Batteries Charging Routine

Yes... lets open this Pandora's box for a while.

What is the most optimal charging routine? I have seen so many opposing opinions on this one...

So...

1. To charge switch battery off, plug charger to electric socket and switch it on. Connect charger to battery.

2. Charge battery to some decent level, but not to 100% as this would reduce battery life? Lets say 90%?

3. From time to time charge battery to 100% and let it charge little longer to balance cells. How much longer? 1h?

1. To charge switch battery off, plug charger to electric socket and switch it on. Connect charger to battery.

I can see why some support this view; Switching the charger on pre-charges the internal output capacitors preventing sparks/damaging the charging socket/pin contacts. Saying that, one of my own bikes/chargers uses a relay in circuit which prevents that anyway. So it's bike/charger dependant.

2. Charge battery to some decent level, but not to 100% as this would reduce battery life? Lets say 90%?

Some do say. But if you do that, the battery doesn't balance properly since balancing happens only when the battery is fully charged (near to) to 100%. Has anybody proved this theory? Personally I don't see the point; just don't leave a fully charged/balanced battery sitting that way for ages before using it to avoid over-stressing the cells.

3. From time to time charge battery to 100% and let it charge little longer to balance cells. How much longer? 1h?

IMO the only sure way to know is to use a wattmeter. On one of my bikes, when the charger LED turns green it's still drawing/providing 18 watts of charge. How long it actually takes before consumption drops to below 2 watts depends upon how out of balance the cell strings are.

My suggestion would be to follow your own bike makers recommendation. At least if faults occur during warranty you've followed your manufacturers best advice.

Interesting to note on the 'leave it an extra hour? on ful charge' that on exposure lights, you charge it to full 100%, then are expected to leave it to continue 'charging' for a bit longer - This is the company instructions rather than what someone told me on FB/Twatter/Here.

So there must be some merit in leaving it for longer past its 100% mark.

Personally I've been charging when its a bit less than 1/2 used, charging to 100%.

It should also be noted that for power tool batteries, you charge to 100% and I've never seen instruction to do other like charge to 90% or whatever - These are pro kit batteries.

3. From time to time charge battery to 100% and let it charge little longer to balance cells. How much longer? 1h?

only if you need rebalancing. The symptom is your battery cuts out before it's completely empty.

On older BMS, the design wasn't too clever and the current to keep the BMS awake is much higher than now. This causes the battery to be out of balance once every few months. When the battery reaches about 95% full (41V), the BMS enters balancing mode. You may see the LED on the charger flashes red / green for a few minutes before it goes solid green.

Nowadays, BMSes are better, the standby current is in micro-amps instead of milliamps, you may never need to do that.

Yes... lets open this Pandora's box for a while.

 

What is the most optimal charging routine? I have seen so many opposing opinions on this one...

 

So...

1. To charge switch battery off, plug charger to electric socket and switch it on. Connect charger to battery.

 

2. Charge battery to some decent level, but not to 100% as this would reduce battery life? Lets say 90%?

 

3. From time to time charge battery to 100% and let it charge little longer to balance cells. How much longer? 1h?

1. The risk is that when you connect the charger to a live charge port, you get a big spark as the battery charges the capacitors in the charger. The spark can weld the jack in the socket and destroy it when you try to pull it out. If it doesn't weld, it will erode the socket until it eventually can't make a connection. If the capacitors are already charged by switching on the charger, that can't happen. If you have a power switch on the battery that isolates the charge socket, likewise, you can't get that problem as long as it's switched off. Some advanced more expensive chargers might have diodes to prevent reverse charging.

2&3. You can charge your battery to whatever level you want occasionally, but balancing only happens at the top of the charge. It works on the principle of a little and often, since the balancing charge is only about 60 -100 mA. You can do an occasional charge to maximum for a long time and the rest 80% charges, but all you achieve is to reduce your useable battery capacity by 20% because when you do the long maximum charge, you hold the battery at the maximum voltage for a long time, which is not good for it and undoes any saving you made on the previous charges. Without balancing, there is a danger that one cell could drain below 2.5v and brick your battery.

Whenever your battery needs charging, switch on the charger, plug it and wait for the green light. When you get the green light, unplug it and switch it off. It's pretty simple really. I don't understand why you guys want to try to make it more complicated.

I listened to a lithium Ion talk on a podcast. Cut to the end.

