what capacity cells would be in 36v 17ah battery

[NJS]

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.

I didn't need your paraphrasing to understand D8s meaning; but one phrase sums up that meaning (original & paraphrased): Not applicable!

Have you heard of non-balancing BMS boards? Ie. Protection (UV/OV/OCD/SCD) only!

 

[danielrlee]

Have you heard of non-balancing BMS boards? Ie. Protection (UV/OV/OCD/SCD) only!

I have. They give less protection than balancing BMS boards. What's your point?

I can fit my little finger in a household mains socket - doesn't make it a good idea though.

 

[NJS]

I have. They give less protection than balancing BMS boards.

Hm. Since most cheap (typical E-bike pack) BMSs don't do dynamic balancing, they are effectively Protection only boards except when charging; thus provide no extra protection whilst you're riding.

What's your point?

My point is that as I am using a protection only BMS on my pack, none of D8s "No. You don't want to do it like that, You should do it like this. You MUST charge to 42 volts because I said so, and if you don't the sky will fall and the world will end" edicts, apply.

I take care of balancing through a different mechanism, that allows bottom balancing, and protects my cells, by not forcing the entire pack to sit at or close to 100% capacity voltage for the entire duration of myriad charge/shunt/charge/shunt cycles, which is authoritatively recognised as being once of the primary reasons for shortened lifespans in Li-Ion batteries. Second only to heat.

Balance the pack at a lower voltage and only bring up to 95% SOC immediately before riding, and an entire class of cell damage -- extended periods at maximum voltage -- is precluded.

(There's more to it than that, but I don't want to be accused of encouraging anyone to adopt my methods, so I'll leave it there.)

I can fit my little finger in a household mains socket - doesn't make it a good idea though.

You were doing so well. You did at least inquire. Just a shame you had to resort to puerile sarcasm before waiting for the answer.

 

[danielrlee]

Can't. Be. Bothered.

 

[NJS]

Can't. Be. Bothered.

Paraphraseut of your depth.

 

[danielrlee]

Paraphraseut of your depth.

No. I can't be bothered to explain why 'bottom balancing' is bad practice and why you are always only one degraded cell away from a catastrophic event.

 

[Deleted member 4366]

Paraphraseut of your depth.

OK, we let you win. Now go and troll somewhere else. Try the My Little Pony forum. That's full of fantasy, so you should fit in well there.

https://mlpforums.com/

 

[NJS]

No. I can't be bothered to explain why 'bottom balancing' is bad practice and why you are always only one degraded cell away from a catastrophic event.

I didn't ask you to tell me why you think its bad. Once again, your opinion versus proven methodology.

I was simply explaining why nothing D8 or you was relevant to what I'm doing.

 

[NJS]

OK, we let you win. Now go and troll somewhere else.

You are the troll. I made a passing comment; and you got rude, aggressive and defensive; and now resort to taunts when you know any technical argument you might offer will be torn to sheds.

The only petulant child here is you; which I guess is why you knew where to link for your insult.

Logic is obviously beyond your calling.

 

[danielrlee]

I didn't ask you to tell me why you think its bad. Once again, your opinion versus proven methodology.

I was simply explaining why nothing D8 or you was relevant to what I'm doing.

Oh, do stop flirting. Please tell, out of the two of us, who do you really prefer?

 

[NJS]

Oh, do stop flirting. Please tell, out of the two of us, who do you really prefer?

Oh Definitely D8. He's so butch. You're just a little too camp for me.

 

[danielrlee]

Oh Definitely D8. He's so butch. You're just a little too camp for me.

Can't interest you with a 'Netflix 'n chill' then?

I bet it's been your plan all along to familiarize yourself with d8veh's probe. Go on then. It'll all end in tears I tell you. He's only interested in your batteries.

 

[NJS]

Can't interest you with a 'Netflix 'n chill' then?

I bet it's been your plan all along to familiarize yourself with d8veh's probe. Go on then. It'll all end in tears I tell you. He's only interested in your batteries.

Sorry man. Didn't realise I was stepping on your toes there.

 

[danielrlee]

Sorry man. Didn't realise I was stepping on your toes there.

I'd say you're certainly looking to "bend over and touch 'em" with one of us and we all know you like the butch ones. Who's on top tonight then?

