Help me out please, chargers and charge rates

[Bartman]

Hi folks.
There's a new charger on its way from Hitec, the X4 80, it's a DC only charger with 80 watts max per channel, and it can simultaneously and independently balance charge 4 packs at a time. I'm wondering though, at 80 watts max charge rate per pack, what does that translate to in terms of max charge C ratings for a typical 4S 5000 mah pack?
Maybe I can figure this out a little;
a watt is a volt-amp and we're charging 3.7 volt cells so each cell is getting maybe 4.5 volts to charge it? so 80 watts divided by 4 cells in a pack is 20 watts available per cell. so if each cell has 20 watts available and it's coming in at 4.5 volts, then each cell (C rating) can be charged at about 4.4 amps max?
is that right?
it's amazing what a brain can do after a little caffeine.
bart

 

[kloner]

man, slow..... 5000 mah pack would be at or less than 1c rate

I had a 50 watt single output to start with, had a maximum rate it'd do on 3s around 4.4 amps. If i remember right, the max amps is affected by cell count, not the mah. if i had to guess, with a big enough power supply it'll probably do 4-5 amps on your 4s. I've never been around the multi port chargers like this, did you get a big power supply to support 4x 80? it'd probably need 500 watts at 12v to support full service to all 4 ports. 320 output plus some overhead for the charger

your math is pretty close

 

[robvree]

Hi folks.
There's a new charger on its way from Hitec, the X4 80, it's a DC only charger with 80 watts max per channel, and it can simultaneously and independently balance charge 4 packs at a time. I'm wondering though, at 80 watts max charge rate per pack, what does that translate to in terms of max charge C ratings for a typical 4S 5000 mah pack?
Maybe I can figure this out a little;
a watt is a volt-amp and we're charging 3.7 volt cells so each cell is getting maybe 4.5 volts to charge it? so 80 watts divided by 4 cells in a pack is 20 watts available per cell. so if each cell has 20 watts available and it's coming in at 4.5 volts, then each cell (C rating) can be charged at about 4.4 amps max?
is that right?
it's amazing what a brain can do after a little caffeine.
bart

80 watts is really low for modern 4S batteries. The max amps your charger can hit with your 5000 pack is 5.4 amps per channel (80 watts / 14.8 v). That's only slightly higher than a 1C charge rate. Many modern Lipos can take a 5C charge. Not sure if that charger allows you to combine the power of each channel to charge 1 pack at 340 watts.

For me I have the Hyperion 0720i AC/DC charger. It does 90 watts on AC and 150 watts on DC. With my 2S packs it was great. Now that I have switched all to 4S packs it's killing me. I just ordered the Cellpro Powerlab 8 that has these specs -

612W @ +12VDC input, 1344W @ +26.35VDC.

Using the 12v power supply I currently use I should be able to charge my 5000 mah 4s packs in under 15 minutes at 25 amps (5C).

This is the charger I am referring to - ​

http://www.revolectrix.com/

 

[Bartman]

how many of those packs can it charge at a time?
we've discussed here the benefits of multiple pack charging through the discharge leads but that set-up requires all your packs to be about equally discharged and i can't commit to that. i'm looking for a high output multiple port balance charger. i'll look at the powerlab 8.
thanks,
bart

 

[llbr22]

THey really don't have to be equally discharged as the batteries will equalize themselves (although most will recommend that they are of similar discharge). With a 1000 watt power supply and iCharger 306b I'm parallel charging 6 4s 4000 's in 40 minutes or so. I typically just make sure I've flown them all with similar Fightimes, but it's for sure not exact.

 

[kloner]

i got the 306b, 2 dell 750 watt ps wired in series for 24 volt and it'll blow through 6 6s 5000 mah in nothing flat, have ran it at 30 amps, that's the icharger paralel adapter limit. Next time i need a board, i'll look into that fma one, i like the independant fuses and 40 amp rating

they don't have to be anywhere near exact, it makes all the cells plugged to it the set 4.2 volt and shuts off. I've seen some damaged packs ina mix not come out 4.2, but it's right there. the only thing that has to match is the cell count

 

[kloner]

heres a quick vid of how the boards work

 

[seattle_helo]

Bart, 80 watts per channel is low. I've seen guys with the iCharger doing 30A charge rates and it's pretty impressive. I also know guys with the Powerlab 8 and they love them. Just be sure to get a serious power supply for it. I've got a couple of Bantam BC8 chargers that can do two packs at 200 watts. That's low too- wish they did more. I'm maxed out at a 9A charge rate which fills my 6600 4s packs in about 45 minutes. It's like molasses for these packs that can accept a 10C charge. :nevreness: But I'm old school and I still think that it "helps" the pack to not charge it so hard. :tennis:

 

[Bartman]

thanks for the info....what's the purpose of being hooked up through the discharge leads and the balancing tap?

 

[seattle_helo]

Bart, the packs are being charged via the main leads at 9A. They are also being actively balanced via the taps at 250mA. Those BC8dx chargers have integrated balance boards in them. You can't see the balance adapters in the photo but they have extension cables on them which reach outside the case to the batts.

 

[DucktileMedia]

So, power supply/charger not being a factor, isn't there a limit to how much juice you can inject at a time without harming the cells? I heard that the rule of thumb was max charge at the output of the battery. So if it is 5000mah you charge it at 5 amps max. The I was told even this was harmful to the longevity of the cells. Comments? I know very little about this. I think I will be fine using 2 chargers at once. it takes me over an hour to charge my 5500 3s cells but it is nice knowing I am being good to my batteries.

 

[seattle_helo]

Well, the charge rate is dependent on a few things. The main factor is the chemistry. Not all polymers are the same and it's the higher-end chemistries that can tolerate the increased charging rates. The battery pack must be specifically rated for a charge rate above 1C and that info should be right on the label of the pack. Also it's usually stipulated to use a certain type of charger that can balance and monitor the individual cell voltages with enough discharge power to keep everything balanced and equal at high rates like that. 1C charge rates, like you mention, have been standard since the introduction of LiPo's. It's only been relatively recently that 3C and now 10C+ rates are possible and becoming common. A few friends are using monster 80A, 24V power supplies with serious chargers like that Powerlab 8 and they are charging huge 6S packs in under fifteen minutes. It's all pretty impressive but I still think that a lower charge rate like 2 or 3C will keep packs happier and alive longer. For the guys flying 3D with fish heads I think it's fine for them to push the packs a little with crazy charge rates. But for AC work I think it's better to stay a little more conservative and help ensure reliability and longevity.

 

[robvree]

So, power supply/charger not being a factor, isn't there a limit to how much juice you can inject at a time without harming the cells? I heard that the rule of thumb was max charge at the output of the battery. So if it is 5000mah you charge it at 5 amps max. The I was told even this was harmful to the longevity of the cells. Comments? I know very little about this. I think I will be fine using 2 chargers at once. it takes me over an hour to charge my 5500 3s cells but it is nice knowing I am being good to my batteries.

All the batteries I have claim a max charge rate of 5C or more. The Genesis say 8C, the Quadrocopter say 5C and the Hyperion say 6C but 5C is recommended. Right now my charger is limiting me to less than 2C so I don't have any evidence that these high charge rates are good or bad. I'm sure as hell going to try and get that high to seriously cut down on my charging time. If it makes my packs only last 6 months instead of a year, the time savings makes it totally worth it to me.