Battery woes...

[Peter van Es]

I have a few questions with regards to the battery in my 280SL. About two years ago (in August 2001 to be precise) I bought a brand new battery for my car. Because I had problems with a dead battery before, and I have an alarm system, I bought a 70AH capacity battery.

Throughout the last two years, I have had no starting problems whatsoever. I run my car once every week (except when there is a lot of rain, or snow and salt on the roads) for at least 45 minutes. Even in mid-winter, with freezing temperatures, the car starts easily and the first time.

When I run the car, the red light (charging circuit) never comes on. Four weeks ago my garage replaced the heater leavers. That means they must have taken the dashboard apart. They also serviced the car completely, and it ran fine after I got it back.

Two weeks ago I drove the car all day on a Mercedes-Benz outing (30-odd Pagoda's were there, story and photos to appear on my web-site soon). Last weekend I tried starting the car: nothing. The starter motor doesn't crank. When I switch the lights on, dim light dims to just the filaments glowing. When I measured the voltage, 9.9v at rest (i.e. no load).

I tried jump starting the car. Hooked up the battery to another car with engine running. Tried starting it, and even then the starter motor only manages to turn one crank. No noticeable change in revs on the donot battery car. So this didn't work. When I was pulling my hair out and thinking -- couldn't think of anything. Just before taking the jump leads off tried one last time and car started...

I forgot to measure the voltage with engine running -- so I do not know if charging worked. I drove for one hour. No red warning light. Got home, stopped the car. Tried starting it one hour later, nothing. Couldn't even get it jump started again.

Here are my questions:

1. is it usual for a battery to appear normal and then suddenly, in the space of one week to fail completely? I would have expected gradual degradation in starting performance...

2. with this battery in the state it is, is it worthwhile messing with acidity/density meters, with distilled water, and charging it again or would you expect it to be beyond repair?

3. I haven't gone back with my car to my garage (they are over 100 miles away), they claim that this problem could not really have anything to do with their work. Is there anything I could do to check it out?

4. what kind of regular maintenance do you typically do on your batteries?

5. Should I be using a trickle charger?

6. is there anything likely to be wrong in my cars charging circuitry or something else that could have depleted my battery in one week, that could have occurred suddenly?

7. What is the normal type of battery used in the 280SL (type / part number for different brands) and does a 55Ah suffice?

Thanks for your help

Peter


Check out http://bali.esweb.nl for photographs of classic car events and my 1970 280 SL

[George Davis]

Peter, some answers:

1. is it usual for a battery to appear normal and then suddenly, in the space of one week to fail completely? I would have expected gradual degradation in starting performance...
-Not normal, but possible.  Internal mechanical failure in the battery could cause this.  Also, failure of a diode in the alternator.  The alternator can still partially work with one bad diode, but when it's stationary, the battery can discharge through the bad diode.

2. with this battery in the state it is, is it worthwhile messing with acidity/density meters, with distilled water, and charging it again or would you expect it to be beyond repair?
-I would add distilled water if it needs it (assuming it has removable caps) and try recharging it.  If it takes and holds a charge it's probably good for a while, though likely with shorter life expectancy.  If it doesn't charge up, I'd replace it.

3. I haven't gone back with my car to my garage (they are over 100 miles away), they claim that this problem could not really have anything to do with their work. Is there anything I could do to check it out?
-I wouldn't expect their work to have anything to do with this problem.

4. what kind of regular maintenance do you typically do on your batteries?
-I buy "maintenance free" batteries, the only maintenance I do is occassionally cleaning the terminals and clamps, but I'm sure that's not the best answer.

5. Should I be using a trickle charger?
-I don't, and with 2 vehicles that don't get driven often, I don't have any problems.  However, use of a trickle charger may extend battery life somewhat.

6. is there anything likely to be wrong in my cars charging circuitry or something else that could have depleted my battery in one week, that could have occurred suddenly?
-See answer to question 1.

7. What is the normal type of battery used in the 280SL (type / part number for different brands) and does a 55Ah suffice?
-55Ah should suffice, but I understand more is better.

If you can get the battery recharged (or replaced), it would be a good idea to have the charging system checked out.  Good luck with it!

George Davis
'69 280 SL Euro manual

[Cees Klumper]

I've had this kind of sudden failure on my Pagoda battery a few years ago. In the space of a few days, the battery just completely expired without warning. The charging system of the car was not at fault. I replaced the battery and have not had this problem since.

[n/a]

i had this sort of prob with another car not a pagoda and thought it was the battery, i would always try to push the car every morning. However, even after changing the battery the problem did not disappear. It finally boiled down that certain leads with the starter had a loose contact. Checking the leads could be worth a try
yours
job

[Naj ✝︎]

Peter,
In my experience, 2 to 3 years is a good life for a battery that sees a hard life. By that I mean it is left to discharge to quite a low level because the clock/alarm would be draining it for say 2 to 3 weeks and then it gets a surge charge at say 35 to 55 amps.
They do not like these huge cycles.
I've had a Porsche for 5 years and its on its third battery. (Maybe its to do with the dodgy make of car!)
Also when you have a good alternator, battery failure is sudden. In the case of my wifes' car, it ran ok for six years (used daily) and one evening coming back from work, it just would not start. I think Cees's experience goes someway to support this theory
naj

naj
hobel 65 230SL
jalopyno 68 280SL

[Naj ✝︎]

Peter,
Also check out:
http://www.optimabattery.freeserve.co.uk/
yellow top battery
naj

naj
hobel 65 230SL
jalopyno 68 280SL

[Tom]

Hi Peter,

I had similar problems to what you describe on a good battery and, as in Job's experience (see earlier post), it turned out to be loose terminal leads on the starter.  With the expansion-contraction cycles caused by the heat of the exhaust manifold, the terminals can work themselves free over time.

