what capacity cells would be in 36v 17ah battery

[footpump]

don't intend to go the parallel route. but ebc dolphin 13.4 and the 17.4 seem to be similar so might be able to use either on same mounting plate.
still no joy on finding exact call used other than its lg ?
main concern my 13.4 battery about 800 miles use, last time I used it 21 flat miles , 2 bars left out of 8 .
the new battery uses a 3amp charger ,
some adverts state 36v 17ah 512 watts others 529 watts capacity

 

[NJS]

This is a case where information is relevant in one context, but it gets misunderstood and regurgitated into a context where it's not relevant, so your "reliable sources" may or may not be as reliable as you thought, depending on which context they're referring to.

My reliable source is Professor Jeff Dahn. (Around the 1hr10 mark.) He regurgitated nothing and I misunderstood nothing.

Whoever made your bike, decided on a specific charging system to optimise your battery. If there were a way to do it better, they would have provided it.

Effectively, I chose, when I modified my charger.

 

[NJS]

Be careful that cell strings don't get out of balance at 41.5v, every so often you should give a full voltage charge to ensure they are all behaving.

Indeed. A full balance charge every 30 cycles is the number I've seen most often.

 

[Deleted member 4366]

Indeed. A full balance charge every 30 cycles is the number I've seen most often.

That's bullshit. Good luck if you want to follow that advice.

As I already said, what's in that video is a completely different context to your ebike. I've watched that video before. IIRC, he's talking about BMS design. If you want you can strip out your BMS and use a 10-cell ballance charger, then you can charge to whatever voltage you want.

 

[NJS]

That's bullshit. Good luck if you want to follow that advice.

As I already said, what's in that video is a completely different context to your ebike. I've watched that video before. IIRC, he's talking about BMS design. If you want you can strip out your BMS and use a 10-cell ballance charger, then you can charge to whatever voltage you want.

He didn't mention "BMS" anywhere in the entire 1h12 video!

[D8veh] or Professor John Dahn ... (and a few other references.)

I'm not here to argue with you. I did my research and you can "bullshit!" all you want; I've reached my conclusions.

 

[Deleted member 4366]

He didn't mention "BMS" anywhere in the entire 1h12 video!

[D8veh] or Professor John Dahn ... (and a few other references.)

I'm not here to argue with you. I did my research and you can "bullshit!" all you want; I've reached my conclusions.

Good luck then, but please don't advise others to do the same. it just causes confusion.

 

[NJS]

please don't advise others to do the same

I never did. I said "what I do". The only advice I would offer others, is follow the links, read the research and draw their own conclusions.

Mind you, it would be interesting to see the research and/or bonafides that you believe gives you the expertise to be handing out advice on this subject.

 

[danielrlee]

I never did. I said "what I do". The only advice I would offer others, is follow the links, read the research and draw their own conclusions.

Mind you, it would be interesting to see the research and/or bonafides that you believe gives you the expertise to be handing out advice on this subject.

It's tempting to dig your heels in when someone challenges you on an internet forum (d8veh is often blunt and to the point), but he is 100% correct in this instance. You would be better off trying to understand the theory behind his statement, rather than dismissing it outright.

 

[NJS]

he is 100% correct in this instance

And you base that conclusion upon what evidence?

 

[danielrlee]

I base it on my own understanding of the subject. D8 nails the explanation in the first paragraph of post #20.

 

[NJS]

I base it on my own understanding of the subject. D8 nails the explanation in the first paragraph of post #20.

You're "evidence" for contradicting one of the world's foremost Li-ion experts is: your opinion.

Thanks.

 

[Deleted member 4366]

Mind you, it would be interesting to see the research and/or bonafides that you believe gives you the expertise to be handing out advice on this subject.

I don't know if this still works for you since Photobucket borked their forum links. It's three pages of photos of batteries I've repaired/built or otherwise dealt with.

http://s451.photobucket.com/user/d8veh/library/batteries?sort=3&page=1

I have about 100 ebike batteries in my houseat the moment. Some of them built by myself, but most are defective ones that people sent me to analyse. That's not counting all the ones I've repaired and built for other people. I wonder how many BMSs Prof. Whatshisface has had a meter on to find out what's gone wrong with them.

Nobody is disagreeing with the Prof. Nobody is disagreeing that cell voltages need to be kept below 4.2v to prolong their life. What I said is that typical ebike batteries are controlled by a management system that's optimised for charging to 4.2v per cell. The bleed resistors are typically 100 Ohms, so at approximately 4v per cell group, they can balance at 40 miliamps. That would take 25 hours to balance 1 amp-hour. How long do you leave your green light on for your occasional balance charge? How much out of balance is it when you do it? You'd be holding the cells at 4.2v the whole time you want to leave it to do the balancing, which according to your argument is the last thing you'd want to do compared with switching off when you get the green light and letting the bleed resistors immediately reduce the cell voltages to 4.15v, so minimal time at 4.2v.

