[trickle]

i bet the front of the module will warm much easier, if heat can't shoot out the back like it was, i would picture the heat in the middle will want to go towards the front more than it did before.

 

[mudder]

Those bolt-on resistors and PCB resistor changes did wonders balancing out cell temps!
I've got all cells in the 18S-- configuration to within 3 degC, which is good enough for me.
Since these bolt-on resistors bump the power up from 50 to 80 watts, I'm now also able to get all three modules up to 32 degC when it's -7 degC outside... that's a 40 degree temp rise**, which is about ten more degrees than I think we'd even need... but there's really no reason to dial it back, since LiBCM will just turn the heating elements on and off as needed. If anything, I'll bump up to the next-highest common (E192) resistance value when I specify the actual resistors.

I just started what is hopefully the final 18S-- test, which adds foam insulation:
-between the 12S module and the junction board (with cutouts for HVDC current cables), and;
-between the outer 18S module and the clear cover (with a channel for the 18S-- HVDC current cable that runs through that cavity).

...

After finishing that last 18S-- test (tomorrow morning), I'll circle back around to the 18S+- configuration and see how well my findings apply to 18S+-.

**Previously I 'observed' the same temperature rise, but that was only as measured by the temperature sensor in the middle of each module. The 30 extra watts applied by these bolt-on resistors removes the cell temperature gradient, but of course uses more power.

 

[trickle]

excellent breakthrough, i would imagine the insulation is going to get very warm on the sides.. hopefully not tooo warm.. super awesome libcm can just cycle it on/off... i picture it like being a microwave kicking on and off on defrost mode.. the indirect 30 watts therefore shouldn't really be a waste if libcm doesn't have to run 100% duty cycle.. should be plenty of 'off time' that helps conserve power i would think.. great job mudder, thanks for the videos and feedback, as frustrating as this has been it's great to see that people will have warm batteries. i want to see a user jump start a gas car now lol, that would be the cherry on top

 

[mudder]

Insulating just the left and right sides improved performance much more than I had anticipated. I was able to maintain the same 40 degree delta with 25% less power. I also realized I can use LiBCM's onboard balancing resistors to keep that end of the pack warm, too... that's an additional 10 watts on the LiBCM side. So at this point I've got additional heating on both ends, without obstructing airflow. 18S-- data gathering is complete.

18S+- test in progress now. So far the module temps are much more uniform than before (i.e. the middle cell is no longer running away). The two pieces of foam on either side of the pack are really doing wonders.

Before I can ship these kits out, I need to order new resistor values (based on the data I gathered these past few days).
From a software perspective, I'm thinking there's no longer any reason to run the fans when it's cold... the resistance heaters are much more effective at concentrating heat into the pack when the fans are off. Given how long the engine takes to heat up in the winter, I suspect that by the time the cabin air is warm, the resistance heaters will have already surpassed the cabin air temperature. It's looking like the LiBCM Heater Kit can heat the cells 10 degC per hour.

FYI: LiBCM can automatically detect whether the LiBCM Heater Kit is installed. I'm thinking about the following user settings in config.h:

HEATER_DISABLE_BELOW_SoC_PERCENT 50 //when car off and grid charger unplugged
HEATER_KEEP_PACK_ABOVE_TEMP_C_KEYOFF 5 //Lower temperatures conserve power //Recommended range: 5 to 30 degC
HEATER_KEEP_PACK_ABOVE_TEMP_C_KEYON 20 //in extremely cold environments, set to 30 degC to store extra heat in pack (e.g. for overnight outdoor storage)
HEATER_KEEP_PACK_ABOVE_TEMP_C_GRID 20 //when grid charger plugged in
HEATER_KEYOFF_DELAY_BEFORE_USING_HOURS 5 //LiBCM waits this many hours after keyOFF before heating pack //conserves power overnight


Let me know if y'all have any other user-configurable firmware ideas.

 

[joeaax1j]


HEATER_KEEP_PACK_ABOVE_TEMP_C_KEYON 20 //in extremely cold environments, set to 30 degC to store extra heat in pack (e.g. for overnight outdoor storage)


Thanks, Mudder! I'm not sure I understand the above config option. For extremely cold overnight outdoor storage, the person needs to leave the key in the "on" position all night?

