HV battery votlages/tests

Faults and Technical chat for the Honda E
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EEEE
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Post by EEEE »

EEEE wrote: Thu Dec 21, 2023 10:56 am

So what does the voltage discharge curve tell us? We need to find some data sheets!

I believe the cells in questions are Panasonic UF261591TA NCM622 51Ah. NCM 622 being the specific chemistry composition of the cells. Other details about the cell sizes and weights can be found in the link.
( source https://pushevs.com/2020/07/03/modern-p ... ery-cells/ )

I cannot find data sheets for the cells - I suspect these are only available under NDA.

I also cannot find a generic rule of thumb for cell capacity/life vs DoD (depth of discharge). What I did see is that charging ncm622 to 4.3v /4.4v / 4.5v would decrease the lifespan, so charging to 4.15v seems conservative. Likewise, some discharge tests go well below 3v, but the lifespan is only measured in the 100s of cycles range before significant drop off in capacity.
From the opening post. I can't remember where i found the cell part number from, but it no doubt came at the end of many hours of trawling the internet.

I couldn't find a discharge curve for NCM622 cells, or a spec sheet for any cell of this chemistry, so I never came to any conclusion about how deeply discharged the cells are (and thus work out if we are all worrying about battery degredation needlessly, which I suspect we mostly are).

I doubt that largely improved cells will be made in the same form factor. It stands to reason that if there was a precedence for improved cells in the same form factor, we would have seen it already, rather than the form factor changing over time (which is what seems to be the case). Perhaps there will be replacement cells in future that are slightly better (5%-10%?).
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FDAD
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Post by FDAD »

EEEE wrote: Wed May 08, 2024 12:46 pm
I doubt that largely improved cells will be made in the same form factor. It stands to reason that if there was a precedence for improved cells in the same form factor, we would have seen it already, rather than the form factor changing over time (which is what seems to be the case). Perhaps there will be replacement cells in future that are slightly better (5%-10%?).
Everything is firmware... a new battery could be made from scratch with totally different cells.

To put it simply, the car sees voltage for power/range, a more difficult approach would be changing to 800v architecture for example.

Besides that, anything that translates the battery package specs successfully to the BCM (given a theoretical approach that that wouldn't be changed) would work.
Even using the same insides with different cells:

New BYD BLADE battery:
Chemistry = LiFePO4 (LFP)
Capacity = 202 Ah
Nominal Voltage = 3.2 V
Maximum Charging Voltage = 3.65 V
Charging cut-off voltage = 3.8V
Energy Content = 646.4 Wh
--------------------------------------------------------
Panasonic NCM
Capacity: 51 Ah
Nominal voltage: 3,7 V
Energy: 188,7 Wh
Chemistry: NCM 622

In this case there is a large variation in voltages, that would require adjusting the maximum and minimum voltage parameters in the BCM.
a more suitable approach would be:

ECO POWER C1-NCM58W

Voltage Max. 4.35V
Voltage Nominal 3.67V
Voltage Min. 2.75V
Current Standard charging current 58A
Maximum Pulse Discharging Current(≤10s) 450A
Volumetric 508.5Wh/L
Weight 0,920Kg

This would increase capacity with minimal effort.

Or even better (given the weight increase):

Samsung SDI94 Li Ion 3.7V 94AH NMC NCM

Nominal Capacity = 94Ah
Nominal Voltage = 3.68 V
Energy = 345Wh
Weight 2,1Kg
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EEEE
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Post by EEEE »

The problem with the stance of 'its just firmware' is that in a tesla, the firmware is all centrally controlled and managed by a single corporation. The honda e will be a mish mash of vendors, honda may not even own/control the firmware of half the modules (they are the customer , not the owner/programmer).

The problem is just one of economics. The more you have to change, the more systems you need to understand/control/reprogram to make it work.

The more barriers there are , the less likely it is someone will build a product to replace the original battery.

You would have to stick to the shame shape pack (or even re-use the original) which limits you to same cell size in reality as you need to get multiples of 96 cells to sit right and interact with the BMS nicely.

Changing chemistry only gives you more trouble in reality.

The BMS system is not the charger. The charger would need reprogramming. That might contain cryptographically locked firmware? Who's going to unpick that? they only sold 10k units worldwide? The market is small, so the investment in breaking/controlling systems is not worth the return.

Then you've got the integration testing, perhaps the new cells put out more heat, can the cooling system deal with that?

I cannot see anyone offering new packs for the e. The best we can hope for is like for like replacement of the cells, giving only a small step improvement (eg, re-cell the original pack with same chemistry or near-same chemistry which will only give marginal improvements).

It will not be in hondas interest to help sustain the car or improve it after they have shipped it (why improve an old car when they can sell you a new one?). That limits what is possible as a privateer or small business offering in my view.
'21 e Advance - Charge Yellow - E1702RR alloys
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FDAD
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Post by FDAD »

EEEE wrote: Wed May 08, 2024 2:09 pm The problem with the stance of 'its just firmware' is that in a tesla, the firmware is all centrally controlled and managed by a single corporation. The honda e will be a mish mash of vendors, honda may not even own/control the firmware of half the modules (they are the customer , not the owner/programmer).

The problem is just one of economics. The more you have to change, the more systems you need to understand/control/reprogram to make it work.

The more barriers there are , the less likely it is someone will build a product to replace the original battery.

You would have to stick to the shame shape pack (or even re-use the original) which limits you to same cell size in reality as you need to get multiples of 96 cells to sit right and interact with the BMS nicely.

Changing chemistry only gives you more trouble in reality.

The BMS system is not the charger. The charger would need reprogramming. That might contain cryptographically locked firmware? Who's going to unpick that? they only sold 10k units worldwide? The market is small, so the investment in breaking/controlling systems is not worth the return.

Then you've got the integration testing, perhaps the new cells put out more heat, can the cooling system deal with that?

I cannot see anyone offering new packs for the e. The best we can hope for is like for like replacement of the cells, giving only a small step improvement (eg, re-cell the original pack with same chemistry or near-same chemistry which will only give marginal improvements).

It will not be in hondas interest to help sustain the car or improve it after they have shipped it (why improve an old car when they can sell you a new one?). That limits what is possible as a privateer or small business offering in my view.
I understand perfectly what you're saying but without investigation it could be a storm in a cup of water.... For every problem you pointed out the solution may be simpler than what it seems.
Even the charger could be kept the same if you don't exceed the charging rate of the new ones...
Honda E advance [Modern Steel Metallic] 8-) [DELIVERED JULY 2020] - 85 000Kms + ✌️🎂
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