Need help reading battery charger

[wavinwayne]

This picture was taken approx. 5 minutes after hooking the charger to the battery in my '00 GTI. I confess my ignorance in this area; Can one of you guys please look at the picture and tell me how to read the ammeter, and let me know how it should read if/when the battery is charged? Thanks in advance.

 

[Jim 5]

I had this charger. The numbers along the bottom tell you how many amps the battery is accepting from the charger. The needle is basically an ammeter.

There are 2 scales, one for the 2 amp rate (indicated by the small red triangle on the left) and one for the 10 amp rate (indicated by the 0-100% and starting at the "R" of "Rate" and ending at the far right).

If you are charging a low battery at the 2 amp rate, then the red/green triangle at the left applies to tell you how discharged (roughly) your battery is. If it is taking 2 amps at that rate, then your needle will be at the high end of the red triangle on the left showing that the battery is accepting all of the 2 amps being supplied by the 2 amp charger. This means you have a serviceable battery and it is really low. As the battery charges, it will start accepting less amps and the needle will move from the 2 amp rate towards the left showing a movement to 0 amps indicating a 100% charge

Same thing applies at the 10 amp rate, except in this case, the 0-100% scale applies. If the needle is pointing at the 25%/10 amp point, you have a good battery that is very discharged. As the battery charges, it will start accepting less amps and the needle will move towards the left showing a movement to 100% charge.

If you test your battery and you know it is very low and the charger indicates a very low amp flow nevertheless, you will know that your battery is not accepting a charge and you have a bad battery.

I had the manual version of this charger so I could tell whether it is on or not. Yours is automatic, so if it has detected that your battery is fully charged, presumably it would turn itself off and accordingly there would be no amp flow showing on the ammeter. I'm not sure how you would test this function. It looks like it is off. That could indicate a fully charged battery - with the automatic charger cut-out having been activated. I'm guessing on that one. If you think your battery is fully charged, I'd switch it to the 2 amp rate and leave it, given you have an automatic charger.

I hope this helps.

 

[wavinwayne]

Thanks Jim5.

 

[oilboy123]

I don't believe it kicks out when it's charged. I have a couple of little cube chargers that are automatic. I use them %99.9 of the time.
I normally use my bigger automatic charger when I need it on the lower setting because it's a little easier on the battery.
Having a voltmeter will let you see where the battery is in the charge cycle. But that's a whole other can of worms......

I would say be careful of leaving charging for too long.

 

[Jim 5]

Originally Posted By: wavinwayne
Thanks Jim5.


No problem. I like that GTI of yours. How many miles are on it now?

 

[wavinwayne]

Originally Posted By: Jim 5
Originally Posted By: wavinwayne
Thanks Jim5.


No problem. I like that GTI of yours. How many miles are on it now?


She's got 166k so far. Shooting for 250-300k, then I'm selling it, or I may send it to GTI heaven.

 

[Jim 5]

Originally Posted By: wavinwayne
Originally Posted By: Jim 5
Originally Posted By: wavinwayne
Thanks Jim5.


No problem. I like that GTI of yours. How many miles are on it now?


She's got 166k so far. Shooting for 250-300k, then I'm selling it, or I may send it to GTI heaven.


Great! Is it shooting coins out of the HVAC vent yet? (I guess you'd have to see the Auto Zone commercial I'm talking about).

 

[wrcsixeight]

Sometimes a 12v battery which is discharged below 10.5 volts will not take any amps. Automatic chargers will likely shut down.

The trick is to parallel a good battery to the below 10.5 volt battery, and hook them both to the charger. Then the bad battery will be able to accept amperage from the charger.

Any battery that has been brought below 10.5 volts has had a percentage of it's capacity removed forever. It depends on how below 10.5 volts and how long it remained there and the quality of the battery. But it can be fully recharged and be used for another year or 2 or more if recharged and treated properly after that.

 

[wavinwayne]

Originally Posted By: wrcsixeight
Sometimes a 12v battery which is discharged below 10.5 volts will not take any amps. Automatic chargers will likely shut down..


Bingo. That would explain why my charger was showing a full charge, while I knew from this car's history, that the battery was telling me it was on it's last leg. I ended up going to Autozone and having the battery tested. The battery was indeed bad. A new Duralast battery had me on my way. At least the old battery has some warranty remaining, so I didn't get stuck paying full price.

Also, I let the Autozone guy replace the battery, since they do it free of charge. No need for me to get my hands dirty if I don't have to.

 

[wavinwayne]

Originally Posted By: Jim 5
Originally Posted By: wavinwayne
Originally Posted By: Jim 5
Originally Posted By: wavinwayne
Thanks Jim5.


No problem. I like that GTI of yours. How many miles are on it now?


She's got 166k so far. Shooting for 250-300k, then I'm selling it, or I may send it to GTI heaven.


Great! Is it shooting coins out of the HVAC vent yet? (I guess you'd have to see the Auto Zone commercial I'm talking about).


I know the commercial well. I always chuckle to myself whenever it comes on. Little Red has been (figuratively) shooting coins back at me for years.