 

[Steb]

I'd say you're certainly looking to "bend over and touch 'em" with one of us and we all know you like the butch ones. Who's on top tonight then?

Sorry to but(t) in (dreadful pun), but when you lot aren't having a go at each other you seem to know exponentially more than I do about batteries (though I'm quite adept at hijacking threads). So, at risk of causing more flaming, what battery would you put on a torque sensor Ed crank drive (tsdz2) that's nominally 500w but in reality up to 700 (i.e. at 36v about 18 amp)? In other words what do you thinks the best 36v 18a bottle battery out there? Many thanks

 

[Steb]

Sorry to but(t) in (dreadful pun), but when you lot aren't having a go at each other you seem to know exponentially more than I do about batteries (though I'm quite adept at hijacking threads). So, at risk of causing more flaming, what battery would you put on a torque sensor Ed crank drive (tsdz2) that's nominally 500w but in reality up to 700 (i.e. at 36v about 18 amp)? In other words what do you thinks the best 36v 18a bottle battery out there? Many thanks

And why does tesla get 8 years and unlimited miles out of battery packs regularly cranking out 5C (several hundred kW) when pedelec batteries die after two years and negligible miles? Evidently its not heat, and I think you've all established its not charging protocol.

 

[NJS]

And why does tesla get 8 years and unlimited miles out of battery packs regularly cranking out 5C (several hundred kW) when pedelec batteries die after two years and negligible miles? Evidently its not heat, and I think you've all established its not charging protocol.

Cos Telsa restrict the SoC -- lowest discharge / highest charge -- to between 20% & 80% -- you need their special permission/remote authorisation to charge higher than 80%.

That means they don't (cannot) top balance.

 

[danielrlee]

Cos Telsa restrict the SoC -- lowest discharge / highest charge -- to between 20% & 80% -- you need their special permission/remote authorisation to charge higher than 80%.

That means they don't (cannot) top balance.

Tesla do everything that you say, but their BMS's are programmable so that balancing occurs at whatever voltage they want it to, therefore balancing is not compromised. I'm pretty sure they do 'top balance' though, although I'm not totally certain. Another possibility is 'active balancing' that constantly occurs throughout the charge range, although now I'm just speculating.

I'm sure you DO understand that off the shelf ebike batteries have their BMS's balance at 4.2v per cell and they are seldom programmed for anything else. This is why we shouldn't recommend the practice of undercharging in this context.

 

[danielrlee]

And why does tesla get 8 years and unlimited miles out of battery packs regularly cranking out 5C (several hundred kW) when pedelec batteries die after two years and negligible miles? Evidently its not heat, and I think you've all established its not charging protocol.

I'll leave the battery choice for someone else to help, since I tend to not buy 'off the shelf' packs. I would however recommend sourcing from within the UK if after sales service is of any importance to you.

Tesla packs achieve such a long service life due to a number of measures.

Firstly, as NJS correctly states, they only use 20-80% of battery capacity in regular daily usage (unlike most ebike batteries, their BMS deals with this practice in the correct way).

Also, they use active (fan) cooling to keep the pack at optimum temperature.

Additionally, they also use pack heating to bring the cells UP to temperature when operating in 'ludicrous mode' This is to make sure that the pack has the lowest possible internal resistance (IR), so that it can dump HUGE amounts of power with the very minimal of cell degradation.

Lastly, since they own and control the entire cell manufacturing process, they can ensure very high levels of quality control.

EDIT: Ebike batteries have the additional problem that they are much more price sensitive and as a result, compromises are often made that stress the pack far more than is ideal. Also, we often hear of packs that have been left to sit for a long time without usage, which causes issues. Electric cars don't suffer from the same usage issues as they tend to get used much more frequently. When it comes to the majority of lithium ebike batteries, it's definitely a case of "use it or lose it"!

 

[Nealh]

And why does tesla get 8 years and unlimited miles out of battery packs regularly cranking out 5C (several hundred kW) when pedelec batteries die after two years and negligible miles? Evidently its not heat, and I think you've all established its not charging protocol.

It does appear that SOC isn't 100%, to over come this they spec and use a bms with lower balancing voltages. Also I suspect the lower discharge voltage level is higher .