36v trolling motor battery

[pilothawk]

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!

 

[45North]

Cordless tool Li batteries (DeWalt, Ryobi etc) are all rated 18v (although often marketed as 20v). They are coming out with larger and larger ones ... 5ah, 8ah .... Why not just put 2 of these in parallel to get your 36v? Or these same companies also have bigger Li batteries for yard equipment, lawn mowers etc. which also might be suitable. I'm all about getting double-duty out of things I seldom use in the course of a year.

You will pay a premium for these because they are proprietary, but when you're not fishing you can mow the lawn or fix up the house. (Your wife can thank me later!)

 

[SolarRat]

I think you guys both mean series and not parallel.

45North, they won't nearly be big enough.

With my 36v 101lb thrust troller I run 3 105ah group 31 lead acids in series. My motor draws about 31-33 amps at max speed, but I usually run it at about 20 amps which only drops the speed by about 0.4mph over it's max. So at 20 amps I get about 2.5 hours before the battery gets to the safe halfway point.

The more the AH's in the lithiums you get, the longer they will run. A 60ah 36v lithium would be about similar to what you have now (if yours are still like new), so use that to judge how big you want to go.

Sounds like you probably have a 112 lb thrust? Minn Kota claims 52 amps max, but you will likely never see above 36-38 amps at full.

Lithium batteries can be used below freezing, just not charged. So you can fish with them, just wait till they warm up to charge them. I'd still play it safe on the discharge level in below freezing temps.

 

[pilothawk]

Had parallel on the brain. You are correct, I have them in series, and it is the 112# ulterra.

Did you make your battery or are you using "drop-in" LiFePO4's. Also what are you using for a charger?

 

[Supervstech]

Ryobi 40v mower and such tool batteries would be similar voltage... and they come in 5Ah and 8Ah... to get all day use, you would need 12 of them... not very practical.

The LFP prismatic cells can discharge down to minus 30F... 100Ah set would be double what your SLA can put out... around 1200 for 12 cells... I'm not aware of a 36v bms though, so you would need a cell charger that charges via the balance leads like the rc crowd uses...

 

[pilothawk]

Had parallel on the brain. You are correct, I have them in series, and it is the 112# ulterra.

Did you make your battery or are you using "drop-in" LiFePO4's. Also what are you using for a charger?

I catfish and there are days when I rarely turn my trolling motor off.

I am interested in the LiFePo4's because of the increase in capacity vs weight, and longevity if treated right.

 

[Sparky]

B hookups has options: (I have no affiliation, just bought a few and haven't played with them much yet)

Search: 20 results found for "36v"

Battery Hookup

batteryhookup.com

 

[SolarRat]

Had parallel on the brain. You are correct, I have them in series, and it is the 112# ulterra.

Did you make your battery or are you using "drop-in" LiFePO4's. Also what are you using for a charger?

I'm still using 3 group 31 lead acid batteries in series for 36v 105ah. They can get me home in an emergency from 15 or 20 miles away if the gas motor dies, which was my main concern. I'm currently using an on-board ProMariner 3 bank charger. I'm not doing much fishing lately, just cruising on the pontoon.

We've been using the electric motor more and more for just cruising through the canals or harbor, and I'd like to add some solar panels. I don't want to spend a lot on a 36v system, because it won't be around for long. I'm not using the stock speed control as it died, I'm using a speed control rated up to 60 volts, and will likely get a bigger electric motor at some point soon. So I want to step up to a 48v system (Lithium), which I can more easily get charge controllers and inverters for (I'd like to use the boat as an emergency power supply/generator).

 

[heavy-impact]

I have the 112 Ultera and will be using a brand new Chevy LG 5.94kWh Li-ion battery pack that I purchased from battery hook up. Battery specs are 42 to 28v, 19"x14"x4", 72 lbs. Minn Kota says Li-ion is OK but not to run it at full power for long when the voltage is still above what lead acid puts out. I'll run it without a bms because the charger limits the max voltage to 42v, a 60 amp breaker limits max discharge current and I'll set a low voltage alarm on the monitor. I added a 2 amp active balancer to the battery that keeps the cells balanced to .004v. I haven't run the boat yet since it's still in my shop being refitted but this should be plenty for my 1 day fishing trips.

