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e-Electric Batteries & Chargers > Li-po charge rate, 2C, 3C, 4C!

Richardmid1
Veteran
Location: Leeds, England

Whats the fastest anyone has ever charged a Li-po without damage?

Eat, sleep, 3D, crash, repair, repeat...

07-12-2008 07:49 AM

"Cam"
Veteran
Location: Asia

Well, since doing this will void your warranties and probably cause a fire. Please have a bucket of sand, a Co2 extinguisher, a shovel and a camcorder at the ready so you can post it on you tube for us all to laugh at you.

Really, no one wants to do this because their LiPos are too costly to dick with.

It takes time and a few brave and/or wealthy or Darwin nominees to confirm you can keep doing this without a problem. Most people will crash their packs long before they are near the end of their cycle lives so they never know.

For now, please stick to charging Lithium Polymer packs at 1C, unless you have a really smart charger like an 0610i or 0606i DUO – then you can charge at 2C.

A123 (LiFeP04) can be charged at 4.3C – this is 10 Amps for a 2300 pack.

Most chargers will not let you charge at more than 1C. The top end ones – the last two I stated will but you have to change the amps from the default setting. AND these chargers are very smart and really will not let you make a mistake compared to cheaper ones that will cost you the battery.

07-12-2008 02:42 PM

helicraze
Key Veteran
Location: Victoria - Australia

Charging anything above 2-3C gives really no reduction in charge time, its very little difference and won't outweigh the damage.

Charging at 2-3C will give you reduced cycle life, but is safe to do with a good charger and balancer and lipo

07-13-2008 05:39 AM

Richardmid1
Veteran
Location: Leeds, England

I doubt a li-po would catch fire from fast charging, unless you weren't using a balancer and the pack was seriously out of balance.

Eat, sleep, 3D, crash, repair, repeat...

07-13-2008 10:02 AM

Raydee
Veteran
Location: Western New York

My Lipo's cost me so much that I have never charged above 1c yet. I guess I am just a chicken

The Future of Nitro is ELECTRIC

07-13-2008 01:05 PM

helicraze
Key Veteran
Location: Victoria - Australia

I charge my $460au 10S pack at 2C sometimes

07-13-2008 01:48 PM

Magic Hook
Senior Heliman
Location: Naples, Florida USA

What? Consider buying more battery's!

07-13-2008 06:36 PM

Richardmid1
Veteran
Location: Leeds, England

Its cheaper to buy a good charger than a bunch of batteries.

Eat, sleep, 3D, crash, repair, repeat...

07-13-2008 09:15 PM

"Cam"
Veteran
Location: Asia

I am going to start charging LiPo’s at higher rates but I will also be using PC Logging software so I can compare the charges over time. The software “LogView” by “Dominik” on EZone also shows the individual cell voltages (from the NET and DUO) and I need to double check but I am sure it has a compare function for saved charts.

On LogView you can see when the charger pauses to perform an accurate balance check. There’s about ten values you can plot including the individual cell voltages so you can see how everything is varying.

One problem at the moment with charging at 3C or 4C is the balancers work by discharging and they can only do upto 300mA per cell. So packs may get out of balance quicker then the balancers can compensate, this could cause a fire.

07-14-2008 01:00 PM

beeflyer2
Key Veteran
Location: Woodstock, GA

Cellpro 10S, 2C/3C charging no problem. I keep it at 2C though.

07-14-2008 03:58 PM

fenderstrat
Elite Veteran
Location: Aston,Pa

been charging at 2 and 3C for a year,if you look on the main forum you will see a thread I just did.One of my batteries just hit the 500 cycle mark(sport flying) and has been charged at 2C since day 1.With the proper set up 2-3C charging is safe and will not cause short cycle life.those of you who seem to love that 1 hour charge time,enjoy your 1c charging

Quote
One problem at the moment with charging at 3C or 4C is the balancers work by discharging and they can only do upto 300mA per cell

if you have an "active balancing" charger this is not a problem,as the charge rate is monitored and the cells are balanced AS they are charging

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07-15-2008 04:22 AM

Richardmid1
Veteran
Location: Leeds, England

I use the FlightPower V-Balancer which is a high rate balancer and can handle upto 10amps. I charge my 6s 2600mah packs at 4.2amps which is the most my charger will put out for 6s and they always balance out with the V-Balancer.

