Batteries Charging Routine

[guerney]

As far as I understand it is exactly how it is being done. Battery is not overcharged or at least theoretically it is not. Otherwise leaving battery on charge for 12h would mean 100% guarantee of an explosion.

The green light is a simple volt meter, it indicates that the charger voltage reaches 42V. If you want to balance the pack, you have to give it time. 15 minutes should be enough for regular charging.

Would a device inline between the charger and battery, which disconnects power to the battery, when it measures a descending current of less than about 500ma(?) for 15 minutes (>15 minutes for a blance charge), prevent some fires?

 

[guerney]

Or how about a device which is triggered by power to the green LED on the charger, to initiate a timed shutdown of power to the charger, with push button options for 15 minutes, 1 hour, 24 hours etc?

 

[StuartsProjects]

Would a device inline between the charger and battery, which disconnects power from the battery, when it measures a descending current of less than about 500ma(?) for 15 minutes, prevent some fires?

What is so uncertain is what exactly is causing the recent and much publicised eBike\eScooter battery fires, so were all left guessing as to what to do.

If the cause of a battery fire is a failure of the charger then that impiles that the charger just carries on charging the battery once its reached 4.2V per cell.

So an simple and independant monitor and voltage cutoff should prevent that battery fire.

For sure if your using good quality chargers then you should not need additional protection, but in the modern so advanced on-line shopping World how can you know that what your buying is 'quality'.

 

[Woosh]

Would a device inline between the charger and battery, which disconnects power to the battery, when it measures a descending current of less than about 500ma(?) for 15 minutes (>15 minutes for a blance charge), prevent some fires?

The charging is finished when the current is < 100mA at 42V.
you would need to add an ESP32 or similar to control the charger via bluetooth or add a TFT touchscreen to the charger.

 

[Sturmey]

Batteries do wear. One of my original batteries (2017 & about 900 cycles) lately suddenly started to give reduced range. The advice often given in this case is to plug it in overnight for a long charge . Anyhow, I was suspicious that something was wrong. When I opened battery to check, I got a very sweet smell. I checked cell voltages and 9 of the 10 cell groups were perfectly balanced. But the fifth group was about .2 volts below. Anyhow after a bit of further opening up I discovered that two cells in this group were leaking the sweet smelling stuff (electrolyte).
So in my view, be very careful about batteries, especially If they start to misbehave in any way e.g. reduced range, motor/power cutouts.
Also be careful about using chargers. For example,some 48v charger plugs will fit and charge 36v batteries but this is potentially dangerous, so there is room for improvement I presume.

 

[WheezyRider]

I did say 'seems to have lost', it's a typical question when someone noticed that the bars on the LCD battery meter went down more quickly than before. I reply that the first thing to do is to leave the battery on charge for several hours to make sure that the battery is fully charged and balanced.


agreed. The green light is a simple volt meter, it indicates that the charger voltage reaches 42V. If you want to balance the pack, you have to give it time. 15 minutes should be enough for regular charging.

I don't think that's the case, it's when the current drops below a preset limit (usually around 100 mA), then the light goes green, it doesn't mean the voltage is at 42V.

 

[WheezyRider]

I think a big cause of fires is the use of incorrect chargers. Many have the same connections whether it's 24V or 48V. The average person doesn't have a clue and will just plug something in and expect it to work.

And 48V, what is that anyway? There is no proper standard as there is with 36 V. sometimes it's 13s, sometimes 14s. Then I've found that these days there seems to be a fairly lax attitude by cheaper charger manufacturers as to the specifications on output voltage, with some 42V chargers I've bought being over 43V.

I do think there needs to be a study into what causes battery packs to catch fire. Most fires seem to be during charging, but the current supplied by chargers would be insufficient in most cases to rupture a cell and cause a fire. It the voltage is too high, the BMS should step in and disconnect the charger...so where are things going wrong?

 

[Sturmey]

There is a difference in build quality of batteries. For example the faulty Phylion battery I dismantled mentioned above had 2 temperature sensors embedded between the cells with that white thermo goo stuff and also an additional thermal fuse on charging circuit also embedded. Some of the cheaper batteries have only one sensor and just loosely fitted under the blue wrapping. Some BMS's sold on ebay etc dont even seem to have a temperature sensor.
Lithium fires are not new. e.g. Dell laptops and Samsung Galaxy note are examples of recalls if I can remember. Anyhow, in the photo below, this battery is built with every cell individually fused with a tin wire between the cell and the nickle strip.. Is this over the top?

 

[WheezyRider]

Maybe its a temperature sensor for the battery ?

For the fast charging the Bosch chargers can use, 1C, you would think a temperature senor on the battery to be essential. It would also make sense if the tool the battery was connected to could use the temperature sensor as a safety power cut off.

Also a lot of the small flat Lithium Ion batteries used in cameras etc, have at least one extra connection, often labled T.

Looks like the Bosch tool batteries have a temperature sensor:



From the PCB for the 36V tool battery:

 

[guerney]

We have ignition!

