A123 20ah PRISMATIC CELL from A123rc (Solar Charger)

a123prismatic00.JPG
 
What do you have in the way of power supplies? A simple lab-type power supply that has adjustable voltage and adjustable current limit will safely charge it.

Discharging, well, from the stuff I've read on the forum so far, you could drop a crowbar across it and the only thing it will hurt is the crowbar and your eyes. :lol:

But realistically, there are a few discharge testing methods around in various threads about testing A123 cells (and other cells), including some buried within threads about how to connect these cells up into packs.
 
Discharging a single cell is not as easy as it would seem, well discharging it quickly at least. You could easily discharge one with a cheap lipo charger that also has a LiFe setting but they usually only discharge at 20-25W unless you pay $100+ for a decent one with either regenerative discharge or discharge+ feature. so at best your going to be looking at a 5-7amp discharge rate. even the element from a 1000watt space heater would only pull about 30watts from the cell at 3.3v. About best way i can think would be a high wattage, low voltage step up DC/DC converter to step it up to 12V, then you would have no problem pulling 20-30 amps out of it with the right converter.

Any more than 20-30 amps and then your looking at a lot of $$$ just for the discharger, i once watched a youtube vid of someone pulling 300amps from a single A123 20AH pouch with a massive resistor the size of beer keg, no idea where they got it from though.
 
It's easy to discharge at stupidly high rates. Jumper leads coiled inside a bucket of water to keep them cool. Clamp them on, read the current from a current clamp and wait. I did this for my Turnigy pack without the water cooling:

http://www.youtube.com/watch?feature=player_profilepage&v=A1RY_6gMU_M

At 300 amps it would have been drained in 5 mins.

Those cells look the real deal, and if not, they sure have done their homework :)
 
jonescg said:
It's easy to discharge at stupidly high rates. Jumper leads coiled inside a bucket of water to keep them cool. Clamp them on, read the current from a current clamp and wait. I did this for my Turnigy pack without the water cooling:
Click to expand...

Thats true, but that is the equivelent of a dead short, which will give a test of burst discharge BUT will have negative effect on the cell if it is used to test capacity, and also with that you are unable to choose the C rating to which you discharge at, so will be unable to see how it performs at say 10C or 5C loads.

Your above setup is however a really simple way to test burst discharge of a cell / cell group.
 
I'm actually working on a nichrome wire load. Maybe even a bomb calorimeter to measure the efficiency :) Basically use some seriously heavy duty copper to carry the current to the nichrome wire which is able to provide enough resistance at a high enough current, consistently. I need about 10 metres of the stuff though :lol:

But yeah, you're right it gives a burst followed by a constant current that is often 2/3ds the original burst.
 
Yea, Nichcrome wire is something that can be used, dont know why i didnt think of it at the time as i use it myself lol, but like you say, to get a decent current you need a lot of it, i only have about 2 foot of it from a hairdryer i butchered. on my 2 cell tests at about 8V i could only pull 5 amps... Made a nice hand warmer though haha :)
 
Not a bad source for the Pris A123s.

Nichrome is also good for heated motorbike gear...but get the teflon coated stuff, makes life easier :mrgreen:
 
I’d like to charge the battery with solar. Below is a picture of my board that I created based on the “How to Measure Power Supply Voltages” sample from this site:
http://www.robotroom.com/Solar-Recharging-3.html
The solar panel plugs into the board. A 5v regulator brings the power down to 5v from the solar for the Arduino power. Extra power goes to charging the battery. The Arduino has a DS18b20 temperature sensor that will monitor the battery to see if it gets too warm. If so I’m going to add a relay to power off the circuit.

powersupply01.jpg
 
Here is the charge controller. I copied it from this site:
http://www.mdpub.com/555Controller/
I’m going to plug this into my solar panel supply board. I will adjust the low voltage and overvoltage settings on it to control the relay.

chargecontroller01.jpg
 
tomaj said:
Are cells from a123rc dealer genuine or fake?
Click to expand...
I don't know. I can take other pictures of it if there is something else someone would like to see to determine if it's real.
 
theRealFury said:
Discharging a single cell is not as easy as it would seem, well discharging it quickly at least. You could easily discharge one with a cheap lipo charger that also has a LiFe setting but they usually only discharge at 20-25W unless you pay $100+ for a decent one with either regenerative discharge or discharge+ feature. so at best your going to be looking at a 5-7amp discharge rate. even the element from a 1000watt space heater would only pull about 30watts from the cell at 3.3v. About best way i can think would be a high wattage, low voltage step up DC/DC converter to step it up to 12V, then you would have no problem pulling 20-30 amps out of it with the right converter.

Any more than 20-30 amps and then your looking at a lot of $$$ just for the discharger, i once watched a youtube vid of someone pulling 300amps from a single A123 20AH pouch with a massive resistor the size of beer keg, no idea where they got it from though.
Click to expand...


I dead shorted one of mine with 8 gage jumper cables and it only pulled about 200 amps. The cables got hot, the cell barely got warm.
 
BR549,

Cool project, a single cell LiFePo4 solar charger. I need a charge controller bad, but I need to go from low voltage from my solar panel to 4-8 times the voltage at the battery. Can that controller be tuned to that kind of range or do I need to come up with a voltage multiplier first? I have .5V solar cells and need to charge to an 82V cutoff, but 160 cells would be way too big for my needs, since I want it portable.
 
John in CR said:
BR549,

Cool project, a single cell LiFePo4 solar charger. I need a charge controller bad, but I need to go from low voltage from my solar panel to 4-8 times the voltage at the battery. Can that controller be tuned to that kind of range or do I need to come up with a voltage multiplier first? I have .5V solar cells and need to charge to an 82V cutoff, but 160 cells would be way too big for my needs, since I want it portable.
Click to expand...
Multiple solar panels and/or wind turbines can be connected to this unit. As you mentioned you'd have to put enough solar panels in series to come up with that much voltage. You can safely go up to 35v (the LM7805 5 volt regulator only goes up to maximum Input voltage of 35VDC). You would also need to adjust the trim pots (they work as variable voltage dividers) to your new cut off values.

I would think if you put a voltage divider in front of the LM7805 in this circuit you could drop the voltage coming in to under 35V. Then you would also need to replace the relay (mine is off my motorcycle and rated for 40 amps 12v) with one rated for over 100V (and with high enough amps to handle the max of your solar cell/wind turbine array).
Essentially you need to drop the voltage coming into the board. The relay switch handles the voltage and amps going to the batteries.

If you don't have enough panels to get up to 85v then yes, you might consider a voltage doubler to feed the circuit. I have not done one of these so if you pursue it let me know how it works. You might be able to build a portable wind turbine and with the turbine connected to the solar panels, it might get you the voltage you need and still be portable.
 
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