LiPo Noob

[F1Atom]

I am sick and tired of the NiMH packs. I am planning to go Lipo. However, I am afraid of what might happen if I mistreat Lipos. I seen a lot of videos of packs blowing up and catching on fire. The last the thing I want is to burn down my house and waste lots of money.

Can anyone give me advise on how to use LiPo's properly (charging, use, discharging, etc...)

I'm am planning to get the Blade CP pro charger with AC adaptor and a 8 tooth motor with a 11.1v 1200mah or above lipo batt. Something to start with. Since I'm still learning I want something with long duration.

[kgfly]

Some lipo safety rules

1) Never leave a lipo charging unattended. Check that the lipo is not getting hot or puffing during charging.

2) Charge in a fire-proof container (eg saucepan, terracotta pot, pyrex casserole, ammo box, cinder-block) and preferably outdoors and not below any flammable materials.

3) In general, never charge above 1C (eg 1.2A for a 1200mAh pack).

4) Never allow to discharge below 80% capacity.

5) After a crash, always isolate for at least 30min in a fire-proof location.

6) Get a decent charger/balancer setup that allows you to monitor the charging process and total recharge into the battery to ensure you are not over-discharging and help you get maximum lifetime from your batteries.

7) Always discard a puffed battery.

Charger I suggest you don't waste you money on the BCP charger. If you think you will be sticking with nothing bigger than a TRex450 or similar 3S-4S heli then look at the FMA Cellpro4S or the eStationBC5. These are integrated balance chargers that charge each cell separately for maximum safety and lifetime.

If you think you might go to a T600 or similar 6S+ heli then look at the eStationBC8 (integrated balance charger for up to 8S) or the eStation902+PB6 (charger+balancer for up to 12S) or the TP1010+210 (charger+balancer for up to 10S).

All of these chargers will require a DC power supply in the 12V-15V and 12A-20A range. Something like a 13.8V/20A is ideal. Heaps of power for where you are now and plenty of headroom even for charging large 10S packs in the future.

[F1Atom]

Thanks for he info. I going to purchace my first Lipo pack. Kinda scared though. :shock: :(

[F1Atom]

Ladies and Gentlemen I am the proud and terrified owner of a LiPo battery. My first one yea!! I haven't used it yet cause I'm waiting for my power source. Anyway, I have question: what are you supposed to do for the first charge on a new battery pack? The pack I have is 11.1 v 1250 mAh. I checked using my volt meter it read about 12v. Should discharge the pack a little or do I just charge it.

When I am flying should I time my flight to ensure I don't over discharge the battery?
What should I do?

Another thing whats the estimated flying time on this pack. I'll be using a 8 tooth pinion motor on the Blade CP.

[F1Atom]

I forgot. Speaking of a power source. I have a bunch of AC/AC adaptors around the house and I was wondering if it is possible to split the wires both positive and negaive and use that? The requirements for the charger are that it has to be 12-15 volts with a max current of 6 amps. Currently, I have 12 volt charger that gives out 500mAh. Can I use this as a power source? Is it safe or should I wait until I OEM power source comes in.

[kgfly]

First cycles
You can simply charge the battery. One of the benefits of Lipo is that unlike NiCd or NiMH, they are not affected by partial discharge/charge cycles. Lipo cells are nominally 3.7V but 4.2 when fully charged. Hence your 3S 1250mAh battery has 3 cells in series with a nominal voltage of 3 x 3.7 = 11.1V and a fully charged voltage of 3 x 4.2 = 12.6V.

Many people recommend gentle use to no more than 50% discharge for the first 5 cycles. In your case this means gentle hovering and FF with no climbouts, piros or acrobatics and a flight time of maybe 3min the first cycle then add 1 min each cycle.

Time your flights and monitor your recharge
Yes, get a digital kitchen timer and use it to time your flights. Set it to count down and land within 10-20 seconds of it expiring and beeping at you. I use a small velcro strap to hold my timer to the base of the Tx antenna.

You goal initially is no more than 50% discharge (=> recharge is no more than 625mAh) and in the long term, no more than 80% discharge (=> recharge is no more than 1000mAh).

What charger/balancer combo did you buy (I hope it shows you the total charge put into the battery) ?

I am unfamiliar with the expected flight time of a BCP with that battery so be conservative. 3min for your first flight, then recharge and see how much went back. Increase by 1min each flight until close to the target discharge (50% initially).

After your first 5 cycles you can get more aggressive with your flying but remember that it will use more power so always check your recharge amount and adjust you flight time to suit your flying style. It might take 10 or 15 cycles to find a safe time limit for your normal flying style, don't get impatient or be tempted to fly "just a bit longer" or your risk reducing the lifetime of your battery.

