Is BIG BATTERY full of Crap??

[ghostwriter66]

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

 

[Will Prowse]

I just need the data sheet for the cell they are using. It probably is. I had my viewers make me feel stupid today because they mentioned that A123 and Winston are capable of charging at lower temperatures. So I guess me and your R&D guys are way behind. Winston cell have been around for ages.

I am going to email head engineer to send me data sheet for the cells they are using tonight.

 

[Will Prowse]

Yep, my viewers were correct about winston. Darn. Please excuse my ignorance. Let me look for the A123 sheet now. Here is winston: https://www.thunderstruck-ev.com/Manuals/Thundersky Product Manual.pdf

 

[Will Prowse]

Yep, correct again. Sounds like quite a few LFP can charge below 0 degrees Celsius. I am guessing they modified the anode to prevent lithium plating.

 

[ghostwriter66]

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View attachment 26609

Yep, my viewers were correct about winston. Darn. Please excuse my ignorance. Let me look for the A123 sheet now. Here is winston: https://www.thunderstruck-ev.com/Manuals/Thundersky Product Manual.pdf

OK ... so technically the BigBattery ppl were right when they said you can charge down to -20 ... the issue is that its such a low charge its barely negligible. Its dishonest on their part not to let most of the "unfamiliar" (solar newbies) know on their webpage that anything under 0/32 that the charging drops to 0.1CA ... but I guess their marketing department is looking for a niche. WHERE this will backfire on them is that ppl living in RV's and Vans are going to use these batteries below 0/32 and drop them down to 5% or so during the day/night - and then the next day get plenty of sun all day but their batteries will only go up from 5% to 6% and they will think something is wrong ... Nothing is wrong - its just that ALL the batteries are going to do is trickle charge until the temp gets above 0/32 - but I would hate to be that Van person relying on solar to keep me warm at night and having bought this BB battery because they said It could charge down to -20C ...

 

[Hedges]

0.1C charge rate doesn't sound all that bad. Hey, I use AGM!
Will they self-heat at that rate? Enough to let them get a full charge by evening? Of course, BMS or something would have to communicate to charge controller what current is wanted. Or, have a shunt regulator fed to a heating pad.

 

[GMB]

OK ... so technically the BigBattery ppl were right when they said you can charge down to -20 ... the issue is that its such a low charge its barely negligible. Its dishonest on their part not to let most of the "unfamiliar" (solar newbies) know on their webpage that anything under 0/32 that the charging drops to 0.1CA ... but I guess their marketing department is looking for a niche. WHERE this will backfire on them is that ppl living in RV's and Vans are going to use these batteries below 0/32 and drop them down to 5% or so during the day/night - and then the next day get plenty of sun all day but their batteries will only go up from 5% to 6% and they will think something is wrong ... Nothing is wrong - its just that ALL the batteries are going to do is trickle charge until the temp gets above 0/32 - but I would hate to be that Van person relying on solar to keep me warm at night and having bought this BB battery because they said It could charge down to -20C ...

 

[Crazyfrog]

Well, now that I just joined the forum. I am better informed. But I did last night go and preorder 4 of the new 24v power blocks from bigbattery with these supposedly -20c charging ability. Oh well. With the $100 off preorder price and the diysolar discount (take another $150 off) 16kwh total package cost me only 5399.00. With free shipping. Not bad though at 0.34 per watthour. A big step up for me from my 4 old 200ah 6v borrowed from my rv. I am only getting 100ah at 12v (1.2kwh) from them currently.

The charge below freezing was a determining buying factor, but so was the servicability of the cells and bms. And the price per wH rocks for no assembly required!

 

[toms]

As i have mentioned in other threads, there are many different ways to construct a LiFePO4 cell.

I know of a set of LiFeTech LiFePO4 cells (the same as i use) that have been regularly charged over the last nine years at subzero temps.

0.1C is not insignificant- for a 48V house bank of 400ah that is a 40amp charge (over 2kw)

Perfect for those panels facing the early morning sun, and by the time the sun has risen to the point the PV output is higher, the cells have warmed.

 

[AussieSim]

I just need the data sheet for the cell they are using. It probably is. I had my viewers make me feel stupid today because they mentioned that A123 and Winston are capable of charging at lower temperatures. So I guess me and your R&D guys are way behind. Winston cell have been around for ages.

I am going to email head engineer to send me data sheet for the cells they are using tonight.

I would be interested in the datasheet, because the I haven't seen a 170Ah Lishen LiFePO4 prismatic cell listed on Alibaba.