 

[mudder]

No, the key doesn't need to be on. What I was trying to say is that setting the KEYON heater setpoint higher allows LiBCM to preheat the battery to a hotter temperature while you're driving and power is 'free' (or at least 'unlimited'). So for example say you drive around for three hours... during this time, if you use the default 20 degC value, as soon as the pack heats up to 20 degC, LiBCM turns off the heater. Then, when you turn the car off and park overnight, the starting pack temperature is only 20 degC. Whereas, if you change the KEYON value to 30 degC, then while you're driving around LiBCM will heat the pack to 30 degC, so that when you turn the car off and park overnight, the starting pack temperature is now 30 degC.

Even the above explanation is wordy... if someone understands what I'm saying and wants to write it more clearly, be my guest.

Maybe I should just replace that user config option with:
HEATER_KEEP_PACK_ABOVE_TEMP_C_KEYON 20 //while driving, LiBCM will heat the pack to this temperature

And maybe I should rename the above parameters:

HEATER_DISABLE_BELOW_SoC_PERCENT //When keyOFF and grid charger unplugged, pack heater disabled if SoC below this value
HEATER_SETPOINT_DEGC_KEYOFF //When keyOFF, LiBCM enables heater below this value
HEATER_SETPOINT_DEGC_KEYON //When keyON, LiBCM enables heater below this value
HEATER_SETPOINT_DEGC_GRID //When grid charging, LiBCM enables heater below this value
HEATER_KEYOFF_DELAY_BEFORE_HEATING_HOURS //When keyOFF and grid charger unplugged, LiBCM waits this many hours after latest keyOFF before heating pack //conserves power overnight


 

[joeaax1j]

Thanks for the explanation. That makes sense. I like the wording changes.

 

[Arbus]

Given how long the engine takes to heat up in the winter, I suspect that by the time the cabin air is warm, the resistance heaters will have already surpassed the cabin air temperature.

Run the fan backwards!

 

[mudder]

More parts shortage headaches... based on my test results, the 18S heater PCBs need either 6k34 or 6k48 2010 resistors... and they just aren't in stock anywhere. The only thing in stock anywhere is a $0.30 precision part, which adds an unexpected additional $107 in BOM cost per kit. This is a non-starter, but even if it wasn't, there are only enough $$$ parts for sale worldwide to build QTY3 kits.

It blows my mind that in 2022 I still can't purchase discrete passive SMT resistors.
I haven't exhausted my search yet, but this is just ridiculous.

...

Update: I ended up modifying the other heater kit resistor values in order to use an in-stock 6k2 resistor. Purchased enough parts to build QTY5 5AhG3 Heater Kits... for the five people who have reserved this time-suck, money pit kit. If you haven't signed up yet, you won't be in the first batch. If there's no real demand, there might not be a second batch, which is fine because I'd much rather work on other LiBCM stuff.

 

[davismltc]

Let me know if y'all have any other user-configurable firmware ideas.

If it's not too much trouble, maybe add:

CHARGE_DISABLE_BELOW_DEGC //LiBCM disables regen & charging below this value

Here are datapoints collected recently regarding LiBCM's temps (Goog is from my phone):
Time Goog Thermostat LiBCM. . . .Diff
04:00p 50F 10.5(50.9F) 12C(53.6F) 1.5
04:15p 49F 09.8(49.6F) 12C(53.6F) 2.2
04:41p 48F 09.3(48.7F) 11C(51.8F) 1.7
05:06p 47F 08.9(48.0F) 11C(51.8F) 2.1
06:08p 43F 06.6(43.8F) 10C(50.0F) 3.4
07:39p 38F 03.3(38.0F) 08C(46.4F) 4.7
08:28p 35F 02.3(36.1F) 07C(44.6F) 4.7
09:12p 33F 01.1(34.0F) 06C(42.8F) 4.9
09:38p 32F 00.7(33.3F) 05C(41.0F) 4.3
10:16p 31F 00.0(32.0F) 04C(39.2F) 4.0 (0*C Actual)

05:30a 25F -4.2(24.4F) -02C(28.4F) 2.2
06:10a 26F -4.0(24.8F) -02C(28.4F) 2.0

 

[tervic]

More parts shortage headaches... based on my test results, the 18S heater PCBs need either 6k34 or 6k48 2010 resistors... and they just aren't in stock anywhere. The only thing in stock anywhere is a $0.30 precision part, which adds an unexpected additional $107 in BOM cost per kit. This is a non-starter, but even if it wasn't, there are only enough $$$ parts for sale worldwide to build QTY3 kits.

