What is the minimum I need?

[trillian]

OK, I have two electric helis, a 3DX450 and a Gaui 550.

The Gaui uses the same type of lipo but with two in series.

Currently I have an Align RCC-3CX balance charger which can charge one 3 cell pack at a time.

Do I need a digital voltmeter to match the voltage of my two 3 cell packs for running them in series on the Gaui ?

I know there are better chargers out there and on the one hand I don't want to spend a fortune on a charger but on the other I don't want to ruin any lipos.

So what do you guys think is the bare minimum equipment I need?

[kgfly]

Do I need a digital voltmeter to match the voltage of my two 3 cell packs for running them in series on the Gaui ? No, since you are connecting them in series the voltages of the two packs simpy add together, for example:

2 x 3s1p (11.1V) 2100 20C/42A in series = 6s1p (22.2V) 2100 20C/42A
2 x 3s1p (11.1V) 2100 20C/42C in parallel = 3s2p (11.1V) 4200 20C/84A

If you are going with compound packs then get yourself a second charger so that you can charge at least two packs at a time, otherwise each 8min flight of the Gaui 550 will translate into almost 3 hours of charging time.

If you think you won't be going to anything with larger packs, then get one or two FMA CellPro4S. An excellent integrated 2s-4s/50W balance charger that is only USD$75. A very good alternative that will give you more flexibility is an eStation BC6. An excellent integrated ac/dc power supply, multichemistry 2s-6s/50W balance charger. More expensive but you get a lot for your money.

Both of the above are great for the 3s/4s packs normally used in those helis. They are a bit underpowered for the larger capacity packs used in most helis larger than the 450-class. For example the 50W/5A output limit means they will charge at about these maximum rates:


For a 50W/5A output LiPo charger the charge current limits are about:
No. cells Max charge current
--------- ------------------
1s 5.0A
2s 5.0A
3s 4.4A
4s 3.3A
5s 2.7A
6s 2.1A
--------- ------------------


If you think you might have T600 or similar in your future then get an eStation BC8. An excellent integrated multichemsity 2s-8s/150W balance charger.

[trillian]

Thanks Kenneth I really appreciate the input.

I am slightly paranoid about these LiPos with all the stories I hear about them 'puffing' and the worry of over-discharging them etc. If they were not so expensive it might be different.

I might look into the a123 packs at some point as well.

-S

[kgfly]

The FMACellpro4S(4A) model and the BC6/BC8 all support A123 (LiFe) cells which is another reason they are a good choice. :) Of course apart from their improved safety and robustness, one of the great benefits of A123 is their ability to be safel y charged at up to 10A without significant degradation of their lifetime. The 50W/5A chargers simply don't have the oomph to take much advantage of the over-1C charge rates which makes the BC8 the pick of the bunch if you can afford it.