 

[Dzl]

Yep, my viewers were correct about winston. Darn. Please excuse my ignorance. Let me look for the A123 sheet now. Here is winston: https://www.thunderstruck-ev.com/Manuals/Thundersky Product Manual.pdf

Apologies if this has been mentioned already I haven't read the full thread but Winston cells are not straight LFP, they are LYP. Which quite probably explains the apparent cold weather advantage.

Its also worth nothing this bit from the MarineHowTo LiFePO4 article:

There is some confusion out there surrounding the LiFeYPo4 Winston or Voltronics cells. Winston claims that the addition of Yttrium allows the cells to be “charged” at temps as low as -40ºF. I have asked Winston & their old US distributor Balqon, via email on multiple occasions, to furnish or name any third party testing that confirms it is safe to charge LiFeYPo4 cells at temps below 32ºF/0ºC. All I’ve received is dead silence. With Winston Chung’s past history all I can say is I use caution with some of his claims. Please do your own homework on this if you plan to charge in a sub 32ºF/0ºC environment. Voltronics, who uses Winston to manufacture their LiFeYPo4 cells, suggests not charging these cells below 32ºF/0ºC.

Until I see some verified & legitimate third party or University level sub 32ºF/0ºC testing I am holding steady that you should avoid this temp range for charging. If anyone has a white paper I missed on cold weather charging of LiFeYPO4 please forward it along.

I have searched for info on this chemistry but really haven't been able to find anything of depth on it, even from the manufacturer. I'm curious to learn more about it if anyone has any info. I'm going to take a peak at the old Thundersky doc will posted when I get a chance later, it way more detailed than the current documentation I've found from Winston (less than 1 page in length).

Can someone explain what 0.1CA refers to (is this c rate? amps? 'cranking amps'?)

 

[toms]

C rate is the rate of charge or discharge of a battery. A 100ah battery being charged at a 1C rate is being charged at 100A. Some battery manufacturers refer to this as 1CA. ie 1C(amps)

0.1CA in this example is a charge rate of 10amps.

You won’t find definitive documentation on the anode/cathode/separator/electrolytes used in proprietary LiFePO4 cells. There are many scientific papers showing extreme cold weather LiFePO4 cells and their performance.

Once again, since accelerated C rate charging/discharging is the number one lifespan determinant of LiFePO4 - you just have to wait a couple of decades to see how your chosen cell fares.

 

[striider]

I have a cabin at 9400 feet that is unheated when I am not there. Temperature is a huge factor for me, as it has been -20C inside before, but usually stays above -18 or so. Side question: will bouts of -28C damage LiFePO4 batteries? I understand they won't take a charge until they warm up.

 

[Sabre36]

Kind of odd to suggest -20°C charging when the BMS is supposed to, based on the specification sheet, cut off the charge at -4°F? Also, be aware that "operating temperature" is not the same as "charging temperature" on many specification sheets..

 

[Steve_S]

http://en.lishen.com.cn/index.aspx

Sadly I cannot find the spec sheets for their cells.

 

[striider]

 

[Luthj]

At cold temperatures the lithium ions aren't very mobile, and have a hard time entering the holes in the anode (capturing). This max capture rate drops with temperature, but its accelerates as the temp drops below ~35F. The exact curve will vary with anode porosity/design, electrolyte composition/etc, and most importantly SOC. As SOC increases, especially near 90%, the max capture rate will drop.

Now there is typically a temperature where any charging will cause plating, but its not well defined for most cells, and typically is a fair bit lower than the 0C rule of thumb.

When the charge rate exceeds the max capture rate, the lithium ions start to plate the anode surface. This effectively plugs some of the holes in the anode, causing capacity loss.

Most LFP cells can tolerate very low charge rates 0.05C for example) at low temps without issue, (except at very high soc?). This is part of the reason that many systems with small solar arrays tied to large LFP packs get away without a low temp disconnect, even at low temps.

The issue is that most manufactures have not fully tested the low temp charging effects to determine the safe, and recommended parameters.

Edit: for example Trojans Trillium battery (made by K2?) shows they do allow some current at low temps.

 

[Will Prowse]

I just need to buy a freezer and cycle them a few times. Then we will know.

My understanding is that lithium plating would show up in a capacity test result after a single cycle.

I will buy the coldest freezer I can find.

 

[Deleted-User]

I just need to buy a freezer and cycle them a few times. Then we will know.

My understanding is that lithium plating would show up in a capacity test result after a single cycle.

I will buy the coldest freezer I can find.

Costco is running a deal on Midea 7 cu.ft. for like $159...hope they have stock in LAS.

 

[Hedges]

I just need to buy a freezer and cycle them a few times. Then we will know.

My understanding is that lithium plating would show up in a capacity test result after a single cycle.

I will buy the coldest freezer I can find.

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