Weird battery issue

[A80Avant]

I see. So this is to check if the battery has had it.

This check is done with the battery completely off the car, right?

Do I replace some distilled water if I need to?

[caterpillar]

no need to have the battery out...do it in the car , if you may come to the battery( the du have the weightunit , in some plasticversons too)
and you need some ionisert water or destilled water in, if you have to little( 1,5cm over the cells/ plates in every chamber....6 of them... use safety equipment...acid you know!!
the battery are done if you have bigger different than 0,2 (0,3) and if the acid are black coloured (violet)..... ckassik 1,24 -1,24-1,19-1,21-1,24-1,22 battery are gone bad, change it...
fresh battery with correct charge , and full charged: 1,27- 1,28-1,28-1,28-1,27-1,28... in very cold veather minus 10 or so the acid weight goin higher... 1,30 or so.. thats are NOT correckt

[caterpillar]

Im not kidden about this; i had to live in a place with 30-40 degrees below.. so to turn the engine in theese temp; puuuh!!hard to be the starterunit.... ok battey, high volt, less problems... better lights( alot) less fuel cunsumpions, better heater.....

[Dybro]

This check is done with the battery completely off the car, right?

It depends on how much room you have. But it is always best to pull out the battery before you start checking the specific gravity of the electrolyte (in case of a spill).

Do I replace some distilled water if I need to?

Uhmm... Don't know what you mean by that

You should know that the electrolyte is not just water.. it is sulfuric acid and water. If the electrolyte level goes down it is most likely because some of the water is "boiled off" during recharge. The recharge causes electrolysis and water is split in to hydrogen and oxygen. If these gasses just stays in the battery they can fuse together and become water that goes in to the cell again. But if the H2 & O2 gasses is vented to the atmosphere then the battery has lost some of its electrolyte/water.
The production of H2 & O2 is accelerated when you overcharge the battery (above ~14.4v at room temp).
Some batteries (valve regulated lead acid and AGM batteries, I think) only vent gasses to atmosphere when the pressure inside is to high (e.g. when overcharging them)

If your electrolyte level is low then you should top off with distilled/demineralized/deionized water.

If some of the cells isn't fully submersed (because of too low electrolyte level) then the cell capacity will be permanently reduced and can not be recovered by adding water.

[A80Avant]

I see what you mean.

I will see first if the sealed battery can be unsealed to test. Then report back.

Thanks

[A80Avant]

Hmmm. Plot thickens...

New battery, unusued and charged with 12.65V reading.

On idle 14.2V
On lights on and 2000rpm 13.8V !!!!

What the hell!

Checked Ian's battery and similar tests

On idle 14.56V
On lights on and 2000rpm 14.2V

However Ian has the battery in the engine bay.

So by ruling out things I suppose my cable to the battery may be getting old..? Or the reconditioned alternator is not so good?

Need to find or get a cable and test again, as well as try to measure the alternator voltage on idle as well just to see the difference.

If the cable is the issue, rather than ripping the current one out for another one, would a variable voltage regulator cure things? If I noteably have 0.4V missing and I use the regulator to produce 14.9V instead of 14.5 wouldn't that keep things under control?

[johne]

The cable can only be an issue at either end where the connector is, not in the middle so there's no need to rip the cable out. I suggest you measure the voltage between the battery positive terminal and the alternator output terminal (you'll need to make one of your multimeter test leads very long but that's no issue) and do the same between the alternator body and the battery negative terminal. Any significant voltage drop shows that the problem is in the cable and it's connectors or your earths.

That said, 13.8 to 14.2 isn't that far out given the variability between individual regulators and temperature.

Using a variable regulator can just give you other problems and shouldn't be necessary.

John

[newsh]

I had a very similar issue with one of my bikes, first thing I noted was the heated handlebar grips didn't really get as warm as they should, sometimes the bike would be difficult to start. Revving the engine would actually cause the voltage to drop a little (lights are alway on on this bike). What cured this in the end was to take off both battery terminals and ground straps bolted to the chassis and the engine and clean and grease them, wire brush or wet and dry paper on the metal, no-crode grease on the terminals and copper grease on the chassis and engine bolts, I got my missing volt back and all is well.

[A80Avant]

Cleaning the terminals is an easy thing to do.

Also I will try to measure the new voltage at the alternator which I haven't done using as negative the chassis around the engine. If I get the voltage difference there, wouldn't that prove its not the alternator but somewhere between the alternator and the battery connection?

I will get a couple of terminals clean the bolts and replace bits that are easy to replace before doing anything to the actual long + cable. I agree ripping things out is not fun!

[newsh]

Have a good look at where the wire joins the terminals and the crimps at the ends, you can get corrosion in the crimps, they look ok but they're not.

As Johne says, the big wire will be ok, the terminations are where the voltage will be lost. Definitely measure between the alternator output and the battery positive, if there is resistance you will see the voltage loss (volt drop) as a small voltage, might be your 0.4v. Do the same from engine to battery negative.

[A80Avant]

Bother cables are work of welded on the terminals. I think they are like that from stock!

Checked alternator voltage on idle and its spot on 14.56V.

On the battery its 14.06v

So I'm missing 0.5V which I desperately need.

If I am to replace the terminals that means cutting them and getting new ones to fit on. There is some slack on the cables to reuse them.

Cables from the edge of their terminal joint seem fairly clean, but as you say they may still be of problem.

[AndyP]

Bother cables are work of welded on the terminals. I think they are like that from stock!

Checked alternator voltage on idle and its spot on 14.56V.

On the battery its 14.06v

So I'm missing 0.5V which I desperately need.

If I am to replace the terminals that means cutting them and getting new ones to fit on. There is some slack on the cables to reuse them.

Cables from the edge of their terminal joint seem fairly clean, but as you say they may still be of problem.

Those numbers are pretty similar to mine, you have a slightly bigger volts drop because the avant has a much longer cable run to the battery. I wouldn't worry about it now, unless you're still having problems?

[Pirvu Eugen]

Dont know the RS2...but the 200q with battery under the rear seat had an splice in the battery cable..positive one, near the ecu position for the lhd cars. Maibe the RS2 has that too and there...you can loose alot.
Just a thought!

[A80Avant]

What do you mean by splice in the cable? For what? In the rs2 the cables goes from the drivers side all the way to the battery well hidden under a plastic cover under the carpet. Due to the engine bay being crowded its hard to see where it goes starting from the alternator but I could trace it while it is in the car.

I also noticed that my + cable is around 0.9mm thick which is rated for 130Amp according to the cables on the market however one shop suggested I got the 170amp rated cable as it seems better for my application.

Now looking at the terminals on the market they are horrible looking and cannot seem to find any that have an additional screw on the positive side for additional cable mounting.

I will try and take a photo of the terminals so that experts in here can shed some light as I feel uncomfortable splicing them out only to replace them with less quality ones. They do seem pretty clean.

So that leaves the variable voltage regulator idea as the simplest one although I do know this is not curring the problem its just compensating for an existing problem.

Given the fact that my cables have been soldered on the terminals what kind of cleaning can I do?

[A80Avant]

Those numbers are pretty similar to mine, you have a slightly bigger volts drop because the avant has a much longer cable run to the battery. I wouldn't worry about it now, unless you're still having problems?

I'm not sure I will have a problem or not! Seeing Ian's voltage numbers makes me worried as, as more electrical stuff are on the voltage drops even more.

In fact if the voltage was higher vems wouldn't also have to work harder maintaining a good quality idle when a lot of amp draw is going on with fans and A/C on or heated windscreen which is a huge draw by the way!