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[Low On Cash]

I thought it would be a good discussion topic regarding proper long term battery storage and some of the options to help preserve our cells. Zero’s “Leave it Plugged In” recommendations has created considerable uncertainty regarding proper procedures during winter or non-use storage.

I’ll also discuss a commonly used “Self-Discharge” feature which self drains the cells to a lower SOC after a period of time, this is used on lithium cells for the aerial drone industry and may be advantageous to Zero owners as well.

Zero’s Plug & Leave Recommendations 

Regretfully, I “Do Not” recommend using Zero’s storage recommendations outlined in the manual of just leaving the battery on charge and unattended. This is not a safe practice and certainly not in the best interest of protecting your home or bike.

For safety reasons - Or when ever possible, lithium cells should never be left on charge unattended, since in the event of a battery management system malfunction and failure to limit charging, it could result in catastrophic results and a fire.

Battery Management System - As we all know, the only safety valve to prevent under or over charging of the pack is the battery management circuitry. This system is not perfect and if a failure occurs there no redundant backup system to monitor battery status.

Speaking for myself, it is not even imaginable to leave my bike on charge and head down to Florida. The battery pack in our bikes is like a small bomb. I’m sure most of you have seen what happens with these electronic cigarettes when just one small cell ignites, so you can imagine a Zero pack.

Winter or work storage for me means unplugging everything possible to prevent the unknown from happening. Having my Zero’s battery charged is far less important that the safety of my home. Even for every day charging, I always attempt to charge when I get home and in most cases before bedtime she’s back up to 100%. While I understand this schedule might not work for everyone, if you have to leave the bike plugged in at night or when not home, there is a risk, so use caution.

Voltage Spikes - There is always concern for voltage spikes in the power grid which could damage the charger or BMS. In addition, spikes may cause the processor to freeze with uncertain results causing an overcharge situation.
During a lightning storm, a close proximity strike could easily destroy not only the charging circuit, but also spike the bikes processor and circuitry. Therefore any time a lightning storm is near you’ll want to immediately unplug the 110 v cord, of course this is not possible when if the bike is unattended!

Uninterruptible Power Supply System

If for any reason you have to leave your bike plugged in and unattended, you can provide some additional protection with the use of a uninterruptible power supply system. While the battery back up feature will be minimal, it will still provide momentary inverter power during spikes in voltage as well as “open the circuit” in the event of a strike.  Keep in mind, if a lighting spike gets in your bike, the damage could far exceed the cost of a UPS so its a good investment. I presently use these UPS units on not only my computers but also on all my TV’s, security camera, Wi-Fi System, alarm and even for my RV power.

Long Term Storage at high SOC

There is substantial documentation that shows it is much healthier to store lithium cells at 30-50% SOC then at full charge (80-100%). At present, the Zero battery management system does not offer any type of cell conditioning for long term storage.Therefore its up to the owner to monitor the SOC and take precautions when storing the bike for long periods of time. 

Lithium Cells for Drone Use

Having used lithium cells since their inception in the RC Helicopter / Drone industry, we quickly found out that storing lithium cells at full charge would reduce the cells life and in some cases cause a chemical reaction to “Puff” the cells making them unusable. We remedied this problem when we discovered that cells stored at 40-50% had better health so modelers began discharging their packs to 40-50% after a flight project.

This is a typical drone lithium pack with the battery management module mounted atop the cell.



As our drones evolved, we designed a high tech battery management for drones to balance and control charging of the cells. This BMS system was eventually mounted on each lithium battery pack, so when charging there was no extra connections to be made other than the charger itself since each battery had its own BMS.

Self Discharging Circuitry for Lithium Storage

A few years ago, we incorporated a new feature into the BMS which protects the cells during storage. This involves a user programmable routine, where we program a period time in days for the BMS to begin a “Self-Discharge” routine which automatically discharges the cells slowly to 40-50% SOC.  Since most drone owners have many packs, this was a major advantage since they longer had to be concerned about managing each pack individually between uses.

While not mandatory, a system such as this could easily be adapted to the Zero’s BMS or even a separate aftermarket device could be offered. This discharge module would be powered by the bikes own pack and equipped with a resistive feature to discharge the pack to 50%. This would be helpful option for Zero owners since they would no longer have to be concerned during storage, the owner would just charge the battery to 100% and park the bike.

