Checking battery capacity

[davidej]

The sharp eyed among you will have seen that I have managed to flatten all my batteries. Currently they are in the garage trickle charging.

I will take them into town tomorrow to test. I think all they do is put a large load on and test the voltage. Does this give any indication of the capacity to hold charge?

Two of these are 5yrs old and, even before this incident, I felt they wern't holding as much charge as they used to . Is there any simple way of measuring this other than connecting, say a car headlight bulb and timing how long it burns?

 

[john_morris_uk]

The sharp eyed among you will have seen that I have managed to flatten all my batteries. Currently they are in the garage trickle charging.

I will take them into town tomorrow to test. I think all they do is put a large load on and test the voltage. Does this give any indication of the capacity to hold charge?

Two of these are 5yrs old and, even before this incident, I felt they wern't holding as much charge as they used to . Is there any simple way of measuring this other than connecting, say a car headlight bulb and timing how long it burns?

I don't know of any other way to test them accurately. The technique of using one or two car headlamps and using (borrowing?) a digital multimeter is also cheap. (Except it costs you some patience...)

 

[halcyon]

The sharp eyed among you will have seen that I have managed to flatten all my batteries. Currently they are in the garage trickle charging.

I will take them into town tomorrow to test. I think all they do is put a large load on and test the voltage. Does this give any indication of the capacity to hold charge?

Two of these are 5yrs old and, even before this incident, I felt they wern't holding as much charge as they used to . Is there any simple way of measuring this other than connecting, say a car headlight bulb and timing how long it burns?

If they use the modern gear, it gives all details of the battery, including it's health and if it needs replacing, high load drop tester's are old hat now.

Brian

 

[davidej]

If they use the modern gear, it gives all details of the battery, including it's health and if it needs replacing, high load drop tester's are old hat now.

Brian

What type of company has the hi-tech gear and what should I ask them find out?

I bought the batteries from Colchecter Fuel Injection who supply batteries and are the local Ebby dealers as well as servicing injectors, pumps,etc

Presumably the local halfords will be no good. AFAIK the local auto electrician has closed down so I am not sure where to go.

 

[savageseadog]

What type of company has the hi-tech gear and what should I ask them find out?

I bought the batteries from Colchecter Fuel Injection who supply batteries and are the local Ebby dealers as well as servicing injectors, pumps,etc

Presumably the local halfords will be no good. AFAIK the local auto electrician has closed down so I am not sure where to go.

It's a battery conductance meter you need, Midtronics is possibly the best known make.

 

[halcyon]

What type of company has the hi-tech gear and what should I ask them find out?

I bought the batteries from Colchecter Fuel Injection who supply batteries and are the local Ebby dealers as well as servicing injectors, pumps,etc

Presumably the local halfords will be no good. AFAIK the local auto electrician has closed down so I am not sure where to go.

Any battery firm should have one, they have been standard equipment for around 5 years, looks like a fancy multimeter, select battery type, fit probes to battery terminals, press button, and it does a number of tests, capacity, holding charge, etc.

Try asking Colchester, though it's the sort of gear that Halfords would have, no knowledge required, just feed in details, and press button, wait for answer.

Brian

 

[mtb]

I use what should be used to test a battery ! it is a exide rapid discharge tester. Once connected there's a large coil inside you press the button and see how long it holds the voltage on the dial before dropping. If the needle stays above a certain voltage for the battery's amperage then fine
The so called do it all hand held meters do not put the battery under full starting load so how can that be called a full test.
I have a vw van which due to the glow plugs wouldn't start, out came the AA, he got one of those meters and put my vans battery on test ( I'd told him the battery was fine and why it wouldn't start, but he insisted he had to do a test !) he then printed out a bit of paper which stated the battery was fine and would turn the engine over x amount of times YEAH WHAT EVER
It required jump starting and easy start, no way was there enough in the battery to start it with out jumping it.
Why must things be reinvented sure a multi meter can give an indication re state of charge and level of volt's but the real test is to put it under full starting load
Unless of course a little meter has some magical secret that doesn't melt it's self to put the battery under load

cheers
mick

 

