The basics of electrics - AKA Electricity for Dummies

[daijoubu]

Originally Posted by geoavia

Just realised that, the problem I belive will arise is: If I manage and charge 6s packs half by half, than I will get two charged and balaced 3s packs connected in series in one brick, but this can not guarantee that any cells from different halves will be in balanced voltage range.

So probably this is not a wery good idea of chargind 6s cells half by half, even if charger and pack allows it. Huh, think, time to look at larger chargers...

Does it? An integrated balancer will terminate the charge when all cells are 4.2v +/- 0.01v or so.

[daijoubu]

Originally Posted by geoavia

Thanks for precautionary words I know about lipo safety, and won't do anything that potentially may cause damage. that's why I'm asking.

You're welcome, not everyone reading this thread knows though. I met a guy at the field on Saturday who started telling me how he cut his lipos open and was testing them out. He wanted to open a pack, cut it up and re-assemble it as a smaller lipo to fit in different planes. The only thought in my head was "Oh my god, get away from me! Put your batteries back in your case and keep them away from my car and helis!"

[minskie]

Yawn, ho hum.

Never realised how boring electricity and electronics was.

I just want to plug n fly

Glad I never studied to become an electrician. I'd have fallen asleep in class every day.

[odam2k]

Originally Posted by daijoubu

You're welcome, not everyone reading this thread knows though. I met a guy at the field on Saturday who started telling me how he cut his lipos open and was testing them out. He wanted to open a pack, cut it up and re-assemble it as a smaller lipo to fit in different planes. The only thought in my head was "Oh my god, get away from me! Put your batteries back in your case and keep them away from my car and helis!"

Hmm, I've taken two packs that had bad cells, cut them apart, and used three good cells to make a 3S pack from them. They were identical packs... Nothing wrong with that... I've also cut the tops open to resolder the balance plug wires back on when they break off. In fact, I'm considering taking 4 3S packs and making 3 4S packs out of them...

[aerocal]

Originally Posted by odam2k

Hmm, I've taken two packs that had bad cells, cut them apart, and used three good cells to make a 3S pack from them. They were identical packs... Nothing wrong with that... I've also cut the tops open to resolder the balance plug wires back on when they break off. In fact, I'm considering taking 4 3S packs and making 3 4S packs out of them...

I think a clarification of "cut it apart" is in order.Ive also modified quite a few LiPo packs.They are all packaged a bit differently.Generally the seperate LiPo cells are encapsulated in their own airtight shrinkwrap type membrane with the leads both on one end.Airtight being the key part of this package.Multiple cells are stuck to each other usually with some kind of double sided tape,adhesive,etc.Then a piece of pcb(printed circuit board) the size profile of the end of the pack is positioned on one end for a solid place to connect leads and provide strain relief to lead ribbons LiPo cells use.Then once everything is in place the entire assembly is shrink wrapped again further protecting the cells and connections.Some dont have an outer shrink wrap and have like a fiber tape wrapped around them.So Id say "cut it apart" is better defined as "cut apart outer wrapping".Any and or all of the secondary package(outside shrink wrap or tape) can be removed to expose the cells and connections.Two main precautions are to never puncture the membrane,case,plastic wrap on an individual cell and to excercise higher than usual care not to short the leads together once they are unsoldered.If the cell membrane/case is puntured an oxygen is allowed to get inside its done and there is the very real chance it may spontaneously combust.Maybe in a few minutes maybe hours tomorrow who knows?Punctured LiPo cells very very bad.The leads on them are mostly all a flat ribbon type lead and are many times plenty long enough to easily come together when loose.Even if they just barely touch there will likely be enough current to make them spot weld themselves together in a short and get very hot and possibly start a fire or on fire or at best ruin the cell or cells in a matter of seconds.Toughest part I found is serperating the cells themselves without stretching or poking a hole in the cell.Most seem to use something like servo tape.I found that a credit card kind of sharpened works good.Gentle pressure and work the card in the gap slow steady pressure.I ruined a few using a knife too.Obviously this is something that requires more care than making Ni-Cd packs but with a bit of extra care and attention can be done quite safely.Be aware.Be prepared for eventualities.It is what it is.

[odam2k]

Exactly... yes, good definition of "cutting apart" - seperating the single cells... he he

I find the cheap packs don't have the pcb on the top, and the balance plug wires easily come off the tabs. I've started folding the balance plug wire over the top of the pack and taping it there now, its shorter, but there is no strain on the solder joints any more... I have a bad habit of picking them up by the wires

[Tom.C]

Originally Posted by HFG

One thing that is really wrong is your discription of a watts "...Watt is a unit of work done over time".

''Watts'' just tells you how many amps and volts a particular device needs in order to function, i haven't heard anything about time when working with the term ''watts''.

