36v set up: two 31's and one 34??

[stumpjumper1]

Would it hurt anything to run two group 31 batteries and one group 34 battery on a 36v trolling motor setup?

[CatFan]

It would be pretty close to the equivalent of 3 34s in run time. A 34 is a tiny battery compared to a 31.

[Fishysam]

Not really, but your 31's will be more discharged after fishing that the 34, so they may not last as long as the 34, could get creative and put your anchors on the 34, won't hurt anything since the gas motor has sacrificial anodes and the anchors are bolted to it

[John Jackson]

Yep, a 34 is much smaller and had far less capacity than a 31. you will be out of juice on the 34 with no troller while the 31 have plenty left that can't be used. Your usable amps will be whatever the smallest battery in the series is.

[CatFan]

Not really, but your 31's will be more discharged after fishing that the 34, so they may not last as long as the 34, could get creative and put your anchors on the 34, won't hurt anything since the gas motor has sacrificial anodes and the anchors are bolted to it

?? You have it backwards. A 34 is smaller than a 24 and way smaller than a 31.

[billnorman1]

Anyhow, unless you have a very very unusual size 34, it will probably be the motor battery and probably suffer greatly because it will be the highest loaded. Those two 31's pushing current through it can easily reverse a cell when it gets low.

[moetorola]

This is why we should stop using BCI Group numbers as a reference to capacity.

I understand how people would think a 34 has more capacity than a 31. Because we reference capacity to the BCI group number, here and other places.

The group number has nothing to do with capacity. BCI Group is it physical dimensions.

However....It is true in general the larger the battery the more capacity.
With different chemistries being used more and more in boats and most using the BCI group number, makes it even more unreliable to use as reference to capacity.

It is more relevant to use information such as Reserve Capacity (RC) or Amp Hours (Ah)!


We already reference starting batteries to the CCA or MCA and not group size. Why not use RC and/or Ah for deep cycle!

[Fishysam]

Haha yeah I was tired, 34 is small

[moetorola]

Haha yeah I was tired, 34 is small

I will admit I thought 34 was larger than 31.

[joebone1]

i kind of think the OP meant a 24 and not a 34.

[billnorman1]

Like I said, "Unless you have a very very unusual 34...."