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-   -   BD VPX battery voltage (http://www.rcuniverse.com/forum/batteries-chargers-84/7984770-bd-vpx-battery-voltage.html)

SU29 09-23-2008 09:15 PM

BD VPX battery voltage
I bullt a 2 cell pack using one of the VPX batteries and need to know what is the rule of thumb for checking (voltage etc) as far as when to stop flying and charge the battery?

I understand these are lithuim-phosphate batteries, is this correct?

Thanks for the help


Snipin_Willy 09-23-2008 09:51 PM

RE: BD VPX battery voltage
Lithium Nano-Phosphate would be A123's term. Most flyers will go by time rather than voltage. I just 2-cell packs in my vendetta and have the LVC set for 2.0v per cell. If your flying till you can feel the motor getting sluggish then you're about to crash, the voltage drops that fast when you get to the end of the charge.

FLPilot 09-23-2008 09:53 PM

RE: BD VPX battery voltage
These threads will answer most questions.



SU29 09-24-2008 06:18 AM

RE: BD VPX battery voltage
I read some where that these batteries were the Lithium phosphate chemistry however they are not the A123 type cells. So I'm looking for the safe flying voltage for glow/gas planes not electrics at this time.

Thanks for the info and the link, good information.


FLPilot 09-24-2008 06:52 AM

RE: BD VPX battery voltage
VPX is the same as A123 in this case.

This chemistry is not about remaining voltage. Get a charger like a cellpro 4s, that tells you how many MA you put in. With some history you can determine the MA being used per average flight. They can be charged at the field in 15 min or less.

You cannot use voltage as a measure of remaining capacity like a NimH.


Bob Pastorello 09-24-2008 07:48 AM

RE: BD VPX battery voltage
Using voltage as a determinant of remaining capacity on A123 chemistry cells will bite you BAD.
In my own tests, a 2S A123 pack discharged 2100mah before it reached the "cliff" where the voltage dropped from 6.2v for the pack to 2.6v ** in less than 20 seconds **, under a 1A discharge load.

Fromeco makes an excellent switch that measures milliamps drawn through the device, and displays it on the switch mounting plate. There is NO substitute for knowing the milliamps drawn by your particular configuration, and using a charger that tells you how much you put back in.

The absolutely FATAL flaw that will give the LiFe technology a bad rap will be those who persist in attempting to use measured voltage as a determinant for the "fly / no-fly" question.

SU29 09-26-2008 05:05 AM

RE: BD VPX battery voltage
Thanks for the info, that is what I gathered after looking at some data sheets and graphs. Knowing that they are A123 is even better. I do have a 4s and 10s so I will put them to good use.


Bob Pastorello 09-26-2008 07:50 AM

RE: BD VPX battery voltage
That will be great. If you disassemble your own B&D VPX packs, be sure to remove the resistor that is hidden in the white wire that goes to the center tap.

SU29 09-28-2008 05:28 AM

RE: BD VPX battery voltage
Hey Bob, I did remove the resistor now I'm trying to decide on options for balance charging. I also have the Fromeco Cube charger that will charge through the charge jack with out balancing. I am leaning towards the balance side and making a adapter to work with the 10s. I use the HD Jr type switches so I think I will have to cut the white wire going to the receiver for this to work?


Bob Pastorello 09-28-2008 06:05 AM

RE: BD VPX battery voltage
That's correct. It's orange, I think, though. In the switch, the orange and black wires are "wired through", and the switch contacts are dedicated to the red wire.

dirtybird 09-28-2008 10:07 AM

RE: BD VPX battery voltage
Since Wall Mart is dumping these I wound up with 8 batteries and 2 chargers. I made a plug that fits the battery. A crimp on spade lug auto connector fits just fine. You have to fabricate a holder for the two connectors.
Now when I go flying I just strap in a freshly charged battery and go. Its plenty of flying time for me

rlmcnii 09-28-2008 10:39 AM

RE: BD VPX battery voltage

Is Wal Mart getting out of the VPX business?? A few days ago I bought a pack for $12. It seems too good to be true....a nice pack for ignition or sport-sized glow-powered planes for 12 bucks.

BP is certainly correct: Do not use voltage as a go/no-go.

SU29 09-30-2008 07:28 PM

RE: BD VPX battery voltage
I picked several up at Walmart for $11 and was told they are not going to sell them any more do to the way BD packaged the VPX line.

I got the first one intalled and ready for testing.

Bob Pastorello 09-30-2008 07:32 PM

RE: BD VPX battery voltage
The irony of their marketing decision is that the B&D VPX tools are pretty good. I have several, and their flashlight and drill/driver (with the chuck) is a handy "airplane-sized" tool.

Thanks to dirtybird, the fact that our local WalMarts are zero-stock is a non-issue.

These are true "A123" technology; they should last a really long time in our usage.

SU29 10-03-2008 12:46 PM

RE: BD VPX battery voltage
I cleaned my walmart out as well at that price. I am thinking about the drill - driver myself, looks like a very handy tool and about the right size for hobby use.

I'm using 18ga servo leads and will use two packs with 2 switches for redundant power and double capacity. Should be a good clean set up.

nikg 10-04-2008 08:47 PM

RE: BD VPX battery voltage
Would a 3-cell A123 work well in a Super Cub? My standard pack is a 7-cell NIMH, but I have heard of people using 8-cellNIMH and even 3s Lipo (11.1v?) There is a jumper in the SC that needs to be removed when using lipo. I believe it is some sort of low voltage cutoff. Would this work with the A123 cells?
Also, how would one charge these? Could you use the stock VPX pack charger for a 3-cell configuration or not? If not, then is there a relatively cheap charger that does A123? Will it also do lipo?
Finally, I saw a thread about rebuilding these into 2-cell packs by disassembling them and soldering bars and wires much like with NIMH cells. Is that a bad idea? I have made numerous NIMH sub-c packs and I know you have to be very careful not to overheat the cells when soldering. I have an 80W iron with a big tip that touches the cell/bar for less than a second before I pull it away. Can you solder these A123's without harming the cell or risking some kind of explosion or venting etc.?

Extra Credit for anyone who answers all these annoying questions:D

Snipin_Willy 10-04-2008 11:44 PM

RE: BD VPX battery voltage
The A123's are a little trickier, to do mine I tin the ends of the cells with solder and flux and also tin the wire leads or battery bars that go to them. then it's as easy as putting the battery bar on top of the cell and putting the soldering iron on top of the battery bar for a second or two. The 2300 size cell are a bit different, the positive ends have a steel plate that is soldered to the aluminum body, and you have to solder on top of the steel plate for anything to stick.
As far as charging; depends on how much you wanna spend, or if you wanna build a lipo-dapter like circuit you might get a charger pretty cheap (http://liglow.com/a123.htm). I really looked around for a good A123 charger before I settled on the FMA cellpro 10s. I don't think you'll need 300+ watts of charging power for little 1100 batteries, but I needed it for my 4s 2300's to keep my charge times down.

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