How-to: safely test LiFePO4 battery's cold-temp cut-off and self-heating functions?

[Mako74]

Hi all. I purchased a pair of 150Ah 12V LiFePO4 batties with BlueTooth BMS, low-temp cut-off and self-heating function (you can see more about them here: https://diysolarforum.com/threads/b...bluetooth-low-temp-cut-off-and-heating.14625/)

I'd like to test the low temp cut-off and self-heating functions prior to installing the batteries to my camper van to make sure they really work as advertised before using them in cold winter temperatures. I've seen @Will Prowse doing the low-tem cut-off testing in his many tests but haven't seen any regarding the self-heating (maybe I'vre just missed them?).

It's minus 10 degreees celcius outside so I could just freeze the batteries and start putting load on one and start charging the other to see if the said functions work, but I'm too scared I'd cause some damage to the batteries while doing so as I haven't donesuch tests before.

Any tips or resources on how I should go about doing the tests and still have a usable pair of batteries after that?

 

[jasonhc73]

Put them in the freezer and just let them freeze. If the heater thingy works, you will always get a voltage with a voltmeter.

If the BMS kicks in and opens the circuit, then you know the BMS low temp works, and the heater thingy doesn't.

But if the heater thingy works, how are you ever going to know if the low temp cutoff works?

Such a canundrum.

 

[Supervstech]

Do you have a thermal camera?
you could set them outside on some ice, if the cubes melt, you will know the heater is working.
also, measure the voltage, and when the heat kicks in, there will be a voltage drop.

 

[wholybee]

I would expect the Bluetooth BMS should be able to tell you the temperature and if it is cut off or not. I would freeze the battery, and start with checking what the BMS says. If the BMS shows it working, apply a charge voltage and monitor current and the BMS operation. You should see some current as the heater is running, but the BMS would report that the battery isn't charging.

Will tested a Kilovault battery with an internal heater basically that way.

 

[Mako74]

I would expect the Bluetooth BMS should be able to tell you the temperature and if it is cut off or not. I would freeze the battery, and start with checking what the BMS says. If the BMS shows it working, apply a charge voltage and monitor current and the BMS operation. You should see some current as the heater is running, but the BMS would report that the battery isn't charging.

Will tested a Kilovault battery with an internal heater basically that way.

Thanks! And I'll find that Will's video for reference. The BMS BT app shows the info on the images attached.

 

[Snowboardphil]

Go any tests done already ? I've inquired about the 100 Ah battery with Linda from Bely, and she would charge me 220USD for air transport to Québec City, Canada, apparently arriving after 3 weeks (more like 3 months I would guess). My understanding therefore is, for 1 x sample 100ah with bluethoot and self-heating, should hover around 595 USD (375 bat+220 ship) to north-eastern north-america. I guess it would be a good price if it all works as advertised.

Going trough what Bely offers on alibaba, for the 100ah line of batteries one can evaluate that the self-heating functionality seem priced at 80USD, the Bluetooth functionality seem priced at an additional 15 USD. (so baseline 100ah battery with no BT and self-heat would be around 500 USD delivered to my place in Québec).

 

[Mako74]

Go any tests done already ? I've inquired about the 100 Ah battery with Linda from Bely, and she would charge me 220USD for air transport to Québec City, Canada, apparently arriving after 3 weeks (more like 3 months I would guess). My understanding therefore is, for 1 x sample 100ah with bluethoot and self-heating, should hover around 595 USD (375 bat+220 ship) to north-eastern north-america. I guess it would be a good price if it all works as advertised.

Going trough what Bely offers on alibaba, for the 100ah line of batteries one can evaluate that the self-heating functionality seem priced at 80USD, the Bluetooth functionality seem priced at an additional 15 USD. (so baseline 100ah battery with no BT and self-heat would be around 500 USD delivered to my place in Québec).

Doing the capacity test. My testing seems to span several threads (sorry!), like in HERE.

I will try to compile main findings HERE.

 

[Mako74]

So I did 'a' cold temperature test with the battery and put together a short video about it on YouTube.

Main notes: when I plugged in the 15A Victron charger the relay(s) in the BMS went open/close several times (you can hear it in the video). After the relays settled in, App showed no current going in, but the multimeter showed current around 14A, This current steadily dropped to around 10A until the charging heating stopped and charging started. Would this current drop from 14A to 10A be due to the charging heating or why is the current dropping steadily?

Not looking for likes or comments on YT, but rather I would appreciate if you more experienced battery guys and girls could comment here what you think is happening with the BMS BT App when the BMS is tripping its relays before charging heating begins and also on the current during the charging heating.

Any feedback much appreciated!

 

[BenCos18]

So I did 'a' cold temperature test with the battery and put together a short video about it on YouTube.

Main notes: when I plugged in the 15A Victron charger the relay(s) in the BMS went open/close several times (you can hear it in the video). After the relays settled in, App showed no current going in, but the multimeter showed current around 14A, This current steadily dropped to around 10A until the charging heating stopped and charging started. Would this current drop from 14A to 10A be due to the charging heating or why is the current dropping steadily?

Not looking for likes or comments on YT, but rather I would appreciate if you more experienced battery guys and girls could comment here what you think is happening with the BMS BT App when the BMS is tripping its relays before charging heating begins and also on the current during the charging heating.

Any feedback much appreciated!

I think it most likely is tbh

 

[grizzzman]

So I did 'a' cold temperature test with the battery and put together a short video about it on YouTube.

Main notes: when I plugged in the 15A Victron charger the relay(s) in the BMS went open/close several times (you can hear it in the video). After the relays settled in, App showed no current going in, but the multimeter showed current around 14A, This current steadily dropped to around 10A until the charging heating stopped and charging started. Would this current drop from 14A to 10A be due to the charging heating or why is the current dropping steadily?

Not looking for likes or comments on YT, but rather I would appreciate if you more experienced battery guys and girls could comment here what you think is happening with the BMS BT App when the BMS is tripping its relays before charging heating begins and also on the current during the charging heating.

Any feedback much appreciated!

It’s likely as the voltage sags a bit amps would drop. Could be a temp. Control issue involved. Tear it apart and let us know! ?

 

[Supervstech]

All resistive loads drop amp draw as the elements heat up increasing resistance.

 

[grizzzman]

All resistive loads drop amp draw as the elements heat up increasing resistance.

Well it depends on the tech involved, as an example I have 12 DC heat cable that increases its resistance as it gets colder and decreases as it warms up.

 

[Supervstech]

Hmm.
I bet that is a control adding or subtracting heating to temp.
The resistor itself will drop ampdraw.

 

[grizzzman]

Hmm.
I bet that is a control adding or subtracting heating to temp.
The resistor itself will drop ampdraw.

The maker states that it is a chemical reaction.