[john_morris_uk]

I use what should be used to test a battery ! it is a exide rapid discharge tester. Once connected there's a large coil inside you press the button and see how long it holds the voltage on the dial before dropping. If the needle stays above a certain voltage for the battery's amperage then fine
The so called do it all hand held meters do not put the battery under full starting load so how can that be called a full test.
I have a vw van which due to the glow plugs wouldn't start, out came the AA, he got one of those meters and put my vans battery on test ( I'd told him the battery was fine and why it wouldn't start, but he insisted he had to do a test !) he then printed out a bit of paper which stated the battery was fine and would turn the engine over x amount of times YEAH WHAT EVER
It required jump starting and easy start, no way was there enough in the battery to start it with out jumping it.
Why must things be reinvented sure a multi meter can give an indication re state of charge and level of volt's but the real test is to put it under full starting load
Unless of course a little meter has some magical secret that doesn't melt it's self to put the battery under load

cheers
mick

Mick,

What you describe is fine for testing the ability of a battery to crank a petrol or diesel engine for starting, but it tells you close to nothing about the actual capacity of a battery that is used for powering lights, instruments and domestics demand etc in a marine situation.

Its the wrong test and is designed for testing a starter battery as the OP was asking about how to test the CAPACITY of a domestic (presumably deep discharge) battery (and presumably in Amp-Hours) which is a totally different thing..

 

[savageseadog]

Mick,

What you describe is fine for testing the ability of a battery to crank a petrol or diesel engine for starting, but it tells you close to nothing about the actual capacity of a battery that is used for powering lights, instruments and domestics demand etc in a marine situation.

Its the wrong test and is designed for testing a starter battery as the OP was asking about how to test the CAPACITY of a domestic (presumably deep discharge) battery (and presumably in Amp-Hours) which is a totally different thing..

I've found a good correlation between a battery performing to its specified cranking current and it's specified capacity. Notice I've used the word "specified", because a leisure battery will have a low cranking capacity and an automotive starting battery will have a high cranking current even though the capacity in AH might be the same. A reduction in cranking capacity will indicate battery degradation and closely corresponds with reduction in capacity. If you don't have the original CCA by specification or previous measurement you won't be able to assess this way.

 

[Daydream believer]

Whoever tests the battery will tell you it is past its sell by date & by fluke they just happen to have a new one in stock that they can sell you

 

[Stemar]

Whoever tests the battery will tell you it is past its sell by date & by fluke they just happen to have a new one in stock that they can sell you

Cynic! ):

Though if it's Halfrauds, you probably aren't wrong.

Batteries frequently don't recover their full capacity when allowed to run flat and, if they were already past their best, as the OP intimates, they seem to suffer more. Because of this, plus the Oh sh!t factor when boat batteries turn up their toes, I'd be tempted to treat the boat to a new set anyway.

Halfrauds batteries strike me as being budget jobs in everything but price, so I'd go for a mid-range brand like Numax bought on line from Tayna or the like.

 

[Zanziba]

Physics perspective:

The battery should be able to deliver 12V-14V when under load (not just across the terminals) so get something that will supply resistance (A known resistor would be a good idea) and connect it up. Measure the voltage across the terminals and check they remain high. A sudden drop would indicate a high internal resistance on the battery and hence it is knackered.

Wiring up to a couple of 12V car bulbs and letting it discharge, taking ammeter readings every 30 minutes would enable you to work out the approximate amp-hours that it can deliver (and hence store) which can be compared with it's rating.

 

[black mercury]

If the batteries were completely discharged, overnight on a trickle charger won't be enough to fully charge them. You might have to charge them for a week, depends on capacity and how low they got. And don't store them on your garage floor if its concrete, set them on a piece of wood, they will discharge themselves very slowly on damp concrete.