Watch moment e-bike battery bursts into flames as charity warns of dangers

A video shows a lithium e-bike battery busting into flames. The video, released Electrical Safety First, was shot in a test environment as they conducted research into the dangers of these batteries. The charity says batteries for e-bikes and e-scooters should be regulated like fireworks and...

www.aol.co.uk

Fun vid.

 

[Az.]

We have ignition!
(...)

Fun vid.

Do they have a vid when they set a can of petrol on fire and call for more regulation?

 

[WheezyRider]

We have ignition!

Watch moment e-bike battery bursts into flames as charity warns of dangers

A video shows a lithium e-bike battery busting into flames. The video, released Electrical Safety First, was shot in a test environment as they conducted research into the dangers of these batteries. The charity says batteries for e-bikes and e-scooters should be regulated like fireworks and...

www.aol.co.uk

Fun vid.

So what did they do to it to make it do that? Drill into it? All sensationalist BS and no scientific analysis.

 

[Woosh]

Most fires seem to be during charging, but the current supplied by chargers would be insufficient in most cases to rupture a cell and cause a fire. It the voltage is too high, the BMS should step in and disconnect the charger...so where are things going wrong?

ruptures are accumulative.

 

[Sturmey]

Lithium cells are also potentially dangerous in that 'dendrites' can form internally in the individual cell that internally short circuits the cell and the whole parallel cell group can discharge through that cell, resulting in a 'thermal runaway' situation. I think age/abusing cell/bad quality cell (impurities)/low quality BMS etc. and of course the increase in the usage all increase the chances of this happening.

 

[saneagle]

Lithium cells are also potentially dangerous in that 'dendrites' can form internally in the individual cell that internally short circuits the cell and the whole parallel cell group can discharge through that cell, resulting in a 'thermal runaway' situation. I think age/abusing cell/bad quality cell (impurities)/low quality BMS etc. and of course the increase in the usage all increase the chances of this happening.

You guys are working yourselves up into a frenzy of hysteria. Badly made self-build batteries are something to be aware of. Which of you has one of those?

How many people in the entire history of this forum have had battery problems? How many people in the entire history of this forum had batteries that caught fire.

 

[Sturmey]

You guys are working yourselves up into a frenzy of hysteria. Badly made self-build batteries are something to be aware of. Which of you has one of those?

How many people in the entire history of this forum have had battery problems? How many people in the entire history of this forum had batteries that caught fire.

Some of these problems/odds of fire are small I agree (we will say about a million to one per day to illustrate but I dont have an exact figure). But here lies the potential problem I think in that there is a huge growth in the sale of electric scooters and ebikes (which are often grouped together in countries that have introduced legislation and in general conversation/news). So if you have a country with like 1 million ebikes/scooters and there is a million to one chance per day of a fire, then thats a fire every day.

 

[Az.]

You guys are working yourselves up into a frenzy of hysteria.

Not at all. There is definitely something going on with batteries. Problem is we don't know what, so we all (including you) work on assumptions.
I think it is a good practice to adopt some safety measures just to be safe while we wait for more information. This is why I moved my batteries to the shed for the same reason why I wouldn't keep a can full of petrol at home.
I didn't experience any battery problem resulting in catastrophic failure nor any fire at my home. I still have installed smoke sensors and have fire extinguishers. Just to be on a safe side.

 

[Woosh]

I think the safest move may be a wide adoption of intelligent 41V charger with complete history stored in the cloud so an AI can help with safety but we need to quantify the cost/benefit. Bosch may have already done that.

 

[flecc]

Lithium fires are not new. e.g. Dell laptops and Samsung Galaxy note are examples of recalls if I can remember.

Lithium cells are also potentially dangerous in that 'dendrites' can form internally in the individual cell that internally short circuits the cell and the whole parallel cell group can discharge through that cell, resulting in a 'thermal runaway' situation. I think age/abusing cell/bad quality cell (impurities)/low quality BMS etc. and of course the increase in the usage all increase the chances of this happening.

Indeed, all those laptop incidents were caused by poor cell manufacturing standards. The best manufacturers have tightened up on standards since and chemistries have improved. However I believe there are still many Chinese companies happily making low cost cells to suspect manufacturing standards, probably the source of many of these fires in scooters, rather than the chargers.

As the second of your above quotes indicates, lithium cells are intrinsically far more vulnerable than any other cell type to serious problems caused by very minor manufacturing faults. Even the best can get caught out, like Boeing with the 787 fires, and I've even had a Canon camera battery swell up inside the camera and have to be prised out with a screwdriver.
.

 

[Woosh]

However I believe there are still many Chinese companies happily making low cost cells to suspect manufacturing standards, probably the source of many of these fires in scooters, rather than the chargers.

they use unmarked reject cells and labelled them as their own, consequence of that: the cells are unmatched, the pack falls out of balance and next time, when they charge to full, the pack starts a fire.