Charge to 4.1v/cell
 

This is all from Battery University. I will look for more technical data to support this, but this is inline with our thoughts about not storing batteries fully charged.

Charging to 4.1v/cell reduces high voltage stresses and can prolong the number of useful cycles by 50%-100%. With the shape of the discharge curve, there should be next to no impact in F3A performance. Maybe you lose a touch of initial burst, but you get into the flat of the curve sooner and have constant power throughout the flight.

Some small test data from Powerstream - says charging to 4.1v will double the cycle life of the battery.
http://www.powerstream.com/lithuim-i...ge-voltage.htm

Some stuff from Battery University, says the same thing:
http://batteryuniversity.com/learn/a..._ion_batteries
http://batteryuniversity.com/learn/a...ased_batteries (scroll down to Table 4)
http://lancair.net/lists/lml/Message...y%2520Life.pdf says more of the same, but talks about how to alter the charger to get the proper effect:

RE: Charge to 4.1v/cell
 

That's good info. I'm going to modify the presets on my PL8 and do some test flights!!

RE: Charge to 4.1v/cell
 

Me too. Small change with potentially a substantial impact. Easy enough to do on the iCharger 1010's. Nothing to lose really.

RE: Charge to 4.1v/cell
 

Actually, need to review charging requirements. Charging at constant current is different than charging at constant voltage. Ifound in the iCharger that if you change the max charge voltage to something other than 4.2v, it switches from constant current to constant voltage (which seems that you can't charge at a specified 'c' rate). Still need to learn about this.

RE: Charge to 4.1v/cell
 

Ok but let's not forget that the goal of flying electric...(for me anyway) is so I don't burn one gallon of high nitro fuel every time I take my 2m plane out for a day...and 30 minutes to clean it up after the day....so I see my batteries as being quite a bit cheaper for me then running Cool Power fuel.....so I'm going to go only so far to baby them....after all they are to a certain extend an expandable item. I'm not even talking about the saving on engine/pipe mounts price..... and repair parts.....

Anybody else think this way???

RE: Charge to 4.1v/cell
 

Yeah, I agree..I just fly the things and throw them in the box to take home...I`m sure that`s not text book. It works for me, but different strokes for different folks...you can baby them all you want and sometimes they just go bad....but that is a good tip for guys doing that.

RE: Charge to 4.1v/cell
 

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Yes, but electric also has many, many other advantages over fossil fueled alternatives. I have done nothing, none, nada, zero, zip maintenance of any kind to my Advance 30-10 motor or ESC for over two years. When I contacted the retailer about what I need to do, he told me that NOBODY who owns one has had to do ANY maintenance or adjustments to theirs. Don't think I could say that about the YS motors. The servos in the plane are the original and still installed where they were three years ago. Never a deadstick. Never a backfire. Can stop the prop on the runway and still taxi back. No starter to charge / carry. No glow driver. No glow fuel pump or battery to charge. Same power each flight. No charging receiver batts. I could go on . . . . so for me electric is much more than saving on the cost of glow fuel. My flying has improved 100% since I spend more time as pilot than YS maintenance technician.
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Anyway, to your quote. I agree that the batteries are there to serve me, not the other way around. However, if I can do something as simple as changing a preset in my charger and get the same performance as before while making the mule live twice as long, I don't see why I shouldn't. If I can definately tell a difference after changing the charge termination point, then I won't hesitate to go back to 4.2V.
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RE: Charge to 4.1v/cell
 

Joe, I notice the references you listed are for Li-ion batteries, not Li-poly. I believe the chemistry is different, li-poly cells have a higher power/density. I wonder if the information on your references apply to li-poly cells as well as li-ion. If so, I think it would have come up from the heavy users and li-poly testers on the 'other' RC forum.

Woodie

RE: Charge to 4.1v/cell
 

If you read through carefully, it says the same applies for lithium polymer and other lithium based batteries.

