Making this thread for anyone else having the same issue, I’m done with the mechanical parts of my build, I got the iOS version of the BMS app, Xiaoxiang, I successfully connected my BMS to it. But I’m confused on what to set for the values, I got a 4500mAh two lipo batteries, the peak voltage they go is 42v, discharge rate of 37v. Help would be appreciated if anyone can tell me what this all means
You need to press bms read first to see the default values
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BMS
- DESIGNED CAPACITY
- What is the range of the pack in mAh
CYCLE CAPACITY
- How long do you ride/cycle before you charge
FULL CHARGE VOLTAGE
- Your single cell max charge. Defaults 4150 or 4.15V per cell
END OF DISCHARGE VOLTAGE (Most likely bypassed)
-
Your single cell voltage max low. Defaults 3000 or 3.00V per cell.
-
when the BMS cuts of your power due to low battery IE End of discharge voltage.
SELF-DISCHARGE RATE
- How fast the pack will discharge while not in use.
- may want to set to 0 for lipo’s.
80% 60% 40% 20% Capacity Voltage
- I assume this is for warnings to be shown when hitting these marks.
START VOLTAGE
- When balancing should on a given cell. default is 4000mV or 4.0v
DELTA BALANCE
- How finely you want your balancing to be in mV.
- Default is 30mV or .03V.
- This means it will attempt to balance each cell within 3/10th or a V
BALANCE ENABLED
- self explanatory
BALANCE ONLY WHEN CHARGING
- self explanatory
- may want to leave set to only charge so your battery is not working more than it should when not in use.
CELL OVER VOLTAGE
- [Trigger] When do you want the BMS to stop the flow of current based on a cell.
- [Release] When do you want the BMS to allow current to flow again and remove warning.
- Default is 4250mV or 4.25V per cell, which I believe to be too high.
- I will set mine at 4150 or 4.15V and release to 4050mV or 4.05V
CELL UNDER VOLTAGE
- [Trigger] When do you want the BMS to stop the flow of current based on a cell.
- [Release] When do you want the BMS to allow current to flow again and remove warning.
BATTERY OVER VOLTAGE
-
This is your batteries max charge of the entire pack.
-
default is 51000 or 51.0V
-
[Trigger] When do you want the BMS to stop the flow of current.
-
[Release] When do you want the BMS to allow current to flow again and remove warning.
BATTERY UNDER VOLTAGE (if discharge is bypass this is ignored but can throw flags/warnings if not set.)
- This is your batteries max low of the entire pack.
- default is 32400 or 32.4V
- [Trigger] When do you want the BMS to stop the flow of current.
- [Release] When do you want the BMS to allow current to flow again and remove warning.
CHARGE OVER CURRENT
- BMS will cut power from charger’s that exceed these set parameters .
- Example: If you plugged in a to powerful charger this can prevent harm by cutting the current.
DISCHARGE OVER CURRENT (ignore if BMS is bypassed)
- BMS will cut power to source of what ever is drawing to much current based on these settings.
CHARGE OVER TEMP.
- Prevents charging when too hot.
CHARGING UNDER TEMP
- Prevents charging when too cold.
DISCHARGE OVER TEMP
- prevents power to board if too hot.
DISCHARGE UNDER TEMP
- prevents power to board if too cold.
xiaoxiang BMS CONFIG
DESIGNED CAPACITY
- What is the range of the pack in mAh
CYCLE CAPACITY
- How long do you ride/cycle before you charge
FULL CHARGE VOLTAGE
- Your single cell max charge. Defaults 4150 or 4.15V per cell
END OF DISCHARGE VOLTAGE (Most likely bypassed)
-
Your single cell voltage max low. Defaults 3000 or 3.00V per cell.
-
when the BMS cuts of your power due to low battery IE End of discharge voltage.
SELF-DISCHARGE RATE
- How fast the pack will discharge while not in use.
- may want to set to 0 for lipo’s.
80% 60% 40% 20% Capacity Voltage
- I assume this is for warnings to be shown when hitting these marks.
START VOLTAGE
- When balancing should on a given cell. default is 4000mV or 4.0v
DELTA BALANCE
- How finely you want your balancing to be in mV.
- Default is 30mV or .03V.
- This means it will attempt to balance each cell within 3/10th or a V
BALANCE ENABLED
- self explanatory
BALANCE ONLY WHEN CHARGING
- self explanatory
- may want to leave set to only charge so your battery is not working more than it should when not in use.
CELL OVER VOLTAGE
- [Trigger] When do you want the BMS to stop the flow of current based on a cell.
- [Release] When do you want the BMS to allow current to flow again and remove warning.
- Default is 4250mV or 4.25V per cell, which I believe to be too high.
- I will set mine at 4150 or 4.15V and release to 4050mV or 4.05V
CELL UNDER VOLTAGE
- [Trigger] When do you want the BMS to stop the flow of current based on a cell.
- [Release] When do you want the BMS to allow current to flow again and remove warning.
