Multi-Rotor Thread

[Clive]

[sinbad]

Some nice stuff from 4 min.

Now that"s some awesome stuff, i need them to spend 10 minutes on my quad, awesome stuff.

[SoutherlyBuster]

Zac and I are having some trouble with charging our Li-Po battery. When we first bought it, we charged it up directly to our car battery. We typically got 20 to 30 minutes of flight time per battery, this is for a glider, switching between power on, then power off to glide some.

After two battery use/charge cycles, we only got 3 minutes worth of flight time. For this run the charge was done again directly to the car battery, but did notice after 2hours the green light on the balance charger did not go out. We thought it was because of the cold garage where we where charging the battery. So we bought a 240 AC to 12 V (1.5amp) power supply and started to charge the battery inside the house where the room temperature is 18 degree C. After about 2.5 hours the green light was still on, indicating it thinks the battery was still not charged. This does not sound right as Zac reckons the package said it charges within 1 to 2 hours. We unplugged the battery fearing that we would damage it.

Here are the battery specs: Hobby King, Li-Po Battery High Power searies 20C 11.1V

and the balance charger specs: Hobby King 2S/3S Li-Po Balance Charger, 12DC 1.2A input, 11.1V output.

We just measured the no load voltage of the battery at 11 V but don't have a clue how much that will drop once load is applied.

Any suggestions?

Thanks in advance,

Zac and Norman.

[SoutherlyBuster]

Some more info. After charging this morning for 2.5 hrs, still no green light off but went flying anyway. Outside temperature 9degC. Batteries only lasted for 2 minutes before the ECS automatically shut off power to the electric motor, but enough power for the servos to operate and get the plane back down to earth safely. The battery voltage after this droped from 11V to 10V.

If we just leave it plugged into the charger and keep charging until the green light goes out is there any danger in wrecking the batteries provided we monitor the battery for signs of heating/bulging?

Regards,

Norman.

[BobM]

A long time ago when I was playing with electric RC cars, I had two types of charger: one was a slow charge which would take 14 hours from flat to full; and the other was a fast charge doing the same job in under one hour. The advice at the time was to use the fast-charge sparingly as it tended to chemically alter the battery's internals.

I'm not sure if this is still relevant with today's chemical batteries.

BobM

[Goz]

LiPos don't like the cold if your having particularly cold weather it could be affecting the batteries, but it sounds like your charger may be having issues.

Try warming the batteries up before using them in cold weather it will improve the flight times.

It's worth ivesting the money in a decent programmable balance charger. I find the AC/DC ones to be pretty handy I got myself an Imax B6AC Charger which is pretty good for the money.

http://www.hobbyking.com/hobbyking/store/__6478__IMAX_B6_AC_Charger_Discharger_1_6_Cells_GENUINE_.html

I was looking at this one the other night and it looks pretty good value as well.

http://www.himodel.com/electric/SKYRC_T6755_110-220AC_11-18DC_Input_Touch_Screen_55W_1-6S_Charger_Discharger.html

[SoutherlyBuster]

LiPos don't like the cold if your having particularly cold weather it could be affecting the batteries, but it sounds like your charger may be having issues.

Try warming the batteries up before using them in cold weather it will improve the flight times.

We effectively did that today. Had the batteries charging in our house, then went straight to the field before the batteries had a chance to cool down.

It's worth ivesting the money in a decent programmable balance charger. I find the AC/DC ones to be pretty handy I got myself an Imax B6AC Charger which is pretty good for the money.

http://www.hobbyking.com/hobbyking/store/__6478__IMAX_B6_AC_Charger_Discharger_1_6_Cells_GENUINE_.html

Just looked this up and saw this comment:

Why is it that Hobbyking keep removing this message? I have just received one of these chargers. It will not charge 2S or 3S LiPos when on mains charging but it will charge 4S. When on 12V supply it charges 2S, 3S and 4S. I have seen that others have had the same problem.

Do you have this problem?

I was looking at this one the other night and it looks pretty good value as well.

http://www.himodel.com/electric/SKYRC_T6755_110-220AC_11-18DC_Input_Touch_Screen_55W_1-6S_Charger_Discharger.html

Fancy unit. Don't think I need that fancy, PC controllable, just need one that is reliable and works.

Some other sites give more details on charging such as

http://www.chargedrc.com.au/Battery-Stuff/read-before-you-charge-your-lipo.html

Here is where it gets interesting. They way I read it, you are supposed to charge the Li-Po's at their maximum voltage of 4.2V per cell, so for a 3S1P (3 in series) that makes 12.6 V, but the balance charger says input voltage of 12V and the 240V power supply we have outputs 12V (I measured it, 12V spot on). Should we then be charging at 12.6V not 12V?

