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Couple of amateur questions re:batteries


Paddylaz
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Embarassingly noob questions I know. But.......

This idea of 'bad cell(s)' in your battery. How would you know? Would it for instance come up in my Inmotion app's diagnostic test? Can cells randomly 'go' bad or would there have to be some sort of initiator (old age, damage, penetration etc)

Also.......how long do chargers 'last' before they start not properly charging the battery? I only ask because my phone charger 'charges' my phone to 100 - but there is something wrong with it as the two Samsung phones I use drain too quickly on it, making me question the charger rather than batteries.

Cheers guys. Just a cocktail of curiosity & paranoia on my part!

PS. USA wheelers, enjoy the eclipse!

Edited by Paddylaz
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23 hours ago, Paddylaz said:

Embarassingly noob questions I know. But.......

This idea of 'bad cell(s)' in your battery. How would you know? Would it for instance come up in my Inmotion app's diagnostic test? Can cells randomly 'go' bad or would there have to be some sort of initiator (old age, damage, penetration etc)

Maybe they could - but normally they should have a reason. Imho mostly age?

you should notice it on decreased range.

for more details you can read through batteryuniversity.com...

23 hours ago, Paddylaz said:

Also.......how long do chargers 'last' before they start not properly charging the battery? I only ask because my phone charger 'charges' my phone to 100 - but there is something wrong with it as the two Samsung phones I use drain too quickly on it, making me question the charger rather than batteries.

A first quick test for the charger should be to measure the no load voltage?

for phones it could be different with the "smart capacity meters"? Or just too many (new) apps draining the battery?

 

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23 hours ago, Paddylaz said:

This idea of 'bad cell(s)' in your battery. How would you know?

If you charge your wheel to 100% and let it sit for some hours and the charge has dropped a bit, that might indicate a bad cell. Or if you don't reach full charge at all...

23 hours ago, Paddylaz said:

Also.......how long do chargers 'last' before they start not properly charging the battery?

They charge or they don't. They typically don't charge improperly. If the app shows a full charge, you got a full charge, no smart meter involved that could fuck up.

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23 hours ago, Paddylaz said:

This idea of 'bad cell(s)' in your battery. How would you know? Would it for instance come up in my Inmotion app's diagnostic test? Can cells randomly 'go' bad or would there have to be some sort of initiator (old age, damage, penetration etc)

Also.......how long do chargers 'last' before they start not properly charging the battery? I only ask because my phone charger 'charges' my phone to 100 - but there is something wrong with it as the two Samsung phones I use drain too quickly on it, making me question the charger rather than batteries.

Paddy, I can only talk from experience of LiPo batteries going bad, but everything I've seen and read about 18650 suggests that failures should be similar, albeit they should last a hell of a lot longer not only because LiPos are way more fragile but also in model aircraft they get really badly treated - 1C or higher charges and 20C plus discharges, most of my flight batteries last 6 to 10 minutes in flight, I.e. averaging a 10C discharge, an EUC should have at least 1 hours run time so an average of 1C or less.

Firstly, I fly using 2 to 6 cell LiPo's which should have been fairly closely matched at manufacture yet it is very rare for more than one cell to go bad in a pack so there is a definite randomness to it. Ignoring physical signs (a cell puffing up) the often noticeable change is significantly increased internal resistance, I.e. Under load the pack will drop its voltage more and the maximum current will be reduced. Our chargers show every cell's voltage and a failing cell will often be lower when it's been used but sometimes reaches full voltage quicker (I.e. It's capacity has gone down) Sometimes, leaving the pack for some days, that cell may have dropped to a lower voltage, I.e. It is leaking charge - which I think is that Lithium metal whiskers starting to partially short the cell.

The problems you have with an 18650 battery pack in an EUC is that there are a) cells in parallel and b). not usually any monitoring of the individual cells by the BMS that reaches the main control board so, it is highly likely you will only see range reducing and a greater voltage drop under high load (high acceleration or a hill). It would probably be easier to spot if you commute on the wheel so start to see changes day to day - but a colder day will also show the same effects.

Using a charge doctor might show you that the current is reducing more slowly or indeed stops reducing and settles at a low level. As @Slaughthammer has just said above it might slowly discharge lowering the pack voltage after a few days

Chargers, like any electronics, could last for generations or fail tomorrow, there is no effect other than plugs wearing out that could be seen as ageing although electrolytic capacitors ( the big cylindrical ones) can potentially dry out with age but it's fairly unusual- I'm still using a Sony CD player I bought in 1986 and the Casio calculator I had at school (which, OK, replaced a slide rule) still worked when I put a battery in it last year. As @Chriullhas already said above, if it is reaching full voltage off load it is probably OK, with a Charge Doctor you can also confirm it reaches full current as well.

Edited by Keith
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