Battery tester

[Rykard]

Hi,
can someone recommend a battery tester? We have one we got from aldi or lidl (i think) but it doesn't seem to be giving consistent results .. we tested some yesterday as a smoke alarm was bleeping - all tested full, now it's bleeping again...

it would need to cover all sizes

thanks for the help

 

[G2EWS]

Hi Rich,

Invest in a low cost multi meter from Maplins.

Better than a battery tester and more useful as you can check fuses, mains power, car batteries etc.

Regards

Chris

 

[compo]

Unless your battery tester puts some load onto the battery when it measures it the battery could read full. As soon as you refit the battery the load pulls it down again. A multimeter would do the same thing.

 

[G2EWS]

Hi Compo,

Whilst what you say is true, a multimeter will give you an accurate voltage reading on the battery. Once it drops below it's optimum value then you can be sure without measuring current that it is on the way out.

A suitable and easy guideline would be for example a typical 1.5V battery will give you approximately 1.6 - 1.7V when new. Should it be reading 1.4V or less and you can physically see the voltage dropping then it has not got enough power to drive anything other than the lowest of current drain devices.

You can only work with guidelines on this type of test. I could go in to how to test by measuring the current drain or indeed the total available current within a battery, but this would not be suitable and could lead to serious damage should someone take the information and use it for example on a car or leisure battery.

The above example which can be used with any kind of battery and a modicum of common sense is good enough for most, if not all household situations.

Best regards

Chris

 

[Davidc]

If you use a multimeter you need to check what short circuit current the battery can produce for 5 seconds, and you'll have to gain experience over what to look for, and be careful which batteries you check that way. I used to do hundreds. Sorry G2EWS, but measuring voltage is no use at all as nearly exhausted batteries can give full voltage readings after a couple of hours rest and depolarisation into a meter which only takes nanoAmps from them. Where I worked we went over to an an-load voltage system once alkaline D cells arrived which could produce 15A+ SC current started blowing meter fuses. Even more current can be produced by rechargeables of various sorts.

Better to use a half decent tester which puts on a test load appropriate to the size and type of battery and measures the on load voltage. I have 2 which get frequent use.

This one has a meter of a type which takes a significant current to work it. I have one indoors in the cupboard where we keep spare remote control and smoke detector batteries. (Mine came from Maplin about 20 years ago as a free gift with an order. Simple, crude, and useful. Wife friendly).

This one needs an internal battery. I have one in the garage which gets used for the batteries in my bike lights and theft alarms, torches, and so on. Again it draws a small current from the battery being tested. It works well for both alkaline and NiMH batteries. The rechargeables only go a small way into the good bit of the display when charged, but the middle of the next bit is the end point for both alkaline and rechargeables. (I've had mine for years and it has just worked. Don't think it's ever had a new battery either).

 

[compo]

For most people it is even easier to try a new battery.

Simples

 

[Davidc]

For most people it is even easier to try a new battery.

Simples

OK if you don't use many of them, or if you're happy to just put new ones in and throw away the part used ones before a ride. Also OK if you're happy to throw away 4 batteries when one is dead and the other 3 have 4/5 of their energy left.

Fine if you're rich!

 

[compo]

The OP was referring to a battery in a smoke alarm. For anyone unsure about reliably testing batteries a new battery would be much safer in such an important application.

 

[Davidc]

The OP was referring to a battery in a smoke alarm. For anyone unsure about reliably testing batteries a new battery would be much safer in such an important application.

Absolutely. Those, and the same type in my CO alarm in the kitchen, get changed every New Year. Don't care about cost with those - they need to work 100% of the time.

The question asked about testing so I replied to that. In the circumstances a decent tester helps decide whether the problem is with the detector or battery. Again my view is that with smoke and CO detectors they get replaced if there's even a slight question mark over their condition.

(Not as important, but I change all the batteries in my clocks every year when they go back in October too.)

 

[G2EWS]

Hi David,

Of course as I have said, if you want to do the job properly a basic test is not good enough. But for the average person at home my suggestion works very well and is almost foolproof.

A 'revitalised' dead battery will start to loose it's voltage as soon as you apply a multimeter to test it. A battery with most of it's 'life' left in it will not. You appear to know what you are talking about so I am sure you will agree with this. Remember this is not a thorough test, but a simple one for the average person.

Forgive me if you have read it before but I am an electronics engineer in the communcations industry with my own company supplying the UK water industry. We have solar and battery powered radio sites all over the country and a Water engineer or technician cannot go onto a site in the middle of the night and waste time carrying out what you and I would call a 'proper' test. The idea is to get a quick understanding of what is happening and move on. Exactly the same really for an average person who has no need to understand too much technically when it comes to a battery in their torch/remote control/smoke detector etc.

Best regards

Chris

 

[Davidc]

A 'revitalised' dead battery will start to loose it's voltage as soon as you apply a multimeter to test it. A battery with most of it's 'life' left in it will not.

No I don't agree, you're wrong.

A multimeter from anytime in the past 15 years will likely have an input current when measuring voltage of the order of nanoAmps. (Input resistance upwards of 100 megohms on a 2v range). This is not sufficient to make the terminal voltage drop noticeably for at least minutes. An older cheap multimeter will act faster but the resolution of an analogue moving coil device is lower too.

The way batteries behave is a combination of simple physics and chemistry, and if you don't draw any current from a not quite totally dead one (nanoAmps is effectively none) it will have the same voltage as a brand new one. It's when you draw current there's a difference in behaviour, which is why a properly thought out tester will work and a high impedance digital multimeter won't.

I don't doubt you have experience with batteries, but you're not the only one. A boring but necessary item. I can only think you use some form of voltmeter to measure the things which draws a significant current. I had a voltmeter in the garage (until I dropped it and broke it) which my grandfather gave me. Read up to 9v. A hot wire type which had a resistance of about 1 kohm. I'd used it for years to do exactly what you describe - judging the state of batteries by how fast the reading fell.

I've just tried an AAA "Sunrise" branded battery out of the box we have for batteries for recycling. Using a 1990ish Maplin multimeter. It read 1.667v out of the box. Current into the 2mA range read 0.003, dropped away fast to 0.000. Back on 2v, first reading 0.004 and rising very slowly. Presumably it'll be back to full open circuit voltage sometime next week. OK, a one-off but what I'd expect. For comparison a brand new AAA Duracell measures 1.705v, 9.54A on the 20A range for a second, 1.705v by the time I switched the meter back.

(I'm not suggesting my old multimeter is accurate to anything like its precision by the way, but it's typical of an uncalibrated device of its type.)

 

[G2EWS]

Hi David,

Not wishing to make this thread become as aggressive as some I have been reading lately. I suggest we should agree to disagree.

Best regards

Chris

 

[Davidc]

Hi David,

Not wishing to make this thread become as aggressive as some I have been reading lately. I suggest we should agree to disagree.

Best regards

Chris

Draw discussion to a close anyway, since a full theoretical analysis of this isn't really appropriate to a cycling forum, and I really can't be bothered to write it.

 

[subaqua]

really simple answer. if the smoke detector bleeps, change the battery for a brand new out of the pack one. better still get a good sparks to install mains powered, lithium battery backed , interlinked ones. the cost v benefit is amazingly good as you only get one chance if theres a fire in the night.

right can i go back to being a bit of a nobber now

 

[Andrew_Culture]

I've spent / wasted most of my life playing in bands, and we check 9v batteries by licking the tops...