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View Full Version : FMA Skyvolt charger


JWN
09-13-2005, 05:39 PM
FMA just posted thier Skyvolt charger and battery announcement.
https://www.fmadirect.com/site/home.htm

I wonder what it would take to use this charger on other manufacturer batteries that already have taps installed such as Polyquest? It appears that the charge rate is user adjustable so one should be able to charge thier packs at 1C as they do with their current charger.

Greg Covey
09-14-2005, 09:24 PM
How about the 12" extension cable and a pair of cutters. :)

JWN
09-15-2005, 07:29 PM
Now that's what I call support!

Red Scholefield
09-16-2005, 10:58 AM
How about the 12" extension cable and a pair of cutters. :)

AND knowing the pin out to get the connections right.

JWN
09-16-2005, 03:00 PM
That too is very important. I'm just surprised to see a manufacturer help us use their product in a manner they have no control over.

Greg Covey
09-20-2005, 02:12 PM
Darn, was my signature still activated!? :)

Actually, it's not really me. Someone has stolen my password.

Looking into the solder end the picture shows the connections. The numbers are the nodes. The minus (-) sign is ground or black wire and the plus (+) sign is the highest node of the pack. On a 4-cell pack, you can measure cell voltages between the following pins:

- to 1
1 to 2
2 to 3
3 to +

JWN
09-26-2005, 06:27 PM
If I'm looking at this correctly, it appears the charger does not charge each cell individually, but instead only monitors their voltage while they are being charged through the main +/- lead. I'm not sure I understand how this balances the cells as all cells are charged through the main lead and the charger will simply turn off when the first cell reaches the cut-off voltage.

Red Scholefield
09-26-2005, 07:19 PM
If I'm looking at this correctly, it appears the charger does not charge each cell individually, but instead only monitors their voltage while they are being charged through the main +/- lead. I'm not sure I understand how this balances the cells as all cells are charged through the main lead and the charger will simply turn off when the first cell reaches the cut-off voltage.

You are not looking at it correctly. Each cell is charged individually until it reaches 4.2 volts. I'm presently testing one 3S pack now. Deliberately discharged one cell to about 3.5 volts and then connected to the SKYVOLT. Using the viewer software you can monitor the voltage of each cell. While the 2 cells that were at full capacity show FULL the one discharged is still being charged and will continue until it reaches 4.2 volts.

JWN
09-27-2005, 02:27 AM
I'll take your word for it Red. I guess there is additional circuitry in the battery itself to terminate charging to individual cells. Otherwise, I do not see how this can be done when charging through the main +/- wires. It "looks" like the white wires only purpose is to monitor cell voltage and not provide any real current for the charge process.

Greg Covey
09-27-2005, 01:57 PM
John,

I'm not sure what you are looking at above. There is no circuitry in the battery pack. The so-called "main wires" are used for high discharge current. All the wires are used for charging since the current is much lower. Yes, they can easily handle 10amps charging current at 4.2 volts. The Skyvolt charger balances each cell on every charge. No cell can go above 4.2v at any time.

During discharge, the main current flow goes through the thick main wires and the DPM monitors each cell through all the wires to determine proper shutdown on the weakest cell. The throttle setting also is a factor in determining what voltage under load to cutoff the motor power.

JWN
09-27-2005, 09:24 PM
Greg,
Ohhhh, now I see. I was expecting that charge current to be delivered through the thick wires ala old school chargers with the white wires only monitoring the cell voltage. Now it makes perfect sense! Thank you for lifting the obviously thick fog from my eyes!