Li-ion battery testing

[guerney]

" A battery left on charge caused a huge fire at a North Wales takeaway"

Huge takeaway fire was caused by battery on delivery e-bike, claims boss

Video footage showed the business engulfed by bright orange flames

www.dailypost.co.uk

 

[guerney]

“We would also suggest people try not to charge them when they are asleep, so that if there is an issue they can react quickly.”

Another e-bike battery safety warning as charity warns that dangerous chargers are "freely available"

London Fire Brigade has renewed its e-bike battery safety warning after a fire in a high-rise block of flats in south-east London last week. The charity Electrical Safety First has also called for tighter regulation, as it says dangerous e-bike chargers remain freely available from online...

ebiketips.road.cc

 

[Bikes4two]

• This leaving batteries on charge overnight being the (possible) cause of fires -
• I don't think leaving them on charge per se is the problem but rather something else in the charger/battery system that is causing the fires, but what, I don't know.
• I mean, our laptops, mobile phones and many other domestic devices have lithium batteries in them and we don't blink an eye at leaving them plugged in.
• Dodgy battery cells, poor battery construction, poorly regulated charger, BMS not working properly?

As an aside and not directed at anyone in particular here, ebike battery fires make good headlines in the press/media (and this forum) and one can see growing hysteria about such fires - I'd advocate exercising caution before promulgating such stuff and for making unsubstantiated claims (e.g as in just repeating what's been read on the web unless demonstrably credible).

If the hysteria continues one can see all sorts of restrictions emerging from you 'you can't park your ebike here' to not being able to build your own batteries or only being able to use batteries that are factory made to approved standards.

 

[Nealh]

Personally I think it is common sense not to leave a battery on an over night charge regime.
For my phone I use a timer as for my laptop only when I'm using it , is it charged.
The ebike battery I will put on a timer but not when I'm sleeping.

 

[matthewslack]

• This leaving batteries on charge overnight being the (possible) cause of fires -
• I don't think leaving them on charge per se is the problem but rather something else in the charger/battery system that is causing the fires, but what, I don't know.
• I mean, our laptops, mobile phones and many other domestic devices have lithium batteries in them and we don't blink an eye at leaving them plugged in.
• Dodgy battery cells, poor battery construction, poorly regulated charger, BMS not working properly?

As an aside and not directed at anyone in particular here, ebike battery fires make good headlines in the press/media (and this forum) and one can see growing hysteria about such fires - I'd advocate exercising caution before promulgating such stuff and for making unsubstantiated claims (e.g as in just repeating what's been read on the web unless demonstrably credible).

If the hysteria continues one can see all sorts of restrictions emerging from you 'you can't park your ebike here' to not being able to build your own batteries or only being able to use batteries that are factory made to approved standards.

The difference with phones etc is that almost all use a single cell, eliminating at a stroke all the issues that arise from balancing and degradation of individual cells and interconnections. So long as the charger output voltage is accurate it is hard for anything to go wrong.

 

[guerney]

As an aside and not directed at anyone in particular here, ebike battery fires make good headlines in the press/media (and this forum) and one can see growing hysteria about such fires - I'd advocate exercising caution before promulgating such stuff and for making unsubstantiated claims (e.g as in just repeating what's been read on the web unless demonstrably credible).

Batteries only have to take up smoking once; appear to find it as terminally addictive as people - despite such happenings being rare, I've rethunk my battery storage habits and will keep it in a steel box wrapped in a fire blanket atop a flagstone while charging, situated so exits aren't blocked, because it's present off-bike accommodation (steel wheelbarrow) will be soon be needed at my remote veg garden. Trouble is steel melts at 1,205-1,370 °C, glass fiber fire blankets burn at 1200 °C and lithium ion battery fires burn hotter than both at over 2,000 °C... and one happening is enough to seriously disrupt the schedule of one's hobbies, possibly permanently. My efforts will merely slow it down a little, which isn't totally useless; would buy a little time. I already have a steel box I can drill a hole through for the charger connector, but could buy one of these into which my battery will just about fit diagonally I think:

Pardon our interruption...

 

[Bikes4two]

Well, there's Risk Averse and RISK AVERSE! but I understand that you have to be comfortable with what ever you do.

If such nervousness were more wide spread then that would be the end of the ebike industry, so for the rest of us, please consider being more conservative on how you share your views before the hysteria I mentioned becomes more wide spread.