''Watts'' is just the correlation between Amps and volts, VxA=watts

[DominicD]

I am somewhat familiar with electronic theory.

[ENDO1]

Originally Posted by alex_p_kiel

Volts in the electromotive force in a current or how fast it is moving. Amps is the electric potential or ammount of power. Watts is is volts x amps. Ohms is electrical resistance. From my own calculations, a "C" is about 2 or 2.1 amps. A miliamp is one-thousandth (0.001) of an amp. I don't know if I am forgetting anything.

Originally Posted by Tom.C

''Watts'' just tells you how many amps and volts a particular device needs in order to function, i haven't heard anything about time when working with the term ''watts''.

''Watts'' is just the correlation between Amps and volts, VxA=watts

"From my own calculations, a "C" is about 2 or 2.1 amps"

[rcboosted]

nm

[LowOreo]

Im kinda confused on how they calculated the 5 minutes to kill the battery at 1000 mah and 12C. Anyone wanna help explain that with maybe at 2200 mah at 25C.

[spork]

Originally Posted by LowOreo

Im kinda confused on how they calculated the 5 minutes to kill the battery at 1000 mah and 12C. Anyone wanna help explain that with maybe at 2200 mah at 25C.

Sure, I'll take a crack. The battery capacity is 1000 mah (that's 1000 milliamps for 1 hour - at its rated voltage). If you think of it as a jug of water, the capacity is how much water is in the jug.

12C refers to the rate the water can flow out of the jug. 1C is sort of short-hand for "1 capacity" which is sort of shorthand for "1 capacity in one hour. But keep in mind, this is a RATE of flow. So 12C would be 12 times that rate. This would suggest you could dump 12 times the battery's capacity in one hour. But of course the battery doesn't *have* 12 times its capacity. It only has 1 times its capacity (by definition). But 12C is still 12 times the *rate* of 1C. What this means is that you'll dump the entire battery's capacity in 1/12th of an hour - or 5 minutes.

So let's look at your case of a 2200 mAh battery at 25C. To know how fast you can dump the entire contents, it doesn't matter the capacity of the battery. Just the "C" rating alone will tell you that. If it's a 25C battery, you can dump the entire battery in 1/25th of an hour - or about 2.4 minutes. Since you can dump 2200 milliamps for one whole hour, you would dump 25 times that current (or rate) over the 2.4 minutes. So you'd be putting out 55,000 milliamps (or 55 amps).

[TJinGuy]

I like the "jug" analogy, thanks for that.

[LowOreo]

ah gotcha. thats what i thought but just wasn't sure. i appreciate the help.

[freewheel510]

The problem with using water "pressure" and water "flow" to explain potential (voltage) and current (amps) is that many people who don't understand electricity don't understand water either.

[airnoob]

I'm confused. Why is a battery's mAh rating featured so prominently though it ignores the voltage.
Wouldn't WattHour be a more accurate measure of what a battery can do? Hope the question wasn't too dumb :o

[TJinGuy]

Originally Posted by airnoob

I'm confused. Why is a battery's mAh rating featured so prominently though it ignores the voltage.
Wouldn't WattHour be a more accurate measure of what a battery can do? Hope the question wasn't too dumb :o

In terms of work done, yes Wh would be a better rating to display but that is not what is important with packs. What is most important is Ah. This the bases for figuring out discharge rates, charge rates, sizes, etc. If you only advertised the Wh of a pack instead of Ah, then the user would have to do some math in order to determine all the pertinent info themselves.

[airnoob]

Thanks, Chris

I think I've finally got my head wrapped around the basics.

Now, if I can only hover inverted...oops...that should be a new thread.

[carlocivicsi]

can anyone tell me the basics of parallel and series.

im new at this and i would love to save money not buying new batteries if i can mix them together. for example i bough a new trex 500 esp and i have 6 3s 11.1v 2200 mah and the trex requires 6s 22.2v and at least 2200mha. so what can i do with this batteries?? thanks.

[spork]

Originally Posted by carlocivicsi

can anyone tell me the basics of parallel and series.

im new at this and i would love to save money not buying new batteries if i can mix them together. for example i bough a new trex 500 esp and i have 6 3s 11.1v 2200 mah and the trex requires 6s 22.2v and at least 2200mha. so what can i do with this batteries?? thanks.

When you connect packs in series you add the voltages, but the capacity remains the same. When you connect them in parallel the voltage stays the same and the capacities add.

So you can connect two 3S packs in series to get one 6S pack. That will give you a 6S 22.2V with 2200 mah capacity. And you're good to go.

To add them in series you'll connect the red wire from one pack to the black from the other. The remaining red and black wires will be your 6S outputs.