Inconsistent ReGen/Battery behavior

camaroguy · Jan 1, 2016

Hi, its been getting a little cold here in Washington lately and I have noticed some strange regen behaviors.

I understand that when the battery is cold and I don't have max E-Cell I might not be able to regen because it can hurt the battery. The odd thing is the power gauge says I are still in almost max regen even though I can feel the car is almost coasting. It might be under very slight regen, but certainly not what the gauge is reading.

Is the gauge just telling you the amount of regen relative to the max it can regen at any given time? Has anyone else noticed this? I notice it every once in a while when the car is all warmed up too. I have not been able to figure out a way to reliably reproduce that one though.

Also I recently got around 25% battery for the first time. The e-cell gauge started to flicker off of 100%. Is this normal? I was under the impression that it didn't start limiting your power until it was around 12% battery.

JeffRay · Jan 1, 2016

Hey CG,

I have no idea what the E-Cell gauge does or is for. However, as someone who runs the battery down below 25% every week, I can tell you that the E-Cell on my 2014 definitely starts heading south slowly and then rapidly once I hit the Low Battery alert around 12%.

camaroguy · Jan 3, 2016

For others who don't know, the E-Cell gauge tells you how much instantaneous power you have on tap. Its good to know this for situations where you might need the power.

Say the motor can use 138 KW at full tilt, if the E-Cell gauge is at "full" you can use the full 138KW when you floor the accelerator. If the gauge is at say half...you can floor the accelerator all you want, but you only get a fraction of that power (ideally 50% of it if the gauge is accurate). The reasons you have E-Cell gauge less than full are as follows:
1, Battery tempuratures hot or cold (this is to protect the battery from damage due to current high current drain/regen)
2. Battery is low on power (in this case it is to help not run the battery dry)

That said, has anyone noticed the regen behavior above? The gauge says its doing heavy regen, but its really doing almost none?

JeffRay · Jan 3, 2016

CG, I would be happy to watch but unclear what to watch for. If I am at 25% and coasting, are you asking if I am feeling the braking or not? If not, please advise.

Stretch2727 · Jan 3, 2016

I have noticed the lack of regeneration when the battery is cold. It occurs sometimes even though the eCell is at 100%. There is some regen just not as much as normal.

If the gauge is off of 100% due to a cold battery I get pretty much zero regen even on D-.

My eGolf does the same thing with regen but maybe not quite a sensitive to cold as the MB. The difference is the power gauge does not move as far to indicate it cannot do regen. The MB the power gauge moves like it is doing the same amount of regen as normal when in fact there is little or none.

One comment as I was surprised by the limits on regen if you can charge the battery while it is cold. The difference is the regen can push a lot of power back to the battery. I believe for the MB it is in the range of 40-50KW. This is a lot more than any charger can do on the MB (10KW). A hair dryer is about 1.5KW. So every time you use full regen you are generating enough power to run 25+ hair dryers....a lot of power! Ok it is usually just a short time, this is why you rarely see the % meter gain. 1 min of full regen could add 1-2% to the battery but this is very hard to achieve unless you are running down the side of a long steep mountain.

I know the eCell moves off of 100% some where below 20-25% battery charge. Just not sure exactly when as I was not paying attention.

camaroguy · Jan 4, 2016

Thanks for the info Stretch. So I know there isn't anything abnormal with my B anyway.

I guess I find it odd that a German manufacture would design it this way (I suppose I don't understand why the battery percent doesn't read 112 on a full range charge either)....So as the gauge indicates more regen than is actually happening. I understand the reasons why the regen doesn't happen, they should do like your e-golf, and just move the needle less

I suspect they are just showing you a percentage of available regen that's happening (just like the power gauge). Its just unintuitive to those of us that really want to see what is going on.

This is my first Mercedes, is this typical design behavior from them? I felt in there were instances where my BMW's would even confuse people because of the tendency for complete accuracy.