Help us build a better Ebike battery

[Woosh]

Basicasic brings up some research, which would mislead forum members to use their batteries correctly.

I read the same posts from Basicasic like everyone else, I did not find his posts misleading in the slightest.
Like in most situations, the devil is in the details.
How, for example, do you know you are charging your battery to 80% of its full capacity? For me, it's easy, that is to charge it up to 40V instead of 42V, that involves opening up your charger and find the adjustable that controls the output voltage and change it, but I would not do so though, because doing so will make the cell balancing impossible. What is worse? having unbalanced cells that leads to failure or having only 800 charging cycles? If I were in need of more charging cycles, I would use Lithium Iron Phosphate instead of Lithium Manganese Nickel Colbalt batteries.
In a forum like this one, we all benefit from a diversity of points of view.
I would rather have more views than just the repeated orthodox ones, even if at the end of the day, the orthodox ones are those you should follow.

 

[Deleted member 4366]

I read the same posts from Basicasic like everyone else, I did not find his posts misleading in the slightest.

How many people come on the forum and asks the question, "I've heard that I can get longer battery life if I only charge my battery to 80%? Where can I get an 80% charger?" For every one of them, there's probably 10 more that figure out a way to charge to 80% on their own. Is that what you'd want people to do with your batteries?

 

[basicasic]

You don't need to defend me, guys. The situation is much more simple than that. I'll explain: Basicasic brings up some research, which would mislead forum members to use their batteries correctly. He's put straight on it, so gets a chip on his shoulder, which he probably already had because he completely misread and misinterpreted what I wrote. He then tries to get revenge by making personal attacks in another thread. We just have to bide our time with these wakers until they find other forums to troll.

This is so very sad to see.

The research article I quoted is in fact quite correct and all you are doing is making yourself look silly. I specifically challenged you in that thread:

' you show me the Battery University article is incorrect and I'll willingly change my opinion'

You couldn't and haven't. In fact you replied: 'I didn't say it's incorrect'

Furthermore I recommend everyone read this article with regard to the subject of extending battery life taken from a lecture given by Professor Jeff Dahn from the Dahlhousie University, Canada (who's research dept works with 3M and Tesla) and judge for yourselves exactly who is misleading who. The video is well worth a watch for those with a technical interest as well. You can skip all the tech stuff and go straight to the end of the article and read the recommendations if you wish:

https://www.electricbike.com/how-to-make-lithium-battery-last/

Now no doubt our forum 'expert' knows better than Professor Dahn but to sum up the conclusions of this article. To maximise the life of your lithium battery you should:

1. Keep it cool
2. Store it when not in use at 3.5V in a cool place
3. Never charge it to 100%. and only to 80% (or 90% just before you use it)
4. Charge your battery slowly (reduces heat)

All of the above are exactly the same conclusions drawn by the article I quoted in the other thread which our 'expert' dismissed as misleading and 'old technology'

Forum members can judge for themselves exactly who is misleading them.

 

[Deleted member 4366]

I think d8veh is just trying to obtain clarity on the voltage limit.

That's partly it. Like many others, I'd love to know of a test house that would approve a bike with a 48v battery to EN 15194. Look around. How many OEM ebikes are there in Europe with 48v batteries and an EN 15194 certificate? I don't know of any! There must be a reason for that. Either the market doesn't want 48v or they're not allowed. Either way, OP would be wasting his time making 48v batteries for the European market unless he knows of imminent changes. This was what was on my mind.

I'd still like a definitive statement that he has checked with X (named) test house, and they have given him in writing that they would approve a bike with a 48v system to EN 15194. That would clarify one point at least. An eternal sceptic I might be. Call me what you like. I'm not convinced that this has been bottomed out yet.

 

[basicasic]

I would also add to my post above.
To achieve these things in the real world you can do simple things such as:

1. Keep your bike or battery in a cool place
2. Run it down to 2 bars out of 5 before you store it
3. Only charge it up to 4 bars out of 5 if possible. If you need the range charge it to 100% just before you make your journey. Fully charge it every now and then, but use it as soon as possible after.
4. Unfortunately you are stuck with the charger you've got but slow charging is better

These simple things according to Professor Dahn can increase the life of your battery by 2 to 3 times.

 

[Deleted member 4366]

This is so very sad to see.

The research article I quoted is in fact quite correct and all you are doing is making yourself look silly. I specifically challenged you in that thread:

You're making yourself look silly. Read again. I never said that anything in the article was incorrect. I agree with every point in it as being relevant at the time it was written or updated.

 

[basicasic]

I'd still like a definitive statement that he has checked with X (named) test house, and they have given him in writing that they would approve a bike with a 48v system to EN 1519.

Try asking him nicely.

 

[Deleted member 4366]

I'll say it one more time.

• Balancing only happens at the top of the charge - say above 95%.
• It happens very slowly, and works on the basis of a little and often.
• Going to 100% only occasionally won't provide sufficient time to balance. If you left your charger connected on green for a long time to compensate, it would hold your battery at an even higher voltage, which would be worse for it.
• The management system on all the common e-bike batteries is designed to work properly when you regularly charge until you get the green light. Doing anything else without understanding the consequences and implications would most likely do more harm than good.

 

[Woosh]

Is that what you'd want people to do with your batteries?

No, I don't give out that advice.
Nor do I tell people how to reduce the shunt resitors' value.

 

[Benjahmin]

2. Store it when not in use at 3.5V in a cool place

This is for a cell, not a battery. A battery is made up of a number of cells. So a cell will last longer if charged to 80%, correct. But, E bike chargers do not charge individual cells, they charge the battery. Only if charged until green light will the bms balance cells. Lvc will operate when any one cell reaches this limit. Ergo, whilst it may be better for a cell to be charged to 80%, the battery needs a full charge to give maximum Wh.
That's my understanding and attempt at clarity on this.

