Hi Guys,

As the subject says a friend of mine has a G.T.Power V5 battery charger and i was planning to buy it.. Any of you guys ever used it ? Also i would like to know some tips on how to take care of your lipo batteries...

Cheers

Atul G.

Looks like similar to the IMAX, Turnigy etc (wonder if the same people actually manufacture them all).   Here is an intro video.



The only real worry on these economical chargers is how good they balance the cells (as compared to the expensive ones like from Bantam).  See online if anyone has done tests on the individual cell balancing capability of this charger, and if it is OK, go ahead.

The only thing I would suggest is that you might want to go for the 6cell one for the long term (assuming availability and affordability/budget).  Actually after 3 cells, the most widely used cell count is 6 cells.

There are many threads here that talk about Lipos and how to take care of them.  If you have gone through them, and then have questions, please ask.

The important things are :

1. Do not overcharge
2. Do not over discharge
3. Always use a balance charger
4. Store for long term at half charge
5. Do not keep them in the sun for long
6. Be aware of the fact that they are volatile, so prevent the connection leads from short-circuits etc.

Hi Anwar,

Thanks for the video and actually surfing it out from youtube for me..Cheers 

I thnk this charger pretty much serves my purpose, thanks for the tips for lipo battery - long life.. 

I am going to go in for a hyperion 2100mah frm sunil in somedays, i thnk its an awesome buy for the price offered..

chan's got one battery i guess, would really like a little review here..chan shoot away..

good night people..

had a good party.. Cheers

I know the rule does not apply to the new Hyperions, but it is always recommended that you charge at 1C or less. I should have mentioned this in my list above. 

1C means that you charge a 2100mah battery at 2.1amps. 

Hi Anwar,

I want to know, how does the calculation work ? If i try to charge a completely discharged 2100mah battery by plugging a field charger to my car battery, how much time does it take or how much does this drain your car battery ? ..

I have charged 1000mah on my car battery a couple of times, is tat fine ? All the guys charge their batteries on their car is this reccomandable ?  

thanks man.. good day

You should not completely discharge your lipo.  Typically, you should not let it come down below 3.2volts per cell.  Another way to look at it is, when you recharge the battery, you should be putting in no more than 80% of the rating of the pack.  So for a 2100mah pack, you should be putting in about 1625mah back while you are recharging it, and most of the balance charges will tell you how much you are putting back. 

Balance charging of a lipo at 1C rate will take 45 minutes to 1hour, since the last part (last 10%) is done using trickle charging for the purpose of balancing.  Many charges allow you to "fast-charge", which is typically much less time of a full balance charge, where the pack is charged to 90% of the capacity quickly and the last trickle charge part is skipped.

Charging a pack using car batteries is fine, but how many packs can be charged depends on the Ah rating of the battery also.  If your battery is 30Ah, you can charge a 2100ah battery 30000/2100 which is roughly 14 times ideally. Now give about 20% for various losses, so charging 10 packs should be possible before the car battery runs out. So charging 3 or 4 times is typically not a problem.

By the way, the 30Ah capacity for a car battery is just an example value, typically it is higher.

neat stuff, so on an average a 1000mah battery would take abt 1 hour and drain out only 1amp from the car battery.. tats wat my trainer told me..so even if i charge 2 or 3 times on the field is not a problem..The car battery can be easily recharged while going back home  

Oh yeah anwar, i checked for the individual cell balancing capability of this charger & it has an inbuilt individual-cell-voltage balancer so it does not need a separate balancer when charging LiPo batteries.

Many people use their car batteries to charge Lipos. But I am not very comfortable with it. We all give a lot of thought to Lipo batteries and not to the card battery. Usually, the car batteries (lead-acid) are designed to give a momentary (high) current drain to start the car engine. They are no good for constant high current discharge.

In Lipo charging we often charge the batteries at 2A - 3A. The poor car battery nearly chokes when you draw that kind of power for a long time. Further, when the Lipo gets to the trickle charge stage, the chrager draws pulses of current (again 2A to 3A) from the car battery. Generally, batteries hate pulsed current and it will reduce the life of the car battery.

I have seen noticable change in my car battery power after charging Lipos for about 20 - 30 cycles spread over a long period of time. I would highly recommend a separate power source for the Lipo charger like an SMPS or  if you could afford get a separate car battery + charger exclusive for RC use.

