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Winston

wrote:

(...)

Decent! How about this as a retrofit to the Harbor Freight cheapies:

push a pushbutton switch, which charges a supercap when you need it,
giving an hour or so runtime per press?

Iq = 0uA.
Battery life: Same as shelf life.
Parts list: homemade switch, supercap. $0.20.

Caliper starts blinking? Press the button again to keep it going.

I like that! But I can reduce the BOM size.
Just a (rotary?) switch in the battery cover.

If you leave it on, you get 10 months
out of the battery. If you use the power
switch religiously, you get 'shelf life'.

* A switch handling ~40 uA does not have to
be nearly as stout as one handling 'short circuit'
current into the super cap.

* Most super caps don't tolerate high current well.

* This mod is dead simple, reversible and does not
require access to a ground connection.

--Winston