48v ebike battery voltage chart -???

[jeffieh]

I found this on the internet.
On the face of it, a super-useful tool for calculating battery range.
Def NOT a battery expert.
You techies out there - can it be relied on for accuracy (eg the battery has 70% charge at 49.7v) ?

Many thanks in advance.

 

[Chalo]

Differences in chemistry, even subtle ones, change the battery's discharge curve. You can't correlate resting voltage to state of charge with that level of precision unless you test your specific battery through a full discharge.

As for me, I treat 49.0V as the halfway mark for my lithium NMC packs. Maybe that leaves me a little in reserve, but I don't like to push it.

 

[amberwolf]

It also depends on the condition of the battery.

If it is brand new with matched cells (which isn't common for the typical ebike battery, but would be for large-EV packs, including ebike packs built out of used EV modules), then it might apply.

As the battery ages, the voltage it drops to under load will be different for any particular SoC (state of charge), and the total capacity it has will be different, so the voltage you see even under no load will represent a different total range.

If the cells are not matched (which is likely), they won't stay balanced over the discharge curve, so the voltage you see at the pack output won't necessarily match the same point in the chart. The lowest capacity/capability cell (group) in the series set of them will limit the entire pack to that capacity.


You can see discharge curves for many kinds of cells over here:

Batteries and chargers

 

[Hillhater]

“…can it be relied on for accuracy (eg the battery has 70% charge at 49.7v) ?”
In a word NO !
Be careful, That chart doest even say what the battery construction is ,.. 12S, 13 S , etc ,..let alone what chemistry its for… ,lico, lipo, NMC, LiFe , etc
For example, my 48v 12 s, lipo pack would be dangerously overcharged at 53v !

 

[tomjasz]

That chart came from a moderator on electicbike.com in 2015. If you do the math it's close but not entirely accurate

 

[jeffieh]

Thanks for all your feedback on this. I'm now a little less excited about using the table as a hard-out measure of charge - and predictor of range. Oh well...

 

[jeffieh]

Differences in chemistry, even subtle ones, change the battery's discharge curve. You can't correlate resting voltage to state of charge with that level of precision unless you test your specific battery through a full discharge.

As for me, I treat 49.0V as the halfway mark for my lithium NMC packs. Maybe that leaves me a little in reserve, but I don't like to push it.

49v eh? I might try that.

 

[Hillhater]

O

49v eh? I might try that.

yet again….. its not that simple..
…..it will depend on you particular pack construction 12s 13s 14s ?? And cell type, chemistry, etc

 

[Chalo]

O

yet again….. its not that simple..
…..it will depend on you particular pack construction 12s 13s 14s ?? And cell type, chemistry, etc

To be fair, his chart referenced Li-ion at 48V nominal voltage, which is 13S. So that's what I was talking about. You're correct that halfway down would be a different voltage with 12S or 14S Li-ion, 16S LiFePO4, 40S NiMH, 24S lead-acid or whatever.

 

[docw009]

It's based on a 48V ebike controller that shuts off around 40V, If you start thinking that your 48V ebike pack has 0% charge left at 40 volts, the resulting fire if you accidentally short circuit the battery will tell you otherwise,

Your results will depend on the size of your battery, A very large 48V24AH battery could power your bike all the way to 40V. A small 48V10AH battery might shut off at 44 volts because of voltage sag, never nibd the chart sez 20-30% left,




,