diy solar

diy solar

36v trolling motor battery

hello everyone, I'm new here and placed an order for Ultrex 112 thrust 36 volt system for my 18 foot lund. i have a Valence U27-12xp battery for my two humminbirds and garmin livescope (overkill on amp hours.) with the victron energy IP67 blue smart 12v/17ah battery charger. I was planning to order 2 more of the U27-12xp but then i wasn't sure if i need a charger for each battery or i can hook up one 12v17ah charger to all three at once. Now I'm thinking of building one 36 volt battery for my new trolling motor with like 70-80 amps to go two days if fishing with out charging. Pretty sure i need a new 36 volt battery charger. would I be able to use the U27-12xp has a starting and main battery? The U27-12xp is 12v, 144Ah, group 27,max cont. current is 150 A, charge voltage 12.6, energy is 1843.
 
First of all, hi! Great forum.

I want to build a 36v battery pack for a trolling motor. The motor specs listed say the max draw is 53 amps.i will seldom run the motor at full speed, but I will run it all day some days.

I have been using FLA group 27 batteries connected in parallel, but they will only last a couple of years, and I'm looking for something that will last a bit longer. What amp hour rating should I shoot for and what chemistry would work best? I do fish in freezing temperatures from time to time so that is a concern. I have looked at some off the shelf batteries, but I'm not sure how they would react to running in parallel and how to charge them. Plus I'm not made of money.

I am considering this build because I hope to parlay this into a "powerwall" system for my home some day soon.

That is for the help!
have you started on this. I just ordered a new Ultrex 112 from minn-kota and want to make a 36v battery for my boat.
 
Hey Pilothawk,

Where you from?

Keep it simple man! I'm doing the exact same thing as you, DIY stringing together lithium battery packs to run a 36v Minn Kota trolling motor on my bass boat. I suggest you keep it real simple and stay with LifePO4 tech, and build 12v batteries with 4 large square prismatic cells. They're simple to manage, connect and fix. The easy 54a low draw of that trolling motor is no problem. I'm planning on making 3 12v batteries to replace the group 27 FLA batteries and connecting them in SERIES, Lol. Easier to buy a 3 or 4 bank Lithium charger that way too and you can charge or jump start your dead crank battery for a sec from one of those 12v t/m batteries.

You can buy 4 new or used 3.2v LifePO4 cells and put them in series, get the 100a smart BMS Will recommended with bluetooth smartphone app for quick monitoring and do WAY better than FLA for hardly any more $$ and get 4x the life!

A 12v group 27 FLA battery may have a capacity of, say 80Ah, BUT, with FLA tech if you pull it down below 50%, voltage drops so low your t/m will barely run, AND it kills them real quick, as you've been doing. If 3 group 27's have been fine for you, then three 12v 50Ah LifePO4 packs will be fine because unlike FLA, you can use 100% of it's storage. Guys on bbcboard bass boat forums are doing exactly that, repl group 27 FLA's with 50Ah Lifepo's and getting BETTER runtime. That being said, it's best to NOT kill your lithium batteries every day either if you want them to last 10 years; work with an operating range from 80% to 40% and they could outlive you.

I'm overshooting and making 3 12v 75Ah batteries for the 36v trolling motor, but I may also switch to a 24v Garmin Force because its brushless motor is both more powerful and way more efficient than the Minn Kota armature. The same Garmin can be set to run at 24v or 36v, and 75Ah should be fine for long days fishing and which ever voltage I run. If you build 100Ah lifepo batteries, you'll be able to fish a couple big days no prob without charging, from what guys say.

As you probably already know, LifePO4 can last you over 10 years if you're careful. Don't treat them like FLA. Don't store them at 100%, store them at 50% AND disconnect them so they don't get accidentally drawn below 2.5v per cell. Do not overcharge. Do not draw them down below 2.5v per cell. Do not charge below freezing.

I'm doing it! I'm ordering cells from China here real soon. Trying to find good cases. I'm doing my engine starting battery too, but even bigger, 150Ah for headroom and fish finders. Lets do this!
Hello. Sir. I’m reading along these post when i break away from family time. What kind of BMS or where can I get them? I’m looking to build an 80-100ah for my new 112 ultrex that I’m picking up in a few days. I believe I need about 12 of those 3.2 lithium cells. Then another question is do I build three 12v batteries or one 36v battery. I’m struggling to find aassortment of 36v lithium charger to choose from.
 
Hello. Sir. I’m reading along these post when i break away from family time. What kind of BMS or where can I get them? I’m looking to build an 80-100ah for my new 112 ultrex that I’m picking up in a few days. I believe I need about 12 of those 3.2 lithium cells. Then another question is do I build three 12v batteries or one 36v battery. I’m struggling to find aassortment of 36v lithium charger to choose from.
I'm assembling a 36v 100AH pack for my Minn Kota 112 now with 240 of these https://batteryhookup.com/products/3-7v-4-4ah-16-28wh-w-bms-no-wires. Here's a link to the thread I started about wiring https://diysolarforum.com/threads/need-help-wiring-pack-please.11249/post-123691
It will measure 9"x9"x9" and weigh 50 lbs. That's some high density energy.
Be sure to pick up a Kipawa 112 propeller when they're back in stock for greater efficiency.
 
