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1. 07:04 PM - Re: Re: DC clamp meter (Robert L. Nuckolls, III)
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| Subject: | Re: DC clamp meter |
>Does this sound like a reasonable way to do a meaningful capacity
>check? It does to me, but what the heck may I be missing? Seems
>like the hardest thing to do will be rigging up the resistive dummy
>load (open for ideas) so I can consistently do the load test per
>battery year to year.\
Okay, got a tighter box around your goal. Probably
doesn't need to be that complicated. You know your
endurance loads to a reasonable degree of accuracy.
The really cool thing about Li batteries is their
very FLAT discharge curve as a consequence of low
internal resistance. This means that energy delivered
to the terminals is relatively constant irrespective
of load. So consider getting some of these.
https://tinyurl.com/ydg62u2r
an order of 5 pcs is about 8 bux delivered to your
door. Mount 4 of these to a chunk of aluminum say
6 x 6 inches or so. .06 or more thick. Space them
out over the surface. Hook all four in parallel
to make a robust, 1.0 ohm resistor.
This resistor connected to one of your batteries
will discharge right at 12.5 amps. Time the interval
to discharge limit with this load.
Since you have quite a bit of time on these
batteries, you don't have an as-new benchmark
but you now have as-is benchmark.
Maybe the a.h. number isn't really that
useful. Rather, it's time to trip
the discharge limiter. That's pretty close
to your as-is endurance value. When
that number is below design goals, change
the battery.
Bob . . .
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