DIY: Charging a car battery with a home inverter

Hence I devised this easy contraption that one can add to the existing inverter battery circuit to help charge the automotive batteries through the same smart charger that the inverter uses.

BHPian HimuraKenshin recently shared this with other enthusiasts.

I happen to have four cars - a Fiat Linea MJD, Swift 1.3L Gen 1, HM Ambassador Classic and Premier Padmini. With the second lockdown upon us, it is not possible to keep the cars running and hence the batteries in optimal condition. Letting batteries discharge reduces their life as well as their power capacity (due to sulfation).

To counter this, in the past, I have used transformer-based (not smart) chargers which used to feed a constant current to the battery and hence needed to be looked into every few hours to ensure that you aren't overcharging. This particular rudimentary charger of mine also went kaput a few months ago.

Hence I devised this easy contraption that one can add to the existing inverter battery circuit to help charge the automotive batteries through the same smart charger that the inverter uses. Inverters have an inbuilt smart charger that optimally charges the battery connected to it, hence essentially, what I did was connect my car battery in parallel to the inverter battery. Hence to the inverter, it only ‘sees’ 1 slightly discharged battery and charges it just enough to bring it up and then float charges it. This helps as I don’t have to monitor it continuously and hence sort of works as a smart charger with a float charger capability. I’ve used this to charge all my batteries and it has worked very well.

For the project, you’d need the following:

• Volt/Ammeter – I bought it from Amazon
• DPDT toggle switch
• 5mm wire as per length requirement
• Alligator clips
• Bana plus
• Fuse holder and fuse
• PVC box to house the components
• Wire casing for the wires from the inverter battery to the panel

The wiring is pretty simple and I’ve drawn it out for easier understanding.

Wiring Diagram:

Connection to inverter:

35AMP Fuse and panel:

Internal wiring:

Battery connected:

Finished product:

Thanks to HimuraKenshin again. Check out BHPian comments for more insights and information.