Battery Technology and Best practice battery care


Mark911

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What Alta REALLY needs to release is the software for reading the realtime and logged data from various controllers in the system. If you've ever used one of those simple "OBD2" (Onboard Diagnostics ver 2) interfaces to help troubleshoot your car's emissions systems you'll know exactly what I'm talking about. With access to data such as instantaneous current and voltage, motor rpm, etc, it wouldn't be difficult to write a simple script to determine torque and HP. Essentially, using the realtime or logged data as a "virtual" dyno! It would be analogous to measuring ICE parameters using OBD2 access such as airflow, injector time, and rpm to determine torque and HP but without the totally chaotic variable known as combustion to screw up the calculations.

In regards to this particular thread, having access to the battery management system (BMS) controller where individual cell data is kept would be truly eye-opening. You'd be able to see individual or groups of cell temperatures, voltages, estimated capacities, current status, etc, under both running and charging conditions. This data alone would help one understand how Alta programmed the system.

The next even bigger ask would be a communication system with WRITE authority for certain parameters. Alta, like any manufacture, must be very conservative in many design aspects for reliability and liability reasons. Since this tread is about battery packs, Alta must be concerned about individual and collective cell life and safety. Li-Ion cells such as the 18650 are like IC engines in many ways. There are MANY parameters under Alta's control even after the specific chemistry and construction are selected and the cells procured from the vendor. Lets call this particular cell a stock 250F engine. That stock cell was designed by the manufacture with certain performance and reliability claims based on specific operating conditions. For example, like an IC engine with a rev limiter set at 12,000. Want more performance, no problem, just operate the cell outside the manufactures recommended (and warranted) recommended operating conditions. Like re-programing the 250F rev limit to 14,000 rpm!

However, just like the ICE example, exceeding recommended operating conditions has risks, like a blown motor! The biggest risks for any individual cell is internal damage which leads to degraded capacity (cell life) or worse yet, thermal runaway. If you've never seen a battery pack made of dozens of 18650 cells in thermal runaway just google it, it's not a pretty sight. Cell life, while not as dramatic, is a major concern for any EV owner not looking to prematurely spend big bucks on a new pack.

But that doesn't stop tuners from modifying IC engines for "reasonable" performance improvements and it doesn't stop Alta from making similar "reasonable" modifications to the cells in their pack either. This process is always ongoing as Alta gains more user data and at each new cell design iteration. They want to push the envelop only so much, release it and see how it performs in real world conditions. That's why getting the latest software update is always important.

What parameters are typically tweaked? The BMS system controls most of these and very simply they can be divided into two categories, charging and running. When charging the BMS controls the max voltage each cell can obtain. The nominal voltage for a 18650 is around 3.6v, but the charge cutoff voltage is significantly more, 4.0-4.2v. Pushing the voltage higher means more capacity (like a bigger gas tank on the 250F), up to a point! After that all you get is a bunch of heat with the possibility of permanently damaging the cell. In any event, anytime you exceed the cell mfg recommended max charge voltage you run the risk of longterm degradation. Another charging related parameter would be max charging current. Increasing this results in quicker charge times but again you run the risk of longterm degradation.

An example of some running parameters would be cell maximum discharge rate and cell temp. Higher discharge rates is like a ported head on the 250F, more airflow. Discharge rates are typically tied to safe cell temperatures. Higher current rates typically mean higher cell temperatures just like higher HP means higher combustion temps in an ICE. High cell temperatures are associated with cell thermal runaway, definitely not a condition you want. Cell discharge rates and temperatures are closely monitored as you ride and the system will automatically limit power if these parameters exceed programmed limits. Continual operation at these upper limits also leads to the risk of longterm degradation. If you are the type of rider who's always on the verge of thermal intervention I suspect your pack will expire before someone who does not. Remember, the "industry standard" for needing a new pack is around 80% of the original capacity. It doesn't mean your bike wont work, it just means you'll only have 80% of the original range/performance. How quickly the pack dies (in charge cycles) after reaching the 80% point is another concern.

Back to the point, although Alta may not want to risk pushing the pack harder I think the owner should have the ultimate decision. With WRITE access we'd have the ability to modify certain performance parameters just like we have today with our ICE bikes. This has implications far beyond the battery pack; examples include user defined throttle response, performance maps, engine braking, etc. All done using a simple app on your phone. If pushed too hard our IC engines blow up. The risk is the same with our electric bikes. However, in the case of thermal runaway the expression "blow up" is an under statement!
 

rtf

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Wow. Thank you Mark for taking the time to write that. I, like alot of others I'm sure are new to EVs, your knowledge on this is very helpful.
 