Actually the first time we charged the batteries sucessfully was with my wife's car battery -- I'll go and measure what the voltage is. Ok here's what I found: my wife's car battery outputs 13 V (did charge first time ok on this), my car outputs 12.5V (never got the charger to get a full charge using this). I'll now swap over the charging from my wife's car and see if that fixes the problem.

But point taken, think we need a better balance charger, the ones around $30 have readouts to diagnose problems like telling you the voltage across each cell.

Thanks again for the tips.

Regards,

Norman

[Goz]

Mine has charged everything I have thrown on it so far, I mostly use 2S and 3S batteries mostly. It has wierded out once or twice on power on but restarted it and everything was fine.

The main thing with the charger is to make sure it balances the cells properly, it's also handy if it has settings to drain the batteries to a safe storage level as well. It's worth getting one of the battery checkers to check the balance and charge levels of your batteries in the field and after charging.

[Oooo]

if you want to find out about lipo batterys go to helifreaks web site,iv found out a lot of info at heli sites, the other thing it takes about ten charges with a good charger to get them to their full potential from new and to hold a full charge with a decent charger, then the other most important thing is NEVER fully discharge while using them either !!! as this is the quickest way to kill a lipo you should leave about 20-25 % (I think from memory ) in the battery eg I have 3s 11.2v 25c lipo in my blade 450 3D heli at a normal speed doing hover and basic stuff I get 8`10 min fly time if it dose 3d 100% power I get 7m30s fly time , now if you are not going to use them for awhile then 80% charge them this is called a holding charge as they don't like to sit fully charged either . NOW the scary part LIPOS DO EXPLODE get a charge sack and NEVER leave them while charging ,even a drop on to hard ground from waist height can cause a prob and the can go bang !! but lipos have great power ,and by the way your not allowed to carry them on planes either so I found out opps

regards mick

[SoutherlyBuster]

Thanks Goz and Wolife.

I think we are sort of converging to the same answers, but hey some experience from those that have had them much longer than us helps a lot. Most appreciated.

Charging one of the batteries last night on my wife's 13 V car battery -- no change, still not charging to full.

So I get out the volt meter and check the charging leads to see what is across each of the cells:

1st battery: cell 1: 3.7 V; cell 2: 3.7 V; cell 3: 2.8 V (after attempting to charge)

2nd battery: cell 1: 3.7 V; cell 2: 3.7 V; cell 3: 3.0 V (after using in the field)

well there is the problem, the balance charger is not doing it's job properly, the charges are unbalanced.

The plane Zac is using has an ECS with an automatic low voltage cutout switch for the motor only. As soon as this cuts out, we glide the plane to the ground (servsos still active) and stop flying with those batteries.

So a bettery balance charger and a fire proof charging sack is next on the list.

Yes we know about the blowup scenario, as soon as air gets to the Lithium it sets on fire. We have not dropped the batteries and they never felt hot, just a bit warmish. The fact that we have different brands of batteries, points to the balance charger being the problem.

Regards,

Norman and Zac

[Oooo]

yes norm that can be an issue with some charges I brought a twister heli before I knew about them and the charger that came with it did ok till I put it on my hitek x2 which can do two batts at a time blance and charge ( now this charger is what they call low end ) runs of a power pack mains psu I run it at 17.9 volts and will charge my 450-3D batterys in about 20 mins or if I bump it up in the amp department I can do two batts in 15 mins but not good to fast charge all the time there are some good charges out there and not so good the biggest thing is the power supply seems to be the most important bit some make their own out of computer power supplies lots of fun tho altho cost can be a prob !!

[SoutherlyBuster]

Thanks Mike,

So you reckon the power supply choice is important. From reading of the charger specs some need power inputs in the range of 5 amps for 12 V, that's a fair amount. The Dicksmith power supply have only outputs 1.5 amps. So what aspects of the power supply did you find important?

Regards,

Norman.

[SoutherlyBuster]

Thanks Goz and Mike. Zac and I have been scouring the HK site reviewing the chargers. Well it turns out the unity that you suggested Goz, the "IMAX B6-AC Charger/Discharger 1-6 Cells" is the best fit for us, it also includes a built in power supply. It's the USA style but all we need to do is get one of those $2 converters for our style of plug as it accepts 240V as well.

We also checked out the protection bags, there is a "Lithium Polymer Charge Pack 18x22cm sack, should do the trick.

Cheers,

Norman and Zac.

[Cesium]

I don't usually post here, but this time thought I would to help someone save time and money.

Your battery charger might well be below par, but the real problem is your battery - it's buggered, throw it out. A 2.8V readout on a lipo cell at rest is terminal and indicates permanent damage. When the battery is under load, that cell's voltage will drop even further and that's why your ESC is shutting things down.

