Hi @policetac.

Quite often you can obtain the same voltage batteries with different capacities. So I assume your chopper is similar to this one here

http://www.yousky7.com/Skytech-M1-helicopter-parts-Skytech-M1/Index.html

Notice how you have an option to buy two different batteries? A 7.4V 1500 and a 7.4 2200ma in this case. As long as the batteries will fit and the voltage is 7.4 volt you could insert larger or smaller current batteries.

The advantage of the larger batteries (1800ma in your case) is that the helicopter will run for a longer period of time.

If you really like flying this helicopter, after a while, I encourage you to enter the world of collective pitch!. Its a crazy fast and addictive world of wonder. For example you can buy a helicopter that is huge and performs tricks like this! (note it takes along time to fly to that level but you can still do amazing things) The video below shows you how these things look on the inside and how they fly etc.

Its important you find the right people who can steer you in the right direction. In the world of collective pitch we have @ZEN RC who supply the sort of model you see in the video above and they are very helpfull and knowledable as well. So is @Jeff B who supplies alees helicopters. These people are passionate about what they sell and will set you on the right track.

But if you never venture into those waters, the heli you have above is still alot of fun... I started with a similar model to what you have and over time became hopelessly addicted.

I hope the above helps @policetac

 

YEP! That's the one!

First of all, I'd like to thank you for your reply. You are the first one who actually answered the question I posted instead of responding with something totally unrelated or motivated by sale.

Yes. I'd love to someday be able to upgrade to a better, bigger, faster, more complex bird, but for now this one's just going to have to do. As it is, I was only able to get this one because I got a real,ly great deal on it. (Although I have moved up to 4ch's on the really small living room models.)

I do have a followup question though.

If increased mAh equals longer flying time, is there a limit here? (Aside from size and weight restrictions)
Meaning,l if 1800 mAh's is good, is 5000 mAh's fantastic?

Thanks again. I'll be hanging out for a bit so I can reply a little bit quicker this time.

Again, thanks for the help.

policetac@yahoo.com

 

Hi @policetac,

Thanks for the compliment!... If 1800mah is good, 5000 mah will provide you with more flying time. But with helicopters everything must be in balance. If you go too big, you will find your helicopter might feel sluggish especially during maneuvers. And the balance of the helicopter might end up being off. Think of the battery mah like the size of your petrol tank.

I remember thinking exactly the same thing. I put in bigger batteries in my coaxial helicopter which was called a big lama. I took it to the field with eager enthusiasm. it was flying great but as soon as i tried to move quickly forward or in a turn the blades up the top would strike and cause a crash. So it would be a case of try and see really because it would be model specific. I would think however that increasing the weight over double that of an 1800mah much might be a bit much and it might be hard to make fit or it might be hard to make it fly right.

When using lipos, the battery must have 20% left in the pack after a flight - if you go lower, you can damage the pack. On larger helicopters we time the flight to make sure this does not happen.

It will be interesting to see how you progress. Please keep us informed as i remember being in a similar situation to you.

 

..."It will be interesting to see how you progress. Please keep us informed as i remember being in a similar situation to you."
Tell you what. I'll do one better. I'll even have my daughter post some video Which makes me have to ask, "Was that you in that video with that helicopter breaking the laws of physics I've spent all these years trying to violate myself?" (I work in theoretical high energy physics.) That's some pretty far out flying!

Yea, I kind of figured out that the whole lift to weight issue might be a finer line than I first imagined. I think I've literally spent most of the day just trying to find the right balance between the two as I decide exactly which battery I'm going to choose.

I think I found the right one with the Gens Ace battery found here: http://www.gensaceusa.com/98p-4000-2s1p-2222-rx.html

I'll give you a chance to check it out and put forth your opinion first if you don't mind looking at it.

It seems like it's a pretty decent price too from what I've found so far.

 

Yes @policetac it is a descent price and it is a very descent battery. The GensAce series batteries are quality. They are up with the best. The advantages of a good battery are:

* More power on demand.

* More cycles - you must not discharge this battery below 20% though - i cant stress this enough. If you do it doesnt matter what LIPO you use, you will destroy the chemistry in the battery and it will never be as powerful and its cycle life will be reduced considerably or maybe it wont recover at all. You could expect 200 - 300 cycles with consistent power!


That is a very good price for a GensAce battery. I could not see anything wrong with that purchase...

 

Welcome to heligods policetac.

You will find this forum is very relaxed

 

Yep, Welcome, enjoy the ride like a particle through the CERN accelerator
Simon

 

Thank you everyone! Glad to be here, glad you were here!

Well, I went ahead and ordered that GensAce. Can't wait 'til it get's here!