Oded

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Great info, thanks.
Zero are using pouch cased cells and not the more familiar 18650 cylinder cells. They do it mainly for space saving.
Is there a possibility that Alta are using these kind of cells as well? Just curious..
 
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Mark911

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Someone who would like to remain anonymous (@Vagus) said that the Toshiba SCiB battery could be our next hot ticket.
Looking closer at the specs there's good and bad.
1) Excellent discharge capability, over 10X more than 18650.
2) Excellent charge capability, over 10X more than 18650
3) Higher capacity, 20amp/hr vs 18650 now over 3amp/hr (about 7X)
4) Lower nominal voltage, 2.3v vs 18650 at 3.6v.
5) Very Heavy, 510g vs 18650 around 45g per cell.
6) Very big, 260cc vs 18650 around 21cc.

Due to the lower nominal voltage you'd need around 152 cells in series to generate the required bus voltage of 350v. However, due to the higher capacity and huge discharge ability you'd only need one string instead of five. This would net a pack with a capacity about 15% greater with the ability to discharge and charge at very high rates. Very cool!
HOWEVER, factoring in the weight and volume and the story changes. Given the same capacity as noted, the Toshiba pack would weigh over 3 times the 18650 pack and be almost 4 times bigger! Wow (assuming my quick math is correct).

There's a reason companies like Alta and Tesla and many other "performance" oriented EV manufactures choose the Li-ion chemistry in the form of (or slight variations of) the 18650 cell. At least for now.
 

ElectroBraap

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It would be nice if moving forward we would be able to upgrade older Altas with the newest technology when available.

I was talking to the boys at Alta about this very thing today (we had a few conversations). I think it depends on what kind of improvements are made to the battery's moving forward. Something that can discharge faster or output more power in general will probably not be backwards compatible. This is one of the main reasons that the MX can not accept the MXR battery(wasn't designed to handle higher power output). If the improvement is in capacity, then its possible that we could potentially utilize that with older bikes. The guys at Alta said that if its possible to be backwards compatible, it will be... That's all assuming its not a totally new type of battery. That would at the very least require a totally different charging system... So... IMO (for what its worth), Its not looking good for backwards compatibility. :cry:

-Electro
 

Mark911

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I was talking to the boys at Alta about this very thing today (we had a few conversations). I think it depends on what kind of improvements are made to the battery's moving forward. Something that can discharge faster or output more power in general will probably not be backwards compatible. This is one of the main reasons that the MX can not accept the MXR battery(wasn't designed to handle higher power output). If the improvement is in capacity, then its possible that we could potentially utilize that with older bikes. The guys at Alta said that if its possible to be backwards compatible, it will be... That's all assuming its not a totally new type of battery. That would at the very least require a totally different charging system... So... IMO (for what its worth), Its not looking good for backwards compatibility. :cry:

-Electro
Who did you speak with? The only reason I ask is that, with the exception of Marc, most of the Alta reps I've spoke with don't seem to be very tech savvy. In my opinion, any improvement with basic "cell" technology should be reverse compatible. Particularly if they're staying in the same chemistry family (like in the 2018 MXR). Therefore, I suspect a good portion of the overall performance improvement is not associated with the cell itself but with more optimized connectivity and peripheral component's. Significant changes in these areas makes reverse compatibility difficult if not economically prohibitive.
 

ElectroBraap

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Who did you speak with? The only reason I ask is that, with the exception of Marc, most of the Alta reps I've spoke with don't seem to be very tech savvy. In my opinion, any improvement with basic "cell" technology should be reverse compatible. Particularly if they're staying in the same chemistry family (like in the 2018 MXR). Therefore, I suspect a good portion of the overall performance improvement is not associated with the cell itself but with more optimized connectivity and peripheral component's. Significant changes in these areas makes reverse compatibility difficult if not economically prohibitive.


It was just a few of the reps, whoever pics up the phone when I call (I talked their ear off lmao). You seem light years more educated than they did. I myself am not that educated on the topic as well. We had some basic discussions of why the mx can't be converted to an mxr cost effectively and how that could potentially be the same case moving forward.

