Lipo charger from arduino?

Projects General Guidance
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Hi,

Well, I'm rather new here, so sorry if this is posted on the wrong spot (Let me know and I shall learn) But I am very curious if I can build battery chargers with an arduino. I am VERY familiar with the dangers of lithium-based batteries (and how they work) and I'd love to be able to build my own charger because all the balance chargers I have bought are... really not that great, but being as I am, I LOVE electronics and building so I think I'd rather try to build one myself as I like it and want it.

I am not good with programming, but I am quite fine with visual programming.

Is the idea feasible? to build a lipo charger with an accuracy of down to 0.001v per cell?

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Most chargers don't have a programmable microcontroller or software... But yes, it's feasible.

to build a lipo charger with an accuracy of down to 0.001v per cell?

No... The Arduino has a 10 bit ADC (analog-to-digital converter). That gives you 1024 "steps" for 5mV resolution on the 5V range or 1mV resolution on the optional 1.1V reference (too low for your battery).

If you are charging in series you'll need a voltage divider, or multiple voltage dividers, to keep the voltage below the 5V maximum and your resolution will be reduced proportionally.

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Umbra_Therios:
...to build a lipo charger with an accuracy of down to 0.001v per cell?

Is this for lab testing cell capacity (I assume for a 4.2volt cell).
Can't see any other reason why you want this precision.
Leo..

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DVDdoug:
Most chargers don't have a programmable microcontroller or software... But yes, it's feasible.
No... The Arduino has a 10 bit ADC (analog-to-digital converter). That gives you 1024 "steps" for 5mV resolution on the 5V range or 1mV resolution on the optional 1.1V reference (too low for your battery).

If you are charging in series you'll need a voltage divider, or multiple voltage dividers, to keep the voltage below the 5V maximum and your resolution will be reduced proportionally.

well, that is rather depressing...

Hobby chargers have programmable microcontrollers in them though. its how they have so many features, settings and other things and can often be hacked with custom software (like cheali software)

Wawa:
Is this for lab testing cell capacity (I assume for a 4.2volt cell).
Can't see any other reason why you want this precision.
Leo..

for hobby use. I build drones and my charger balances down to within 0.004 ish volts but that difference can shorten the lifespan of the cells if it ends up being higher than 4.200v, it will increase internal resistance over time and... generally bad stuff. its a very good charger too, but not as good as a 600 dollar charger (which has the accuracy I want) which is so far out of my budget I might as well call myself the president if I could get it. I do enjoy building things and I can balance cells down to 0.0001v with my multimeter but that is tedious and I dont have time for it so I would like a way to just build one myself.

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The difference in lifetime between a lipo charged to 4.200V and 4.201V is going to be somewhere between zero and unmeasurable. Unless of course you have some scientific (and I don't mean anecdotal) evidence showing otherwise?

It's also very unlikely that your multimeter can measure to anywhere near that accuracy. Even a well-calibrated top-end Fluke has a basic accuracy of usually +/-0.1%+1 digit so when measuring 4.200V it could read 0.005V out, plus or minus.

You may be rather overthinking this.

Steve

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I agree that the difference in the 2 chargers will make very little difference in cell health. Current draw and minimum voltage on discharge will be a much bigger impact.

But if you want to pursue, I think there are external ADC units with greater precision.

Edit: I googled 'analog to digital 24 bit' and found many examples.

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slipstick:
The difference in lifetime between a lipo charged to 4.200V and 4.201V is going to be somewhere between zero and unmeasurable. Unless of course you have some scientific (and I don't mean anecdotal) evidence showing otherwise?

It's also very unlikely that your multimeter can measure to anywhere near that accuracy. Even a well-calibrated top-end Fluke has a basic accuracy of usually +/-0.1%+1 digit so when measuring 4.200V it could read 0.005V out, plus or minus.

You may be rather overthinking this.

Steve

It's a fluke 287. yes it can, look it up or get one yourself if you don't believe me. (Or I can send a photo, if I must and if I can.) And it has an accuracy of 0.025% ish (on lower voltages atleast.)

Still though, I like precise measurements because I like consistency in my flights and as I also said, I like building even though my charger suffices, and while a millivolt over 4.2 is negligible in damage, I still like to take care of my batteries and I do like precision, is that such a sin? :frowning:

vinceherman:
I agree that the difference in the 2 chargers will make very little difference in cell health. Current draw and minimum voltage on discharge will be a much bigger impact.

But if you want to pursue, I think there are external ADC units with greater precision.

Edit: I googled 'analog to digital 24 bit' and found many examples.

it depends on the charger. some chargers can be calibrated. some cant. my imax b6ac (it has 5% accuracy components on the inside instead of 1%) only charges to between 4.174v and 4.186 randomly and I lost 1 minute and 30 seconds of flight time (and it damaged one of my cells because the battery was so inbalanced and during use that cell got pulled down to 2v while others stayed at 3.5 ish volts) compared to my antimatter charger which charges to 4.20 ish when I calibrated it, give or take 5 or so millivolts.

It's a tad more complicated than just saying "the difference is neglegible" or "the different between 2 chargers are neglegible" because there are many factors involved :confused: Thats another reason I hope to build my own charger, because then I know I can calibrate it myself and now have to spend more than I already have in things that... really disappointed me, except for my antimatter charger.

is it so wrong to want to build something better?

Thanks for the info though, I will check those out and see what I find.