 

[guerney]

If such nervousness were more wide spread then that would be the end of the ebike industry

I very much doubt my linking of a few of the recent news stories of the few relatively few ebike lithium-ion battery fires which do get reported and written about (with scant detail ) by online newspaper websites, on this quiet forum, will make any difference to the overall health of the ebike industry.

 

[guerney]

Why don't you use something like this: You preset the end voltage you want, and the charger is turned off when the battery gets there.

You could set say 41v as a safe upper limit to terminate the charge where you could top it off a little bit more before you ride if you wanted, or say set to 36-37v if you want a safe long-term storage charge.

I've seen them for about £10 before - maybe a little more nowadays (apologies for my crude image cutting and pasting).

View attachment 50273

Thanks for linking that. I could use a timer aswell, in case that fails at some point, as everything electronic does eventually. A Sinclair ZX81 still functions, controlling my central heating system, so perhaps a new low power device could also function for many years. I was thinking of making a 12V charger for a couple of old lead-acid batteries I've scavenged from a escooter I found, using an old PC power supply, and I could route it through this device. A device which monitors decreasing voltage and cuts it off when a user-assignable value is reached (plus a variable for timed cutoff after a certain low voltage is reached, for balance charges), is preferable foe my ebike battery, but doesn't appear available to buy - I'm unsure as to whether I'm bothered about this enough to program something like a Raspberry Pi to do the job. If chargers not shutting off completely increases the likelihood of battery fires, it seems rather daft that charger manufacturers don't build such a system into chargers.

 

[Bikes4two]

If chargers not shutting off completely increases the likelihood of battery fires, it seems rather daft that charger manufacturers don't build such a system into chargers.

• It is very difficult to get much data on what is the likelihood of such an incident.
• If the number of incidents does increase and the problem is identified as being down to the charger (rather than the battery, wiring or controller) then that's when you'll see at least from reputable manufactures, them building in timers.

I very much doubt my linking of a few of the recent news stories of the few relatively few ebike lithium-ion battery fires which do get reported and written about (with scant detail ) by online newspaper websites, on this quiet forum, will make any difference to the overall health of the ebike industry.

I'm sure (and hope) you're right but some folk just glance at such headlines without getting into the detail and before you know it they've repeated the headline plus their own twist, and so it goes on.

In another UK bike forum there was a conversation about 'waking up' a sleeping BMS by briefly charging through the discharge post which brought the response


which is clearly not the case. On enquiring further, the poster subsequently revealed that they had charged a 'dead'(as in below 3v on a cell) LiPo battery from one of their RC models (which had crashed incidentally thus possibly compromising the LiPo cells)) using a charger set to NiMh batteries. Now this is a known technique in the RC world for recovering batteries and the poster was prepared for it all going pear-shaped, which it did, but to post the above was alarmist, something which is not unexpected on the Internet but detrimental none the less and should be challenged.

 

[Nealh]

Issues occur when one reads about by passing the BMS and reverse charging and the loon tune on the woke CUK forum who suggests lipo are safer then lion.

 

[guerney]

In another UK bike forum there was a conversation about 'waking up' a sleeping BMS by briefly charging through the discharge post which brought the response

which is clearly not the case. On enquiring further, the poster subsequently revealed that they had charged a 'dead'(as in below 3v on a cell) LiPo battery from one of their RC models (which had crashed incidentally thus possibly compromising the LiPo cells)) using a charger set to NiMh batteries. Now this is a known technique in the RC world for recovering batteries and the poster was prepared for it all going pear-shaped, which it did, but to post the above was alarmist, something which is not unexpected on the Internet but detrimental none the less and should be challenged.

Isn't that a case of someone not providing much detail in the first instance - alarming, possibly because he was alarmed by what happened - and supplying more information later after he'd settled down a bit, had a cup of tea and a nice slice of cake (or biscuits), rather than intending to be deliberately alarmist? I'm surprised there isn't a sticky thread about ebike battery care, because every pedelec has at least one. I recall @Woosh saying:

avoid keeping and charging your high capacity high power batteries inside the house

Woosh - DWGC22 installation thoughts

Well, I've finished the bike and took it for a ride today. I cannot believe I am allowed such a thing. It makes cycling really, really easy and I think it will pay for itself in no time. I can't see any point in keeping my car now. Not turning up at places all sweaty. Installation was really...

www.pedelecs.co.uk

 

[dlwest]

IMO, cell internal resistance is more important than Wh capacity. I use an electronic load to measure voltage drop under 300W instantaneous load. Cells' voltages should stay balanced in that condition - but the battery is to be opened to take these measurements