iMAX B6AC doesn't charge at 5A

Freakazoid

New member
Hey there,

I've got the iMAX B6AC for charging my 4s lipos (and other stuff). For some reason it does only charga at 3.3A maximum, even if I set it to 5A.

Why is this and how can I fix that?

Thanks.
 

RAM

Posted a thousand or more times
Could be part of the automatic programming. I don't think LIPO's stay at constant voltage or current for all phases of charging. Might have something to do with the charge that is left on your battery when you plug it in.
 

rcspaceflight

creator of virtual planes
I have the Accucell 6 charger and when I was charging my 5.0A 3S batteries it didn't go straight up to 5A. I think it stayed at 3something for a while before it worked it's way up to 5A. But I didn't watch it charge so I actually don't know for sure what numbers it was charging at and for how long. But I think what you're experiencing is normal.
 
The issue is the 50W limit on the charger. You need to divide the 50W by the pack voltage to see what the maximum charge rate in amps is going to be. Assuming 16.8V for a fully charged 4S pack, this means that 50W will only allow 50W/16.8V = 2.9A at the end of the charge. Assuming you start the charge at 3.7V/cell, that's 14.8V for the pack, and 50W/14.8V = 3.4A at the start of the charge - almost exactly what you're seeing.

The takeaway is that you're hitting the 50W limit before you hit the 5A limit. Even with a 3S pack you won't get more than about 4.5A of charge rate with a 50W charger. With a 2S pack you would be able to charge at the full 5A.
 

rcspaceflight

creator of virtual planes
The issue is the 50W limit on the charger. You need to divide the 50W by the pack voltage to see what the maximum charge rate in amps is going to be. Assuming 16.8V for a fully charged 4S pack, this means that 50W will only allow 50W/16.8V = 2.9A at the end of the charge. Assuming you start the charge at 3.7V/cell, that's 14.8V for the pack, and 50W/14.8V = 3.4A at the start of the charge - almost exactly what you're seeing.

The takeaway is that you're hitting the 50W limit before you hit the 5A limit. Even with a 3S pack you won't get more than about 4.5A of charge rate with a 50W charger. With a 2S pack you would be able to charge at the full 5A.

Good point. Sounds like I need a better charger. Maybe the OP needs one too.
 

nerdnic

nerdnic.com
Mentor
The issue is the 50W limit on the charger. You need to divide the 50W by the pack voltage to see what the maximum charge rate in amps is going to be. Assuming 16.8V for a fully charged 4S pack, this means that 50W will only allow 50W/16.8V = 2.9A at the end of the charge. Assuming you start the charge at 3.7V/cell, that's 14.8V for the pack, and 50W/14.8V = 3.4A at the start of the charge - almost exactly what you're seeing.

The takeaway is that you're hitting the 50W limit before you hit the 5A limit. Even with a 3S pack you won't get more than about 4.5A of charge rate with a 50W charger. With a 2S pack you would be able to charge at the full 5A.

This is the correct answer and this is why I just got a 400w 20a charger.
 

jetpackninja

More combat please...
Mentor
Good point. Sounds like I need a better charger. Maybe the OP needs one too.
Not necessarily. the 50 watt charger will still charge the battery fully, but most likely not as fast as you would like it to ;)

Thanks Ace for giving the answer that I was not able to find the right words for :)
 
Yeah. 50W doesn't go very far these days as packs are getting bigger. That's why I decided to spend the cash on an FMA PowerLab 6. For the price of 8 iMAX B6 chargers, I get 20 times the power (1000W!!!), plus much greater balancing capabilities. I can charge 4 3S 1800mAH and 2 3S 1300 packs in parallel in about 15 minutes, and the charger isn't even breaking a sweat. And I can control it from my PC and get charge graphs which let me see if any of the cells in my packs are growing funky. I consider it a good investment as I'm not going to grow out of it any time soon.
 

Freakazoid

New member
Thanks for your help guys.

That really bugs me. The charger was pretty expensive and since I'm new to the hobby, I haven't used it that much. I really have to plan going out to fly some time ahead, for charging the lipos.
 

RAM

Posted a thousand or more times
Now we need someone to hack the B6 and add a couple hundred extra watts to it.
 

jetpackninja

More combat please...
Mentor
It's difficult to recommend charging systems to new flyers, especially w/o fully understanding their requirements.
You can get a new flyer into a charger that will probably meet their needs for about 25 bucks.
The typical 50w 4 button multi-chemistry charger is almost always what I recommend.
Part of the problem is not knowing the commitment level for the new flyer.
Your typical 4 button charger may be all some people will ever need and in fact, I did fine with two of these and a couple of parallel boards for a long time
I charge packs for three different flyers, but we all fly 3s.

Now I have a four channel 400w (100w per channel) charger that does everything I need it to do and I can usually charge all of my packs over the course of an evening. If I ever get into bigger packs and highr voltages, I'll probably want something with a 24v input and higher wattage.

Research and education will help you find something that will best meet your needs.
Do your research and charge safely!

This is how I do it:
http://www.flitetest.com/articles/ninja-quick-tip-charging-ninja-style

img-20131016-224441-360.jpg
 

Freakazoid

New member
I think I buy another 50W charger some day, since they can be pretty cheap and I don't need an external power supply. I usually go out flying with 5 4s 3000mAh lipos after work. Thats enough for about one hour of fun, which is enough, since it gets dark after that hour ;). I think it's also best for the health of the lipos, when I charge them at these low rates (in this case a bit above 1C).
 

rcspaceflight

creator of virtual planes
I just ordered an Accucell-8 150W charger. It still runs off of 12Volts. Which is good because I parted out a car that had a new battery in it, so it seemed like the perfect opportunity to switch to solar. I bought a Coleman solar panel for $65 that trickle charges the car battery. I don't fly every day, so I don't need an epic solar panel or anything. So I will soon have 2 chargers that I can use at the same time to charge up my batteries.

On my favorite set up I can get a 2200mah 3S to last for about 15 minutes. It takes about an hour to charge. So I won't have too much dead time using both chargers while flying. Although I kinda want to get another charger or two so I could spend an entire Sunday flying, and yet that seems like too much of a good thing. (Plus I doubt a car battery could keep up with that.)
 

jetpackninja

More combat please...
Mentor
I like the 12v car battery/solar combination.
In the setup pictured above, I very seldom use the power supply anymore.
I bought a big marine deepcycle battery and use it for charging at the field and at home.
I keep a battery tender on it in the garage.
I can basically fly all day at the field with this charger setup.