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Old Jan 18, 2013, 03:03 PM
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Austin, TX
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JIm.
I had asked the Techs at XPS for help and they sent me this on Oct. 30, 2012.
Quote:
. We run multiple batteries in parallel (connected at each end of the receiver bus, even if a Y cable was necessary).

For example, in our 50% Yak 55 we have four A123 packs. Two sets of packs are wired in parallel. This gives us 4600mAh (2 x 2300mAh) per set, for a total of 9200mAh of capacity. One set is plugged into the BATTERY port on the receiver and the other set is plugged into the last channel. We do NOT use switches. To turn on the system, all 4 packs have to be plugged in. We do this by having a permanent connection at the receiver, and the A123 packs plug into our parallel harness individually.

Having the connections at each end of the bus evenly distribute the load across the bus and gives us redundancy. If one set fails (due to wiring or battery issues) the other set will still fly the plane without any problems.
Unquote.
I have it set up that way.
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Old Jan 18, 2013, 03:32 PM
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you could still do it that way, but the soldering taps would be a superior form of connection than anything using servo plugs...
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Old Jan 18, 2013, 03:45 PM
Xtreme Power Systems
Lake Havasu, AZ
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Correct. This is because you are not going through a servo pin, which is what will limit the current capability. A soldered pad is good for >10x the current capability compared to a single servo pin.
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Old Jan 18, 2013, 04:36 PM
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Launceston Arpt, Tasmania, Australia
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Quote:
Originally Posted by JimDrew View Post
Correct. This is because you are not going through a servo pin, which is what will limit the current capability. A soldered pad is good for >10x the current capability compared to a single servo pin.
I would say that the female part of the connector is the limiting factor, as it is
thinner material and must retain it's tension on the pin, said tension gradually disappears as the material heats up. so it is not actually the pin itself that is the limiting factor. To be correct say " individual connection mating is limited to 5 A".
Am I being pedantic or what? Please, not too many replies back on the "what"
bit, my ego would not survive it.
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Old Jan 18, 2013, 05:48 PM
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Originally Posted by E_ferret View Post
I would say that the female part of the connector is the limiting factor, as it is
thinner material and must retain it's tension on the pin, said tension gradually disappears as the material heats up. so it is not actually the pin itself that is the limiting factor. To be correct say " individual connection mating is limited to 5 A".
Am I being pedantic or what? Please, not too many replies back on the "what"
bit, my ego would not survive it.
J'accuse! Sesquipedalian!
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Old Jan 18, 2013, 06:30 PM
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Quote:
Originally Posted by AlanDY View Post
I had asked the Techs at XPS for help and they sent me this on Oct. 30, 2012.
Quote:
. We run multiple batteries in parallel (connected at each end of the receiver bus, even if a Y cable was necessary).

For example, in our 50% Yak 55 we have four A123 packs. Two sets of packs are wired in parallel. This gives us 4600mAh (2 x 2300mAh) per set, for a total of 9200mAh of capacity. One set is plugged into the BATTERY port on the receiver and the other set is plugged into the last channel. We do NOT use switches. To turn on the system, all 4 packs have to be plugged in. We do this by having a permanent connection at the receiver, and the A123 packs plug into our parallel harness individually.

Having the connections at each end of the bus evenly distribute the load across the bus and gives us redundancy. If one set fails (due to wiring or battery issues) the other set will still fly the plane without any problems.
Unquote.
I have it set up that way.
Bad advice. A123 (2300) cells may fail shorted. If a single cell fails, all is lost. If you want redundancy, you need to have a diode in-line of each pack, or some other means of preventing one pack draining the other.
Sharing load on two connectors makes sense. Doing this by using Y-cable does not, if we are talking about servo type connectors. There will be even more connectors involved. There should be no need to power a bus from both sides, as voltage drop along the bus should be low, especially if it is rated 30-60A.

Anyway, the best thing is wires soldered directly to the pads with heavy duty connectors to the batteries.

