Amp/Volt Settings for (2) PL8s w/ 1 Power Supply

[GRR45]

I just picked up 2 PL8s and a Meanwell power supply which delivers ~2000W @ 80A continuous and 24V. I plan to power the chargers with a Ryobi inverter generator capable of 1800 W continuous/ 2200W surge.
I’d like parallel charge on both PL8s simultaneously and am looking for recommendations regarding the max current and voltage settings I should set for each chargers and was considering the following:
1) get close to “maxing out one PL8” with limits of 54A @24V (1300W), and set the 2nd PL8 to 15A @24V (350W), which puts total power draw at a bit over 1650W, or
2)Set each PL8 limits at 32A @24V, which puts max power draw at around 1550 W
Do these settings look reasonable, or would there be a better way to do the setup? I understand that these figures don’t account for all inefficiences with the chargers/power supplies, but hope they are in the ballpark considering that I don’t typically charge over 2C and use primarily 3S 2200 mah, 6s 3000 mah, and 6s 5000 mah packs.
I know the chargers can be connected in expansion mode, but have a large mix of different batteries and would rather not to use the Auto 1, 2, or 3C presets on both chargers, as some of my older packs aren’t ever charged over 1C. Generating fuel tables for the various brands and ages of the packs also seems less than ideal for this situation, and the instructions suggest that expansion mode can be inefficient and slower if the fuel tables aren’t accurate- I’d rather keep things simple and input the charge current manually as required.
Thanks in advance for any advice or suggestions, and sorry for the lengthy post.

[nightflyr]

I also run dual PL8 chargers, but I also run 4 server supplies wired for 24V @ 97A.
To keep things simple I set both at the same limits.

[Gregor99]

Here's a couple data points for you.

• Charging 6s packs at the full 40 amps only requires about 45 amps from the supply.
• In expansion mode there isn't load sharing data. With regard to balancing load, you aren't losing anything by not running in expansion mode. But its a very cool feature and I recommend you explore later.
• Typical end to end efficiency (charger+power supply) is 75%. That means with your supply and generator, you'll be about to hit about 60 to 65 amps of combined output (charging 6s packs.

I would set the input current limit to 47 amps. That way you will always be able to fully max out one of the chargers on 6s. At high charge currents the CC stage ends rather quickly. As soon as thes the CV stage starts, the charge current will star to drop rapidly. Since you are staggering your charge cycles, you can start the second charge at full tilt as soon as the first charger drops down to 35 amps.

Be sure to do some testing of this setup. You may find the generator does not quite deliver the rated specs. Or you need to beef up your extension cord. Normally a Kill-A-Watt is useful for telling how much you are pulling from the generator. But at 220 watts, you will be well over its 15 amp rating.

[GRR45]

Thanks for the information and quick response. please bear with me, as I am a noob to parallel charging s well as the pl8s. By this:

Originally Posted by Gregor99

[*]In expansion mode there isn't load sharing data.

Do you mean that the pl8s do not automatically adjust the current and voltage to each charger to prevent overload when two units are powered by a single supply in expansion mode (the units assume that there are two identical power sources to support charging)?

Sent from my SGH-T989 using Tapatalk 2

[Gregor99]

Originally Posted by GRR45

Thanks for the information and quick response. please bear with me, as I am a noob to parallel charging s well as the pl8s. By this:

Do you mean that the pl8s do not automatically adjust the current and voltage to each charger to prevent overload when two units are powered by a single supply in expansion mode (the units assume that there are two identical power sources to support charging)?

No problem, happy to help. You are correct. When two Powerlabs are connected in expansion mode, both chargers still have individual current limitations and honor their own setting without sharing load info. In fact this is the way I power my two Powerlabs. Two separate supplies, one for each charger. Its not required, it just worked out that way.

I occasionally run both chargers from a single supply. In those times, I just manually ensure the total current from both chargers does not exceed the supplies' rating. I will either charge at a reduced rate, or stagger the high power charges as I described above.