It blows my mind that in 2022 I still can't purchase discrete passive SMT resistors.
I haven't exhausted my search yet, but this is just ridiculous.

...

Update: I ended up modifying the other heater kit resistor values in order to use an in-stock 6k2 resistor. Purchased enough parts to build QTY5 5AhG3 Heater Kits... for the five people who have reserved this time-suck, money pit kit. If you haven't signed up yet, you won't be in the first batch. If there's no real demand, there might not be a second batch, which is fine because I'd much rather work on other LiBCM stuff.

Geez, thanks for putting the effort into this...
I'm disappointed that only five of us have been interested in this. I guess there must be more owners in the "Tropics" than out here where it gets cold!

 

[davismltc]

I appreciate all of Mudder's effort as well. He's doing a fantastic job!

Only five orders?
My guess is folks don't realize permanent damage occurs when charging lithium batteries at or below freezing. To me, it's not worth the risk damaging the HV battery, especially since a replacement will be somewhat scarce and pricey.

Additionally, the way the lithium cells are oriented within the OEM battery case, cabin air alone is unlikely to heat the cells adequately. These cells don't self-generate much heat, and it's going to take Mudder's solution, or some other method to maintain an adequate cell temp around the freezing mark. I'd have concern about overnight road trips to cold climates without it (unless regen was disabled). I guess it depends on how much damage you're willing to risk.

...and how much you don't mind driving without assist while regen is disabled..

 

[mmdepace]

That is surprising. Still considering it and it doesn't get to 0C outdoor temperatures here. If I ever remove the cell packs, will definitely order. Also, couldn't imagine building a new LiBCM pack anywhere in the coutry without installing these as essential hardware to protect the investment.

 

[Arbus]

My guess is folks don't realize permanent damage occurs when charging lithium batteries at or below freezing.

Yep. There are good reasons most vehicles use active heating on their lithium batteries.

 

[trickle]

I would like to share my thoughts, before this gets out of control
I certainly hope people who need to be on that list (post #229) got on it, this whole thread was based on a thought that i had and wanted for myself. I brought light to it because in the lower 48 i am the first person to recieve winter and the last to see it leave. I know how difficult it is to keep things warm outside when it gets nasty out. I want to be clear and open right now about where i stand. Mudder sold me on libcm back in April, in an old thread, I was coming out of cold weather with this in the back of my mind.
Supply shortages have messed up everybody's lives, it hurts me when somebody as nice as mudder is affected. i have been working construction for the last few years where it is getting exponentially harder for normal people to afford the basics. I myself have been forced to stick unfamiliar irons in the fire just to keep the lights on at home. I worked diligently all summer/fall to be able to afford an libcm that mudder built. It wasn't the lithium that sold me, it was the man behind it.
In my only defense, my intentions were to start this problem before cold neighbors could wreck their batteries. I'm low tech and it simply amazes me that mudder took on this challenge and has brought it to what it is in such a short period of time.
I feel if i wouldn't have started the fire, somebody else may have literally started a fire with a cheap chinese heater on an extension cord weeks later. I have cheered him along best as i can to get it sorted out because of it's importance, the man deserves way more credit than only i can give. I 100% agree that he should move on

 

[joeaax1j]

@trickle This thread took on a life of its own, but there were several other discussions in other threads about LiBCM functionality in sub-freezing temps, so don't feel guilty. I'm one of the ones that filled out the form for the heater solution and am excided to buy and install it, even though I also have also filled out the form to replace my 5AhG3 solution with the 47Ah FoMoCo solution. I imagine that I will be moving my 5AhG3 LiBCM to my second Insight.

