Decent battery charger

[Oaktree]

Don't know about your old one. But I have 3 chargers and multiple battery maintainers and all of them have circuitry to not allow reverse flow. We have a lot of power outages and internet outages around here also!

All but one of my chargers are old school...a 12V transformer, a bridge rectifier and maybe a pilot light or ammeter. There may be a tiny bit of back leakage thru the diodes, but nothing that's ever been an issue.
These are all essentially trickle chargers, none will put out more than a couple amps. To prevent overcharging when being used as a maintainer I just put 'em on a timer, power on only 3-4 hr/day.
I have a lithium jump pack for when I need that functionality.

 

[John_Mc]

No need to put modern smart chargers on a timer - at least not the good brands like BatteryMINDer, NOCO, and some others. You can just hook them up and forget them, leaving them attached for months.

 

[Pixguy]

When I head south for 4 months every winter I hook up 6 Schumacher trickle chargers and I've never had a problem. 2 cars, 2 snowmobiles that are on 12 months, my tractor and my rider mower. All good.

 

[tacticalturnip]

I've been quite happy with this Harbor Freight staple...

Harbor Freight Tools – Quality Tools at Discount Prices Since 1977

Harbor Freight buys their top quality tools from the same factories that supply our competitors. We cut out the middleman and pass the savings to you!

www.harborfreight.com

 

[1Mech]

I've been quite happy with this Harbor Freight staple...

Harbor Freight Tools – Quality Tools at Discount Prices Since 1977

Harbor Freight buys their top quality tools from the same factories that supply our competitors. We cut out the middleman and pass the savings to you!

www.harborfreight.com

I bought one of those a few years ago, when my main heavy duty charger disappeared, (ended up in my neighbors garage, I guess we both forgot he borrowed it)
Anyway, the Harbor Freight one I bought is of rather low quality. It works, but if I put it on high charge, the needle jumps all over. I can only use it in 2 or 10 amp setting.
I found an older Schumacher my father in law had, it works great.
Often a good older model can be found for cheap at yard / estate sales.

 

[tacticalturnip]

I'm not surprised that quality would vary from individual item to individual item, lol.