The basics of electrics - AKA Electricity for Dummies

[spork]

Originally Posted by celter

The Volt would be the height difference between the water level in the tank and the end of the hose. A bigger tank would not increase the pressure (Volt)

True enough, but I that's what was stated in the PDF file, right?

To the extent you can use the water analogy (which I think is a pretty fair analogy) the PDF file looks accurate to me.

[supergenius]

Originally Posted by HFG

The C rating only determines how much maximum current your battery can supply. You motor determines how much current is drawn. Your esc doesn't care the least bit. If you motor doesn't need more then 10C your new 20C pack won't make any difference. If you motor was trying to draw more then 10C with your old pack your new pack will be able to provide the current your motor demands. As an example lets use a 3S 2100mah pack on a 35A esc.

35A / 2100mah = 16.7C max

which means going from a 20C to a 25C lipo is a big waste of money.

How do I calculate the amount of current my motor will draw?

[DominicD]

Been way too many years since i had to fake an interest in power electronics, sorry.

[spork]

Originally Posted by supergenius

How do I calculate the amount of current my motor will draw?

That's kind of a tough one. As you put more and more load on the motor it will draw more and more current. Finally you can stall the motor. At this point it will try and draw current governed by V = I * R where V is the input voltage, I is the current you're looking for, and R is the resistance of the windings. The resistance of the windings will be based on the material (probably copper), the length, and the guage of the wire.

I don't know if many motors give the stall current in thier specs, but you don't want to be stalling the motor anyway. Many motors seem to publish the max current (which is as much as you want to be pulling to not burn out the motor).

[supergenius]

Can anyone recommend some good batteries in the 2200mah 20C range?

[wecoyote]

When you are talking "20C, 25C etc" you are looking at a multiplier of capacity that the battery can handle in discharge.

Lets look at a 3S 1P 20C 2000Mah LIPO battery:

3S = 3 cells in series = 3.7V x 3S = 11.1 Volts (series increases voltage but does not affect capacity)
1P = 1 parallel = 2000Mah (2P would = 4000Mah etc.) (parallel increases capacity but does not affect voltage)
20C = 2000Mah (2 amp hour) x 20C = 40,000Mah (40 amp hour)

So as you can see that that "C" rating means that the battery can handle a 40 amp discharge rate without damage.
If you went with the same battery in 25C then it could handle 50 amp discharge rate without damage.

[supergenius]

Ok, that helps.

So, right now, I have a 1S 11.1V 1200mAh 10C pack, and a 1S 11.1V 2300mAh 10C pack. The 1200 gets is pretty hot after each flight, but it charges pretty well. One of the cells on the 2300 pack started to swell during charging, so I stopped using it.

My helicopter has a 3500kv brushless, and a 30apm speed-control. It's a 400 sized heli. I'm thinking the 1200 pack is getting hot on discharge because the heli is pulling up to 23 amps out of it, and the pack can only handle a 13 amp discharge? (not entirely sure if my math is correct)

For the 2300 pack, the heli is pulling up to 13 amps out of it, but, the battery can handle up to 23 amps? What would cause the 2300 pack to swell during charging?

[wecoyote]

Originally Posted by supergenius

Ok, that helps.

So, right now, I have a 1S 11.1V 1200mAh 10C pack, and a 1S 11.1V 2300mAh 10C pack. The 1200 gets is pretty hot after each flight, but it charges pretty well. One of the cells on the 2300 pack started to swell during charging, so I stopped using it.

If it's 11.1 Volts and only has 3 cells then it is 3S 1P.

Originally Posted by supergenius

My helicopter has a 3500kv brushless, and a 30apm speed-control. It's a 400 sized heli. I'm thinking the 1200 pack is getting hot on discharge because the heli is pulling up to 23 amps out of it, and the pack can only handle a 13 amp discharge? (not entirely sure if my math is correct)

Close, 1200 (mah) x 10 (C) = 12000 so it can only handle a 12 amp discharge.

Originally Posted by supergenius

For the 2300 pack, the heli is pulling up to 13 amps out of it, but, the battery can handle up to 23 amps? What would cause the 2300 pack to swell during charging?

Yes a 2300Mah 10C pack can handle a 23 amp discharge.
What amp rate are you charging at? It should be 2.3 amps. (charge at 1C)
Also what brand battery is it? It might just be a bad battery.

[wecoyote]

Originally Posted by supergenius

Can anyone recommend some good batteries in the 2200mah 20C range?

That is like asking if Ford or Chevy is best.

With battery chemestry advancing so rapidly it is hard to keep up with which is best.

My personal preferences are in this order:
1. FlightPower
2. Thunder Power
3. Air Thunder
4. Kong Power
.
.
.
somewhere down here is Align.

