YONHAN Battery Charger 10-Amp 12V and 24V Fully-Automatic Smart Car Battery Charger

I keep one of these in it

If you want something to keep a battery maintained, help recover a weak one, and fit into regular garage life without much drama, this is a strong practical choice. It is not a fancy product. It is a useful one, and that is usually what I want from this kind of thing. Keep in your car, garage even your boat. You battery dead just pull this charger out and bam you can charge your battery yourself.