[RE-wrenches] Low temp LFP

Mon May 11 07:30:04 PDT 2026

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 <jay.peltz at gmail.com> 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.
>
> [image:
> 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
> <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>
>
> <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 <
> re-wrenches at lists.re-wrenches.org> 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 <jay.peltz at gmail.com>
>> To: RE-wrenches <re-wrenches at lists.re-wrenches.org>
>> Subject: [RE-wrenches] Low temp LFP
>> Message-ID: <2FB2EBEF-72F1-466C-AB5E-892A98F042FA at gmail.com>
>> 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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-- 
Zeke Yewdall
PV Engineer
NABCEP #031508-89
zeke at darkforestsolar.com
303-523-3592
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