[supergenius]

The batteries and my charger are all walkera brand.

So, I'm ruining my 1200 pack, right?

The 2300 pack has a tiny hole in the one of the cells (have to use a magnifying glass to see it). It's from when I landed in a tree and tried some 3D from the top of the tree to the ground... The hole is in the cell that's swelling, so I'm thinking it's the cause for the problem.

To up grade, I was looking at this combo:
http://www.readyheli.com/ProductDeta...225%2D3charger
Any suggestions?

[wecoyote]

I've been looking at that myself.
Finless is doing a great comparison on them here:
Finless battery comparison

I'm waiting with baited breath for the results to see if they hold up in the long run before I buy.......HURRY UP Finless! LOL

That is a LOT of flights to make for this test.

[seanh]

Why is the 2300Mah battery puffing? if it's a walkera that would be why. I've got several walkera batteries that have puffed just sitting in the garrage. They were fine at last flight...partially charged for storage. A month or so later, with no draw or charge they are puffed No more walkeras for me. stick with flitepower, Thunder power, airpower, kong power

[SonGunnar]

Well, I see this thread is old but don't know where else to ask.

1. I have a 70 Amp, 2-4 Cell lipo Scorpion ESC, and a Scorpion HK3026 motor, 1210 KV.

Can anyone tell me if 2 4, Cell, battery packs were run in parallel, would the 4 Cell ESC, recognize the combo as 4 Cells?

I would think operating time should go up, if the esc would work.

2. Will the motor and esc work with (1) Zippy 2500 or 3500 Pack without cooking the works (maybe governor mode set by ESC)?

The Heli I am looking at is rated for 6 cells 1200 kv but is sold with 6 cells 1100 kv.

I am thing that weight savings may justify a higher pack rating, with lower cell count?

Thanks for any help.

SG

[grig]

the more voltage, the less amps taken by the battery pack?

[DominicD]

READ THIS, should clear some of this up.

https://www.helifreak.com/showthread.php?t=64727

[geoavia]

Sorry if asked already but didn't find via search...

I have charger that has support for only 1-5 cell lipos so till now i'm stuck with 3s packs only for my trex 450 and some planks.
I ordered trex 500 recently (wow!) thus will be using those 3s packs in series but I'd liked to try 6s single brick packs.
So just looked for this pack:
http://www.helidirect.com/product_in...oducts_id=7192
and noticed that it has 2 3s style balance plugs and also TP connector. Does it mean that I can charge it half by half with my 1-5 cell charger (one 3s part first than another)?

[wecoyote]

Originally Posted by geoavia

Sorry if asked already but didn't find via search...

I have charger that has support for only 1-5 cell lipos so till now i'm stuck with 3s packs only for my trex 450 and some planks.
I ordered trex 500 recently (wow!) thus will be using those 3s packs in series but I'd liked to try 6s single brick packs.
So just looked for this pack:
http://www.helidirect.com/product_in...oducts_id=7192
and noticed that it has 2 3s style balance plugs and also TP connector. Does it mean that I can charge it half by half with my 1-5 cell charger (one 3s part first than another)?

sorry but the answer is no.
The ballance leads are in two seperate plugs BUT the power lead is one single and that is where the charging happens.

[geoavia]

Hm so neither 6s packs can bi charged via balancer plugs only? I thought chargind by additionally connecting power wires are for high power charging. Than why I can charge my 3s packs via balancer plugs only?
3000mAh pack usually charged at 3A (1C), and I belive balancer wires can easily handle this current. Why I can not charge separate cells (even one by one) if I do so on 3s packs?

[daijoubu]

If you know what you are doing, yes you can charge through the balance plugs as two separate 3S packs. You can also short the pack or wreck your charger. Check it out thoroughly. If you set fire to your garage, don't come back mad at me.

You will need to make sure your charger can charge through the balance taps only. Neither of mine can. I think the cellpro series can and some of the cheaper lipo chargers do.

[geoavia]

Originally Posted by daijoubu

If you know what you are doing, yes you can charge through the balance plugs as two separate 3S packs. You can also short the pack or wreck your charger. Check it out thoroughly. If you set fire to your garage, don't come back mad at me.

You will need to make sure your charger can charge through the balance taps only. Neither of mine can. I think the cellpro series can and some of the cheaper lipo chargers do.

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.

Yes my charger allows charging via balancer only. Actually I have Simprop Intellisence charger (that I bought far before I decided to go to larger packs) using in couple with equinox balancer (coz charger itself has no balancing plugs). Quite performing configuration, had no problem of chargind TP, Cong and also some cheap LiPos as well up today.

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...