Battery issues

I got a new battery back in February(a Numax CXV-X 1000 Amp) , since the colder weather set in a week or so ago, the landy was taking a little longer to start - until Friday when I stopped on way home from work, turned engine off and couldnt get it going again.

RAC came out and gave me a jump - I also asked him to check battery and alternator output to see why it happened.

Votlage was ok, going up to 13.8 fairly quickly. Ampage though (with a device like those home energy monitors) said only 8 amps was going into battery. He said that meant the battery was goosed. The amps in abttery at that time were 380ish (out of 1000!). He wasn't trying sell me a new one as I said I had warranty (3 years !), but suggested I charge it over night and then take it to halfords to get another test (and more evidence for place I bought it from).

I did that, and the guy at halfords didn't really know what he was doing, but the machine told him to do things, so I think the test was OK, even if he couldnt interpret the results properly. The print off said replace suggested, amps were 400 something/1000. Voltage quite happy too.

So my question is, does all that mean the battery is knackered (ie the 8 amps into battery bit - presumably with a 65 amp alternator, I should be getting close to that?). Does it mean alternator is goosed? (RAC bloke said no...but just checkign).

Your alternator should kick out 65 amps, which means that you can use a maximum of 65A worth of lecktrickery stuff, including all your lights, heater, wipers, radio ans whatever else you have on at any given time.

8A into the battery should be OK, as your big 65A charge will only last for a few seconds after your engine is started before it is reduced to between 4A & 8A.

I take it that the drop test gave a CA of around 400A, which should be enough to turn your engine over quite well.

However, if your CA should be 1000A then I would return it and have it replaced as it's still under warranty.

gse1986 said:

I got a new battery back in February(a Numax CXV-X 1000 Amp) , since the colder weather set in a week or so ago, the landy was taking a little longer to start - until Friday when I stopped on way home from work, turned engine off and couldnt get it going again.

RAC came out and gave me a jump - I also asked him to check battery and alternator output to see why it happened.

Votlage was ok, going up to 13.8 fairly quickly. Ampage though (with a device like those home energy monitors) said only 8 amps was going into battery. He said that meant the battery was goosed. The amps in abttery at that time were 380ish (out of 1000!). He wasn't trying sell me a new one as I said I had warranty (3 years !), but suggested I charge it over night and then take it to halfords to get another test (and more evidence for place I bought it from).

I did that, and the guy at halfords didn't really know what he was doing, but the machine told him to do things, so I think the test was OK, even if he couldnt interpret the results properly. The print off said replace suggested, amps were 400 something/1000. Voltage quite happy too.

So my question is, does all that mean the battery is knackered (ie the 8 amps into battery bit - presumably with a 65 amp alternator, I should be getting close to that?). Does it mean alternator is goosed? (RAC bloke said no...but just checkign).

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I think what you are saying is when the RAC man put a load tester on the battery the voltage came up to 13.8 volts against a load? The current flowing into the battery, as the alt was spinning, was 8 amps, so that is a fairly hefty charge; if you charge a battery much harder you would knacker it.

That does sound to me like the battery is goosed however he has based that diagnosis on knowing A. the car wouldn't start on it and B. you had been driving so he would assume it got a charge, so the assumption is, it's not holding a charge therefore it is knackered - and this may be correct.

But, it doesn't allow for a battery that may have been depleated and just needs a bloody good charge. With a big starter motor and cold temperatures batteries can take a fair hammering, if journeys are short then the battery will never get the chance to charge well and it will display characteristics of a failing battery, a good charge before it gets profoundly discharged may save it.

Now what did the Halfords tester look like? Did it have a big load on it to put the battery under some load when it tested it?

The charging method is not really as basic as taking the full 65amp output and blasting it into the battery, if the alternator see's a lower voltage it will increase output to maintain system voltage around 14.4volts, turning on the headlights will load the system, the voltage drops again and the alternator can ramp up output to keep the system voltage up.