Just my thoughts on the subject. - Keep your car happy!

-Ismail

Agree with Ismail. Even though it is OK in general,  charging using a car battery should not be the primary means of charging.

Quote from: atul_pg on July 12, 2009, 10:33:17 AM
Oh yeah anwar, i checked for the individual cell balancing capability of this charger & it has an inbuilt individual-cell-voltage balancer so it does not need a separate balancer when charging LiPo batteries.

It is important not only to make sure there is a balancer in the charger, but how good the balancer is.  This is where the "you get what you pay for" comes in, and the biggest complaint about some of the lower-end chargers.  After charging and balancing, a good charger will have all the individual cells in the battery close to 4.20v each (within like 0.05volts).  If the different cells are like 4.1v, 4.0v, 4.2v etc, then the balancer is questionable. 

My understanding of the car battery is slightly different. They are built for high current, but not deep discharge. They should not be discharged to more than 50% or so of their capacity. They have more thinner plates for high current discharge.

The batteries used for inverters and UPS are of deep discharge type with thicker plates. These have lesser current discharge rates than the car battery.

One thing that was missed in the discussion about mAH taken out of car battery was the voltage coversion in the charger SMPS.  For example a  2S 2100mAh battery (I approximated to 4.2V/cell constant for ease of calculation) will take out 2100*(4.2*2)/(12*0.8)=1837.5mAh out of the car battery. A 6S 2100mAh will take out 2100*(4.2*6)/(12*0.8) =5512.5mAh. The 0.8 number is the 80% efficiency assumed for the charger.

The charger balancing difference I have seen reported is less than +/-0.05V. I don't think it is critical. See the thread http://www.rcgroups.com/forums/showthread.php?t=775766 where some people habitually bashing these cheaper chargers disappeared from the scene as soon as they were challenged to give a technical reasoning for their bashing.

The balancer voltage difference is an issue (may be it is just for purists) mainly because of hard numbers posted by the manufacturers themselves. What their technical reasons are for such a strict guideline, I am not sure. I haven't seen much useful information on it, may be because it is all cell chemistry issues.  Almost all of them are very strict about not going over 4.2v per cell.  Why not 4.4v (or even 4.3v) ? So even 0.1v difference is cautioned against.  And if the balancer is not good, you can end up with cells going over the 4.2v limit (on a 3 cell pack, you can easily end up with 4.0v, 4.2v and 4.4v, and the same thing with over discharge on the lower end). 

It is to be remembered that the discharge is provided as the cell voltage goes from the range of 4.2v to 3.2v, whatever the capacity of the pack is.  So each 0.1v is providing about 10% of the capacity of the pack, which can imply that a 0.1v difference is a significant deal (I guess I am over simplifying it by assuming it is all linear).

You are right about calibration issues.  The best you can do is measure with different tools.

Quote from: RotorZone on July 12, 2009, 11:40:52 PM
They should not be discharged to more than 50% or so of their capacity. They have more thinner plates for high current discharge.

This is why I was suggesting around 3 charge cycles as the safe limit (for the sample case), before the car battery is discharged too much.  And this is consistent with what I have seen people do on the field.  Most people who are serious about field charging bring a separate battery (most of them are the "no maintenance" type).

I have seen reports a few years back about a study where going above 4.2V/cell decreases the life span dramatically (very dramatically if it catches fire ). Going over voltage is the one concern I had raised also, but again even a charger using 1% components could go upto 4.242V. Electronic components do age, the voltage is likely to vary a bit over the years. I have come across components that varied significantly after a year of use. That component was dissipating a lot of power so that might have accelerated the aging, but it does happen on all components. So if your charger goes to 4.2V exactly when you buy it, it could be different after some years of use. Given this, I think people are loosing sleep unnecessarily over a few milli volts.

Going by with the same logic, one can deduce that if you started with a bigger difference in voltage levels, then after some use  it would become an even bigger variance down the line.  And these bigger variances could be bordering on the tolerances of these fragile beasts.

Yes, I agree. The conclusion I have arrived at is that if all the cells are below 4.2V I don't worry about the slight imbalance. If it is higher, then look at alternatives, there is some info out there about recalibrating these chargers.