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Sep 02, 2004, 06:59 PM
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Larry3215's Avatar
Those are all good points. With Polyquest you would make up a single conector and be done with it.

I was thinking of all my Tanic and homemade packs with JST taps.

I like that there are so many new good options coming onto the scene!

Larry
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Sep 05, 2004, 01:54 AM
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dowd's Avatar
Although it was designed as a balancer, it seems that if you set the cutoff on this circuit for 8.4 volts instead of 4.2, you could use it in parallel with your 2-cell pack and you could charge off of a regular nicad variable current charger. Might be a nice use of one of those old unneeded nicad chargers to get a lipoly variable current charger. Prob'ly be better if you turn down the current once the LED comes on though.

Dowd
Sep 06, 2004, 04:49 PM
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Dan Baldwin's Avatar
The first one of these I built was for my brother, and it is set at 8.4 volts so he can use it with his hitec cg340 charger to charge his lipolys at any rate he wants. Yes, you can turn down the current so that the LED just stays on to keep the heat to a minimum. He also has a 12 volt light bulb he can use as a current limiter instead of the CG340.

Dan
Sep 08, 2004, 02:24 AM
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Larry3215's Avatar
Dan

I am haveing trouble finding all the parts at Digikey.

The TIP137 and MFR185 do not come up on a search.

Do you have a part number for the LED as well?

Also is the TO-92 type ok?

Thanks!

Larry
Last edited by Larry3215; Sep 08, 2004 at 02:29 AM.
Sep 08, 2004, 02:27 AM
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Larry3215's Avatar
Also, I am assuming 1/4 watt resistors?
Anything special needed for the cap?

I want to build 3 of these and get them tested

Thanks!

Larry
Sep 08, 2004, 10:33 AM
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Dan Baldwin's Avatar
I bought most of the parts from Mouser, so I have included the part numbers from my purchasing. I've noticed that the Mouser search doesn't seem to work right recently. I have had trouble finding some parts too. 1/4 watt resistors will be fine. I suggest putting a 1 ohm current limiting resistor in between the collector of the TIP137 and the MFR185. That resistor will need to be a larger, perhaps 2 watts. The transistor that is used to turn on the LED isn't critical. I actually used the PNP tansistor shown below. If you don't anticipate large balancing currents, you can use small screw on TO-220 heat sinks as shown below. You can use any LEDs you want. I use super bright LEDs because they're nifty. If you want REALLY nifty, you could use blue or white LEDs, but they're a lot more money. Make sure that you check proper operation of the balancers, and calibrate them to 4.2 volts BEFORE you hook them to the batteries. There is nothing critical about the capacitor. I chose these particular pots because they are 1) inexpensive, and 2)tamper resistant. It takes a small allen wrench to adjust them. Mouser shows that all the parts listed below are in stock.

Dan

511-TIP137 PNP POWER DARLINGTONS .68
531-PT10MH-1K 1K OHM POT .40
604-L934SGC T-1 GRN 300 MCD 50 DEG SUP BRITE LED .18
511-TL431ACZ ADJUSTABLE SHUNT REGULATOR .28
511-2N3906 PNP GENERAL PURPOSE SIGNAL XISTOR .06
567-290-1AB T0-220 HEAT SINK .38
Last edited by Dan Baldwin; Sep 17, 2004 at 09:15 AM.
Sep 08, 2004, 11:35 AM
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Larry3215's Avatar
I just ordered enough parts to build 9 balancers. Thats the most I would ever use at one time. They should be here this weekend. Ill put a few together and test em out.

Thanks Dan!

Larry
Sep 08, 2004, 11:58 AM
Registered User
Dan Baldwin's Avatar

screw up alert


Then you won't be happy that I found a couple of little problems. I had made a few changes that I didn't think would have any bad effects on the circuit that I published, but I was wrong. A couple of changes need to be made. You will need to change the value of a resistor (120 ohms instead of 330 ohms) and add a couple of capacitors. 1 .1 mfd and 1 2.2 mfd. Those changes seem to work fine, but I'll really wring it out later today.

Sorry.

Dan

EDIT
Schematic changed
Last edited by Dan Baldwin; Sep 08, 2004 at 03:59 PM.
Sep 08, 2004, 12:05 PM
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Larry3215's Avatar
No biggie. They are additions, so I didnt order anything I dont need.
Should I wait till you do some more testing?

larry
Sep 08, 2004, 02:20 PM
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Dan Baldwin's Avatar
Good idea. I'll work it over later this afternoon.

Dan
Sep 08, 2004, 04:13 PM
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Dan Baldwin's Avatar
I was having problems with oscillation, but the scematic shown above (I changed it again) is stable.


Dan
Sep 08, 2004, 05:45 PM
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Larry3215's Avatar
This is the one to go with then?

Not bad, you added 2 caps and one resistor and changed one it looks like.

Should add less than a buck to the cost.

I should have parts by the weekend and will get some built and tested and report back.

Larry
Sep 08, 2004, 06:07 PM
Registered User
Dan Baldwin's Avatar
yup, that otta do it.

BTW $5.00/cell? I come up with more like $3.00/cell. Of course that's not including printed circuit board.

Dan
Sep 09, 2004, 01:57 AM
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Larry3215's Avatar
OK then, show me your list an I'll show ya mine

My wife says I the best over spender she has ever married

I would not mind saveing $200 per.

Larry

Larry
Sep 09, 2004, 09:55 AM
Registered User
Dan Baldwin's Avatar
Okay, we have a beer on this, right? You've seen the list above;

511-TIP137 PNP POWER DARLINGTONS .68
531-PT10MH-1K 1K OHM POT .40
604-L934SGC T-1 GRN 300 MCD 50 DEG SUP BRITE LED .18
511-TL431ACZ ADJUSTABLE SHUNT REGULATOR .28
511-2N3906 PNP GENERAL PURPOSE SIGNAL XISTOR .06
567-290-1AB T0-220 HEAT SINK .38

Those parts add up to $2.01. Additionally you need;
6 misc resistors @ .05ea .30
1 100 mfd cap 75-516D107M035 .28
1 .01 mfd cap 581-BF014D0103K .09
1 .1 mfd cap 581-BF014D0104K .11
1 1 ohm 3 watt 72-RWM410-1-5 .32
Mouser shows that all parts are in stock

For a grand total of $3.11/cell. Did I miss anything?

I can probably save that additional $.11 if you make me.

Dan
Last edited by Dan Baldwin; Sep 17, 2004 at 09:17 AM.


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