battery question

[ianainge]

i have bought my batteries home and need to check if there are ok as i think one might be knackered, if i charge them up to full and put a test meter across them what should they read. second question. if i leave them for a week is there an element of discharge that occurs if so what realistically what should that be, at what point should i determine one has had it.Thanks.

 

[sfh]

You need to take the battery to a garage or an auto electrical company and have a High Rate Discharge Test, this will determine the condition of the battery.

 

[spannerman]

Or invest in a battery hydrometer, then you can check the specific gravity of each cell, they are graduated to tell you the correct reading. If one cell is duff then you can see immediately. Assuming of course you dont have sealed batteries.

 

[hlb]

A hydrometer is only a couple of quid. If one cell is down the battery is knackered.

<font color=blue> Haydn

 

[JEG]

Some modern batteries cannot be tested by means of a hydrometer so perhaps the following will help: Charge the batteries & leave disconnected overnight, check voltage next day. 12.7 good, 12.6 so so, 12.5 bad [source haynes motor manual]

 

[halcyon]

The only way to check condition of battery is a load test, puts a high load 100/200 amps on battery and measures the voltage it drops to after a time.
Voltage is very dependant on type battery,charge level, air temp, age, even air pressure, but off load after 8 hours, 12.7/12.8 volt is about 100%, 12.0 volt is flat, it is approx a straight line between the top and bottom voltage, around +/- 5% error. But it gives a quick guide, remember that on load and on charge the voltages are totally different, which is why you have to allow battery to settle with no load.

Brian

 

[boatone]

How old are the batteries?
How many are there?
Are they used singly or as a bank?
What makes u think one is knackered?

If they are more than 4-5 years old just buy a new lot.
If they are used in a bank and one is knackered and they are more than a few months old you will need a new lot anyway cos bad news to mix old and new batteries in a bank.


<A target="_blank" HREF=http://www.boatsontheweb.com/galleryframes.html> BoatsOnTheWeb, Photo Gallery, Chat Room</A><P ID="edit"><FONT SIZE=-1>Edited by boatone on 06/01/2003 10:19 (server time).</FONT></P>

 

[tcm]

Re: Drop test

Don't think you can checkem with an ordinary meter. You need a special meter.

The man at the shop puts a special meter (hydrometer?) thing across them and says "well they're fine! No need to waster money on new ones!" So you refit them. Then the same prob reccurs. So you buy new batteries anyway. Then the problem goes away. Then the electrical man who turns up who hasn't been unbooked finds something wrong with some other thing like the alternator and that gets fixed too. Usually, the whole job gets sorted for less than a grand.

 

[Chris_d]

Try this...

www.actmeters.com/actmeters.htm

Look at the ACT IBT Intelligent battery tester, its a bit expensive but works well with all types of batteries, we use them to determine the condition of racing car batteries, when you need to know if the battery is a least 95% good and in A1 condition.
Have used loads of drop testers and they will basicaly confirm that a battery is knackered or flat but nothing in between.