Jaunty

Hi guys. First post. Just last night picked up a 1 year old C300h AMG Line Estate Premium Plus in Polar White with 19" 788 AMG wheels on non run flats . Will stick some pics up when I figure out how. Coming from a Z4 so a bit of a change - but a big saving on UK company car tax and a lovely a motor. And 3 and a half years of junk in the loft can now get taken down the tip haha.

First Question - On the 3 hour drive home (A roads, M25 then London suburbs) from the independent dealer, even with the battery up in the 70% area and in Eco Mode the car would not start/stop or use electric. I even turned the air con off to give it a hand. Music, Sat Nav and lights were all on but even so I thought in that situation it should cut in at the traffic lights. This morning I didn't drive the car but I did get in and start it. The battery was at 75% I think and the diesel came straight on. I thought it would start in Electric mode if I was stationary? Maybe a bit too soon to worry - but should I?! I can try and get it booked in to MB this weekend if i need to.

(PS For those W205 owners without the hybrid, you can't actually turn of ECO start/stop on these, so it is not that.)

Thanks for any thoughts.

Bonzo the Dog

Non-hybrid W205s have the option to switch off Start Stop.

r1155

Just had same problem with my 1.5 year old car, turns out it was the vehicle battery, suggest you get it plugged in at a dealer, can only think it had lost some of its capacity.

ButteryStools

Before you go back to the dealer try pointing the blowers onto the windscreen. This time of year the start stop on my c250 won't activate unless I've had the blower on the windscreen for about 30 minutes. I am guessing the car thinks the screen is misted up.

Steve9

Jaunty, I have exactly the same observation. Car seems to run in battery only mode for maybe 10 minutes from cold, then it keeps on running on diesel mode even when stationary. The only way to revert to battery mode is to turn off the ignition and re-start in Comfort or Eco mode. Bit of a bollox really. Let us know how you get on with the dealer if you leave it in.

r1155

Just to clarify. I had the same problem with 2015 C300h, was in dealer to be fixed yesterday, fault finding indicated main vehicle battery NOT hybrid battery was the issue. Battery replaced and it seems to be working perfectly today.

Steve9

So on the basis of R1155's reply, I put the C300h on my CTEK battery charger overnight. The battery was definitely not full before connecting the charger, I can tell from the lights on the charger.

This morning I did exactly the same route as a few days ago, and it's now running in battery only mode when load conditions are reduced or when stopped.

It looks like the car senses when the low voltage battery (the regular 12 V car battery) is down, and does not allow the car to disable the engine, as there is insufficient charge to run all the auxiliary equipment, fans, steering etc. The 12V battery in a C300h will see more load than a conventional C250d, as the engine is cutting in and out while moving (not just while stationary), and also running equipment while coasting.

If you have a decent battery charger, try that. Easy to locate the positive terminal under the slider flap and the earth post is just in front for the negative; it's also detailed in the manual.

This looks like yet another aspect of the C-class, in this case hybrid specific, which has been poorly designed.

vikaspatel04

Hi there

Its been a while but I found your reply which could help to resolve the issue I am experiencing with the Merc C300h (hybrid) 2016 model.
Did you connected in the front under bonet where jump start is? or did you tried connecting at the battery itself by disconnecting all cables from the battery.
Also while using CTEK battery charge did you choose AGM mode? i m planning to buy this for charging the battery.
or can i use below

Steve9

I connected the ctek +ve to the plate under the red plastic slider on top of the battery and the -ve to the small brass looking earth post in front of the battery. I dont think my CTEK has any special modes other than a winter mode. I just connect it up and switch on.

I had the original battery replaced under warranty, I waited until it was in a fairly depleted state and not running in E mode, took it to the dealer. They said the only thing it could be is the battery so replaced it. I try to make a point of using the CTEK every couple of months to keep the 12V battery topped up to preserve the E mode. It's still going well, almost 50,000 miles on the clock now, I mostly service it myself and have had zero mechanical or electrical problems other than a blown bulb in the drivers door handle courtesy light - cheap to buy but took me over an hour to fit as you have to access from the inside removing the door card and window pane.

edit : I should have added the problem of not running in pure E mode if you dont keep the battery topped up is worse in winter time and cold conditions. Also in the summer the car should start up in E mode, in winter it will always start up in engine mode then only switch to E mode after a few miles.

vikaspatel04

Firstly thanks very much for the immediate reply.
my car is hybrid and it has a battery in the rear boot.
I also have a jump start option in the front bonnet where the engine is located. I believe it's safe to connect it on the jump start?

Thanks for the other note: I had a dashcam installed at the same time when the winter is starting hence. One day battery run out due to the dashcam left on and since I am having similar issue others mentioned i.e. not running on hybrid mode or stop-start feature while waiting in the traffic. I also notice about E mode and C mode as you mentioned.

Steve9

sorry you are correct I forgot about that - the battery is in the back. Yes I just connect up to the jump terminals in the front and never had a problem.

I also realise my terminology was inaccurate and misleading. When I referred to E mode I meant electric only mode and not the E (economy) drive select option!

vikaspatel04

thank you steve. really appreciate I have ordered the charger let's hope for the best.

vikaspatel04

Thank you steve. It worked for me. All back to normal start/stop including switching to electric started to work