3D Romeo

My Feedback: (111)

Hi,

I'm not sure if this is the right place to ask this question, but figured it was the best place to start...

I'm converting a friends SIG 4-Star 40 from glow to electric, and we decided to permanently mount one 5-cell A123 2300mAh pack for the power source. Rather than making a hatch, or removing the wing, to swap out packs between each flight. The only problem with relying on only one battery pack is you have to charge the pack at a high C rate (3C-4C) if you don't want to wait an hour between each flight. Which leads to my question...

I was originally planning on making a small access panel to access the balance charge connector on the battery pack, and using one of those MPI arming switches to disconnect the battery until needed. Then I realized that this setup would only work if charging at a low C rate. I forgot when charging at a high C rate you need to use the balance port AND the main power connector.

So my question is...Does any have a simple setup for charging with the balance connector AND the main power connector, and also disabling the battery until needed? I imagine something could be done with something like the MPI arming switch along with some other switches. I want to keep it as simple as I can though, and please keep in mind that my battery, and all connections will be permanently mounted inside the airplane. So all charging connections and switches must be accessible from the outside of the airplane.

Any ideas would be greatly appreciated?

Thank you,

Mark

JoeAirPort

My Feedback: (41)

If you go with CellPro chargers you need just one 3 pin charge jack (does power and balance in one connector). I use the Deans 3-pin charge jack. Mounts on the side of the fuse. Works great. I charge at 4 amps. Takes about 10-15 minutes. Just use a normal switch as you don't need the charge port.

3D Romeo

My Feedback: (111)

Joe,

Thanks for the info. Would it be possible to post some photos of your setup when you get the time? Sounds simple enough. But it always helps seeing something to make sure I'm understanding it properly.

You say you don't need to use the charge port on the battery pack. But isn't balance charging just as important with LiFe cells as it is with LiPo cells? If so, and even if it's only needed once and awhile, the guy I'm doing the conversion for doesn't EVER want to take the plane apart (unless absolutely necessary). So if it is recommended that the battery pack be balanced at some point during it's life, I'd still have to make the balance connector accessible from the outside of the airframe.

To achieve the charge times I'd like with my battery pack I'll need to charge at 6.9A or more (2300mAh at 3C).

Mark

Johnnysplits

Check out www.hangtimes.com all the info and diagrams on using LiFe batteries and the cellpro chargers there

3D Romeo

My Feedback: (111)

Thanks for the link Johnny!

Funny story...I was just at hangtimes yesterday, but only checked out the A123 FAQ. I didn't noticed the A123 Setup Guide lol.

You were right...all the info, and diagrams you'd ever need.

Mark

ramboman

"when charging at a high C rate you need to use the balance port AND the main power connector"

ramboman

You don't need to balance each time you charge...
Use a dean plug to disconnect the pack and another one to charge it...
My Fokker D.VII has a 6s2p a123 pack charged at 20A...

3D Romeo

My Feedback: (111)

Thanks for the tip ramboman!

While perusing the internet, I noticed that 4A is the maximum they recommend charging at using the balance connector alone. So using both connectors (or just the discharge connector for those that don't feel the need to balance every flight) seems like the only way to go for charging at higher C rates, and does coincide with what you are saying.

Mark