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[wontuan]

Not to pry, but how do you know Farasis' practices and accident statistics?

I guess I should have mentioned that I work for Farasis designing BMS and a bunch of the Zero engineers are my good friends.

[Low On Cash]

User Low On Cash is mostly right. Cells don't like being stored at full SOC, it shortens the cycle life. But there is a reason why Zero recommends leaving the charger plugged in.

I am not sure where this idea that there is a 2-3% self discharge every month came from but it isn't true with Farasis's cells. The self discharge rate is heavily dependent on chemistry, temperature, and SOC. After extensive testing with these cells, at higher SOC (70-90) Farasis's cells will self discharge maybe around 1-1.5% a month while at lower SOC its much less. So much less that the amount of current the BMS draws is more important than the self discharge rate.

Other people have already said it but Zero only charges the battery to 4.15V which is not full capacity of the battery. The area that hurts cycle life the most is between 4.15V and 4.2V, any thing higher than 4.2V it is considered dangerous (I can explain why if people are curious).

I store my bike around 40-60%, this is what Farasis stores their batteries at. While leaving the bike on charge isn't the best for it's cycle life it shouldn't cause any fire. In the event the BMS locks up it can't do anything but open or close the contactors. There is also the MBB on the bike that can protect the bike in the event of a non-responding BMS. If the charger dies due to surge or something then the BMS will open the contactors due to a non responding charger.

The ways to get a battery fire is to put it in a super hot environment, or over discharge the battery then try to charge it back up, or over charge the battery. Leaving the bike on charge can't cause either of those scenarios. Leaving the bike plugged in won't allow for an over discharge, and since the charger won't go higher than 116V you can't over charge your battery plus the BMS and MBB are there to oversee things. In the event of the BMS and the MBB not responding and the contactor is welded and the charger some how outputs more than 117.6V then yes there is a risk of fire. This is probably why Zero ask you to check on it every 72 hours to make sure the bike is still responding and the BMS is still alive. Also just to clear things up there has never been a fire with a production Zero bike that uses Farasis cells (this doesn't count prototypes and test bikes).

I think someone said that Zero’s BMS is like $20-30. Not true, the parts on there alone are like $40 not counting the PCB, potting, and assembly cost. Their BMS is not perfect and has some known flaws but they are making them better each year. But when it comes to protecting the battery the BMS does a really good job and won’t close the contactor if there is anything out of the ordinary. I think the Zero BMS uses some of the same parts in the Tesla Model S BMS.

So the reason Zero says to leave the bike plugged in is that it prevents over discharge and there shouldn't be any over charging because they left some margin and there are many things that needs to fail to over charge. This does hurt cycle life on the cells, but its better then having either an over discharge or over charge situation.

Also something else that people might not know. Without saying too much there are a few magic secret things in those battery pack and cell pouches that in the event of thermal runaway or fire they will limit the current flow and suppress any damages. There is a reason why Zero pay a premium for these pouch cells and not cylinder cells like other people

Sometimes it may not be clear why engineers including those at Zero and Farasis do what they do but I assure you that they are concern with safety and they always have to evaluate the risks. I am sure someone will say that I am wrong but I think I will leave at that.

Wontuan thanks for your detailed reply - it is greatly appreciated and it confirms a lot of speculation.

Regards - Mike

[clay.leihy]

Of course if your bike never sits still for more than a couple of days, storage isn't much of an issue. 😉

Sent from my Z981 using Tapatalk

[gyrocyclist]

  In my years in the model industry, I have seen first hand many of my co-workers homes and business burnt to ground as a result of lithium cells. 

Wow, that's a bit inflammatory

But seriously, dude, I'm thinking you should sell your zero. Sounds like a disaster waiting to happen!

[JaimeC]

Of course if your bike never sits still for more than a couple of days, storage isn't much of an issue. 😉

What HE said!! 

[Low On Cash]

Hello Zero Owners - Sorry I didn’t get this up sooner - since this very thread brought up safety concerns of Zero’s recommended “UnAttended Charging”, Zero has changed their policy and now does not recommend leaving the bike on charge for long periods of time since there is possibility of an over-charging the pack which would result in the pack igniting in fire.

I would like to personally thank the folks at Zero for taking the immediate incentive to correct their “Long Term Battery Storage” recommendations for the Zero motorcycle. 

I’m certain my safety concerns posted on this thread, combined with my personal letter to Zero with my concerns regarding the “Fire” risk of unattended charging was instrumental to their decision.

As I indicated in my remarks on this thread and my letter to Zero’s Corporate office, due to very low self-discharge rates of current lithium cells, there is no benefit in having the bike powered and unattended for long periods of time. As I outlined in this thread a safer method of simply discharging the cells to 60-70% SOC provides better health for the pack and most important allows the bike to be un-plugged for long term storage therefore removing the possibility of charging circuitry failure, which may result in an over-charged SOC, resulting in a fire threat, loss of property or even death as we have witnessed numerous times with other lithium powered vehicles and devices.

Best Regards - Mike Mas

[BrianTRice@gmail.com]

I've reported your latest comment for deliberately mischaracterizing Zero's statement again. Let's lock this thread, please.

[Fred]

And please somebody buy his DSR, then he'll have no reason to hang around.

[Shadow]

[skadamo]

If everyone has said their piece I can lock this thread. The great thing about discussion forums is people can say what they think and others can support or deny it. What is posted may or may not be true. Leaving a thread unlocked allows folks with the truth to share it if it's the latter.

Most folks on this board are intelligent enough to think twice and verify what they read so I'm less inclined to lock a thread.

Locking threads may just send people to other forums to post the same thing there. Why not just beat it to death in one place and call it done?

Pm me if you have thoughts one way or another. I'm interested.