HobbkyKing batteries are in my experience, average at best and often very poor, especially the bottom-of-the-range blue Zippy packs. Before learning my lesson, I had several brand new packs drop cells (3S pack suddenly becomes 2S, etc.) on the first flight, and some even arrived puffed and gassy before they've even been used. Puffing was a real problem with the yellow Rhino packs and I won't bother with those anymore.

Another thing to consider is that HobbyKing vastly overstate the C ratings on most of their packs, and if you actually try to draw the amps that should be sustainable, well...watch the battery fail before your eyes. A genuine 2200mAh 20C pack should be able to supply and sustain 44A, but those blue packs will never even come close to that before shitting themselves. You'd be lucky to get past 20A.

I've had a lot better luck with the Zippy Compact batteries, so maybe they're a different chemistry, process, something? The 2200mAh 3S 35C packs are a nice light weight and serve about 15A in my Wildcat at full throttle without any drama.

For properly high performance models, I'd recommend Hyperion and ThunderPower, though it would seem silly to put an $80 battery in a $60 foamie.

[Oooo]

https://sites.google.com/site/tjinguyte ... evision=10

a lot of good info here norm good reading iv learnt a lot from here and as ces said some brands are better than others id have to agree there as I have several different types some are a little puffy and others are still good the puffy ones at the mo are just my hover packs no cockpit on so if they do go I can get it out quick plus I have extinguisher there too as have seen three fires now and don't want mine to go that way too have drained as per this site and desposed off no probs

[Oooo]

Yep norm thats why a lot of people convert computer psu's one they have inbuilt cooling fans they work well under load ESP for charging as some charges draw high amps which help with charging my power pack can run at 5 amps 1000 watt my charger is a twin port and I can charge two batts in 20 minutes easy but sounds like you have researched what ya need so will be good most heli guys start small then up grade as helis get bigger lol mine will do up to 12s but will take round 45mins so I'm told

[SoutherlyBuster]

Your battery charger might well be below par, but the real problem is your battery - it's buggered, throw it out. A 2.8V readout on a lipo cell at rest is terminal and indicates permanent damage. When the battery is under load, that cell's voltage will drop even further and that's why your ESC is shutting things down.

If we had just the one battery having this problem, yes but we have the same problem with two batteries each of which are a different brand.

The first battery is a "Hobby King" 20C 11.1V. This came with the plane.

The second battery is a "Turnigy" 20-30C Discharge 1300 mAh, 3 cell 11.1V

These are the specs read directly off the battery not what is published on Hobby King.

Looking just at the price we paid for the above this was $9 to $10 each, most of the batteries from Hobby King with the above spec are around the same price. So did we really go that wrong with the quality?

HobbkyKing batteries are in my experience, average at best and often very poor, especially the bottom-of-the-range blue Zippy packs. Before learning my lesson, I had several brand new packs drop cells (3S pack suddenly becomes 2S, etc.) on the first flight, and some even arrived puffed and gassy before they've even been used. Puffing was a real problem with the yellow Rhino packs and I won't bother with those anymore.

We did not purchase Zippy pack, nor a Rhino pack. But point taken there are some that you have found to be no good. For our next battery purchase will steer away from them.

Another thing to consider is that HobbyKing vastly overstate the C ratings on most of their packs, and if you actually try to draw the amps that should be sustainable, well...watch the battery fail before your eyes. A genuine 2200mAh 20C pack should be able to supply and sustain 44A, but those blue packs will never even come close to that before shitting themselves. You'd be lucky to get past 20A.

This now raises the question of whether we attempted to draw more power from the batteries than we should have. We looked up the specs of the motor, nothing stated. Remember this is a for a glider. The ECS that came with the glider was rated at 20A, so I would think that 20C batteries should be fine. The first three sessions we had with these batteries were great. Things only went pair shaped once we charged in the garage at lower temperatures estimate 10 degC.

Don't under stand where you got 44A from? If the battery says 20C I would have thought that for a series connection that 20 A is all that it will deliver.

I've had a lot better luck with the Zippy Compact batteries, so maybe they're a different chemistry, process, something? The 2200mAh 3S 35C packs are a nice light weight and serve about 15A in my Wildcat at full throttle without any drama.

I know you can't go purely by price, but the Zippy Compact batteris are about the same price as what we paid for our batteries.

For properly high performance models, I'd recommend Hyperion and ThunderPower, though it would seem silly to put an $80 battery in a $60 foamie.

After a quick look could not find a supplier of the Hyperion's but did spot one for the ThunderPower. Looking at the ThunderPower for similar specs to what we have, they were $30.00.

I sill reckon it's purely a charger problem. If the charger is playing up and not charging the one cell, perhaps our batteries are then still OK, just not balance charged. I talked with Zac again and he said the second battery, the Turnigy definitely had no hard landings.

