[stevieg]

As the title states how(with one of those hand held meters)do you test a battery.I have looked at these and there are all sorts of dials etc so (chapter and verse)what exactly do you do?
I have one controller that gives a volt readout but have 2 setups so would like to be able to do the same with the other and spare battery.

[dai]

I use a cheap mutimeter about 8 quid. Move the dial onto 20 volts and put the clips on the battery terminals. A fully charged battery should read about 13.5 volts, when it reads 12 volts it needs charging.

[jeff1]

Check the voltage like Dia said but if you have Just used your battery then give it at least 20 minutes to stabilize.

Checking the voltage of a battery is not the correct way to check a battery?  A battery should be checked under load and this is done with the meter set to Amps and the pos and neg leads connected in-line with your pump.

[dai]

Check the voltage like Dia said but if you have Just used your battery then give it at least 20 minutes to stabilize.

Checking the voltage of a battery is not the correct way to check a battery?  A battery should be checked under load and this is done with the meter set to Amps and the pos and neg leads connected in-line with your pump.

Thanks Jeff, could you be a little more specific, this is an important bit of info that we could all benefit from.

[michael papworth]

A battery needs to be tested under load. Yes, that's right. But it's not tested the way that Jeff1 said. You don't measure current.

Please, don't attempt to measure current. It's not quite as easy and straightforward as you might imagine, especially when dealing with motors which can draw a large current on start up.

Garages have a special device that draws a large current from the battery and measures the voltage at the same time. That's the way to do it.

To be honest, you don't need to test your battery. You'll know if your battery is duff - it won't hold its charge long.

[jeff1]

Hi Dia

Ok lets first check the amperage of our pump? Although its often specified to a certain amperage not every single pump that comes off the production line is tested so a +/- will always be true.

We need to do the amps test in series and the best way to do this is to disconnect the positive terminal of our pump,  (now your meter must be capable of 10amps) connect your leads to the meter taking care to connect it to the amp socket on your meter often denoted by a letter A, with your meter cables connected to your meter, now put your negative probe onto the positive battery terminal and your positive probe onto the battery connection,  Turn your meter to the 10 amp range and switch on your pump, You will now see the current drawn from your pump, leave it running for a minute or two, this Stabilise's the meter reading and puts your battery under load  (this is what we want) you now have a true reading of your own pumps current draw from the battery.

Now if you were to take a voltage reading of your battery straight after this test you will be faced with a completely wrong mis-leading reading, leave the battery for 20 minutes to half hour and go back and take another reading and you will be faced with a different reading because the battery has now had time to settle and stabalise its self.

You will have now tested your battery after a load test. HTH

Just seen wally's post.
Wally were doing a current test to put a batter under load hence my 10amp range setting of the meter, you measure current to get a current reading of an item and in our case our pumps, a pump running has now put your battery under load so once the battery has stabalised you now take a true voltage reading.

[michael papworth]

Strongly advise that you don't attempt to measure current.

If it holds its charge, it's OK. If it doesn't hold its charge it needs replacing. That's all the test that you need.

[jeff1]

I've been taking current readings for years and they are completely safe and as safe as a voltage reading.  :

[michael papworth]

I've been taking current readings for years and they are completely safe and as safe as a voltage reading.  :

OK. You've been doing it for years and you know about voltage, current, resistance, internal resistance, motors, back emf, inductance, capacitance and all that stuff.

You know how to set up a circuit and check it. You know Ohm's Law and Kirchoff's Laws and bridge circuits and potential dividers and Lord knows what else besides.

You know it and I know it.

But we're talking here about people who don't have your knowledge and mine. I still suggest that no one go messing about with making current measuring circuits and using ammeters without having a full knowledge of all these things. They obviously don't or they wouldn't be asking.

And even if they did, what are they going to do with the readings. If its 258 mA or 2.58A, what's that going to tell anyone?

What's going to happen to someone who doesn't know about these things? They know how to measure voltage by putting the voltmeter across the terminals. They then think, "Oh, I'll measure the current in the same way."

