Absolute Cheapest Dummy Load To Test Your Battery


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1:44 PM
Mar 24, 2022
Instead of buying 70 100w 120v light bulbs or 7 range top heater elements you may want to save money on a very temporary dummy load.

Pulverize charcoal and put it in a PVC pipe after you insert two 40 cm long electrodes positioned within mm of each other. Angle is easy to tape together. Then fill half way with water and check the amps from a single 3.6 v Battery. Add salt and then water until you get down to about 1 amp.

Put a fuse inline and then apply the current from the new battery. This is not ohmic so you'll need to check the current again at full voltage.

It's not really a pure resister so the ohm meter was worthless.

Raise the electrodes out of the slurry to draw less current.

I blew a 15 amp fuse and used 1 cm wide al foil instead. Steam soon boiled out the top of the pipe but I held in there for a full minute. No hot spots anywhere on the battery.

I had charged up 0.6 v earlier -- half an hour at 1.18 amps -- and the voltage dropped 0.4 v in about the minute and a half I was actually zapping the thing.

This comes out to be an average of ~ 18 amps.

I'm not going to bother with the 5 minute test with BMS. Hardly any hills in the valley take much more than a minute anyway.

The original BMZ looked like a prototype, like no one had done a thorough analysis of the possible wear from possible vibration that could short the battery. So BMZ adopted a throw eberthang ya got at them approach. The battery was held together by dozens of nifty tapes and sealants -- a Maginot Line mentality!

Now I'm starting to wonder if I took enough care. My reasoning was the down tube should be the battery holder. Stuff that battery tightly enough in the down tube and there is no intra battery rubbing. Sure would hate for it to short out a year from now.