Until then, I pulled out my trusted multi-meter and proceeded to Frankenstein myself an emergency charger I could use on the old battery pack it came with. Only problem is that there's really no way I'm aware of to know exactly when your battery is starting to "overcharge." About all I can think of to do is watch my heat and try to figure out where "full" is using my voltage meter (around 8.0v - 8.02v?) and disconnect it when I reach that target voltage. Knowing that the first time I guess wrong I lose a good 20% or more.

Of course on the other hand, I also came to the realization that rechargeable batteries are everywhere!
I have a feeling I'm going to be very much on the lookout for them on the weekends when garage sailing the area. lol

Okay. Well, thanks again. I'm going to sign off for now, but I'll keep checking in to keep my interest's peaked!

Hope to chat with you all again soon.

policetac

 

Hi @policetac ... Regarding charging of Lipo batteries, please read the following, i copied the text for your information and safety. I have only ever used a proper lipo charger so i cant really comment on using a home made version... Hope you find this useful...


Lithium cells must be charged very differently than NiCad or NiMH. They require a special charger specifically designed to charge lithium cells. In general any charger that can charge lithium ion can charge lithium polymer, assuming that the cell count is correct. You must NEVER charge lithium cells with a NiCad or NiMH only battery charger. This is dangerous. Charging cells is the most hazardous part of using lithium batteries. EXTREME care must be taken when charging them. It is important to set your charger to the correct voltage or cell count. Failure to do this can cause the battery to spew violent flames. There have been many fires directly caused by lithium batteries. PLEASE BE RESPONSIBLE when charging lithium batteries.

Here are a few MANDATORY guidelines for charging/using LiPos (Lithium Polymer Batteries).

1. Use only a charger approved for lithium batteries. The charger may be designed for Li-Ion or Li-Poly. Both batteries are charged in exactly the same. Some older cell phone chargers may charge the batteries .1 volt to low (4.1 vs 4.2), but that will not harm the battery. However, inexpensive lithium chargers are widely available and the use of cellphone chargers is highly discouraged.
2. Make certain that the correct cell count is set on your charger. Watch the charger very closely for the first few minutes to ensure that the correct cell count continues to be displayed. If you don't know how to do that, get a charger that you do know how or don't charge the batteries.
3. NEVER charge the batteries unattended. This is the number one reason for houses and cars being burned to a crisp by lithium fires.
4. Use a safe surface to charge your batteries on so that if they burst into flame no damage will occur. Vented fire safes, pyrex dishes with sand in the bottom, fireplaces, plant pots, are all good options.
5. DO NOT CHARGE AT MORE THAN 1C unless specifically authorized by the pack vendor. I have personally had a fire in my home because of violating this rule. Todays highest discharge batteries can supposedly be safely charged at greater than 1C, however so far in all cases doing so shortens the life of the pack. Better to buy 3 packs than to try to charge 1 pack 3 times quickly. This may change in the future but as of Winter 2005 1C is still the recommended charge rate.
6. DO NOT puncture the cell, ever. If a cell balloons quickly place it in a fire safe place, especially if you were charging it when it ballooned. After you have let the cell sit in the fire safe place for at least 2 hours. Discharge the cell/pack slowly. This can be done by wiring a flashlight bulb of appropriate voltage (higher is voltage is ok, lower voltage is no) up to your batteries connector type and attaching the bulb to the battery. Wait until the light is completely off, then throw the battery away.
7. If you crash with your lithium cells they may be damaged such that they are shorted inside. The cells may look just fine. If you crash in ANY way carefully remove the battery pack from the aircraft and watch it carefully for at least the next 20 min. Several fires have been caused by damaged cells being thrown in the car and then the cells catch fire later and destroys the car completely.
8. Charge your batteries in a open ventilated area. If a battery does rupture or explode hazardous fumes and material will spew from the battery.

Now that we have covered that important topic let's move on to lighter matters:

2. Lithium What?Lithium Polymer batteries are used in many electronic devices. Cell Phone, Laptops, PDA's, Hearing Aids just to name a few. Most, if not all, lithium polymer batteries are not designed for RC use, we use them in different applications than they were designed for. They are similar to Lithium Ion batteries in that they each have a nominal voltage of 3.6 volts, but dissimilar in that they do not have a hard metal casing but rather a flexible material encloses the chemicals inside. The "normal" lithium polymer batteries are thin rectangle shapes with two tabs on the top one positive one negative. The reason we use Lithium cells is that they are significantly lighter than comparable NiCad or NiMH batteries, which makes our planes fly longer and better.

