24 Volt Trolling Motor Battery Build/Questions

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Lithium18650
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24 Volt Trolling Motor Battery Build/Questions

Post by Lithium18650 » Jan 30, 2017 3:02 pm

I am in the process of building a 18650 based module (7 or 8S 40P) for powering my 24Volt Minnkota Terrova trolling motor. I am planning on building the following but am looking for any suggestions or personal experience from the group which could help me optimize my final design. I am a little concerned with the proper voltage going to the trolling motor. I do not want to fry a $1,500 unit! I have called Minnkota and they were less than helpful. They said the operational voltage was 23.4 to 25.6 volts however they would not tell me what safety factors they have built into the circuitry. I suspect there is a larger range.
  • Should I do a 7S or 8S
  • I am planning on skipping the BMS and using a voltage monitor/alarm to indicate low voltage.
  • If I go with 8 S I could use 2x4S modules to enable charging with a hobby charger.
  • If 8S is used the voltage will be too high according to Minnkota. My thought was to add a 60 AMP PWM on the output. Will the PWM be "too dirty" to power the TERROVA which has its own PWM?
  • Will a PWM work if the actual voltage drops below the setting it is at - basically just letting pass through voltage through without reduction?
Any thoughts and experiences are greatly appreciated.

mrzed
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Re: 24 Volt Trolling Motor Battery Build/Questions

Post by mrzed » Feb 01, 2017 1:02 am

Use 7s. Safe replacement for 24v lead and the bottom is still well above the average for the 24v lead if you are looking to boost power. If the standard power for the motor is enough for you then it's worth considering 6s even, so you can use a standard hobby charger.

Lithium18650
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Re: 24 Volt Trolling Motor Battery Build/Questions

Post by Lithium18650 » Feb 01, 2017 11:45 am

I like the idea of 7S however the upper end of the voltage range still scares me a bit (without PWM). I believe 6S will be a bit more performance than I want to sacrifice. Your suggestions did however, get me to thinking. I could buy a PWM now and run my current 24V Pb batteries through it and limit the voltage to the 6S specs and see how it performs. This will prove/disprove the performance of 6S and give me a feel for how the PWM works with the PWM in the Minnkota, all while never having enough voltage to fry anything. If 6S works fine, I can get rid of the PWM, if not, I am set for 7 or even 8S.

I also found a Turnigy 8S hobby charger for less than $50 so that helps from the charging front if I go above 6S.

I really hope that a PWM works well as it would allow me to use this cell for many applications down to 10 volts if needed!

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Monstarr
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Re: 24 Volt Trolling Motor Battery Build/Questions

Post by Monstarr » Feb 02, 2017 10:49 am

Very unlikely that anything will get 'fried' when you go to 28/29 volt.
Do those Minnkota trolling motors also have a connection for external 24 volt leadpack? Those are 28,8 Volt fully charged.

Or extract the original drive unit and install an appropriate Kelly brushless controller to be sure.

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