Unregulated lithium ion battery charge/discharge management

[Muhendis]

The BMS (battery management system) is a bunch of electronics used to control and limit the current passing into and out of a lithium battery pack. It also limits the charge voltage to a level so as not to overstress the battery. A battery cell monitoring circuit is generally included in the BMS which is used to make sure all the cells get charged to the same level.

 

I have seen cheap e-bikes on sale in Thailand. There is definitely no battery cell monitoring going on and the BMS must be presumed to be in the charger if it exists at all. 

 

If you buy one of these cheap e-bikes the result could be this:

 

https://news.sky.com/story/call-for-government-to-fund-safe-e-bike-subsidies-after-battery-fire-12915065

 

 

[OneMoreFarang]

13 minutes ago, Muhendis said:

I have seen cheap e-bikes on sale in Thailand. There is definitely no battery cell monitoring going on and the BMS must be presumed to be in the charger if it exists at all. 

I share your concern about Lithium battery fires. 

 

But electronics can be cheap and without any regulation the batteries would die on the first charge.

There will be some electronics. How good or bad or reliable is a different question.

 

[Muhendis]

39 minutes ago, OneMoreFarang said:

But electronics can be cheap and without any regulation the batteries would die on the first charge.

There will be some electronics.

Electronics can indeed be cheap. There is, of course, some degree of electronics regulation because all these e-bike are fine being recharged. But that could be only constant voltage with no current limit. A high internal resistance cell would overheat possibly to the level of combustion.

 

44 minutes ago, OneMoreFarang said:

How good or bad or reliable is a different question.

This is where the other type of regulation comes in. There are regulatory authorities tasked with protecting consumers from being sold goods of dubious/dangerous quality. They require government legislation to act against these shoddy goods. So governments need to get their fingers out and pass legislation to ensure the unaware consumer has some sort of protection.

[OneMoreFarang]

3 minutes ago, Muhendis said:

This is where the other type of regulation comes in. There are regulatory authorities tasked with protecting consumers from being sold goods of dubious/dangerous quality. They require government legislation to act against these shoddy goods. So governments need to get their fingers out and pass legislation to ensure the unaware consumer has some sort of protection.

Sure

 

But then there are those people who think they are smart and who buy cheap. And then they are surprised when bad things happen. How could that possibly happen? ... 

[KhunLA]

Have 2 batteries for my ebike, one inexpensive, and not surprisingly, and expected, I got what I paid for, and I believe it has already died.  And a quick death at that.

 

I've taken it off the bike, (as I don't trust it) and will test one more time, but not optimistic.

[Muhendis]

1 minute ago, OneMoreFarang said:

Sure

 

But then there are those people who think they are smart and who buy cheap. And then they are surprised when bad things happen. How could that possibly happen? ... 

Yes I agree. There are many who think they have enough knowledge to overcome all obstacles. That is where regulatory authorities come in. They will require these e-bikes to have been type tested and a certificate of conformancy issued. This would be much the same as washing machines and other domestic appliances. Maybe have the BSI  Kite Mark

 

[Muhendis]

5 minutes ago, KhunLA said:

Have 2 batteries for my ebike, one inexpensive, and not surprisingly, and expected, I got what I paid for, and I believe it has already died.  And a quick death at that.

 

I've taken it off the bike, (as I don't trust it) and will test one more time, but not optimistic.

Do you know if your e-bike has battery cell balancing? 

 

It's possible that the individual cell is ok but can't charge as well as others in the string. This would cause the whole string to go down.

Edited July 5, 2023 by Muhendis

[KhunLA]

1 minute ago, Muhendis said:

Do you know if your e-bike has battery cell balancing? 

 

It's possible that the individual cell is ok but can't charge as well as others in the string. This would cause the whole string to go down.

Really haven't a clue, as not exactly a lot of specs available.  The dead/dying battery was complete false advertising, and TBH, wasn't surprised.  Only that it died as fast as it did.

 

Neither are name brand, although the 2nd one (10Ah) is quite impressive for the price.

 

The comparison of the 2 is obvious.  Dead one is 1/3 the size of the good one, but spec'd 3X better (30Ah vs 10Ah) ????  It was damn cheap though, and hindsight, now damn expensive per kms ????????

[Muhendis]

1 minute ago, KhunLA said:

Really haven't a clue, as not exactly a lot of specs available.  The dead/dying battery was complete false advertising, and TBH, wasn't surprised.  Only that it died as fast as it did.

 

Neither are name brand, although the 2nd one (10Ah) is quite impressive for the price.

 

The comparison of the 2 is obvious.  Dead one is 1/3 the size of the good one, but spec'd 3X better (30Ah vs 10Ah) ????  It was damn cheap though, and hindsight, now damn expensive per kms ????????

Best way to check for battery cell balancer is to have a look at the battery pack and see if there is a wire going to each cell terminal.

[Banana7]

Lots of e-bike fires throughout the world. If you google e-bike fires, New York and London alone had some spectacular fires. 75 fires in New York in 2021, resulting in 72 injuries and three deaths, London England had 130 similar fires.

 

If an EV car is in an accident, it too can catch fire. There are reports that it can catch fire multiple times. Some fire departments bring an open top water tanker truck to an ev car collision. If the EV is on fire, it gets dumped into the water tanker.

