Questions About Battery V, Condition, Drain

[GLPoomobile 958]

I bought a new Halfords battery a year ago. Unfortunately, with my car being left unused with the alarm armed, I've managed to run the battery down a few times.

 

One of the things I've noticed is that the voltage will slowly drop over time with the battery disconnected. So after being charged it might start on 12.60v, then drop quickly by the next day to 12.40v, then down to 12.25v, and over the next few days slowly down to 12.17v. I'm not sure if it would drop any further as by this time I'll have usually put it back in the car.

 

What voltage would you expect to see on a freshly charged good condition battery? And should it be losing voltage as shown above?

 

Lastly, what would be the minimum voltage (ball park figure) that you could get away with to crank the starter on an Mi? Cos mine dropped down to about 11.70v (I had the lights on while I was trying to fix dodgy connections/blown bulbs etc) and it wouldn't crank for s*it. The fact that the battery dropped enough to not start in such a short space of time with the lights on also concerns me.

Edited October 2, 2009 by GLPoomobile

[ablister 31]

take it back to halfords, they should be able to test it with their battery tester. But battery sounds like it has a high internal resistance for it to drain itself

[RossD 44]

Charge the battery and then leave it overnight, check the voltage. Anything below 12.1v and it's had it. 12.5 is fair condition and 12.7 or so is good. I suspect yours might be 12.1 or lower!

[chrisj21 2]

A topic of mine a few months back

 

topic

 

I was quite supprised how little the battery had to drain to not start the car. This was a 1.9 8v.

 

Chris

[kyepan 291]

just to share my own thoughts and experiences.

 

batterys that are left uncharged for long periods go through a process of sulfication where the sulphuric acid reacts with the lead sponge to produce... lead sulphate. This process is somewhat reversable by shocking the battery with higher voltages, expensive battery chargers such as the halfords one priced at about 50-60 do this, so do the slightly cheaper non halfrauds ones. However in some cases it is not completly reversable.

 

I was in a similar situation, battery often going flat, and did manage to damage a budget battery. either get yourself a decent charger that desulphates and give it a go, or get a new battery. I opted for new battery as the terminals were wrecked on the older one, peugeot sold me a budget battery for less than 40 quid.

 

Also as you replied to the other post steve, you'll realise that dodgy terminals can seriously affect the battery's ability to transfer enough charge to fire and turn the starter, so i'm sure you've probably checked them.

 

Hope this helps.

[Cameron 16]

You really need to do a cranking voltage test to find out of its shagged or not. Get your multimeter on the battery and note the voltage, then crank the engine and note what the voltage drops to. Anything below around 9.5V and its unhealthy. A healthy battery should be able to sit for a few months and still have enough charge to crank the engine.

[GLPoomobile 958]

Cameron - I presume you mean to watch the voltage drop as the starter tries to crank the engine. Or do you mean, crank the engine, then stop, then see how much the voltage has dropped? (I don't think you mean this, but just clarifying).

 

Justin - battery terminals should be good as they are almost prefect condition. I think I re-used the positive one but the negative one is new as it came attached to the new length of cable. All the cables were replaced just before I did the new loom.

 

I last used it at 9pm yesterday, and I'll be going out in it at around 7.30pm tonight, so I'll see what the voltage is before I start it tonight. I didn't measure it yesterday though, but I know it was 12.7v a couple of days ago after I'd had the engine running.

 

It may just be that it needs some 'proper' charging from a few good runs in the car. But if I still see a voltage drop over the next few weeks (or if it's dropping to much when cranking) then I'll take it back to Halfords.

[kyepan 291]

It may just be that it needs some 'proper' charging from a few good runs in the car. But if I still see a voltage drop over the next few weeks (or if it's dropping to much when cranking) then I'll take it back to Halfords.

 

unfortunately only desulfication will restore it's potential to accept and hold charge. cycling the battery doesn't create the conditions to break down the suphates.

 

like i previously said there are a few good battery chargers that will desulphate.

 

also check for current drains if you believe the battery is in good health, this has been covered many times and is very quick to do.

 

J

[Cameron 16]

Yeah that's what I mean, check voltage while the engine is cranking.

[large 33]

What you normaly find is if you let a battery discharge itself to a low voltage say 9v or less. you run the rick of warping the electrod plates in the battery. The battery will then not hold a charge for long (time is dependant on the damage).

 

So don't let your batterys run flat.