The whole system is designed to work the balancing a little and often, not to try and do it in one prolonged session

 

[NJS]

I have about 100 ebike batteries in my houseat the moment. Some of them built by myself, but most are defective ones that people sent me to analyse.

Hm. Hope your insurance is up to date. And I hope it is fully-declared, business-class, full-liability fire insurance backed by fire service site inspections and approval by them, the local council, neihbours et. al.

Li-ion fires might be rare; but it sounds like you are really pushing your odds.

That's not counting all the ones I've repaired and built for other people.
I wonder how many BMSs Prof. Whatshisface has had a meter on to find out what's gone wrong with them.

So, your qualifications are that you know how to wield a multimeter; and are apparently jealous of professional expertise.

Nobody is disagreeing with the Prof.

Really, because re-reading your posts in this thread, I think most readers will have reached an entirely different conclusion.

Nobody is disagreeing that cell voltages need to be kept below 4.2v to prolong their life.

Finally. The admission that nothing I've said here is "Bullshit!". That all the references I've cited are correct. Not so hard was it.

What I said is that typical ebike batteries are controlled by a management system that's optimised for charging to 4.2v per cell.

No. That is not what you said. You never dained to mentioned any of that. You just talked down your nose like a petulant teacher's assistant

...

Have you heard of "bottom balancing"? If not, look it up!

 

[danielrlee]

If you spend a while on this forum, it should become apparent that d8veh is one of the worlds most knowledgeable and experienced electric bike builders. Yes, he can be blunt and sometimes even a little rude. He's not always right (we're all still learning 'till the day we die, after all), but he knows of what he speaks on this occasion.

From your latest post #33, I can see that you haven't had a chance to digest what has been said previously.

Cell degradation tends to happen over time. It's not charging to 4.2v per se that damages li-ion cells, but the amount of time that the cells spend at the voltage. Charging to 4.2v just before you use the battery will not be detrimental to the cells.

Undercharging can be of benefit to unprotected cells, or a battery with a BMS that has its full charge voltage set to a lesser value.

The problem comes where you undercharge a battery when its BMS is expecting a higher voltage. What results is that the BMS never gets the opportunity to balance the pack, cell charges become mismatched, pack capacity drops like a stone and eventually the pack will die due to a number of over discharged cells. The alternative scenario is that cells become overcharged due to not being balanced and you end up with a 'thermal event' that can end up in disaster, but you appear to already be aware of this possibility. This is what was meant when d8 mentioned that "balancing will be compromised" and "information taken out of context".

 

[Deleted member 4366]

I wouldn't waste your time Daniel. He's just a waste of space. I don't care what people do themselves, but I worry when they try to mislead other people.

To anybody that reads this, do not do what he says or you'll compromise your battery.

 

[danielrlee]

I wouldn't waste your time Daniel. He's just a waste of space. I don't care what people do themselves, but I worry when they try to mislead other people.

To anybody that reads this, do not do what he says or you'll compromise your battery.

I have always had a short fuse and don't suffer fools gladly, but I'm trying to better myself as I age. I'm pleased it's not possible to view previous post revisions, since I called him a lot worse. After 15 minutes I realised that it made me come across as a bit of a dick and all the cursing helped nobody.

It's the proliferation of misinformation that annoys me too, but in order to counter it, we need to engage in a positive manner, rather than constantly butting heads. I know this all sounds hugely patronising, but it's aimed at nobody in particular and is derived from thoughts about my own being.

NJS, have you had a chance to reconsider the information offered yet?

 

[NJS]

...I don't care what people do themselves,

Then why interfere when I say "what I do"?

but I worry when they try to mislead other people.

That is an out & out lie. I made no attempt to mislead anyone.

I briefly described my practice and gave links to support my reasoning. Full stop.

Any and all misleading, misdirection & subsequent tension in this thread originate firmly and squarely in your court.

 

[NJS]

NJS, have you had a chance to reconsider the information offered yet?

No need to reconsider. I considered it carefully the first time. D8's statements are inapplicable to my pack -- the details of which he has not even attempted to inquire after.

You are adding nothing to the thread or discussion, by blindly assuming a self-described 'expert' knows it all and can do no wrong.

 

[NJS]

No need to reconsider. I considered it carefully the first time. D8's statements are inapplicable to my pack -- the details of which he has not even attempted to inquire after.

You are adding nothing to the thread or discussion, by blindly assuming a self-described 'expert' knows it all and can do no wrong.

(Eva Brown! Discussion ends by Godwin's law.)

 

[danielrlee]

I haven't the foggiest what you are getting your knickers in a twist over, but you clearly have a habit of not reading what is being said.

I've explained in my own words, without the need of assistance from anyone else, why undercharging an 'off the shelf' BMS protected pack is a bad idea. I couldn't care less if you either agree or understand, but I do care that you insist on proliferating the misguided notion that it is recommended practice.