On Sun, 28 Jun 2020 12:38:16 -0400, Paul
wrote:

T i m wrote:
On Sat, 27 Jun 2020 23:20:29 +0100, alan_m
wrote:

snip

Any circuit that requires a heat sink in such a small enclosed die cast
box is going to run at elevated temperatures.

And that's enough to suggest to me that it might not be the best
solution, if you are looking to conserve energy?

snip

If you draw high amperage through the switch, you're
not exactly conserving energy.

Well, if that's what you want to do I'm not sure the fact that 'the
switch happens to waste energy (because it's not 100% efficient) is
the issue is it? The issue here was nor wasting *unnecessary* energy
that *isn't* part of the desired load (even if the load itself is
inefficient etc)?

It's a linear solution.

It operates in its saturated mode (full on), and the losses
are a function of the channel resistance (I^2*R).

https://www.mouser.ca/datasheet/2/38...f55-956481.pdf

Rds-on = 0.018 ohms

At 10 amps, loss = 1.8W, while the load receives 12V*10A = 120W.

Then in the absence of a better alternative, that's part of the deal.

In normal situations, the junction capacitance might be a
problem for allowing such a device to switch repetitively
at a high frequency.

In this case, response time isn't particularly a problem.

Quite?

So, the issue is back to ... can you afford to keep replacing
over-discharged (with best case reduced recycle count, worst case
completely ruined (sulphated, if LA) batteries or are you willing to
sacrifice some capacity for their protection? Yes / No.

The alternative would be to do things like:

Cycle the battery manually with a mains charged one every 'n' interval
(where n was fairly constant pre the addition of the controller /
solar panel) V n + x, where x is the time gained as a function of
adding the solar panel?

Monitor the battery voltage manually and remove it before it went
below a safe threshold.

Monitor the battery remotely and remove it (or the load, add the
charger etc) before it became over-discharged.

Ensure the worst case load V charge never goes negative.

Ensure the capacity of the battery is large enough to maintain the
load between instances of sufficient charge (if the load isn't
constant etc).

Cheers, T i m