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Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
I have this R/c Helo, but i believe i have lost the ability to charge it due to its internal overheating.
Background:
The internal battery is seen here:
so, can I charge this single pouch cell with just a LM317 holding 4.225 volts? since no cell balancing voltage issues are present, what voltage would be wise?
Registered Member #509
Joined: Sat Feb 10 2007, 07:02AM
Location:
Posts: 329
I'd just use a max1811 on the 100mA setting, that and a 5v usb style charger, or micro/mini USB phone charger (or any with a 5v regulated output, USB connector on the end is just a good clue it'll be a regulated 5v supply) and youre set.
IIRC you said that you could do a 15min charge or something similar with it? You could try the 500mA setting, but a 4C charge isnt exactly gentle on the cell, though such a small cell has surface area/volume ratio advantage to big cells. I wouldnt be surprised if you puffed a cell charging at 4C though.
However I'm guessing you probably have 317's around so you can set it to 4.20 or so (the energy gained from 4.2 to 4.225 will be not much, and 4.3v is when bad thingsâ„¢ start to happen. For the CC-phase if your supply is regulated, then pick a resistor to put in series between the supply and the 317 to limit the current into a 2.5v cell to around 2C if you want a relatively quick charge.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
ConKbot of Doom wrote ...
I'd just use a max1811 on the 100mA setting, that and a 5v usb style charger, or micro/mini USB phone charger (or any with a 5v regulated output, USB connector on the end is just a good clue it'll be a regulated 5v supply) and youre set.
OK a 5 volt source.
ConKbot of Doom wrote ...
IIRC you said that you could do a 15min charge or something similar with it? You could try the 500mA setting, but a 4C charge isnt exactly gentle on the cell, though such a small cell has surface area/volume ratio advantage to big cells. I wouldnt be surprised if you puffed a cell charging at 4C though.
The booze fuzzied my memory, its actually 30-35 min charge time, a 10C battery.
ConKbot of Doom wrote ...
However I'm guessing you probably have 317's around so you can set it to 4.20 or so (the energy gained from 4.2 to 4.225 will be not much, and 4.3v is when bad thingsâ„¢ start to happen. For the CC-phase if your supply is regulated, then pick a resistor to put in series between the supply and the 317 to limit the current into a 2.5v cell to around 2C if you want a relatively quick charge.
can you explain the "C" rates and math again? Im fuzzy, but sober.
ConKbot of Doom wrote ...
Think VR = Vsupply-2.5v-Vdropout @ 2C mA
I dont see what you mean, by this math? if my supply is 5V-2.5V = 2.5-AnyDrop ... then im already tolow on V?
Registered Member #509
Joined: Sat Feb 10 2007, 07:02AM
Location:
Posts: 329
Patrick wrote ...
ConKbot of Doom wrote ...
I'd just use a max1811 on the 100mA setting, that and a 5v usb style charger, or micro/mini USB phone charger (or any with a 5v regulated output, USB connector on the end is just a good clue it'll be a regulated 5v supply) and youre set.
OK a 5 volt source.
ConKbot of Doom wrote ...
IIRC you said that you could do a 15min charge or something similar with it? You could try the 500mA setting, but a 4C charge isnt exactly gentle on the cell, though such a small cell has surface area/volume ratio advantage to big cells. I wouldnt be surprised if you puffed a cell charging at 4C though.
The booze fuzzied my memory, its actually 30-35 min charge time, a 10C battery.
ok, 30-25 is ~2C for charging,fast, but not dangerous for a cell meant for it.
Patrick wrote ...
ConKbot of Doom wrote ...
However I'm guessing you probably have 317's around so you can set it to 4.20 or so (the energy gained from 4.2 to 4.225 will be not much, and 4.3v is when bad thingsâ„¢ start to happen. For the CC-phase if your supply is regulated, then pick a resistor to put in series between the supply and the 317 to limit the current into a 2.5v cell to around 2C if you want a relatively quick charge.
can you explain the "C" rates and math again? Im fuzzy, but sober.
C = AmpHour/milliAmpHour rating of the pack/cell, for a 130mAh cell, 1C = 130mA, 2C = 260mA, 10C = 1.3A
Patrick wrote ...
ConKbot of Doom wrote ...
Think VR = Vsupply-2.5v-Vdropout @ 2C mA
I dont see what you mean, by this math? if my supply is 5V-2.5V = 2.5-AnyDrop ... then im already tolow on V?
With a 317, the dropout voltage is ~ 1.6v, so you'd not be able to work with a 5v supply anyway, but assuming a higher voltage supply,
2.5V is the lowest you should be running the Li-Po battery, so the greatest current draw will be at this point too. You want to limit your current to 260mA. If you have a 1.6v dropout on the 317, and 2.5v on the load side, than it going to be 4.1v on the input terminal. Using a 9V supply, that leaves 4.9v to drop @ 260mA, or ~18 ohms in series with the 317 to keep it from drawing too much when the battery is low.
This wont be a true constant current by any means, but would be a quick and dirty way to make something that would charge the battery safely, by sagging the input voltage of the 317 enough to pull it out of regulation while its in the CC phase of charging
If you wanted to build a more proper sort of charger with 317's then 317 setup for constant current (almost 3V dropout!) with a voltage regulating one after that (~1.5-1.6v dropout). Hooked up to the battery. This would be charge faster than just using a resistor to sag the input voltage to the regulator, since it would give a full 260mA all the way to the battery reaching 4.2v, but you'll need a 9V supply instead of 5 with the maxim chip.
Registered Member #3761
Joined: Tue Mar 15 2011, 12:29AM
Location: Toronto, Canada
Posts: 15
Grenadier wrote ...
I'm surprised that nobody mentioned that that cell is puffed up.
DO NOT CHARGE IT.
Just to restate Grenadier post trying to charge will make it explode and not a pop but a large fiery one, the cell is puffed. It is now dead weight, Because the cells are made cheaply they likely had a small amount of water in them or other contaminated lithium and the lithium has degraded. do not puncture it either. I've had this happen to many of my cells, Its not caused by heat but by just by a bad cell or over charging. Because of the cheaply produced helicopter there is no protection for the cell and if you discharge the battery fully continually this can happen.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
The battery is fine, you all are too panicky.
Besides, how can any of you know that its buldged? it looks the same now as the day I bought it and took it apart. It looks the same now after 14+ flights. I believe thats a thermistor wraped around it too.
also, I have exploded batteries before, this one doesnt seem close to the edge.
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Helix 360 ... Li Battery charging problem.