 

[Supervstech]

I have the 112 Ultera and will be using a brand new Chevy LG 5.94kWh Li-ion battery pack that I purchased from battery hook up. Battery specs are 42 to 28v, 19"x14"x4", 72 lbs. Minn Kota says Li-ion is OK but not to run it at full power for long when the voltage is still above what lead acid puts out. I'll run it without a bms because the charger limits the max voltage to 42v, a 60 amp breaker limits max discharge current and I'll set a low voltage alarm on the monitor. I added a 2 amp active balancer to the battery that keeps the cells balanced to .004v. I haven't run the boat yet since it's still in my shop being refitted but this should be plenty for my 1 day fishing trips.
View attachment 13381

I would not recommend charging any lithium battery without a BMS especially a lithium ion battery! Especially especially on a boat! Fire is a very bad thing...

 

[heavy-impact]

I would not recommend charging any lithium battery without a BMS especially a lithium ion battery! Especially especially on a boat! Fire is a very bad thing...

I don't charge it on the boat and I think most chinese BMSs are more of a fire hazard than the battery. I don't think this chemistry causes fire anyway. I believe they only vent steam from the cells themselves. I have a backup plan for just about any situation.

 

[Supervstech]

I don't charge it on the boat and I think most chinese BMSs are more of a fire hazard than the battery. I don't think this chemistry causes fire anyway. I believe they only vent steam from the cells themselves. I have a backup plan for just about any situation.

LiFePO4 is the only non explody battery chemistry I am aware of... I would definitely want a quality BMS on any expensive battery though. Limiting the peak pack voltage does NOT protect any individual cell from unbalanced overcharge or undercharge. Even if you are not worried about fire, damaging the cell would be expensive.

 

[heavy-impact]

LiFePO4 is the only non explody battery chemistry I am aware of... I would definitely want a quality BMS on any expensive battery though. Limiting the peak pack voltage does NOT protect any individual cell from unbalanced overcharge or undercharge. Even if you are not worried about fire, damaging the cell would be expensive.

There are plenty of IMR "safe chemistry" cells, pouch and 18650. You really have to beat on them to make them pop and when they do it's nothing but steam... no fire.

 

[Fish Freak]

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!

 

[heavy-impact]

I would not recommend charging any lithium battery without a BMS especially a lithium ion battery! Especially especially on a boat! Fire is a very bad thing...

I've got a bunch of cycles on the battery pack now and it's been perfect without a bms. The 2 amp active balancer keeps it in perfect shape.
This is a very high quality battery pack with the tabs factory welded so there is no chance of a single cell overcharging. I think it's as safe as it could possibly be. This pic is after 2 days of fishing.

 

[Fish Freak]

I've got a bunch of cycles on the battery pack now and it's been perfect without a bms. The 2 amp active balancer keeps it in perfect shape.
This is a very high quality battery pack with the tabs factory welded so there is no chance of a single cell overcharging. I think it's as safe as it could possibly be. This pic is after 2 days of fishing.

How many hundred amp hours does that cell equate to? Does that jive with the performance you've gotten? I wanted to use prismatic LifePO4 cells because it seems they can handle more cycles than the lithium-ion cells I've compared them to, but that Chevy (volt?) battery, isn't that something like lithium manganese cobalt chemistry?

 

[Bob B]

If I'm doing the math right ... at 36V 5.94KWH would be 165 AH at 36V.

 

[heavy-impact]

How many hundred amp hours does that cell equate to? Does that jive with the performance you've gotten? I wanted to use prismatic LifePO4 cells because it seems they can handle more cycles than the lithium-ion cells I've compared them to, but that Chevy (volt?) battery, isn't that something like lithium manganese cobalt chemistry?

Like Bob said they're rated 165ah but they've been giving closer to 170. I don't know the chemistry, I just know I'm happy with the battery pack and active balancer. Suits my needs perfectly. I have this one mounted in a Pelican 1550 case and I have a backup battery pack made up of 200 LG MJ1 18650 cells for 70ah in a Pelican Air 1485 case. If my power goes out at home I take them inside and run a 3000w inverter from them.

 

[vtx1029]

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!

So your running 3 of the BMS's in series?

 

[Rbertalotto]

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