Battery Technology and Best practice battery care


snydes

Moderator
Staff member
Location
Pennsylvania
There are a couple things I’d like to understand better about these batteries to give them the best chance of maximum life. They claim battery life at 1000 charge cycles which is being used interchangeably with 1000 hours, that’s assuming the average user is going to average an hour out of a charge. So that makes we wonder is it better to deplete the battery completely before charging or is frequent “top offs” not going to impact the battery life to any measurable degree? Obviously this wouldn’t be practical in many situations, but if for example I was only riding on my property a little each night during the week, I could run it down completely before charging if that was better for it in the long term.
 

Philip

Administrator
Staff member
Location
Ann Arbor, MI
From what I heard, incomplete discharges aren't bad, but incomplete top-offs could be. Like when adding some charge between the motos.

We have some resident battery technology experts here, perhaps they can pitch in. @Mark911
 

snydes

Moderator
Staff member
Location
Pennsylvania
I’d love to hear more discussion on this. Is topping off a partially discharged battery have the same effect on battery life as a full discharge/recharge?
 

Judaslefourbe

Well-known member
Location
Brisbane, CA
The only recommendation is to leave the pack at about 50-60% charge if you plan on letting the bike sit for a long time (months). It would be good to check in every now and "top off" when needed.
Other than that, the pack will protect itself from harm, so no need for special care.
 

snydes

Moderator
Staff member
Location
Pennsylvania
The only recommendation is to leave the pack at about 50-60% charge if you plan on letting the bike sit for a long time (months). It would be good to check in every now and "top off" when needed.
Other than that, the pack will protect itself from harm, so no need for special care.

Would it be better to fully discharge (if practical) before charging in regards to maximizing battery life, or does a top off from say 50% only count for half a charge cycle?

I ride mine at home during the week and don’t go through a full charge on any one night, so if it is better for the long term health of the battery to run it empty before charging I can do that. That’s basically what I’m getting at.

Thanks
 

snydes

Moderator
Staff member
Location
Pennsylvania
According to my engineers, it won't really matter. I would recommend you get used to how the bike feels when it is nearing depletion though, so you know what to expect when you're out and about.

Thanks so much. That is a great suggestion, if I run out at home it’s a much shorter push to the garage!
 

bluefxstc

Well-known member
From the electric car world, with lithium batteries it is better to not completely charge or discharge the batteries. Tesla has the ability to not fully charge their pack to extend the battery life. The Volt from my understanding only uses about 10Kw of 16Kw. Lithium cells don't have a memory function so partial charges should not be a problem. The big question is what Alta allows you to do to the battery pack. They could easily limit what you use in software, something like only charge to 90% and discharge to 10% remaining. I demoed a MX before I purchased my EX. I completely discharged the MX to where no hash marks were showing in the battery gauge. When I charged the bike it used 5.57Kw as measured by a kill a watt meter. There are some charger losses, and you have to run the coolant pump, so I think the battery probably took about 5.5kw into a completely empty pack. My guess is that Alta has some software limits on the bike to help protect the pack. Not much but I could only get about 5.5Kw into a 5.8Kw pack so there should be no problem fully charging to discharging the pack. As has already been mentioned storage is a different matter as is charging if he pack is below 32F/0C.
 

snydes

Moderator
Staff member
Location
Pennsylvania
Welcome aboard @bluefxstc ! @Oded is going to be thrilled he’s no longer the only EX guy who has made themselves known. He was feeling outnumbered I believe.

Thanks for that explanation on the battery, that’s the type of info I was looking to get!

Steve
 

Mark911

Well-known member
Location
Corona Ca
If you want to educate yourself on the care and feeding of the 18650 cell just do some google searches. The e-bike industry (as well as Tesla) has been using this cell for many years and there's quite a bit of information.
Although Alta will not say, I suspect they're using a configuration similar to the LG HG2 18650 cell on the 2018 MXR. Of course, they're using approximately 500 cells total, 5 parallel strings of 100 cells.
 

