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Power Expander w/FS and A123

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Old 07-20-2008, 02:20 PM
  #1
RCAddiction
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Default Power Expander w/FS and A123

I'm equipping a 75cc Aeroworks Extra (DA85) with (2) 2300 A123's for the radio, along with JR balance taps for charging. I am trying to determine the overall power and switching system. Hitec 5955 or 7955's with a FASST receiver will be used so I need the servo signal voltage boost. The Power Expander Pro with optional failsafe pin/flag switch seems like a good option. Another option is a Wolverine switch between the batteries and the Power Expander Sport.

PE Pro - the (2) A123's will be set up with a Deans output and a 3 wire JR balancing connector for charging the cells with an FMA Cellpro 4S through Ernst jacks on the side of the fuse. The charge connectors on the Power Expander Pro, therefore will not be employed at all. The 2S batteries will always be connected to the PE via the Dean's connectors except during the off-season.

Questions:

Using the failsafe switch setup for power on/off, is there any problem with balance charging the A123's thru the 3 conductor JR balancing connectors?

The "Flight Packs" page on the Smart-Fly website doesn't show any A123 packages. Everything shows a regulator. Your recommendations for A123 packages, along with the discounts would make it easier/faster/slightly cheaper. So, this is both a suggestion as well as a request for your recommendation for an overall package suitably sized for my plane.

thanks!



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Old 07-20-2008, 02:36 PM
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Default RE: Power Expander w/FS and A123

Hi,
Please see below for answers to your questions

Quote:
ORIGINAL: RCAddiction

Questions:

Using the failsafe switch setup for power on/off, is there any problem with balance charging the A123's thru the 3 conductor JR balancing connectors?
The only issue will be if you charger can handle the common ground created. This would be created no matter how you connect two batteries together, even through switches since they only switch the hot lead. If the charger cannot handle a common ground you could damage the charger.

Quote:
The "Flight Packs" page on the Smart-Fly website doesn't show any A123 packages. Everything shows a regulator. Your recommendations for A123 packages, along with the discounts would make it easier/faster/slightly cheaper. So, this is both a suggestion as well as a request for your recommendation for an overall package suitably sized for my plane.
The Flight Packs were created when we did not have PowerSystems. The various combinations of all the products would create just too many variations to be practical. Sorry.

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thanks!
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Old 07-20-2008, 03:03 PM
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Default RE: Power Expander w/FS and A123

To my knowledge, the FMA chargers will only charge A123 batteries if they have a balance tap on them

Is the common ground issue caused by the Battshare function built into the Power Expander and the Wolverine? I don't believe this is a problem with standard JR or MPI charge switches when the 3rd wire going to the receiver is pulled from the connector.

Recommendation
Can you suggest a complete A123 compatible system for a 75cc plane that would allow me to charge the batteries without disconnecting them? Seems lots of people are doing this somehow with larger planes, and are rapid charging between flights.
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Old 07-20-2008, 03:11 PM
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Default RE: Power Expander w/FS and A123

Hi,
You are correct about the FMA chargers, they only charge through the balance lead. The common ground is not caused by the BatShare but because you are plugging two batteries into the same place. JR and MPI charge switches ONLY break the positive lead, the white and black (ground) are passed directly through the switch. To my knowledge there is no switch out there, including the Wolverine, that breaks the ground wire as well as the power wire.

There is no system I can recommend that will not give you a common ground. You would end up with a common ground even connecting through two JR switches to a receiver. Also, charging through a JR balance lead you are limited to 3 amps charge, this is all that kind of connector will take on a continuous basis. More than that and the plastic on the connector and wires will soften and you may short and cause major damage to your charger. Everyone I know of that is fast charging is doing it through the Deans connectors by unplugging the batteries.


Quote:
ORIGINAL: RCAddiction

To my knowledge, the FMA chargers will only charge A123 batteries if they have a balance tap on them

Is the common ground issue caused by the Battshare function built into the Power Expander and the Wolverine? I don't believe this is a problem with standard JR or MPI charge switches when the 3rd wire going to the receiver is pulled from the connector.

Recommendation
Can you suggest a complete A123 compatible system for a 75cc plane that would allow me to charge the batteries without disconnecting them? Seems lots of people are doing this somehow with larger planes, and are rapid charging between flights.
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Old 07-20-2008, 07:30 PM
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Default RE: Power Expander w/FS and A123

Robert,

I just ran a charge test with 2 batteries with parallel switches into a single receiver and it was no problem.

I plugged each A123's 2 wire 6.6v output through a charge switch then into a receiver. The setup included (2) A123 batteries, (2) charge switches, plugged into 2 slots in a single Hitec receiver that I had on my bench. To make sure each circuit worked, I plugged a Voltwatch into another slot on the the RX, and turned on each battery one at a time to make sure each one was alive and connected properly, then shut off both switches.

With both switches off, I charged the first A123 battery thru the loose 3 wire JR style balance plug, with the FMA charger. It did a very brief fast charge (it was 95% full already) and then completed a "safety" charge until it was at 100%. I then charged the 2nd battery the same way. No problem. Nothing got even slightly warm and the charges all terminated "normally".

Ok....I now know I can charge them each with no issue it seems, using conventional, parallel switches between the batteries and receiver. However, I don't know how the failsafe switch operates between the batteries and receiver. Since it is always drawing a small amount of power, I assume it might behave a little bit differently with some possible connection always being alive between the 2 batteries.

With the success charging thru the parallel standard switches, do you think I should stick with that kind of switch, or would I likely be equally successful with your failsafe switch?

thanks!
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Old 07-21-2008, 09:06 AM
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Default RE: Power Expander w/FS and A123

Hi Lee,
It may have worked this time but if the charger cannot handle a common ground it may not always work. Electrically there is no difference between using two mechanical switches and the failsafe switch. Both create an open circuit in the positive lead and leave the ground lead connected. If you go ahead and charge both batteries at the same time, no matter if you use mechanical switches or the failsafe switch, be very careful. This can be dangerous and cause a fire. You should check with FMA and see if their charger can handle a common ground. It may be that it can, I have no idea.
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Old 07-21-2008, 09:33 AM
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Default RE: Power Expander w/FS and A123

I had not planned to be charging both at the same time. I did not even think about that. I have charged 2 li-ion at the same time with the Fromeco 5 port charger in other planes....no problem.
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Old 07-21-2008, 09:37 AM
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Default RE: Power Expander w/FS and A123

Hi Lee,
OK, I really thought that was what you were asking. I guess I just missed the point. Sorry. Charging one at a time works just fine. I guess I figured when you were talking about charging at the field fast that I assumed you were going to charge both at once. Please excuse my divergence here.
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