A question about the "missing low temp sensor" problem...

[LVLAaron]

Just saw @Will Prowse teardown the EnjoyBoy battery and it was missing the low temp sensor just like many other cheap units.


Is it possible the sensor they're using is built into the BMS? The JBD systems we use for DIY projects do have an internal sensor... maybe these do to?

 

[LVLAaron]

For clarity.. I understand that using an onboard sensor would be incorrect and bad practice. I'm just curious if the chinese companies making cheap batters are doing it that way.

 

[A.Justice]

I've wondered the same thing. The fact that those temperature sensors probably cost less than a penny each in bulk make it hard for me to believe that they don't add one, ESPECIALLY considering the fact that low temperature charging can cause permanent damage.

Edit: Accidentally posted while drafting.

 

[LVLAaron]

I've wondered the same thing. The fact that those temperature sensors probably cost less than a penny each in bulk make it hard for me to believe that they don't add one, ESPECIALLY considering the fact that low temperature charging can cause permanent damage.

Edit: Accidentally posted while drafting.

Yes, they're cheap to add... but the cost adds up when you have to pay slave labor to assemble them

And I'm sure they dont' care if you ruin the battery and need to buy another one

 

[Will Prowse]

Just saw @Will Prowse teardown the EnjoyBoy battery and it was missing the low temp sensor just like many other cheap units.


Is it possible the sensor they're using is built into the BMS? The JBD systems we use for DIY projects do have an internal sensor... maybe these do to?

If there is one mounted in the bms, it would not work to assess the temperature of the cells. And that internal sensor on the JBD is for the mosfets, and required to ensure over temperature event does not occur on the bms.

 

[Will Prowse]

For clarity.. I understand that using an onboard sensor would be incorrect and bad practice. I'm just curious if the chinese companies making cheap batters are doing it that way.

Now I read this comment second, and yes absolutely. It blows my mind that they do not add this to every pack. Such a cheap and basic feature to add.

 

[Steve_S]

It almost seems like a lot of these just are content to get 95% of the way to "Just Right" and give up. Dual Temp Sensors capable of Hot/Cold registration are CHEAP, hell even a BT Module on a BMS costs less than $2 USD @ manufacture. And considering they likely buy batches of BMS' in 1000 Lots so in the end they may spend an extra $5 total per unit and could even markup by $10 and the customer happy rating would increase. Maybe it is a support issue that the companies cannot offer support for a BT App etc ?

It isn't the first time that Will has run across a " It's Amazingly Great but for this One Tiny Ommission that screwed it up".
Will, maybe you should write up a quick "Cheat Sheet" of what you envision as the best "Affordably reasonable" Prebuilt Battery assemblage and send that to these companies. I'd be surprised if any listened but there seems to be a couple who ARE "listening and hearing" and adjusting accordingly.

 

[Rednecktek]

So what are the chances that the BMS's being used have the capability to do low temp, but the sensor just didn't get installed. Could they be fixed with a probe and a soldering pen?

 

[Rbertalotto]

Can we simply put a battery in a freezer that advertises Low Temp Sense, but we can't find it hanging on a piece or wire? How hard would it be to have it as part of the circuit board? It only need to read absolute temperature of it environment, all heat sources considered.......No?

 

[LVLAaron]

Can we simply put a battery in a freezer that advertises Low Temp Sense, but we can't find it hanging on a piece or wire? How hard would it be to have it as part of the circuit board? It only need to read absolute temperature of it environment, all heat sources considered.......No?

It shouldn't be on the circuit board, because the BMS will get warm if it's discharging. The cells might still be frozen, but the board could be warm.

 

[Quattrohead]

Can we simply put a battery in a freezer that advertises Low Temp Sense, but we can't find it hanging on a piece or wire? How hard would it be to have it as part of the circuit board? It only need to read absolute temperature of it environment, all heat sources considered.......No?

I am thinking this too. It is somewhat better the have a thermistor on a wire so that it can touch a battery to get a more accurate temperature but I think the bulk of the whole battery unit will be around the same temperature in almost all circumstances. So I do think a freezer test is more technically the correct thing to do.
I also think the battery manufacturers would have been hot to correct the lack of low temp cutoff for charging or be keen to correct the reviews that might have called them out incorrectly.
I think these tests need to be revisited.

 

[A.Justice]

It shouldn't be on the circuit board, because the BMS will get warm if it's discharging. The cells might still be frozen, but the board could be warm.

It SHOULDN'T be, but IS it? ?

 

[eXodus]

It shouldn't be on the circuit board, because the BMS will get warm if it's discharging. The cells might still be frozen, but the board could be warm.

Modern cells are not freezing at 0C

Now I read this comment second, and yes absolutely. It blows my mind that they do not add this to every pack. Such a cheap and basic feature to add.

