flat battery?

Anonymous · Post by **Anonymous** » Tue Sep 25, 07 12:49 pm

Just a little input. I dont understand why you are looking / testing for high resistance joints. Dave suggested checking for a short circuit, but it isnt clear whether you have done this.

If you are testing the battery after driving the car and finding it is flat, there are three things it could be.

1: A short circuit (which may be intermittent i.e. an cable splashing down off the body work).

2: Charging circuit not functioning correctly (over charging as well as failing to charge at all).

3:) Battery is shagged.

Lets briefly (as this is a very big area) talk batteries (they are regularly misunderstood). If you overcharge the battery, it will gas (cook). This is when the electrolyte boils away to the point whereby the battery cell plates over heat, and buckle. Once you get a shagged cell, the whole battery string is for the skip as cells cannot be changed individually on these sealed units. So, if you have the correct level of electrolyte in each cell, you then go on to check the Specific Gravity (SG) of the electrolyte. Not sure on an exact reading, but your newly purchased battery hydrometer should show an SG level of between 1130 - 1250 for a decent health, and all cells ought to be within 30-40 either way, of each other. A big difference in one against the others means the cell is playing up.

As I have already mentioned, cells play up when they are cooked (too high a charge) or as Steve said, drained to nothing whereby they never fully recover. So, how would you shag a cell?? By over charging (see 2 above) or undercharging (see 2 above) (regulator either constantly telling the alternator to charge the battery, or telling the alternator the battery is charged when it isnt). So what you are trying to understand, is ultimate battery condition bfore fitting, and subsequent condition after it has been run on the car, as the latter can help in understanding where to look for the problem.

So, if your battery is good, and the charging system is functioning correctly, you either have a massive short (visual inspections, then breaking down wiiring and doing insulation resistance (NOT continuity) tests.

Or, the battery might just not be big enough for the car. You need a big Amphour battery to crank one of these engines, and a little bugger just might not recover quick enough after a short drive to turn it over again.

There you go. I could write for hours about Lead Acid batteries, NiCad LIon and so on. We have spent many thousands and thousands of pounds on understanding why batteries do not perform. Its a subject that is suprisingly big.

Hope the above helps.

Oops - I got sensible again

AllKiller · Post by **AllKiller** » Tue Sep 25, 07 1:22 pm

Nice reply Clivey

And from what i have read you replaced a duff battery with a battery with a slow discharge

.....so replaced Duff with duff

Apologies if im wrong there

the dodge · Post by **the dodge** » Tue Sep 25, 07 1:41 pm

yeah i agree it is, still trying to get my head round it,
atleast if this new battery is duff i can get a replacement or my money back, from memory the battery is 12v, 75ah, 625 cranking amps
just picked up a new earth lead so will fit that tonight - compared to the original one well, the original certainly does look nackered!!!

Anonymous · Post by **Anonymous** » Tue Sep 25, 07 1:48 pm

Well that isnt going to hurt fella.

Once you have been through the basics, the only thong you can do is look at all the components (alternator, regulator, battery, cables etc.) as a system. Understand the relationship between them and work out how to establish whether each component is doing the right thing, correctly.

The battery you have seems to be large enough. I wouldnt go much lower on the cranking power or the Ah though.

Dave-R · Post by **Dave-R** » Tue Sep 25, 07 2:15 pm

I don't think you have done or completed any of the tests I outlined which whould have isolated the problem. Instead you are just shooting in the dark.

If you can't do what I suggested or answer any of my questions then I can't help you.

Anonymous · Post by **Anonymous** » Tue Sep 25, 07 2:18 pm

the dodge · Post by **the dodge** » Tue Sep 25, 07 2:19 pm

well i'll let you all know how it went tomorrow, thanks all for your input that's what i like about these forums - you get lots of info & advice about things you wouldn't imagine could be the problem and usually you get the answer to it to, as they say many heads are better than 1

Dave-R · Post by **Dave-R** » Tue Sep 25, 07 2:22 pm

Skippy wrote:

What?

I am just stating facts.

Anonymous · Post by **Anonymous** » Tue Sep 25, 07 2:23 pm

Anonymous · Post by **Anonymous** » Tue Sep 25, 07 2:25 pm

It's the way you tell 'em Dave

You sounded like a strict headmaster with a cane in his hand ready to tan some ass

.

Anonymous · Post by **Anonymous** » Tue Sep 25, 07 2:33 pm

33 Plymouth wrote:
You sounded like a strict headmaster with a cane in his hand ready to tan some ass

.

I wonder how much Dave charges for that then.....

AllKiller · Post by **AllKiller** » Tue Sep 25, 07 2:42 pm

You tell em Dave

Dave-R · Post by **Dave-R** » Tue Sep 25, 07 3:10 pm

£50 quid a time. Not including "extras".

Anonymous · Post by **Anonymous** » Tue Sep 25, 07 3:12 pm

AllKiller · Post by **AllKiller** » Tue Sep 25, 07 3:22 pm