battery percentage

[mike killay]

Am I the only one getting tired of our resident troll?

 

[Woosh]

when you keep battery at 80% when stored, is that 80% of 36v or 42.2
thanks

that's 80% of a full charge.
if your battery is completely flat, the voltage across its output pins would be about 31.5V. When it's 100% full, that will be about 41.5V.
At 80% full, the voltage is about 39V.
Lithium ions move from one electrode to the other when charging and in the opposite direction when discharging. The best way to store them is when both electrodes contain the same amount of Lithium, that is usually 36V. As they lose their charge over time, the recommendation is that you keep it a little above their 50% SOC (state of charge).

 

[Nealh]

Am I the only one getting tired of our resident troll?

No, that's why I can't be bothered to play ball.
Cutting and pasting all the time it's like plagiarism.

 

[Andy-Mat]

Andy, can I suggest that you are possibly taking some of the criticism that you receive on this forum a little too personally.

VFR is widely regarded as one of the most knowledgeable and practical electric bike experts on the planet. Admittedly, I wouldn't describe him as a 'people person' – he shoots from the hip and doesn't mince his words, but he does deal with facts and data, rather than beliefs, feelings or unfounded opinions. Every so often he does cross the line between being 'blunt' and 'rude', but that should not detract from the quality of the information he is able to offer.

You're not the first person to offer well-intentioned, but out-of-context information on this forum and I'm certain that you won't be the last. The problem with doing so is that it encourages bad practice and becomes exponentially more difficult to stamp out and re-educate as time passes.

Self-improvement involves accepting the possibility that you could be wrong. I've been wrong about lots on the subject since my first exposure to electric bikes in 2012. I only stopped being wrong once I was prepared to listen to augments critical of my own ideas and beliefs. I'm sure VFR would admit a similar learning experience. Don't let pride and stubbornness be a barrier to your own self-improvement.

Dan

He is a purveyor of bad facts, especially to do with electricity. Naturally you can chose to believe who you want, its a free world here in the EU, but if you had looked at the links I posted, from good reliable web sites in answer to his bad information, he not only totally ignored those good facts, but went off on another "tangent", also with no supporting information, compare yourself, you might get the right idea.
He is OK on mechanical bits, its mainly his electrical knowledge that is very poor, some informed people might even say dangerous to the longevity of the battery.....
But as I said, its a free world, each of us may choose what we want to believe.....
By the way, the reason he picks on me is that apparently he believes that I "was" someone else here at one time, who he did not get on with. Who that was I haven't a clue....But I have always had the same avatar here....Never another one! He could get that info from the forum owners if he wished!
Regards
Andy

 

[danielrlee]

He is a purveyor of bad facts, especially to do with electricity. Naturally you can chose to believe who you want, its a free world here in the EU, but if you had looked at the links I posted, from good reliable web sites in answer to his bad information, he not only totally ignored those good facts, but went off on another "tangent", also with no supporting information, compare yourself, you might get the right idea.
He is OK on mechanical bits, its mainly his electrical knowledge that is very poor, some informed people might even say dangerous to the longevity of the battery.....
But as I said, its a free world, each of us may choose what we want to believe.....
By the way, the reason he picks on me is that apparently he believes that I "was" someone else here at one time, who he did not get on with. Who that was I haven't a clue....But I have always had the same avatar here....Never another one! He could get that info from the forum owners if he wished!
Regards
Andy

*sigh*

 

[Deleted member 25121]

Full is 42 volts, empty is about 30 volts, most people recommend for storage 34 volts or thereabouts, on a 36 volt battery.

Sorry, storing at 34V is far too low, maybe you made a calculation error so please allow me to correct it for the benefit of others who might be following this thread:
I'll use your figures of 30V empty and 42V full battery, giving a voltage range of 12V.

Bosch recommends storing batteries "at approx 30% to 60% of charge status", see page 27 of https://www.bosch-ebike.com/fileadmin/EBC/Service/Downloads/Akku_Guide/Akku_Guide_August_2019/Bosch-eBike-Battery-Guide-MY2019-EN.pdf?_=1535448290

So, Bosch's
maximum recommended storage voltage = 30V + 60% of 12V, = 30 + 7.2V = 37.2V
minimum recommended storage voltage = 30V + 30% of 12V, = 30 + 3.6V = 33.6V

If you leave your battery at 34V it's only just above the minimum and could quickly drift below it.

Most people recommend using a storage voltage of 38V (your min voltage of 30V is typically 31 to 32V so this is in line with Bosch's recommendations).

 

[vfr400]

Some of the more sophisticated batteries, like Bosch,have sleep mode, which shuts down the BMS so that you can leave them for a long time without any significant self discharge. This means that they can be stored at a lower voltage.

Most ebike batteries don't have sleep mode, so the BMS is drawing a small amount of power whether the battery is stored or not. What's worse is that some take their power from only one cell, so that one cell will go down 10 times as fast as those where the BMS takes its power from all cells. If you were to store any of these types of battery at 34V, the cells are already tipping themselves down the steep precipice, where the voltage accelerates downwards as they give up their charge to the BMS. That's why you need to store them at a much higher voltage.

Think of your battery as a vessel full of water this shape draining away:

 

[cyclenut1952]

Thanks, would you know if Apache batteries have sleep mode?

 

[Deleted member 25121]

Some of the more sophisticated batteries, like Bosch,have sleep mode, which shuts down the BMS so that you can leave them for a long time without any significant self discharge. This means that they can be stored at a lower voltage.

Most ebike batteries don't have sleep mode, so the BMS is drawing a small amount of power whether the battery is stored or not. What's worse is that some take their power from only one cell, so that one cell will go down 10 times as fast as those where the BMS takes its power from all cells. If you were to store any of these types of battery at 34V, the cells are already tipping themselves down the steep precipice, where the voltage accelerates downwards as they give up their charge to the BMS. That's why you need to store them at a much higher voltage.

Think of your battery as a vessel full of water this shape draining away:
View attachment 33237

Yes, even more reason not to store your battery when it's down to 34V as he was advising....

By the way, I can confirm that the self discharge rate on by Bosch batteries is extremely low, maybe 1% every 3 months if that.