Hi all, Im looking to build a Nese battery module with 26650 a123 lifepo4 cells. Wondering if my esc would tolerate it if I go all the way up to 14s because then the voltage will be similar to a 12s li ion/ lipo?
My esc is the new-ish one from torqueboards.
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If it can handle 12s Li-ions, it will handle 14s lifepo4. Same voltages.
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I only charge mine to alittle over 3v per cell due to the sharp drop in voltage from 3.65 down to 3v where it levels off on the discharge curve. Works great. Shortly after you start riding your 14s will lvl off to arround 42v…around and equal to 10s lion. 16s @3v would put you around 48v.
I think that first big dip in the discharge curve from 3.6 downwards finishes around 3.2-3.25V, depending on cell and load. This is from a fairly small amount of googling though so lmk if it’s out of date, but it looks like 3V is kind of near the end of the capacity just before the second big dip
At 3.2 @14s gives about 44.8. 51.2v at 16s
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My LiFePO4 spend most of their time discharging around the 3.24 - 3.29 V/cell range which is 45.3 - 46.1V in 14S
I set the cutoff at
Awesome thanks. Do you guys know if 14s would risk damaging the vesc? I just read a thread from 2 years ago and @b264 was saying 12s li ion is past the upper limits of what the vesc is rated for and therefore he prefers 10s li ion over 12s. Wondering if that rule of thumb still stands 2 years later with updated vesc technology maybe
who’s vesc? alot has happened in 2 years
Most of the new stuff is fine with that. I would not use a VESC 4.12 with it.
A 60V ESC is still better to not run at 85% of its rating but folks are doing it all the time.
If it’s a commuter vehicle or high reliability is important, I would consider 12S LiFePO4.
The other thing with LiFePO4 is that they plummet SUPER fast from 3.65V. Just idling the ESC for a few seconds while you get ready to ride it can already knock a few volts off, that’s just the nature of LiFePO4 with a super flat discharge curve and an almost vertical spike at the end of charge. So in this sense, at 14S it won’t be over 50V for long at all, if any, while the motors are being used.
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I have the newest one from torqueboards
Very cool thanks
Does 14s lifepo4 have a noticeable power boost compared to 12s lifepo4?
Motors run on current. The biggest difference would be a 16% higher top speed.
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I used to run my AT commuter board with 16s lifepo4 cuz couldn’t find a 14s bms. Charged em up to 57.6V then it will dip down by itself to around 54V if left alone for a while - typical lifepo4 characteristic. When riding, that 54V will quickly drop and settle down to the flat part of the voltage curve around 52V-53V. I actually prefer the voltage curve of lifepo4 over that of Li-ion.
As for the vesc I paired it with, it used to be fsesc4.20 plus. ikr I was running a questionable esc with a voltage equivalent to 13s. Had no issue running it on bldc mode.
Lifepo4 is known for being tough and I was expecting it would outlast all other components of my board. Too bad the pack is ruined by the combination of bad bms and my inexperience. The fsesc4.20 plus is still alive btw.
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very interesting. off topic sort of, but do you know approximate range for lifep04 packs? is there a calculator? obviously very different for your at board vs my street
If you calculate the capacity of the pack in watt-hours, you can calculate range the same way as with a Li-ion pack. Usually we use Wh per km (or miles if you’re wrong) to measure power consumption or efficiency of a board or riding conditions, if you don’t know what you consume you can try work it out with a range test or post your build and people will give a rough idea of what to expect.
To get the capacity of the pack in watt-hours:
Wh = (V) x (Ah)
If you’re using 14S LiFePO4 that would be (44.8V) x (Ah of the pack)
Range depends on many factors, mainly about the capacity of the pack.
A li-ion and a lifepo4 packs with he same WH will yield the same theoretical range based purely on capacity. The chemistry of the battery pack does not matter as long as the capacity is the same. But if we factor in the energy density of the packs, you’ll get slightly lesser range with lifepo4. It is much bigger and heavier compared to it’s li-ion counterpart. More weight results in less range.
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The calculator is linked in the top bar
Ffs I didn’t realise the calculator had a LFP setting, that’s much less complicated
Is Voltage sag an issue with a 14s2p Lifepo4? Considering going to 12s3p to reduce sag, but wondering if the superior chemistry of Lifep04 makes sag a non issue