Mod the Regen?

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Limey

Well-known member
Joined
Jun 5, 2013
Messages
149
Has anybody found a way to modify the regen? Specifically, I am looking to make it so that it is available at 100% (5 dots) even if you are still @ 99% charge.
 
To get better recharge, the current rate just isn't good. if i could have full access to regen immediately, i would gain at least 5% more mileage easily (my morning commute has a good amount of downhill.
 
At full regen you are stopping at full brake levels. Once the battery is fully charged to regen capacity the regenerative braking is reduced or completely turned off and only the friction brakes are used. Leaf drivers who live on high mountains have to be careful to not charge their cars fully when at home so that they will not loose regenerative braking on their way down mountain roads making it so they have to rely on friction brakes to keep speed down during their descent.

If you put full regen back into the battery when its at 99% or fully charged they you will likely overheat the battery so that it will fail more quickly. That of course would void the battery warranty since you are defeating the regen cutout that is there to protect the battery. The standard charging cycle is to taper off the charging rate the last few percentage points of the charge cycle since those last few percentage points of charge are the ones that can generate the most heat.

Really look before you leap on hacking the regen program on your Leaf unless the warranty is of no consequence to you.
 
RockyNv said:
If you put full regen back into the battery when its at 99% or fully charged they you will likely overheat the battery so that it will fail more quickly. That of course would void the battery warranty since you are defeating the regen cutout that is there to protect the battery.
I suspect there wouldn't might not be an overheat problem but rather the cells will be taken beyond their design voltage, damaging them.

Only workaround for the OP is to not charge as fully.
 
Only workaround for the OP is to not charge as fully.

Geez, where's the fun in that??! Why unplug an hour early when you can hack the car's primary systems, void the battery warranty, and risk who knows what else? Where's your sense of adventure, man?

Actually, when I saw the topic title I thought is was about making adjustments to the regen at typical (lower than 100%) SOC readings. I guess I'm just an optimist...
 
i used to charge mine to 80%, it's a 2012, and then i've get ti use regen more on my way to work.. but my commute is only 13 miles (one way) so I don't need a fully charge battery to start off the day.
 
LeftieBiker said:
Geez, where's the fun in that??! Why unplug an hour early when you can hack the car's primary systems, void the battery warranty, and risk who knows what else? Where's your sense of adventure, man?
:lol: All too true, but as you say, where is the sense of fun and adventure in such a simple solution.

Have often thought that it might be useful for those of us that desire maximum regen independent of battery state (charge level/temperature/age) to incorporate a supercap into the system. The supercap would absorb the regen and either feed it back out into the drive system or charge the batteries at a steady rate.

As always, there are a variety of trades to be made in such a design (cost/size/weight/complexity/reliability) and it would probably only address a certain subset of the population. My guess is that it's not worth doing overall, but I really hate to see how little regen is available for the first dozen or so miles on my drive every day.
 
Limey said:
Has anybody found a way to modify the regen? Specifically, I am looking to make it so that it is available at 100% (5 dots) even if you are still @ 99% charge.
I'd like to make regen work on my '12 even at SOCs not much above 70%. It's missing 2 bars and I have a feeling that's the primary culprit but missing 2 bars I really need the regen, but I get very little :( It's out of warranty so I don't really care about that so I would really like a way to bypass whatever is telling my car to only give one or two bubbles of regen even though the battery is much less than 100% SOC......
In contrast my '13S with ECO enabled(no B mode on it but ECO does give significantly more regen) I get more regen at 95% than I ever get on my '12, even at a very low SOC....
 
Limey said:
Has anybody found a way to modify the regen? Specifically, I am looking to make it so that it is available at 100% (5 dots) even if you are still @ 99% charge.

It is not possible to add energy into a fully charged battery without doing harm. End of story. Byebye :lol:

Get a newer Leaf. At normal temperatures 25-30kW regen is available at 95%. Charge to 95%.
 
It was odd to me that the Mitsubishi i-MiEV had full regen (running in "B" mode) even when the battery was full. I guess Mitsubishi realized that, on flat terrain, it takes more power to make the car go than can be regenerated. On a mountain, sure, that's not going to allow regen past 100% charge. It seems that Nissan is just being much more conservative than Mitsubishi was.
 
