Is BIG BATTERY full of Crap??

Hedges

I See Electromagnetic Fields!
I am going to freeze those cells to -20C, and charge at max rate. Repeat. Then capacity test, or test internal resistance with my cell monitor.

And I do not trust any company or distributor. @fat_old_sun is correct, and the only way to find out is to test it ourselves. Bigbattery has a qualified EE as head designer, and he knows his stuff. I am not sure where they found him, but he seems to know everything. I have thrown a lot of questions at him, and he always knows his stuff.

But yeah, lets test it!
Good start, but the corners are what were most likely to be tested (if it was tested for all those functions.)
Sometimes the failure occurs under other conditions.

If they do successfully disconnect at 100A, -20C or whatever, repeat until you find the current threshold. And the temperature threshold.
Then test how the battery tolerates being operated just inside the disconnect limits of current, of temperature.

It's your job to be the better fool!

Do you automate test equipment operation? (Labview, VEE, Python, Matlab, Basic, whatever)
 

Will Prowse

Admin
Staff member
Moderator
Good start, but the corners are what were most likely to be tested (if it was tested for all those functions.)
Sometimes the failure occurs under other conditions.

If they do successfully disconnect at 100A, -20C or whatever, repeat until you find the current threshold. And the temperature threshold.
Then test how the battery tolerates being operated just inside the disconnect limits of current, of temperature.

It's your job to be the better fool!

Do you automate test equipment operation? (Labview, VEE, Python, Matlab, Basic, whatever)
I really need to automate. Have a dc to dc battery cycling system. Wouldn't be that hard to build, but manual testing sure is easy. But yeah, I will try to find the current threshold. Would be more professional to graph out the data too.
 

Dzl

Perpetual Newbie & Unofficial Forum Librarian
Staff member
Moderator
A reminder / refresher for new and old members, this is not the first time we have discussed sub-freezing charging. Or the first time we have discussed the relationship between C-rate and Temperature (spoiler: there is no one specific point that defines safe/healthy charging, its a gradient and a relationship between C-rate and temperature). This conversation came up last year, and then again earlier this year after Will's interview with Battleborn (who uses a low temp cutoff of like 25*F I think). For visual folks like myself, this graph from Ian George shows the rough relationship between charge rate and temperature:

2vgsMuP.png
 
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Dzl

Perpetual Newbie & Unofficial Forum Librarian
Staff member
Moderator
One thing the above trend makes me think about is how useful it might be to have a charger (or maybe BMS) that 'throttled' current based on temperature as opposed to a simple 'on/off.' Victron controllers have low temp protection (with an addon) and are temperature aware, they also have the ability to manually limit current. It seems like this is all the building blocks for what I'm envisioning, the software would just need to be designed for this.
 

Steve_S

Offgrid Cabineer, N.E. Ontario, Canada
Well, it should be simple enough for BIg Battery to post the actual Lishen Datasheets for the cells used in this pack, or any other cells / packs they have for sale..

PS: Geez, a case a Deja-Vu on the Cold Temp thing again...
 
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ghostwriter66

"Here - Hold my Beer"
I read it as saying it could recharge 10% in the next hour. That should easily put in at least 50% during the day even if it didn't warm up.

As you said, the consumers aren't likely to understand.

The system needs to automatically address that. Does Big Battery's product at least automatically disconnect if charge current exceeds allowed maximum at that moment/temperature?

Ideally, the charge controller is somehow informed and adjusts its output. Either a datacom link (complex), or Big Battery ought to have a linear regulator that reduces voltage applied to the cells in order to reduce charge current to 0.1C. Whatever voltage drop and watts dissipate in the regulator ought to heat the batteries. Or, charge controller with temperature sensor, programmable for current limit vs. temperature.

So doing real math that we use here at work - thats not done by marketing students trying to make a sale - NO - the actual real numbers is that at -20C ... and with a charge rate of 0.1Ca (which is slightly high) - its going to be - (well let me switch to layman's terms) - WHAT TAKES YOU 8 HOURS TO TAKE OUT OF THE BATTERY WILL TAKE YOU 12 DAYS TO PUT BACK IN if it remains below 0/32 .. . So NO not 10% per hour ... we are talking in reality that if your 280aH 3.2V LiFePO4 battery is at 5% and the temp is -20 and you have a proper BMS hooked to it (regardless of panel size) that maybe you are up to 9% after 5 hours in the sun ... thats 9% from 5% ...
 

HaldorEE

Photon Sorcerer
So i am looking for actual documentation. @Will Prowse video yesterday he was saying that BigBattery told him (and its ON their website) that their LISCHEN LiFePO4 batteries can be charged at: -20°C – 55°C. One of my guys called today and BB was of no help -- lot of well my sister's boyfriend neighbor knew a guy that said this or that but no spec sheet. LiFePO4 is a CHEMISTRY. Chemistry does NOT change because you simply put it in a different case. SOOO either 2 things are wrong - either my corporate R&D guys are waaaay behind pushing this info out to the field -- or BigBattery is pulling the wool over @Will Prowse and causing him to misinform millions of folks ... personally i would just like to see the test sheet they used ... NOW don't get me wrong -- YES we charge our LiFePO4 batteries when its well below 0C BUT its such a minor trickle charge - like 0.01C (don't quote me) ... BUT thats NOT what BB is saying ... they are saying that you can charge them normally at -20C ...