[GRR45]

Many thanks for the information, and i will try my best not to post too many more questions. Too bad the wizards at revolectrix haven't come up with firmware which automatically "ramps up" the power supplied to a second charger as the power demand is reduced to the first unit to always utilize 100% of the power available. Seems like it would be a nice feature.
Out of curiosity, did you calculate the 47 A max rating for the 6s packs by just assuming a 15% loss in efficiency? Finally, how did you calculate that the threshold for starting the second charger should be when the current to the first unit drops to approx. 35A? I am only asking because I'd like to set up a spreadsheet to determine charge rates and current thresholds for starting the second charger using different packs and scenarios. Once again, thanks, for all your help.

[Gregor99]

The observed current draw for a 6s pack at 40 amps starts 44 amps and peaks at just under 46 amps at the end. This isn't calculated, its measured. The result is just over 90% efficiency. The FMA online calculators use a worst case of 85% efficiency. But I've never seen my Powerlab do worse than 90%.

When the second charger starts up the pack voltage will be lower so current draw from the supply will be roughly 44 amps. The supply is rated at 80, so 80 minus 44 is 36. Round it down to 35 so the total current will be 79 amps from the supply.

[Diviner]

I have that Ryobi gen with an iCharger 4010duo (basically the same setup as yours). The max you will get out of the gen/charger is 42amp at 25v (21amps x2). That gen max is 12.5amps @ 120v (1500w) before the overload kicks in. If it is hot outside, the max drops to 10amps (1200w) from the gen to the charger.

Like most 2000w chargers (15a @120v=1800 watt rating), the actual capacity is around 12.5a (1300w-1550w).

The honda is rated 1600 or 13.3 amps so this isn't a ryobi thing.

So, you have about twice the capacity in your setup as the genny can handle.

But with your setup, you can still charge about 4 700 sets (2x5000) an hour, and can do unlimited flying (7 flights and hour) on a 600.

Also, I have noted almost 0 loss in efficiency from the power supplies (dells) and very little drop from the charger. I expected more of a drop but was pleasantly surprised.

[GRR45]

I had no idea the generator capacities were that overrated and assumed the full 1800w would be available to work with. I'll assume I have 1500w available from the generator and will lower my charger settings if that results in overload. Thanks for the info guys.

Sent from my SGH-T989 using Tapatalk 2

[Diviner]

Knowing what I now know, I wouldn't of upgraded from my hyperion super duo (500w/500w) since it was cable of 20a per side, and I am only getting 21 per side out of the iCharger at the field. Tons of unused capacity. But it hasn't impeded the number of flights an hour that I fly.

The only reason to buy a 1000w+ field setup (like both of us have) is if you have a 3000w genny.

[Gregor99]

I'm using a Honda EU2000 which does operate fine at it its rated spec. Though I cannot max out both chargers, its more charger than I need.


Based on 75% end to end efficiency (power supply+charger)
Continuous - 1600 watts AC - 1200 to packs - 47.6 amps for 6s - 23.8 amps per charger
Peak - 2000 watts AC - 1500 to packs - 59.5 amps for 6s - 29.75 amps per charger

Plus its nice to be able to pump 40 amps into 6s packs on one charger then use the second charger for 3s packs, 2s or 1s packs at the same time.

[GRR45]

I was going to buy the 1600W Honda and bought the Ryobi instead due to the 1800W rating. I haven't tried charging with it yet and hope that it isn't as over-rated/underperforming as indicated above..

[Diviner]

The real life ratings of Honda, Yamaha, Ryobi, and all the others (champion, etc) are probably all within 10%. They are designed around a 15a circuit.

I bought the Ryobi, in part just like you did, based on the 1800 ratings. However, I knew not to expect more than a Honda (1600). Mine is coming in at 1550. And drops as a function of heat.

The biggest reason I ditched my deep cells was that there are now 2000 watt generators that were half the price of Honda and Yamaha (Ryobis can be found on ebay for $500 shipped back in April, I paid $550 shipped).

I like Ryobi; they have affordable products. I also liked the wheels that come standard on a Ryobi; a feature that is $100 more on a Honda. It also has the telescoping handle, something that Honda doesn't have. So in pure features, Ryobi blows Honda out. In performance, they tie. The test will be service and longevity. In terms of value (quality / price), Ryobi wins by a factor of 2. I could have 2 Ryobis for the price of 1 Honda and tie them together to get a true 3000w, thus maxing out my field setup.

