Charging at Home & Charging at Events

Power System
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I recently took my ePPG to its first 3-day fly-in. I wanted to see how quick and easy it was to charge the batteries on a portable generator and maximize my flight time. Here’s some observations:

My setup:
8 Bonka 22Ah batteries
3 Dual-Channel Battery Chargers
-2 Polaron EX (400 Watt per Channel)
-1 HT700 Duo (350 Watt per Channel)
1 1500 watt Power Supply (for the Polaron’s)

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If you could charge a LiPo at 1C from 0% to 100% it would only take 1 hour. In practice, topping off the battery (the last 20% or so) uses significantly less amperage to prevent taking the cells over 4.2V. I believe the average LiPo takes 1.5 hours to charge from 0% to 100% at 1C.

In my case, 400 Watts gives me about 22 Amps (1C) for just a few minutes, but as the voltage climbs, my Amperage drops. Plus I always do a balance charge, which adds time as well. I average 2 hours for a complete charge, (and I typically see the Bonka batteries give a full 22Ah).

I also have two other limiting factors, my power supply is only 1500 Watts, so charging 4 batteries off of the one power supply gives me about 350 watts per channel (with overhead wattage for the actual chargers). With all three chargers running, I am pulling more than a standard 20 amp AC circuit can deliver, and it pops the breaker (in theory I should be under the 2400 Watts for the circuit- but I’ve tested on several circuits at my house and at another house, and they always pop).

Knowing all these factors, I tried a Honda 2200 generator, but it couldn’t handle the load, so I ended up using an older Champion 5000 Watt generator with 2 20amp outlets and it worked great!

Best case scenario would be to start each morning with fully charged batteries, do one flight then start charging the first 4 batteries, and then do a second flight (on the other 4). After the second flight start charging 2 more batteries. An hour and a half later the first 4 would be done then add the last 2 batteries. Then another flight and 2 more batteries on the charger. Before mid-day a last flight with 6 batteries, then charge everything back up and repeated the process in the evening.

So 8 flights in a day is best case, which sounds like a good day, but it would really only be a little over 2 hours total time in the air. During the test, I spent a significant amount of time swapping batteries back and forth, and of course, waiting…

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Sounds you had a lot of fun and flight-time!

Over a year ago I was posting about charging here…

To have an idea as to how powerful your charger has to be…

Wattage is calculated by measuring the voltage and amperage of a circuit and then multiplying them together:

Watts = Volts * Amps

If you want to charge a 22000mAh 6s pack at 1C. How many watts does that require? We know the voltage of the battery and the 1C charge rate is 22A.

Watts = 6s * 1C = (25.2V) * (22A) = 544.4W

So the charger will be outputting at most 544.4W. I say most because the voltage of the battery is changing the whole charge cycle. It will likely start in the mid 22V range and will finish at 25.2V. So in order to calculate the max wattage needed, I use the max voltage involved.

My 24 Volt 1500 Watt power supply and my two chargers are 1000 Watt 30A per charger -
Even if I put them on 2 C charging they can just charge with 1.35 C (29.8A)…

In conclusion the wattage plays a crucial role in charging. Don’t forget to take it into account as you choose your charger and power supply.

You can also charge your lipo pack with 0.5C or 0.2C in this case you just have a less powerful charger!
It just needs more time…

Don’t forget “NEVER USE THE CHARGER UNSUPERVISED”

In your case why you need more time to charge the batteries:

Charging 4 x 22000 mAh with 4 x 350 watts = you are charging with ca. 0.63 C (13.9A) and not 1 C!

Hope this explained it…

1 Like
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Thanks! So for a dual-channel charger I’d need at least 1100 watts. I’ve looked for chargers that high, but haven’t found anything reasonably priced. @tarifachris what charger are you using at 1000 watts? Is it dual-channel? Anyone else found a charger that can perhaps do up to 2C on these bonka batteries?

4

Interesting!
If your doing 4 battery flight I think 12 bats is optimum - go for flight - you have 2 packs waiting - start charging 1st pack and 3rd still waiting to fly with 2nd pack charging…

This is what I was thinking of doing - was getting ready to order another 4 bats(have 8 now) but then I just purchased a Chevy Bolt so no more bats for me because I just purchased that 60KW one with the Bolt ***** if only I could run my small charger off that *****

5

I use that one to load this battery:

I use that combination with this 3500 watt inverter and 12 volt batteriebank parallel 8x agm varta marine 2000 ah

6 solarcells 2100 watt peak and 3 mpp loader are loading the batterybank

All installed in a boat - works perfect - for fieldloading you could put the batterybank on a trailer and load it at home via solarcells and use it as a powerbank also for your house.
Or as overkillsolution : https://www.mobismart.ca/

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I agree, and it’s the configuration I’m working towards.

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Thanks for the info, but I was hoping for under $300.

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My new HT700 charger does not seem as accurate as my other two chargers. Anyone else experience this?

My Polaron chargers will put 22Ah into the batteries after I’ve used them until they are almost completely discharged, whereas the HT700 says it charged them up 24.5Ah. Since all 6 batteries were connected together during the flight, and they are only a 22Ah battery, I’m more inclined to believe the two Polaron chargers instead of the HT700.

1 Like