Battery Load Test vs. Specific Gravity Readings

C

Colonel Biggs

Senior Member
I installed a new Interstate 6v battery (#1-VHD; 640 cca). It fired up the engine the first few times without a problem. Now, it is barely turning the engine over.

I removed the starter and used jumper cables to test the starter. The starter shaft spun, but at a low rpm, which was too slow to pull in the Bendix. I ran the same test, using a 12v battery, and the starter spun nicely and pulled the Bendix in.

The specific gravity readings for each of the three cells was 1.275, which should be the case for a new battery. Could the battery still fail a load test, or do the specific gravity readings rule that out?

I had cleaned all of the battery grounds, and I have an additional ground strap installed to a bolt on top of the cover for the u-joint housing. Are there any other tests I should run before returning to Interstate? I have tested the starter for shorts, but could find none, and the brushes were recently replaced. I am assuming that if there was a brush failure, the starter would not have spun with force on the 12v battery.

Gordon
 
What's the date code on the battery?
That would be a letter and number to tell when the battery was made, not when it was sold.

How long did the engine run after each start? Was it long enough to recharge the battery?
I like to put my 6 amp battery charger on a new battery as soon as I get the battery home.
It may have been on the shelf a long time without a charge.
 
Hey, Tom --

I have thought about shelf life. I have always used a 6v battery tender, which assisted in making my previous AC Delco battery make it to 6 1/2 years of service. When it turned "green," I had the car out on the road for about 30 minutes.

The tender also read "green" last night - just prior to the current fiasco. I had been traveling during the week prior, but the battery had been on the tender.
The engine cranked for about 20-30 seconds in total before quitting altogether. I put the battery on the tender overnight; it was green this morning. The starter spun (at a slow rpm) this morning, but it appeared sluggish.

There is a small "K15" (November 2015?) sticker on the side of the battery. It's a "stuck on" affair; not part of the battery label on the top.
 
So that battery has sat for almost 6 months.... My interstate supplier rotates my stock out every 6 months... It is also stamped / melted into the battery case if you look near the top on the side. Is your car charging at the proper rate?
 
No stampings on the side. There is a serial number on the label, which I am sure that Interstate could use to determine the date of manufacture.

I have always set my generators to charge at an 8 amp rate; I am told by electrical engineers that the 10-amp rate commonly talked about/referenced is overkill for a 6v battery, and can lead to overcharging. Regardless, a 30-minute drive and use of a battery tender should be sufficient to generate enough charge to turn over an engine. (Of course, if the tender is faulty...might have to try a standard charger to see how long it takes to get to fully charged.)
 
I consider 8 amps as too high a charge for daytime driving of 30 minutes. A rate of 3 or 4 amps would have been enough to recharge the battery. I would put the battery on a 3 to 6 amp charger for 4 to 6 hours, then load test it.
 
Placed the battery on the charger's 2-amp charge mode. It was up to fully charged in well less than ten minutes. Used cables to jump the starter. No change -- slow spin and no action from the Bendix. I would imagine that the load test will corroborate this.

Tom, you are correct. 8 amps is more than sufficient for only 30 minutes of driving. My point was that even with the combination of limited driving and use of the battery tender, it still should have been sufficient to spin the starter, using a new battery. In other words, it wasn't undercharged to begin with. I'm interested to see what Interstate comes up with in terms of a load test.

Question: is it possible for an armature to fail to deliver sufficient power, because of age, for example? Even if there are no shorts, can a commutator that was ground/turned years ago slowly fail, because of brush wear? I'm trying to think ahead - in case Interstate says that the load test is successful.
 
Colonel Biggs said:
Placed the battery on the charger's 2-amp charge mode. It was up to fully charged in well less than ten minutes. Used cables to jump the starter. No change -- slow spin and no action from the Bendix. I would imagine that the load test will corroborate this.

Is the battery installed in the car or is it out of the car and you are using
jumper cables to try to start it??

Bob
Click to expand...
 
Colonel

As a quick test, if you have a volt meter you can use your starter motor as a load test. Measure the voltage across the battery while you are cranking the starter motor with the ignition off.
If the voltage drops by about 2 volts the battery may have a dead cell.

Jeff
 
FYI-Battery load testers are quite reasonable on the internet. Start with a freshly charged battery, then load test it for 10 seconds. You will probably have to recharge the battery for a short time after you load test it because it puts quite a draw on the battery.
 
[IDo you have another 6 volt battery available that you can attempt to start the car with. Maybe a friends Model A. That way you can isolate the problem as either battery or starting system.. Wayne[/I]
 
I have both the battery and starter out of the car. I tested the starter on a 12v battery, and it spun fine. I removed the starter to look for shorts. Used jumper cables between the two to spin the starter, thinking that maybe the battery ground in the car was a potential problem.

I have a load tester, but it's up in NJ, which doesn't do me much good down here in Texas. Because of the specific gravity readings, I'm going to guess that the cells might be okay. However, my knowledge of battery electronics is not sufficient enough for me to describe why a load test could fail, even if the specific gravity readings are okay. If the load test is okay, then there is something going on with the starter to prevent it from generating sufficient output. Since the brushes are new, and I haven't found any shorts, it would have to have something to do with the armature, or the field coils.

Since the battery is new, I will be taking it in to Interstate in the morning for a load test. I will report back on the results.
 
Jeff in BC said:
Colonel

As a quick test, if you have a volt meter you can use your starter motor as a load test. Measure the voltage across the battery while you are cranking the starter motor with the ignition off.
If the voltage drops by about 2 volts the battery may have a dead cell.

Jeff
Click to expand...

If the starter was dragging, wouldn't the voltage drop as well?
 
The battery cables for the "A" are #1 gauge, if I recall correctly. I use #2 gauge jumper cables for my 12v batteries. Without the flywheel load they are usually sufficient for testing the starter's spin when it is off the car.

If the starter is "shot," as someone suggested, the question becomes one of diagnosis. Field coils don't contain any movable parts, so unless the covers are exposing the windings to possible shorting situations, I would think that they would be okay. However, my technical knowledge of what constitutes a serviceable armature is on the light side. But, $100 for a new one is cheaper than a rebullt starter. Bratton's describes their rebuilds as using original field coils and armatures that have been "tested" (whatever that means!).

Many thanks for all of the responses in this mess!
 
Colonel Biggs said:
Question: is it possible for an armature to fail to deliver sufficient power, because of age, for example? Even if there are no shorts, can a commutator that was ground/turned years ago slowly fail, because of brush wear? I'm trying to think ahead - in case Interstate says that the load test is successful.
Click to expand...

Any part can fail. Brushes can wear down, the commutator can wear down, You said it your self "...was ground/turned years ago...". The coating on the windings can break down due to age and things like overheating.

There are a couple of Starter rebuilders in the houston area. If the battery tests good I would take the starter to one of the professionals.
 
Colonel Biggs said:
The specific gravity readings for each of the three cells was 1.275, which should be the case for a new battery. Could the battery still fail a load test, or do the specific gravity readings rule that out?

Gordon
Click to expand...

Back to your original question, no a specific gravity test does not prove that a battery is in good working order. It can prove a battery is bad, but a combination of both specific gravity and load test is the best way to see if the battery is performing properly.
 
You must log in or register to reply here.
Back
Top