Question about , lipo's amps, and fast chargeing
 

I know it's safest to charge lipo's at 1c but I hear about (expensive) packs that can be charged at 3,4, and 5c which is really fast. However the packs I can afford (sky lipo, blue lipo, turnigy) make no mention of what the fastest charge they can take is so I'm wondering how you find out if the battery seller doesn't say?

For example, What would happen if I charged my new sky lipo 2200mah 40c 3s packs at 4.4 amps? Would they explode? would they heat up? Would it drastically shorten their usable cycles? Any info on this subject from you guys that know lipos would be great:yipi:

I ask because I just got my new Icharger 306B which can charge at up to 30 amps (more like 20 max with the 600 watt atx power supply I'm using:oops:) and a paraboard to go along with it.

I have 3 blue lipos 5000mah 5s and charge them at 2c rate or 9 amps. Technically they can be charged at 10 amps but I always charge on the conservative side.

From what I know about all the li-po's you mentioned, as long as they are the newer batts, they all can be charged at more than 1c. Some of the older turnigy can only be done at 1c rate. The turnigy's list the charge rate at Hobby king's website. My blue li-po's have the rating right on the batt.

I never charge above 2C, I think the high amp chargers are more about being able to parallel charge multiple packs simultaneously...

Though I do wonder what the criteria is to be able to find the highest "safe" charging rate for a specific lipo. Like what to measure to know when you've found the limit of the packs charge ability. Heat I would assume to be the limiting factor?

I play it safe myself and rarely charge over 5amps regardless what packs I'm charging, I'm reasonably prepared and patient and rarely in a hurry to charge at a higher rate. I have however experimented with a new Sky Lipo hardcase 5000mah 2s 40c, I charged it at 2c/10amps and it was brillant. From LVC to peak took 11minutes and no heat or issues, will I do it again, prob not but least I know I can if needed ?

IMO I beleive the higher charge rates 7-8amps+ is hard on the packs in long term.

Wussies.

You can charge the blue lipos at 5c. Nothing happens with charging at a high rate. I've been charging my 5000mah packs at 30-40A(depending on power supply) ever since I got the Powerlab.
Ebike packs have more then 50 charges at that charge rate for the past month.
The thing is getting more lifecycles out of them and I'm trying that out with 4.1V per cell cutoff and not going below 20% capacity.

One of the biggest issues with charging at a high rate is balancing. If there is enough of an imbalance, the balancer probably won't have a chance to equalize the cells before the charger gets to the CV phase. Of course, this doesn't apply to chargers with internal balancers since they usually see the imbalance and either cut or slow down the charge rate.

from what I've heard fast charges will impact the life cycle of the battery. Fastest I've ever charged any lipo at is about 2C, generally about 1.5C though

Get an FMA and see.

I love my FMA Powerlab 8! :smile: I charge my 5s 4200mah Hyperion at 5c (21.0 amps) all the time now. All of the equipment is cool to the touch. I'm going to keep buying Hyperion Lipos, they are the most solid performing Lipos for the cost (that I've owned).

If it is 1c charge I will charge just below that rating. For A123's I charge at 10-15 amps. For polyquest 5c 4300mah I charge at 10 amps. Like Brian said, the balance will control the charge rate so they don't stay on those high amps for too long. The polyquest have been slightly puffed but that is from in car use, I haven't noticed any adverse affects from charging e.g. no heat or puffing etc...

The FMA can balance and charge at that same high amp rate. Like I said, you have to try the FMA to believe the true high speed charging. The A123's get charged at 20A now. That is limit of those cells.

So does anyone know for sure what a lipo will do if you charge it too fast? Will it just start gassing (getting puffy) or would it start heating up? Or maybe neither and it just shortens the usable life of the battery with no outward signs that it's being stressed?

When I was trying to learn about lipo's I had heard of them exploding during charging but that was from using the wrong charger (nimh) or trying to charge dead or disfunctional cells. I haven't heard of someone deliberately charging more than the C rating.

One or two of my A123 packs were make up's from disfunctional dewalt packs so they have mixed resistance and life cycle (yes, I know, my bad :oops::whip:). Didn't think it would matter that much 'cause of the relatively safe chemistry. There still going strong:yipi:

What I would like to know is how does the FMA keep up the charge rate on unbalanced packs when the balance tap is only good for 2 amps?

FMA does it at 3 amps.

Based on my observations, the resistance of the cells go down when you start to pump amperage into your packs. The higher the CC the lower the resistance.
My Acepow get out of balance below 3.7V per cell. When I have 3% capacity in the 4s pack the cells are out of balance, but during charging the the cells voltages match up again at 3.7V per cell. So in a way it self balance itself out at that point. Now once it goes into CV the amprate drops but then your pack in near full and it's just topping it off.
The top off time is a tad longer with me charging at 4.1V per cell cutoff, which comes out to around 91% capacity.

The one thing I don't like of the FMA setup, is the power cables with the blade fuses. Those little fuses get stupid hot at 40A. I added heatsinks onto them. You don't see that everyday.

:lol: Thats awesome! Can we see a pic?

I'd install a 50A or even 60A fuse then. Fuses are meant to be protection against catastrophic failure and not affect the circuit under normal operation, nor are they meant to run near their fuse value. Upping the value a little won't hurt the protection at all and will not be so hot - that is if the heat is coming from the fuse itself and not the connectors/wiring.

However if the fuses are the ATO/ATC type, 40A is the max size available IIRC and would have to replace it with something a little larger, like a mini-wafer fuse (the larger ones are just too darn big). Or I suppose you could parallel a couple 30A ATC fuses/holders.

Here is a iphone pic

http://i189.photobucket.com/albums/z...8/IMG_0416.jpg



Whenever these fuses go, I'll upgrade them again.

Snellemin... that looks hilariously awesome!

I could make it funnier and heatsink the fuse on both sides.

:party: It just goes to show how powerful the Powerlab 8 is.

Ok I just added a second heatsink. This is maxamps approved.

http://i189.photobucket.com/albums/z...8/DSC04325.jpg

Wrong! Where are the flame stickers? Sheesh! I thought we went over this in detail? You would only need one heatsink if it has a flame sticker since everyone knows they instantly and automatically double, if not triple, the performance.

This is the prototype Brian. The stickers will be wrapped around the heatsink and produce a supercooling effect. Crossdrilling of the plugs and wires are being considered. Crap, I just leaked out the future patent.

I know what happens to all of my packs when charged "too fast". Nothing. :yes:

Maybe add a fan?

:intello::lol:

Why 2 fuses??? It is a circuit and opening one leg negates the need to open the other.
An open circuit is an open circuit...

There's too much power for one fuse to handle. The excess power from one fuse jumps to the other wire automatically. By using two fuses he effectively doubled the burst rating* of the charger.

*Burst rating = (((Fuse 1)(Fuse 2))/(Pi*Cake)^(C^(Flame Sticker)))*0

There is awalys the potential I could plug in the battery in reverse and power on/enable the charger, hence the fuse on the negative wire.

Still wouldn't matter...

It does matter. It doesn't matter at the charger input side. But at the output side it does, as there are relays circuits involved on both the main outputs and balancing output.
One fuse will always blow first, which is better then having to depend on one fuse that can blow at a slower rate.