Battery And Starting Problems

[OGDB]

Hello. 


Hopefully a simple one for someone on here to answer. 

I've changed plenty of batteries in my time and have a vague idea of what's going there but I could do with knowing a bit more. 

I bought a retro vehicle about a week ago, I've been driving it all week however after the car has sat for a while, perhaps 12 hours or so, it seems the have a slightly laboured start. For example the first crank is fine and strong, and then it gets far more laboured, before it gives another firm crank and then it usually fires into life. Today I drove the car to work, it started fine, drove it to work, parked it up and checked everything was off. I then came out this evening to come home and I got the usual laboured start, then tick tick tick, thing wont start! I called the missus who came up and I jumped the car which started instantly, no hesitation at all. I drove the car home and turned it off and it started straight away, no hesitation. 

I've just gone out with my tester and got 12.6v with the car off and 13.7/8v with the car running which as far as I see it is fine. However from what I am aware this doesn't confirm the battery is 100% healthy, is that correct? I understand that you can drop test the battery, I presume this measures a voltage drop over a period of time idle, is that correct? 

The car had been owned by the previous owner for around 5 years, with less and less use in the recent years. The previous owner told me that it would possibly be parked up for 4 months at a time, then run around for a weekend before being left for another number of months. I can only presume that the battery has started to deteriorate over the years of this happening. When I look at the battery it seems to be a dated, no name item. 

I recently had a T4 van, I suspected the battery was a dud so threw a new one in. Annoyingly it turned out to be a duff starter motor, so even more expense was paid out, but the thing started wonderfully. I am ruling out the starter motor here as when the car was jumped it started superbly. Is that a fair conclusion to make? 

I realise that there could possibly be a slight voltage drain coming from somewhere. Is there any way to confirm or eliminate this? I suppose I could read the voltage after 12 hours with the car sat idle, take a reading. Then disconnect the battery for another 12 hours and take a reading then to see if there is any difference?

I understand that one or more of the plates in the battery could be caked up with fuzz. Could this effect the CCA of the battery and make it read the correct voltage at idle and when running but actually make the battery useless? Would taking a battery voltage reading whilst the car is cranked over help with any sort of diagnosis? I think my local battery specialist had a bit of kit that could tell you all of the vitals, however with out reading it myself I find myself a bit hesitant to believe what they say.  

Any help on the subject would be fantastic! 

Thanks in advance. 

[sowen]

Stick the multimeter on it when it's cranking, sounds like there'll be a big drop and it's lost it's capacity.

[ChasR]

IME there are only really two ways to tell if a battery is bad and although they give more information, it's not always a perfect one:

• Drop-Tester ; This effectively shorts the battery with a big resistor, and see what the voltage drops to, and from the gauge, it will show whether it is dead or not-They are around £30-50 to buy
• Capacitance Tester : These can be more thorough, and can tell if the bettery is 'truly' charged.

I bought a cheap capacitance tester which has come in very handy; I bought a Foxwell BT-100 which I've now used a few times over the years, and it cost £40. Yes, a £200 Yuasa one is probably better but to be fair, the readings of mine haven't been miles off, and I've compared it to a few testers out there now, including the workplace .

Another thing to bear in mind is, if this is your 944, they are never the quickest turners on the key anyway. Most people IME will go cheap on the battery in either the brand or the capacity (I've seen them with a 063 battery, which TBH, is too small for a daily car or one used on short journeys) as at one point they weren't much cash, and as such, that can give issues. So I'd check the battery size too. From memory, it should be a 075 battery at least in there or preferably a 096. I know my Turbo never stuggled to start on a 550 CCA battery.

Another thing to remember is if your car still has a factory alarm installed, that can cause issues too. Porsches were known for the factory alarm having a drain present, hence many have been bypassed for this reason. It may be worth you checking whether you have a drain present.

[colnerov]

Hi, Is it the same if you disconnect the battery over its periods of rest? Is there a spark if you flash the power lead on and off the connection on the alternator?

Colin

[Phil H]

When you jumped it, did the connect the jumps leads to the battery terminals?

Curious if you’ve got a poor battery clamp (or earth if it’s a braided type).

[comfortablynumb]

Sounds like a sporadic earth fault to me

[vitesseefi]

Sounds like a knackered battery to me. One that is substantially sulphated by being left too long in a partially discharged state. This leaves it capable of showing a good voltage but having only a very small reserve capacity. I’ve just replaced a similar one that was giving very similar symptoms.

Nick

[OGDB]

Thanks very much for all of the replies and sorry for my lack of response. I have been doing some investigation and this is what I have discovered. I would multiquote and reply to you all but I don't know how! ChasR yes this is my 944. 

