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Building lipo packs
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 Posted: Fri May 17th, 2013 06:50 am
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Craig W
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Bill, a picture of said item might be helpful, but on a 2 cell pack, you will usually have a 3 wire balance plug attached. is this what you are referring to?



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 Posted: Fri May 17th, 2013 07:09 am
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Robin2
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@Bill, The 3rd wire is almost certainly for balanced charging. If so it will be connected to the connection between the two cells and if you measure the voltage from the centre connection to either of the other connections it should read about 3.7v - half the pack voltage.

@mike, Thanks for the Stanton link. It's interesting but much too bi for my locos.

...R

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 Posted: Fri May 17th, 2013 07:29 am
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johnhu
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1whudson wrote:
Thank you Johnhu. I have already settled on th 2S lipo without the stepup solution. I find the 7.4v is just right with its 200mAh. I have yet to solve to my satisfaction the on/off switch situation yet. What switch did you use and is it hidden? Is the switch located between the battery and the receiver? Did you only interupt at the positive pole or both poles? Finally, what do you know about the reed switch? Didn't know you were getting in so deep did you?

Bill


Hi Bill. The switch I use is a micro slide switch from a local electronics store (about 5mm x 3mm in size). As I'm in Australia, I'm sure you'll have more options than I do. The switch is an SPST switch, so just switches the positive connection. The negative connection is common).

I've hooked it up as follows: The centre pin (common), goes to the battery. One of the other pins goes to the receiver (ie: battery connects to receiver - receiver turned on). The last pin goes to my charging lead (ie: this disconnects the battery from the receiver - turns receiver off, whilst at the same time connecting the battery to the charging lead). Hard to write, but hopefully it makes sense.

Pin 1 to charging lead, pin 2 (centre/common pin) to battery, pin 3 to receiver. The battery can then be either connected to the charging lead to charge (receiver off), OR connected to the receiver (receiver on).

I've glued it to the side if the cab (on the inside) where it's hidden just inside the cab doorway. I use a small right angled set of tweezers to reach in the doorway and move the slide switch.

I hope the info helps Bill.

John - Perth, Western Australia.

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 Posted: Fri May 17th, 2013 10:16 am
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wv railbaron
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Bill, are the colors of the wires black,red and white? Can you post a picture of the battery? My batteries with a balance connection are more than 3 wires and have a definite separate connector that is put into a different port on a charger. There is a protective jacket to place lipo batteries into when charging to absorb any problems.
Steve Sherrill

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 Posted: Fri May 17th, 2013 01:17 pm
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Masonbogie
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The Stanton system is available through NWSL and works very well. I even have a 2 cell version he did up special order because of heavy draw.



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 Posted: Fri May 17th, 2013 01:26 pm
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mwiz64
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None of mine have a third wire on the power leads. I wonder if its a temprature probe wire?



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 Posted: Fri May 17th, 2013 03:06 pm
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1whudson
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Hi Folks
Guess I wasn't as clear as I thought about my battery. So far, in my newness to this subject, all of the two and three cell batteries [at least the ones I have purchased] have only one connector with three wires, e.g. red, blk and white. It is the white one that I assume is for balancing when charging the battery in question. It seems to be the bigger lipo's that have a seperate balancing plug in conjunction with the charging plug.

Bill

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 Posted: Fri May 17th, 2013 04:05 pm
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W C Greene
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You assume correctly about the white wire. Yes, larger batteries have separate plugs.

Woodie



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 Posted: Fri May 17th, 2013 04:08 pm
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Herb Kephart
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Mike---

Do the brushless motors that the RC industry seems to be going to control the speed by PWM or by controlling the frequency of the polyphase input to the motor?

IF it is PWM, what frequency is used?


Herb



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 Posted: Fri May 17th, 2013 04:26 pm
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mwiz64
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Here is what I'd call a typical small lipo. It has a red JST power connector and a white JST-X balance tap. Most balancing chargers will work with this wire layout.





And here is a Lipo specifically made for some Eflight brand micro models. Notice how it only has one connector and it looks like the balance tap connector in photo above. Woodie is right, the center wire is for balancing. Some chargers can deal with this wire layout but most cannot. Obviously the "proper Eflight" charger will balance charge this battery with this connector. My charger has the ability to perform what it calls a "safety charge". In safety charge mode it will slowly charge any battery up to 8S through it's balance tap. I believe it would charge this battery if plugged into the proper balance port. I love my charger (Revolectrix Powerlab 8) but it's WAY overkill for this application. Anyway, if you have one of these batteries and you want to ignore balance charging just connect red to red and black to black. Again, I don't see the sense in this. There are chargers that will balance charge every time and at no extra effort on your part.



It took me a little research to get you that last answer. I don't have any batteries like that one. It looks like a great solution for a compact 2S pack.

Last edited on Sat May 18th, 2013 04:08 pm by mwiz64



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