Fred
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Old Jan 18, 2013, 08:20 PM
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I am more confused than ever. Do it this way, No don't do it that way. How am I going to connect two pairs of A-123 Batteries to one input? Please, no Hi Tec answers just a practical explanation.
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Old Jan 18, 2013, 08:21 PM
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I used four batteries because I have four very large servos, not for redundancy.
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Old Jan 18, 2013, 08:24 PM
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just make some parallel Y harnesses...
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Old Jan 19, 2013, 12:42 AM
Xtreme Power Systems
Lake Havasu, AZ
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Originally Posted by flarssen View Post
Bad advice. A123 (2300) cells may fail shorted. If a single cell fails, all is lost. If you want redundancy, you need to have a diode in-line of each pack, or some other means of preventing one pack draining the other.
Sharing load on two connectors makes sense. Doing this by using Y-cable does not, if we are talking about servo type connectors. There will be even more connectors involved. There should be no need to power a bus from both sides, as voltage drop along the bus should be low, especially if it is rated 30-60A.

Anyway, the best thing is wires soldered directly to the pads with heavy duty connectors to the batteries.

Fred
We sold THOUSANDS of A123 packs. Out of the hand full of failures we did get, NONE were shorted closed circuit. ALL were open circuit. Not surprising, these batteries can start your car - so they would burn through any short circuit condition.
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Old Jan 19, 2013, 04:24 AM
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Quote:
Originally Posted by AlanDY View Post
I used four batteries because I have four very large servos, not for redundancy.
in that case the ultimate power solution is to connect one battery directly to each servo, bypassing the receiver connection.
you still need to have a connection from the receiver to each servo passing the ground and the signal wires only, not the positive. actually, you can leave the positive in, you then have each positive feeding the receiver, should be enough amperage to drive that power hungry receiver.
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Old Jan 19, 2013, 10:04 AM
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Originally Posted by JimDrew View Post
We sold THOUSANDS of A123 packs. Out of the hand full of failures we did get, NONE were shorted closed circuit. ALL were open circuit. Not surprising, these batteries can start your car - so they would burn through any short circuit condition.
Ya agreed A123 packs are awesome.
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Old Jan 19, 2013, 12:17 PM
PGR
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Originally Posted by JimDrew View Post
We sold THOUSANDS of A123 packs. Out of the hand full of failures we did get, NONE were shorted closed circuit. ALL were open circuit.
My experience with A123 cells hasn't been good. I've never used them in RC applications but the four DeWALT XRP Nano battery packs I owned all were populated with the 18650 cells.

I got those four Nano packs with new tools I purchased and all four packs died on me in less than a year. In every case they died because a single cell or pair of paralleled cells opened up. Ironically, all four of my DeWALT XRP NiMH packs (which were already well-used before I got my first XRP Nano packs) are still going strong and showing no signs of wearing out.

And let me be real clear about something: I don't abuse my cordless tool packs. The moment they show any sign of running out of energy I exchange 'em with charged packs, and I only used the DeWALT DC9310 NiCd/NiMH/Li-Ion chargers that came with the tools to charge them.

This is irrelevant to the discussion, but the only DeWALT cordless tools I still use are my 1/2 gallon and 2 gallon cordless vacuums. I either sold or retired the rest of my DeWALT cordless tools and replaced them with Makita 18V LXT tools. The reason actually has little to do with battery issues, though: I just think the DeWALT tools are too bulky and too heavy and I can't seem to detect any benefit to the additional bulk and weight.

I'll add that I don't even know what cells Makita is using in their LXT battery packs, but I've never had one fail or wear out and some of mine are close to 3 years old.

Pete
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Old Jan 19, 2013, 12:25 PM
Xtreme Power Systems
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It's pretty well known fact DeWalt's charger used for the Nano cells was based on their Nimh charger and didn't work well, and there was no balancing of the cells at all.
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Old Jan 19, 2013, 12:55 PM
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Originally Posted by PGR View Post
I got those four Nano packs with new tools I purchased and all four packs died on me in less than a year. In every case they died because a single cell or pair of paralleled cells opened up.
Yes, the 18650 cells usually fails open.
The 36V packs with 26650 cells I have opened, included a battery management module. Really strange if they omitted this on the other types of packs, Maybe it didn't work properly?
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