Resting battery voltage high.

[White 03]

I was in a hurry and got one of those cheap china rebuilt alternators for my 91 civic along with a new battery. Next day after sitting overnight showed 12.3 volts and gravity showed around 1200. I took the trip and the voltage regulator in the alternator went out and the battery got overcharged. Boiled water down to somewhere below the plates.

Battery voltage showed 13+ volts after sitting all night. I filled battery with distilled water and charged it. I replaced alternator and this one is giving around 14 to 14.5 volts, a little less with full load.

After a two weeks of use battery still shows 13+ volts after sitting overnight or sitting for two days, even after leaving all lights on for 5 minutes. Gravity still shows low, around 1200. Car seems to start OK.

How come the voltage is staying so high?

I tried to reset the battery by leaving the lights on for a couple of hours until battery dead and recharging but battery still shows high. Three meters all show the same readings +/- .1volt.

 

[tinmanSC]

How long in between purchasing the battery/alternator and the voltage regulator failure was there? 1 day? 2 weeks? 4 years? You also said you took "the trip" what was "the trip?"

 

[wrcsixeight]

Strange behavior, if your digital multimeter taking readings at the battery terminals themselves is accurate. Do not trust dash gauges without corroboration.

The surface charge on some batteries can last longer than others, especially when new.

When the water level falls below the plates, fill with just enough distilled water to cover the plates, then recharge. Then add water to the proper level. If you add too much water the Specific gravity readings will be low even after agitated and fully recharged.

Most hydrometers are highly inaccurate, and are only good to compare readings to itself at a later date. The glass turkey baster style with the fragile glass floats are the best, as long as you get all the bubbles off the float.

 

[White 03]

Originally Posted By: tinmanSC
How long in between purchasing the battery/alternator and the voltage regulator failure was there? 1 day? 2 weeks? 4 years? You also said you took "the trip" what was "the trip?"


Sorry, trip was what caused me to be in a hurry and buy overseas rebuilt instead of local electric shop rebuild.

Alternator's regulator went out two days after buying while on trip. Alternators was warranteed with another one like it. Alternator seems to be working for now.

 

[White 03]

Originally Posted By: wrcsixeight
Strange behavior, if your digital multimeter taking readings at the battery terminals themselves is accurate. Do not trust dash gauges without corroboration.

The surface charge on some batteries can last longer than others, especially when new.

When the water level falls below the plates, fill with just enough distilled water to cover the plates, then recharge. Then add water to the proper level. If you add too much water the Specific gravity readings will be low even after agitated and fully recharged.

Most hydrometers are highly inaccurate, and are only good to compare readings to itself at a later date. The glass turkey baster style with the fragile glass floats are the best, as long as you get all the bubbles off the float.


Car only has light, which now comes on occasionally at random times; all readings are with digital volt meters.

I have tried to get rid of surface charge buy letting it set from 12 to 48 hours; same reading. Even turning lights on for 5 minutes voltage goes down to 12.0 then back up to 13+; this is with engine off no alternator.

Hydrometer is glass turkey baster with glass float. Not greatest but seems usefull when compared with other vehicles with good batteries. Hydormeter reading is before engine is started after sitting all night.

I still can't figure why voltage stays high.

Thanks.

 

[wrcsixeight]

I'd confirm with another Digital meter, and cut up an old ciggy plug device to hook to the DMM so you can see what is happening when driving and the light illuminates. Reading at idle only does not tell very much.

 

[3311]

It's fine and normal to have an open circuit voltage of 2.16 volts per cell(13/6 cells) But the specific gravity in your battery is low at 1.200, it should be 1.250 for a fully charged automotive.

 

[Donald]

Do a load test or a conductance test on the battery.

 

[White 03]

Originally Posted By: wrcsixeight
I'd confirm with another Digital meter, and cut up an old ciggy plug device to hook to the DMM so you can see what is happening when driving and the light illuminates. Reading at idle only does not tell very much.



Several digital volt meters all come within .1 volts of one another. I did hook up a meter to the battery and read volts while driving and that is when I discovered the high voltage with the prior alternator. Idle voltage and driving voltage seems to be normal around 14v to 14.5v with new alternator. I also have gotten a volt meter that plugs into the dash power plug so I watch it and try to trouble shoot it.

 

[White 03]

Originally Posted By: 3311
It's fine and normal to have an open circuit voltage of 2.16 volts per cell(13/6 cells) But the specific gravity in your battery is low at 1.200, it should be 1.250 for a fully charged automotive.



I thougt 12.6 was about as high as I have seen a new battery, most of mine start at 12.5 and go down over the years. This battery started life at 12.2 to 12.3 even after sitting on a slow charge over night. 13 volts seems to be a result of the over charging but I have never seen this before.

1.250 and even 1.280 is what I have been told is normal for a new battery. 1.200 combined with 13 volts seems odd. Could I have changed the specific gravity when I filled it with distilled water? It probably took a couple of cupfulls.

Thanks