I saw some similar breakers to those on Amazon. The ones you mention below have a 50V rating. The peak charging voltage for a 48V battery system is ~56V. I'm reluctant to use a breaker that's only rated to 50V in a system that will regularly hit and slightly exceed that rating.
I ended up ordering this one from Amazon, with a rating of 12V - 72V:
Though, that one will take a couple of weeks to arrive. I was thinking of temporarily putting a 30A inline fuse in the circuit while I wait. And then.... discovered all the public boat ramps are still closed. The fully qualified breaker may be here before I can get good access to a boat ramp.
The first test was to run the motor in a garbage can filled with water. But that only allowed me to get the motor up to 100W (~2A).
The next test will be to back the boat down a boat ramp so that the motor is in the water, and run the motor at the dock for about an hour at about 900W. I'll be watching the voltage on the motor, and probably taking data points every 5-10 min. At 900W (~18A) to 1000W (~20A@50V) - I am expecting that I'll end the test due to low battery voltage before I hit an hour. But this will give me a good idea of how well the battery is working compared to the advertised rating. And it will also give me confidence that I can run the boat a long enough to take it off the trailer and putz around.
From previous tests with AGM batteries, 600W got me about 4mph, while 960W only increased that another half mph. Cruising at 500-600W (~10-12A) should be about the sweet spot for this boat, and should hopefully get me well over an hour of cruising on a 20Ah battery, with some margin to spare.
John
On Sunday, May 3, 2020, 09:29:26 PM CDT, sw via groups.io <v1opps=yahoo.com@groups.io> wrote:
Maybe these will work for you?
https://www.ebay.com/itm/30A-300A-AMP-Circuit-Breaker-Fuse-Manual-Switch-12-48V-DC-Car-Boat-Waterproof-/143422006751
On Sunday, May 3, 2020, 05:27:43 PM PDT, john via groups.io <oak_box=yahoo.com@groups.io> wrote:
I'm using a 48V E-bike battery pack in a proof of concept type experiment.
The battery pack is rated at 20Ah, with a discharage of 50A, and max discharge of 100A.
The electric motor can pull up to 100A - so I'd like to put a circuit breaker in line with the battery, with the idea being that if someone accidentally gets too excited on the throttle, the circuit breaker would trip long before the BMS does. (This is especially after the relevant post about the BMS protection circuits being an unknown quantity in sealed battery systems!)
Questions:
1) What is a good circuit breaker for a 48V system? I'm thinking around 25-30A. Most seem rated for 12V, some up to 48V. I've only found one so far that is rated for 72V.
2) Can I use a "48V (max?)" rated circuit breaker? Is that intended for a 48V system that really goes up to 56-58V at peak charge, or is it really strictly limited for 48V (and intended for 32V systesms)??
3) Is a standard 30A blade fuse ok to use in a 48V circuit? Many don't seem to have voltage ratings...
Thanks,
John
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