eat2muchrice

Success! Well so far.
I figured out a way to rebalance your 2s batteries without the need to buy expensive chargers. I’m not sure if this has already been done but I did several searches on google/yahoo/forums and came up with nothing.
I’ve been flying with my two stock e-flite batteries for months now and have about 200-300 flights through them using only the E-Flite and Venom charger/balancer. I used to average about 8-9 minutes of flight per battery until just this week when I started to notice my flights dropped down to 5-6 minutes. So I took out my Volt meter and checked each cell, sure enough the cells were unbalanced on a full charge. One cell read just below 4v’s and the other was at 4.2v’s.
I spent a whole day trying to get them rebalanced with the chargers by unplugging and replugging them in, I even slightly drained them and tried milking the charger but they won’t level out. So this is what I ended up doing and testing,

1. Tested each cell on a full charge with a volt meter
2. Plug a 5v LED light onto the stronger of the two cells (needs to be at least 5v LED, anything else will fry. I think blue LED’s can handle higher voltage)
3. Let it drain that cell for about ……….5 hours (every 20-30 minutes check on it with your volt meter)
4. Once the cell has level out even with the other, then just recharge it on your charger. It should now charge balanced.

I still haven’t figured out the long term affects and have only tested it twice. I’m getting my full 8-9 minute flights back and the cells seem to be keeping balanced after each dis/recharge. I’ll see how long it last, and hope others will assist me in this testing and keep everyone posted on it.

Please look closely at the pictures below and take note on all the arrows to see how to test each cell.

rikybob

I will give it a whirl tomorrow.......cool!

Rikbob

soloboss

I still think that eat2muchrice is a goofy name. But you seem to be nearly brilliant, so I suppose I can't pick on you too much. That was a really good idea - and simply brilliant in it's simplicity!

Good work. The Collective thanks you.

Soloboss

rikybob

Well..........put a DVM on my offending lipos as well as me good DN's and found that oddly enough they measure the same (basically) hmmmmm......now keep in mind DVM's as nifty as they are do not put any kind of "load" on the thing that is being measured. Whereas the old school analog meters do. Me thinks I will follow this further as the batts die. Good work and direction!

Rikybob

eat2muchrice

Its the Collective that the thanks should go to. Just 5 months ago I didn't know cr@p about anything dealing with rc helicopters, I didn't even know what a balance plug was . It was everyone in this forum that has tought me the ways of the heliforce.

rikybob

Its slightly insidious. Much like one would imagine a heroin addiction would be. I see therepy in my future

Now you have to excuse me. I have to go stare at the Esky forums at the single rotors. Help!


Rikybob

soloboss

We are all students.
We are all teachers.
We are the Collective.
You have been assimilated.

gnd2

FYI
http://led.linear1.org/myth-of-the-5-volt-led/

LED's should always have a resistor in series, whether it be internal (rare for the type of LED you seem to be using) or external.

Carljw

How do you ck the ballance on a 2cell and a 3 cell lipo. I have a volt meter buy dont know what leads to but the red and black wires to . I use it on the end that plugs into the hile to see if it is fulley charged or how much it is discharged. I guess you use the white plug that goes into yhe charger buy what wires do you use, on the 3cell i have a black yellow blue and red. and on the 2cell i have a black abd two red on the white plug.
Carl

rikybob

Carl,

Look closely at rices photos........he has arrows pointing on the two cells...........for the three I cannot help.

Rikybob

Carljw

I think I figured it out. on the two cell my 3 Mega Power 4.15-4.17 next two 4.20-4.22 the 2 cell E-flite reads 4.02-4.01
My e-flite 3 cell 4.15-4.16-4.16
I use the e-flite charger that came with the CX2 to charge the CX2 batterys and the CP Pro batterys.
Carl

eat2muchrice

Its a "expensive" cheap Radio Shack LED. They come without any resistors.

eat2muchrice

ooo a digital meter . You can fine tune your batteries very nicely with that.

eflitemaniac

Does anyone have a recommendation as to when they would balance with this method? For instance, when one cell is +/- 0.1 volts different than the other? With the DVM my cells read 4.17 and 4.21 at full charge using eflite stock charger. Is this close enough?

eflitemaniac

eat2muchrice

The thing about useing an led that it very very slowly drains one cell, so you if your batteries are off just a little then go ahead and fine tune them. If you wait for them to really become unbalanced then you'll have to babysit the battery for hours and hours one of my batteries took me over 8 hours just to drain .15v's.
One day I'll get a digital multimeter and you bet my batteries will be near perfect.

gnd2

then you shouldn't be shorting it across the battery terminals like that.

Actually, if it really takes 5 hours or so just to "balance" out the cell, it must not be drawing that much current so maybe it's OK, but in generally you shouldn't use diodes without some series resistance.

eat2muchrice

Lets just say I fired 3 different LED bulbs doing this test.

gnd2

Aha, see, told you! Put a resistor in there and you'll stop frying them. Look at the current rating of the LED, use V=IR to determine a value for R that gives you I less than the max rating. Actually, you don't even need the diode, a resistor alone will do just fine, but stuff that lights up is always cool [8D]

Or you could just get a blinky which will do the same thing for you automagically for only 25 bucks

pirellip

This is what I use:

http://www.rctoys.com/rc-toys-and-pa...ERS-POWER.html

I originally purchased it for my TREX, and use it every time I charge (I have it plugged in as I'm charging)

It will auto balance the cells if they are more then 0.005V out (no, 0.005V isn't a typo)

By doing this you get the best possible charge and your lipos will last the longest.

Not a bid deal when you can get DN lipos for $15 for your CX2, but much more important when you're using $100 batteries that I have in my TREX...

Phill86

hi.
I balanced mine using a computer fan with blue led lights.
It only took 10 mins to bring it from 4.23 down to 4.11

The question I would like to ask is after i flew my heli to flatten the battery ready for its charge I took another reading. insteasd of them being the same like you would expect, the red lead cell was 3.71 and the black lead cell was 3.49 why would they discharge differnt.?
Im going to charge it an see if it rebalances.
Will post back.

eat2muchrice

yes, using a computer fan would is more idea then my stupid LED and waisting 4-5 hours.

Did you recharge the battery after you balanced it? test and recharge it after you balance, then test it again after a discharge flight.
My batteries seem to discharge fine, but one cell losses power when i store it a couple of days.
Maybe one of your cells is starting to die and you just can't fix that....well not to my knowledge.

Phill86

hello.
the 1st battery I equalled out then used, it now is not equal
The 2nd battery I equalled out then recharged and it is equal. need to fly then recheck.

Going to try redoing bat no.1 and see what happens when I charge after a equal....then a fly.if that makes sence?

fingers crossed.

Coyote64

Strange how baty 1 went out of balance after first flight, lol yeah it makes sense to balance first then charge

I would be interested to see how the balance is after you do this, balance first, charge, then check balance again to see if charger could not keep balance when charging

Phill86

After the balance and charge both batteries are fine. all equal.
When I have used them neither battery is equal. maybe they are failing.
At least the charger is working ok, as it can charge them equal.
Going to try re balancing again just to make sure.

Could the motors be failing as it is always the same cell that is lower. (red lead on both batteries)
Would a failing motor just not work or do then slowly fail?

Coyote64

It depends really on what part of the motor is failing, ie stator etc

The current draw should increase as a motor starts failing, the power will decrease noticably as well, which might knock battery cells out of balance.