Do what you want regarding charging.

No two batteries are the same and why some last longer than others is a mystery.

The charger and circuits will protect battery.

I can back this up.

I bought 2 phones 6 years ago.

One got that it would not last long and became unusable 2 years ago, while the other is still working fine . Both left on charge all night.

There is evidence that charging little and often exstends battery life for some. I just plug mine in every 2 days until red light turns green.

Just use it until it dies. Seems no matter what you do it won't make much difference if you have a battery that decides it's not going to last.

I do think some cells will fail causing a drain 24/7 but nothing you can do to prevent that If your unlucky..

I plan to make my battery work over next 3 years , and when it needs charging every day I'll think about buying another

No two batteries are the same and why some last longer than others is a mystery.

I suspect its not a mystery to those using Lithium batteries for electric car batteries.

So there is a question, electric car batteries are seemingly designed for a long service life and may well be charged often.

So what voltage do electric car batteries charge too and are there other battery management stuff they do to improve service life ?

So what voltage do electric car batteries charge too and are there other battery management stuff they do to improve service life ?

The only thing that matters with e-car batteries is speed of charge. For example my third series Nissan Leaf has three options for charging it's 40kWh battery:

Rapid from a public charger at up to 50kW rate. Charges an empty battery to 80% in 40 minutes The more this is done, the shorter the battery life. Beyond 40 minutes the charge continues but the rate automatically drops rapidly as the battery fills. For example, 22 kW rate at 85% full, 7 kW at 92% full, so taking for ever to completely fill.

Fast from a Home charger installation at 6.6kW rate, taking 8 hours for a completely empty battery to full. Typically overnight, this is considered the normal way to charge and the batteries are lasting 12 years to date with this sort of charging.

Slow from a 13 amp socket at up to 9kW rate using the dedicated slow charger connector. This takes 20.5 hours to fill a completely empty battery. This amounts to trickle charging and gives the battery a very easy stress free life.

The personal way I've used these in my almost 5.5 years with the car:

Charge when content down to between 30% and 40%, avoiding emptying the battery more if avoidable

Rapid only when I absolutely have to.

Fast alternating with Slow roughly every other charge most of the time. Being down to 38% earlier today, it's actually on the Slow charger at the moment, the last charge being Fast.

Slow when ambient temperature is at or below 10 degrees C to protect the battery.

End result at present is little loss of range and capacity at 5.5 years. On the run in warmer months down from 168 miles to about 155 miles, so about 8%.

When used only in local stop-start heavy traffic, range is academic since always ending up back at home, but the rate of discharge in both mileage and battery content percentage indicates 140 to 145 miles.

So I'm very happy with it at 87, knowing the battery will easily outlive me. It will still have at least 70% range when I'm 94 and the car 13.5 years old, and even at 100 it will still get me to and from the supermarket etc a number of times between charges.

But of course even if still alive I won't necessarily still be driving, since I'll stop as soon as my faculties show any sign of not coping. Already, although my daytime eyesight is excellent at 6/6 metric (old 20/20 imperial), it's not good enough after dark so I never drive at night now.

For information:

"Pupils shrink and don't dilate as much in the the dark as we age, reducing the amount of light entering the eye. The retina of an 80-year-old receives far less light than the retina of a 20-year-old, making older drivers function as though they are wearing sunglasses at night. An older person may exhibit normal visual acuity in an eye exam but still struggle to focus on the road at night, where lighting is poor and more complex visual tasks are required.

Ironically, high beams, auxiliary lights and fog lights designed to help you see better at night can put you at risk for an accident due to the glare you may experience when oncoming vehicles have these features."

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Edited July 17, 20232 yr by flecc

Electric cars and e-bikes both use 18650 cell batteries. So does my power tools.

Not so with all e-cars. The forerunner Nissan Leaf for example has only ever used flat prismatic cells for it's over 12 years on the market, and these sort of cells are what's used in battery electric buses. The Mitsubishi MiEV uses Le50 cells made by Yuasa, and some models latterly use Toshiba's SCiB Lithium Titanate battery cells.

The trouble with most 18650s, 21700s and the like is they are often too high density for long life, so that's why ebike batteries rarely last over 5 years, often far less. In e-cars, buses etc., weight and bulk aren't so important, so lower density cells are used for longer life, over ten years now being considered normal.

