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Discussion Starter #1
Hello everyone-

Picked up cheap go cart and converting to electric (https://gokartsusa.com/Baja-49cc-Off-Road-Go-Kart.aspx) for my boys.

Picked up this and bench tested (https://www.amazon.com/TDPRO-Brushless-Electric-Controller-Motorized/dp/B075WT34MK)

I randomly have a bunch of 18v ryobi lithium 5-6ah batteries so my plan is to power with 3 packs in series. Probably won’t get a ton of run time but I have 8 and a 6 port charger. May convert to a dedicated lithium battery if this works. I could do lead acid? They aren’t terribly expensive but so heavy!

The controller is rated to 48v so I may blow It with the 3 packs. But I’ll be running it at medium speed so hopefully it won’t freak out. I can’t do 2 packs as the controller low voltage shuts off at 41v.

4 newb questions:
1) is this crazy?
2) I want an emergency battery disconnect. Ones that handle full 60vdc are big and expensive. Could I put a 24vdc 15a switch between packs 1 and 2 in the series as a cutoff? Any other creative safe solutions? I want my 10year old to be able to fully shut down without difficulty.
3) what max amperage can I expect?
4) what fuses would I get?

Thanks, LB
 

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Discussion Starter #3
Thanks- a fresh pack is around 20v so 60v total. Should I put this switch in between the series or is it fine to put at end of whole pack even tho it may be 60v on a 48v switch? I’ve read about arcing/welding and all that and just nervous my kid will be on a run away train
 

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Anywhere in the series circuit does the job. Looked like rating was to 60 volts DC.
major
 

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Are battery terminal disconnects rated to break current? I was under the impression they were mostly to disconnect a powered down system to prevent drain and to make maintenance safer? Has anyone seen specifications for using them as an emergency disconnect (like how much peak current they can break)?

There are a bunch of solar power products that might work - you can pick up one of these 150v dc breakers in a variety of sizes for under 20 bucks - I think 63 amps is the biggest, which would be more than you need for the motor you have
https://www.amazon.com/MidNite-Solar-Breaker-150VDC-MNEPV60/dp/B00BSYSLXU/ref=psdc_13638744011_t1_B004EQRAQS

They are DIN rail mount, which needs some other parts for a clean-looking install, but you can just strap it down, too :)

I was also wondering if anyone with more experience could weigh in on the OP's idea of running tool batteries in series. I know some tools out there do use double batteries, but I wonder if too many series packs is going to spell trouble for the on-board BMS or anything?
 

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I often run my 24V Bosch hammer drill or saws on 2-12V Craftsman Li batteries without trouble. I think more than a few ebike diy guys use series connected tool Batts. Might check out endless sphere forum.

You should check out switch specs for break current rating. The product I showed had like a 1250A 10 second cranking rating, but no break rating. If used between battery and controller the load is capacitive, not inductive, so I would use it. And a failed controller isn't going to result in runaway when using AC or BLDC motor.

Dad should examine component specs, ask questions, and use what he's comfortable with. Get the driver protection (helmet, etc.) and go for it. Always some risk. But have fun.

major
 

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