Is testing the remaining capacity of a battery really possible?

[Fordulike]

I, like many others, would love a gadget that could be fitted inline to the battery to show remaining gogo juice.

The method I used before, was to rely on a Cycle Analyst to show how much juice I had already used, from a known starting capacity.
Obviously this isn't ideal, as you need to have a fully charged battery in the first place, to reliably calculate the figure.
Plus, as the battery gets older, the start capacity drops, making the calculation less and less reliable as the battery ages.

Has technology conquered the problem of testing remaining capacity in a battery, or is this just a rehashed multimeter?

Battery capacity LCD Tester 12V-48v

If it is now possible to show a percentage remaining figure in a battery, then I'll be over the moon, but I'm not gonna hold my breath.

 

[trex]

it may just as well be a modified volt meter, extrapolating voltage vs state of charge, between low and high.

 

[SteveRuss]

The guy at 50Cycles (Kalkhoff shop) rigged my 17ah battery up to their engineer's electronics box yesterday and it showed the battery as a 17ah battery that thinks it has a total capacity of just over 12ah and was showing the remaining contents at around 6ah. I took it in as the performance of the battery has dropped this past seven days. Could have a problem me thinks.

So. It's possible. It's possible with car batteries as you will have noticed when you get those tested. How accurate they are I don't know but.

For £4.99, I would be interested to know how accurate that linked device is though.

 

[VictoryV]

The guy at 50Cycles (Kalkhoff shop) rigged my 17ah battery up to their engineer's electronics box yesterday and it showed the battery as a 17ah battery that thinks it has a total capacity of just over 12ah and was showing the remaining contents at around 6ah. I took it in as the performance of the battery has dropped this past seven days. Could have a problem me thinks.

So. It's possible. It's possible with car batteries as you will have noticed when you get those tested. How accurate they are I don't know but.

For £4.99, I would be interested to know how accurate that linked device is though.

Usually the car battery tester as used by garages and battery depots in my experience is a little different. They apply very strong electrodes across the battery - virtually a short circuit, and then check for the voltage and any excessive gassing in each cell to see if it is in the process of failing to take the load. So it is an extreme short circuit high current load test.

 

[SteveRuss]

Usually the car battery tester as used by garages and battery depots in my experience is a little different. They apply very strong electrodes across the battery - virtually a short circuit, and then check for the voltage and any excessive gassing in each cell to see if it is in the process of failing to take the load. So it is an extreme short circuit high current load test.

Ah. I was going to look that up as my knowledge of this stuff just extends to the capacitor test I have on my Fluke multimeter.

Cheers for that!

 

[flecc]

Usually the car battery tester as used by garages and battery depots in my experience is a little different. They apply very strong electrodes across the battery - virtually a short circuit, and then check for the voltage and any excessive gassing in each cell to see if it is in the process of failing to take the load. So it is an extreme short circuit high current load test.

That's called a heavy discharge tester, they've been in use for decades to test for failing cells. I used to use them in the trade, but they don't give a measure of capacity or content, just cell fitness.
.

 

[SteveRuss]

That's called a heavy discharge tester, they've been in use for decades to test for failing cells. I used to use them in the trade, but they don't give a measure of capacity or content, just cell fitness.
.

Two years ago, my 7 year old Audi's battery died whilst I was away. I got stuck having to go to Halfords. The guy actually showed me the read out of how much capacity his machine thought was left in what turned out to be the original battery. I think it was a smidgen over 150amps I think. I suppose their machines must be a little bit more technically minded than the tester you mentioned.

 

[Gubbins]

Is it possible to fit something in line that measures how much electricity goes in, and then how much comes out during use?

 

[Deleted member 4366]

Yes. It's called a wattmeter. £8 from Ebay.

 

[flecc]

I suppose their machines must be a little bit more technically minded than the tester you mentioned.

That's obviously something different Steve, but what VictoryV described accurately fits what a heavy discharge tester is. That simply produces a near short circuit across the cell terminals to check for instant voltage collapse as he described.

Once commonplace, the advent of sealed lead acid batteries with cell terminations buried has made them largely redundant in the motor trade now, but they still have applications elsewhere.
.

 

[mike killay]

What's the betting that certain motor accessory shops have got impressive looking devices that always read 'Dead Battery' even on brand new ones?

 

[Deleted member 4366]

The RAC were caught using them by Watchdog several years ago. They had put their guys on a bonus for selling stuff, and when they didn't sell enough, they got called in for a discussion wiyh their boss. They've stopped that now.

 

[Cyclezee]

We have equipment for testing battery capacity and various parameters, it also generates a report, but it cost considerably more than a fiver and most of the batteries we test with it.

 

[Gubbins]

My last car had a battery failure at just under 1 year old. I have seen the old way of testing with a bar thingy across the terminals in the past but this time they connected it to a machine which gave out a comprehensive report.. Obviously things have moved on...

 

[Deleted member 4366]

People will believe anything, especially if it's printed out by a computer.

 

[Croxden]

Depends, Is it on Wikipidea?