Using an AstroFlight 109 Lithium Charger - RC Groups
Shop our Airplanes Products Drone Products Sales
Thread Tools
Mar 25, 2004, 08:33 PM
Involuntary Beta Tester

Using an AstroFlight 109 Lithium Charger

After reading about these chargers and using some of my colleagues 109s I decided to pick one up. I already have an Orbit V6 with 6.3 firmware. So what attracted me to the Astroflight 109

Obviously the price is pretty good. $129.

It will charge up to 8 amps. I fly mostly larger electrics so I have several 7.8ah and 8ah Thunderpower 3s4p packs and one 7.8 5s4p pack. Being able to charge to 1C will decrease charge times in the field.

This charger will charge a Lipo pack faster than than the Orbit. I'm not sure about the Schulze chargers. The Orbit takes about 2 1/2 hours to fully charge one of my 3s4p 7.8 or 8 packs to completion just because of the algorithm used. The 109 uses a different algorithum. I was able to fully charge one of my 3s4ps in less than 1 1/2 hours at a recent event on a colleagues 109.

I purchased mine at Esprit Models. I ordered it on Saturday, it was in stock and they shipped it Monday. It arrived today, Thursday via Fed Ex. I've read that normally these chargers come with an Astroflight connector but mine came with a Deans connector soldered on. I don't know if Esprit does that for everyone, a friend bought one a few weeks ago and it came with a Astroflight connector.

I do have some small Lipos, 2 iRate 850s 2s1p packs. All my packs were fully charged so I decided to try the discharge function on one of my iRate 850.

The instrucstion state it will discharge to approxiatemately 3 volts per cell so it should stop at 6 volts.

So I hooked one 850 to the charger and my Radio Shack 25amp power supply and turned the power supply.

Here is the charger after about 40 minutes
Sign up now
to remove ads between posts
Mar 25, 2004, 08:43 PM
Involuntary Beta Tester

Discharge Confusing

As stated before the instructions state 3 volts per cell when discharging.

One of the things I don't like about the Discharge display is that the charger doesn't indicated how many cells it thinks is connected in this mode.

I watched the voltage slowly drop. Just after the photo was taken the voltage started to drop. I watched the voltage reach 6 volts and it kept going down. I watched if for another 10 to 20 seconds and decided to pull the plug as I was concerned it was discharging th cells too much.

Connecting a voltmeter to the battery showed the voltage above 6 volts.

So my question to Astroflight is how does the discharge mode work?

It appears to discharge beyond 3volts per cells.

Does it discharges the cells so that in a resting state they are close to 3 volts per cell?

Since the documentation doesn't state any details other than "approxiatemately 3 volts per cell" I won't feel confident to let the charge automatically stop the discharge mode.
The firmware is 1.4.

Mar 25, 2004, 08:46 PM
Just an average RC'er
Jim McPherson's Avatar
Why would you want to discharge a lipo?

Mar 25, 2004, 08:54 PM
Involuntary Beta Tester
I discharged it so I could recharge it to see how the charging works. I couldn't fly the pack out in my Shockflyer because the weather. Normally I wouldn't do this but the instructions do say that you can discharge your Lipo pack to measure the capacity of your pack.

I have a 7.8 3s4p Thunderpower pack and I was planning discharging to 3 volts/per cell after the next time I fly the pack and then recharge it to measure it's capacity. I've had that pack since last May.

I can use the Orbit to discharge it also by setting it to 9 cells even though the pack is a 3s. It will dischare to 1 volt per cell or 9 volts which is 3 volts per cell.

Last edited by kelvin; Mar 25, 2004 at 09:12 PM.
Mar 25, 2004, 09:07 PM
Involuntary Beta Tester
Now that the pack is discharged I'll charge it up.

With the charger plugged into the power supply, the display indicates waiting for battery.

I made sure the current knob was rotated all the way to the left and then I plugged in the 2s1p 850 and it indicated a 2 cell pack. There are three phases to the charging cycle, C1, C2 and C3. C1 lasts a couple of minutes. I set the current to .8 which is close to 1C for this battery. Then the charger enters phase C2. This is where the voltage ramps up close to 4.2v per cell and the pack is charged 80% to 90%. Then it enter phase 3C. It pulses the current until 4.2 volts per cell and then shuts down.

Here is the pack at phase 3C. It's been on the charge for about an hour.
Mar 25, 2004, 09:09 PM
Involuntary Beta Tester
The charge has completed. 1 hour and 13 minutes. The Orbit would have taken longer. I like this feature.

I plan to use the 109 in the field mostly.

The question is which method of charging is better for the lifespan of the cell? I don't think anyone knows.
Mar 25, 2004, 10:36 PM
Registered User

discharge mode

the discharge mode on the 109 is based
on the ratio of the intial voltage to the
discharge voltage. cut off under load will
vary from about 2.8 volts per cell for small
packs to 3 volts per cell for large packs.
this happens because the cell voltage drops
more under the 1 amp load on small cells.
after the discharge is complete and the load
on the cell is removed voltage will recover
to 3 volts or more.

try it again and you will see.
astro bob
Mar 25, 2004, 11:11 PM
Involuntary Beta Tester
Thanks, I'll try it on my small packs at the Big Spring Indoor event this weekend. I was just concerned that the voltage was dropping too low.

