[seschroeder]

Gentlemen:

I guess I just don't understand - please help. The battery on my 1982 308 GTSi discharges after the vehicle sits for 10 to 14 days. If driven daily there is never a problem. There are no lights on that I can tell. The radio does have a "clock" but surely that would not be enough of a voltage drain. I suspect the diode in the alternator might be bad.

When I attach a volt/omh meter to the vehicle, plus and negitive battery leads but the battery out, I get a reading of approximately .6 volts which then drops to 0 volts. I've done this twice. When I check for resistence, I would think in should read 0 without the battery, I get a reading. It goes without saying that I am not understanding something.

Removing the alternator from the vehicle doesn't appear to be the most fun one could have.

Any comments/thoughts before a remove the alternator for a rebuild??

As always, thanks in advance.

Steve Schroeder

 

[jungathart]

Hi Steve,
I recently solved similar problems on my QV.
Your battery is needing replacement. Here's how to verify:
1. with the battery in the car, jump start it. After several minutes put the voltmeter on the battery electrodes. If it reads @12 V, then your charging system (belt tension, alternator, etc.) is fine.
2. take the battery out and take it to your local "PepBoys". They can test it by drawing a load from it. If it can handle it (which I suspect it won't), then it should be OK and you might have a short somewhere that is drawing steady juice from your battery.
3. when you replace the battery, I recommend getting one of these new gel-type batteries (also available from "PepBoys"). They are maintenance free and are ideal for cars which are occasional drivers. I live in a climate where there are 6 months of winter and my car battery has to withstand sitting in the vehicle in subzero temps and still be able to provide the weekly engine starts to keep the oil and belts from settling.
4. I recommend a battery disconnect for times when you won't be running the car for more then a couple of weeks. Mine also has a little bypass circuit which allows a trickle of current to maintain clock and radio settings. You can buy this for $10.
Good luck, let us all know how you made out!

 

[seschroeder]

I had the battery checked at the auto parts store. They put a load on it and said it wasn't the battery. I am not convinced as it has been discharged/recharged many times.
With the car running the system is at 13.86 volts so perhaps it isn't the alternator.
How does one attach a voltmeter/ohm-meter to check for a drain??

Thanks for the help.

Steve Schroeder

 

[jungathart]

Hi Steve,
I am glad it's not your charging system!
A voltmeter wouldn't be able to withstand the current put out by a car battery and will overheat and fry; a battery tester is able to take the amperage. Here is what I learned from my trusted technicians: a battery may pass the load test, but depending on the device used the battery may not get stressed with the same amount of current draw that a starter may pull. Thus, even though your battery passed it may still not be able to deliver the amperage needed!
Lastly, the starter itself may be drawing too much current. Your technician can check this very easily.
Keep us all posted!

 

[Rich S]

A voltmeter measures voltage, not amperage. Doesn't matter what the output amperage is so long as the correct range for voltage is selected on the meter. In a 12 volt system (actually charges up to nearly 14 volts, with the alternator output being a bit higher) set the meter range at 20 volts.


I'm about to switch the clock in my 328 GTS for a voltmeter (a Veglia model that matches the rest of the instruments) as I wear a wristwatch, but the car has no voltmeter, originally...I don't know why, it's very useful to keep track of the electrical system! I know this thread is pretty old but someone might read the last response and assume that voltmeters can't be used (???). As for testing a battery's output amperage, in order to be able to withstand a fair amount of amperage, rather than have very heavy wiring in the meter (which would make it very large!) car ammeters have "shunts" that only run a small amount of current thru the meter itself, rather than taking the full output. The meter is calibrated to give the actual output of the system or battery. So if a car ammeter is used, make sure it has an internal shunt, rather than an external one as some older versions used. New ammeters sold at auto parts stores have wiring diagrams to indicate which design the meter is. In any event setting up an ammeter can be tricky; voltmeters are much easier, the only caveat being make sure a wired-in voltmeter is wired to an ignition-keyed circuit, or else if wired directly to the battery it'll always give a reading, even with the ignition off, and will eventually drain the battery.

 

[Bluebottle]

I am no technical expert, so I long ago gave up trying to resolve a similar issue on my '89 911. I now simply hook it up to a battery conditioner so that it stays topped up at all times - not a perfect solution, but a cheap and simple one.