The Ryobi has been out for a few years now, so it does have a track record.

I don't subscribe to the notion of "you get what you pay for". I do however believe in "sometimes you get more than what you pay for". I currently believe the Ryobi to be the latter, Honda the former.

Personally, I think the days of spending $900 on a gen are over. Much like spending $400 on a FBL. People will think they are getting a better unit because they paid double. Maybe they are right. But maybe they are wrong.

But again, time will tell.

[GRR45]

Glad to hear you are happy with the ryobi and hope I feel the same way after I develop a comfort level with parallel charging and the pl8s.
That said, if the max. output is really about 1550w, Ryobi should be up front about it. I do agree it does have some nice features lacking in the other units
One other question, do you typically charge single lipos at high rates or parallel charge multiple packs? Thanks.

[Diviner]

I always parallel charge, but only 2 batteries. Sometimes 1 if a single cell gets out of whack. Once you start parallel charging, you never go back to single charging. With multiple chargers, you are always staggering 2 sets of batteries at a time. That means every 10 minutes you have 2 batteries coming off a charge on one charger or the other.

It becomes an assembly line. Fly 2 flights, pull 2 off the charger on the left side, throw two on. Fly 2 more flights, pull 2 more off the right side and put 2 back on. You always have 4 charging and 2 are always coming off every 10 minutes or so. Any extra time just gives the charger more time for cell balancing. Its like clockwork.

Everything goes home with a storage charge. Usually I leave 2 packs fully charged if I am flying within a couple of days. That way I have zero down time when I start the next flying session. It's a thing a beauty when it all comes together.

My setup. The deep cells are gone and the genny is just behind the fence. 30 feet of a retractable extension cord that I have mounted permanently to the geny is just enough so the sound is reasonable when it is maxed out (which is all the time).

[GRR45]

So with your setup you only need six or 8 packs of each size for nearly continuous flight? What is the highest C value you charge at, and do you buy thunder powers or other high $ lipos? Also, do you simply split the power equally between the chargers or do you stagger the charging as the current demand drops as Gregor posted above?

[Gregor99]

For my 600 and 7000 I only have two flight packs per model (two 6s packs). Most decent packs can be charged at 3c to 5c without an issue.

[Diviner]

Originally Posted by GRR45

So with your setup you only need six or 8 packs of each size for nearly continuous flight? What is the highest C value you charge at, and do you buy thunder powers or other high $ lipos?

For continuous 6s flyers 450, 500 X5: 6 packs each.
For alternating 12s flyers 600 & 700 : 2 sets (4 packs total) each.

Mostly Ace Pow (gens ace, glacier, pulse ultra). A few nanos on the smaller models.

C charge rates: All at 21a into 2 packs, so 4c for the smaller ones up to 2c for the biggest ones.

In fact I just sold over 20 batteries I no longer needed since moving to a genny.

Also, do you simply split the power equally between the chargers or do you stagger the charging as the current demand drops as Gregor posted above?

I thought of that, but for simplification and the fact that the charger is not the bottleneck, it is just 21a into both sides all the time.

With the iCharger ( and I believe the pl8) the balance phase of the charge is very short, so when the power drops it isn't very long.

My old charger ,the hyperion, the balance cycle was 1/3 of the total charge. In that case I would consider 30a & 21a settings for each pack type.

[GRR45]

Thanks for the info, I'm going to set mine up the same way to keep things simple and will get some better quality packs to reduce the risk of charging at higher rates.

[Diviner]

One more tidbit.

If you are buying good packs and doing field charging, try setting the ending voltage from 4.2 to 4.24. Lipos can go up to 4.28 safely, but to keep well within the limits, 4.20 is recommended. Pros do this all the time in order to get 4min of hard flying.

I have accidentally went to 4.5v without incident on a charger screw up on my hyperion.

In the highly unlikely event of a charger fire, you are outside so there is minimal damage.

Good luck!