Battery Testing ?

[cancunia]

Can anyone suggest ways to test a 12v battery AH capacity / CCA other than with a bespoke battery tester? 

Thanks

[oilyrag]

Although most batteries are supplied new with that info it is not going to be easy to verify either figure other than seeing how long the battery lasts at a given discharge load such as headlights. The CCA is also something of a theoretical figure and temperature, age of battery etc will impact on the actually available power. 
I don't think it's something that will be easy to do but no doubt someone will know, having burnt their shed down

[saskak]

Very difficult to do without a battery tester. I suspect it can be done with a known load, something that draws a known constant current (Amps), e.g. light bulb, 12V fan, but that is way too small current drawn. Charge the battery to max, leave out there for 24h, then put your load on, measure voltage of battery with a mutlimeter at regular intervals and leaving 1-2h of not being on load before measuring. Test until it drops to a predefined limit of volts. That would be your 50% discharge, but very difficult to say what 50% is in term of volts. I would say 12.1V is a safe limit to discharge it to and ~50%. Sum up the Ah that have been drawn and compare to the Ah stated on the battery. That is a pretty good gauge where the battery is at. Ambient temp is also a factor.
It is difficult to convert Ah to CCA, but apparently rule of thumb, taken with huge amounts of pinches of salt, is Ah*7.25=CCA. Do not quote me on that one.

[oilyrag]

I'd like to be in the next door garden when Yimal does the test of 250 Amps for 15 seconds ...or maybe a bit further away than that - allowing for the battery probably boiling itself !  A battery that has been pushed down to 9.6 volts may never recover .....
If Cancunia does want to see if a battery is still any good, or as good as it should be, just take it to a garage and give them a drink whilst they attach their prongs to it ....... a bit quicker than waiting for a bulb to go out!
Alternatively put it on the car, leave the headlights on for half an hour. If the car still starts then it's a good'un.

[geoff]

I've been watching this with interest ... a method self method of testing? ... not aware of any

Testing a battery for AH and CCA ??? Why would you even want to even try to determine these values yourself when you can get a FREE discharge test done with proper equipment by most any garage / battery / tyre / exhaust depot that will determine battery efficacy ?? It takes seconds to complete.

I find the human human ear easily detects cranking speed and is capable of recognising any relative loss of speed over time ... ideal for longer term ownership.

Anyway I'm with Oilyrag and his comments above !

[saskak]

I've been watching this with interest ... a method self method of testing?  ... not aware of any

Testing a battery for AH and CCA  ???   Why would you even want to even try to determine these values yourself when you can get a  FREE  discharge test done with proper equipment by most any garage / battery / tyre / exhaust depot that will determine battery efficacy ??  It takes seconds to complete.

I find the human human ear easily detects cranking speed and is capable of recognising any relative loss of speed over time ... ideal for longer term ownership.

Anyway I'm with Oilyrag and his comments above !

Now yes, if the question was how you can do it then getting a battery tester or using one from a garage/shop is the easiet to do. The question was without a bespoke tester, hence people answered that. I read without a bespoke tester as not having access to one, not being able to go to a shop/garage is included in that category in my eyes.

EDIT: I re-read the post again: "Can anyone suggest ways to test a 12v battery AH capacity / CCA other than with a bespoke battery tester?". Can you suggest ways to test the battery, explicitly stating other than with a tester. So people did that, including me.

[cancunia]

Yes, it's easy to go to the likes of Halfords, Quickfit etc but here's the problem & why I put the question in the General Chat section. It's not for a car, it's for my motorbike.
I can measure the voltage pre/post charge & with the engine running without issue but wanted to know more about the actual capacity and cranking power without buying a battery tester or getting some head scratching at a car shop.

[oilyrag]

You're absolutely right in your answer to the original question saskak! But as you say, you need to make assumptions as to where 50% is ..... and that 12.1 volts is the right one, and although correct it just hasn't the entertainment value of burning the shed down!

[saskak]

You're absolutely right in your answer to the original question saskak!  But as you say, you need to make assumptions as to where 50% is ..... and that 12.1 volts is the right one, and although correct it just hasn't the entertainment value of burning the shed down!

Haha, yeah. I was thinking of something in the range of 1-2Amps, rather than 250 which will probably create work for the local fire brigade.

[oilyrag]

Yes, it's easy to go to the likes of Halfords, Quickfit etc but here's the problem & why I put the question in the General Chat section. It's not for a car, it's for my motorbike.
I can measure the voltage pre/post charge & with the engine running without issue but wanted to know more about the actual capacity and cranking power without buying a battery tester or getting some head scratching at a car shop.

Nearly every motorbike battery I've had lasts one day longer than the warranty