[OneMoreFarang]

39 minutes ago, Banana7 said:

Some fire departments bring an open top water tanker truck to an ev car collision. If the EV is on fire, it gets dumped into the water tanker.

I recently saw a video from a professional fire fighter. He showed a couple of ways which are not successful to stop those fires. His summary: Just let it burn. And try to make sure nothing else catches fire. 

 

[Banana7]

23 minutes ago, OneMoreFarang said:

I recently saw a video from a professional fire fighter. He showed a couple of ways which are not successful to stop those fires. His summary: Just let it burn. And try to make sure nothing else catches fire. 

 

The tricky part is that the fire maybe extinguished at the collision scene, as the fire department puts away their gear, the fire erupts again. Sometime, the vehicle bursts into flames a third time as it is being towed away.

 

Have  a look:

 

Edited July 5, 2023 by Banana7

[Muhendis]

2 hours ago, Banana7 said:

The tricky part is that the fire maybe extinguished at the collision scene, as the fire department puts away their gear, the fire erupts again. Sometime, the vehicle bursts into flames a third time as it is being towed away.

Yeah.

The problem is, the fire is the result of a chemical reaction. Once the lithium ion battery gets to a temperature of 345ºC (I think) the chemical reaction starts quite violently. generating more heat which speeds up the reaction and becomes self perpetuating.

To successfully extinguish that sort of fire the temperature needs to be brought down and kept down.

That's all well and good but the original cause (short circuit?) of the high temperature also needs to be removed plus any newly acquired short circuits. This is a likely reason to let the fire burn itself out. So it's bye buy ESS. Bye buy e-bike and bye buy e-car.

Don't worry too much. It rarely happens.........????

[Crossy]

12 minutes ago, Muhendis said:

Don't worry too much. It rarely happens.........????

 

And LiFePO4 packs are much less likely to go fzzt!

 

[Bandersnatch]

15 minutes ago, Crossy said:

 

And LiFePO4 packs are much less likely to go fzzt!

 

[Muhendis]

21 minutes ago, Crossy said:

 

And LiFePO4 packs are much less likely to go fzzt!

 

Yes.

The addition of the iron raises the combustion temperature by about 100ºC to something like 420ºC.

In transport applications the addition of iron unfortunately decreases the time and hence miles/kilometres between charges. In other words the battery capacity is reduced.

[Crossy]

2 minutes ago, Muhendis said:

In other words the battery capacity is reduced.

 

The energy density is improving, to the point that most of the Chinese EV manufacturers are moving to LiFePO4.

 

Even Tesla are using LiFePO4 cells in their standard range models.

[007 RED]

A very recent tragic incident in the UK serves a timely reminder that these cheap e-bikes, and similar 'toys', have a potential disaster built in, and its waiting to happen.

 

An e-bike left charging in a flat was the "most probable cause" of the blaze in Cambridge on Friday (30/06/23), where a mother and two children aged 8 and 4 died.  A man in his 30s remains in a critical condition after the early morning

Cambridgeshire Fire Service said.

 

Area commander Stuart Smith said the service spent two days at the scene of Friday's fire with police and specialist fire investigation support.

 

The vehicle involved had been taken away for further testing, he said.  "All we know from the fire investigation is that the e-bike was on charge, the plug was switched on, it was connected," he said.  "The likelihood is that the e-bike overheated and then caused a fire in the charging process”.

 

"We all know that these electric scooters, e-bikes, hoverboards are starting to be used as modes of transport so they are more prevalent in people's homes when they are being charged.  "I appreciate people want them ready to use to get about during the day, so they charge them at night - but I would urge people to charge them when they are awake and alert."

 

https://www.bbc.com/news/uk-england-cambridgeshire-66096597

 

 

[Crossy]

I would encourage users of this type of pack to charge out-doors and invest in a charging bag.

 

It may not stop the spread completely, but should give you time to escape.

 

Or do what Boeing did with the 787 Dreamliner, and put the pack in a metal box.

 

https://www.lazada.co.th/products/portable-fireproof-safety-bag-lipo-guard-explosion-proof-fire-resistant-charging-sack-battery-safe-bag-for-battey-i3238269350-s12043713390.html

 

[Muhendis]

I would encourage users of this type of pack to charge out-doors and invest in a charging bag.

 

It may not stop the spread completely, but should give you time to escape.

 

Or do what Boeing did with the 787 Dreamliner, and put the pack in a metal box.

 

https://www.lazada.co.th/products/portable-fireproof-safety-bag-lipo-guard-explosion-proof-fire-resistant-charging-sack-battery-safe-bag-for-battey-i3238269350-s12043713390.html

 

 

Nice idea but how would anyone remove the battery pack on an el cheapo electric tricycle sold in Thailand by the million and driven around the villages at snails pace.

The batteries are loaded into a metal box at the supplier premises and connected to a socket ready to receive the charger power. lid of the metal box is plastic.

That Lazada thing must have been made with something else in mind. I also notice it is called a "LIPO Guard" when LIPO cells are supposed to be safer. Am I missing something?

Edited July 5, 2023 by Muhendis

[Muhendis]

6 hours ago, Crossy said:

The energy density is improving

Interesting.

Do you have any figures or links to scholarly articles please?