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May 31, 2004, 12:08 PM
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Multiplex 6-pole plugs adapted to charge LiPos

This thread is dedicated to luc, who I think first disclosed the use of Multiplex 6-pole plugs for parallel charging and series discharging LiPo packs.


R1 = Red lead, cell #1; B1 = Black lead, cell #1.
R2 = Red lead, cell #2; B2 = Black lead, cell #2.
R3 = Red lead, cell #3; B3 = Black lead, cell #3.

ON THE MALE CHARGER PLUG (two pairs of 3 solder lugs bent together):

RC = Red lead to charger; BC = Black lead to charger.

ON THE MALE PLUG TO THE ESC (two center pairs of lugs bent together):

Resc = Red lead to the esc; Besc = Black lead to the esc.

The bent-together lugs will attract a solder bridge and electrically connect the lugs without needing a wire between them.

Pot the soldered plug ends with goop; see finished charger plug, which also shows a parallel pair of plugs for charging two LiPo packs at the same time:

Lipo cells charged in parallel donít have to be the same capacity, but should be within a half-volt or so when connected together.

IMO, this system is so economical, foolproof and safe that it wonít be long before some enterprising LiPo manufacturer starts offering a complete system, including an injection-molded female plug fit to the end of eack pack, a 4.2 volt charger with capacity-sensing amperage control and a charging plug, and a plug for the esc, with the connections disclosed here molded into each plug.

- RD
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May 31, 2004, 03:42 PM
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RD, I was going to post a message to you here saying to never give up the battle. Then I realized that it was not necessary!

Your dogged determination to promote Li safety through the concept of Keep It Simple is legendary on this forum. Kudos to luc for pioneering the concept, and to you for keeping it in the public eye. The 4.2V charger would be nice. But, as you well know, for all those who are charging Li cells with a variable voltage/current power supply, this parallel charge/series discharge wiring system can be easily implemented today.
May 31, 2004, 09:34 PM
Registered User
Thanks for your encouragement, Dave.

Quite a few folks have posted, in many threads through the last 18 months or so, that they charge LiPo cells in their packs individually or in parallel, with series discharging.

It does require more connections, though, and luc and I (and others) have tried to simplify that, as much as possible.

But making those extra connections is only needed once - at the time of the construction of the pack and three plugs. After that, only two wires emerge from the charger and ESC plugs, same as now.

The situation is ideal for a LiPo pack manufacturer to take over construction of this pack and plugs. A low-cost system offered with the right charger, and it's safe Plug-and-play for newbies. That's what I'm trying to promote now.

You are quite right that the system will work with currently available components, but overcharging is possible without a dedicated, 6.4 volt charger and connection mistakes are possible without correctly wired, six-pole polarized plugs for a 3s pack.

Luc's posting of the Multiplex plug really helped.

If manufacturers develop the concept, I'm sure higher amperage plugs and chargers will appear, for high-powered packs

Thanks again.

- RD
Last edited by RD Blakeslee; May 31, 2004 at 09:37 PM.
Jun 01, 2004, 05:49 AM
veni,vidi, roto volubilis
Happy|Harry's Avatar
i'll be another to add support for your efforts RD, right from the get go you've reccomended paralell charging
and without doubt it is the safest option bar none!, also this connection method is one of the simplest ways to
impliment it i've seen to date. i just wish there were higher rated plugs of this type available for higher output
packs, but like you say hopefully one of the li manufacturers will take up the mantle and make them available

Jun 01, 2004, 11:45 AM
Registered User
Modular Anderson Powerpoles have interlocking tabs that allow them to be ganged together in clusters of 6, and are available in ratings up to 180A.
Jun 01, 2004, 05:16 PM
Registered User
Originally Posted by Happy|Harry
i'll be another to add support for your efforts RD ... i just wish there were higher rated plugs of this type available for higher output packs, but like you say hopefully one of the li manufacturers will take up the mantle and make them available

Thanks, phil

Charlie Wang, maybe?

- RD
Jun 01, 2004, 05:24 PM
Registered User
Dave, re your observation about getting along with current hardware, luc has observed that typical LiPo chargers can be used to partially charge a pack in series (up to 4 volts or so) through an plug wired for an ESC, then switch to charging through a parallel plug for filling the cells safely. That would speed up charging with low amperage chargers.

- RD
Jun 02, 2004, 03:54 PM
Registered User

Dave H,

Great observation about the AP connectors.....the standard connectors that most of us use are rated for 30 amps (I push them past 50) would be a great parallel-charge/series-run "system"

Obviously you want to mount the battery-plug as close to the pack as possible. 6 strands of 14gauge wire adds up.....the ESC-side only needs the usual 2.

The benifits are big with a reliable p-charge system over the standard s-charge systems.