RE: Charge to 4.1v/cell
 

Not sure that this is relevant to Joe's OP, but all of us are charging our LiPo's with sophisticated, software controlled chargers where the designers have no doubt accounted for the (then) best way to balance, charge, discharge or store (depending on the program chosen) each "chemistry." When compared to simpler chargers that may accompany consumer electronic devices, I wonder if the issues raised in the articles continue to apply to the way we are charging on our iChargers, FMA's, PowerLabs, or any high-end charger of your choice?  Heck, our chargers probably cost more than the most consumer electronic devices where LiPo/LiFe charging is perhaps not as sophisticated or optimal.  Like I said, not sure this is relevant...<div>
</div><div>OTOH, pattern is a competitive sport so I don't see myself launching too many flights on a short charge, LOL!  I do see many pattern pilots charging their packs not too far in advance of their flights, and returning them to storage voltages shortly thereafter, and that may be the best we can do given the need for max performance in the air.  Most brands of packs seem to last for hundreds of flights when well cared for by pattern pilots, and while we all have our favorite brands, on the whole, LiPo quality and longevity have greatly impressed me, at least for those who take good care of their packs.  Heck, even my oldest packs are still plenty strong for practice flights; my newest ones are favored for contest days. There is also the risk that by departing with a short charge, that we may inadvertently stress a cell during a spirited flight; not to mention safety concerns about having less flight time than one used to.  Thoughts?  Cheers!</div>

RE: Charge to 4.1v/cell
 

I think 4.2V is 4.2V no matter what charger gets you there. If we are not storing our batteries charged, it would seem that we believe a battery topped at 4.2v/cell will not last as long. And the difference in flight time between a 4.2v/cell and a 4.1v/cell would minimal, especially with the newer motors and batteries.

It said somewhere in the articles that people use lithium batteries because they want the most amount of power for the longest run time. So companies make chargers that charge to 4.2v to accomplish that and longevity of the battery suffers.

I thought there would be more receptiveness to this. I personally would prefer not having to buy fresh packs every year or two if I can avoid it. Doubling the life expectancy of my batteries for a simple change that I probably would never notice performance wise sounds like a no-brainer.

I will watch my charger at the field next time and see how many ma it takes to go from 4.1 to 4.2v. My thought is that I land usually at 3.83v/ cell and can afford an extra 0.1v, and I hear people using ~3200mah per flight out of a 4500 or 5000 pack, so should be able to afford a small amount of capacity.

Last thought is that the impact seems linear. Charge to 4.1v/cell doubles life expectancy. You can charge to 4.15v/cell and gain 50% life expectancy which still sounds good.

RE: Charge to 4.1v/cell
 

Hi Joe,
Approx 475mA - nearly 10% of total capacity or 12% of the 4000 usable (80% guide) in a 5000mAh pack.
'Undercharged' by this much would/could lead to extra occasions of over-discharge - choose your poison.

Brian

RE: Charge to 4.1v/cell
 

It probably will put the pilot in competition disadvantage if each cell is charged below 4.2v when the motor is designed for a fully charged 10s pack.

A separate discussion point: it would be something if the energy can be harvested and put back into the batteries during downlines.

RE: Charge to 4.1v/cell
 

The Military overhere loads their lipo`s to 4.15 a cell.

Gr Frank<br type="_moz" />

RE: Charge to 4.1v/cell
 

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Your batteries are only at 4.2V for a few seconds once you start running the motor, then only at 4.1V for a short period after that. I'll try to post a Castle data log showing pack voltage during a flight later this week if this thread is still alive.
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<br type="_moz" />

RE: Charge to 4.1v/cell
 

Your batteries are below 4.2V the minute you take them off charge. I think people read into this stuff too much. Batteries have just so long a shelf life. Just charge them as usual, don't go beyond 80% discharge and have fun. There are no perfect lipos. I've even had TP's go bad. But at least they were replaced for free with the warranty they provide. The way we use these batteries they are really only good for two seasons and maybe good for practice packs if you go beyond that. If I get at least 100 cycles out of a set of batteries, that's good enough for me. Just think of what it costs to run 30% nitro in a YS that beats the hell out of your airframe and radio gear. I still think it is a better deal even if you pay the premium price for Thunderpower packs. By the way, I take the results on a Castle data logger for what there worth. And that is just trend info. I don't hold much truth in the acuracy of the data it provides.

