Charging car battery, how high v is too high?

[TurnThePage]

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?

[MEXICOWANDERER]

To the OP (stirring the pot)...

What brand didja buy?

[azrving]

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

[RJsfishin]

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.

[Golden_HVAC]

Hi,

Yes if it is going up to 14 + volts shortly after applying the charger, then it indicates that once cell is shorted out. . .

Good thing to replace it and have reliability again.

Fred.

[TurnThePage]

Yup, it read 14.3V while idling.

This was my first regular starting battery that died a premature death without my helping it along.

[azrving]

When you put the new battery in, check the charging voltage. It should be around 13.7 to 14.2 ish

[TurnThePage]

I thought it pretty strange for a battery that was down to 8 volts, to be reading all the way up to 15.7 in only 15 minutes on a 10 amp charger. After disconnecting the charger and waiting a while, it started the car and still had a resting voltage of 12.7. I tried to start the car again and got the telltale clicking noise. Now the meter says 10.3 volts. Off to replace the battery. Thanks for the feedback!

[azrving]

MEXICOWANDERER wrote:
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

lol

[time2roll]

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

[MEXICOWANDERER]

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

[azrving]

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 MANUAL
AMERICANA & AMERICANA PLUS
RM 2351, RM 2354, RM 2451, RM 2454
RM 2551, RM 2554, RM 2652, RM 2662
RM 2663, RM2852, RM2862 & NDR1062

dc
Voltage
The operational range
of the unit is a minimum of 9.6V DC to a maximum of
22V DC. The unit will automatically shut down until volt
-
age has decreased to 18V DC.

[Dakota98]

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]

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.