The battery just becomes a load like any other once the alt is spinning, if it is the ONLY thing requiring power, so no lights or radios or heaters, then it will be the only real load on the system causing the voltage to fall, the alternator then increases output so that the system is sitting at 14.4v ish. The alternator does this by increasing currant, so if voltage needs raised only a few volts it will only need 4 or 5 amps to hold the voltage up and this will flow into the battery to charge it - as the requirement to hold the system voltage up against the battery falls the output will fall till on a long drive with no other loading the alternators output could be less than 1 amp.

So 8 amps is quite a lot as I said, for a while after start up that might be fine, but it if continuous then perhaps the alt is making up for poor battery performance, or you have let your battery get quite low - only you can know if you give your battery a hard time.

Remember the battery needs charge time, without charge time the battery can never come back up to a good level of charge.

Note: People who give the car a 5 minute idle in the cold weather to "charge the battery" are in fact probably making it worse.

Cheers for the replies.

OK, that makes a bit more sense - to be 8 amps/65 sounded awful - I was basing this that 65 amps for an hour would charge a 65 amp hour battery completely - probably am wrong here.

I'll give it another night charge tonight, and see what happens. I do only shortish journeys, so this could be the reason - it did last the winter last year though, (obviously a different battery), before eventually dying in Feb when even a full night charge wouldnt start the engine the next day.

I'll report back shortly!

In reply to the questions re halfords, they just had a hand held device that told him like turn headlights on, start engine, turn heater on etc. Then produced a report.

Well overnight it charged, but my charger was now charging at ~2 amps, where before it was charging close to 4 (car battery charger, not alternator )

I'm not sure if this suggests the battery is getting full?

short journeys kill batteries, get a trickle or solar on it to keep it topped up

Just for your info. I bought a brand new battery which went off after one year. It wouldn't hold its charge. When I took it back they tested it and replaced it under the guarantee which was a three year guarantee. I think sometimes you do get a duff one.

mikescuba said:

Just for your info. I bought a brand new battery which went off after one year. It wouldn't hold its charge. When I took it back they tested it and replaced it under the guarantee which was a three year guarantee. I think sometimes you do get a duff one.

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Interesting. Mines a three year guarantee too. How bad did yours get? It's difficult for me to spot how long its been bad, as it seems the cold has pushed it over the edge. That said, so far only had it not start once....

also that battery is not cca it's mca.. probably closer to 850cca

gse1986 said:

Interesting. Mines a three year guarantee too. How bad did yours get? It's difficult for me to spot how long its been bad, as it seems the cold has pushed it over the edge. That said, so far only had it not start once....

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I started noticing it wasn't turning over so quickly after about 18 months, But then the winter came along I first put it down to the cold weather but then it let me down completely one morning. I charged it right up over night and the same thing happen again about a week later. The battery was just over two years old. Its a Banner. I replaced our three cars with Banner and never had any problems with the others, just the one in the defender. In fact one of the batteries is five years old and still going strong.

gse1986 said:

Cheers for the replies.

OK, that makes a bit more sense - to be 8 amps/65 sounded awful - I was basing this that 65 amps for an hour would charge a 65 amp hour battery completely - probably am wrong here.

I'll give it another night charge tonight, and see what happens. I do only shortish journeys, so this could be the reason - it did last the winter last year though, (obviously a different battery), before eventually dying in Feb when even a full night charge wouldnt start the engine the next day.

I'll report back shortly!

In reply to the questions re halfords, they just had a hand held device that told him like turn headlights on, start engine, turn heater on etc. Then produced a report.

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A 65amp charge into a car battery, or most batteries for that matter would boil it.

The lower the current the better in fact, we just don't have weeks waiting around for a battery to charge at 100mA!

The dropping in amps goes back to what I said about current vs. voltage, the batteries voltage is coming up, which means it needs less current to charge it. When the rate drops to less than an amp it's pretty damn full.