RE: Charge to 4.1v/cell
 

Another way to look at it:  A typical flight starts at 4.2V per cell and ends around 3.8V per cell, give or take for wind, flight time and/or traffic avoidance.  The difference there is 0.4V of usable eMF in the battery, the potential energy that our motors convert to the kinetic energy that moves the airplane.  Now, if I start a flight at 4.1V, I only have 0.3V of eMF to apply to the motor: That's 1/4 less eMF than I had before when starting at 4.2V. It stands to reason that flight time will decrease given the same flight profile; and I risk asking for too much from the cells if I attempt the same flight, potentially stressing them on the low side. With just a precious few minutes of flight time on a full charge to 4.2V, I really don't see much value in departing with less eMF than possible, as a matter of choice.  But that's just me: I like to have a full tank of gas at the start of each flight. Cheers!

RE: Charge to 4.1v/cell
 

I agree don't read touch much into it just fly he thing.... Like most of you guys I got lots $ in my recharging stations......

RE: Charge to 4.1v/cell
 

What you guys need is a step up converter/regulator so that you get 42 volts for the whole flight. A step down converter/regulator would be better but I think the rules would prevent you from running a higer voltage pack before a converter, even if the ESC was only being supplied by 42V.

If the converter were integral to the pack then you could possible get away with it?

RE: Charge to 4.1v/cell
 

Brian, what was your procedure for measuring the 475 mAh? It would seem that you'd need to start from a specific known charge, maybe the storage level, and first charge to 4.2 and then repeat the process charging to 4.1. And then you might want to repeat the test a few times to see if you always got the same result.

Jim O

RE: Charge to 4.1v/cell
 

Hi Jim,
We got two different chargers ; A cellpro PL8 and an i ??? 4(50v job).
We used these because we could change the pre-sets at the field.
We changed the pre-sets on both to 4.1 then charged 2 5s5000's on each to 4.1v.
We let the charge complete it's cycle fully.
We then changed the pre-sets back up to 4.2 and put the packs back on immediately.
Of the 4 packs the lowest 'top up' was 464 and the highest was 489.

This was the best way I could come up with.

Brian

Edit ; I'm confident that the discharge curve ,if plotted (which we did not do), would look almost exactly the same as a 4.2 discharge courve.
ie; The classic steep down then a gentle decline etc.
It would be just the 0.1v lower more or less all the way along time wise.
So power will be down a little all through the flight when compared with a 4.2 charge.

RE: Charge to 4.1v/cell
 

A buddy of mine has a Cell Pro 10X and can't figure out how to set the upper limit. Can someone post the instructions please. Thanks

RE: Charge to 4.1v/cell
 

Download [link=http://revolectrix.com/downloads.htm]Cell Pro Manuals[/link]

RE: Charge to 4.1v/cell
 

Usually my plots of voltage have a drop at first and start to level off for most of the flight, with some dips during high power applications. I was thinking that starting at 4.1 would just get you into the flat of the curve quicker. I could be wrong but I don't think the pack would be a full .1v lower for the whole flight.

RE: Charge to 4.1v/cell
 

Hi Joe,
I was referring to the std,, curve which is achieved is a test situation by applying a fixed continuous load - my bad.
However it will reflect real world work loads.
There is only a drop of 0.45v when you discharge from 4.2 to 3.75.
Now 0.1 seems like a high % of the 0.45.

This does not mean that your point is not valid - just that if one uses 80% or close to it at present the abuse will move from one of 'topping off' to one of over-discharging.

Brian