages go down uniformly. I would not recommend it. Its bad enough having same size batteries that are different age in series (but I will admit, I do that on my boat). Ideally you have multiple series batteries that are the same size, same manufacturer, and the same age. But I realize that can be expensive.

birdman920
Posts: 326
Joined: Sat Nov 28, 2015 4:23 pm

Re: 12V Batteries Combined in SERIES - Different Size/Capacity OK?

Postby birdman920 » Wed Jan 02, 2019 2:18 pm

Very bad idea ‘ to mix batteries!.... my buddy fried his new Ultrex doing that !....

WRB
Posts: 623
Joined: Tue Dec 29, 2015 8:47 pm
Location: Simi Valley

Re: 12V Batteries Combined in SERIES - Different Size/Capacity OK?

Postby WRB » Wed Jan 02, 2019 5:09 pm

All batteries in series should be the same size, age and voltage, otherwise the weakest link is the weakest battery and the all the batteries are drawn down dropping the voltage.
Tom


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