Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length.

[HS93 (RIP)]

If you read my comments above, I said if it is designed to work that way by the manufacturer it is a different matter, these packs will have been designed by the manufacturer to be safe.

Not wired together by an amateur.

As Peter says they are series, and not knowing the difference between Parallel and Series points up the danger of amateurs getting "BURNED"

they are saddle packs for cars , I have some they are designed to run in series and have a big label saying, do not connect in Parallel. ill take a picture of some if you want

peter

[Timo2]

Hi All

    Quote form Supplier Web Site

           each 3.7V 5700mah so both 7.4V and 5700mah in series or 3.7v and 11400mah if connected in parallel




    Timo2

[snowwolflair]

Hi All

    Quote form Supplier Web Site

           each 3.7V 5700mah so both 7.4V and 5700mah in series or 3.7v and 11400mah if connected in parallel




    Timo2

In a sealed pack like that there is going to be a fuse, thermal cutout or similar in the pack, just as some NIMH have temperature sensors and fuses.  A fuse will blow and stop the "BANG"

[HS93 (RIP)]

where does it say Parellel

PRODUCT ID: Z57002S3P-25
RATED: 
ZIPPY Flightmax 5700mAh 2S3P 25C saddle pack
   
   



Zippy Flightmax batteries deliver full capacity & discharge as well as being the best value batteries in the hobby market today!

Spec.
Capacity: 2 x 5700mAh
Voltage: 2S3P / 6 Cell / 7.4v
Discharge: 25C Constant / 35C Burst
Weight: 154g Each (including wire, plug & case)
Dimensions: 69x46x31mm
Balance Plug: JST-XH
Discharge Plug: 4mm Bullet-Connector
 
 
*2 packs included, as shown in the image.
 
 Capacity(mAh) 5700
Config(s) 2
Discharge(c) 25
Weight(g) 154
Max Charge Rate (C) 5
Length-A(mm) 68
Height-B(mm) 47
Width-C(mm) 31
 
 
 
Update/Add my own data
Customer Data   
Having trouble finding what you want? Try our comparison system. 

peter
 
 
 
 

[HS93 (RIP)]

All

    Quote form Supplier Web Site

           each 3.7V 5700mah so both 7.4V and 5700mah in series or 3.7v and 11400mah if connected in parallel




    Timo2



[quote where was that info ?

peter

[RaaArtyGunner]

I have seen in sites re these comments to paraphrase
"Assumed user is competent and responsible for use"

Which means to me there is a danger and the manufacturer/supplier is giving themselves an out when it will go wrong.
Note, when it goes wrong not if.
These types of warnings etc are used because of probelms that have happened not potential problems.


Also Malcolm's comment below is very very relevant.
No doubt there are others out there with concerns.


"The pro-connecting up group are all, I presume, knowledgeable about things electrical, but they have to bear in mind that many of the members here, while they make models that I can only drool about, really know very little about electrical matters, and, given their skill set, why should they?  There is also the occasional typo where series and parallel get confused, and the occasional person who doesn't know the difference, and, maybe the majority, for whom things electrical are a black art (see the section title). "

Have been following up all the thread references and find comment after comment on Fires and inherent dangers.
Hence why I don't touch them and only use nicads & Nimhs.

[grasshopper]

where does it say Parellel

PRODUCT ID: Z57002S3P-25
RATED: 
ZIPPY Flightmax 5700mAh 2S3P 25C saddle pack

The parallel answer is in the product ID - Z57002S3P- 25, the Z is zippy pack, the 5700 the total capacity 5700mAh, it says in the blurb that it's a 6 cell pack, consisting of 3x1900mah 3.7v packs IN PARALLEL to give the 5700 total (3 cells in each saddle block) and then those blocks are wired IN SERIES to give 7.4volts total.

I know from experience that there are no fuses or cutouts in any of the Zippy hard case packs I use - I opened one up after it failed following a big crash - the heavy pcb used to connect the cells had cracked - a successful repair was made by soldering 2 sections of 20 amp cable along the pcb - had no problems over the last six weeks of racing.

Yes, I do have some electrical / electronics knowledge but I still follow advice and instructions, and am generally cautious.

[snowwolflair]

the heavy pcb used to connect the cells had cracked

Thats could be  the answer why you can parallel these cells.

PCB track has a lot more resistance than the normal special wire, gold or silver tags used with these cells.  Even a very small series resistance is enough to create a voltage difference - enough to reduce the current to a safe level.  

Strapping the PCB was probably not a good idea, only time will tell.

at 150Amps 0.024ohm drops 3.7 volts, enough to compensate for the loss of one cell.  So 0.1 ohms of PCB track would be enough to drop the short current under the max charge rate.

Also PCB will almost certainly act like a fuse at 150A.

