950 CCA diesel generator battery in my TDI ?

Hey guys,
I picked up a diesel generator 12v battery that needed to be replaced at work because there was a power cut and the battery voltage went down to ~3volts over a few days (we installed it last year so it's really only 1 year old) so I took it home and I'm charging it up tonight with a real 12v battery charger (reconditionner). I'm fairly confident the battery is still 100% in good shape.

That battery was installed in a CAT diesel generator in pair to provide 24v. The brand is Detroit Genuine Parts.

Here is the picture of the specs: https://i.imgur.com/UGdLpnH.jpg

That battery is quite heavier, and a little bigger than the one I have actually in my TDI, but it could fit. Do you think it's too powerful for my poor TDI ? Do I risk breaking anything if the starter is powered with too much amperage ?

The voltage is what matters... Your starter will only pull the amps it needs, not get hammered by what the battery is capable of delivering.

Hope the reconditioning works out for you. Might be worthwhile to get it load tested before installing it.

Good luck with it!

ffemtp said:

The voltage is what matters... Your starter will only pull the amps it needs, not get hammered by what the battery is capable of delivering.

Hope the reconditioning works out for you. Might be worthwhile to get it load tested before installing it.

Good luck with it!

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*remaining* amperage is what matters. Have it load tested and you'll know. Voltage won't tell you that.

That battery is capable of delivering a huge amount of amperage at cranking.

How can I load test it? All I have is a damned multimeter.

you need a special tester. chain stores typically can do it for you - in US AutoZone, Pep Boys, etc. It'll tell you how many amps the battery can put out

You can also do a poor man's load test with your meter. You fully charge the battery. Then set it up to test voltage. Then crank the engine for several seconds and see how low the voltage goes This has to be done with the ignition or fuel (in diesel's case) deactivated so it won't actually start. It should stay above 9.5 at all times. If it doesn't, that battery is toast and useless for the car. This is only a first pass test. The battery may still be very damaged and perhaps not last a full season.

We have and use 2 testers. first and quickest is the inductive tester, which is what the part store people will use. It will tell you state of charge, state of health, internal resistance, and CCA. They seem to be relatively accurate for the most part, as long as the battery is charged fairly well to begin with.

The next tester is the old fashioned "carbon pile " type. You can dial a load and put the battery on the treadmill so to speak. The rule of thumb is 1/3 battery cold cranking amps for 15 seconds. If the battery drops below 10 volts it is weak. Many strong batteries will go 30 seconds. Once tested it needs to be recharged because you depleted it quite a bit, but it is the most valid test of capability. We get by 99% of the time with the inductive testers, but once in a while we have to dust off the carbon pile. Smoke literally rolls out of it when testing if it has gotten dusty.

Can I purchase that kind of tester? Where can I buy one?

jorioux said:

Can I purchase that kind of tester? Where can I buy one?

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You'll need about a 500 amp one for your battery (to load your battery with about a 400 amp load).

https://www.amazon.com/s/ref=nb_sb_...efix=500+amp,automotive,139&crid=BAVU8ZXXJ5RE

Prices vary and I don't know how reliable the cheaper brands are.

The carbon pile testers are not cheap, though you may stumble onto one occasionally at pawn shops or the like.

The cheapie induction testers are readily available. I bought several of them to sprinkle around the shop, ideally at least one to a tech. I buy them on ebay. The best cheapest one I found was made by autool. If you watch the auctions and bid sparingly, you can pick one up for $30. shipped. They have been reliable and read very close to the Midtronics units we have .

Old guy method- Battery condition-
Clean it
Top off electrolytes
Full trickle charge
Measure the specific gravity in each of the 6 cells
Those numbers will tell you the relative condition of the battery

Battery Specific Gravity Test: Battery Hydrometer Test

BobnOH said:

Old guy method- Battery condition-
Clean it
Top off electrolytes
Full trickle charge
Measure the specific gravity in each of the 6 cells
Those numbers will tell you the relative condition of the battery

Battery Specific Gravity Test: Battery Hydrometer Test

Click to expand...

Take me back in time alright. Did that many times, but I think your steps are out of order. i would not add electrolyte till after charging because it could rise. if it was bone dry the battery is toast anyway.
Another step you omitted is battery cell voltage test, done cell by cell. Once in a while there was a reversed cell caught this way.

Today's testers do work pretty good and can be relied on mostly, but once in a while old school is called into play.

My personal view on batteries anymore after having battled many of them over the years is almost zero tolerance. If it has some age to it and starts giving trouble you are better replacing it and starting all over.

I have spent unpleasant hours in the freezing cold and on camping trips and other inopportune times to try to save a dollar milking the last minutes out of a battery. i would rather replace it 6 months too soon than one minute too late.

All true and correct, I always go for simple and it does work.
We see a lot of posts where battery shows 12, 14 when running and battery is declared good. In recent years I just take it in for load test.

BobnOH said:

All true and correct, I always go for simple and it does work.
We see a lot of posts where battery shows 12, 14 when running and battery is declared good. In recent years I just take it in for load test.

Click to expand...

Yup. I confirm it has electrolyte, trickle charge for 2 days, then load test. It is either good or less than good. Less than good = replace for me.

I can't be wondering how long a marginal battery will last and leave me stuck somewhere.

A starting battery that is fully depleted is almost always permanently damaged. That one was drained dead, dead, dead and at least one cell was almost-certainly reverse-charged, which is what destroys them.

"Deep cycle" batteries sometimes survive that sort of abuse. Sometimes.

The problem with "charge and load test" is that it will miss one of the bigger problems, which is a less-than-complete internal short. What happens when you reverse-charge a cell is that it tends to bridge -- if fully then the battery will never charge properly at all in that one cell is basically shorted, so a 12V battery (nominal) only charges five of the six cells in the string, and it will ALWAYS read low.

But the perverse sort of failure, and the one that WILL strand you, is the one that usually happens when you over-discharge a battery -- a partial, fairly high-resistance short in one or more cells. A battery with one may pass a short-term (e.g. cranking) load test; it will likely fail a carbon-pile test, but not the quick ones used by a parts store or the use of an inductive clamp. That's because the damaged cell(s) will charge, just not to 100% since a some amount of the energy is bled off by the short.

The problem is that those cell(s) are self-discharging immediately and always! So if you charge the battery and then let it sit overnight, THEN load test it, it'll fail. Likewise, put it in something, run it for a while, go park the car for a couple of days and..... oops.

I've only relied on the carbon-pile tester. Dial up the load and just wait for the battery to fail (95% of the time) lol.

Even though my old go-to method isn't scientific, if the output/metered voltage is low I always open the cells and physically look for "metal" to be floating on the top of the cell; this is done before any charging occurs. In my history if there is "metal" floating in the top of any cell, that cell is either dead or soon to be dead. I also use a multi meter to check the voltage cell-by-cell. Each cell should read at least 2 volts higher than the previous cell.

Flooded lead-acid batteries get PTSD when discharged that far. It *WAS* damaged. It may still be healthy enough to serve, but it was damaged.
cheers,
Douglas