Always remember to disconnect your flight battery right after flying. Many a lipo has been killed by being put back in the car/on the shelf while still plugged in/turned on inside the heli. This is one area where a lipo alarm can be a real boon.

DC power supply
You typed "AC/AC adaptors" but I am guessing you meant AC/DC. To charge your lipo at 1C your charger has to ouput approx 1.3A at 12.6V = approx 17W. Assuming the charger is 90% efficient that means the input will need about 18W. So you need an AC/DC adapter that can reliably provide 18W@12V => 1.5A.

Hence no, you cannot use a 12V/0.5A adapter and you should wait for your OEM source which I am guessing has an appropriate output rating (eg 13.8V/12A, 12V/10A or similar).

[F1Atom]

Thanks for the info. Being new LiPo has given me lots of questions ask. So.. Thank you for your responses and patience. I got a Common Sense RC charger + balancer. It charges and balances through the balancer plug. And yes it does show the total charge of each cell. I'm a little confused about the 50% discharge. It means no more than 50% of the pack, right.

When your done recharging the pack, the pack doesn't have to be warm to use right?

About storing the pack. What the way best for storage. I'll be going to school soon so I'll only be able to some flying done during the weekend (If I'm lucky).

[kgfly]

Hmmm, I think that is an active balance charger (charges each cell separately) which is good, but last I heard, although it displays the per-cell voltage, it does not show the total mAh pumped back into the battery. This means you cannot tell how much the battery was discharged.

For example, if your 1250mAh battery was 50% discharged you would expect the charger to put 625mAh back by the end of the charge. If you charger does not report the total charge put into the battery then you cannot tell how much was taken out to start with. I hope I am wrong and that charger does indeed give you this vital information.

Never charge a hot battery (right after flying). Always allow them to cool to close to room temperature. Charging at 1C they shouldn't really even get warm and certainly not hot. If they do, let them cool to ambient temperature before flying.

If you live in the frozen wasteland and have icy winters, then keep you lipo in your jacket at about body temperature until just before flying. Lipos do not perform well at freezing temperatures nor should they be charged at low temperatures.

Storing for a week requires no special preparation, just charge and store. One of the big advantages of lipo is the low self-discharge so when you come back in a week, it will still be 95% charged and you can just go fly.

If storing for an extended period (say 3months) charge to 75% (or discharge down to 75% from 100%0 and store. For maximum shelf life, store in the fridge (NOT freezer). When the time comes, a quick top-up charge and off you go.

[F1Atom]

Unforntuately, this charger doesn't tell you how much the battery was discharged, suxs. So how can I keep track now.

After I'm done flying should the battery be warm or just barely warm or hot?

I have it on the charger now I just got the OEM power source. It looks like something you use on a Lap Top. I'm watchin it like a hawk!

[kgfly]

I am afraid you are out of luck in terms of monitoring your discharge /recharge with that gear :(

I would suggest you keep researching to find out typical flight times for your overall setup and use that as your guidance. You could also mount a small lipo alarm on the heli to give you a warning if you are flying too long. You can get a good one here: http://www.helifreak.com/viewtopic.php?t=21253& and see here for some more discussion that might be helpful to you: http://www.helifreak.com/viewtopic.php?t=276328&

At normal room temperatures the batteries may get warm or very warm but should not be too hot to hold comfortably. One simply test (sounds odd I know) is to hold the battery to your lips. If that is painful then the battery is too hot. Of course if it is 100F ambient the battery will get hotter than normal and you should fly less aggressively or for shorter times to prevent overheating.

Happy flying :)

[F1Atom]

I think I'll be timing my flights to prevent damage.

[Efliernz]

I post worldwide - over 70 of these alarm now flying, 40 thanks to Helifreaks :D

Thanks for the support Kenneth - and your good advice on the lipos found above :D

[F1Atom]

How do you hook the lipo alarm to the battery or heli?

[F1Atom]

I am unable to check how much mAh hours are put back in the pack because my charger doesn't display it. So... would it be ok to base your flights on voltage? For example, right now I am timing each flight until I get to at least 10v on the pack. Once I determine that I will fly until that time is reached then check if its 10v, then recharge from there. For example, if 10 mins of flight will leave 10v left in the pack then I fly for 10 mins only. Would this be good practice to keep my lipos from dying early?

[kgfly]

The lipo alarm sense wires get wired into the ESC connector so that when the battery is plugged into the ESC, the alarm sees the battery voltage.