What you have just said would be good to put in future copies of the owners manual.


Apr 08, 2004, 09:13 AM
Crash Master
Gene Bond's Avatar
I am also interested in the differrent charging method used by Astro on this charger. I guess I skipped over all the posts when it was first introduced.

I have 3 different Li chargers currently.

The Orbit, V6.11... It starts with full current, and then tapers current down to maintain correct teminal voltage. It cuts off when current drops below 50ma. You have to be careful with a pack that's 80-90% charged, as it can guess the wrong cell count, or trip off before it can reduce the current enough to cap the voltage. Not sure how the newer firmware acts, but I understand it has changed some.

Hobbico Quick Field Charger Mkll... Not having this as long, I'm unsure exactly what it's doing, but I believe it maintains full charge current, until the voltage reaches the preset level and then cuts off, with no current taper down. This only gives 80-85% charge, which is adequate for a 'Quick Charger' as the name implies. The pack voltage drops after charge termination to about 4.05v/cell.

Scratch-built charger... This uses 2 linear regulators, one as a voltage limiter, and one as a current limiter. It works flawlessly, maintaining the voltage and tapering down the current. There's just no end of charge indication. Sure I could add it, but no big deal.

So, as I understand the Astro 109, it ramps up the current, then maitains the current, then cycles the current to maintain the voltage.

In stage 1, I assume it slowly ramps the current up to the setting, then switches to stage 2.
In stage 2, it maitains the current setting while looking for the target voltage, and then switches to stage 3.
In stage 3, it turns on the set current and cuts back off when it reaches the correct voltage. It waits a second or two, and goes again. When the voltage doesn't relax below the target voltage, it indicates endo of charg.

Does this sound correct?

It's an interesting algorithm, and interesting that it works faster this way. I, too, wonder how or if it affects cell life.

This may be a fun one to play with. Fun, meaning it could also be very dangerous, if you were careless, which I am guilty of on occaision. But, if it does, in fact work faster for the last 15-20% of charge, then it would be well worth the effort to do.

Hmmm... maybe my next scratch project
Apr 08, 2004, 10:34 AM
Registered User

astro firmware

we have invested about 1 man year
in developing our software for lithium
charging. we do not intend to give it away.

instead of speculating on how i works
why not buy on and study it.

Apr 08, 2004, 12:46 PM
Nimble with Gimbals
I usually wait until stage 2 to dial in my amperage as my charger (1.3) will always increase it by varying amounts. Bob has put out a fantastic product and I am most grateful for the time and effort he put into developing this charger.

Bob, Thunder Power specifically recommends that their cells never go under 2.9V per cell even if they rebound. I can forward the e-mail to you if you wish.
Apr 08, 2004, 04:07 PM
Registered User
I have had the 109 for approx 3-4 months with the first firmware version,could anyone tell me what is different in the lastest version and is it worth upgrading[i have had no problems with mine] but am i missing something?

Cheers Graham
Apr 08, 2004, 11:52 PM
Registered User
I just purchased an Astro 109 while waiting for my Orbit Pro to get the correct v6.3 chip to be replaced.

I am very impressed with the speed charging my 3S4P TP pack. I wish that the charger had more power capablility though.

I just bought it new today and it say v1.3? Since I paid full price I don't see pauying for an upgrade already so I'll probably return it and get the latest version.

Overall, GREAT charger. I could buy 2 109s and almost a 112D for the price of my Orbit Pro.

Thanks Bob!

Apr 09, 2004, 12:23 AM
Registered User
Catching up on the list. I noticed you mentioned the Schulze chargers in reference to charging LiPo batteries. According to their web site, they don't have enough memory to upgrade to Lithium charging. I'm patiently waiting for them to decide to increase their memory and upgrade so I can get the firmware for my isl 8-936g. With the trend to LiPo power I feel sure they will want to increase their market share by offering LiPo charging on their marvelous machines. In the meantime I'm using the 109; a fine charger in it's own right.
Apr 09, 2004, 03:13 AM
Registered User
BEC's Avatar

Schulze isl-6 chargers have had llithium charging software available for several months (version 8.xx). Those of you with the flagship isl-8s are still waiting, which has really frustrated one isl-8 owner I know......


The difference between 1.3 and 1.4 in the AF 109, according to the fellow who writes the software, is only something that facilitates factory checkout. To the end user (like you and I) there is no difference. No need to take it back.


The main difference from earlier versions is that the first stage is lengthened from one minute to four (IIRC) and that the cell count calculation can no longer update once the charger enters stage 2.

I'm running 1.0 in one of mine and 1.4 in the other and for the small stuff I'm charging at the moment (no more than 3s) there's not any real difference in how well it works (which is well).

Thread Tools