In article , U
writes:

Where I live, in the woods of Maine, we have power outages.

Solar panels and all that stuff is quite expensive, but old car batteries
("old" is when it doesn't get my Diesel started in subzero temps) are not.

To make things just a bit comfi it would be nice to leave it in place with a
charger attached (right now I tote the charger around when needed).

Many things will run right off the batterie(s), others might need an
inverter.

So basically I am talking about a photovoltaic system without the
photovoltaic panels, sort off.


So which chargers can I leave permanently attached to a battery?

The word 'trickle charger' or 'shore power' comes to mind. How is that
different from my old Sears charger which does me good for many years
already (but I unhook it after a day at most!).

With good control of charging current and voltage, the battery can
"float" in the circuit, always connected to the charger or the AC mains
low voltage supply that can take over from the battery when mains are
hot. The space folks do that regularly from low earth orbit (90 min.) to
geo-synchronous (24 hours), using series power diode isolation.

Another thought is to check out computer UPSs which have already
been engineered and tested, ready to go off the shelf. Those can
handle up to 600 W loads for small servers and auto-switch to internal
batter in less than an AC cycle. Industrial-strength UPS models can
handle much more. A little, cheap UPS sits between my PC box and
line all the time now, can easily handle 300 W loads for several minutes.

Len Anderson
retired (from regular hours) electronic engineer person