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HomeAircraftHelicopterMain Discussion › Why do lipo chargers balance a pack? that is so dumb...
04-07-2010 07:04 PM  8 years agoPost 41
jackheli

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Vancouver - Canada

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They still share the common ground.
You are mistaken, sir. Check your schematics knowledge.
You will see the voltage exactly as he stated, even though you effectively move electrons in an isolated fashion when balancing.

And in the end that's all we care about.
Electrons...

It's easy to find an excuse to do wrong. Hard is not to find an excuse to do right.

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04-07-2010 09:17 PM  8 years agoPost 42
aceisback

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Terre Haute, IN

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With the correct circuitry, you can charge the individual cells using an individual charger for each cell (Look at the previous schematic). This is how the chargers that do charge through the balance port work using independent charge circuits for each cell. The problem of charge current remains due to the wire and connector size. It doesn't matter if you have an individual charger or multi-charger as the results would be the same and have the same limitations.

I can't speak for every charger designed, but I do know that some charger circuits charge through the main +/- plugs and monitor voltage for each cell at the balancer and supply a top-off charge independently to each cell to boost each cell so they match as close as possible.

If you have cell phones or other devices that use USB based charging or have batteries with the charge monitor circuit built in to the battery, you notice they get hot and even hotter if left charging. Our LiPo's don't get hot like that when properly charged. Big difference in basic charger vs. smart chargers.

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04-07-2010 09:40 PM  8 years agoPost 43
jackheli

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The idea of topping off a single cell through the balancing connector makes perfect sense, although you would need all what a generic lipo charger brings plus the extra circuitry and software to charge from both the discharge and balancing connectors. Price could be a factor.

It's easy to find an excuse to do wrong. Hard is not to find an excuse to do right.

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04-07-2010 09:45 PM  8 years agoPost 44
aceisback

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Price would definitely be a factor. Even mass producing such an item would be more costly thus the final product cost would be outrageous with the typical cost markups.

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04-07-2010 11:01 PM  8 years agoPost 45
Aaron29

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Just get the voltage from the previous tap and not always from the first tap.

Each cell has a wire in the balancer connector for each of it poles. You can isolate each cell as you please.
I think I see what you mean now. In the first diagram, are you suggesting using the white wire to act as the ground for the first cell instead of going through subsequent cell?

I suppose I can see that.

So in the end thicker wiring is all you'd need?

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04-07-2010 11:49 PM  8 years agoPost 46
Aaron29

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But then are we only able to charge one cell at a time if we do it independently?

Help me understand how you can charge through the balance lead with separate simple chargers.

Wouldn't you effectively HAVE to have a complex system in order to maintain the voltage potentials across each cell?

In other words, for that first diagram 2 cell system, the white wire would be acting as the ground for the first cell while simultaneously acting as the positive lead for the second cell. How then would you make that work with 2 separate chargers? Getting the voltage potential to be correct across each cell would require something that a couple 15 dollar chargers just don't have.

I think it is complex because it has to be, unless of course you disconnect the cells from one another prior to charging.

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04-08-2010 12:02 AM  8 years agoPost 47
jackheli

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The idea aceisback proposed was to do the heavy duty charging with high current from the discharge connector if the pack is balanced. If not, charging would take place at first with independent single cell chargers (one charge for each cell in the pack) until they are all balanced.

The chargers that charge through the discharge connector and the chargers that charge through the balancer connector would be totally independent and would not operate at the same time, in principle.

It's easy to find an excuse to do wrong. Hard is not to find an excuse to do right.

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04-08-2010 12:07 AM  8 years agoPost 48
Aaron29

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Why go through all that trouble of having the heavy duty charger if you can just use the balance lead, then?

Assuming you beefed up the wiring, of course.

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04-08-2010 12:39 AM  8 years agoPost 49
aceisback

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This is the basic theory of using multiple chargers with a 2 cell setup but it would just cascade for each additional cell. There is more to it but this is the basic design.

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04-08-2010 12:40 AM  8 years agoPost 50
Aaron29

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Sweet drawing.

