I think I found the right battery relays

They make all kinds of relays and a lot of electric forklifts use them to switch their motors. I ordered a used one from Ebay for testing. 35€. The good thing is that they are made in the UK. Heavy duty and also heavy weight, but rated for high currents and voltages.

They don’t have Anti-Spark, but I think we could add a resistor to the contactor. If not, we could add an auxiliary relay just for antispark. The Arduino that controlls this will then connect the antispark before the main relay is connected and then disconnect it again.


So you were the one bidding higher. Just kidding, those should work, I found a similar one on german ebay a few weeks ago, but I thought they don‘t come up regularly enough to be a permanent solution for me. I looked at the Albright SW180. Those are quite expensive new. Yours should be quite efficient, at 150A it‘s specifed for only 40mV voltage drop. That means you only have 6W conduction losses in the relay at full power. Thats more than the 2W an electronic switch would have, but still very small compared to the losses in the wires to the motor. Not as nice with your relay is the continous actuation power for keeping the relay on. The datasheet says 7 to 13 W. But again that should be at least ten times less than what your motor needs, so it will shorten your ride only a bit. Just remeber to switch it off after riding, otherwise it will drain your battery pretty quickly.

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Hi, looking for a bit of help or to see if anyone else has had a similar experience.
I have got a seaking esc 130ahv with 12s batterys 2 x 6s in series and i had the anit spark resistor burnt out the other day. The connector was connected, which is weird.
I have contacted supplier to find out what size anti spark resistor they using and what watts, and its a 5 ohm 3 watt resistor.
i have now installed a solenoid to cut the the battery power to esc, with a relay that brings in a anit spark resistor across the solenoid, this resistor burnt out last night. I replaced it now with a 50ohm 5watt and seem to be okay for now. Has anyone else experienced similair issues?

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5 ohms is way too low. 100 works better depending on your capacitor bank. I use Gigavac waterproof hermetically sealed 350 amp solenoid with 500 ohm 3 watt resistor. Remember those guys use 24V not 48V so you need to increase the resistance a lot more.

I had done some calculations before on why a 50 Ohm resistor with 5 or 3W capability should be about right over at The Max Maker Build - #13 by Flo - Builds - FOIL.zone.

I have to admit that I just wanted to ride and left the calculations aside. I had a 1 Ohm 5W resistor floating around my bench and have been using it as precharge/antispark with 16mm^2 cables and 5x470uF Capacitors on the ESC. So far it did survive :slight_smile:

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