Maximum Safe Battery Charging voltage

[190]

Anyone know what voltage an original MB battery should be charged at in my W204. I don't want to risk any damage to the battery or electronics but I do want to fully charge it. I'm wondering what type the battery is with it being tuck away out of sight under all that plastic air ducting. Is it a sealed VRLA type.

I have an adjustable regulated charger which is usually set at 14.4 volts full charge and 13.8 volts float.

 

[GordonTarling]

Your charger will be fine. Out of curiosity, how do you plan to charge it if you can't see it?

 

[190]

Thanks Gordon,

I've been using the auxiliary +ve connection which has been provided for jump starting, so far only on the float setting.


I've been doing some research which has suggested that blue efficiency models have variable voltage regulation to save fuel and that this can result in the battery not always being fully charged in use. On top of that I only use this car 3 days per week and it stands in the garage for 4 days. I like to keep the battery topped up at all times for long life so I give it a quick charge before use.

 

[Bernie C]

Thanks Gordon,

I've been using the auxiliary +ve connection which has been provided for jump starting, so far only on the float setting.

I've been doing some research which has suggested that blue efficiency models have variable voltage regulation to save fuel and that this can result in the battery not always being fully charged in use. On top of that I only use this car 3 days per week and it stands in the garage for 4 days. I like to keep the battery topped up at all times for long life so I give it a quick charge before use.

Hi 190

The battery is located in the boot from memory with charging points in the engine bay - just thought I'd let you know

 

[MancMike]

14.4v is what the alternator generates and that's what it charges the battery with, so as said, that's fine.

 

[grober]

The plastic airducting is easy to remove. UNDO THE 2/3 clips on the top tilt slightly back and lift up- There are some locating lugs that point down and fit into locating slots on the bulkhead. Dont force anything and try not to damage the foam seals on the two duct ports- basically all the U shaped duct does is link two rectangular ports on the bulkhead

 

[190]

Thanks,

I managed to get the air ducting off and back on again.

At 84Ah and 700A EN that's one big battery to crank a little 1.6 engine. Probably original as it's a Mercedes Varta but couldn't see a date on it to check. It's a maintenance free wet cell rather than an AGM so 14.4 volts and no more will be OK as the safe maximum charging voltage.

No battery under the boot floor on mine. Maybe the later models with start stop have those.

 

[grober]

My W204 200CDI with stop start has a VARTA 80Ah 800A VRLA/AGM battery under the airduct at the front and is termed the starter battery in the EPC. The small battery in the boot is 12v/ 12ah 170Ah and termed the auxilliary battery its got a W211 number --A2115410001 and made by FIAMM

 

[notsofast]

A very interesting thread and whilst not wishing to hi-jack the thread I have been a little concerned about charging my battery in situ also. I have a battery conditioner which initially charges to 13.8v then does not charge again until the battery voltage drops to 12v which I use with great success on my other non MB cars. The only issue is that my car (W219) somehow prevents the battery voltage reaching 13.8v hence the conditioner is constantly trying to charge.
The charger acieves 13.8v if the battery is disconnected from the car. The car is used infrequently - quite often sitting for 4 weeks without running and has never had an issue with the battery discharging (when not being charged externally) so I think there is something in the car power management preventing the battery reaching 13.8v. As a consequence I do not use the conditioner at all but I am not sure it is the best way to look after the battery in my infrequently used car.
The handbook is of little help:-
"Never charge a battery while still installed in the vehicle unless the accessory battery charge unit* approved by Mercedes-Benz is being used. Gases may escape during charging and cause explosions that may result in paint damage, corrosion or personal injury.
An accessory battery charge unit* specially adapted for Mercedes-Benz vehicles and
tested and approved by Mercedes-Benz is available, permitting the charging of the
battery in its installed position."
Any ideas ot thoughts ?

 

[grober]

Mercedes rebadged approved chargers are Intelligent chargers made by CTEK. They monitor battery voltage and will supply the appropriate current/voltage to bring the battery to full charge and then move to a trickle maintenance charging regime. The smaller unit is 3.5 A but I would recommend their 5A unit as a better buy for all but the highest capacity batteries. IRRC there is no restriction to them being connected to the battery while its hooked up to the car except to connect the negative lead to the cars earthing point rather than the negative terminal of the battery. Other makes of intelligent chargers have been used on MB sucessfully but by going with CTEK you get one thats MB approved.

 

[lexman8]

IRRC there is no restriction to them being connected to the battery while its hooked up to the car

I do this all the time with no problems.

