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Old 7th April 2017, 00:57   #1
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Default Charging car battery via home inverter

Either my Car wiring is having issues and draining my car battery, or my D.I.Y stuff is incorrectly working and draining the battery.

Recently my car won't start if I leave the car for 4-5 days, Existing battery is Amaron FLO in my santro, Its a 2 yr old battery.

Over a jolly mood on a weekend, I went to the parking and car won't start, my DIY voltmeter was showing 10.5 volts or so, killing my mood, and I needed to reach somewhere on time, skipped the car and took an OLA. Once I was back, removed the battery from car and carried it along to my apartment.

Had a hardly used Inverter at home, and quickly plugged it in, luckily I didn't needed to boost it, as these UPS based Inverters won't start charging if battery is below 10v or so. Within a few hours, Battery charging stopped, another voltmeter was showing full, approx 13v or so upon initial connection, but was coming to 12v range in a few minutes.

Installed the battery back and it started in half a crank.

A week later this battery was down to 7v (Certainly current leakage) and this time Inverter didn't start charging, I was worried, spent weekend again without driving, but this time I had a 12v 2Amp power supply as the only option. On Tuesday night I connected it to car battery, and left it connected for 24 hours, Battery is back to 12.5v, and on Wednesday night disconnected the charger as slow charging was complete.

Now its been more than 24 hours since battery is left disconnected, I am still getting 12.4v on it. I am sure battery still has juice left and only thing I need to take care of is to prevent my Arduino & GPS to stop draining the battery.

I do have an Amplifier in car, but it doesn't turn on until HU is turned on, I am sure this is what prevents the Amp from draining the battery, but will try keeping this disconnected for a few days to see hows the battery drain looks now.

Made a small video about charging via Inverter, Don't have video for 2Amp wall charger video, but will make if I needed to charge the battery again.


Last edited by GTO : 7th April 2017 at 12:03. Reason: Several language errors
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Old 7th April 2017, 09:08   #2
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Default re: Charging car battery via home inverter

Quote:
Originally Posted by ghpk View Post
Either my Car wiring is having issues and draining my car battery, or my D.I.Y stuff is incorrectly working and draining the battery.
You need to follow these steps:

a) Charge battery till charging stops, confirmed via an ammeter or a clamp meter. The charging current will be <0.5A
b) Disconnect the battery from the charger, measure the voltage at the posts. It will read 13-13.3V. Let the battery sit idle, without any connections, for about 12 hours to remove surface charge
c) Take another voltage reading. A fully charged battery will read about 12.66 - 12.7V depending on the accuracy of the meter you are using
d) A reading of 12.4 shows a battery at approx. 75% charge. This is NOT normal unless it has been connected to a load. I'd advise you to have the car tested for current leaks after which please have the battery tested for any internal shorts or damage.

Last edited by R2D2 : 7th April 2017 at 09:10. Reason: typo
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Old 7th April 2017, 09:15   #3
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Default re: Charging car battery via home inverter

Quote:
Originally Posted by ghpk View Post
Battery is back to 12.5v, and on Wednesday night disconnected the charger as slow charging was complete.

Now its been more than 24 hours since battery is left disconnected, I am still getting 12.4v on it.
12.4V seems to be low for a battery without any load. I assume wither the charging is not completed or the battery is reaching it's end of life.

PS: I used home UPS inverter to charge my car battery couple of times and during the vardah cyclone at Chennai I used the car alternator to charge the inverter battery.

EDIT: Just noticed the previous post better explanation. It wasn't there when I started typing my post.

Last edited by Mr.Boss : 7th April 2017 at 09:17.
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Old 7th April 2017, 11:30   #4
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Default re: Charging car battery via home inverter

R2D2: Thanks for excellent info.
As stated the battery in question is 2+ years old, with multiple DIY type experiments, I think its already in last phase of its life cycle.

I'll be installing it back into car tonight, and will report back with results tomorrow.

Mr.Boss: When Car is running during the day, I see charging volts from alternator to go till 14.5 volts. while when charging from home based inverter it was in 13.5v or so, and when used 12v 2Amp charger, the max charge voltage i noticed was 12.9v or so.

As said earlier, I'll install this tonight and update on findings tomorrow.
Thanks again for inputs.
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Old 7th April 2017, 15:18   #5
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Default Re: Charging car battery via home inverter

Why don't you just connect a multimeter in amp mode and measure current draw? That will tell you if there is something significant drawing current, to isolate this disconnect the accessories or DIY's, till you find the leak source.
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