Best,

Tom

[Peter van Es]

I am fixing this today and indeed I'll be buying a new battery. In my internet searches I found the following to be a very useful source of information on batteries, chargers, do's and dont's.

http://uuhome.de/william.darden/index.htm

Peter

Check out http://bali.esweb.nl for photographs of classic car events and my 1970 280 SL

[Bearcat]

ever thought of changing the voltage regulator?

[n/a]

I recently had battery charging problems. It turned out to be the alternator, who had a faulty field diode, the red warning light never went off completely,  the battery died slowly. Also the mechanical Bosch regulator had burned in contacts. I had the alternator overhauled by a retired car electrician, and replaced the regulator with an electronic one : CAR GO nr. 130675. It's 1/3 of the height of the Bosch, the installation holes match, and I paid 35 Euro's.
I also have a 77 Ah battery since 5 years now, problem free till now, (1500 km's a year).
Just last week, my son in law, had his battery die on him completly, from one day to another, in his 2 year old Alfa Romeo.

Willy, 230 SL 1967 - 220 SEb 1965

[Peter van Es]

quote:Also the mechanical Bosch regulator had burned in contacts. I had the alternator overhauled by a retired car electrician, and replaced the regulator with an electronic one : CAR GO nr. 130675. It's 1/3 of the height of the Bosch, the installation holes match, and I paid 35 Euro's.

I've thought of the voltage regulator. After installing a new battery I checked out the voltage at 1000 RPM, 2500 RPM and 3500 RPM. In all cases it is around 14 volts... which should be ok for our cars, it could be a little higher. I am thinking of installing a new voltage regulator. If that doesn't fix it, an alternator overhaul might be in order.

However, in the meantime, I checked out my lights... dipped beam and full beam, nor rear lights work. Indicator and braking lights are ok. I checked the fuses, and checked the lamp units (with an Ohm meter). That all appears ok. I therefore suspect the dashboard switch, or the floor mounted switch (although that shouldn't affect the rear lights). Given that the dashboard was out for the heating levers, I'll look into this now.

Peter

Check out http://bali.esweb.nl for photographs of classic car events and my 1970 280 SL

[Peter van Es]

Well, I've finally solved my problems. The new battery I bought appeared to be fine, but last weekend, when I tried to start my car, it was dead too! Measuring the battery voltage (2.4 volts) indicated something serious was wrong... I must have a short circuit somewhere.

I disconnected the battery, hoping that I would be able to revive this battery without having to buy a new one. With a batter this far depleted that is a worry. I bought the excellent Battery Tender product from http://www.batterytender.com Deltran, who also have excellent Battery information on their site. I hooked it up to the battery when it arrived 2 days after I placed my order, and on Thursday (Ascension day) I decided to fault find my short. Many of my friends warned me electrics were a big problem so I was apprehensive but decided to have a go.

I hooked up an ohm meter between the positive and negative terminals of the car, without the battery in place (remember, that was being slow charged by the Battery Tender).  It measured a resistance of around 2 Ohms... a clear short circuit somewhere... this would drain a battery of 12V with 6 Amps of current, depleting a 55AH battery completely in about 10 hours.

With the ohm meter connected I set about removing fuses, one by one (and reinserting them) to see when the resistance became infinite (essentially removing the short circuit). I tested all of the fuses and with fuse number 1 I found my short.

I printed the schematic diagram of the 280SL's wiring, and set about tracing the wires from fuse 1 to all the connected lamps and switches. Because the short went away when I removed fuse 1, I knew the problem was not between the battery and fuse 1 (i.e. upstream of
fuse 1).

Fuse 1 provides protection for the glove compartment light, the boot light, the entry light, the door switches, and the clock. Since my dashboard had been removed recently by my garage for the installation of new heater handles, I immediately suspected that area.

So, I had to start taking apart the glove compartment, and verify the wires for shorts. I removed the light bulb of the glove compartment and the entry light... still 2 Ohms.. I removed the clock (now 2 Ohms went up to 7) I started following the wires. I got under the dashboard under the steering wheel, and found that the alarm system was also connected to Fuse 1. And finally I found the culprit. A wire which had a series fuse in it (i.e. it was a powered +12V wire) had a bare end with a little bit of insulation tape covering it... but the tape had come loose and the bare end was touching the metal of the dashboard creating the short. The wire looked like it had powered a cassette player or a mobile phone charger in the past... I removed it and my short had gone !

Then I re-inserted all the light bulbs, and re-installed the glove compartment. The battery is now charged, and appears to have survived this depletion.

Hopefully I can now get through summer without any more of those typical "old car" things that seem to plague us owners.

Peter

Check out http://bali.esweb.nl for photographs of classic car events and my 1970 280 SL