Charging 4 saddles at once?

[Cardnim]

OK, probably a stupid question, but thought Id ask anyways.

Ive jsut moved from stick packs to saddles and tonight will make up a balance lead so I can charge each pair of saddles as a set (i.e. 2 saddle packs on charge at once, just like my old 7.4v two cell stick packs)

However, it occurs to me that a saddle is just a single cell lipo that we put together to create the 7.4v we need; and if we can do this for charging, then surely I can put ALL FOUR of my saddle packs together using linkage wires, and then balance charge them all at the same time as a 4 cell lipo battery.

My thinking is that as long as the batteries are all wired in series (i.e. not parallel) then it should charge fine.

Or am I just stupid?

[Cardnim]

I made a little diagram to help explain what I mean:
In this example, each saddle is 3.6v, 5000 mAH, rated at 60C

[Big G]

you'd gain nothing, but run the risk of unbalancing the pair. In theory yes it can be done.

Assuming packs are 5000mah charging at 5A will take an hour, but your setup makes the pack 10000mah. to charge at 5A will take double. 2 hours.

You'd be better off buying this
http://www.jespares.com/electric-mod...ategory_id=486

[Cardnim]

Cheers Gaz. I know Im not seeing this correctly mate, but heres my thoughts:

Originally Posted by Big G

you'd gain nothing, but run the risk of unbalancing the pair.

- cant unbalance the pair, as all 4 are going into the balancer on the charger, so if we assume the charger is working, then all 4 should be balanced (this would be no different than charging a standard 4 cell lipo for 1/8th scale say)

Originally Posted by Big G

...but your setup makes the pack 10000mah...

- although the capacity is increased, does that matter when charging? (it porbably does but Im too thick to see it!)
Here why i ask...

In a stick pack, its rated at say 5000mAH.
Now I always took that as the TWO CELLS TOGETHER.
Thus, 1 hour @ 5amps = fully charged.

BUt in my new saddles, they are INDIVIDUALLY rated at 5000mAH (Im basing this on the little sticker on each one (they are Vampire cells) says 5000mAH), so therefore, even if I charge two together as normal, that still means 2 hours at 5amps?!

Hope that makes some sense?

[peetbee]

Yes, what Gaz is saying is that you wouldn't charge them any faster.

What benefit are you looking to achieve with this as at the track wouldn't you normally be charging one pack whilst using the other one anyway?
(plus at home you can charge one pack after another within the same time as the method you propose)

[Cardnim]

You're right Pete (and thanks for the reply chum) but Im really just trying to understand saddles a bit more.

My understanding was that each saddle was rated INDIVIDUALLY, but Ive now realised it's as a pair (think this a bit bonkers labelling, as it shows on BOTH my Vampire cells as 7.4v / 5400mAH, not 3.6v / 2700mAH as I would have expected)

What I was hoping to achieve is not at trackside (where you are right, I would only ever be charging two at a time), but at home, when putting on 1 charge (albeit twice as long) would be kinda nice - just turn on and forget about it for 2 hours. Come back, and take all cells to race.

Because I am making my own balance lead, I could easily make it with the above in mind so it could do both scenarios; but Im guessing it doesnt really make much sense now.

Sorry guys, I'll put it down to a senior moment and move on.

(although, got to say, I reckon Im not completely stupid about electronics, and when a single cell says 7.4v / 5400mAH on it, then I would always take it as rated at that - cant believe that Im the only one to think that about Lipo saddles)

[swords]

the capacity would still be the same 5000 but the voltage would be higher 14.8 so they would actually charge quicker than charging seperately as you are putting more watts in which is the key figure, watts is easily worked out by a simple equation, volts multiplied by amps=watts, this simply shows that you can acheive the same power out put with lower amps at higher voltages or vice versa, as an example this country has a connection to the french national grid which runs at massively high voltages simply to keep the amperage down

[mark christopher]

Originally Posted by Cardnim

I made a little diagram to help explain what I mean:
In this example, each saddle is 3.6v, 5000 mAH, rated at 60C

they would not balance corectly as above
if it was a 4s pack it would have a balance lead between each cell block
the two on the left will only be balanced to the two on the right, but the left pack could have a low cell and the 2nd left have a higher cell to compensate, which is why you should have more than one balance (blue) lead
if you had blue leads between pack 1 & 2. 2 & 3 and 3 & 4 you could charge them as a 4 s pack ok