Lithium or Not ?

Thu Sep 4 12:15:50 AKDT 2003

I would add that we get focussed on the battery and not the charger. All batteries will do something nasty if seriously overcharged.

I pay a lot of attention to what Jim O. tells me. If the charger will not prevent an overcharge then you have high risk situation. Jim has written about this before.

Regards,

Eric.

-----Original Message-----
From: discussion-request at nsrca.org [mailto:discussion-request at nsrca.org]On Behalf Of Troy Newman
Sent: Sunday, August 31, 2003 6:49 PM
To: discussion at nsrca.org
Subject: Re: Lithium or Not ?

Li-ion packs.

Bob, and Lance.....
I have been running these 2000mah packs since February. They are a 2 cell pack. Central sells them for $35 a pack and they have a $50 charger....Here is the kicker. The charger is plug in and forget. It can't harm the batteries even if left on charge for 3 months. Its basically a voltage regulator setup where it puts out 8.4V and when the pack reaches 8.4V its done....The nice thing is the charger has a Amp meter on it so when the battery is empty it might take 1-1.3amps but as it charges the current flow goes to zero. Once the pack is charged up the current flow is zero and no juice is going to the battery. You're not waiting for a light to turn color or go out...You can see what is actually going into the battery.

Lance the pictures of the plane that burned up were a guy using Lithium Metal cells. These were the first Duralite batteries....The industry folks got away from Li-Metal as it was highly highly dangerous when the electrolyte came in contact with the air....and would burn....

Let me repeat the Lithium-ion packs are not the same packs as caused that guys fire.

OK

Here is the scoop on what I use. 1 battery pack 2 cells its rated at 2000mah....I can pull about 2200 out of it before it reaches the magic stop voltage. The pack has a great discharge curve it is almost linear until the pack is near dead. So every flight might use say 0.15V per flight....It starts at 8.4V and I stop flying at 7.2V on my Volt meter with a 500mah load. They say you should use a 1amp load to test the voltage. What I did was plot a curve of the discharge. I stuck the battery on a cycler for 15min "flights" pulling the exact same mah out of the pack each "flight" I then plotted it on a graph vs. time. This gave a sharp knee when the pack is almost of out power.....What happens is as the packs fall below 7V there is not much left in them...Even though the cutoff is officially like 6V or 5.5V depending on the company selling you the battery...By the way many of them are the same cells. And I have driven the pack down to around 5V and they are still fine. I tested the batts about 4-5 times and got the exact same response everytime...So I flew them and got the exact same response as if I was having the pack sit on the cycler....I use about 180-200ma per flight

Setup...1 pack 2000mah, 1 Oddino regulator 5.3V...and go...... the setup weights about 3.8-4oz total. I can fly around 8-10 flights in a day and still have enough for more flights but its getting close to time charge. Charge up is about 2-3hrs on a  dead battery pack. The charger runs on a 12V source so you can "field" charge it just doesn't charge any faster than the 2-3hrs on a dead pack...However...With the AMP meter on the charger you can get an idea of the charge level left in the pack. Plug it in and it draws 300ma...then you still about 3/4 of the battery remaining....if it draws around 1amp its almost dead...and needs some time on the charger...If for example its drawing 1amp and 1 hr later its down to about a 200mah draw on the charger...pull it off and fly it some more....it will jump into the curve like it already had 2-3 flights on it....and act the same as it did on flights 4-5-6 from a full charge....There is no memory, no need to drain the pack before charging....you can charge after one flight or after 10 flights.....

Also if you charge and don't fly for like a month...the battery is still sitting at about 98% full charge....I have a pack I charged before the Team Trials....just measured it and full its 8.4V and it reads today 8.31V...It was charged last in Mid JUNE! Like the 10th of June...and its still got 8-9 flights in it....

These packs are awesome. They are dummy proof and allow me to fly all day long...now your mileage may vary depending on your battery drain....But I'm running a YS DZ on a Hyde Mount with 5 digitals even a little 3421 on the throttle.....9411SA's on the Ailerons and 8411SA's on rudder and Elevator...So I'm working the packs pretty hard...

Just ask ole' man Whitachre...Bob would come out this spring and what me fly all day on two models...I would drain 2 gallons of fuel just flying back to back to back...about 16-18 flights in a day....and never charge...just fuel, test, and fly.

Since being in GA I have been out much less than before the NATS and I have gone flying 2-3 days on the same charge. Maybe 3-4 flights per day.

I love the way they work.....Can't speak for the Duralite, Powerflite, and others...but the Central Hobby packs are great....I gave all my Nicd packs away to guys that will use them. I don know the Powerflite and the NMP (centrals) are the same cells. As are the Superbatterypacks.com, and some of the other suppliers...Now Duralite and Powerflite have special chargers that are expensive but they can charge 2-3-4-5 packs at a time....this charger only does one pack at a time....buts a dummy proof charger...reverse polarity it doesn't do anything...lites a red LED to tell its backwards....Green LED says Polarity is good and plu it in....If the amp meter says zero its charged....If it reads 1.3amps the pack was dead....pretty simple...and you can use the charger like a fuel meter....the closer the meter is to zero the more charge is inside the battery pack....

As for the age issue. My packs are pretty new...but I know people that have packs going on 2 years old now. The age failure seems to be a slow loss in capacity...as the pack gets old...they simply don't reach 8.4V any longer...Instead they it 8.2 then 7.9V and then slowly creep down to 7.5V....At this time is when you know to get a new one. 

I have 2 packs I have flown since Feb....that's going on 28 cases yes cases of fuel this year.....I'm approaching 1000 flights just this year flying two different models...I think the technology is pretty sound and works well. I was leery before as I had some bad luck with the old style li-METAL packs Duralite originally sold....These packs are much more forgiving and easier to manage.

I would recommend them over ni-cds or Nimh....weight is not so much the issue its the consistent discharge curve....they are AWESOME.....
And not priced too much out of range.....$35 a pack....this is slightly higher than a 2000mah Nicd pack...

Troy
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