The battery was charging at 13.8v and when the car was shut off and left for the night the battery was showing 12.6v. The next morning I came out and the battery had dropped down to 12.2v. The car wouldn't start. I then came home from work checked it again and the battery had dropped again to something like 11.8v. At this point I decided I would remove the battery and replace it with one which I knew was good. I took a battery out of my R32 and wacked that in. The battery is a 096 70AH with 640CCA. I put this in and drove around all day Sunday with no problems, all was good. Was starting a whole lot better as well. I parked the car up Sunday, came out Monday morning and the damn thing has dropped to a point where it will continuously crank the engine... but not fast enough for the thing to fire over. 

So at this point I have. 

• Checked the earth to the car, all seems good with a good connection. Also checked the battery terminals which are clean and have a good connection. 
• Left a jumper lead from the battery to the body in an attempt to rule out any poor earth faults. 
• Checked the charging voltage which is good at 13.8v.
  
• Disconnected the new battery over night to check for a voltage drop. The voltage drops significantly when the battery is connected to the car, there is no voltage drop over 12 hours when the battery is removed from the car. When connected to the car it is dropping 0.5v every 12 hours it seems.
• I have checked everything in the car is switched off when the car is left over night.

At this point I think, and please point me in the right direction if I am barking up the wrong tree here, and it was mentioned by some of you earlier in the thread here, but I think that there is most probably a parasitic drain somewhere in the system. Problem is where! Can anyone point me in a direction as to try and pin down my drain? Is there a method that can help pin point the problem? I've been very lucky in my time and never had a problem like this and the fear of walking back to your car and wondering if the damn thing will start sucks! 

I am more than happy to chuck a new, decent battery in the car, but I don't want to be charging the thing up every other day with this persistent drain. 

The car in question is a 1989 Porsche 944 2.7l. 

Thanks in advance for any help. 

[Phil H]

That’s some heavy drain there! Got to be an Amp or so?

Favourites:
Courtesy light (underbonnet, glovebox, boot?)
Radio
Alarm or immobiliser (especially old ones you don’t know about) - mentioned by ChasR above.
Alternator

You need an ammeter in circuit with the battery, then start pulling fuses and see which circuit stops the current flowing.

[nomad]

Sept 26, 2019 19:19:33 GMT colnerov said:

Hi, Is it the same if you disconnect the battery over its periods of rest? Is there a spark if you flash the power lead on and off the connection on the alternator?

This ! Go for a drive, disconnect battery earth when you stop and measure battery voltage. measure again a couple of hours later. Leave overnight or more and measure again.!if there's a big drop the battle is dead.
If voltage still looks  OK, connect battery leads,, leave overnight etc and recheck. If there's a big drop you have a something draining the battery.

[colnerov]

Oct 2, 2019 12:44:43 GMT nomad said:

Sept 26, 2019 19:19:33 GMT colnerov said:

Hi, Is it the same if you disconnect the battery over its periods of rest? Is there a spark if you flash the power lead on and off the connection on the alternator?

This ! Go for a drive, disconnect battery earth when you stop and measure battery voltage. measure again a couple of hours later. Leave overnight or more and measure again.!if there's a big drop the battle is dead.
If voltage still looks  OK, connect battery leads,, leave overnight etc and recheck. If there's a big drop you have a something draining the battery.

Hi, Yes, if there is a drain one of the things to check is that a diode may have gone bad in the alternator and is leaking to earth.

Colin

Edit: Oops already mentioned.

[jpr1977]

Oct 2, 2019 4:48:02 GMT Phil H said:

That’s some heavy drain there! Got to be an Amp or so?

Favourites:
Courtesy light (underbonnet, glovebox, boot?)
Radio
Alarm or immobiliser (especially old ones you don’t know about) - mentioned by ChasR above.
Alternator

You need an ammeter in circuit with the battery, then start pulling fuses and see which circuit stops the current flowing.

Phil beat me to it, this is the best way i have found of beginning to trace faults like this, then its a question of checking the individual components on the suspect circuit.

[ChasR]

What the rest have said.

Put a multimeter in line in with the negative feed and see what the drain is. At that point, you can:
-Start pulling out fuses and see how the drain is affected
-Disconnecting boxes, like the head unit (depending on how it is wired up) or aftermarket boxes/immobilisers. As said, Porsche factory alarms were known battery drainers.

My RS Turbo had a similar issue, except it turned out to be a clock that was wired incorrectly the light was always on. That was enough to kill the battery over a length of time. As soon as I removed the feed, it stopped.

[OGDB]

Thanks again for all of the help in here. I've been very busy with work so have been trying to do a little bit of investigation on the car little and often. Anyway. I started by driving the car to work, once at work I removed the negative battery terminal as previously suggested. after 10 hours the battery started at 12.6v and 10 hours later was still at 12.6v. Over the last 3/4 days I've been driving the car daily and disconnecting the battery when its sat idle, its started fine every time. Problem is the battery is in the boot and when the battery is disconnected I cant open the boot to reconnect the battery, so I have had to climb through the very small boot to reconnect the battery which is getting very old very fast. 