Fod

Well-known member
Location
CA
If you want to educate yourself on the care and feeding of the 18650 cell just do some google searches. The e-bike industry (as well as Tesla) has been using this cell for many years and there's quite a bit of information.
Although Alta will not say, I suspect they're using a configuration similar to the LG HG2 18650 cell on the 2018 MXR. Of course, they're using approximately 500 cells total, 5 parallel strings of 100 cells.
Well duh!
But please rephrase that for the sake of our non-Rocket Scientist members....You know triple digit SAT score folks!:lurker:
 

Mark911

Well-known member
Location
Corona Ca
The Alta battery pack is rated at 350v and 5.8Kwhs. Doing a quick conversion for a 95% efficient 30kw (40hp) 3 phase AC motors at a battery voltage of 350v results in an estimated current of about 60 amps at full power (2017 mx). The battery pack must be able to provide this kind of voltage and current.

The power source we refer to as the "Battery Pack" is actually composed of about 500 individual Li-Ion cells (the exact # is unknown). The cells themselves are an industry standard size, 18mm in diameter and 65.0mm in length, hence the designation 18650. This particular cell configuration was originally developed for mobile electronics (laptops, camcorders, etc) which required compact size and light weight with relatively high power and capacity. The approx. 500 cells constitutes about 50lbs in cells alone and makes up the bulk of the reported 70lbs pack. The remaining twenty pounds comes from cell electrical interconnects, the external frame, internal cell support, thermal management materials, the main contactor, and various BMS electronics and sensors.

Many companies’ make 18650 cells, but the best are made by Panasonic, LG, Sanyo, Sony, and Samsung. Each manufacture offers several versions of the 18650, each with different performance specifications, with some being particularly well suited for electric vehicle (EV) application. In my opinion, the LG HG2 version would be one such cell.


What makes a "good" cell for EV application? There's literally dozens of design criteria that must be considered. However, capacity (in milliamp/hours) and maximum discharge current (in amps) are the most talked about along with Energy Density. Capacity determines how LONG you can run before the pack is empty and max (continuous) discharge determines how HARD you can run before the pack gets too hot. Energy density factors in the weight of the pack/cells as well. No use having great range and power if the pack's going to weigh 200 lbs! The 18650 cell design is extremely well suited in terms of Energy Density so it usually boils down to the other two factors. Unfortunately, the two are somewhat diametrically opposed due to certain limiting chemical and manufacturing processes. In other words, cells with high capacity tend to have lower max discharge rates and visa versa. The best 18650 cells are currently peaking around 3500mah with 10-15 amps continuous, although this is constantly improving.

What 18650 cell does Alta use and who do they buy from? They don’t say. I suspect they’re using a cell around 3300mah. That would give them the advertised 5.8Kwh pack (assuming 500 cells) with a few cells dedicated to low voltage power required by the computers and other electronics plus the ability to actively balance the pack. At 3.6v per cell (typical for a 18650 cell) you’d need about 100 cells in series to achieve the bus voltage of 350v. That means there must be 5 strings of 100 cells in parallel, each string capable of safely producing 12 amps+ continuous power (about 3.8C) for a total current capability of 60+amps. Again, 2017 MX numbers.

The lack of concise cell/pack data from Alta along with the general lack of agreement in the battery cell industry and the typical misinformation associated with such a hot topic is why I suggested doing individual research on the subject. That way one can determine their own conclusions. It's not rocket science! Otherwise, follow the mfg recommendations if available.
battery.jpg
 

Fod

Well-known member
Location
CA
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!
 

Fod

Well-known member
Location
CA
Fog and I have a buddy who is a professional motocross engine builder. He has a dyno! Anyone interested in dyno charts of the mxr in all 4 maps?!?!? I'll ask him, I just don't know how he will get rpm readings.
 

Philip

Administrator
Staff member
Location
Ann Arbor, MI
I though about using a dyno too. On the second track this week I could not tell the difference between the MX and the MXR. I am planning to do a drag race this weekend to compare the two!
 

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