Can you add gen2 leaf cells to a gen1 powerwall?

BigDav

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So last year I built my Gen 1 Leaf powerwall in using 28 gen1 modules in 7s4p (14s4p) format and have now got a Gen 2 battery with 88.1% SOH

I originally planned to replace the Gen1 with Gen2 cells andstart fresh with the gen2 modules

But would it be possible to combine the gen1 and gen2 cells in the powerwall? What would be the implications? Can it be done? Has anyone done it?

image_ppvues.jpg
 
Zero experience with Leaf cells.
One obvious issue is thatthe Gen2 module is essentially 2xGen1 modules stuck together (+capacity upgrade), BUT with opposing (-) and (+) terminals. See pic below.
So inserting those Gen2 modules in your current stack will probably be difficult.... would require major rework on the bus bars.


image_wlwpuu.jpg
 
You should be able to run gen1 & gen2 in parallel, chemistry hasn't changed much (if at all!).
Like ajw22 says, it's just physical layout/connection issues to solve.
 
Agree with above and I'd add that you want to keep capacities matched. For example, if your Gen1 is 14s (7 modules) at XX AH and you add a Gen2 'battery' in parallel - be sure to test the Gen2s and build a Gen2 battery with similarAH as Gen1s. No experience with these cells - but sounds like Gen2 might have more capacity - so less cells per battery?
 
OffGridInTheCity said:
Agree with above and I'd add that you want to keep capacities matched. For example, if your Gen1 is 14s (7 modules) at XX AH and you add a Gen2 'battery' in parallel - be sure to test the Gen2s and build a Gen2 battery with similarAH as Gen1s. No experience with these cells - but sounds like Gen2 might have more capacity - so less cells per battery?
The same number of physical cells inside the battery but a better battery chemistry. My gen 1 cells are around 70% SOH and my Gen2 is 88%


floydR said:
What BMS are you using?
later Floyd
Im using the Batrium Watchmon 4 with leafmons
 
>My gen 1 cells are around 70% SOH and my Gen2 is 88%
Yea - so ideally you want fewer Gen2(s) in a battery that is parallel with Gen1(s). 66ah * 70% = 46ah. 66ah * 88% = 58ah. This means that if you put the Gen2's in their own battery to parallel with the existing Gen1 - ideallyyou want 8p of Gen2 (8 * 58ah = 464ah)and 10p (10 * 46 = 460ah) so they have very similarah(s).

Alternately, if you can reconfigure the Gen1s,you couldevenly distribute Gen1/Gen2 in within a single 'battery' so that each 'cell' of 14s has similar ah.
 
OffGridInTheCity said:
>My gen 1 cells are around 70% SOH and my Gen2 is 88%
Yea - so ideally you want fewer Gen2(s) in a battery that is parallel with Gen1(s). 66ah * 70% = 46ah. 66ah * 88% = 58ah. This means that if you put the Gen2's in their own battery to parallel with the existing Gen1 - ideallyyou want 8p of Gen2 (8 * 58ah = 464ah)and 10p (10 * 46 = 460ah) so they have very similarah(s).

Alternately, if you can reconfigure the Gen1s,you couldevenly distribute Gen1/Gen2 in within a single 'battery' so that each 'cell' of 14s has similar ah.
My plan was to add the gen2 cells to each parallel pack in my existing battery by reconfiguring the busbars and layout etc
So in each parallel stack I would have 4x gen1 modules and 7x gen2 modules
 
BigDav said:
My plan was to add the gen2 cells to each parallel pack in my existing battery by reconfiguring the busbars and layout etc
So in each parallel stack I would have 4x gen1 modules and 7x gen2 modules

Very interested to see how you're going to design the busbars...seems like an impossible task without producing a spaghetti maze of wires, at least onquick thought
 
Or just create to different 48v pack's? and leaf your gen1 alone?
Just connect the gen2 at the 48v mainline???
Or is this really stupid?
It was just a thought thinking out loudfor perhaps 2 bms's?

This was my ONE cent thought, hope it will give food for your thought, i am open for comments.
With best regards Igor
 
100kwh-hunter said:
Or just create to different 48v pack's? and leaf your gen1 alone?
Just connect the gen2 at the 48v mainline???
Or is this really stupid?
It was just a thought thinking out loudfor perhaps 2 bms's?

This was my ONE cent thought, hope it will give food for your thought, i am open for comments.
With best regards Igor
Redpacket said:
Should be able to run parallel stacks eg 1x 48V Gen1 & 1x Gen2 connected at the 48V bus just fine.


