Need recommendations, regarding suitable battery

Thread Starter

JoeReal

Joined Oct 25, 2020
4
Hello Everyone!

I bought a Lithium Magnesium Iron Phosphate Battery, 138 AH and 13.7V, to be used to power my Newport Trolling Motor. The problem is the warranty on the motor will be voided if I use a Lithium battery. The manufacturer rep said that the Lithium ion batteries outputs a constant voltage of 13.7V no matter what the load is, until of course it starts to run out of charge, and such high voltage could burn out the electric motor that is expected to be powered by a deep cycle 12V battery. I really like to use the Lithium battery because it is very lightweight and high energy density to last a very long time compared to deep cycle lead acid batteries.

The 12V electric motor is rated for at 20A continuous and short peak bursts of 30A. What's the best existing 30A product to use to protect the motor so that it won't burn from the slightly higher voltage. Where to get 12V 30A voltage regulator from 13.7 to 12V? This is a small drop but require large current. Is the buck boost controller better? Where can I buy these? Do I need to assemble a circuit for this?

This problem is becoming quite common as lithium ion batteries become more available at affordable prices. The problem is that their voltage output is constant even with load, and many electric motors aren't designed for that. Any help would be appreciated. Thanks!
 

MrChips

Joined Oct 2, 2009
22,107

Ian0

Joined Aug 7, 2020
759
The manufacturer's rep is fibbing to cover up some problem with his product.
Did he say you could use ANY deep cycle lead-acid battery? A really big one isn't going to drop any significant voltage at 30A load! And that's OK and the Lithium isn't?
 

psahd

Joined May 2, 2014
2
Hello Everyone!

I bought a Lithium Magnesium Iron Phosphate Battery, 138 AH and 13.7V, to be used to power my Newport Trolling Motor. The problem is the warranty on the motor will be voided if I use a Lithium battery. The manufacturer rep said that the Lithium ion batteries outputs a constant voltage of 13.7V no matter what the load is, until of course it starts to run out of charge, and such high voltage could burn out the electric motor that is expected to be powered by a deep cycle 12V battery. I really like to use the Lithium battery because it is very lightweight and high energy density to last a very long time compared to deep cycle lead acid batteries.

The 12V electric motor is rated for at 20A continuous and short peak bursts of 30A. What's the best existing 30A product to use to protect the motor so that it won't burn from the slightly higher voltage. Where to get 12V 30A voltage regulator from 13.7 to 12V? This is a small drop but require large current. Is the buck boost controller better? Where can I buy these? Do I need to assemble a circuit for this?

This problem is becoming quite common as lithium ion batteries become more available at affordable prices. The problem is that their voltage output is constant even with load, and many electric motors aren't designed for that. Any help would be appreciated. Thanks!
The Rep really does not know what he is talking about. If you are only running your trolling motor at full power, you would have a problem regardless of which battery you are using. It is not about the difference in voltage, it is about the current draw of the motor. TO be safe, limit your throttle to 98% of max power and you are good to go!
 

Thread Starter

JoeReal

Joined Oct 25, 2020
4
Thanks! I bought a 50A diode which should help in the voltage drop, so as not to void the warranty. I will also limit the settings to just 85% of highest load, so it means set the motor to only level 4 instead of level 5. It has settings of -3 to 5, the negative numbers are for reverse propulsion.
 

Thread Starter

JoeReal

Joined Oct 25, 2020
4
A 12V battery is actually 2.1-2.2V x 6 cells = 12.6 - 13.2V
So 13.7V is not that much higher than 12.6V.
12V batteries are normally charged at about 14.8V.

If you wish you can put a 30A rectifier mounted on a heat sink in series between the battery and the motor.
This will reduce the voltage by 1.0-1.5V depending on the current and temperature.

Example:

View attachment 220627

https://www.digikey.com/en/products/detail/vishay-semiconductor-diodes-division/VS-1N1184/81666
Thanks! I bought a 50A diode which has a voltage drop rating of 1.1 Volt.
 

LowQCab

Joined Nov 6, 2012
65
This sounds highly suspicious that the Motor is "Rated" for ~20 Amps, and "Short-Peak-Bursts" of 30 Amps.
I smell BS.
Is this a "Motor Rating", or is this a "Controller Rating" ???
Both should be "Water-Cooled", so Heat shouldn't be an issue.
This Trolling Motor doesn't have an Ammeter installed on it,
so how is anyone supposed to know when it is being pushed over ~20 Amps ????
Why are you even asking for "permission" to run a different Battery Type ?
If it smokes under normal usage conditions, warranty it, and do not mention ANYTHING about a different Battery.
The Battery you are using is "nominally" the same Voltage as a Lead-Acid Battery.
If you were trying to run it on ~24 volts, that would be your bad.
This is what the "Customer Ratings" Section is for on probably every On-Line Store that sells this unit.
There's probably 20 different YouTube Videos talking about how good or bad that Model may be.
Do your "Due Diligence" before buying, or it's completely your fault if you bought a poor design.

Alternatively, (since this IS an Electronics Forum), if it smokes, take the Motor apart and inspect it.
There is probably a Bi-Polar Power Transistor mounted to the Motor Housing, which is probably the culprit.
Replace it with a beefier part, and never worry about it again.
Or, design your own control system from scratch, it will likely be far more efficient as well.
It is very unlikely that the Motor itself will suffer from too much Current/Heat since it's Water Cooled,
but a cheap, way-underrated Transistor can pop when it's ice-cold.

A Diode in Series is just a totally wasteful endeavour.
.
.
 

bassbindevil

Joined Jan 23, 2014
110
If what you have is a Valence U27-12XP, the manual says nominal voltage is 12.8V, but the range from full to discharged is 14.6 to 10.0 volts. That is higher than lead acid, but it's unlikely that a motor or controller would be damaged by an extra couple of volts unless you're using WOT while tangled in weeds or something. If the controller does fail, there's 60A PWM controllers on ebay (etc) under $20.
According to this thread, some Newport speed controls are just tapped power resistors; simple, but inefficient:
https://forum.gon.com/threads/electronic-speed-control-for-trolling-motor-diy.925685/
 
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