Battery/Charging issues...still...

zhenya · Post by **zhenya** » 03 Dec 2010, 10:49

Thanks Jerry.

I charged the battery overnight, and was surprised to see that it is topping out at 12.4v. I took your advice and went and bought a battery hydrometer, and all cells are measuring way low at between 1.2 and 1.175 specific gravity. The battery is toast, even though it is only a year old (replaced under warranty - last one only lasted a year as well).

I think I'm coming around to what is going on...Basically, between the somewhat higher than normal parasitic drain from the fusebox and relays, and the additional drain from the bad diode in the alt, plus the fact that I often have to park the car for 7-30 days at a time, the batteries must be going bad from the somewhat regular deep discharge cycles. Hopefully if I replace the battery and alternator, and am vigilant about disconnecting the battery when out of town or using my solar charger, I can extend the life of the next battery a bit.

Sound plausible?

Retired MVS Contributor · Post by **Retired MVS Contributor** » 04 Dec 2010, 07:29

It is most likely toast, but there are 2 important factors to be considered...One is the temperature at which the hydrometer reading was taken and the other is the length of time the battery was charged...

Hydrometer readings are correct only at 80 degrees F...The specific gravity would be 1.280 for a fully charged battery at 80 degrees...For an acid temperature of 20 degrees, 1.226 specific gravity would be a fully charged battery...The instructions for use of the hydrometer (which should have come with it) will tell you how to make the simple conversion...Some hydrometers have a built in thermomter...Mine does, but it is over 50 years old...

You have a very wide difference in cell hydrometer readings which is not good, but yet, is not conclusive...Overnight (12 hours) is not enough time to charge a dead battery with a run-of-the-mill Sears taper charger...You need at least 24 hours before it is time to condemn the battery...The reason is that the charge rate will be very heavy at first, but as the battery starts to "come up", the rate of charge will taper 'way off and it will take a lot of time to gain the last few hundred millivolts...I hope that the battery was disconnected when you charged, if not, the abnormal parasitic drain your car has will eat up a lot of the final charge...

Jerry

zhenya · Post by **zhenya** » 04 Dec 2010, 08:37

Hydrometer readings were taken at 30F, and it does say it is temperature corrected. I will charge the battery, disconnected this time, for 24 hours and check it again. Thanks!

Retired MVS Contributor · Post by **Retired MVS Contributor** » 04 Dec 2010, 10:46

zhenya wrote:Hydrometer readings were taken at 30F, and it does say it is temperature corrected. I will charge the battery, disconnected this time, for 24 hours and check it again. Thanks!

I am a little confused, zhenya...You said it is temperature corrected...There is no way that I know of that this can be done, it defies the laws of physics...UNLESS!!!..the float has several printed charts on it for the various temperatures you will encounter...I kind of doubt that because there would not be enough room and the print would be microscopic...Please explain..

Is this hydrometer the conventional "looks like a big hypodermic" type, or is it one of those newer semi-circular and unreliable types with the pivoting float?...That type is notoriously erratic and unreliable because the "float" device tends to cling to the walls of the window and give erroneous readings...OK for ball-park, not so good for balls and strikes...

Jerry

zhenya · Post by **zhenya** » 04 Dec 2010, 14:23

Yes, one of the cheap kinds, although it says clearly on it 'temperature compensated' and 'good for testing batteries warm and cold.' Could they not make the response of the needle relative to the temperature of the device?

Anyhow, all 6 of the cells on my battery were clearly down in the 'recharge' section of the chart. I also checked another battery that has been on a trickle charger, and it clearly measured good, so while the readings may not be all that precise, it looks like they are generally accurate. In any case, I've brought the battery indoors, and will charge it for 24 hours, then check both voltage and specific gravity again at room temperature.

Retired MVS Contributor · Post by **Retired MVS Contributor** » 04 Dec 2010, 15:18

Good enough zhenya...You mentioned a trickle charger you had another battery on...You were not attempting to recharge the battery in question with the trickle charger were you?...A trickle charger will only maintain a battery at it's present state of charge, it will not boost it up to full charge...I assume you knew that, at least I HOPE you did...

Jerry

zhenya · Post by **zhenya** » 04 Dec 2010, 16:17

No, different charger.

main battery is charging on my 10 amp charger.

zhenya · Post by **zhenya** » 05 Dec 2010, 12:20

Ok, battery charged indoors for almost 24 hours. After taking it off the charger, it reads 12.68v, but the hydrometer readings are essentially the same at 1.2, with 1 cell ever so slightly less than the others. I ran a couple of errands with the car, and after 4 starts, the voltage is down to 12.28. So looks like the battery is, in fact, bad. Glad it's still under warranty!

zhenya · Post by **zhenya** » 07 Dec 2010, 14:01

Ok, finally got the alternator changed and...my current draw is now under 30mA! Hopefully I can now close this chapter. Thank you all for all your help.

Retired MVS Contributor · Post by **Retired MVS Contributor** » 07 Dec 2010, 14:07

Great news...The alternator did indeed have a bad diode...Rather rare, but not unheard of...Good luck...

Jerry

Battery/Charging issues...still...

Re: Battery/Charging issues...still...