[kgfly]

When are you measuring the 10V ? If it is 10V at rest then it is likely to be much less under load. I would say you are probably discharging too far.

My batteries are (almost) never less than 11V at rest 5-10min after a flight, typically 11.2 to 11.4V. I am conservative about it, I fly only 7:30 on my setup as I would rather get >100 flights 30s shorter than 50 flights 30s longer. A few times I have forgotten to (re)start my timer or otherwise gone over time and hence gone a bit lower, but that's where my lipo alarm (set to 10.3V) has kicked in and saved me from damaging my lipos.

[F1Atom]

So.. should I stay above at least 11v at rest? I was going for 10 mins on the pack but if my tests show that it will drop below 11v, I am more than willing to just fly for 8-9mins or shorter. So far, the longest I have flown was 5 mins and after checking the voltage at rest it read 11.90v. The 8 tooth brushed motor got pretty hot to the point where I almost couldn't touch it for a long time. It was flown indoor mostly hovering. I checked the temp with a temp probe it was about 90 degrees F more or less. Would this be normal? I have a heat sink on it too. I think have give it some breaks too kool off. I have 11.1v 1250mAh pack. What kind of pack do you have?

[kgfly]

Yes, aim to stay above 11V at rest. Those brushed motors can get very hot and do need a rest after a few minutes to cool down. Do you mean 90C ? After all 90F is less than your body temperature (96F) so would certainly not be too hot to touch, whereas 90C is almost boiling. If 90C that is dangerously high as the magnets in the motor will start to demagnetise. It is possible your gear mesh is too tight causing the motor to work too hard. Try and find someone near you that knows about BladeCPs or maybe put a post on the appropriate forum here in helifreak about your motor getting hot. Provide details about the heli, motor, esc and battery.

I run Hextronik 3S1P 2200 12C/16C in my TRexSE.

[Pinecone]

I would fly an extra minute then check the resting voltage after 10 - 15 minutes. If above 11, then fly an extra minute the next time. Keep doing this until you get to 10.8 - 11 volts resting.

The other thing is, fly your 5 minutes, borrow a charger than tell how much you put back in and charge it. You can then calculate the max safe flight time.

Here is an Excel safe flight time calculator.

[F1Atom]

I'll do that as soon as I find a another person with a good charger that tells mAh.

[F1Atom]

To: kgfly. I checked the gear mesh with the paper btwn the gears method. So...it should be just right. But I'll check that again. I flew it again today and it wasn't as hot cause I flew it outside. The other hot flight was indoors.

[F1Atom]

Sorry for all the questions but unfortunately I have more.

Just wondering what are the S & S (signs & symptoms) of Lipo death? What should I expect, what should I look out for when my pack is dying?

Next question, has anyone ever figured out mAh with using math equations (by hand). I know it won't be exact but it would be nice to just get ball park of how many mAh are being put back in. So far, my cousin has come up with this equation:

mA X mins charged/60=mAh.

In my case, I always charge below 1A at 0.6A. So my equation would be
600mA X 15mins charged/60=150mAh put back into the pack.

Would this equation work? or is there something better.

[kgfly]

S&S if Lipo failure:
- reduced capacity
- puffing of the pack (swells up)

Recharge equation:

Lipo charging is "CCCV"= Constant current, constant voltage. The first phase is constant current, in your case, 600mA. When the pack voltage reaches 4.2V/cell, the charger switches to constant voltage and monitors the current. End of charge is when the current falls to some low level (eg. 0.1C or maybe 100mA).

Your equation is correct in simple terms, but due to this CCCV behaviour, will give an over estimate of the recharge. Lipos typically recharge to about 80% at the CC mode then take quite a while to complete the last 20% in the CV mode.

In terms of checking your flight time, overestimating the recharge is safe in that it would tend to make you fly for a shorter time than actually needed to stay below 80% discharge. The problem is that the error could be so large that it would be unreasonably restricting your flight time. Try it and see and let us know how it goes.

[F1Atom]

So far so good. I have flown my longest flight of 8 mins. I had to break it into two flights ; one 5min flight and a 3min flight to keep the motor kool. But a soon as the timer went off I landed and measured the resting voltage and it was 11.50v. During the recharge it took about 56 mins to get fully charged. Using the equation above (mA X mins charged/60=mAh) I roughly put back 560mAh back into the pack more or less. It looks like I could fly at least for 10 mins maybe more. The only problem is I have land to kool down. I can't fly it for the full 10 mins like I used to on the NiMh batt. What do you guys think?

Thank You!

[kgfly]

Sounds good so far. Take it up 1min at a time and certainly do keep breaking up to allow the motor to cool down.