Charging car battery off AC?

[Jeff Nicholson]

I did a house today where the seller had a car battery charging through some kind of adapter from a 30 amp circuit. The intent was to have the battery ready to power an inverter for the sump pump if power went out. The inverter was not connected to the battery at the time. My question is, does this present enough of a backfeed situation in an outage to worry about? The adapter had warnings all over it, telling me to read the manual... wherever that is.

[Greg Fretwell]

You can't backfeed the grid through a battery charger, for a number of reasons.

[Jeff Nicholson]

Actually, now I can see why not. Thanks.

[msaxton]

Actually the general idea might not be so bad, I have seen setups like this in alternative IE solar homes,but the setup here is just not right , I believe that it needs an isolator and a power loss switch that will seperate the two systems yet draw on the alternate when needed....don't yell at me if i don't have the terminology right , but thats the general idea

[Greg Fretwell]

The easiest way is to just keep the pump plugged into the inverter, running off the battery all the time. Then you use a good "automatic" charger connected all the time to keep the battery up. I would still want to see this whole cludge in a fireproof enclosure and the battery separate in a well vented place, in a battery box (similar to what you have on a boat).