However, it's probably not wise to run the Ctek's battery conditioning programme with the battery still connected to the car.

 

[190]

A very interesting thread and whilst not wishing to hi-jack the thread I have been a little concerned about charging my battery in situ also. I have a battery conditioner which initially charges to 13.8v then does not charge again until the battery voltage drops to 12v which I use with great success on my other non MB cars. The only issue is that my car (W219) somehow prevents the battery voltage reaching 13.8v hence the conditioner is constantly trying to charge.
The charger acieves 13.8v if the battery is disconnected from the car. The car is used infrequently - quite often sitting for 4 weeks without running and has never had an issue with the battery discharging (when not being charged externally) so I think there is something in the car power management preventing the battery reaching 13.8v. As a consequence I do not use the conditioner at all but I am not sure it is the best way to look after the battery in my infrequently used car.

I've seen some strange behaviour when charging the battery in the car. What I now do as a matter of course is not to connect the charger until the car has gone to sleep otherwise there is a substantial current drain which the charger is trying to compensate for. Once things have settled down the car only consumes approx. 50mA which shouldn't have any significant impact on the charger. From my experience 13.8 volts is on the margin of charge current falling to zero and could really be considered a safe float charge voltage. 13.8 volts is not really high enough to fully charge a modern battery. One thing to determine in that respect is the battery chemistry. We have already seen in this thread that it varies from my maintenance free wet cell (I've since discovered it's a Silver calcium to be precise) and other cars with stop start which have AGM batteries and they have a higher charging voltage requirement.

Another instructive exercise is to hook up a volt meter while driving to observe what the cars charging system is delivering. I saw up to 14.6 volts even at low revs then the voltage fell off into the high 12's. I thought this indicated a fault but later discovered that blue efficiency models deliberately vary charging voltage to save fuel which can result in undercharging the battery. That explains a lot!

I suppose the bottom line is that modern cars charging systems are much more complex than the ones I grew up with and even the batteries have evolved subtlety different constructions and chemistries that have changed the charging requirements.

 

[notsofast]

I've seen some strange behaviour when charging the battery in the car. What I now do as a matter of course is not to connect the charger until the car has gone to sleep otherwise there is a substantial current drain which the charger is trying to compensate for. Once things have settled down the car only consumes approx. 50mA which shouldn't have any significant impact on the charger. From my experience 13.8 volts is on the margin of charge current falling to zero and could really be considered a safe float charge voltage. 13.8 volts is not really high enough to fully charge a modern battery. One thing to determine in that respect is the battery chemistry. We have already seen in this thread that it varies from my maintenance free wet cell (I've since discovered it's a Silver calcium to be precise) and other cars with stop start which have AGM batteries and they have a higher charging voltage requirement.

Another instructive exercise is to hook up a volt meter while driving to observe what the cars charging system is delivering. I saw up to 14.6 volts even at low revs then the voltage fell off into the high 12's. I thought this indicated a fault but later discovered that blue efficiency models deliberately vary charging voltage to save fuel which can result in undercharging the battery. That explains a lot!

I suppose the bottom line is that modern cars charging systems are much more complex than the ones I grew up with and even the batteries have evolved subtlety different constructions and chemistries that have changed the charging requirements.

Yup - I connect the charger directly to the connector permanently wired to the battery terminals, close the boot and lock the car and do not switch on the charger until the car has "gone to sleep". I guess the issue could be with the charger I am using which does not maintain a trickle charge but actually switches off and does not charge again until the battery voltage drops to 12v and brings the battery back up to 13.8v.
The variable charging is not uncommon these days though. Even my 2008 Ford Transit has this system. It will however reach 13.8v on this charger which is of course below the full design charge of 14.4v of the Ford silver calcium battery.

 

[kid-jensen]

A battery left for only 4 days without use will be fine whthout external charging..

If you're getting symptoms of a discharged battery after only 4 days, you have a battery or alternator/regulator fault. Alternatively, some other discharge path which needs investigating.

Leave the parked car alone and enjoy the additional liesure time...

 

[190]

I have no symptoms of a discharged battery other than when you hook up a charger it takes several hours to top up the battery. I now accept that a partially discharged battery is a feature of the variable charging system in my car and the fact that it takes some time to go to sleep. Once it is asleep and fully charged the battery holds it's charge very well. I know I'm being over cautious but I've always looked after batteries working from the philosophy that if you wait until there are symptoms of a discharged battery then it's already too late and some damage in terms of reduced battery life has already been done.