A123 Batteries for Dummies.

[hybris]

I believe that you can't charge two packs connected in parallel with two Cellpros. You must unplug the two packs before charging. I remember reading this someware.

[aerobob]

It's in the CellPro instructions. Two packs that share a common ground won't work correctly. At least that's what I remember reading.

[Pale Rider]

For the life of me I cant understand why charger manufacturers dont make their multi-port chargers able to handle the common ground issue..the only ones I know of that can do this are the Alpha 4, Hughes Spectra, and Miniron mobile...Only three!!

[dick hanson]

	Quote: Originally Posted by hybris
	I don't know how two cells connected in parallel can be off .1 volts. I am not suggesting connecting separate pack in parallel for charging. I am suggesting that a pack can be built with parallel cells. What testing did you do to to prove this unsafe? What was the result? Another option is to build two 2s packs and use a Batt Share. this would also give you twice the capacity.

I won't argue your point - just do this
buy some 123 cells and hook two in parallel -charge and watch voltage at each cell during charging - you may have zero problem -both may move exactly to 3.6 and be fully charges at the same time -
However - if you take a fully charged pair in parallel - THEN reduce voltage in ONE cell say .2 v and recharge - tell me what happens --

[klhoard]

	Quote: Originally Posted by Pale Rider
	For the life of me I cant understand why charger manufacturers dont make their multi-port chargers able to handle the common ground issue..the only ones I know of that can do this are the Alpha 4, Hughes Spectra, and Miniron mobile...Only three!!

.
.
The CellPro acts like 4 indepenent chargers, each one working on its own cell. If you had a common ground, then the cells would be paralleled and it wouldn't be able to monitor each cell individually.
.
I'm sure there is a way to hook up a switch that will break the common ground and allow the CellPro to charge (2) 2S packs as a 4S pack. That may be the best way to charge both 2S packs simultaneously.
.
Actually, in this case, the batteries won't have a common ground until the receiver which is on the other side of the charge switches. So, I guess you need to find a way to connect the two packs with the charge switches off so it looks like a 4S pack to the CellPro. . .
.

[Rolling Thunder]

I ran my batteries today. I put 2 2S packs in my Comp Arf Flash. I pulled out the regulator but left in the Batshare. Everything worked perfect.

[Pale Rider]

I prolly missed it somewhere but what is the finished weight of a 2S pack ?

[toprudder]

	Quote: Originally Posted by dick hanson
	I won't argue your point - just do this buy some 123 cells and hook two in parallel -charge and watch voltage at each cell during charging - you may have zero problem -both may move exactly to 3.6 and be fully charges at the same time - However - if you take a fully charged pair in parallel - THEN reduce voltage in ONE cell say .2 v and recharge - tell me what happens --

If you hook two in parallel and check the voltage of each, they will be the same as long as they are connected to each other. If the state of charge is different between the two, then the only way you could determine that is to monitor the CURRENT flowing into each one. The charge algorithm is a constant voltage, current limited, so until the current drops below a very low value, the charger will continue to supply current and it will go to the cell that is not fully charged - you can't overcharge either cell since the voltage is not allowed to go above a safe value. So, IMHO (without actually trying it yet!) I don't see a problem. But, I may be wrong.

However, I would much rather have packs that are NOT wired in parallel, for the very reasons mentioned. In particular, it would be difficult (not impossible) to monitor the health of a pack if they are paralleled.

If I want redundancy, I would seriously consider something like a Batshare.

Bob R.

[Kiwi]

	Quote: Originally Posted by Pale Rider
	I prolly missed it somewhere but what is the finished weight of a 2S pack ?

I don't have my scales home with me but each cell is 70 grams. 140 for a 2S then. I done the one in each hand thing yesterday, 2600 Li-Ion and a 2300 A123. I don't see it making any difference at all to my flying. BUTTTTT!!!!!!!!!

Given I don't need regs, extra cables etc I just know its a slightly lighter setup. And I can give myself a hangover with the difference in price if I so desire.

[Pale Rider]

Close enough!

Hey anyone try using a single A123 on the ignition? I know some guys using a 3.7v Lipoly so why not right ?

[dick hanson]

I worded my explanation really badly - obviously - two cells hooked together in parallel will read a "common voltage."
I really should have said -one cell can be simply a short and you would not see it .
If all is well they would likely self balance .
but as was noted trying to charge two seperate packs in parallel would possibly get you in trouble if one pack was lower and both were close to full to begin the charge
On the Cell Pro -- usingtwo cells - if you futz with doing a final charge up after cells were not used for a while and were fully charged -it is possible to get one cell above th other in voltage and when the charger sees .15 difference --it goes into a trickle n balance "safety" mode which may take forever (over an hour ) to equalize.
the cells self balance very well -just charge in series and leave em alone

use em fully charged - run em down till power quits -etc.. the cells don't care I flew another 4 cell pack till it quit today at 40 amp loads -no problems .

[Rolling Thunder]

My packs with shrink wrap run both front to back and side to side. Then charge balance lead and rx lead came out at 5.4 oz.

[Pale Rider]

	Quote: Originally Posted by Rolling Thunder
	My packs with shrink wrap run both front to back and side to side. Then charge balance lead and rx lead came out at 5.4 oz.

Thanks! That rules out running dual packs on my 50cc planes..would have to go with a single 2s pack.

[Zeeb]

I'm just starting to pick up some of these cells and a charger. Your comment brings me to something I saw another member post since I'm quite interested in having two switches/paths for my 50cc bird. Just put the packs together with dual output leads, then you can have dual swiches (eliminating the most common failure point) and a dual current path for higher amperage capability to the rx.

[Pale Rider]

	Quote: Originally Posted by Zeeb
	I'm just starting to pick up some of these cells and a charger. Your comment brings me to something I saw another member post since I'm quite interested in having two switches/paths for my 50cc bird. Just put the packs together with dual output leads, then you can have dual swiches (eliminating the most common failure point) and a dual current path for higher amperage capability to the rx.

Thats what I plan to do as well..My current setup has 2 rx packs and 2 switches which is the way Ive always set my planes up..Now I will only have 1 pack but will have the dual leads....Will have to get used to only having 1 battery pack instead of 2...