So then I see only 2 obstacles.

First, we need to beef up the wiring in the balance lead. Wouldn't even need to call it a balance lead anymore as it really would be individual charge leads.

Not sure if anyone is up to cutting open a LiPo and soldiering thicker guage wire onto the terminals. Seems a bit "brave" if you ask me and could be expensive if you damage the battery. Could also be dangerous. We might need to cater to the manufacturers for this change.

The second obstacle is the individual chargers need to have at least rudimentary monitoring. Most people would not trust the wall wart lipo chargers to do the job.

I would prefer a readout of volts (down to the hundredth), amps, and milliamps delivered. Time would be nice.

No idiot lights or lack of monitoring. Not for a 300 dollar battery anyway. Or not mine, I should say. I guess you could just slap it on a simple charger and put a voltmeter on it when done. I'd like to know how at LEAST how many milliamps went in so I can continue to check the 80% rule.

Are there any single cell chargers on the market that offer monitoring? At the bare minimum, milliamps delivered.

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04-08-2010 01:00 AM  8 years agoPost 51
Furious Predator

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Kitchener, Ontario, Canada

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from what i understand, the old Thunderpower 1010 charger with its corresponding balancer, charge through the balance connector. this has been around for quite a while...

Shawn
Team Leisure-Tech
Team HelixRC

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04-08-2010 01:01 AM  8 years agoPost 52
Aaron29

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USA

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Well the idea is to do it with cheap chargers.

If there is an el cheapo 1 cell charger out there that has rudimentary monitoring it could work.

Of course by the time you buy 12 of them for a 12S setup you've bought a nice charger.

I see this working mostly for 3 to 4 cell systems as the idea is to keep cost down.

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04-08-2010 01:08 AM  8 years agoPost 53
aceisback

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Terre Haute, IN

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All I was able to find were 1 cell lipo charger bare boards, and they were $19 each back in Dec. when I was researching this.

There are some dedicated IC's for chargeing LiPo's:

- MAX1555
- MAX1811
- STC4054
- LM3420
- MCP7384

Don't remember much in the way of circuit details though. Output current would probably still be an issue.

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04-08-2010 01:20 AM  8 years agoPost 54
Aaron29

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USA

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- MAX1555 (280ma crazy slow)
- MAX1811 (500ma, this is getting there, you could charge a 3 cell 2200mah lipo at about .7C with three of these. Still slow.)
- STC4054 (800ma, now you're talking, you could charge a 3 cell 2200mah lipo at about 1.1C with three of these)
- LM3420 (20ma, oh boy, INSANE slow)
- MCP7384 (couldn't find it.)

So what's a STC4054 cost. Couldn't find it.

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04-08-2010 01:21 AM  8 years agoPost 55
Aaron29

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were $19 each
I just don't see that being worth it. It'd cost me 60 bucks to get a simple charger for a three cell.

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04-08-2010 01:36 AM  8 years agoPost 56
Terrabit

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Seattle, WA - USA

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I think a reasonable assumption would be that when such a device becomes practical, one of the many qualified electromechanical engineers tasked with the purpose will work out the details. That's how this sort of stuff works. When demand justifies the commitment of various resources, supply will follow.

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04-08-2010 01:36 AM  8 years agoPost 57
Terrabit

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Christ Aaron, you tryin to make Professor today or what? I'm going to lmao if you pass 20 posts today.

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04-08-2010 01:37 AM  8 years agoPost 58
Terrabit

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It's all good. It's just kinda funny that's all.

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04-08-2010 01:37 AM  8 years agoPost 59
Terrabit

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04-08-2010 01:39 AM  8 years agoPost 60
Aaron29

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USA

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That's 4 for you right there...

Oh and I just checked a couple profiles...

Aaron29...1.42 posts per day.

Terrabit, 3.11 posts per day.

Who's the blabbermouth now?

(I just get it all of my chest and then you don't hear from me for a while.)

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HomeAircraftHelicopterMain Discussion › Why do lipo chargers balance a pack? that is so dumb...
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