3. Voltage and Cell Count: LiPolys act differently than NiCad or NiMH batteries do when charging and discharging. Lithium batteries are fully charged when each cell has a voltage of 4.2 volts. They are fully discharged when each cell has a voltage of 3.0 volts. It is important not to exceed both the high voltage of 4.2 volts and the low voltage of 3.0 volts. Exceeding these limits can harm the battery.
The way to ensure that you do not go below 3.0 volts while flying is to set the low voltage cutoff (LVC) of your electronic speed control (ESC). It important to use a programmable ESC since the correct voltage cutoff is critical to the life of your batteries. Use the ESC's programming mode to set the LVC to 3.0 volts per cell with a hard cutoff, or 3.3 volts per cell with a soft cutoff. If your ESC does not have hard or soft cutoff, use 3.0 volts per cell. You will know when flying that it is time to land when you experience a sudden drop in power caused by the LVC.
If your ESC has an automatic lithium mode. Use it, it will correctly sense the number of cells and set the auto cutoff appropriately.
If you have previously been flying with NiCad or NiMH batteries, switching over to lithium polymer will result in a different number of cells being used. If you had 6 to 7 round cells then 2 lithium polymer cells will correctly duplicate the voltage of those cells. If you had 10-11 cells then 3 lithium polymer cells would be right for you. There are a lot of 8 cell flyer's out there that are stuck between 2 and 3 cells. In my experience the best option is to determine how many watts you were using before and duplicate that with your LiPos, Motor, and Prop. For example. If you were running 8 cells (9.6volts) at 10 amps on a speed 400 airplane, then you have 9.6 x10, 96 watts. So if you went with 2 lithium polymer cells (7.2 volts nominal) then you'd need to change your prop such that you used 13 amps. If you went to 3 LiPoly's (10.8 volts nominal) then you'd need to reduce the amperage to 8.9 amps. These estimates are approximate, and some experimentation is required for best results but conserving Watts is a good way to start.

4.10C from 3S4P? Naming conventions explained.

How fast a battery can discharge is it's maximum current capacity. Current is generally rated in C's for the battery. C is how long it takes to discharge the battery in fractions of an hour. For instance 1 C discharges the battery in 1/1 hours or 1 hour. 2 C discharges the battery in ½ or half an hour. All RC batteries are rated in milli Amp hours. If a battery is rated at 2000 mAh and you discharge it at 2000mA (or 2 amps, 1 amp = 1000mA) it will be completely discharged in one hour. The C rating of the battery is thus based on its capacity. A 2000mAh cell discharged a 2 amps is being discharged at 1C (2000mA x 1), a 2000mAh cell discharged at 6 amps is being discharged at 3C( 2000mA x 3).
All batteries have limitations on how fast they can discharge. Because of this many LiPoly batteries are put in parallel to increase the current capacity of the battery pack. When 2 batteries are wired positive to positive and negative to negative they become like one battery with double the capacity. If you have 2 2000mAh cells and you wire them in parallel then the result is the same as 1 4000mAh cell. This 4000mAh cell has the same C rating as the original 2000mAh cells did. Thus if the 2000mAh cells could discharge at a maximum of 5C, or 10 amps then the new 4000mAh cell can also discharge at 5C or (4000mA x 5) 20 amps. This method of battery pack building allows us to use LiPoly batteries at higher currents than single cells could produce.
The naming convention that allows you to decipher how many cells are in parallel and how many are in series is the XSXP method. The number in front of the S represents the number of series cells in the pack so 3S means it's a 3 cell pack. The number in front of P means the number of cells in parallel. So a 3S4P pack of 2100mAh cells has a total of 12 cells inside. It will have the voltage of any other 3S pack since the number of cells in series determines the voltage. It will have the current handling of 4 times the maximum C rating of the 12 individual cells. So say our 3S4P pack had a maximum discharge of 6C. That means that it has a nominal voltage of 10.8 volts (3x3.6) and a maximum discharge rate of 50.4 amps (2100mAh x 6Cx4P ).

5. Dealing with temperature.
Lithium batteries like heat, but not too much. In the winter time, try to keep your batteries from the cold as much as possible. Leave them in the car while your flying, or keep them in your cargo pants... etc. At the same time don't let them heat up too much. Try to keep your batteries from reaching 160F after use. This will prolong the life of the cells. A good way to measure temperature is a handheld IR meter, they can be found for around $50.00 at most hobby shops.

 

I'd give it a + if I could be fracked reading it!
Simon

 

Over one paragraph and I'm smoked
Simon

 

Yeah i know. I could have summarized it in to 3 words... "dont do it" .... lol. But when you start out you need more information. There is so much to rc helicopters...

 

Really, if you are new to lipos, read @smakmeharder 's post - I will burn....
Simon

 

Basically it's two cell...ain't going to balance and is going to bad... so don't... else you may do a lot more damage...