[GLPoomobile 958]

Well, after it having some use again, it seems to be OK now. I think

 

I left the car for about 2 weeks, and had to use it the other day. First thing I did was to pop the bonnet and get the multimeter out, but ironically the battery in the MM was drained as I think I had left it switched on. It still had a display but was just reading 1 when connected to the battery (worked fine after swapping the battery). Anyhoo, without knowing what the Pug's battery was reading, I started her up and she fired pretty much straight away. Starter sounded fine. Ran for a couple of minutes then went in doors to sort the multimeter out. When I came back out a while later the battery was reading something like 12.45v.

 

So from using it on Monday evening, it was then this morning when I used it next. Checked it with the multimeter and it was showing about 12.40v. Started it up, sounded fine, ran it for about 30 seconds just to pull the car forward a foot, then switched it off. Came back out 20 minutes later, went to start it, and the starter just groaned like an old man on his death bed Tried again and it was a little stronger, and after cranking very weakly for a few seconds it was just enough to firer the engine. I can only imagine this was something to do with the damp weather. All the earth wires are new, with good earth points. The positive wires are all new. The starter solenoid wire is new. The starter has never given me cause for concern before.

 

So, I'll keep an eye on things and see how the battery goes.

[DrSarty 90 1 Cars]

I think batteries get a lot of bad press, when actually they're pretty much the same and not easy to make incorrectly.

 

I believe they just die quickly if installed either incorrectly or into a system where they become over stressed, die early, and hence get the blame.

 

What I mean is they rely on a good alternator, that charges at the right amount. If they charge too much then they cook the battery, literally.

 

The battery depends on good thick cables and clean, corrosion free, tight* connections and grounds that are as short as possible and go to bare (protected) metal.

 

*I don't mean overly tight; I mean a correct electrical connection. For example battery posts are different sizes, and they are also tapered/conical. The correct terminal must be fitted to ensure maximum contact.

 

Batteries also hate the cold, and being used to start a car and then not being driven enough to recoup the charge will slowly/rapidly and surely kill a battery too.

 

Starter motors are another link in the system which can kill a battery early. If it's naffed, with poor quality wiring and suffering from heat soak, the battery has to work even harder so dies early again. I would suggest every 3-4 years replacing/reconditioning a starter motor is not a bad idea TBH.

 

So really what I'm driving at is that your battery becomes the weak link once placed in a system which doesn't support its operation. They sit forever in Halfords retaining their charge. It's only when they're used, and what they chuck out is not proportionally 'put back' that they die early and get shouted at for being crap.

 

It's not their fault. Hug a battery today.

Edited November 2, 2009 by DrSarty

[Rob Thomson 6]

It's keeping batteries discharged that screws them up. Lead acid batteries need to be kept charged or they rapidly degrade.

[kyepan 291]

Well, after it having some use again, it seems to be OK now. I think

 

I left the car for about 2 weeks, and had to use it the other day. First thing I did was to pop the bonnet and get the multimeter out, but ironically the battery in the MM was drained as I think I had left it switched on. It still had a display but was just reading 1 when connected to the battery (worked fine after swapping the battery). Anyhoo, without knowing what the Pug's battery was reading, I started her up and she fired pretty much straight away. Starter sounded fine. Ran for a couple of minutes then went in doors to sort the multimeter out. When I came back out a while later the battery was reading something like 12.45v.

 

So from using it on Monday evening, it was then this morning when I used it next. Checked it with the multimeter and it was showing about 12.40v. Started it up, sounded fine, ran it for about 30 seconds just to pull the car forward a foot, then switched it off. Came back out 20 minutes later, went to start it, and the starter just groaned like an old man on his death bed Tried again and it was a little stronger, and after cranking very weakly for a few seconds it was just enough to firer the engine. I can only imagine this was something to do with the damp weather. All the earth wires are new, with good earth points. The positive wires are all new. The starter solenoid wire is new. The starter has never given me cause for concern before.

 

So, I'll keep an eye on things and see how the battery goes.

my old battery was like this it would read just over 12v.. but go to start it and it only gave couple of turns, looking at the voltage whilst cranking showed that it dropped to 6v.. 5v .... 4v... then rapidly rose back to 12.5 once the load was removed /not cranking (literally in the time it would take to get from the ignition key to having the multimeter on the terminals).

 

as previously stated, the battery is sulphated, either get a charger that restores it or get a new battery and make sure it is not run flat.

 

cheers

 

J

[GLPoomobile 958]

J

 

I forgot to mention that I did as Cameron suggested a few weeks ago, and checked the cranking voltage. Can't remember what it was but it didn't go below 9.5v.

 

Would have been handy to have done that the other day when it was struggling.

[kyepan 291]

J

 

I forgot to mention that I did as Cameron suggested a few weeks ago, and checked the cranking voltage. Can't remember what it was but it didn't go below 9.5v.