Eat, sleep, 3D, crash, repair, repeat...

07-15-2008 10:14 AM

"Cam"
Veteran
Location: Asia

4.2 Amps. The NET & DUO will do 10. – That’s a 5 cell A123 charging at 10 Amps, on each port!

‘Active balance charger’

“if you have an "active balancing" charger this is not a problem,as the charge rate is monitored and the cells are balanced AS they are charging”

AND how is that done? BY discharging the high cells. BUT if you do it too quickly you are generating a situation where some cells are loaded more than others so it is impossible to directly compare voltages and balance the cells.

That is why there is a sensible limit on the discharger.
That is why the charger even stops at regular intervals – to accurately measure cell voltages- because it cannot be done while charging.

There’s another problem – heat. When resistors heat up (generally what ‘the cells’ (I’ll explain the “” another day) are discharged across, the resistors resistance value changes. This is why balance circuits are delicate things.

The harder you push it the more un-accurate everything gets.

07-15-2008 03:56 PM

fenderstrat
Elite Veteran
Location: Aston,Pa

Quote
AND how is that done? BY discharging the high cells

no, not at all, the input charge of all the cells is monitored and the charge rate of each cell is adjusted so that they are charging at exactly the same rate(cell voltage is checked at 1 min intervals and adjusted constantly throughout the charge cycle).if one cell charges faster the charge rate of that cell is reduced while increasing the other cells,so all cells charge at the same rate.After almost 1500 charges on a CELLPRO4S I have yet to see the cells more than .01V different from each other, ever, during the entire charge cycle

there is a big difference between charging the battery and then balancing and balancing each cell WHILE charging

the FMA chargers do not charge cells and then bleed of current as with most "passive"balancers.that is why 2 and 3C charging is safe with this method, individual cells are monitored the entire time.If the charger senses an imbalance that it cannot correct,it goes into safety mode

http://www.fmadirect.com/

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07-15-2008 06:02 PM

"Cam"
Veteran
Location: Asia

Fenderstrat

You are talking about a parallel charger. These are difficult to calibrate in manufacturing and when they go wrong they really go wrong.

The EOS NET and DUO do constantly monitor and correct cell voltages while charging - and as I tried to explain in my last post doing this while charging has the cells under load, that is why the EOS chargers also stop every minute to do a precision check while the cells are at rest.

A ‘bleed’ balance charger does not really take any current or capacity out of the cells, it is actually reducing the charge rate, allowing the other cells to catch up. Over all it gives the exact same end result only is simpler and more reliable.

07-16-2008 04:19 AM

fenderstrat
Elite Veteran
Location: Aston,Pa

Quote
You are talking about a parallel charger. These are difficult to calibrate in manufacturing and when they go wrong they really go wrong.

the FMA chargers have been out a long time and I have seen very few posts about any serious problems(actually none).Almost all the posts I have seen,the owners give the chargers high marks as far as performance.Most swear by them

Quote
A ‘bleed’ balance charger does not really take any current or capacity out of the cells, it is actually reducing the charge rate, allowing the other cells to catch up. Over all it gives the exact same end result only is simpler and more reliable.

when a "bleed" balancer is used after charging as many people use them,they do "bleed" voltage from the high cells to the low cells,thats exactly what they do.its also why a "bleed" balancer will almost never give you a true full charge,the only way to get a true full charge from this type of balancer is if all cells hit full charge at the same time......for example in a 3 cell pack if one cell hits 4.2V while the other 2 are at 4.18V the charger will stop charging,the balancer will then lower the highest cells to match the lowest bringing the individual cell voltage to 4.18-4.19 V per cell

when an active balance charger is done all 3 cells are at 4.2 because for the last 10% of the charge all 3 cells are charged at exactly the same rate,very slowly and very precisely so they reach full charge at just about the same time

this is why Thunder Power only recommends 2C charging if you are using their charger and balancer WITH the data cable(active balance charging),so the charger/balancer communicate DURING the charge.....if you use the EXACT same set up WITHOUT the data cable(i.e passive balancing)they only recommend 1C charging

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HBK2
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07-16-2008 04:42 AM

"Cam"
Veteran
Location: Asia

Quote
when a "bleed" balancer is used after charging

After charging? I was talking about DURING charging.

