Charging a battery at 11.9v

[2010Civic]

How long are they on vacation for? That is an odd request in my opinion. Tell them to buy a battery maintainer and just let it go.

 

[dubber09]

Speaking of 11.9V... I just installed (on weekend) an Android head unit as a replacement to factory basic one, in wife's Forte. It gave me an option to display car battery voltage on screen, it was 11.9V while engine was off. Voltage went to 14.4V when car was running.
Relatively new battery, about 2 years old. I'm not concerned about the battery, bought it at Costco, it came with 4 years free replacement warranty, 100 months total warranty (prorated after 4 years).

 

[JHZR2]

Panasonic huh? Good batteries. Replaced one in our 94 previa after a decade with no issues just because.

Thing is, 11.9V isn’t good.

A dumb charger to get things going probably is the right move. But I’d limit charge rate and duration.

It will be sulfated, definitely should be remediated by a modern smart desulfating charger when possible.

 

[wavinwayne]

I wouldn't mess with my neighbors battery...

I hate to say it, but same here. If you do anything, you will be blamed for everything that goes wrong on the vehicle in the future. I learned that lesson from trying to help family in the past.

 

[JimPghPA]

That's good information, particularly about the output being directly proportional to line voltage (117 AC RMS in my house).

I suppose the next step up was to to put a Zener across the OP to clamp the voltage to c. 13.2 - 14.2 V.

Clamping with a zener isn't really a great way to try to limit the output of a power system.

 

[Number_35]

Clamping with a zener isn't really a great way to try to limit the output of a power system.

I guess it would have to be one capable of handling the excess current.

How does a modern charger regulate voltage?

 

[Rygrego]

I guess it would have to be one capable of handling the excess current.

How does a modern charger regulate voltage?

A modern charger will gradually charge with a tapering charge until fully charged at which time a good charger stops charging and switches to a float charge. A float charge will maintain by only adding a light charge when voltage drops below a specific level just a hair below full charge.

 

[Rand]

A full size battery is closer to 90 amp-hours, not 50.

45-65AH ? or are you talking semi battery
USING RC of 150 which isnt perfect suggests 63AH for my old battery which was a fairly hefty h7

 

[eljefino]

45-65AH ? or are you talking semi battery
USING RC of 150 which isnt perfect suggests 63AH for my old battery which was a fairly hefty h7

This deep cycle group 24 battery boasts 101 amp hours. Maybe reserve capacity only depletes a battery to a point where it still works, eg starts the car again.

 

[proveitwithdata]

just to close out this thread, I told the neighbor i dont want to mess with the battery, so im gonna leave it uncharged. He will deal with this on his own when he gets back.

thanks everyone