[HimuraKenshin]

I happen to have 4 cars, namely a Fiat linea MJD, Swift 1.3 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 has 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 a rent over charging. This particular rudimentary charger of mine also went kaput a few months ago.
Hence I devised this easy contraption that one can add to thein exiting 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 invert, 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 s 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:
1. Volt/ Ammeter – I bought it from amazon https://www.amazon.in/gp/product/B07...?ie=UTF8&psc=1
2. DPDT toggle switch https://www.amazon.in/gp/product/B08...?ie=UTF8&psc=1
3. 5MM wire as per length requirement
4. Alligator clips
5. Bana plus
6. Fuse holder and fuse
7. PVC box to house the components
8. 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




you can also watch this video if you want to see some more details:

https://youtu.be/1n_k_IXvL2s

[Turbanator]

Nice setup. But you need to take care of your batteries. Use some hot water to clean the terminals and apply some Vaseline.

[Indian2003]

Originally Posted by HimuraKenshin

To counter this in the past, I have has 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 a rent over charging. This particular rudimentary charger of mine also went kaput a few months ago.
Hence I devised this easy contraption that one can add to thein exiting inverter battery circuit to help charge the automotive batteries through the same smart charger that the inverter uses.

I see the charger giving 12,9 volta and 0.1A. Will that be enough to maintain a 12V battery? I have never tried charging with such a low current.
My charger puts out 14,4V and 15A at maximum. It drops down as the battery charges.
The smallest cargers charge at 4A.

[HimuraKenshin]

Originally Posted by Indian2003

I see the charger giving 12,9 volta and 0.1A. Will that be enough to maintain a 12V battery? I have never tried charging with such a low current.
My charger puts out 14,4V and 15A at maximum. It drops down as the battery charges.
The smallest cargers charge at 4A.

The pic was taken when the battery was charged for 27 hours.. if you see the video, when i initially connected it, it was charging at 2.4 Amps...
For a completely discharged battery I've seen upto 6amps

Screenshot is attached

[Holyghost]

Originally Posted by Indian2003

I see the charger giving 12,9 volta and 0.1A. Will that be enough to maintain a 12V battery? I have never tried charging with such a low current.
My charger puts out 14,4V and 15A at maximum. It drops down as the battery charges.
The smallest cargers charge at 4A.

I guess since he is parallelling with the other batteries, a part of charging current will be taken care by other batteries. As he mentioned, the inverter will only see a slightly discharged battery and it float charges it instead of charging to 14.5v at full current.

[Aravind_M92]

Was just pondering about this two days back. Had left my car unused for about 50 days. Came home to a dead battery. Was exploring options if home inverter could be used for charging a car battery. Gave up and called a battery service centre and got it charged from him. Thanks for the detailed set up explanation!