Cheap charging solution for AW Protected C sized LiIon cells

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jlomein

jlomein

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I am planning a ROP high built into a 2C Mag, powered by two AW C sized LiIon cells. I recently found out that although the Ultrafire WF-139 charger can be modified to touch the contacts on a C sized cell, it is not safe to charge with it.

The WF-139 has two independent charging channels that output 450mA per channel. AW states that his C sized cell (3.7v, 3300mAH) has an optimal charging rate of 2.0-2.5A.

He recommends RC type chargers called the Triton or ICE, however they are very expensive. Are there any cheaper charging solutions for these cells?
 
This page has some chargers that can charge one Li-ion cell at a time. I read a post from SilverFox saying that Lithium polymer chargers could be used for Li-ion, so I went ahead and ordered the Graupner GR6437. It says it can charge up to 3 Amps, but I have been unable to determine if you can select 2 or 2.5. I will let you know next week after I try it out.

There is also a more expensive model down the page, a Thunder Power TPC425 that has a 2.5 Amp max charge rate and can charge one cell at a time.

I think charging the C cell at 3 amps would be OK even if the charger won't do 2-2.5 Amps. Can anyone tell me what the implications would be of charging a protected Li-ion cell at 0.9C?

Oh, and these chargers all need 12V power sources, so you'll need a way to power them. I am just going to use an old computer power supply, but you could get a wall wart pretty cheap from places like Marlin P. Jones.
 
SilverFox said:
Hello Jlomein,

You may want to check out the Mastech HY1803D.

Tom
Click to expand...

Hmmm...from what I can find on Google and eBay, that appears to be a power supply of some sorts. I guess it could work as a liIon battery charger, but would not give any indication of a completed charge.

Thanks mudman cj for your suggestions as well. Some of those chargers in the link seem reasonably priced. I may give them a try. Although I do remember reading something on CPF a long time ago about a liIon charger that could do any size/shape and cost only $20.
 
Hello Jlomein,

Sorry, I thought you understood how Li-Ion charging was done with a power supply.

To charge a Li-Ion cell, you set the maximum voltage to 4.2 volts, then adjust the charge current for a rate around 0.8C. Then you connect the cell. As the charge starts, the CC light will light up indicating that it is in Constant Current mode. When the voltage gets up to 4.2 volts, the CC light goes out and the CV light lights up indicating that you are now in Constant Voltage mode.

The charge is complete when the current drops to 0.1 amps.

Oops, I just realized that you were referring to the HY1803D. It does not have the CC and CV lights. Those are on the HY3010E unit. With the HY1803D you have to read the meters. When the voltage gets up to 4.2 volts and the current starts to drop off, you have completed the CC mode and are in CV mode. You still terminate the charge when it drops below 0.1 amps.

The reason I suggested this unit is because I don't think you will be able to find a Li-Ion charger capable of 3 amps at a similar price. $60 is more than $20, but I don't believe you can find any $20 Li-Ion chargers capable of charging at 3 amps.

Tom
 
I just read a response from AW that he posted on the AW C sized cell sale thread (found here http://www.cpfmarketplace.com/mp/showpost.php?p=2033609&postcount=253 )

He states:

"the optimal charging rate for the C cell is 0.5-0.7C ( 1.6 - 2.3A )."

Under those conditions does it allow more budget charging options?

When you say you don't think there is a cheap charger is capable of 3A do you mean capable of less than 3A? Because if the cheap chargers provide only a minimum of 3A, couldn't I just stick a magnet between two C cells and charge both at once, limiting the charge rate since it is spread over two cells?
 
Last edited:
Good point. If the $30 Graupner won't charge one cell at 2.5 Amps, insisting instead to go to 3 Amps, and I decide I would rather not charge at 0.9C, I can just charge both C cells in parallel at 1.5 Amps each. You don't want to connect cells in parallel unless their open circuit voltages are near one another. IIRC the maximum voltage differential should be less than 0.1 V, but I am sure SilverFox can correct me if I am off (which I probably am - don't want to take the time to search on it).
 
