Need help

[Brian5]

I have tried to start my SL R230 but the batteries were dead so put front battery on charge last night and this morning it says 11.8 volts but no amps. So I refitted to the car and used a booster pack to jump start it but nothing key won’t turn

 

[drmw]

11.8 is I think too low to start. There is something to do with how batteries are connected - that could be a contributory factor - there will be a few mentions on the forum.

 

[rorywquin]

What says "no amps"?

 

[00slk]

I had this problem with the 55, the next morning after I purchased the car it wouldn't start, the boot battery was dead, 7 volts if I remember correctly. Had to use the key to get in.
When the 500 had a flat boot battery (Halfords battery again) it started
Volts read 6volts, but it started. Can't work that out

 

[Brian5]

What says "no amps"?

Yes mate I bought a ring smart charger and readout says 11.8v no amps??

 

[rorywquin]

Yes mate I bought a ring smart charger and readout says 11.8v no amps??

Oh just looked them up (Ring smart) - readout would be 'Amp Hours'. Don't know them but assume that the battery was not charged at all.

Sounds like a problem for R230 experts.

 

[peterws1957]

I have tried to start my SL R230 but the batteries were dead so put front battery on charge last night and this morning it says 11.8 volts but no amps. So I refitted to the car and used a booster pack to jump start it but nothing key won’t turn

Need a bit more information here Brian.
Both batteries were dead at the same time, presumably through lack of use? It's unusual for the starter battery to go flat. How old are the batteries (date will be stamped on them)? The car will start even if the rear battery is flat, providing the front starter battery has enough charge, but 11.8 volts isn't enough. What rate charger have you used and how long have you charged for and are you sure you have the correct batteries fitted? The ignition key should turn even with a flat battery or are you meaning that the starter won't turn. If the dead batteries are a sudden issue I would suspect a fault with the alternator.

 

[Brian5]

Need a bit more information here Brian.
Both batteries were dead at the same time, presumably through lack of use? It's unusual for the starter battery to go flat. How old are the batteries (date will be stamped on them)? The car will start even if the rear battery is flat, providing the front starter battery has enough charge, but 11.8 volts isn't enough. What rate charger have you used and how long have you charged for and are you sure you have the correct batteries fitted? The ignition key should turn even with a flat battery or are you meaning that the starter won't turn. If the dead batteries are a sudden issue I would suspect a fault with the alternator.

Yes both batteries flat due lack of use and I bought both direct from Mercedes in Cardiff about a year ago And when I put the key in the ignition nothing happens won’t even turn

 

[peterws1957]

So batteries are recent and correct. Both should be capable of being charged at least sufficiently to start the car. I would keep on charging the starter battery - sometimes it takes a good few hours to get enough charge into a totally flat battery. I use an 8 amp charger. Possible that you have a parasitic battery drain which has totally knackered the battery. Did you have the same problem before and that was the reason why you renewed the batteries 12 months ago?
It's strange that the key won't turn though - it may be that you have a separate problem with the ignition lock

 

[LostKiwi]

The key won't turn if the voltage is too low.

 

[peterws1957]

The key won't turn if the voltage is too low.

Ah I didn't know that - I've clearly been lucky with flatish batteries so far.

 

[davidsl500]

If its a smart charger which "Ring Smart" suggests then isn't this a battery conditioner similar to the CTek's which have a problem charging batteries that have gone too low? Does it need a normal battery charger on it to initially charge it?

 

[LostKiwi]

Ah I didn't know that - I've clearly been lucky with flatish batteries so far.

The key has to be read by the electronics then the locking motor needs to operate.
Too low a voltage and the key can't be read.

 

[rorywquin]

So batteries are recent and correct. Both should be capable of being charged at least sufficiently to start the car. I would keep on charging the starter battery - sometimes it takes a good few hours to get enough charge into a totally flat battery. I use an 8 amp charger. Possible that you have a parasitic battery drain which has totally knackered the battery. Did you have the same problem before and that was the reason why you renewed the batteries 12 months ago?
It's strange that the key won't turn though - it may be that you have a separate problem with the ignition lock

My batteries are in good nick and would easily have easily started the car today. However, but it has stood for 2 weeks (without a drive or battery charge) except to be moved in and out the garage (4 starts) - I put it on my 7amp CTEK and it took 6 hours before the battery(s) were fully charged.

So agreeing with PeterWS1957, OP charger may need a lot longer or as David suggests a boost to get the battery voltage up.

@Brian5 What does the spec. sheet of your charger say for "minimum voltage"

 

[McDonald]

My neighbours A class had to be jumpstarted on Monday, after being stationary through Lockdown. I put my C-Tek onto it for 24 hours. All is now well.

 

[peterws1957]

The key has to be read by the electronics then the locking motor needs to operate.
Too low a voltage and the key can't be read.

Yes - it dawned on me after your last post. That tricky little cheap motor.