Can I power a 46 lb thrust trolling motor with a lithium solar generator??

[magentawave]

I bought a 46 lb thrust trolling motor off of Amazon. The seller says I need a 12 volt 60 amp hour battery to power it but some say the little 35 amp hour SLA battery from Harbor Freight will work.

I can buy a $75 marine deep cycle battery from Walmart but they are heavy. (Weight matters because I have to carry the motor and battery back and forth from my car to the dock.) Harbor Freights smaller and lighter sealed 35 amp hour battery is also $75. From the dock to my boat on its mooring is a 5 minute ride so I don't need this motor for much.

Between the battery and a charger I'll be looking at around $125 with tax but for about $100 more I can buy a cheapo 500 watt "solar generator" on Amazon. https://www.amazon.com/s?k=500+watt+...f=nb_sb_noss_1

QUESTIONS, PLEASE...

1) Can I power a 46 lb thrust trolling motor with a 35 amp hour battery? (Again, its a 5 minute trip each way from the dock to my mooring.)

2) I am finding out that the 12 volt port on these solar generators are limited to only 10 amps. Has anyone figured out a way to power their trolling motor with one of those little "solar generators"?

Thanks!

 

[Bob B]

You need to know how many amps the trolling motor is going to draw. There is no way 10 amps is going to cut it.

On this thread, the OP has 2 35 AH batteries in parallel and they aren't cutting it.

Lifepo4 trolling motor help

Someone please help- I purchased 2 Power Sonic PSL-12450 Lifepo4 They are rated 45Ah 25a draw each I have them ran in parallel to get 90ah and 50a draw My trolling motor is Minn Kota 55 lb thrust 50a draw It will run all day up to speed 3 On speed 4 and 5 the batteries cut off and then reset...

diysolarforum.com

 

[magentawave]

The seller on Amazon said I need a 12 volt 60 amp battery for my 46 lb thrust motor.

I read that thread (thank you) and I'm a little confused because the guy that recommended the Harbor Freight 35 amp hour SLA has been using it to power a 55 lb thrust trolling motor for a couple years. His boat (and mine) are small dinghies and his boat is a lot closer to the dock than mine is but he said it works great.

 

[Bob B]

The AH rating of the battery is mostly irrelevant for such a short distance .... what you need to know is how many AMPS the trolling motor will draw and how many AMPS the battery can provide.
If the seller can't provide the AMP draw spec I would look for another seller who can. Big difference between amps and AH.

The SLA battery is probably not current limited like the lithium battery in that thread, but you need to know the AMP draw specs on both sides.

 

[magentawave]

Okay, I found this review on Amazon for the same motor that I bought...

I am using this motor with an Index Excursion 4 inflatable boat and have been very pleased with it so far. I purchased the motor mount kit from Intex and also a 35Ah sealed battery and a case for it with a battery monitoring system (shunt). We recently went out fishing with my son, wife, and myself, a total weight of about 400 pounds plus some gear and the battery.
The motor performed quite well - very quiet (especially at low speeds) and had pretty good thrust even in some windy conditions. I did have a problem at first since I had wired a fuse inline and was using a 10amp fuse - as soon as I turned the speed up to level 3 (out of 5) it blew the fuse. Fortunately, I had brought a few spares with us, so I swapped it out for a 15 amp fuse. Based on the readings from my battery monitor, it seems to use around 2-3amps on speed 1, about 5-6amps for speed 2, 7-8 for speed 3, and then it jumped way up to 15-16amps for speed 4. I don't think I ever got it up to speed 5, since I didn't want to blow my fuse again. The speeds don't seem to be evenly spaced, at least not based on power draw. I have thick enough wiring that I can probably go up to 30 or 40 amps with no issues, but haven't tried using a fuse that high to see what the draw is for speed 5.
Once you know the power draw of the motor, it is fairly simple to determine how long your battery will last. With a 35Ah battery, you can draw down to 50% charge fairly safely, which means you can use about 17-20Ah. Running the boat on speed 1 should last a good six hours or more. Speed 2 maybe three hours, etc.


Me again. So, for some context, my body and weight of my dinghy plus gear would be close to 300 lbs.

He said this about the amps...
SPEED ONE: 2 to 3 amps.
SPEED TWO: 5 to 6 amps.
SPEED THREE: 7 to 8 amps.
SPEED FOUR: 15 to 16 amps.

Based on what he said there, could I plug the motor into the 12 volt port on a solar generator if I don't go higher than speed three (7 to 8 amps)?

 

[Bob B]

I personally wouldn't put together an underpowered system for the trolling motor on my boat ..... especially if it's going to be your only way of getting around ..... better have some paddles with you.

 

[magentawave]

It's a trolling motor so I'm not going to be using it for anything gnarly and yes I always have a paddle for backup. But if it only uses 7 to 8 amps on the third speed then how is that underpowered?

 

[Bob B]

I don't know what trolling motor you are looking at for sure, but I looked up the specs for a Minn Kota trolling motor. It looks like they are showing that the trolling motor would draw about 1 amp per pound of thrust. A brand x trolling motor might not be quite that efficient.

So, you would have a 46 pound trolling motor that you can only operate at 7-8 pounds thrust to keep in the safe range for the power available.

What happens if you accidentally draw too much current? Does it blow a fuse or trip a thermal breaker?

I don't know if you have ever operated a trolling motor, but there is no way I would have a trolling motor on my boat that could only operate at a fraction of it's capacity. What happens when you have wind?

You could probably get by with a small FLA or AGM battery.

 

[magentawave]

I could put a 15 amp inline fuse on the positive wire. Amazon has free returns so worst case scenario I'll return the lithium power supply to Amazon and buy a sealed 35 amp hour battery and charger from Harbor Freight.

 

[macheung]

You will need to find the maximum discharge rating of the battery. Generally, most batteries in the 20-100Ah range can be discharged at max of 1C, a rate where you would drain the battery in one hour. So a 35Ah battery usually will be OK for up to 35A of current draw. Note that capacitors are often quoted at 1/20C, so capacity when discharging at 1C may only be 70% of rated capacity. And you would only want to drain lead based batteries to around 50% and recharge them to full quickly, if you want them to last. LI based batteries can be drained to 0% if you have a competent BMS.

A 35Ah AGM battery can be drained by 18Ah or so without damage and likely have a max discharge current around 35A. 15A discharge is less than 0.5C so it should be no sweat at all for it. You can likely run it at speed 4 for an hour on a regular basis. Just charge it back up soon after using.