Not specifically an RV issue, but... Our two year old car wouldn't start today. A quick check of the battery showed just over 8 volts. I connected a Harbor Freight 2/10/50 charger on the 10 amp setting. The multimeter immediately showed 14.3v and was at 15.7v 15 minutes later. I disconnected it, fearing it was climbing beyond what was safe. Thoughts?

Hi,When a battery exhibits that kind of behavior it is pretty much done.15.7 is definitely too high for an RV (fridge board is 15.4), but I know not about a car.

The charger is working correctly.The voltage you were reading was what the charger was putting into the battery to bring it back up to capacity. Once the battery gets near to 100% the charger will then switch to a trickle charge mode. I have a "smart" charger that starts out at about 13.2 volts & cycles in small increments up to 16.0 volts over the charging period, once the battery reaches capacity, the charger senses this & backs down voltage.

pianotuna wrote:Hi,When a battery exhibits that kind of behavior it is pretty much done.15.7 is definitely too high for an RV (fridge board is 15.4), but I know not about a car.It depends on the model of refrigerator. This is from Dometic DIAGNOSTIC SERVICE MANUALAMERICANA & AMERICANA PLUSRM 2351, RM 2354, RM 2451, RM 2454RM 2551, RM 2554, RM 2652, RM 2662RM 2663, RM2852, RM2862 & NDR1062dcVoltage The operational rangeof the unit is a minimum of 9.6V DC to a maximum of22V DC. The unit will automatically shut down until volt-age has decreased to 18V DC.

In as few words as possible finding a car battery at 8 volts is exactly like finding a human being with a body core temperature of 55

Charger is fine, 15.7v is fine, battery is shot.

Charging car battery, how high v is too high? | Good Sam Community

RJsfishin
Explorer
Sep 10, 2014
There are some that should get educated on hi voltages damaging electronics.
16+ volts is normal for most todays smart chargers. Even my Schumacher 1.5 amp maintainers go over 15 volts in the first stage. And I've seen 16.4 on my bigger Schumacher, on a new battery, when full charged.
And I believe my PD9245 goes well into 15 volts, but I'm never there when it does that "equalize" thing.
azrving
Explorer
Sep 10, 2014
RJsfishin wrote:
There are some that should get educated on hi voltages damaging electronics.
16+ volts is normal for most todays smart chargers. Even my Schumacher 1.5 amp maintainers go over 15 volts in the first stage. And I've seen 16.4 on my bigger Schumacher, on a new battery, when full charged.
And I believe my PD9245 goes well into 15 volts, but I'm never there when it does that "equalize" thing.

I have been told that my batteries will be junk in 6 months. :)
four 6 volts from 12.25 to full in 4 hr 10 min
MEXICOWANDERER
Explorer
Sep 10, 2014
To the OP (stirring the pot)...

What brand didja buy?

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Charging car battery, how high v is too high?

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