BATTERY OVER VOLTAGE
-
This is your batteries max charge of the entire pack.
-
default is 51000 or 51.0V
-
[Trigger] When do you want the BMS to stop the flow of current.
-
[Release] When do you want the BMS to allow current to flow again and remove warning.
BATTERY UNDER VOLTAGE
(if discharge is bypassed this ca be ignored but can throw flags/warnings if not set.)
- This is your batteries max low of the entire pack.
- default is 32400 or 32.4V
- [Trigger] When do you want the BMS to stop the flow of current.
- [Release] When do you want the BMS to allow current to flow again and remove warning.
CHARGE OVER CURRENT
- BMS will cut power from charger’s that exceed these set parameters .
- Example: If you plugged in a to powerful charger this can prevent harm by cutting the current.
DISCHARGE OVER CURRENT (ignore if BMS is bypassed)
- BMS will cut power to source of what ever is drawing to much current based on these settings.
CHARGE OVER TEMP
- Prevents charging when too hot.
CHARGING UNDER TEMP
- Prevents charging when too cold.
DISCHARGE OVER TEMP
- prevents power to board if too hot.
DISCHARGE UNDER TEMP
- prevents power to board if too cold.
.
.
.
So I think I have Documented the config pretty well.
Let me know if you see any issues with this explanation or ways I can edit to make more clear.
Side note: this is not how I have my config setup but this is my understanding of the config itself hope it helps.
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Ok thanks, i’ll try that later today
Oh man, have no idea how much this helped, so for my batteries the safest discharge rate is 37v since their lipos. And the highest is 42v. Since i can set battery cutoff voltage in the VESCtool so the VESC can start cutting power but still preserve some till the batteries hit the targeted voltage and still be the safe zone, voltage wise I’ll be using the BMS for charge only, the one question i do have is
So the Lipos i do have the max voltage they can handle is 42v, so 80% could be 4150, 60% 4010, 40% 3945 and lastly 20% can be near 37v but 37v would more like be the end. Rounding off around 36v which is the best for lipo packs so they don’t get damaged from reviving them from such a low voltage, thats why 3v isn’t healthy. It’ll be a while till i get new upgrades so i need to baby the batteries as much as i can
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Correct me if i’m wrong. So my over charge is 42000 or thats the practical limit (aka 100%) so should i set the value to 4210 (42.1V) for overcharge, or have it at 42V so it stops right when it hits the value?
Since 32.4V is too low, i can set the under voltage trigger to 37.10 and can set the release when its back to 42v? Would that work or I’m not making any sense lol
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I believe this to be correct, at least your understanding.
There are balance settings also, these will effect this full state also.
Lets say you set to 100%/42.1V and place on charger and its full.
The BMS should or can enter balancing (settings you pick)
if it enters balancing at 100% this can go over 100% on some cells when attempting to balance.
I think this is why it is set a little below what is actually full. 51.0V default or 54V full 12S pack.
My thoughts are the default is a bit lower due to the balancing effects.
I would again say yes, this sounds right.
You can always set some settings higher/lower within reason to test what effects they have.
I had to do this with my charge settings, I wanted my Lipos only to charge to 95%, then I can bomb down
my driveway without worry of over regeneration.
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Ok cool, I was reading up on all that yesterday to get a better understanding, glad everything I said is correct. I’ll also just see what the BMS has it at for default, and just change some things if the value isn’t where it needs to be. I most likely will set the overcharge to 42 and release at 4150, just to safe if the default level is too low
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Got a question about the Xiaoxang BMS app, buttoning up the settings on my first build. Running two 5s lipo batteries in series, not sure if I put everything in correctly, I read the original settings set and changed some values as well. Just making sure before it warms up so I can finish my diy deck and take this thing on the road
Charge under-temp protection should never be below 0°C. This is a safety issue.
Charge over-temp should be a lot lower IMHO. 65°C is really hot for li-ion cells and they will be aging a lot faster if your charging is this aggressive. I recommend a 45°C max but it depends on your priorities…convenience versus pack life.
I didn’t change those values, it was whatever the BMS read out, some settings I did change, others I wasn’t sure their correct. What you think I should set it too?
I already mentioned that. 
0°C lowest for charge under-temp and 45°C max for charge over-temp (or higher if you use a fast charge rate and convenience is your priority over pack life).
Oh shoot my bad, didn’t see that. Ok do you see anything else that needs to be fixed?
Edit: Not sure what this means as well if the value is even right, my first time doing all of this and wanna make sure it doesn’t blow up 
There are some settings that seem to be wrong but I don’t know that software and what they actually mean with those different setting names. Hopefully someone else can chime in with some recommendations.
Alright, appreciate it. Haven’t had any luck with replies on this yet besides you. We’ll see tho
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Give it a couple days at least, many don’t get on very often.
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So I found the right version of the app, plugged in the charger and this is what the balance page looks like, did I do something wrong?
Does the light on the charger indicating that it’s charging?
More than likely your balance wires are in the wrong order
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It has been going from charging to green back and forth seemingly randomly.
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