I think I somehow missed a bunch of posts with technical information in them on the first page of this thread. I need to go back and get my learn on.

-Electro
 

ElectroBraap

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I'd like to chime in on the topic of battery care. I have been racing electric RC trucks competitively that use Lipo packs for years. I do believe(correct me if I'm wrong mark) that most lithium based batteries don't like to be discharged passed a certain point. We dont need to worry about that because the computer in the bike manages this for the rider and prevents damage.

Where we need to be concerned is storage. Someone stated above to store at 50-60% and that is consistent with what I know. With Lipo packs, being close to dead or totally full for long periods of time will cause them to wear out prematurely... possibly even swell.

I leave my bike at 60% until the night before a ride.

-Electro
 

Philip

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I think I somehow missed a bunch of posts with technical information in them on the first page of this thread. I need to to back and get my learn on.
There was no page navigation at the top in the mobile view. I thought this would become an issue, and so it did. But I gave it another thought, googled, and fixed it.

Before:
1525359805002.png

After:
1525359699570.png
 

Rix

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Awesome info! Thanks! Any tips on keeping the battery(s) healthy for the life of the bike? Any things we should avoid doing? My cell phone and laptop batterys have all lost their capacity after a year or so of use. Those I assume are like you said high capacity low discharge. Our bikes I assume are high output low capacity or maybe leaning towards a higher discharge. Maybe they last longer. Thanks for taking time to write this!
I am new here and have been the owner of a 2019 EXR for a couple of days now. However, I have been involved with hi powered electric bicycles for 7 years now. Both my FUTR Alpha and Stealth P7 have packs built from 18650 cells, specifically 30Q cells. As far as getting the most life it of these cells, there are a couple of things we can do to increase our charge/discharge cycle life rate. Never discharge the pack below 10% of standard operating charge (SOC). Even though our batteries have a built in BMS that keeps us from over discharge the pack, its not a good practice to ride our machines until BMS LVC shut down. If you don't need maximum watts for maximum distance, don't charge the battery above 90% of SOC. Grincyclery testing has shown that following these 2 guidelines, cycle life of our batteries can will be increased and can even potentially be doubled. Its also recommended to charge to 100% of SOC once every 5-10 cycles will ensure proper cell balancing. I know it was already mentioned, but if our bikes are stored for a month or so, having the battery's SOC charged at 60-70% is best. I have been following these guidelines on my ebikes for years now with excellent results.
 

Rix

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Great info, thanks.
Zero are using pouch cased cells and not the more familiar 18650 cylinder cells. They do it mainly for space saving.
Is there a possibility that Alta are using these kind of cells as well? Just curious..
Zero is using 25 and 28Ah pouch NMC ( Nickel Manganese Cobalt) made by Farasis. These cells have an expected life span rate of 5 years and are rated for 1000 cycles at 1C charge rate and not exceeding 7C discharge rate. I have not personally had any experience with the Farasis pouch cells, but people who are way smarter than me have and say they are good.
 

ElectroBraap

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Great info, thanks.
Zero are using pouch cased cells and not the more familiar 18650 cylinder cells. They do it mainly for space saving.
Is there a possibility that Alta are using these kind of cells as well? Just curious..

I have seen the packs at HQ. They are not using pouches.

-electro
 

ElectroBraap

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Ye
I am new here and have been the owner of a 2019 EXR for a couple of days now. However, I have been involved with hi powered electric bicycles for 7 years now. Both my FUTR Alpha and Stealth P7 have packs built from 18650 cells, specifically 30Q cells. As far as getting the most life it of these cells, there are a couple of things we can do to increase our charge/discharge cycle life rate. Never discharge the pack below 10% of standard operating charge (SOC). Even though our batteries have a built in BMS that keeps us from over discharge the pack, its not a good practice to ride our machines until BMS LVC shut down. If you don't need maximum watts for maximum distance, don't charge the battery above 90% of SOC. Grincyclery testing has shown that following these 2 guidelines, cycle life of our batteries can will be increased and can even potentially be doubled. Its also recommended to charge to 100% of SOC once every 5-10 cycles will ensure proper cell balancing. I know it was already mentioned, but if our bikes are stored for a month or so, having the battery's SOC charged at 60-70% is best. I have been following these guidelines on my ebikes for years now with excellent results.

Yes yes and yes. This guy gets it.

-electro
 
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