And of course e-cars and other large e-vehicles have far more sophisticated chargers, helping to extend battery life.

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Edited July 17, 20232 yr by flecc

I suspect its not a mystery to those using Lithium batteries for electric car batteries.

 

So there is a question, electric car batteries are seemingly designed for a long service life and may well be charged often.

 

So what voltage do electric car batteries charge too and are there other battery management stuff they do to improve service life ?

Samsung do cells for Tesla powerwalls that are specifically designed for long service life (+2000 cycles @4.1v) e.g. 21700-33j. They are cheap but require either soldering of tabs or laser welding. But again, there is a tradeoff of weight versus performance/capacity versus cycle life.

https://eu.nkon.nl/rechargeable/li-ion/21700-20700-size/samsung-inr21700-33j-3270mah-3-2a-z-tag.html

Edited July 17, 20232 yr by Sturmey

Samsung do cells for Tesla powerwalls that are specifically designed for long service life (+2000 cycles @4.1v)

So these batteries quote a +2000 cycle life when charged to 4.1V. Do they give a cycle life when charged to 4.2V ?

So these batteries quote a +2000 cycle life when charged to 4.1V. Do they give a cycle life when charged to 4.2V ?

Data sheet attached below. Not tested at 4.2 volts as far as I can see. I did read some speculation somewhere that the normal 500 cycles would be expected at 4.2 volts. I just use a 42v charger with older style power rectifier/diode in series that reduces the voltage by a little over 1 volt.

SAMSUNG-INR-21700-33J-Datasheet.pdf

So there is a question, electric car batteries are seemingly designed for a long service life and may well be charged often.

 

So what voltage do electric car batteries charge too and are there other battery management stuff they do to improve service life ?

Active balancing. Temperature control. Cooling. Lower current per cell.

I did read some speculation somewhere that the normal 500 cycles would be expected at 4.2 volts. I just use a 42v charger with older style power rectifier/diode in series that reduces the voltage by a little over 1 volt.

I can see why battery manufacturers would choose a 4.2V cutoff, batteries may not last so long so you need to buy more of them.

Are there BMSs out there that give you the choice, i.e. that would allow you to set the full charge point to say 4.1v per cell and have them balance at that voltage ?

Are there BMSs out there that give you the choice, i.e. that would allow you to set the full charge point to say 4.1v per cell and have them balance at that voltage ?

I asked that question a little while ago:

https://www.pedelecs.co.uk/forum/threads/bbs02-battery-charger.45379/page-3#post-682271

[mention=3847]saneagle[/mention] linked this Smart BMS:

https://www.aliexpress.com/item/1005005320665154.html

Edited July 18, 20232 yr by guerney

I can see why battery manufacturers would choose a 4.2V cutoff, batteries may not last so long so you need to buy more of them.

 

Are there BMSs out there that give you the choice, i.e. that would allow you to set the full charge point to say 4.1v per cell and have them balance at that voltage ?

Nearly every one of us on this forum, who builds our own batteries, the sensible ones at least, charge them to 4.2v per cell. Do you think we're trying to buy them more often too?

If one want's to experiment and use a lower charge voltage then say so with warnings to those unannitiated as it can lead to can of worms. One if using a non smart BMS will need to be able to manually balance if needed and recognise when an unbalance is occurring.

For protection and using a lower balance/charge voltage use a uart/BT smart BMS where the parameters can be adjusted and balance can be accessed via a smart phone or PC.

The only real reason to want to only charge to 4v or 4.1v is for a special project or a scientific project to see how long one can actaully make the battery last.

Other wise for most of us just charge and use to the typical battery specs of 4.2v, I only charge to 4.2v a few hours (12 -24 ) before I need the battery otherwise I charge to 60 -70% and then just top up the final charge.

Edited July 18, 20232 yr by Nealh

I can see why battery manufacturers would choose a 4.2V cutoff, batteries may not last so long so you need to buy more of them.

Dont forget that there are good reasons for using the full voltage range for cells. Restricting the voltage range to multiply the battery life can considerably reduce the actual available battery capacity and range of the battery. For example, when endless sphere tested the Samsung 50E at 4.1 volt and higher lvc, they measured the capacity at them voltages and it was reduced down from 4.954 to 2.878 Ah.

So it it appears that if you want to built a battery to the 'Tesla' spec (2000 cycles), you will need about 50% more cells which means about 50% more weight and cost.

