Lipo charging

[Chris Card]

Do you reckon those balance taps would be ok for 2A Timbo?  That would let him charge in just less than an hour and only at the very top of the charge would the charger's power limit kick in.

 

I know I've charged at 2A via a servo connector on occasion and a JST-XH possibly has a bit more meat to it.

[Tim Mackey]

Im not sure its the taps /plugs themselves that are the issue - the actual wires used on some balance leads are VERY thin and fragile - and I simply wouldnt like to condone running 2A through them. Obviously its the individual's responsibility in these sort of matters, and although I may well do it (in fact on some of my Rhino3s packs, I have charged at 2.5A via the balance plugs) telling someone else to do it, and that all will be fine is something I wont do.

Sorry to sound evasive but I am sure you know where I am coming from

[Garry Pollard]

Hi again lads and especially Timbo and Peevie

Postman arrived today with the lead which had an instruction sheet with it. It states "this product is used to charge 2 packs of 3s at the same time with GTP-A8 and A6.

Specs

working current 0.1A - 15A

Weight 13g

Dimentions 35*130*10mm

Twins adapters are sutable for charging two packs of 3s lipos at the same time. If you charge only one pack please plug the battery directly into the balencing port of the charger. It will extend the charging time when you charge two packs with different capacity or different discharging degrees. Please use the batteries which are the same in capacity, discharging degrees, factory and discharging rate with TWINS adapters

TWINS specs including 4s to 2*2s 6s to 2*3s 8s to to 2*4s etc

Hpoe this makes sense to you as it dont to me. To put this to bed do I still charge at max 1.5 as you both sugested

Garry

[Chris Card]

15A ? 

[Tim Mackey]

I stand by my original suggestion that charging via the balance tap leads cannot be done safely above 1.5A. Who supplies the lead ...I may well contact them.

[Garry Pollard]

I have double checked Peevie and it is definatly 0.1A to 15A working current

Timbo on the leaflet there is no supplier apart from saying it is a G.T. Power TWINS adapters(6s to 2*3s) But was supplies by and ordered from Century UK Ltd www.centuryuk.com. I can assure you both that I will not be charging at more than 1.5A, and glad once again that I asked for help on this forum

Garry

Their Phone no is 01795437056 also [email protected]

 

[Tim Mackey]

I'll follow it up, and post back here.

However, my conclusion is still that if you choose to not use the attached heavy main power cable and deans plug, you should NOT charge at more than 1 -1.5A. The claim that this "unit" will allow charging at up to 15Amp, is I think, based on the user connecting the 2 x 3s pack main leads in series, and then using the attached deans plug to charge from the chargers main output.

Does the leaflet which is supplied with it not expalin or show a diagram at all?

Edited By Timbo - Administrator on 23/12/2009 15:23:15

[Garry Pollard]

Timbo

All the relevent details on the sheet were copied from the sheet on my post before last.

There is a picture of how to conect (poor quality) and it shows the unit plugged into the chargers balance socket and the deans plug lead from unit plugged into a banana lead with adeans male plug on it. Then the lipos are conected to the unit by the balance leads, with the main power leads left conected to nothing , just laid by the side of the lipos. My main worry is that someone else may buy one of these units and may not have access to Peevie and your expertise in the electric field and have a nasty accedent, as could have happened to me without your guidence. If any use I could send the sheet by post if you PM your contact details

Garry

[Tim Mackey]

I have seen the diagram you refer to, and the main leads with the deans plug on, are connected to the charger concerned ( the GT6 I believe ) because that charger, like almost all chargers, needs to charge through the main output sockets, and the balance sockets are NOT used to feed charge current to the battery, but merely "shunt" out any high level cells with a low "bleed" current to bring them down to a suitable level. Its plain to see that the only way the batteries are receiving their actual charge current with this adaptor in use is via the deans connecter which is only then connected internally to the two outermost balance tap leads. These are, as I say, and do appear to be, only thin gauge wires and cannot IMO support a current of 15A. Of course, without actually having the unit in front of me I cant swear to the thickness of the wires, but they sure look like regular thin balance lead wires only.