Oct 2, 2019 22:06:27 GMT ChasR said:

What the rest have said.

Put a multimeter in line in with the negative feed and see what the drain is. At that point, you can:
-Start pulling out fuses and see how the drain is affected
-Disconnecting boxes, like the head unit (depending on how it is wired up) or aftermarket boxes/immobilisers. As said, Porsche factory alarms were known battery drainers.

My RS Turbo had a similar issue, except it turned out to be a clock that was wired incorrectly the light was always on. That was enough to kill the battery over a length of time. As soon as I removed the feed, it stopped.

I may have misunderstood what you've said here but let me explain what I've done and correct me where I've gone wrong if you could please. 

With the car turned off and everything switched off in the car and the key removed I disconnected the negative battery terminal from the battery, set the multi-meter to the correct setting and read between the negative terminal on the battery and connected the other probe to a good earth location on the chassis of the car. Is that correct? 

With this done I was getting a fluctuating reading on the meter, it seemed to float around 12v. However this floating around may have been due to my unsteady hand. Does this suggest I have a 12v drain somewhere in the system? This seems like a significant drain. 

In regards to what's fitted to the car it seems as though there is a after market alarm and immobiliser, the code reader is still present in the dash but is redundant, I am tempted to cut the whole lot out but don't want to immobilise the car. There is no head unit or audio of any kind fitted to the car. Interior light is always off and there is no bulb in the boot. the central locking seems partly inoperative. The passenger door locks off of the key but it does not work from the door. Also if I unlock the boot and turn the key to the 9 o'clock position to open the hatch the motor can be heard running in the boot. 

Is it possible to turn everything off in the car, have the key removed and test across the fuse board if voltage is being drawn? for example, remove the fuse on suspected circuits and see if a draw is there? 

Thanks in advance for any help. 

[nomad]

A basic multimeter can measure *volts* also *amps*
So far you have (correctly) been meausing volts.

To check amps -
leave one battery teminal (positive) connected, disconnect the other (negative)
Set the multimeter dial to read amps, connect 1 probe to the negative battery terminal, connect the other probe to the battery lead you disconnected.
Do not turn on the ignition or try to start the car (or you risk damaging your meter ! ) - you are trying to trace a very small power drain when the ignition is off.

Ideally your meter should show zero amps, normally you will see a small reading (milliamps).
Then just try to find what is taking the power, remove each fuse in turn - if the reading drops a lot you have identified your "problem" circuit.

Hopefully the diagram makes sense

[nomad]

Oct 4, 2019 18:10:43 GMT OGDB said:

I may have misunderstood what you've said here but let me explain what I've done and correct me where I've gone wrong if you could please. 

With the car turned off and everything switched off in the car and the key removed I disconnected the negative battery terminal from the battery, set the multi-meter to the correct setting and read between the negative terminal on the battery and connected the other probe to a good earth location on the chassis of the car. Is that correct? 

With this done I was getting a fluctuating reading on the meter, it seemed to float around 12v.

You're very close but the meter should be reading amps, I suspect you have it set to volts (which is why you are seeing a reading of 12 volts)
Suggest you set the meter to "Amps" and repeat the test   

[Phil H]

Most meters can read up to 5 or 10A but you’ll probably need to move one of the leads to another hole. They normally draw lines on the front to guide you.

[OGDB]

Oct 4, 2019 19:33:48 GMT nomad said:

A basic multimeter can measure *volts* also *amps*
So far you have (correctly) been meausing volts.

To check amps -
leave one battery teminal (positive) connected, disconnect the other (negative)
Set the multimeter dial to read amps, connect 1 probe to the negative battery terminal, connect the other probe to the battery lead you disconnected.
Do not turn on the ignition or try to start the car (or you risk damaging your meter ! ) - you are trying to trace a very small power drain when the ignition is off.

Ideally your meter should show zero amps, normally you will see a small reading (milliamps).
Then just try to find what is taking the power, remove each fuse in turn - if the reading drops a lot you have identified your "problem" circuit.

Hopefully the diagram makes sense

That’s fantastic, thank you very much! As you can see I’m far from an expert but I have used my tester for testing ohms so sure I can hopefully figure it out the read amps.

I will test it in the morning and report back with my findings. Thank you very much indeed for the help.

[OGDB]

I am a little stumped here, this is the tester I have, what setting do I use to read Amps? if it reads amps at all.

www.lasertools.co.uk/product/6228

www.lasertools.co.uk/items/PDF/Products/6228_Technical_Instructions.pdf

Thanks

[Phil H]

Yes it does - leads go in the “10A” and “COM” holes and the dial goes on the 10A setting.

Don’t forget to put the lead back in the normal hole after doing the current measurements otherwise Sod’s law says you’ll blow the meter (fuse) next time you use it...