 

Would have been handy to have done that the other day when it was struggling.

ah ok... still based on what you have said, the battery got left uncharged for a long time, this allows the chemical process of sulphation to take place..

 

i bought one of these from halfrauds, and am very happy with how it restored my battery, which had been left for several months in a low or very low state of charge..

 

hope this helps you make progress towards a usable car mate!

 

J

[petert 586]

Once the cell voltage drops under 1.83V (11V in total), irreversible desulphurisation occurs. A battery is fully discharged at approx. 11.5V.

[GLPoomobile 958]

I reckon the starter might be on it's way out. I was driving back from Haywards Heath this afternoon and pulled into a private lane to go for a piss in the bushes 2 minutes later I try to start it and the motor was really labouring. Stopped, tried again, same thing. 3rd time, it laboured and then on about the 4th revolution it sort of picked up a little bit and just managed to crank fast enough for the engine to catch.

[kyepan 291]

I reckon the starter might be on it's way out. I was driving back from Haywards Heath this afternoon and pulled into a private lane to go for a piss in the bushes 2 minutes later I try to start it and the motor was really labouring. Stopped, tried again, same thing. 3rd time, it laboured and then on about the 4th revolution it sort of picked up a little bit and just managed to crank fast enough for the engine to catch.

mine was like this when the battery terminals were not making good connection, got worse when it got hot.

 

try it cold, see if it cranks faster.

[GLPoomobile 958]

Justin, it's done it a few times when cold too. First start in days and it labours, give it another go and it just about catches.

 

I'm not ruling it out, but all the wiring and connections (on the engine side at least) should be fine. It's all new wiring, the battery clamps are new too, and they are on tight. Also don't have that horrible OE connection on the -VE battery post, that was replaced with a proper clamp.

[lagonda 42]

Batteries are one of the few things that last better when used than left idle. Was seen over a bit with my CTi, bought it with 2 days MoT from a TVR dealer who assured me it would pass no trouble....& it failed 2 months later on knackered rear beam, which took me 2 months I couldn't spare to fix. Due to lack of use, battery knackered, so swapped in the one from my old Y10, which wasn't new when I bought the Y10 in 1998. Sure that battery couldn't last, I bought a still-guaranteed battery from another forum member. Tried it a year later....dead, wouldn't charge. Meanwhile, pre-1998 (& it's only a crap budget one) battery still going strong.

 

I have heard it does batteries good to completely discharge & then charge them occasionally...which I have done, albeit inadvertently!

 

Your starting problem could be resistance related....resistance increases with heat, which is possibly why it might have started from cold, & with little time for the alternator to charge, not enough power to overcome increased resistance....has your new wiring included checking/changing the main battery cable terminal on the starter? Mine (unbelievably, but tell that to Peugeot bean counters) was steel, & half burnt through....fortunately my soldering iron was just up to soldering a brass one on....just like Peugeot should have done originally.

[Simes 248 2 Cars]

I rarely use my car.

It can sit there for a few weeks before it moves.

 

I bought one of these

 

http://www.ctek.com/EN-GB/Buy-Charger.aspx?charger=mxs3600

 

I just leave it plugged in and remove it when I want to use the car.

[GLPoomobile 958]

I'd love something like that, but it wouldn't be very secure having the lead trailed out of my bedroom window and across the street

[GLPoomobile 958]

Just thought I'd check something. When it struggled on Sun, I had left it with the headlights on and Sat Nav plugged in to the cigar lighter socket for the 2 minutes I was having a piss in the bushes.

 

So I've just been out to test the voltage again. With ign on (to stop the alarm arming again ) but everything else off, the battery started at about 12.4v but slowly rose until it levelled of at 13.4v I know the voltage drops momentarily and then recovers after popping the CL, but I didn't expect it to go up to 13.4v!

 

So then I stuck the lights on and the cigar lighter (just cos I didn't have my sat nav with me), and the voltage dropped to about 13v. It wasn't really moving, so I didn't see any point leaving it for 2 minutes as I doubt it would have dropped any lower.

 

Then I cranked the starter with the above still switched on. It struggled a bit, but not as bad as on Sun, and fired after a few turns. The voltage dropped right down to about 10v on the first turn, but went up a little bit again as the starter was cranking and the starter did sound stronger with each turn before it fired.

 

With the engine running, it's seeing about 16.5 v.

 

Does it sound like it could be resistance as Lagonda suggested? Although the wiring is all fairly new and clean, I'm not going to discount the possibility that there could be short comings in my workmanship.

Edited November 24, 2009 by GLPoomobile

[kyepan 291]

i would say you need one of those earthing kits off ebay.