Will I agree with low temp charging protection. I do not like the 0C disconnect. That's a last resort crutch. Like a safety belt. We should be smarter than that.

A disconnect is one way of doing the protection. There are many more ways available.

Low temp throttling of charging as a feature of the BMS.
Low temp shut off charging as a feature of the charger.
Low temp throttling as a feature of charger.

Discharge first then charge to unfreeze the cells.

Etc there are probably a few more ways aside the disconnect.

 

[Will Prowse]

It SHOULDN'T be, but IS it? ?

I have frozen a couple cheap ones and they did not have low temp charging protection on the board. I could try again. It takes a lot of time to get these packs down to that temperature.

I wish MPP or Growatts had a low temp charging protection feature and remote sensor. That would be awesome. But yes, lots of ways to accomplish low temp charging protection.

 

[eXodus]

I have frozen a couple cheap ones and they did not have low temp charging protection on the board. I could try again. It takes a lot of time to get these packs down to that temperature.

I wish MPP or Growatts had a low temp charging protection feature and remote sensor. That would be awesome. But yes, lots of ways to accomplish low temp charging protection.

You got a lot of influence on those kind of developments. When you keep asking for a 0C disconnect in your videos we will get them.

But ask yourself is it the best solution?

People watching you as a trusted resource. Manufacturer will over time add what ever you and other solar influencers ask to satisfy customer demand.

Remember how bad batteries had been only 5 years ago. You got the power to nudge the industry in a desirable direction. And finding solutions for the below 0C market would open up LFP to wider range of climates.

 

[LVLAaron]

Modern cells are not freezing at 0C


Will I agree with low temp charging protection. I do not like the 0C disconnect. That's a last resort crutch. Like a safety belt. We should be smarter than that.

A disconnect is one way of doing the protection. There are many more ways available.

Low temp throttling of charging as a feature of the BMS.
Low temp shut off charging as a feature of the charger.
Low temp throttling as a feature of charger.

Discharge first then charge to unfreeze the cells.

Etc there are probably a few more ways aside the disconnect.

All of those things are fine if you're building a "real" system - These cheap batteries are made for every day consumers who just want to drop batteries into their campers. Believe me, I'm in some camper groups on facebook and there is so much total ignorance and incorrect stuff going on it's not even funny, it's dangerous.

 

[eXodus]

All of those things are fine if you're building a "real" system - These cheap batteries are made for every day consumers who just want to drop batteries into their campers. Believe me, I'm in some camper groups on facebook and there is so much total ignorance and incorrect stuff going on it's not even funny, it's dangerous.

I know, that's why you need multiple layers of safety. Using the low voltage disconnect as only protection is like using a Breaker as a light switch.
Sure it works - but's the last thing you want to do.

The freeze-charging disconnect should be the last line of defense. Like I said - that's the safety belt.

You should not get in an accident in the first place.

My order of operations would be: (aside of developing chemistry which can cope with low temperatures, which there are many already -10C cells are available)
1. Charging reduction by the Charge controller
2. Charging stop by the charger controller
3. Charging reduction by the BMS
4. Heating the cells
5. Low Voltage disconnect.

 

[Gstan]

I have frozen a couple cheap ones and they did not have low temp charging protection on the board. I could try again. It takes a lot of time to get these packs down to that temperature.

I wish MPP or Growatts had a low temp charging protection feature and remote sensor. That would be awesome. But yes, lots of ways to accomplish low temp charging protection.

Will, what temperature do you think charging these batteries at would damage them? I have a couple ampere 12 volt 100 amp batteries that I use for bowfishing.
I go out late in the year. Sometimes I'm out for 3 to 4 hours and it's right around freezing.
You think I'm safe charging these in the garage after I get home? Or should I bring them in the house and let them warm up.
Believe me it's a hassle pulling them out of the boat and bring them in the house everyday but I don't want to damage them. Again I'm never out when it's under 30°

 

[LVLAaron]

Will, what temperature do you think charging these batteries at would damage them? I have a couple ampere 12 volt 100 amp batteries that I use for bowfishing.
I go out late in the year. Sometimes I'm out for 3 to 4 hours and it's right around freezing.
You think I'm safe charging these in the garage after I get home? Or should I bring them in the house and let them warm up.
Believe me it's a hassle pulling them out of the boat and bring them in the house everyday but I don't want to damage them. Again I'm never out when it's under 30°

Throw a heated blanket over them?

 

[eXodus]

Throw a heated blanket over them?

heat rises, a blanket doesn't really do much.
Insulate the batteries in solid foam boards and glue an aquarium heating film against them.

https://www.amazon.com/12V-Flexible-Polyimide-Heater-Plate/dp/B07P2RJDPL

Add a simple control like 5 degree Celsius Bimetallic switch. Those things would toggle between 5C and 10C