Since we don’t have this feature on the Zero, an easy work around would be to fully charge the bike, then ride it at moderate speeds to bring the SOC to around 50 percent. The bike could then just parked unplugged. At 50% SOC there is ample reserve to make up for the very minor loss which occur during storage with no concern of battery health. When Spring comes around, charge her up and your good to go.


IRIS Power Management System

I would like to share my Lowe’s Iris Wi-Fi alarm system and power management with you guys - Iris allows me to turn outlets on and off in my garage which power my electric vehicles chargers. I generally always keep my chargers plugged into the vehicles. When I need to charge or shut down a charger, instead of going out to the garage, I just open the Iris app on my phone to control the 110 volt outlets.

This is the 110 volt Wi-Fi controlled plug module - just plug your Zero in and your charging is controlled from an App on your phone.



Iris could be great for those owners who park their bike in a detached garage to control their charging.  My camper is located in another building and its nice not having to track up there in cold weather, snow or rain to power or unpower the RV. I also have an electric heater in the RV which I turn on when the temperature gets below freezing, all done with ease sitting on my couch. Of course you could be in another state and control or top off your charging if you wish.



Another nice feature of the Iris system it shows on the app how many watts its drawing at any given time. It also keeps track per session, once you enter your KW cost, it calculates exactly how much it cost to charge your car or bike on that session, weekly, monthly or yearly. What can I say, I love toys! 

Zero’s Battery Warranty

In closing, I’m sure most owners would question why Zero would recommend leaving the bike plugged in and at full charge knowing it was not in the best interest of the battery. The answer is simple; the lost health of the cells being stored at full charge will not be a factor in their warranty period. Also since Zero can not control the charge level when the owner stores his bike, which may be depleted, or say 10-20%, their biggest fear is the cells self-discharging themselves to a critical level during storage and cell deterioration, so their simple remedy is to keep it plugged in.

Keep in mind Lithium cells only self-discharge at a rate of 2% to 3% per month, so if we stored the bike at 50% SOC, in 6 months it would only lose an average of 15% and therefore the pack would remain at a safe 35% SOC.  Zero’s biggest fear is the cells self-discharging to a critical level and the need of replacement under warranty. With this in mind, they figure as long as the charger is plugged in and working everything will be in order. However, Zero's procedure fails to consider the owners safety risk and long term battery health as I outlined in this article.

Regards - Mike

[Richard230]

All I can add is that the 2012 Zero ZF12 S that I gave my daughter has been plugged in 24/7 ever since January 2012 and still seems to be working just fine.  If there has been any degradation of the battery pack, she hasn't noticed it (and neither have I when I ride the bike once and a while). The Zero keeps chugging along with only the occasional "glitch" when running wide open going uphill on the freeway. 

[JaimeC]

I'm sorry, but color me skeptical.  I've been around long enough to know that just because it's on the internet, doesn't make it true.  I have no idea who you are or what your credentials are for making the statements you made above, BUT Zero's engineers, who DEFINITELY have "skin in the game" say to leave it plugged in when it's not being ridden, they're the ones warrantying the battery and they're the ones who'd have to deal with any potential lawsuits from battery failures, explosions, fires, etc. so they're the ones I'm going to listen to on this particular topic.

I've also seen a representative from Farasis (the company that manufactures the batteries Zero uses) back Zero's claims right here in this forum.  That's good enough for me.

[Starpower]

I read the Farasis post to agree with the OP on long term storage. And working in the battery world for the last 30+ years I also agree with all said.

[frodus]

also, keep in mind, even though the Zero is plugged in, doesn't mean it's charging. The charger can be enabled and disabled both by algorithm upper set point, or by the Zero BMS.

Follow the manufacturer direction and let the BMS do its thing.

[benswing]

We have had discussions about this before including a battery engineer form Farasis.  My recollection is that he basically said if you don't want to hassle with it, leave it plugged in.  If you don't mind tending to the bike while storing it, then leave it at a lower charge, but you are responsible if you mess up the batteries.


