Repair or replace GZ Yeti 1400 Lithium battery

[fanplant]

Hi guys, first post. My Yeti 1400Lithium WiFi shows 5.5v. I've had it in storage mostly at 100% for 2 years and went to use it and the percentage readout went out of calibration. GZ tech support said to bring it down 5 times to let it learn again. It worked. Then I used it for a week as a power source for my 3d printer charging it with the fast charger and 2 of the 60w chargers. The 3d printer draws 400w when heating ant then 50w running. After that I found it would go dead if left alone in 3 days. GZ will swap the battery for $600 including shipping at least back to me (I didn't question them real well). I'm gun shy, I bought the lithium over Pb for life expectancy but 2 years?? I'm posting pics here because I can't find anyone else who took theirs apart.

 

[svetz]

What did you decide to do?

 

[Ely]

It's not good to hold a Li-battery always at 100%. If the charge more than 80% or lower as 20%, inside the cells grows Dendrites. They are crystal-like structures they looks like a farn. The Dendrites stresses the cathode and the separator of the cell and there are no or very little Dendrites between 20 and 80% charge.

The best for a Li-battery is simple: use it. It mens, all 3 month discharge down to 50%, not lower than 20%. Recharge. The Dendrites grows above 80% charge again, but the structures are little different and not at the same place. This spread the stress all over the cell and isn't always on one spot. You get a long last of the whole battery.

If you have a old lead-acid Yeti, it's very imported, you charge it at every opportunity and hold the charge at 100%. All of my old lead-acid Yeti's (some 150 and two 400) are running since 3 or 4 years every day, the batteries are all the first and very healthy.

Every battery chemistry needs they own handling to get a long life span. If you know this, a lead acid can get a last of 5 up to 8 years (it's easy to swap the battery of the old Yeti, it's a standard SLA), Li-NMC can get more then 10 years.

In Germany we have some companies they configure you individual Li battery pack and you can swap the battery pack by doing yourself. I think the same is in the US, search about such companies.

 

[fanplant]

Yeah I didn't give it the love I should of. I believe GZ says to leave it plugged in and discharge to 30% once in a while (I'd have to go read up on it). It would be nice to have a 80% storage mode but I digress.
My thoughts so far:
1. Not safe, I try to identify the offending cells probably by bypassing the bms and bringing it back up to voltage looking for warm cells and low voltages. This is the craziest of all plans.
2.Buy a bunch of high quality cells and a tab welder and replace them all. Probably from Jehu that youtuber that electrified his VW bus:

Kit

kit.co

3. Bite the bullet and give GZ another bunch of cash +$600.
4. if anyone knows a battery rebuilder in NY/NJ
5. Any Ideas you guys have. I can't swap to lead afaik and I don't want to. I don't know what is communicated on the tiny 3 pin wire that "talks" to the display. Really my pics above are pretty rare in the internet and idk if I can swap and program of what is happening there at all.

Thanks Guys!

 

[svetz]

...It's not good to hold a Li-battery always at 100%. If the charge more than 80% or lower as 20%, inside the cells grows Dendrites....

Do you have a reference for that? I'd always heard dendrite formation was related to C-rate. I've heard keeping them less than 95% full makes them happier, but don't know why. Would like to read up on it.

 

[Ely]

A lot to read ...

The question is how long the Dendrites (the needles) are. If the SOC about two years at 100%, the Dendrites perforated the separator and the cell is weak or defect (a horrible high internal resistance). On top the Dendrites needs volume and this is a mechanical stress too.

Everybody here knows, LiPo (pouch cells) blows up gladly, despite good handling. This is the result of Dendrites.

 

[svetz]

Thanks! I'll look around for an English translation. I did find this too:

For a lithium battery the structure of the positive terminal becomes unstable when depleted of electrons for long periods of time. The instability of the positive terminal can lead to permanent capacity loss. For this reason, a lithium battery should be stored near 50% SOC.

Wonder how long that takes to become unstable? I store my peak jumpstart at 100% and only pull it out for emergencies...but it's nice to have 100% power and not charge it before I use it. Ditto the powerwall on the house.

Update: Battleborn recommends Bulk/absorb = 14.2 – 14.6 V, Float = 13.6 V or lower. That sort of follows the V drop-off:

 

[Archetype-IS]

Thanks! I'll look around for an English translation. I did find this too:


Wonder how long that takes to become unstable? I store my peak at 100% and only pull it out for emergencies...but it's nice to have 100% power and not charge it before I use it. Ditto the powerwall on the house.

The link is in English. Just have to scroll pass the intros.