It should be noted that coasting is more efficient than regen, so unless you have some big hill that you're going down, it's better to coast, and just increase your "stopping" (slowing) distance if possible. As soon as I see a red light ahead, unless I'm convinced it is going to turn green before I come to it, I let off the go pedal and coast, and then regen when I know I need to slow down. When I first got the car I was getting 4.2 miles a kWh, but now I'm averaging 4.6 miles a kWh on my commute. (Average speed of 45mph.)
 
aarond12 said:
It was odd to me that the Mitsubishi i-MiEV had full regen (running in "B" mode) even when the battery was full. I guess Mitsubishi realized that, on flat terrain, it takes more power to make the car go than can be regenerated. On a mountain, sure, that's not going to allow regen past 100% charge. It seems that Nissan is just being much more conservative than Mitsubishi was.

That means 100% charge is not 100% for cells. iMiev charges to around 4.115 volts per cell. Controller may allow to go higher.
4.2V is still safe for lithium cells.
Chevy Volt uses even more narrower SOC window. Regen is totally available at "full charge".

Leaf also charges cell up to 4.135V. But controller does not allow go above that even during regen.

It is not the maximum SOC voltage that degrades cells. it is the time at that voltage.
iMiev expects you to waste that extra 0,5kWh you get if you go down the hill. Pretty reasonable.
Cell chemistry is also a player.
 
RockyNv said:
At full regen you are stopping at full brake levels. Once the battery is fully charged to regen capacity the regenerative braking is reduced or completely turned off and only the friction brakes are used. Leaf drivers who live on high mountains have to be careful to not charge their cars fully when at home so that they will not loose regenerative braking on their way down mountain roads making it so they have to rely on friction brakes to keep speed down during their descent.

If you put full regen back into the battery when its at 99% or fully charged they you will likely overheat the battery so that it will fail more quickly. That of course would void the battery warranty since you are defeating the regen cutout that is there to protect the battery. The standard charging cycle is to taper off the charging rate the last few percentage points of the charge cycle since those last few percentage points of charge are the ones that can generate the most heat.

Really look before you leap on hacking the regen program on your Leaf unless the warranty is of no consequence to you.


My issue isn't so much at 99%. But how about 95%?

On my best regen I dont even get a full 1% back. When I am at 95% battery and going downhill, it will cut me from 3 bubbles of regen to two. why do that? The battery obviously has the available storage. I could easily regen on all 4 bubbles for a long time (longer than I could ever find without using a mountain) before I need to worry about over charging the battery.

Yeah, and the warranty isn't a concern anymore. Due to the news EVs coming out with much longer range, the value of the leaf has plummeted. My wife's 3 year older car, that is beat to hell and 50k more miles is worth more than my pristine leaf.
 
You never said what year Leaf you had but newer ones(post '12) seem to have a fair amount better regen, even at a relatively high SOC. Of course like you I do wonder why even my '13S only gives a few bubbles at 95% when like you said, it should be able to take much more but I guess we'll never know why Nissan did what they did :? Like you I would like more though.
 
Leaf will adjust regen rate according to maximum charge speed.
Voltage will never go above 4.14V per cell. It will reduce regen if that happens.
After load voltage is a bit lower for short period of time. This is why more regen is available temporarily.

New Leaf has at least 3 bubbles available if SOC 95% or less and battery temp at least 4 bars.
 
Unless you re-write the laws of physics... ( please sign over your net worth to me before you do this)
You cannot stuff more water into a full bottle or more electricity into a full battery ( without something exploding).

It didn't take me 5 minutes ( living at the top of a 1000 foot hill ) to discover that there simply isn't
much regen with the batt if nearly full.

If you want to capture the energy.. don't fill the battery.

If you just Want deceleration ( drag) without using friction brakes..

You need a Very Large Resistor... one that can absorb 20Kw of energy. for whatever period you have in mind.
That mofo is going to get very hot.. and probably will be big and heavy.

Or look a lot like a good set of Disc Brakes !
 
I would love this kind of hack. my 12 leaf constantly cheats me of regen forcing me to use friction brakes more.

I am not talking fully charged here. I am talking 20% charged and its bilking me with 2 regen bubbles

the worst is when you are slowing down with 2 regen bubbles and then AFTER you have slowed too much to get much regen THEN it opens a third or fourth bubbles but now your too slow to freaking use them and once you speed back up it takes them away again. especially in the winter.

extremely annoying and I average 4.9m/kwh much much worse in the winter.
 
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