As to the lack of a voltmeter, I bought a device that plugs into the cigarette lighter socket for a few pounds on e-bay. Again, not ideal, but cheap and simple - when appearance matters, I just take it out.

 

[JazzyO]

One thing that I would like to mention, in relation to the 3rd post): it has happened to me on 3 occasions in the last 5 years where my trusted specialists have tested the battery and said "the battery is perfect", but still the battery would discharge (2x on my 550, and 1x on my 458), sometimes within a day. Each time replacing the batttery fixed the problem for many years.

So I am not convinced that battery testing will necessarily tell the whole story. Whenever I have problems I replace the battery. So far it has helped every single time.


Onno



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[Rich S]

I have a suggestion: first, fit a cutoff switch to the battery post so that no matter what's still "on" it cannot drain the battery. If you don't plan on driving the car for a few days or more just turn the switch off. Realizing that the battery is underneath the spare wheel, though, maybe you could slightly rewire the battery so that the ground cable goes to somewhere a bit more accessible in the front compartment, with a bracket to hold the switch, etc. If neatly done it shouldn't be a distraction. Next, if you don't drive the car for long periods, how about hooking up a solar panel to the battery, which would keep it charged. Driving the car every so often is also a very good idea, not just to keep the battery alive!

Oops, just noticed that you weren't writing about a 328 as was the original poster. So I don't know where the batteries are on your cars, but the advice still holds.

Cheers,
Rich

 

[lucca brazzi]

308

Gentlemen:

I guess I just don't understand - please help. The battery on my 1982 308 GTSi discharges after the vehicle sits for 10 to 14 days. If driven daily there is never a problem. There are no lights on that I can tell. The radio does have a "clock" but surely that would not be enough of a voltage drain. I suspect the diode in the alternator might be bad.

When I attach a volt/omh meter to the vehicle, plus and negitive battery leads but the battery out, I get a reading of approximately .6 volts which then drops to 0 volts. I've done this twice. When I check for resistence, I would think in should read 0 without the battery, I get a reading. It goes without saying that I am not understanding something.

Removing the alternator from the vehicle doesn't appear to be the most fun one could have.

Any comments/thoughts before a remove the alternator for a rebuild??

As always, thanks in advance.

Steve Schroeder

i believe that the 308 has an analog clock, just like the 328 s do. I was having this problem many years ago, then I bought a battery tender, problem solved. The clocks in the 308 / 328 dont draw a lot of power, but its enough to slowly discharge the battery. Hope this helps

 

[Mozella]

Hi Steve,
I recently solved similar problems on my QV.
Your battery is needing replacement. Here's how to verify:
1. with the battery in the car, jump start it. After several minutes put the voltmeter on the battery electrodes. If it reads @12 V, then your charging system (belt tension, alternator, etc.) is fine.
....... snip ..............
3. when you replace the battery, I recommend getting one of these new gel-type batteries (also available from "PepBoys"). They are maintenance free and are ideal for cars which are occasional drivers. .......... snip ..........

Since nobody seems to have responded, I will.

If the OP's system is charging at 12 volts, it is NOT fine. You should have a minimum charging voltage of 13.8 volts no matter what battery you have installed.

The OP almost surely does NOT want a gel battery. They will work, but not without some potential problems which must be solved first. Plus, they're more expensive. Perhaps you're confusing gel with AGM. Here's some useful information about gel cells:

"Gel Cell Batteries are typically a bit more costly and do not offer the same power capacity as do the same physical size AGM battery. The Gel Cell Battery excels in slow discharge rates and slightly higher ambient operating temperatures. One big issue with Gel Batteries that must be addressing is the GEL CHARGE PROFILE. Gel Cell Batteries must be recharged correctly or the battery will suffer premature failure. The battery charger being used to recharge the battery(s) must be designed or adjustable for Gel Cell Batteries. If you are using an alternator to recharge a true Gel Cell a special regulator must be installed."

The special regulator alone would disqualify most cars from using a gel cell. AGM is a much better choice. By the way, you don't want charging voltage over about 14.8 (depends on temperature) if you decide to buy an AGM battery. As long as you don't overcharge them, they provide excellent service in a car and their low self discharge rate is good for us Ferrari owners who sometimes don't drive regularly. AGM's don't vent gas or spill acid under normal conditions.They cost about double that of a flooded lead acid battery, but they're worth it. AGM's are cheaper than gel batteries.