Regen - It effects on the traction battery - also deceleration

[ArtInCT]

I was poking around the forums and ran across a wonderful set of spreadsheets that are/were used to capture raw data on recharging the traction battery and the long range effects on recharging styles as well as SOC State of Charge top end percentages.

Those spreadsheets are here, and there are many workbooks in the main spreadsheet --> Tesla Battery Survey (old name MaxRange) - Google Sheets

After a bit of reading and trying to understand the results of these efforts I began to notice that folks were gathering data on recharging efforts, rates and even their use of SuperChargers.

What I suddenly realized is that the data did not account for the effects of many, many small and large regen recharges that occur on each trip in a Tesla Model S.

Also there are two rege "modes" each in itself varies the deceleration rate.
I do not know what the deceleration rates of regen are in -g force... perhaps somewhere between -.05g and -.15g would be my guess.
I also wonder if Tesla Motors engineers arrived at the -g force based upon user comfort or max power regenerated in Kw.?

Also do the different size battery packs accept different regen rates.... or is the regen kW to a 60 kWh pack the same at to the new 90 pack?
Also does regen have any negative effects on the Tesla drive train or its components?

I just do not know the answers to these questions nor are they talked about much.

So I guess I should stop rambling... but simply say that enroute regen could have some impact on traction battery health.... good or bad... and it seems to not be tracked by anyone as we have no metric tools to do so.

Lastly... I am rather cranky that my auto spell check keeps changing regen to region...:wink:

ARTinCT

 

[brianman]

enroute regen could have some impact on traction battery health.... good or bad... and it seems to not be tracked by anyone as we have no metric tools to do so.

I wouldn't say that. With the REST API streaming data, in theory you could track this reasonably well as long as you stay in cell coverage areas.

 

[ArtInCT]

I wouldn't say that. With the REST API streaming data, in theory you could track this reasonably well as long as you stay in cell coverage areas.

Oh, that is nice about the REST API I have not really looked into that much at all. I think the Visible Tesla IOS software project is based on the REST API? However, does the Model S UI display allow for the car to divulge the number of regens and the kW's fed back into the main pack for a given time frame or trip or period? I do not think it does on the screens I have seen. But I do not own a Tesla yet so perhaps there is some display I am unaware of...

That said... How does one learn about the REST API? Is there a white paper on its use and the general architecture? I hear it uses the Tesla Servers to pole the Model S...

So from what I can deduce TESLA API CALL FROM DEVICE -- IP --> TESLA SERVER ---- 3G 4G ----> MODEL S ----> ???

 

[brianman]

Model S REST API

REST API Tools and Apps - Tesla Motors Club - Enthusiasts & Owners Forum

 

[Andyw2100]

but simply say that enroute regen could have some impact on traction battery health.... good or bad... and it seems to not be tracked by anyone as we have no metric tools to do so.

I could be mistaken, but my guess would be that no one has bothered to attempt to track regen's impact on battery health because unlike charging habits, which are easy enough to tweak, no one is really willing to radically change the way they drive in an attempt to eke an extra little bit of longevity out of the battery.

As an exaggerated example, even if it was determined that using the low regen setting would extend battery life by 2%, the amount of money you'd be spending in wasted energy over the life of the battery, just to save that 2% battery life would almost certainly dwarf the benefit from extending the life of the battery. (And that doesn't take into account the additional money you'd be spending on brakes.) I say that this example is exaggerated because when we look at the typical rate at which the batteries are degrading, it's hard to imagine something like decreased regen having a measurable impact at all.

If you somehow determined that more regen was better for the battery, there really isn't anything you could do to generate more regen, beyond learning to drive as efficiently as possible, which you're going to do anyway.

Seriously--I don't think you should worry about using regen!

 

[beingpaulp]

I live at a pretty high elevation (3000ft) and everyday drive down to sea level. What I've noticed is the following:

1 - I regen around 5-7% on a 85D leaving home and going out (downhill)
2 - because of #1 I try not to charge above 80-85% at home
3 - I also freely use the A/C, heater, seat warmers, etc. on max when leaving home
4 - The most interesting thing which I've noticed is that my battery seems to get out of balance pretty badly. I'm not sure what others notice, but I try to do a 100% full charge at a public charger every other month, it took me over 2 hours to balance the pack the last time! (2 hours after it reached 100%)

I suspect my specific regen routine doesn't charge the battery evenly, or maybe it's the daily up (high discharge) and down (high regen) that make the battery get out of balance, either way... I would recommend more frequent balancing if you regen alot.

 

[sillydriver]

Things are complicated by the fact that the power regenerated by decelerating at a given rate varies linearly with speed. A given deceleration under regen at 60 mph charges the battery twice as fast as at 30.

 

[hybridbear]

4 - The most interesting thing which I've noticed is that my battery seems to get out of balance pretty badly. I'm not sure what others notice, but I try to do a 100% full charge at a public charger every other month, it took me over 2 hours to balance the pack the last time! (2 hours after it reached 100%)

I suspect my specific regen routine doesn't charge the battery evenly, or maybe it's the daily up (high discharge) and down (high regen) that make the battery get out of balance, either way... I would recommend more frequent balancing if you regen alot.

How do you determine that your pack gets out of balance?

 

[CHG-ON]

I am very interested in learning about this and how to rebalance. I have read several things. But I haven't seen anything that would be definitive.

Thanks.

How do you determine that your pack gets out of balance?

 

[beingpaulp]

I am very interested in learning about this and how to rebalance. I have read several things. But I haven't seen anything that would be definitive.

Wikipedia has a great explaination: Battery balancing - Wikipedia, the free encyclopedia

Basically if one "cell" or in the Tesla case "group of cells" in series is lower voltage than the others, it ends up getting used more. You don't fully charge it, and you discharge it more than the others. This makes it the weak link in the series chain.

From what I've read, if you do a range charge to 100%, at the end, it will attempt to charge the lower voltage groups of cells. The only data I have is that it is taking longer and longer for me to do a 100% range charge. It's painfully obvious because I never charge fully at home and I'm always out somewhere and waiting for it to finish!

 

[FlatSix911]

Thanks for the interesting article https://en.wikipedia.org/wiki/Battery_balancing

What is the recommended frequency for a 100% charge to rebalance the pack?

 

[Cottonwood]

Thanks for the interesting article https://en.wikipedia.org/wiki/Battery_balancing

What is the recommended frequency for a 100% charge to rebalance the pack?

BTW, relative to that article, the MS uses passive balancing with resistors. Those resistors are small enough relative to the battery capacity, that the balancing can take a day or more if the pack is out of balance. You do not have to leave the MS charging that long, the car remembers the balance state after the 100% or almost charge, and then passively balances over the next many hours.

I do a 100% charge just before each long trip that will require charging before I get home.