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Omg. No way I’m gonna work with 240 of those hard drive size like batteries. That’s insane amount of work. I’ll freak out tapping the wrong wire ka-boom
 
Omg. No way I’m gonna work with 240 of those hard drive size like batteries. That’s insane amount of work. I’ll freak out tapping the wrong wire ka-boom
Discharge them all to 2.8v and the bms turns them off for 0 volts. A 9 inch cube that weighs 50 lbs and delivers 36v 100ah is the ultimate boat battery... for $300 anyway. I retired two years ago so I have to do something with my time.
 
I’m 46 and retired too from the work force but I manage my rental properties for now. So how is that battery working out now? Hmmm. Wonder if I can pay you to build me one?
 
I’m 46 and retired too from the work force but I manage my rental properties for now. So how is that battery working out now? Hmmm. Wonder if I can pay you to build me one?
I haven't wired the battery yet and I really don't want to take on any more responsibility. I had a high stress job that totally burned me out so I try to keep my stress level to a minimum.
 
hello everyone. quick question here. in order to make a 12 volt battery for my trolling motor all i need to do is get the four cells from https://www.alibaba.com/product-detail/3-2V-120Ah-Li-ion-Lithium_62525289710.html
3.2V 120Ah Li-ion Lithium Rechargeable Battery LiFePO4 Cell for Electric Car solar system
then a BMS for each 12 volt battery. then a lithium battery charger for that battery.

since i am having a on board battery charger i don't need to get a solar charge controller and don't need a low temperature disconnect for the battery.

please advise if info above is correct. reason i'm asking is Will Prowse is mostly talking about solar charging.
 
hello everyone. quick question here. in order to make a 12 volt battery for my trolling motor all i need to do is get the four cells from https://www.alibaba.com/product-detail/3-2V-120Ah-Li-ion-Lithium_62525289710.html
3.2V 120Ah Li-ion Lithium Rechargeable Battery LiFePO4 Cell for Electric Car solar system
then a BMS for each 12 volt battery. then a lithium battery charger for that battery.

since i am having a on board battery charger i don't need to get a solar charge controller and don't need a low temperature disconnect for the battery.

please advise if info above is correct. reason i'm asking is Will Prowse is mostly talking about solar charging.
Does you onboard charger have a lithium setting? Most don't that I know of. Yes you want low temp dissconect.
 
the on board charger i currently have has an AGM setting that charges up to 14.4 volts. what does the low temp disconnect do? does it disconnect/turn off when the temperatures get to freezing point. I wouldn't be charging my batteries in the winter months. i would pull them out of my boat, warm them up for at least 24 hours in my house before charging.
 
the on board charger i currently have has an AGM setting that charges up to 14.4 volts. what does the low temp disconnect do? does it disconnect/turn off when the temperatures get to freezing point. I wouldn't be charging my batteries in the winter months. i would pull them out of my boat, warm them up for at least 24 hours in my house before charging.
Your BMS should be able to handle that on the front line. I use a couple of 12V Overkill BMS units - one in the 4s pack I am building for my fishing kayak. In addition to the on the board temperature indicator, they also provide a separate connector that I put in between my batteries with the pack. You can setup the cutoff from their bluetooth module through your phone, it is also set by default to 0 degrees centigrade - most people change that to 1 or 2.

On a sidenote, I am finishing up a 12v 100 AH pack specifically for the trolling motor on my fishing kayak. Here's the thread: https://diysolarforum.com/threads/my-lightweight-portable-power-station-build.11456/#post-135464

I still have to add a few things but this one uses really lightweight lifepo cells.
 
I reached out to minn kota regarding support for my MK345 charger working with Lithium and they told me it's fine and to use the AGM setting. I'm tagging along as i want to build a 36v Lifpo4 setup for my 112lb thrust motor. Wondering if it's better to do a 12S 36v battery or three 4S 12v batteries and connect them in series. The latter would be easier for me to place them in the storage area. Would love to hear what others have done before taking the leap.
 
My suggestion is to build three 12 volt batteries reason I say this you can bundle the four cells in any way you want to maximize space in your battery area to have extra room to store a fourth battery for all graphs or dry storage for anything. Right now I am installing those 12v Facon tank heaters under my valence batteries to keep them warm while I do fall fishing in 30 degrees. I have heating pads for a few reason is. Valence batteries U27-12xp does not have a low temp disconnect. Keep them warm to charge. Warm battery discharge better over cold battery. I need one more big lithium batttery for my four graphs and heating pads. This winter I will look at doing only one DIY battery. If all works out the. I’ll make three more for the trolling motor depending on how the valence holds up.
 
Thanks for the recommendation. I'm in an area that won't need heating pads. Sounds like you're going to stay on the valence route. i'm hoping to find somebody who has built out three 4s lifepo4 batteries and then put them in series, so i can reference their design and lessons learned. I'm not ruling out the valence batteries, but not sure what i want to do about BMS.
 
If you make a diy battery you will need a bms for each battery. From what I learned is your BMS should be rated higher for your use. Example. My trolling motor max draw is 52 amps. I should use BMS rated for 100ah so it’s not working near maximum.
 
Yeah, was planning on getting bigger BMS as well. Was wondering how those are then wired together in series? And do all BMS support being tied in series? I ask, because there are some Pre-build lifepo4 batteries that don't support being put in series.
 
from what i was seeing on the BMS there are four wires and each wire goes to each positive cell of the four cells that will make one battery.
for those pre build lifepo4 batteries you will need to ask the vendor if they can be hooked in series. most prebuild drop in batteries like battle born, dakota, amped outdoors all can be hooked up anyway you want.
 
Seems you need a special BMS for 12v builds that will be put in series. That's what a rep at Daly told me recently. Might just go with 12S 36v even though that's not what i wanted to do.
 
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