This appears to be the case, whether you compare Samsung 50E to Samsung 33j long life or whether you compare cells used at full voltage range (4.2 )or reduced voltage range (4.1 & higher lvc ) depending on actual cell used.

Edited July 18, 20232 yr by Sturmey

Charging to a storage charge of 60/70% then charging to full 100% will still give good life service if the battery is cared for and used regularly , 8 years shouldn't be an issue if top quality cells are used.

A lot of the issues we do see with batteries are due to lack of use or care when not used for many months or even years, the lack of care is simply due to the facts that most users have little or no idea about lithium cells and simply think fully charged it will be ok.

My two 14.5ah /522wh batteries that originally came from Woosh are now 8 years old , though no longer used for ebikes as I don't use 36v any more, they are used for other uses where I need DC power.

The guys on ES are experimenters and love all these facts and figures which gives the likes of us ammunition to use to decide what to use.

If you read the threads they build larger batteries then most so often we see 100+ cell packs being used and often more then 60v, so some of them have vested interest in charging to lower voltage to try an extend the pack life.

Unless one is very knowledgeable then 4.2v is best.

Downsides as mentioned are less capacity which also means less range, unless you have a big battery to counter the range. For most folks 50/60 miles is more then enough range, if you need more for along ride or touring just carry spare batteries .

For my 100 milers I carried approx. 1500wh but would return home with 40% total, extra wh just means one can use higer asssit and not have to be concerned about range anxiety.

Dont forget that there are good reasons for using the full voltage range for cells. Restricting the voltage range to multiply the battery life can considerably reduce the actual available battery capacity and range of the battery. For example, when endless sphere tested the Samsung 50E at 4.1 volt and higher lvc, they measured the capacity at them voltages and it was reduced down from 4.954 to 2.878 Ah.

So it it appears that if you want to built a battery to the 'Tesla' spec (2000 cycles), you will need about 50% more cells which means about 50% more weight and cost.

This appears to be the case, whether you compare Samsung 50E to Samsung 33j long life or whether you compare cells used at full voltage range (4.2 )or reduced voltage range (4.1 & higher lvc ) depending on actual cell used.

 

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So it it appears that if you want to built a battery to the 'Tesla' spec (2000 cycles), you will need about 50% more cells which means about 50% more weight and cost.

Very interesting. Personally, because I have an ebike, I really wouldn't mind a 50% bigger battery.

Very interesting. Personally, because I have an ebike, I really wouldn't mind a 50% bigger battery.

Good point.

I have a 36V 10Ahr that weighs 2.6Kg.

So if the battery 'life' would increase by 400% for a measly extra 1.3Kg, then I suspect a lot of people would go for it.

But I can understand why eBike battery manufacturers would not be so keen to follow that development route.

Good point.

 

I have a 36V 10Ahr that weighs 2.6Kg.

 

So if the battery 'life' would increase by 400% for a measly extra 1.3Kg, then I suspect a lot of people would go for it.

 

But I can understand why eBike battery manufacturers would not be so keen to follow that development route.

The original Raleigh all steel Bikes were considered a bike for life. They came with chainguards, 40 spoke rear wheel, long mudguards, steel frame, leather saddle and they did last a lifetime. But I am not sure if people and perhaps sellers are really interested in long life stuff any more. They are probably more interested in the lighter weight and performance of modern bikes. Many bikes seem to spend most of there time in sheds and rarely used.

I have bought many bikes secondhand for 20 euro or less and many were on their original chains and tyres, which shows that there was little usage.

But I personally do high mileage and hence my interest in hub motors and long life batteries. You may see a turn back in the future towards more practical and utility type bikes. Who knows.

So coming back specifically to batteries, there are reasons why long life cells may not be worth the extra weight and cost. For example, many batteries fail early because of mechanical damage or drenched by rain or stolen or the bike/battery being stored away for a long time with exhausted battery. Also. many people only use their bike once or twice a week so hence a standard 500 cycle battery is sufficient.

But there are people who use their bike daily and they would possibly benefit from a bettery quality battery with long life cells.

Edited July 19, 20232 yr by Sturmey

But there are people who use their bike daily and they would possibly benefit from a bettery quality battery with long life cells.

Indeed.

And it would be nice for battery manufacturers to provide consumers with a choice.