Jay, LFP battery manufacturing in China is a real mixed bag. There are a large number of rejected battery cells that are used in the cheap batteries like seen on Amazon. I have over 2300 emails from such companies that want me to sell their batteries.
Personally I would not trust any battery without a verified UL 1973 certification. Larry Crutcher On May 11, 2026, at 8:30 AM, Zeke Yewdall via RE-wrenches <[email protected]> wrote: Interesting. It is actually a different battery construction than normal LFP it appears. I had not seen that before. My understanding was that the graphite anode was a big portion of the low temperature problem, but they do mention optimized anode and cathode, in addition to a different electrolyte. I do note that it has to be used in closed loop operation in order to properly limit the current at the low temperatures. Zeke On Mon, May 11, 2026 at 5:53 AM Jay <[email protected] <mailto:[email protected]>> wrote: > Hi Zeke > > Here is the link to the battery. I should have included that no heater in > this one. > > In the manual it shows reduced charging/discharge rates at colder temps but > they still seem lower than I’ve ever heard of. > > <eco-worthy-cubix-100-pro-48v-100ah-server-rack-battery-bluetooth-wifi-low-temp-charge-10-years-warranty-lithium-battery-eco-worthy-3996703.jpg> > Cubix 100 Pro 48V 100AH Lithium Battery | Low-Temp Charge | Eco-Worthy > eco-worthy.com > > <https://www.eco-worthy.com/products/eco-worthy-cubix-100-pro-48v-100ah-server-rack-battery-bluetooth-wifi-low-temp-ready>Cubix > 100 Pro 48V 100AH Lithium Battery | Low-Temp Charge | Eco-Worthy > <https://www.eco-worthy.com/products/eco-worthy-cubix-100-pro-48v-100ah-server-rack-battery-bluetooth-wifi-low-temp-ready> > eco-worthy.com > <https://www.eco-worthy.com/products/eco-worthy-cubix-100-pro-48v-100ah-server-rack-battery-bluetooth-wifi-low-temp-ready> > >> On May 10, 2026, at 3:24 PM, Zeke Yewdall via RE-wrenches >> <[email protected] >> <mailto:[email protected]>> wrote: >> >> >> I don't know this particular one, but what I've seen for a lot of LFP with >> the built in heating pads is that they can charge down to -4ºF. But, what >> this means, is that with the heater running, it can keep the battery warm >> enough to charge (above 32ºF) when the ambient temperature is -4ºF. This is >> not, in my mind, really a cold weather battery, but rather one that in the >> right conditions could be used where it might occasionally get cold. Like >> in an unheated garage that might bet below freezing occasionally, or if >> someone leaves the door open by mistake. Or for ourdoor use in moderate >> climate that might get into the 20's or teens a few times a year. But not >> for outdoor use on a mountaintop radio repeater or remote cabin in Montana >> where it's in the single digits for weeks. >> >> Insulating the battery will obviously help a lot in trapping what heat that >> the built in heaters give off -- I've seen the heated ones work okay when in >> a highly insulated box (just like we used to build for lead acid all the >> time) and isolated from the concrete floor. But it also depends on the >> particular control logic, and whether you have grid power. If you have grid >> power to keep them warm they can work pretty well. For off grid, the heat >> is needed the most right when you have the lowest insolation, which isn't a >> good situation. And for control logic, I've seen two variations -- one is >> to run the heater from the battery, which insures that it stays warm... but >> risks tanking the battery fairly quickly (in a few days) from the heater >> load alone. The other variation is to only run the heater when there is a >> charging source for the battery -- which doesn't risk draining the battery, >> but also means that overnight in an off grid system there is no heat input, >> making good insulation around the battery even more important -- to keep the >> temperature above 32ºF by morning so it can accept a charge then -- >> otherwise you are limited to the charging source only running the heater for >> a while (several hours?) till the battery gets back up above 32ºF and can >> accept a charge, and by then you may have wasted a lot of your short winter >> sun hours. >> >> Another thing to consider is what is the lifespan of the heating pad? If >> it's 3000 hours, then that will last a long time -- similar to the battery >> lifespan of 15 to 20 years -- when used a few hours a day during a few >> weeks a year. But if used in a climate where it needs to operate 24 hours a >> day for 3 or 4 months out of the year, the heating pad will wear out long >> before the lifespan of the battery. And then it's no longer a heated >> battery, and it's usually not possible to replace it, as it's built into >> thebattery too deeply. If you have a situation where you are doing a lot of >> heating, then using a external heating source in an insulated box can be a >> much better option. >> >> If you are doing open loop operation of the LFP battery, having built in >> internal heaters can also be problematic. Both because it can throw off the >> accuracy of an external AH counting SOC meter, and because some charging >> equipment will not respond appropriately to the battery limiting incoming >> power to that required to run the heater when the temperature gets below >> 32ºF. Some charging sources will just rise to absorb voltage till the >> batttery warms and starts accepting a charge, when it falls to battery >> voltage. But some sources can spike and cause equipment damage if the >> charging FET's or relays on the battery are opened to prevent charging at >> low temperatures. >> >> For actual low temperature operation, lithium titanate is the only >> technology I've seen that is really good -- full rate charge and discharge >> at -40ºF. Sodium ion can take lower temperatures than LFP, but not as cold >> as LTO. The products for both of these that I've seen have not been >> commercial successes due to much higher cost than LFP. Why by a real cold >> weather LTO battery for $1/watthr when you can get a heated LFP battery that >> claims to work at -4ºF, for only $0.20/watthr. Not understanding the >> limitations of the heated LFP batteries means that few people bought the LTO >> batteries instead. >> >> Zeke >> >> >>> Message: 1 >>> Date: Sun, 10 May 2026 13:19:31 -0600 >>> From: Jay <[email protected] <mailto:[email protected]>> >>> To: RE-wrenches <[email protected] >>> <mailto:[email protected]>> >>> Subject: [RE-wrenches] Low temp LFP >>> Message-ID: <[email protected] >>> <mailto:[email protected]>> >>> Content-Type: text/plain; charset=utf-8 >>> >>> Hi all >>> >>> I had someone ask me about what eco worthy is selling. A low temp LFP >>> battery. They say charging at -4?F >>> >>> Is this actually something new, a new chemistry or just marketing? >>> >>> Thanks. >>> >>> Jay >>> >>
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