so when my batteries get really low, of course my board slows down a bunch. I’m talking like 10 or 15 percent here. If I ride it til its at zero I know normally this will damage my battery but with the vesc I have set a cutoff. so is that 10 percent battery that I see on my phone 10 percent til the cuttoff or 10 percent till the battery is actually dead and by using the battery in those last 10 percent I’m damaging it.
We’d need to know some additional information. What app are you using to get your info from VESC? What are your battery cutoff settings? What voltage is your battery?
My guess is that your app is reporting percentage of total voltage and disregarding battery capacity.
@treenutter I’m using the vesc monitor app. On bldc my start cuttoff is 3.5 and end is 3.2 or 3.3 I forget which. My battery is a 10s lipo
I think with you should base on your vesc cut off and that would be safe. 10% reading on your phone is just a number based on how you set each % to a certain voltage. ( since battery discharge is not linear line ). you shoudn’t be worry if you set you cutoff right in VESC.
With lipos you never really know. Sure the VESC protects if the overall pack voltage gets low. But it does not protect each cell like a BMS does
Running to 3.2V nominal on lipos is really low. Might work for a while but eventually your cells will degrade. Some could actually be at 2.9V or below
Hope you don’t burn up your house
for lipo 3.0 is absolute 0. 3.7 is about 30 percent. from my experience 3.3 is like 5 percent
Ok so like 3.5 is a good in between maybe? Or could I go 3.4
Well I mean as long as I don’t run it past zero percent I should be fine right? Or would u say even 5 percent is too low and Will damage the batteries
Lithium packs are best when only taking 80% out of them
Lipo voltage range of 3.75-4.20v, Taking lipos any lower with load will degrade the packs. And typically begin to sag quite a bit once they go past storage voltage(3.75v). Full discharge on LiPO is considered to be 3.6, however if you are breaking in packs, a low static discharge of .5 amps, down to 3.0v/c will yeild the mAH rating of the pack. Lipo’s are the most volatile when it comes to balance runaway, if you discharge past 3.65v under load you will have very very quick balance runaway. which is not good
Li-ions working range - depending on the cell is 3.35-4.20. While most li-ions can discharge to 2.5v the current curve falls off around 3.35v/c
Life working voltage is 2.9-3.4v, any lower then 2.9v and the current curve falls off and begins to have voltage sag. Most life can discharge to 2.0v, but again any lower then 2.9v and your have voltage sag
for a 10s setup
lipo - max input 48v, min input 35v, cut off start 38v, cut off end 37v liion - max input 48v, min input 30v, cut off start 35v, cut off end 33.5v life - max input 46v, min input 28v, cut off start 30v, cut off end 29v
The above should leave you with about 20% charge on each of these configs, Discharging more then 80% under load from lithium cells is just abuse.
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I set it really low cuz i dont care that much of life span. i put cut off at 3.2. typically cycle is abaout 800 but if u salvage it. cutt off at 3.5 u can increas to about 1000 to 1200. 3.7 is really good but it wont really go beyond. it will get voltage sag and lower mah. quality lipo dont get sag under load anywys
Thats an incorrect statement, ALL batteries have voltage sag under load. Taking Lipos below 3.6 under load is asking for them to puff/swell and will destroy the IR of the pack, continual abuse will only make the IR higher, as the IR gets higher, the pack gives off less and less ampers with increased voltage sag. Eventually it will reach the point where either the pack ignites, or the pack will be fully charged but sag so much that you hit Low voltage cut off right after you start riding. Internal Resistance is a key player in all lithium battery’s health and amper capability.
Take care of your packs.
Also your statement about quality lipos
Quality lipos typically have an IR of 1.5-3.0milliohms, while lower quality packs will have around 3.0-11milliohms IR.
JUST ONE TIME on an abusive discharge can increase the IR to that of a lower quality pack. On lithium polymers they pretty much become useless at around 15-18milliohms/cell and have so much sag that all they do is generate heat because of their IR. Once they get upto 25-40milliohms IR you have ticking time bombs any time you discharge, and each discharge is damaging the cell further because the majority of the layers have already been comprimised.
WIth your methodology of discharge you could ruin a pack in as little as 10-25 cycles. lol…If your not actively watching your IR over time, you really have no clue about a packs health.
Ok thanks for the info and recommendations@deckoz Super useful. back to my original question, after I feel the board start to slow down, is it okay to keep riding it? Does slowing down mean it has reached the upper cuttoff limit or the lower one.
When it starts to slow down its OK to keep riding. Just know you have limited range left. Eventually it will cut off.
Ok thanks so I can basically ride it till it stops and not have to worry about killing my lipos
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Yup as long as your params are set right.
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ok @Deckoz so I changed it, and now I seem to be getting significantly less range than before. like I only got about 6 miles, whereas before it seemed like I was getting a lot more. also before, it would be at full power until the very end when it would dip but now it seems like that period of lower power lasts longer.
you can change the threshold of when the cuttoff starts - but i would keep the cutt off end where they are supposed to be.
Hmm 3.7 seems super high. Idk seen other people run it at like 3.5 but if u say it has to be at 3.7 then I guess I’ll keep it there. Will it really damage the battery that much if it’s a tad lower? I just have some cheap hobby King batteries btw. Nothing fancy
I’ve heard people say to set it to 3.3 as well. seems all over the place