Do any of these types of chargers run off household power? Most of them say they require a car battery or 12V power supply.
 
Well, that didn't work out as planned. The Graupner LiPO Charger 4 is too smart for use with Li-ion batteries. It auto-senses the battery capacity and determines the optimal charging current for the cells connected. The problem is, it doesn't sense Li-ion cell capacity properly, and won't charge a C or even a D size Li-ion cell at over 0.2 Amps. It won't charge cells in parallel any faster. If only the current could be manually selected then I think it would work OK, except it has also given me an error a couple of times when it sensed that I had connected an "incorrect" battery type. It still terminates charge at 4.2 V and reduces current near charge completion, so I can see how some LiPO chargers might work for Li-ion, just not this one.

Does anybody want to buy a slightly used LiPO charger for 1-4 cells at up to 3 Amps? :sigh:

Anyway, I have ordered a 0-15V, 0-2A adjustable power supply with digital readouts for $29.95 plus $15 shipping from here. I was really tempted to get this one that goes to 3 Amps, but didn't think I really need that extra Amp, and I don't foresee needing the higher voltage either. It is a great deal though.
 
Hello Mudman,

I believe the reason you are having difficulties with the Graupner is because of high resistance in your connections. Most of the high end chargers have this "feature..."

The recommended connection with my Schulze is welded or soldered.

Tom
 
I just got my new 20A PS from KitsUSA today.

ps-kits3.jpg


ps-kits2.jpg


ps-kits1.jpg
 
I worked with the Graupner charger but could not get it to charge a D size Li-ion at over 0.75 Amps with the exception of a few pulses that stepped up gradually to as high as 2.6 Amps for a second or two.
This charger starts out with 5 low current cycles that last about a minute and then it starts ramping up. But after it ramped up it settled back down to the 0.75 Amps which gradually decreased as the cell charged higher and higher.
I got the resistance down as far as I could without soldering directly to the cell and measured current with an inductive DC Ammeter. I took out all the extra wires, clips, and DMM I was using to measure the current and replaced them with the output wires from the charger clamped directly onto the ends of one Li-ion D cell. It definitely made a difference, so thanks again SilverFox. :wave: This charger just doesn't do what I want, and that is to charge at a rate I consider appropriate for the cells.

I give up and am ordering an HY1803D power supply instead. That will allow me to charge at up to 3 Amps.
 
Thanks for all your advice. As much as I don't feel comfortable with it, I think I will resort to buying a DC power supply. SilverFox provided excellent instructions that make me feel confident enough to use one.

I think I will search around local retailers first as online shipping isn't cheap for these heavy items. Hopefully I can find a cheap one that will output 4.2volts and up to 3 amps, along with some sort of display.
 
Hello Mudman,

Well, it looks like you have made an attempt to eliminate the extra resistance, so now I am wondering if there may be an issue with the cell itself. The Graupner sets the charge rate according to the internal resistance of the cell.

When you get your power supply, make sure you closely monitor the cell for heat. You may find that 0.75 amps is the highest rate that keeps the cell cool.

On the other hand, the Graupner is probably responding to the extra resistance of the protection circuit...

Tom
 
Hello Mudman,

How may cycles do you have on the cell?

A cell that has been in storage for an extended period of time can sometimes do strange things during the first charge. After that, things usually settle back down to "normal."

Tom
 
Hi All,

I just read through this thread again. The gist of it as far as I can tell is that there is no inexpensive, fire-and-forget solution for the charging of the AW "C" LiIon cells. Is that correct?

I'm hoping to build a Mag 2C 5761 for a friend using the new AW incan driver (if I can get one) and two of his "C" cells, but the hardest thing to line up seems to be the charger. I was ready to settle for the single-cell charger Litemania was selling, in spite of the suboptimal 1.2 amp charging rate, but the sale thread is closed now.

Maybe this difficulty is a blessing in disguise, considering the potential safety issues with charging LiIon cells, especially ones as big as the "C" cells...

If anyone has any thoughts, I'm all ears. Thanks!

-Rick
 
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