Some concerns need to be quantified (in comparison to like-amp 2-connector systems):
1) Cost-penalty for a connector-block (most likely $1-$2) pack configuration
2) Weight penalty.
3) Connector-loss penalty. Connector resistance is usually the higher R in the wire-battery-connector chain. Multiply that by 3 and total resistance may be of considerable concern. Especially when dealing with higher-amp loads which today's modelers demand. 2-connectors disipate heat much better than a snug 6-connector block. The accumulated voltage drop is not cool either.
4) MTBF of a battery 6-connector system vs a standard 2-connector system. This is going to be impossible to nail down, and is probably neglegable. Connectors do fail, although I have never had a connector fail in flight yet.

One risk that does have me concerned is the integrety of the block itself. I mentioned before that I have never had a connector fail in the air. I have had them fail when connecting them together to fly or charge though. With a 2-wire AP plug it is easy to spot a failed connection. It is a little more difficult with a 6-connector system, especially on the "charge" configuration. During charging if you have one of the connectors break loose (solder, metal failure, or case breakage), it would be much easier to miss. The pack will still charge 2 of the 3 cells.....thus putting 1.5 times the inteded amp-charge-rate into the 2 remaining cells. This may not be to big a deal during charging (over-voltage will not ocur). The damage is done during discharge, in that the weak cell will be way out of balance. The block needs to be assembled with quality components and with precision. A good start to achieving this is a one-piece integrated unit that is specific to the application. A locking Astro-Flight type 6-pole system would be something that one should strive to achieve.

Last edited by pullin-gs; Jun 02, 2004 at 04:06 PM.
Jun 02, 2004, 06:28 PM
Registered User
Good points on the multi-connectors, Pullin'. The more you look at it, the more you realize that there is no perfect solution, with each one carrying its own baggage.

Personally, I believe the ultimate solution is to produce Li cells that are not subject to thermal runaway. Then the imperfect add-on safety devices are no longer needed. Saphions are already available, but they can't match the performance of the best Li cells. Maybe they never will. But if a reasonably good performing Li cell with benign chemistry excluding cobalt-oxide cathode material becomes available, all but those looking for the absolute highest performance would no doubt choose the safer cell.
Jun 02, 2004, 07:55 PM
Registered User
Originally Posted by pullin-gs
... The block needs to be assembled with quality components and with precision. A good start to achieving this is a one-piece integrated unit that is specific to the application. A locking Astro-Flight type 6-pole system would be something that one should strive to achieve.


Will Charlie Wang make one for us? I'm waiting to hear- see post #6.

- RD
Jun 03, 2004, 10:50 AM
I plant balsa sticks too
luc's Avatar
Just saw your post now,...thx for the nice words.
In fact , these mpx plugs are widely used in europe (germany in fact more than anywhere else). Graupner just released red ones which are exactly similar and compatible (but red).
You can efectively separate the 6 poles for charging, each pole being able to stand 15A, more than any charger can do.
For discharge, I use 2 packs of 3 poles, which can support together the 45A .
These plugs can't disconnect themselves (unless the pack leaves its position) but can be opened easily by hand.
Yep, for charging, start in serie and end the charge in //. You can even charge them full in serie, disconnect and put the multiplug in // without charging; all the packs will automatically auto-balance themselves.
Here are 2P 2600 packs with multiplugs in serie and //.
I like this system as it balances automatically; same packs can be used in different sized applications (3S,4S,5S,....) In case of a crash you don't ruin an expensive 3S4P pack or so. Packs are stuck together thru velcro (one side is sticky on the battery)
Jun 18, 2004, 06:19 AM
Registered User
An slightly safer variant, which also helps overcome the higher amperage requirement of individual or parallel cell charging, would be to leave the charger plug "straight through", i.e., don't solder the lugs together as shown. Attach a separate, small charger to each pair of charger lugs. That would be three chargers for the 3s plug shown. Three Apache 2600s would charge a 2600mah 3-cell pack at C.

It's a little safer, in that if any cell went open, the other two wouldn't get a 1.5 C charge rate, which they would if all three cells were charged in parallel.

- RD
Aug 15, 2004, 05:06 AM
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Last edited by RD Blakeslee; Aug 16, 2004 at 07:40 AM. Reason: Info already in post #1
Aug 17, 2004, 07:54 AM
Bubble Head SSN 762
LexTalionis's Avatar
Pleasure reading this thread...I can't begin to sum up all of the "tribal-knowlege" and information I have found on this forum.

Would it be possible to someone to do up a Viso Electrical diagram of these two concepts? Even a hand-written and scaned version would work too.

Aug 17, 2004, 08:12 AM
Registered User
If nobody gets to it before I do, I'll post a scanned sketch for you this evening, Lex.

- RD

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