alan_m wrote:
On 27/06/2020 22:08, Paul wrote:

https://www.briandorey.com/post/low-...-using-max8212

https://datasheets.maximintegrated.c...11-MAX8212.pdf

The leakage current isn't zero, but it's a relatively simple circuit.

I wonder if it oscillates around the cut off point. 0.3V hysteresis
seems too low.
Battery under load gets to 12.4V and the circuit cuts off the output.
Battery no longer under load and recovers to 12.7V and circuit restores
output.
Battery now under load at 12.4V and ..........

Any circuit that requires a heat sink in such a small enclosed die cast
box is going to run at elevated temperatures. I personally would have
chosen a capacitor temperature rated at 105C

That would depend on the channel resistance and the load current.
As to what extent it would heat up.

I thought the voltage trip values a bit silly, but using the datasheet,
you can likely adjust it.

A tight hysteresis loop like that, might be intended for cases
where the solar panel cannot provide an infinite amount of power,
the "application" requires motor power at fairly closely
spaced intervals, and so the time to charge is being reduced
a bit. So the thing runs in "spurts".

If you set the hysteresis for the entire battery charging range,
it might take a number of hours for the battery to refill, and
maybe the barrel full of water overflows or something.

I suppose there's a value statement involved here, about what
the output resistance of a battery is. If the battery is elderly,
you might well run into cases where that circuit oscillates.
If the battery is "solid", then it'll be unflappable at low load.

My car battery went from 12.8V to 9V with a 150A load on it.
But I couldn't tell you whether that's a "healthy" battery or not.
4V for 150A. At 25A, that would be 4/6V or 0.66V, which would
run afoul of the tight hysteresis. So maybe a 10A load would be OK.
Even if the circuit had a fuse, we'd have some idea what he
had in mind :-) But there's no fuse. Short the output and
see what that MOSFET can take ???

Paul