Sent from my iPad using Tapatalk

[Kocho]

The problem with leaving it plugged in is not that it is or isn't charging. The issue is that the battery is kept at full SoC all the time (which is worse than if kept at lower SoC) and that much of the bike's electronics are connected to the grid (which exposes them to potential voltage spikes that could damage them, not to mention faster aging of certain parts that happens when they are "on" all the time). The OP explained what the potential and real perils of these two are. Often the manufacturer's recommendations are targeted to the least common denominator in terms of users and use case scenarios. Often they can't take the risk and let the owners manage things even if it means they could do better, because they could also screw-up. The instructions in the manual  are not always the best for the bike, especially beyond the warranty period. Remember that Zero is in for the money, and not necessarily for the best interest of the owners. How many of us will still have the same bike after 5 years, when the warranty is over? While their recommendations would certainly not result in premature failure within the warranty period, they are likely to increase the likelihood of failure or degradation of performance, especially past the warranty period. Up to each of us to decide what's best, of course, and weigh-in whether they want to put-up with the added effort and attention needed to manage the plugging and unplugging .

also, keep in mind, even though the Zero is plugged in, doesn't mean it's charging. The charger can be enabled and disabled both by algorithm upper set point, or by the Zero BMS.

Follow the manufacturer direction and let the BMS do its thing.

[MajorMajor]

The issue is that the battery is kept at full SoC all the time (which is worse than if kept at lower SoC)

It was stated on this forum that 100% SoC isn't actually 100% battery capacity. There is an upper limit at which the BMS will stop charging. This is intentional to prolong the battery's calendar life.

Lower SoC is indeed better but that incurs the risk of getting to too low a voltage which will irreversibly damage the battery.

[Lecram]

The issue is that the battery is kept at full SoC all the time (which is worse than if kept at lower SoC)

It was stated on this forum that 100% SoC isn't actually 100% battery capacity. There is an upper limit at which the BMS will stop charging. This is intentional to prolong the battery's calendar life.

Lower SoC is indeed better but that incurs the risk of getting to too low a voltage which will irreversibly damage the battery.

I have a bad experience that the battery completely depleted after a few months being unused, but plugged in.

[Kocho]

Yup. That's why I did not say "fully charged" as that would be more than full SoC And probably sufficiently low to not harm the bike too soon.

Given how slowly it self-discharges in my bike, I do not see a problem for it spending the winter unplugged. It's been sitting unused for over two months now and I don't see any self-discharge indicated on the dash or the app. I plan to ride it today for a few miles as the weather will be unseasonably warm and bring the SoC even further down to around 1/2 from the 87% indicated right now.

High self-discharge, especially with large cell imbalances when unused would indicate a defective or low-quality BMS, I would think. I don't think the BMS is active on our bikes when the bike is off and off the grid, so theoretically, it should not have the opportunity to mess-up the cell balance by just sitting inactive, but if a few of the modules have lower resistance it might lead to some cells being drained - and if it is just a cell or two, that won't show via the SoC and can go unnoticed, causing cell damage. That is why it is important to monitor the cell imbalance, which presumably is the difference between the most charged and the most discharged cell. So it is not enough to turn the bike on and look at the SoC, need to also check the cell balance with the app.

The issue is that the battery is kept at full SoC all the time (which is worse than if kept at lower SoC)

It was stated on this forum that 100% SoC isn't actually 100% battery capacity. There is an upper limit at which the BMS will stop charging. This is intentional to prolong the battery's calendar life.

Lower SoC is indeed better but that incurs the risk of getting to too low a voltage which will irreversibly damage the battery.

[Richard230]

I would like to point out that if you live somewhere like Scotts Valley, CA, and you ride your electric motorcycle every day, you want it to be fully charged before every ride to maximize your ability to go as far as you can.  Keeping the charger plugged in all of the time will make sure that you are ready to go each day and do not have to do any additional charging before taking off in the morning. 

[Kocho]

Yup, I'd probably be doing exactly that, for convenience, if I was riding it every day.

I would like to point out that if you live somewhere like Scotts Valley, CA, and you ride your electric motorcycle every day, you want it to be fully charged before every ride to maximize your ability to go as far as you can.  Keeping the charger plugged in all of the time will make sure that you are ready to go each day and do not have to do any additional charging before taking off in the morning. 

[Delnari]

I've been keeping my '17 SR at 100% charge when parked, but not always plugged in.  I check the level periodically to see if has dropped and plug in as needed.

[Low On Cash]

Thanks for all the reply's guys - Regretfully, as I mentioned, the only safety valve to prevent over-charging and a fire is the BMS - as we all know these like any electronic circuity are known to fail. A good rule of thumb (if possible) is to only charge when home - never trust your lithium batteries.

Here's an article where two such charging incidents occurred and they removed 50 bikes from service.



   

[SM]

I had heard there was a faulty plug and that this was NOT battery related.