[Garry Pollard]

Timbo

I can confirm that the balance plug wires are of the normal thin wire found on all lipos

and I do not think they could support the type of current they claim as you quite rightly pointed out

Garry

[Peter Beeney]

    With great respect, I wonder if I might add some further comment to this thread? Would it not be possible to consider that, if the balance lead is actually used to charge the battery the current in the balance leads might actually be zero? The exceptions being the end of pack negative and positive leads. These might carry the full charge current, but only of one cell, so in fact the actual power levels involved may not be the same as if the battery is being series charged.
    In the example above, a 15A charge rate at 1C implies a 15Ah battery, a fairly hefty lump.  By modelling standards anyway. At 5C, I reckon that’s a 3Ah pack. Which, I suspect, means that the cell voltage will soon rise to the point where the charger comes out of current limit and thus the charge current then starts to tail off, thus lowering the current rate anyway.
    I have to admit, I haven’t done any specific current carrying checks on balance leads, but I have done some on battery/switch harness wire in the past. This was for a slightly different reason, to see just how much current it will carry; and beyond. This might well be around the same cross sectional area as balance leads, I haven’t checked. As I remember, and it was a while back, up to around 15A very little appeared to change. At around 40A the insulation started to move and swell up. At 70A the plastic became liquid and dripped off, and the wire glowed bright orange and burnt through. I never did get it to catch alight, although my colleague had done so when there was a short circuit. And I used a 12V lead-acid, double the voltage of his 6V nicad.
    This is absolutely Not to say that the balance lead will carry a heavier current, generally speaking this lightweight wire is very lowly rated, but it may well be worth some checks, sometime. I think that it might at least be saying that it’s possible that it will carry slightly more current than we think.
    I hope some of this may be of interest.                  PB 

[Tim Mackey]

Hi Peter, I know where you are coming from, and agree in principle with what you say, however, as I stressed before, I have myself occasionally charged at fairly high current through the thin balance leads, but would be reluctant to condone such practice to others IYSWIM As to the charge currents involved, again I agree that the likelihood of high currents is only short duration, especially if the battery was not completely drained as it were, in which case the charger will fairly quickly enter the CV stage. It does beg the question however why the unit has such obviously heavy leads connecting the deans to the charger output, only for these to then morph into the weedy little balance leads that actually connect the battery end leads

[Peter Beeney]

    Timbo,
         Actually, the little point I was trying to trying to make was the fact that if you charge a pack via the balance leads they do not need to be a massively substantial cross sectional area because there is zero current flowing, at least in the wires; with, as I said, the exception being the end-of-pack connections, but I suspect these power supply leads would normally be connected to the charger as well, anyway. However, if you are going to charge each cell in the pack individually, one at the time, which it is easily possible to do, as a 1 cell, then the leads would of course have to carry the full charging current rate.
    I also tend to think it’s possible that adaptor might be accurately rated at 15A, max. Would not this apply to the input leads; and the internal gubbins? If you then split the 15A over 6 cells, 2 by 3 cell, that’s 2.5 amps max each, much closer to the balance lead capacity. So then, by implication, this would limit the battery size to 2.500mAh anyway. At least, to be able to charge at 1C.  And, with two packs on charge simultaneously we’re talking up to around a possible 60 watts. It seems to me that anything less than a 70W max output charger would find itself near the top limit here.
    As always, there are caveats. Quite often, these things are not always exactly what they say they are on the label. Particularly when it comes to consumer items, made in faraway lands. So it could just be an optimistic rating. And, more importantly, this is all supposition on my part. At least, until I can get my hands on the device, (if I bother), and try and establish that I’m sure I know exactly what is actually going on.
    Always a good topic of conversation for Boxing Day……             PB