tIANci

Cloud ... Its like this ... a motor called Brand B, say its a 35x36 900KV outrunner, rated at 350W and 35A on 3S spins a 12x6-13x6. Now if you want to go 4S on the same motor and use the same prop then your voltage goes up and so does the AMPS. You got more power now of course.

On 4S it may, let's talk theoratically, be pulling 45A, hence too much for the motor. At 45A its now using 652W, more than what the motor is good for. So what you do is to remove the load on the motor, by reducing the prop diameter and/or pitch. So for the same motor you may only use a 10x6 prop.

Why do people do this? Well they want more speed usually. This is when you want to add more cells to a motor that is rated for lesser number of cells.

dashunde

I'll chime in here for a second too...
Remember, a electric motor will always try to reach a specific rpm based on the voltage sent to it.
If you go from 3 cells to 4 any motor will try to turn 25% faster on 4 than it did on 3 cells.
So now that the motor is determined to turn 25% faster you have to reduce the load (prop) so that the motor can reach the higher rpm without drawing too much current (amps) <- which produces heat, and heat creates more internal electrical resistence (slows the electrons) <- which produces even more heat... until something smokes.

Dave..
Your Equinox will work in two ways.
If you hit the button twice while its hooked to a pack and charger it will simply charge each cell individually untill all of them are at 4.2v... or until the charger stops charging based on the total voltage it sees in the pack.
No matter what... When the Equinox is satisfied with all cells being charged equal, it can/will cut off the charger from the pack, thus ending the charge cycle.
Usually it is the later of the scenarios.

The second thing the Equinox will do is a simple no-charge cell balance.
That means you just plug it into a pack and it will balance/equalize all of the cells so that they are all at the same voltage.
It does this by taking a bit of juice from higher cells and moves it to lower cells.
(or maybe it simply dissipates voltage from the higher cells - dont remember exactly)

I think it can also do a passive charge balance (nevermind this, I've found no use for it)

For practical purposes - your doing just fine with the Equinox - just plug it in and let it do its thing.

daveopam

My Feedback: (9)

So i am doing one thing right. Yesterday though it did something different. At the field it took 2 hours for my charger to beep indicating the pack was charged. I hooked up my second pack and 3 hours later it never did beep to tell me it was full. I went ahead and used that pack for a 6 minute flight with no problems. When i got home I hooked up the charge again and 4 hours later it was still charging. SO I'm thinking maybe my flight box battery just doesn't have the poop to charge several packs a day? Or is there some other problem? Should I use my pickup battery to charge the packs?

BTW I used the 14x8.5 prop for 2 flights yesterday. I like it better than the one I cut down. It responds to throttle inputs a little quicker. The vertical is also a little better with it. I am still going to try a 14x7 when I get to the big city. Also your analogy of the 3S to 4S pack was great. Thanks for putting it in a language I could understand.

David

tIANci

David ... charging at 1C should not take more than 90 mins. If your supply battery is low then there should be a error message that input voltage is too low. Let's assume that your power supply is ok then I have seen this problem you face. I suspect its an issue with the balancer. Seen it happen with what you use and also the Triton charger too. One of my pals just changed the balancer recently to another brand and it was ok again. Test it with another balancer and see how it goes. Hope this helps ...

dashunde

Ah yea... use the truck's battery. Here's why..
Even though your charger didn't alert you to a low input voltage your 7ah (I assume) field battery is well below the 12.4v that the charger is trying to push the pack up to.
So the charger starts "transforming" amps into volts... It bumps up the voltage and sacrifices amps delivered to the pack.
For example: the charger will take 11volts at 1amp from the battery and turn it into 12.5v at a .5amp rate - meaning, that if your charging a 2.0amp (2000mha) pack at .5 amps it will take 4 hours (2.0 divided by .5 = 4hr)
Also, if you do a bit of quick math, your (7000mha) - aka "7ah" sealed lead acid (SLA) battery will charge a 2000mha pack about 3.5 times.. but in reality, as the available amps in the SLA drops, so will the voltage, so the third lipo recharge will take awhile.
A car/truck battery, when new, is vastly superior to the little SLA... but be sure to leave enough in the truck to get home!

Important fact - Any given charge voltage MUST exceed the pack voltage - the additional voltage is what "pushes" juice back into the pack, the amp setting is there to determine how hard (Rate) the power is pushed back into the pack - Its simply the reverse/opposite of draining the pack, only these lipos recharge at about 1/25th of their discharge ability.

A standard field charger will use a singular 12v source, convert that into a proper charge voltage and amp rate, and then sends it onto your Equinox to be split, managed, and balanced amongst the individual cells.

But there is a better way...
If you use a balance charger (a charger that charges and balances all in one unit) you can get much better results when charging from a drained SLA.. here's why:
The little CellPro 4s is essentially 4 chargers in one unit with a processor that controls each charger individually.
The trick here, is that since each little charger is responsible for only reaching 4.5v, dropping below the 12v threshold on the SLA doesn't matter much.
See... each little charger has access to far more voltage that it really needs to top off each individual cell.
It will keep going as long as there is enough Amps left in the battery to sustain the desired charge rate (amps) across all chargers & cells.
This is how the little CellPro manages to charge a 14.8v 4cell pack at 3amps with only 11v available - it treats all 4 chargers & cells as individuals.
At least this is how I understand it... could be wrong on a few points, but..

Uh... Note:
You may also want to check your Triton to be sure it is set at 2.0 for your charge rate, if you fat-fingered the setting to, say, 0.5... that will also take 4 hours.
Just a thought.

About your prop..
Careful with that 14x8.5... keep an eye on pack discharge rates/amp draw.
It produces more thrust because:
a) It is drawing more power, plain and simple
b) Because it is still shaped exactly as the engineers at APC designed it to be - in other words, it is still efficient and "correct" from a design standpoint.

When you cut down or reshape a prop you are removing a lot of very subtle design factors that enhance performance and efficiency.
Additionally, most of the static thrust a prop produces comes from the tips... so if you remove a bit of the tips you are removing thrust.
You may find that a 14x7 produces the same static trust as a 14x8.5 without the excessive current draw and delivers longer run times.
The 7 pitch prop just wont be as fast as the 8.5 pitch.

Ok... my fingers are tired... sorry to be so longwinded. [sm=47_47.gif]