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

[SoCalAngler]

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]

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

[Kinzun]

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

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

[JoeLanghans]

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]

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]

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

[WRB]

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