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Li-Poly for a trolling motor?

Aphers

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Joined
Nov 17, 2020
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I use a 12v trolling motor on a dinghy and would like to replace the heavy SLA with something a bit more portable. I don't need a huge capacity, I just want to be able to easily take it home to charge. The motor draws around 53A at full power and I really only need about 20mins endurance, so 20A usable capacity should be plenty.
I've investigated LFP and using conventional (1C) cells I'd need a fairly big and expensive pack. Seems a bit overkill for what I need.
LiPoly however offers crazy high discharge rates, so I could get by with a tiny pack.
My worries are:
- the voltage of a 4x pack is quite a bit higher than the SLA that the motor is designed to use;
- I guess I will still need a BMS?
- the fire risk of LiPoly is much higher than LFP, I think?

Would be interested to hear any thoughts on this, especially if anybody has actually tried it.
 
I have a 12v trolling motor on my kayak that I use Valance LiFePO4 (used medical system) batts and DIY built Li-Ion batts. I would not run LiPo on a trolling motor. That chemistry is to volatile, especially without very close monitoring

4s LiFePO4 voltage is much closer to 12v SLA than either LiPo or LiIon. But increased voltage has not caused me any issues. I don't think the motor of the trolling motor, would ever be an issue. Although I currently run a remote controlled ESC, and have run after market PWMs to replace the factory controls

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@Mike Jordan Do you have a thread with the details of your setup? Working through something fully custom for my inflatable kayak. I would be curious on your range vs watt-hour observations.

To the OP, 53A is 2.5C for a 20AH bank. You may find the motor spins a fair bit faster with lithium compared to lead. So your current needs may be less for the same thrust.

Have you looked at these fortune cells? They are rated at 3C and 25AH. 30% each plus shipping seems reasonable. They are also a lot more stable than LiPo. A 4S pack should work great with a 12V nominal system. At 1.5lbs each, that would be 7-9lbs depending on how you packaged them.

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As far as BMS goes, for LFP the JBD/overkill style BMS would work fine for modest cost. There are versions around 50-100A capacity.
 
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@Luthj I have used my Valence battery system on my inflatable :cool: Same motor as above. But at the time of these pics I just had an ebay pwm controller. The remote controlled ESC set up in the above pic sure is better. :) My 24lb thrust Watersnake motor only draws 16.5 amps at WOT. I get 4.5 mph on my hard shell kayak and 3.5mph on my inflatable with both my wife and I. The sweet spot for speed/draw on my hard shell is 13.5 amps at 4 mph

I have 4 100ah prizmatic cells on order. They are not planed for the kayak, but I am sure I will have to try them anyway :cool:

I do not have any build posts here. I have several YT videos of various aspects my set up. You can check out the channel here

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