I haveconsidered having 2 different packs in parallel. My BMS is a Batrium Watchmon 4 with 7x Leafmon cell monitors. Obviously I would need another 7x Leafmons for the Gen2 48v pack, but would I need another Watchmon 4 supervsior? Or would my existing WM4 do the job for both Gen1 and Gen248v packs?
 
BigDav said:
100kwh-hunter said:
Or just create to different 48v pack's? and leaf your gen1 alone?
Just connect the gen2 at the 48v mainline???
Or is this really stupid?
It was just a thought thinking out loudfor perhaps 2 bms's?

This was my ONE cent thought, hope it will give food for your thought, i am open for comments.
With best regards Igor
Redpacket said:
Should be able to run parallel stacks eg 1x 48V Gen1 & 1x Gen2 connected at the 48V bus just fine.
I haveconsidered having 2 different packs in parallel. My BMS is a Batrium Watchmon 4 with 7x Leafmon cell monitors. Obviously I would need another 7x Leafmons for the Gen2 48v pack, but would I need another Watchmon 4 supervsior? Or would my existing WM4 do the job for both Gen1 and Gen248v packs?
WM4 (+Expansion) can do up to 250longmons (e.g. leafmons are same design - network chain).https://support.batrium.com/article/90-how-many-longmons-cell-monitors-can-be-installed-with-one-watchmon I run 84 longmons - so I'm confident you can do 14 if you decide to go that way:)
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@offgrid,
Thinking out loud: i think you will need two different systems, speaking for myself: i would buy a extra wm4.
Yes one wm4 can do 250+ daisy chained longmons/leafmons, but those are different capacity's, would that not give any trouble?
Cous we are doing a lot of trouble to make every string the same capacity
Best
 
Just a heads up, chemistry has changed quite significantly between the gen1 cells and any other type of cell. The discharge curve is very top-oriented on the gen1/2 24kWh, but on gen3 30kWh and gen4 40kWh, the discharge curve works more like a "normal" lithium battery. This is because they added cobolt to the mixture on the 30kWh and upwards.
 
@Dala,
That would in play that my thoughts/feelings on a second wm was correct?
With best regards, Igor
 
Ultimately you will have a Gen1 48V battery & a Gen2 48V battery in parallel at the main positive & negative busbars.
If you decided to have two current shunt devices to track current separately, then maybe a 2nd watchmon might be needed or useful.
If you just had the one shunt then I don't see why a 2nd watchmon would help.

I have 4 x 16s batteries in parallel at the busbars via one shunt & have 32 longmon & 32 cellmon M8's & this all works together just fine (apparently!).

Maybe you could have the one Batrium system, one shunt there + a Victron BMV-712 shunt (or cheaper eBay model?) in series with each battery.
Eg Batrium does main BMS & balancing functions, BMV's just monitor for you.
 
Thinking about 2 x Watchmon vs 1 and different chemistries. I'm not sure 2 Watchmons are needed.

For me, I use Batrium (and the 84 longmons) primarily to monitor and throw shunt-trip is extreme conditions - e.g. an individual pack <3.1v and >4.15v. I don't use balance except for touch-up after 6 months or so - and its not needed on a daily basis for healthy cells! I operate in the 3.5v to 4.0v range for long life - don't get near the extremes and only do touch up balance once drifts to 100mv max difference- so 3.4 to 4.1 will still not hit the extremes.

Thinking about this... eventhough Gen1 and Gen2 might have different discharge curves and are in separate parallel batteries
1) Batrium will see / report each pack separately - which is no problem monitor wise if you know that 1-7 are a bit different discharge curve than 8-14 - there's no harm, its just info.
2) Batrium balance - you're not limited to 'top balance' you can use auto-level at various portions of the voltage curve. So I'm sure somewhere - top, middle, bottom - you can find a place to do touch-up (or initial) balancing, and then just turn it off. Balance is not needed for healthy packs on a regular basis!
3) Extreme / shunt-trip - assuming your operating in the long-life/powerrange', e.g. 4.1v to 3.4v, then even with different chemistries - its not clear that one Gen will hit the extremes of 3.0v and 4.2v (or whatever you choose) before the other... especially if you're using a long-life operating voltage range as I mention above.

In conclusion - I don't see the need for multiple Batriums even if the chemistry is different :) Ofcourse it depends on 'how different' the voltage ranges are in practice- I'll be interested to hear about it once you get info and if you share - but really, they are both lithium-ion and shouldn't be wildly different?


P.S. I think we already covered mixing Gen1 and Gen2 parallel wise - so this post is limited to the idea that they are not mixed.
 
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