Mike Scott wrote:
I'd like to use this breaker I have, but now have 50 LiFePo calls instead
of the 12 12V gels. Is it time to break out the spare breaker and wire them
in series?
The rating says "Max 160V", but charging will go above that.
The circuit breaker's 160v rating isn't absolute. The complete rating
would be something like "can safely interrupt 160vdc at 10,000 amps with
a resistive load ONE TIME".
Sometimes the manufacturer gives a set of curves, showing the safe
interrupting voltage at different currents, and with different kinds of
loads. If the current is lower, the voltage it can safety interrupt goes
up. If the load is worse (inductive), then it goes down. In your case, I
doubt that the load will be inductive. Both the batteries and the
charger will appear as capacitive loads.
Assuming that your circuit breaker is built similar to others that *do*
have these full ratings, I would expect it to behave something like this:
160vdc at 10,000 amps resistive
250vdc at 1,000 amps resistive
350vdc at 100 amps resistive
Thus, you can probably use it at 250vdc in a circuit that can't produce
a fault current over 1000 amps. A worst-case failure in your charger is
unlikely to be able to draw this much current, so it should be safe.
The more serious question is: If the charger does fail (shorted output
capacitor or rectifier), it may draw 100 amps, which is NOT enough to
trip that breaker! So it is important to have a fuse in the charger
output so something WILL blow to stop the current. Otherwise, you can
get one heck of a fire if the charger fails and the batteries dump
160vdc at 100 amps back into it!
--
For every complex problem, there is a solution that is simple, obvious,
and wrong. -- H.L. Mencken
--
Lee A. Hart, http://www.sunrise-ev.com/LeesEVs.htm
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