If anyone has any real info please let me know ...

https://bigbattery.com/product/12v-lifepo4-power-block/?ref=8 clearly states its LiFePO4 and clearly says charges down to -20C
The spec sheet for the battery claims the low temperature cutoff is -4 F. Which Will proved didn't work.

BB12V170AH.jpg
 

ghostwriter66

"Here - Hold my Beer"
Opps, missed the -4F = -20C. My bad

No worries on that at all -- I guess i shouldn't be being so pissy on this - but a year ago we had the same subject come up with BattleBorn - which was trying to convince buyers that they also had a magic-bean "special" LiFePO4 chemistry but somehow couldn't articulate how THAT worked -- anyway - MY personal concern is that ppl see this and buy it and are disappointed because they didn't understand the print about 0.1Ca charge rate below 0/32 ... heck most folks wouldn't even know what that means - and won't know until they start complaining that their batteries aren't charging and BigBattery says "oh well - we told you 0.1Ca - not our fault you didn't know what that meant" .. so like @Steve_S said "its dejuvu all over again" ...
 

EasyStreet

I used to be a somebody ...
Those have got to be crazy expensive o_O -20C will do haha

edit: just ordered Midea, which hits -28C. So we can easily trigger the charging protection sensor on the -20C packs.

The cheap test equipment you've been using is ok but you have the lab now... you need to invest in real test equipment.
 

Dzl

Perpetual Newbie & Unofficial Forum Librarian
Staff member
Moderator
So doing real math that we use here at work - thats not done by marketing students trying to make a sale - NO - the actual real numbers is that at -20C ... and with a charge rate of 0.1Ca (which is slightly high) - its going to be - (well let me switch to layman's terms) - WHAT TAKES YOU 8 HOURS TO TAKE OUT OF THE BATTERY WILL TAKE YOU 12 DAYS TO PUT BACK IN if it remains below 0/32 .. . So NO not 10% per hour ... we are talking in reality that if your 280aH 3.2V LiFePO4 battery is at 5% and the temp is -20 and you have a proper BMS hooked to it (regardless of panel size) that maybe you are up to 9% after 5 hours in the sun ... thats 9% from 5% ...
You and @Hedges are not on the same page as to what 0.1CA means. I had never heard of it so I am not going to weigh in, but until you agree on the meaning of the unit, you guys are going to be talking past each other.

Based on context I'm pretty sure Hedges is interpreting 0.1CA as 0.1C (28A for a 280Ah cell). Whereas you seem to be defining it differently (I'm not 100% sure how you are defining the unit, would you clarify)?
 

snoobler

Solar Honey Badger
You and @Hedges are not on the same page as to what 0.1CA means. I had never heard of it so I am not going to weigh in, but until you agree on the meaning of the unit, you guys are going to be talking past each other.

Based on context I'm pretty sure Hedges is interpreting 0.1CA as 0.1C (28A for a 280Ah cell). Whereas you seem to be defining it differently (I'm not 100% sure how you are defining the unit, would you clarify)?

@ghostwriter66 this plz.

WTF is 0.1Ca?
 

Dzl

Perpetual Newbie & Unofficial Forum Librarian
Staff member
Moderator
The more I look at that Doc (the Thunder Sky one), the less confident I am in it.
  • First off, its a Thunder Sky document, not 'Winston' or 'Winston-Thundersky', my understanding is that Thunder Sky ceased operation 15 years ago, so this is a very old document
  • If you look at the screenshot linked below for low temperature charging, the graph states at -35*C / -30*F a LFP cell can be charged at a C-Rate of between 0.1C and 1C (or at least that is how I interpret it). I can't believe that this could be acceptable, this doesn't even appear to be for the LYP chemistry.
  • The minimum discharge cutoff is listed as 1.5V this seems extremely low, I know that voltage can be lower at extremely low temperatures, and I have no evidence that 1.5v is too low, but still, I struggle to believe this would be an allowable voltage with today's knowledge. Maybe I am off base here.
 

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toms

Solar Addict
If that's true, then why does it take 12 days to charge a 280Ah battery at 28A?

I would love to see the result of 28A for 12 days into a 280ah battery.

I regularly put 50a for 4 hours to get 50% charge into my 400ah pack. I don’t know how it could work any other way?
 

Steve_S

Offgrid Cabineer, N.E. Ontario, Canada
I'm surprised no one else posted this link, so here it is...
I might suggest to those who are curious & wish to learn more about battery tech "as it is today" with more current information to go through the site below, there is a vast goldmine of Real, Factual Information.

 
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