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Nov 19, 2006, 10:41 AM
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Dan Baldwin's Avatar
Quote:
Originally Posted by rick.benjamin
Another "Dan" is posting.
schematic came from post 438 https://www.rcgroups.com/forums/show...&postcount=438
by Dan Ranc https://www.rcgroups.com/forums/member.php?u=103924 "Flying Dan"
Yes, I found that post. My concern is the the caption on the schematic attachment reads "electronhead charger with Baldwin balancer" which makes it sound like my balancer was added to the electronhead charger, and that is not the case.

Dan
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Nov 27, 2006, 01:31 AM
Hi folks,

You're all correct:
- Dan, sorry for the misleading schematic caption; the post itself correctly states that the schema is "based" on your ideas, and invites urgently the reader to study your original posts.
- yes Harry, the 1 ohm resistor is an attempt at limiting current in case of shortcut.
- I am puzzled by Harry's remark on the schema (bug in the second regulator), since I am using this design daily for some months now. I'll rapidly check this point.

Cheers,

Dan
Dec 13, 2006, 08:17 AM
Registered User
This is my first charger with balancer for Dual Sky 620mAh but I only need to charge at 600 mA .So my R1 = 1.25/600mA = 2.08333 Ohm

It works fine

Thanks for all
Last edited by catflying; Jun 05, 2007 at 01:04 AM.
Dec 15, 2006, 04:50 PM
Looks good Cat. Nice work

Jay
Dec 20, 2006, 12:02 PM
Registered User
Jay,

I have a question about the balancer that Catflying just made. The original Q2 was a Tip3055 - 15Amp capability. Catflying's Q2 is SC9013 - 600ma capability. Must Q2 be able to handle the full amperage of the LIPO pack you are charging, or just a percentage of the pack ? I'm charging 1300 mah packs so I'll need to find a Q2 replacement.

Catflying, how's the balancer working ?

Thanks for your help.
Dec 20, 2006, 02:48 PM
Don L.
Quote:
Originally Posted by SkyCobra
Jay,

I have a question about the balancer that Catflying just made. The original Q2 was a Tip3055 - 15Amp capability. Catflying's Q2 is SC9013 - 600ma capability. Must Q2 be able to handle the full amperage of the LIPO pack you are charging, or just a percentage of the pack ? I'm charging 1300 mah packs so I'll need to find a Q2 replacement.

Catflying, how's the balancer working ?

Thanks for your help.
I'm not Cat, but I think I can answer your question. The resistor in series with Q2 limits the current through Q2 to a little over 100ma.
Dec 20, 2006, 03:23 PM
Registered User
Tr2 is used to connect the 39 ohm resistor across the battery...assuming it is fully conductive then there should be little dissipation in the device...

So applying the resistor across the cell..voltage of 4.22v divided by 39 ohms will give the current flowing.. it is this value that the transistor needs to handle....then go 50% higher to give safe margin...
Dec 20, 2006, 05:21 PM
Registered User
Thanks for the quick replies ! Now another silly question - Can I use this balancer as standalone, without the charger ? I believe it "bleeds-off" the high side to low side. This will leave the battery in a "not topped off" condition but that's OK.

Thanks
Dec 20, 2006, 05:34 PM
Registered User
Essentially delete everything associated with the 2 LM317s...

That will leave you with a balancer system for a 3s pack...

The balancer is basically an electronic load....if a cell is above a preset level, the load discharges the cell until a preset voltage is reached, once reached, the load is inactive...hence the balancing effecting...its as good as the tolerance of the components used....
Dec 20, 2006, 08:24 PM
Registered User
That's awesome ! thanks Chippie for the verification.

Now to find a Q2 that will handle 150ma and I'll start ordering parts.
Dec 21, 2006, 02:20 AM
Registered User
Quote:
Originally Posted by SkyCobra
That's awesome ! thanks Chippie for the verification.

Now to find a Q2 that will handle 150ma and I'll start ordering parts.

well I'm sure its right....Some tell me if I got it wrong quickly before SkyC burns his packs.....


A heatsink would be a good idea too on the transistor even as a precaution..
Dec 21, 2006, 11:08 AM
Registered User
Dan Baldwin's Avatar
Most of the commercially available balancers can be used without a charger to balance a pack even if it's not fully charged, but the balancers shown in post #498 are only intended to balance the pack while being charged. If all cells are less then 4.2 volts (which they should always be when not being charged), the balancers are inactive, although they will still draw a little power from the pack, so they will discharge the pack if left connected for an extended period of time.

Dan
Dec 21, 2006, 01:17 PM
Registered User
Dan,

I was hoping to use the balancer in standalone mode, but now I'll just add it to the charger board. Thanks for setting me straight.

I know it's not your charger, but could I replace the Q2 transistor with a PN2222ATAR ? It can handle 1A .

Ron
Dec 21, 2006, 03:37 PM
Registered User
Dan Baldwin's Avatar
You could probably use a PN2222ATAR in place of the 2SC9013. Just remember that the T0-92 transistors get very hot if you try to dissipate much power with them.

Dan
Dec 26, 2006, 06:15 PM
N36078 '41 BC-12-65
taylorcraft078's Avatar
Quote:
Originally Posted by catflying
This is my first charger with balancer for Dual Sky 620mAh but I only need to charge at 600 mA .So my R1 = 1.25/600mA = 2.08333 Ohm

It works fine
Looks like a nice, simple design. If I wanted to charge only 2 cell packs it looks like I could build it without the cell 3 circuit and call the - line on cell 2 ground. Is this correct?

My target packs are 2 cell 800 mah.

Dave


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