 

[topographer]

I would also add to my post above.
To achieve these things in the real world you can do simple things such as:

1. Keep your bike or battery in a cool place
2. Run it down to 2 bars out of 5 before you store it
3. Only charge it up to 4 bars out of 5 if possible. If you need the range charge it to 100% just before you make your journey. Fully charge it every now and then, but use it as soon as possible after.
4. Unfortunately you are stuck with the charger you've got but slow charging is better

These simple things according to Professor Dahn can increase the life of your battery by 2 to 3 times.

Which 'real world' are you talking about? The one where you ring a taxi to take you home once your bike's down to two bars? Or the one where you spend nine hours before each ride cross-referencing an Ordnance Survey Pathfinder map and a blackboard full of equations to work out what circular journey will have you arriving back home just as you get down to two bars? I suppose you could get down to two bars, then bag the battery and use muscle alone to get home but I don't fancy it.

 

[basicasic]

Which 'real world' are you talking about? The one where you ring a taxi to take you home once your bike's down to two bars? Or the one where you spend nine hours before each ride cross-referencing an Ordnance Survey Pathfinder map and a blackboard full of equations to work out what circular journey will have you arriving back home just as you get down to two bars? I suppose you could get down to two bars, then bag the battery and use muscle alone to get home but I don't fancy it.

I think you misunderstood. Point 2 refers to storage of your battery over a period of time when you aren't using it, say winter. So you would run it down to roughly 2 bars and then store it

These aren't my recommendations. I'm just passing on the advice given by Professor Jeff Dahn from the Dalhousie University in Nova Scotia, Canada who has done a lot of research with partners Tesla and GM about car battery longevity.

The article is here:

https://www.electricbike.com/how-to-make-lithium-battery-last/

You can skip over the technical stuff and go to the conclusions at the end if necessary. It contains a video of his lecture as well but it is a bit long though worth watching if you have time.

 

[basicasic]

This is for a cell, not a battery. A battery is made up of a number of cells. So a cell will last longer if charged to 80%, correct. But, E bike chargers do not charge individual cells, they charge the battery. Only if charged until green light will the bms balance cells. Lvc will operate when any one cell reaches this limit. Ergo, whilst it may be better for a cell to be charged to 80%, the battery needs a full charge to give maximum Wh.
That's my understanding and attempt at clarity on this.

I agree it's impractical for many people not to charge fully to 100% because they may need all the range they can get, and they may charge up overnight and not fancy getting up at 4am to check whether it's at 80% or not. To me the sensible thing to do would be to charge your battery up fully the night before you use it, use it and keep it in between rides below it's maximum charge.

I understand the difference between cells and batteries and the fact that the BMS balances the individual cells in a battery during charging. I'm interested by the fact that Tesla Motors only charge their batteries (which contain thousands of cells) to 80% to maximise their longevity (for the 8 year warranty) and yet the BMS must be balancing them somehow. Maybe their system is far more advanced than the average bike battery ones.

Anyway the article that I have been referring to that made these recommendations is here:

https://www.electricbike.com/how-to-make-lithium-battery-last/

The author is professor Jeff Dahn from the Dalhousie University in Nova Scotia, Canada and it's well worth reading. The video is well worth watching too.

 

[topographer]

I think you misunderstood

Yes, I misunderstood completely.

 

[soundwave]

each tesla bank of cells has its own cpu built in to them and there also cooled as well

the bms we use for bikes are just shite tbh compared to that

 

[Nealh]

ebike bms balance at end of charge which is generally 4.15 - 4.2v. My LG system BMS and charger stop and balance at 4.15v max.
Tesla only have to configure the balance voltage to a lower setting such as 4.1v otherwise AKA a smart bms.
You can get them on BMS Battery for about $40/50 but you need a programmer lead $199 .

 

[Deleted member 4366]

I ordered one of these a couple of months ago. Delivery was quoted as end of June, so it might come any day:

https://www.speedict.com/

 

[soundwave]

 

[lnunell]

Hi All,

A progress report on the battery systems including the BMS and the Charger. We have a prototype system running with all of the metrics in the green, It is currently in a much larger box to test thermals but the system is running comfortably at 600watts output, the initial aim is to have these units running in parallel so we can match demand with different size battery packs.

The 600 W version will charge a 150Wh pack in 15 minutes to full (10 minutes to 80%). But we can combine two of these chargers in parallel to get 1200 watts for a 15 minute charge on 300Wh (10 minutes to 80%)

We have designed our architecture to be infinitely expandable so we will be able to charge as many bike (or as large a pack as possible)

Our current test results are really promising:

600W output
30 degree Celsius temp rise (well withing boundaries)
90% efficiency at 57.6v
Power Factor of 1.
Number of components used 40% less than Half Bridge systems
0 Electrolytic capacitors used (longer life)

We are now switching our BMS and control systems over to fully digital to reduce size, cost and increase control over the analysis of the battery health. We think we will have our system on several bikes before the end of May and validated before end of august.

Thanks,

Leigh.

 

[gwing]

I don't think the market needs fast charging. Schwinn tried that with their lithium titanate batteries. They struggled to sell their bikes. In the end, they had to reduce the price of their bikes by 50%. Those batteries could be charged in 5 minutes and have a nearly infinite life. I have a couple if anybody wants to come and get them.

Instead, you should concentrate on specific energy. People want light-weight batteries with around 500 Wh.

Say rather that, at current technology levels, 500 Wh batteries are at a popular sweet spot for range/weight/cost. As battery capacities increase we'll soon be expecting 600, then 700 Wh at the same sort of price and weight as we have now. I think there will probably be less demand for smaller, lighter, cheaper batteries at 500 Wh capacity but who knows?