Looking for battery build advice

[John Kinslow]

Background, have 24 volt trolling motor which is powered by two group 29 lead acid batteries. Due to location I have to store the boat, I have to remove the batteries and charge them at home each time I use the boat. These batteries are getting too darn heavy for this old man. I am currently wait delivery of 8 ea 240Ah 3.2V Grade A cells from Tewaycell via Aliexpress. My question: Regarding finished battery weight, I would like to have this battery unit in 2 pcs. Would it be best to build 2ea 12V batteries w/ a 4s 12v BMS for each or can I use an 8s 24v BMS with disconnect plug for the 4 cell monitor wires on the assembly w/o BMS? Batteries will be within inches of each other. Thanks

 

[sunshine_eggo]

IIRC, those cells will weigh about 70# alone.

I have never heard of that supplier. No meaningful search results on that name on this site.

I would scrutinize the crap out of them and plan to do a full top balance and the whole shebang.

I would build as your second scenario. Helped a friend do exactly this. Didn't bother with a disconnect plug, just had connectors for each of the other four leads labeled for convenience and a hearty 2/0 stubby cable joining them.

 

[time2roll]

No sun or power in storage to charge at 24 volts?

Pair of 12 volt batteries might be fine.... consider charging them in parallel with a 12 volt charger to keep in balance.

 

[John Kinslow]

Thanks for the info and additional threads. Lots of info here.
Weight, current group 29 lead/acid batteries about 60# each and tough for an old man to lift up out of boat. Figured the LifeP04 would save my back for a while being about 20# lighter each.

No power where boat is stored and hopefully we'll have some cloudy days here in the Sacramento area when we get some rain. I do fish in the winter some and need batteries ready to go when needed.

 

[HRTKD]

@time2roll 's point was that if you have sunshine available where you store the boat, then you could mount a couple of solar panels to the tongue or the boat to keep the 24v battery charged up. Then there is no need to remove it at all.

 

[sunshine_eggo]

Two 100W panels should be able to top them off from empty in about 9 days.

One other question...

How many amps does the trolling motor pull?

 

[John Kinslow]

54 amp wide open; but hardly used wide open. I have never check amp use at the usual speeds I troll at. Figured with the 240amp system I would be good for a 2 day trip. At times I'm able to go fishing once a week.

 

[sunshine_eggo]

54 amp wide open; but hardly used wide open. I have never check amp use at the usual speeds I troll at. Figured with the 240amp system I would be good for a 2 day trip. At times I'm able to go fishing once a week.

Going overkill BMS? 100A should be good.

If there's ANY way of deploying solar, even a 100W panel would likely restore about 10-15% of your capacity with good sun on your 2 day fishing trip... like refueling on the water.