 

[svetz]

From an October 2019 article:

The team found that the level of ethylene carbonate directly correlates with dendrite and whisker growth. The more of the material the team put in the electrolyte, the more the whiskers grew ... Some changes, such as the addition of cyclohexanone, prevented the growth of dendrites and whiskers.

The scientists also say more study is needed

 

[Ely]

A powerwall shows at real 80% SOC 100% charge, like electric cars. This is to prolong the last and avoid dendrites. If the powerwall shows you 0% there are real 20% charge.

The Battle Born batteries are LiFePo4. The Yeti have Li-NMC batteries inside. A different chemistry, a different handling.

My electric bicycle is 10 years old. The battery (Li-NMC) is original, so 10 years too and so good as new. I never discharge below 20% and I stop charging around 80% (mostly, sometimes I forgot to unplug).

 

[fanplant]

Well I opened it last night. The middle bank of cells is at 0.5v. I think the whole pack is 180 cells. I'm not going to replace them myself. So I'll probably do the 600 bucks plan. To bad the battery doesn't fit some standard form. Here's a pic and I'll post more later.

 

[fanplant]

Here's some more photos of the battery in my yeti 1400 lithium wifi. It was nice that the aluminium cover is held down by 6 screws and then another 12 screws, 6 under the foam strips, hold down a plastic plate over the BMS. Not all the holes get screws in the plastic plate, I guess they use it for a few models. The final pic is it back together and showing the increase in voltage because I was able to directly charge two of the banks of cells a little bit but nothing went into the middle one that actually seemed to drop from around 0.5 to 0.3v.
If anything strange happens with customer service I'll post here. So far tech support has been real nice about sharing info and spending time with me even though it's way out of warranty (I'm not telling them about this though I did mention I might try lol). May these pics help someone trying something with their GZ.

 

[fanplant]

Well I called last week and Edgar said it is 599 with shipping both ways but had to contact his repair dept to find out if they had stock before he started the process $$. He never called back. I'll try again. He mentioned the new models are out so I wonder if my species is out of luck. IDK if a diy or battery repair place could do it for 600 bucks. the price of 150 cells (or more) alone could be crazy.
Does anyone have any ideas of an off the shelf battery that will play nice with the GZ charging? It doesn't have to fit as I'd put a big anderson connector on my GZ paperweight. Between the pic of the label below and the internet the specs are:

Lithium Ion NMC
1425Wh (10.8V, 132Ah)

The charger seems to cutoff at 12.6v. A tech told me that 12.4 was max and 9.8v was the low limit with 9.5 being critical.

Googling the "3icr19/66-50" is fun because it returns a bunch of 9 cell laptop batteries.

 

[fanplant]

Well well, I just got through to GZ tech support and they told me battery failure is covered under a two year warranty?? I'll believe it when I see it and keep you all posted. I'm worried I got through to a newbie over there but we'll see!

 

[fanplant]

Well well, I just got through to GZ tech support and they told me battery failure is covered under a two year warranty?? I'll believe it when I see it and keep you all posted. I'm worried I got through to a newbie over there but we'll see!

10 mins later and I calculated how long I've had it. 2 years 4 months 16 days, so idk why the guy was saying it's covered, we'll see.

 

[fanplant]

So the tech support guy is no longer working for them and they found my message in their system and contacted me a month later. I told them either way 0$ or $600 I want to do the repair. Will keep you guys posted

 

[fanplant]

Well they are honoring the guys offer for 0$ so bravo for GZ support! I figure since I did contact them way back when I thought my prob was just calibration of the SOC indicator and I assumed it wasn't covered I'll take it! Well they had to send me a special fedex ground box to put my box in and set up a ground pickup. They'll be shipping me an open box yeti to replace mine. When I get it I'll be picking your brains on the best way to store it. Gone are the days of leaving it plugged in.

 

[fanplant]

Well my "open box" replacement arrived yesterday! Kudos to Goal Zero!

Now what's everyone's thoughts on what voltage to store it at and how often to cycle it? It's for emergency use and I don't lose power often. I would like to keep it with a full "tank" but understand that isn't best for its health. My plan is to mark it on my calendar so I don't forget.

 

[Ely]

Store it at 50% charge, use it at minimum every three month (discharge until 20%, charge until
80% or up too full and discharge until 50%).

So you keep the battery in a good condition for about ten years

 

[fanplant]

Store it at 50% charge, use it at minimum every three month (discharge until 20%, charge until
80% or up too full and discharge until 50%).

So you keep the battery in a good condition for about ten years

Thanks, that's a nice plan. I put it on my google calendar with a reminder so I don't forget.