So unless I've got some thing wrong, the next logical step is to upgrade the charger. I appreciate your feed back Cesium, but I'm not yet convinced that our batteries are ruined.

Mike: Thanks for the link, lots of useful info there.

Regards,

Norman and Zac

[Goz]

If your ordering up a new battery charger Norman grab a couple of Onboard Low Voltage Indicators, well worth the couple of dollars each.

http://www.hobbyking.com/hobbyking/store/__18987__On_Board_Lipoly_Low_Voltage_Alarm_2s_4s_.html

I bought 1 for each model as a precaution against running packs to low.

As for C ratings

1C on a 1000 mah pack would be 1 amp max draw

1C on a 2200 mah would be 2.2 amps max draw

so 20C on a 2200mah pack = 44 amps max draw

Always worth spending a bit more and getting packs that are rated a bit higher than you want to use.

[jhn.holgate]

I think either your charger is stuffed or you're trying to charge the battery at more than the power supply can cope with. I don't think you can charge a battery at 2 amps if you've only got a one amp power supply. 3.7v is very nearly empty. 2.8v certainly is. Not sure about the lipo packs, but my lithium ion torch batteries come back from 2.8v ok - but they have a protection circuit that cuts out at that voltage.

I've had no trouble with any of my Turnigy packs. I have a cheap Detrum hobby charger that can charge to 5amps but I only have a 2 amp supply so I make sure all my charge currents are well below that.... I assume your charger allows you to set the charge current? But if you're reading 3.7v on the cells, then they are not being charged.

I think most of my packs are around 1800ma to 2200ma and I set my charger for 1000 to 1500ma (so I don't bugger the power supply - which did not come with my charger). It's a current controlled charge - it will apply my current limit (ie: 1000ma) until the battery reaches 4.2v, then it reduces the current by whatever amount it needs to hold the battery (or cell) at 4.2v until the current falls to around 100ma then it's done. Lipo's explode around 4.4v!!

edit: your input voltage of 12v has nothing to do with your charge voltage...and yes, they should reach 4.2v per cell.

[SoutherlyBuster]

Thanks Goz,

Ok I've got some to learn.

So the units of the "C" is actually 1/hr. I assume this "C" is not capaictance. Capacitance has the units of farads or coulomb/volt .

So the 20C means 20 1/hr

So the amp draw is 20 1/hr x 2.200 A.hr = 20*2.2 A.hr/hr = 44 A

arg why didn't they just state what the units are. Ok Cesium I stand corrected.

The onboard cell checker, good idea I was wondering about those for pure glider flying where you don't have an electric motor to signal when the power is low. At only $2 can't go wrong. Much appreciated.

PS. Just saw your comments John,

Thanks. I tried charging on my car and the AC power supply, made no difference. My Balance Charge only needs 1.2A, but the one Goz is suggesting and the one I will get goes up to 5AMP and as it's own built in power supply. The elcheop charger I have is just plug in, that's it no option for setting any thing. Just a 7.4V and 11.1V output.

Regards,

Norman.

[jhn.holgate]

My pure gliders have Eneloop packs to operate the servos. I just have to make sure they're topped up!

[SoutherlyBuster]

My pure gliders have Eneloop packs to operate the servos. I just have to make sure they're topped up!

Jees my head is starting to implode . Eneloop, ok their are Nickel Metal Hydride batteries. Well I'm not there yet (was I ever??), my first pure glider will come after a trainer model, the trainer will have an electric motor.

Thanks guys.

[jhn.holgate]

Yep - Eneloops are NiMH and they are charged on the same charger as other NiMH batteries. Except they can hold their charged voltage for ages - so when you buy them (usually) they are ready to be used. When empty, you can charge 'em up and leave em sitting fully charged for like a year and they still have most of their charge. Hobby King have there own version (LSD - Low Self Discharge) for about $1.50 each. I've read good reports on 'em and have a bunch in the mail. All the different battery chemistry's have their own unique set of charging criteria which can get a bit involved if you like to know what's going on, but a good hobby charger is a great investment. Mine is a similar type to Goz's and cost about $50. It can charge my LiPo packs, my LiIon cells, my NiMH cells and packs and my lead acid batteries - it's brilliant

[SoutherlyBuster]

Thanks John. Yep, I'm getting there. I did notice that Goz's charger does all those battery types and figure it a good investment.

Mind you it is a bit scary with those LiPo's can't just let them stand for months at full charge. Figure I will get a tin can and fill the bottom with sand, pop the LiPos in a plastic bag and put them in the tin for safe keep in case things go pair shaped.

[Goz]

One of the neatest ideas I have seen for Lipo storage was a ceramic pot with a lid and put a clip seal bag of sand on top of the batteries. If there is a lipo fire the bag melts and dumps the sand on the fire.