Did you make it compensate for voltage drops?, if not, you should!
Very nice but for me day to day riding I wouldnât use its at all but nice to have for day once a month to check on the levels and to make sure the bms is doing its job. Would it take Mich to make this to sell as I would buy one if was a little more compact.
I am compensating for voltage drop across the whole circuit. But i donât have a precise enough measuring tool for such small voltage drops so i havenât been able to corroborate the numbers to precisions higher than 0.01v
It takes me 2 seconds to check the voltages form my phone to make sure everything is working as intended, it gives me peace of mind (specially since im using lipos). Also, i can keep logs of cell status, etc. And it the software will also give status info on the VESC which is usefull.
I am in the process of making schematics and pcb for this project. Im trying to lay everything out as compact as possible and ideally single layer pcb so anyone can etch/mill their own. Im still trying to find a 12 channel through hole ADC, but its proving hard to find, might use a smd 12 channel but that might complicate some people who are not too good at soldering. If i got the SMD route, i can make everyting REALY small.
Yea I think smaller the better for something like this but have a larger diy version maybe for people with out the capabilities to solder smd.
With the right component selection smd would be as easy as soldering through holes. The only âdifficultâ thing is the 12 channel adc.
Not sure if you understood what i ment.
What i mean is, when you drive the board, and start pulling power from the battery, you get a very large voltage drop on the battery, are you compensating for this?
Not really, why would you want to read anything else than the actual battery voltage? If the voltage is sagging under load, you want to know that.
Well, if your pack is on lets say 30 V, then you accelrate and it drops to 23, when youâre then up to speed it will drop less and go back to letâs say 27, then when you hold still youâre on 29,8 V. You wont get a precise reading (While riding at least) if youâre not compensating for the voltage drop.
Im not sure i understand what youâre trying to tell me.
All batteries drop voltage under load. The bigger the load the more the voltage drop.
Yes, we are all clear about that. And if im going uphill full duty and my battery sags to 20V i want to see those 20V on my battery monitor. Why would i want to see any other âcorrectedâ value?
Because it will say your battery is on 50 % when it might be on 80 %, and iâd like to see the actual range i have left, rather than what voltage it is on at this specific load.
Its a cell voltage monitor. Battery charge level is a whole other thing. It can be implemented, but thatâs not on my list any time soon.
Alright, just wanted to tell you, it would be a neat feature.
The math to calculate voltage sag is incredibly complex, and very dependant on soooo many factors it would be quite hard for the average user to set up properly. You need to take EVERYTHING into account, batteries (type, age, cycles), every resistor, transistor, cap, mosfet, pcb trace, wire, solder job, etc, etc, etc⌠its not something that can just be done and work for everyone.
Made a quick python app for monitoring the cells from a PC, will add some plotting at some point.
3 Likes
I really like your project, might very well build it into my board, when i get to building it.
Do you need any help with the actual app?, also, will you be making it for Android or IOS?, because IOS is supposed to be expensive, for what iâve heard.
Iâm redesigning the electronics at the moment, using differential op amps which should give a much more accurate reading. Im still looking at solutions for cross platform deployment. The windows app is done in python since its quick and easy for such a simple thing. Once i get the mobile app done, i will release the source code so that anyone can build their own.