 

[trickle]

i'm trying my best to not feel guilty after seeing the amount of work mudder spent making a safe heater solution for folks, when it gets cold out it's human nature for people to take it too lightly. I have people around me every year that procrastinate for cold temps because it's a bear to deal with. it's super sad when these cheap overseas extension cords/heaters have become an everyday part of people's lives and ultimately their eternal fate. all it would take to wreck mudder's dream is for someone to get lazy and last minute run to the dollar store and buy the cheapest thing they can get their hands on.. when those things run non stop out in a cold garage/ possibly attached to the house/ it is a HUGE fire hazard. my biggest fear is they would try to cover up the facts. i have poked around and researched plenty to know anything mudder sells has safety as a number one top priority to cover his end. however the image it would portray would wreck it for everybody. If people don't like me for bringing it up, i'll deal with it. if mudder doesn't like me bringing it up, i will listen, because i respect his intuition. but i want to see his dream have a happy ending where he helps all these people have simple solution for their own benefit. my insight has literally paid for itself with gas prices and has helped me pay bills and keep the refrigerator stocked with food. I love the community aspect and how people are fighting to keep these cars on the road.
Now that light has been shined on the subject i pray people think safe and prepare for cold.
I could also care less if i get black listed from libcm fomoco heater if it's too hard to make safe for all of these reasons. i bought 47ah batteries with high hopes, but if it is too difficult, i wouldn't blame the man one bit for pulling the plug on it. I don't want to be that burden and am still willing to support him however "if i can". i know it doesn't look like im supporting him to the non heater crowd but i promise it's for everybody's good. Now i'm stressing that he is going to have to respond, and i don't want there to be any tension over the matter. period. If he wants to do whatever, He certainly should. It's a free country.

Edit: forgot to reiterate that priority at the moment is getting patient existing customers out of beta as they very much deserve it

 

[mudder]

i'm trying my best to not feel guilty after seeing the amount of work mudder spent making a safe heater solution for folks, when it gets cold out it's human nature for people to take it too lightly. I have people around me every year that procrastinate for cold temps because it's a bear to deal with.

I wouldn't feel guilty about it. Sub zero pack heating is a fair ask, and now it exists.
I'm still amazed Honda doesn't design it into their vehicles that use these same modules. However, they know more info about how the cell handles cold weather, and also they're probably not worried about maximizing battery life as I am... their engineering team is probably designing around the warranty expiry, whereas I'm wanting to keep these cells working as long as possible.

it's super sad when these cheap overseas extension cords/heaters have become an everyday part of people's lives and ultimately their eternal fate.

It saddens me that so many people are so comfortable with cheap crap. It took too long for me to understand why a $300 drill costs $300.

all it would take to wreck mudder's dream is for someone to get lazy and last minute run to the dollar store and buy the cheapest thing they can get their hands on.. when those things run non stop out in a cold garage/ possibly attached to the house/ it is a HUGE fire hazard. my biggest fear is they would try to cover up the facts.

If I've learned anything from Tesla, it's that lithium car fires aren't good for brand image. I am very conservative with the cells. In cold weather the pack heater will add to that safety margin.

i have poked around and researched plenty to know anything mudder sells has safety as a number one top priority to cover his end. however the image it would portray would wreck it for everybody. If people don't like me for bringing it up, i'll deal with it. if mudder doesn't like me bringing it up, i will listen, because i respect his intuition.

I am very safety focused. This stems from having to pass each product design through NI's internal safety team. All products operating anything above 30 Vac / 60 Vdc had to pass their rigorous gauntlet. I honestly miss having a qualified 3rd party engineering team audit my work for safety.

I have zero issues with anyone bringing up any potential issue related to safety, whether or not an issue actually exists.

but i want to see his dream have a happy ending where he helps all these people have simple solution for their own benefit. my insight has literally paid for itself with gas prices and has helped me pay bills and keep the refrigerator stocked with food. I love the community aspect and how people are fighting to keep these cars on the road. Now that light has been shined on the subject i pray people think safe and prepare for cold.

I'm routing for "happy ending", too. If not, worst case a litigious plaintiff is going to get enough raw materials to build as many LiBCMs as they want... if anyone is still buying them after this hypothetical Linsight bonfire. I would hope it never came to that.

