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

[swords]

and yes each side of the saddle is just a 3.7volt cell( although there is usually more wired in paralell within each case)

[sosidge]

Although you can charge your two pairs of saddles as if they were a 4s pack, to do so safely would require wiring up an elaborate custom 4s balance lead - and because the packs will have different levels of charge in them after each race, the balance process would take such a long time that it would not be worthwile.

Safer and simpler to just charge each pack individually, with the supplied balance leads.

[Cardnim]

Just to add a bit of weight to my argument.
Just done a quick google on the three types of saddle ive seen around and it seems there are quite a few discrepancies between manufacturer's labelling (i.e. no industry standard) and I find this a bit confusing and slightly alarming:

VAMPIRE (my cells):
Clearly shown on EACH label as:
7.4v / 5400mAH


IP cells:
Clearly shown on label as:
3.7v / 5400mAH
and even worse, both say "Cell 1 of 2" which is just plain wrong.



...and then back to "7.4v" on each cell in this SpeedPower set?!:

[Cardnim]

Sorry guys, was working on that last post of mine with the pics and didnt see your responses.

Thanks so much for the info - that is excellent to know.
I thought it was right that the WATTS would increase as the voltage did.

However, as each cell is NOT labelled individually, we have a bit of a problem, do we?
i.e. ignoring new technology which can charge lipos at rates greater than 1C, the standard "safe" way to charge lipos is at 1C.
However, charging a SINGLE saddle cell at 1C of what is written on the label is wrong.
Take my 5400mAH - if I charge one at a time at 5.4A, then actually I have charged at 2C.
To charge one saddle pack at 1C I would need to charge at 2.7A.
Correct?

Re: balance lead. I didnt get a balance lead with the cells and the one in my charger uses a 2mm banana plug, so I have to make my own balance lead.

[sosidge]

Exactly what is the point of your posts about the labelling?

The cells are sold as a pack that is 7.4V and a stated capacity. Everyone else uses them as a pack. Everyone else charges them as a pack.

You don't seem to understand the nature of LiPos, yet you still seem keen to charge them in a different way. This is either pointless or dangerous - certainly your pit area is not one I would like to stand near at a race meeting.

[Cardnim]

Hey thanks for the nice friendly helpful comment. ffs.
I was only trying to get help with something I didnt understand BEFORE I did anything different than the norm.

[adam_u]

Have a look here mate for how you would need to wire up the balance leads - you can do it, it just means you are charging them as a 4s pack instead of a 2s. I can see a drawback if your cells are a little older/out of balance as it could take a long time for the charger to get all four cells in balance so could take longer than usual. I have those intellect cells and I have wondered why they don't say 1/2 2/2 myself too! I guess they snuck through the QC process before printing...

[Cardnim]

Originally Posted by adam_u

Have a look here mate for how you would need to wire up the balance leads - you can do it, it just means you are charging them as a 4s pack instead of a 2s. I can see a drawback if your cells are a little older/out of balance as it could take a long time for the charger to get all four cells in balance so could take longer than usual. I have those intellect cells and I have wondered why they don't say 1/2 2/2 myself too! I guess they snuck through the QC process before printing...

Thanks bud.

[i4n]

As I understand it from my electrnics theory many moons ago, each individual cell has to be the capacity that it's stated at, so those IP cells you've pictured each cell would be 3.7V, 5400Mah, 60c.

When you wire them together in series you'll end up with 7.4V, 5400Mah (as when you connect in series you increase the voltage but the capacity stays the same. Conversly, if you were to wire them up in parallel you'd end up with a 3.7v, 10800Mah battery).

Hope that helps.

Ian

[fidspeed]

Everyone else uses them as a pack. Everyone else charges them as a pack.

Not Completely true i'm afraid i have a pair me and my boy use them singly in mardaves and we charge our own that way as long as they are fully charged each. they will be balanced as a pair (ignoring negligible difference in chargers (if charged on different chargers) if used as a pair later and found to wildly out of balance then you more likey have a failing lipo that no balancing will remedy

no offence intended to anyone and quite happy to be put in my place and learn more about the black art of lipo tech

regards dave

[Cardnim]

Thanks Ian.
So even though my cells say "7.4v 5400mAH" they are in fact 3.7v 5400mAH each?

I appreciate your help, and you and the rest of the guys (apart from Sosidge) have helped me out loads.

I now know what each individual cell is rated at and what my own saddles labels mean. I also now how to wire them up properly for a correct balance charge, and better understand the implications which wiring them in series is having on the cells.

Thank you.

[mark christopher]

Originally Posted by Cardnim

.


Take my 5400mAH - if I charge one at a time at 5.4A, then actually I have charged at 2C.

incorrect, each cell is 3.7 volts, 5400mah, wired in serries which is how we use them, you have 7.4 volts and 5400mah, 5.4amps is 1c
if you wire them in parallel then you would be charging at .5c as you would have 3.7 volts and 10800mah