Quote
for example in a 3 cell pack if one cell hits 4.2V while the other 2 are at 4.18V the charger will stop charging

This is NOT the case with Hyperion

Quote
when an active balance charger is done all 3 cells are at 4.2 because for the last 10% of the charge all 3 cells are charged at exactly the same rate, very slowly and very precisely so they reach full charge at just about the same time

That is maybe how parallel balancers work. It does not matter if all the cells reach full charge at the same time. The only thing that matters is that they are all the same voltage.

And by the way, you can save a huge amount of charge time by setting the TCS to 90% on Hyperion chargers - basically stopping the charge at the end of CC, and omitting the slow CV part at the end. This can save 20 minutes of charging with large packs for only a cost of 30 seconds flying.

Hyperion chargers balance all the time while charging and the charge ends when all cells reach the TCS specified.

07-16-2008 08:36 AM

fenderstrat
Elite Veteran
Location: Aston,Pa

I still am not sure you are understanding ....if the charger charges through the main leads and balances through the balance tabs at the same time(balance charging) it is a different process than charging THROUGH the balance tabs(FMA)......if the charger is charging through the main leads how can individual cell charge rates be controled going INTO the battery?they cant, they can only be bled off AFTER the cells have been charged,

Quote
After charging? I was talking about DURING charging.

the type of charging I am refering to charges THROUGH the balance leads(main leads are NEVER used while charging with an cellpro 4S charger) so voltage is adjusted BEFORE it gets to the battery...this is just going round and round so this will be my last post on this subject,no hard feelings or anything like that,you just have your view and I have mine

HAPPY FLYING AND CHARGING....FENDER

oh and as far as active balance chargers being expensive and tricky to calibrate a cellpro 4S is 75 bucks and the 10s which will do up to 2 5s(or 1 6-10s) batts at the same time is 189 dollars.when set to auto mode you plug the battery in and go,thats it

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COMPASS helis field rep
Mini Titan/SE
HBK2
Futaba FASST

07-16-2008 02:36 PM

"Cam"
Veteran
Location: Asia

Not going in circles mate, blocks, block-diagrams.

Yes I understand.

The EOS chargers charge through the main power leads and balance the cells through the balance harness **At the same time**

Quote
how can individual cell charge rates be controled going INTO the battery?they cant, they can only be bled off AFTER the cells have been charged

YES THEY CAN

Components in Parallel all get the an equal share of the Supply Voltage

Components in Series all conduct the same current because their individual resistances all effect what share of the voltage is across them.

You can see the balancers are all in parallel with each of their cells. And all the cells and balancers are all in series with the Supply Voltage.

Think of a single cell balancer as a resistor. If it’s resistance changes both the balancer and it’s cell get a different voltage, so the current they draw also changes.

The EOS processor then changes the supply voltage so the other cells stay the same. In reality, all can be changed as they need to.

Now, the EOS internal balancers can discharge at 300mAh per cell. We say that, because it’s a lot easier than explaining that the balancer is really just altering the voltage and charge rate of a any single cell.

No discharging happens while an EOS is balance charging. The high cells simply get charged at a slower rate.

That is why charging above 2C is still a problem – people want small cheap chargers, not ones with massive heat sinks and fans to dissipate all the heat from the cells with higher voltages. (The DUO has two fans and a heafty heatsink across all the FETs inside)

A charger that can balance at the same time, and a charger that charges through the balance harness may be electronically different, but the end result is the same.
In fact you may notice the top positive balance wire and the bottom negative balance wires are directly connected to the Supply Voltage.

There’s a reason Hyperion do not charge though tiny, high resistance wires.

- It limits your charge rate! The DUO can do 10 Amps!

07-17-2008 01:35 PM

beeflyer2
Key Veteran
Location: Woodstock, GA

Quote
There’s a reason Hyperion do not charge though tiny, high resistance wires. - It limits your charge rate! The DUO can do 10 Amps!

So can the Cellpro 10S! However, for charging 4 amps and under, the main leads are not needed.

07-17-2008 02:00 PM

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