I certainly haven't 'saved' any money with the LiBCM project, but I'm having a great time designing whatever I want. It's so refreshing not building someone else's dream... in a previous life as CTO at a startup, even though I designed the product roadmap and was super passionate about the application, it was ultimately not entirely my dream. I loved it, but it wasn't 'mine'. LiBCM is 'mine'.

I could also care less if i get black listed from libcm fomoco heater if it's too hard to make safe for all of these reasons.

I haven't talked about it much, but I actually developed and tested the FoMoCo heater solution in parallel to the 5AhG3... it's presently installed in my car and working well. Next time I take the pack out, I'm going to see about adding a thin insulation layer underneath the aluminum tray... but otherwise the concept works and just needs some fine tuning.

i bought 47ah batteries with high hopes, but if it is too difficult, i wouldn't blame the man one bit for pulling the plug on it. I don't want to be that burden and am still willing to support him however "if i can".

There's 0% chance I pull the plug on FoMoCo. All subsystems in my prototype unit are 100% where I want them, and I'm probably 90% done designing the hardware I'll end up selling next year. The only hardware I still need to finish is laying out the daughterboard PCB (which is required for the 1500 watt charger, and also included in that upgrade cost).

FoMoCo is 100% happening. As is the FoMoCo heater.

i know it doesn't look like im supporting him to the non heater crowd but i promise it's for everybody's good.

I'm seeing your support every time you post. I really enjoy your feedback, banter, encouragement.

Now i'm stressing that he is going to have to respond, and i don't want there to be any tension over the matter. period.

None. Zero.

Edit: forgot to reiterate that priority at the moment is getting patient existing customers out of beta as they very much deserve it.

First heater PCBs, then final push to exit beta. Honestly I'm a bit perplexed that beta customers are so eager to stop updating their firmware. I can say for certain that until I'm confident there aren't any major firmware safety issues, LiBCM will retain the time-based firmware expiration. Maybe I'll increase the period from 40 to 90/180 days, but it just doesn't make sense to risk customers never updating the firmware again. I like that beta customers are forced to update firmware... it all but guarantees older LiBCM firmware won't exist.

Ideally LiBCM would support automatic over-the-air updates, but that feature would require an entire engineering team, per-month wireless data fees, etc. I'd rather focus on the core product, with the minor inconvenience that beta customers need to spend 5 minutes every month loading the latest firmware. It's a small ask. Certainly I could improve the software experience, but again that's attention I'd rather focus elsewhere for now.

 

[mudder]

That is surprising. Still considering it and it doesn't get to 0C outdoor temperatures here. If I ever remove the cell packs, will definitely order. Also, couldn't imagine building a new LiBCM pack anywhere in the coutry without installing these as essential hardware to protect the investment.

I wouldn't order the heater kit if your car will never drop below 0 degC.
I would order the heater kit if your car will never drop below 0 degF.

 

[mudder]

I appreciate all of Mudder's effort as well. He's doing a fantastic job!

Only five orders?
My guess is folks don't realize permanent damage occurs when charging lithium batteries at or below freezing. To me, it's not worth the risk damaging the HV battery, especially since a replacement will be somewhat scarce and pricey.

Additionally, the way the lithium cells are oriented within the OEM battery case, cabin air alone is unlikely to heat the cells adequately. These cells don't self-generate much heat, and it's going to take Mudder's solution, or some other method to maintain an adequate cell temp around the freezing mark. I'd have concern about overnight road trips to cold climates without it (unless regen was disabled). I guess it depends on how much damage you're willing to risk.

...and how much you don't mind driving without assist while regen is disabled..

I suspect that in cold weather climates, the Heater PCB Kit will add years to cell lifetime. Particularly if you leave the car plugged in during extended sub zero storage... or if you drive often enough for the heaters to heat up the pack while driving. Lithium batteries like the same temperatures people do, and suffer just as well in cold weather. Most vehicle BMS systems actually keep a waterfall graph showing temperature, SoC, and time on the X/Y/Z axes, respectively. This lets car manufacturers see post-facto how much each grid coordinate (e.g. a specific temperature at a specific SoC) affects battery life. It'll eventually exist in LiBCM, too... just need to write the firmware.

And yes, 15 years from now it'll be interesting to see if there are compatible cells at a reasonable price. Obviously Honda will still offer them to existing Honda owners, but at what price.