Instantaneous, full battery discharge
 

Dear friends, this is a real puzzle.

The car:
Volvo 940 2.3i estate (1995), 210k mi. Regularly serviced.

The problem:
Twice now, the car has discharged its battery completely inside one minute, only to be rendered fine again with a jump start.

Instance 1 happened in seriously heavy rain round a roundabout which made me think it must be water and electricity not making friends.

Instance 2 dashes this theory as it was a beautifully warm day, car used 4x before the fault. Sat to listen to radio for fewer than 5 mins (no rain, engine not running) and it was dead to the point the radio reset itself etc. A jump and it was fine.

Battery reads great voltages cold and running but whenever this problem surfaces, the car won't even click the starter solenoid it is that weak.

I wondered if it was a loose earth so have been throwing it over speed bumps and round roundabouts and sharp corners to see if I can replicate the fault with cruel treatment; I can;t.

There seems no commonality in instances where the car chooses to fall over.

Fuel gauge only worls 2% of the time. Fresh plugs and bougicord leads fewer than 10k mi ago.

https://www.volvoforums.org.uk/showthread.php?t=313229

The above thread is realy insightful and details the tracking of a similar electricity demon.

I love this car and don't want to hear 'scrap it'. Any advice really appreciated. Stuff I've ruled out is fuel as it has happened once with the engine running, once with it just providing power to radio. Battery itself - this is healthy.

Cheers,

F

To discharge a battery that quickly would create a hell of a lot of heat!!!

Battery voltage is not really a good check on its condition.

Try to borrow a good known battery.

Well, this is the double mysterious thing - the car behaves as though it is dead (lights on dash dim, not enough grunt to even click the starter motor etc) but as soon as you show it a jump start, it is absolutely fine again.

For your advice, I say thanks and will change the battery out to see what it does and report back. It is most annoying as the problem only surfaces occasionally and seems to have no particular reason for showing up.

Cheers,

F

PS it doesn't mind being left for a few days, starts first crank etc. but has shown this fault once whilst driving and once whilst stationary with the ignition and radio on for less than 5 mins.

Possibly no capacity left in it, sulphated and charging ok but seriously depleted after initial starting.

When you fit the new battery, use a multimeter to check the alternator is charging at around 14 volts.

James.:thumbs_up:

Check your battery leads and earth points !

Agree, check and/or remake battery leads and earth points.

OK chums.Thanks for all chiming in. I have done some things today:


1) Checked battery with car switched off. Good voltage.
2) chucked a Snap on Rapid discharger on it for 15 seconds (it gets f'kin hot)
3) Car started beautifully and voltage on batteryu running is a solid 14.01v
4) checked (visually) all earth straps and cables. All seem ok and unsnapped.

Next up I will be:

1) flopping a new battery in
2) Redoing all the earth cables and maybe even adding a fresh one for good measure.

I will report back. In the meanwhile I am carrying a spare battery, jump leads and one of those little boxes of devil technology that weigh as much as a vole and claim to be able to jump start the titanic; let's see.

I do not begrudge the 210k mi car a wobbly. It is a venerable old thing, I like it and I want to see it carry on. What I do dislike is that at work, there is a fanatacism for brand new, financed, hybrids, electrics etc. Despite that, we all worship the volvo for its good reliability record and also its ability to deliver anything up to and including 0.5t of antique doors which none of the new metal can. This is an unsightly skidmark on what is an otherwise clean white y-fronted record.

Cheers,

F

If you try a new battery, ensure it is NOT a calcium/silver-calcium variety. Your alternator is NOT capable of charging this type, try a Halfords HB096, it's a traditional lead-acid battery that uses lead-antimony as a coating on the plates to help prevent sulphation. Newer batteries use silver-calcium which increases the necessary charging voltage to 14.7V MINIMUM just to start the charging process!

In fact, if your current battery is a calcium variety, this may be your problem....... :thinking:

https://en.wikipedia.org/wiki/Silver...alcium_battery

Have a read of that, you'll see what i mean. Also do some more research as you will find that 14.4-14.8V is a conservative estimate, it's normally 15.1-14.7V for a calcium battery but the point it does make in that Wiki page is that calcium batteries do deteriorate rapidly if they're not being fully charged at the correct voltage.

Sounds more like you either have a short or a bad connection, if the battery is good.

You cannot discharge the battery in 1min, something would go on fire, there would be smoke.

You need a better test for the battery than measuring the voltage, you need a load test like a high wattage bulb ideally..try not to blind yourself. Sparking the battery terminals can also work with a short piece of wire, but needs to be done carefully as if you allow it to contact for any length of time it will weld, overheat, go on fire, explode the battery etc,,.. thats a bad day.

A problem that has been reported before is the starter cable chaffing on the bulkheak, but I think that is more of a 740 problem than 940.

Try measuring the battery voltage at, say the cigarette lighter socket after measuring at the battery (with the ignition on).

Is it or is not Calcium?
 

Various posts on various threads mention calcium and antimony re batteries. The Lucas Classic and some Halfords batteries are apparently NON calcium and described as lead acid but how do we know that. All the batteries are lead acid. I’ve just had a browse in my local Halfords. Their calcium batteries are coded as HBC*** clearly marked as calcium, and their alternatives are coded HB*** lead acid and no mention of calcium. But other brands do not make it that obvious. My current Bosch battery silver 096 S5 008, which is now 5 years old, is marked as Silver, as was it’s predecessor, which lasted 12 years, but no indication as to whether there is calcium present. My current battery only shows 12.27 volts after standing overnight and sometimes less than that. I suspect that it is actually a calcium battery, but not marked as such. It still easily turns the engine over though. I’ve trawled around t’internet and have been unable to find any batteries marked as “non calcium” or “antimony” in their descriptions/specifications.

PS: I have a USB device, which also shows battery voltage, plugged into the cig lighter socket. I’ve compared it’s displayed voltage against the actual voltage at the battery whilst the engine is running and it is always 0.6 V less than the actual battery voltage. When driving it indicates a charge voltage of 13.1 or 13.2 so I presume that the alternator is providing 13.7 or 13.8. However, when the ignition is first switched on, prior to start up, it shows 11.9v or even less which would seem to indicate that the battery voltage is actually 12.5.