I'll tell you what will happen. Sparks - and lots of them for about 3 microseconds and then nothing but a burnt-out ammeter and possibly burnt hands as well.

Repeat, don't go measuring current unless you know precisely what you are doing. And if you have to ask on a window cleaners forum, you evidently don't know.

And I still say it's an unnecessary thing to do. You will know if your battery is OK or not by the way it holds its charge. And that's enough.

So, the simple answer to the question:    "How do you test a battery status with a meter?" is "Don't, because if you have to ask, you can't."

[jonnyald]

garages and places selling batteries will test it for free normally with a load tester which is a big copper shunt that goes between the 2 terminals.  instant result

 a few years ago those testers were about 40£  it has two long prongs to touch on the terminals and a little meter fixed in the middle of the shunt
 

[michael papworth]

garages and places selling batteries will test it for free normally with a load tester which is a big copper shunt that goes between the 2 terminals.  instant result

 a few years ago those testers were about 40£  it has two long prongs to touch on the terminals and a little meter fixed in the middle of the shunt
 

Yes. Exactly right.

The only safe way to do it is to get someone else with the knowledge and kit to do it.

[AuRavelling79]

I've been taking current readings for years and they are completely safe and as safe as a voltage reading.  :

...


You know it and I know it.

But we're talking here about thick people like Gold who don't have your knowledge and mine. I still suggest that no one go messing about with making current measuring circuits and using ammeters without having a full knowledge of all these things. They obviously don't or they wouldn't be asking.

And even if they did, what are they going to do with the readings. If its 258 mA or 2.58A, what's that going to tell anyone?

What's going to happen to someone who doesn't know about these things? They know how to measure voltage by putting the voltmeter across the terminals. They then think, "Oh, I'll measure the current in the same way."

I'll tell you what will happen. Sparks - and lots of them for about 3 microseconds and then nothing but a burnt-out ammeter and possibly burnt hands as well.

Ouch!

...

There. I fixed it for you. Quite right too. 

[michael papworth]

It's the way I am. I don't always know when people are serious or joking. And that can get me into a lot of trouble.

I'm in no way suggesting that anyone who doesn't understand these things is thick. It's just that they don't have the information.

That's OK. I'm not thick, but I wouldn't know how to go about neutering a cat ... so I wouldn't try to. Cats can get quite stroppy about his sort of thing.

So, if your're seriously offended, I'm truly sorry. '

If you're joking (which I hope you are)  '

[AuRavelling79]

Joking of course! 

[dai]

Thanks to both Wally and Jeff, just one more question.
Our batteries are rated in amp hours, does this mean that if I had a 100 amp hour battery, and my pump was drawing 10 amps, it would run for 10 hours before being totally discharged?

[michael papworth]

Thanks to both Wally and Jeff, just one more question.
Our batteries are rated in amp hours, does this mean that if I had a 100 amp hour battery, and my pump was drawing 10 amps, it would run for 10 hours before being totally discharged?

Yes, that's pretty much it.

a 100Ah battery will supply 10 A for 10 hours, or 5 A for 20 hours etc.

It's not absolutely precise. It's more of a guide, and it's quite a good guide at that.

So, the short answer is yes. The amount of energy stored is proportional to the current x the time taken to discharge it.

The common unit used is the Amp Hour. It's not an "approved unit," but it's a useful one for battery manufacturers and buyers.

(You probably know that electricity is bought from the power suppliers in kWh - units. Kilowatt hours. That's pretty much the same idea.)

[dai]

Thanks Wally, that's what I thought, It's handy to know as many battery experts recommend charging deep cycle batteries when they are half discharged.
I always tend to run my backpack battery flat, using the above methods and checking the draw under load, I can work out just how long to run a backpack to ensure maximum battery longevity.

[stevieg]

Great news! Lidl are selling for the princelly sum of £1.99 a battery tester.

[John Walker]

Great news! Lidl are selling for the princelly sum of £1.99 a battery tester.

Is that a current or voltage tester and can it also check if a cat has been neutered correctly