[nick_75au]

http://video.google.com/videoplay?docid=3690260570423705609
http://www.youtube.com/watch?v=SQ0SNESIkWk

Congratulations on finding 2 videos on people DELIBERATELY OVERCHARGING Lipo batteries, I can assure you there are many more , I believe the thread is about discharging batteries

So are Nick and you prepared to state on this forum you will back this guarantee of safety with your money to compensate people relying on your assurances when they get injured?

No I am not, nor would anyone, I do not know the competence of the users nor would a manufacturer, I cannot insure for incompetence and stupidity (as seen on those videos you linked to).
All I can do is provide information that is correct as far as I know( note I have backed up my comments with research, links and physical tests and not thrown out alarmist statements)
I'm much more likely to be hit by a car crossing the road, If I listened to statements like yours I wouldn't be leaving the house.

again

A little research, common sense and if you are unsure or uncomfortable then don't do it.

I raise your video with this one

http://www.youtube.com/watch?v=vHj3B5qqjtY

I guess there are not so many of these on You tube, its fairly boring in comparison with exploding batteries

The pack that has been posted earlier is 2S3P which means 3 cells in parallel (3P) then 2 of the 3P in series (2S). this gives a 7.4 volt pack with triple che capacity of a 2S1P pack. The Li-pos I have all have PCB for the cell interconnects, the copper trace is backed up by a heavy layer of solder along the tracks, this is common to most Li-pos. There is no "protection circuit" as seen on laptop and commercial/industrial Li XX chemistry batteries.
 

Cheers
 Nick

[snowwolflair]

I think you are deliberately missing the point. These batteries are working properly, its where one gets a cell failure, something that can happen at any time , the danger begins.

Now find me a video of a charged good cell battary in parallel with a failed cell battery that is not on fire and I will be impressed.

[nick_75au]

I have looked and I cant find one, probably because its not impressive. Have you found one?

Lets see some evidence

Part of my point was people video impressive things, that's why there are so many deliberate attempts to overcharge batteries for the camera, it makes for high impact viewing.
the video I linked to showed 2 batteries with quite different capacities running in parallel a big "no no" in your book yet the results were boring to say the least.

If a cell fails in a parallel pack the good pack will most likely be damaged, that I have no doubt of, I just cant find the evidence that it causes fire and explosion. Nor the evidence that this failure mode is a regular occurrence.

I have not said that there is no danger, anything is possible, like crossing the road.

Would the same thing happen with a standard series pack where one cell had failed do you think?

For everyone else
The biggest danger with Lipos is overcharging or short circuiting the cells and to a lesser extent over discharge or too high a current for the batteries capability, paralleling Li-pos will reduce the dangers of both discharge dangers.

cheers
Nick

[malcolmfrary]

I'm much more likely to be hit by a car crossing the road, If I listened to statements like yours I wouldn't be leaving the house.

Assuming that you know the basics of crossing the road, this is unlikely.  
Obviously cells can be arranged in any way required for a desired result, in the manner of Lego.  But they are not Lego, and those who are not comfortable with electricity or aware of the potential troublesome nature of making an incorrect connection in a power supply need to be considered when advice is offered.  Many more people cross roads, it is normal for those who look both ways first to make it across, it is quite common for those who dont to make it, since the majority of drivers will try to avoid even tourists.  A charged cell, however, should properly be regarded as a primed bomb.  Treated properly its no problem.  Probably.  Mistreated, it can become a problem.
There is a lot of the outlook of "I made it, its my baby, it wont hurt me."  This is the first step to personal injury.
Not leaving the house is one way to avoid a road accident (unless you worry about runaway trucks coming through the front room wall), but knowing enough of the rules and actually following them will usually keep you from harm.
The trend is to pack more energy into a smaller package, this is great as long as it stays put or gets let out in a controlled manner.  The problems arise when it is given the chance to be released in an uncontrolled way.

[grasshopper]

Personally, I think this thread could on forever and is now starting to drop into the territory of 'point-scoring'

Everyone that has posted has done so in the belief that their method is best - and every other is dangerous, over-cautious, safe, lethal and so on.
Unfortunately, anybody reading it has to take some responsibility for their own actions and this is where things could be difficult. If in any doubt DON'T DO IT, if however you take some of the advice on board, do your own study and investigation and then make up your own mind. Read the instructions and follow manufacturers advice.

Where Lipo's are concerned, there seem to be many more 'horror' stories of explosions, fire probably pestilence and plague too - but like Nick has said, lots of things are dangerous but we still do it.

[John Mk2]

Sorry I started it now

[RaaArtyGunner]

Sorry I started it now

Don't be, we all would have missed out on the discussion.
At least it is now clear that lipos are hazardous

[John Mk2]

It was getting a tad heated (Excuse the Pun) in places

[Tombsy]

 I'm using lipo's in my transmitters, receivers and another 10 packs for racing. The only trouble I've had was with a NIMH battery exploding in one of my boats.
Charge lipo's correctly, do not over discharge them and don't use damaged packs.
As I sit with a laptop on my groin that had it's battery recalled for an explosion risk and is so hot it's burning my thigh.  :