Can a battery be tested while flat?

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Renault4

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Have just been speaking to the garage which diagnosed a "cooked" battery along with a failed alternator on my daughters car.

After they replaced those two items, I got the old battery back: it was at 8V, but took a good charge and is still well above 13V a few days later.

The garage said they had tested the battery while flat and found it needed to be replaced.

Is there really such a battery tester? - ie one which can test a totally flat battery?
 
Very simply.

If you accept a battery is a box of power.

All it does (Not really true but OK for this explanation), is hold the power and deliver it as needed.

You therefore can't test it (properly) if its empty.

It should be recently charged, and then stood for hour or 2 before any test. Very rarely this is done though.

But if a faulty alternator has "cooked " it, it likely has signs of bulging, or low acid etc and could well be beyond saving.

Holding 13v is unusual ,(12.6 would be around normal), its how much power it can deliver under load that matters. Worth getting it tested now it's charged
 
As above!
Charge the battery up and whisk it along to a motor factor who will put a heavy discharge meter across it's terminals, and take a reading.
In days of yore you could see a faulty cell bubbling through the open filling caps.
An alternative is to pop the charged battery on a car, and measure the cranking voltage as you try to start it.......anything much less than 11v means it's goosed.
John :)
 
carmanmemoranda said:
Very simply.

If you accept a battery is a box of power.

All it does (Not really true but OK for this explanation), is hold the power and deliver it as needed.

You therefore can't test it (properly) if its empty.

It should be recently charged, and then stood for hour or 2 before any test. Very rarely this is done though.

But if a faulty alternator has "cooked " it, it likely has signs of bulging, or low acid etc and could well be beyond saving.

Holding 13v is unusual ,(12.6 would be around normal), its how much power it can deliver under load that matters. Worth getting it tested now it's charged
Click to expand...
The battery has obviously not been "cooked" as it takes a full charge and holds a good voltage, so that info was fake.
The reason for my question is that I'd like to know if the claim that it can be tested and condemned while flat is also fake.
12.6V is the threshold below which a 12v lead acid battery should be charged. It should be well above that for a good while after charging (unless under load).
 
Renault4 said:
The battery has obviously not been "cooked" as it takes a full charge and holds a good voltage, so that info was fake.
The reason for my question is that I'd like to know if the claim that it can be tested and condemned while flat is also fake.
12.6V is the threshold below which a 12v lead acid battery should be charged. It should be well above that for a good while after charging (unless under load).
Click to expand...
12.4 is typical minimum voltage.

12.6 is typical good healthy voltage

12.8 is very good battery voltage (not many used batteries will achieve this)

But voltage isn't the only criteria. Its how it performs under load that matters

Get it tested now it's charged for the real answer.

Just because it takes a charge doesn't mean its still good.

But it shouldn't have been tested when flat
 
carmanmemoranda said:
12.4 is typical minimum voltage.

12.6 is typical good healthy voltage

12.8 is very good battery voltage (not many used batteries will achieve this)

But voltage isn't the only criteria. Its how it performs under load that matters

Get it tested now it's charged for the real answer.

Just because it takes a charge doesn't mean its still good.

But it shouldn't have been tested when flat
Click to expand...
Best I can currently do in the way of testing under load, gave the following results:
93 Amps for 55 seconds during which voltage decreased to 11.77
then increasing load to 134A for 19 seconds during which voltage declined to 11.41V
and 50s after switching off load, voltage had risen to 13.0V

How does that sound?
 
Burnerman said:
Sounds like a pretty good battery to me.....how are you measuring the high discharge?
John :)
Click to expand...
This.

I'm still a bit surprised it is "recovering" to 13.0 volts.

Other than that it sounds OK, subject to how it's being tested
 
Burnerman said:
Sounds like a pretty good battery to me.....how are you measuring the high discharge?
John :)
Click to expand...
Load was an inverter powering a 230V electric heater.
The discharge current was measured using a clamp meter on one of the cables between battery and inverter.
It has the figure of 540 on it - presumable CCA, so test load should have been a lot higher, but I suspect that result shows it is still usable.

It was the cheapest battery we could find, just over a year ago - a "DriveTec Heavy Duty". It looks like the alternator failure left it either shorted or under permanent load for a few days (recovery guy said it was at 0V), then it got taken out but not charged, by the garage. It was reading 8V when I got it. So it must have been totally flat for 15 days.
 
Why not take it to a motor factor, shop or another garage and get it tested. They will be able to give you a definite condition to work from.

Could then go back to original garage if you wanted, then, with specific facts.
 
carmanmemoranda said:
Why not take it to a motor factor, shop or another garage and get it tested. They will be able to give you a definite condition to work from.

Could then go back to original garage if you wanted, then, with specific facts.
Click to expand...

Logistics is one reason
 
carmanmemoranda said:
This.

I'm still a bit surprised it is "recovering" to 13.0 volts.

Other than that it sounds OK, subject to how it's being tested
Click to expand...

CALCIUM BATTERY!!!

There is nothing on the battery that says calcium.

But having looked that battery up, I now wonder if the garage have actually been sort of right to replace it:

When I put the car reg into the GSF website, it comes up with that DriveTec battery as the cheapest option and doesn't say anything about it being a calcium battery.
But,
when I put that battery model into duckduckgo, it comes up with a GSF listing for that battery which includes the line "calcium technology".

I read that they are not necessarily interchangeable with normal lead acid batteries as they require a higher charging voltage.
I've never used a fancy battery tester but is it possible that the garage scanned the flat battery with tester which has a database of batteries and came up with a REPLACE BATTERY message?
 
The Plot Thickens!

(Please tell me if I'm going off on a tangent)

The expensive replacement battery fitted by the garage was also a calcium technology battery, so would their fancy tester have also told them to replace it I wonder?

Elsewhere I read :

"An ordinary lead-acid battery will require between 12.96 volts and 14.1 volts of charge current to be fully charged. However, a lead-calcium battery will require a charging voltage of not less than 14.8 volts.

The high charge voltage needed means that it is impossible to trickle charge a lead-calcium battery.

When the lead-calcium battery is being used in the car it means the alternator has to continuously run to keep the battery fully charged."

Could that have been a factor in the early failure of the alternator? Is it another reason to go back to the garage and return the new battery?
 
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