Need a Lesson on LiPos

[kent83]

I have two Esky batteries (ESky 1800mah 3S 11.1V 15C and 20C) and have been making do with two Esky chargers (one from my Lama IV). I've been reading enough posts on batteries and chargers to make my head spin. I usually just fly until I feel the power start to drop. In reading about the 80 percent rule, people obviously monitor their batteries and voltage levels very closely, and I have often read to NEVER EVER fly more than 80% -- something I am incapable of monitoring with my setup. I take it that I need to invest in SOMETHING to manage my LiPos better (is that true -- is what I'm doing unsafe or will I just shorten the battery life?), but I really don't want to (and can't) spend more on a charger than I did on the heli, and I'm not interested in buying more batteries at this point. So, I've been looking at products ranging from a cheap digital battery monitor (http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=6589&Product_Name=Battery_Monitor_2-6S)
to an LED battery monitor (http://www.highvoltage-rc.com/index1.html) to getting a new charger (A CellPRO 4s stretching on the higher end of my budget and the Turnigy Accucell-6 on the lower end -- will non-Esky chargers fit the plugs on my Esky batteries?!). But, I've also read posts that say using a timer is the ONLY way to go.... So, I'm looking for a cost effective solution that will allow me to manage my batteries and flight times a bit better. Installing monitors, timers, and adjusting the settings on a charger so the batteries don't blow up all make me just a little nervous. Keep in mind soldering a Dean's connector to my second battery was a big accomplishment for me, so I'm still on the steep side of the learning curve, but I'm willing to try ...

[Real_Sparky]

Kent
The only way to monitor the 80% rule is to get a charger that will tell you how many milliamps go back into the pack when charging. I thought the same as you, and would stop flying when the power dropped a little, but it doesnt work. I have 2 puffed pack's to prove it. I found the best way to acheive this is to time your flights and monitor what goes back into the pack.

I found that a 7 minute flight in idle up with a 100 75 100 throttle curve takes somewhere between 1200-1300mah out of the pack. This is true for my heli but may not be the case for yours so dont take this as gospel.

Esky batteries use jst balance leads and most chargers will fit. If they dont you can buy adapter leads. As for blowing up batteries, if you dont charge at more than 1c (which in your case is1.8amps, 1800mah divded by 1000) you should not have to many issues.

In my opinion the most cost effective way to manage batteries is to buy a decent charger and use a timer. With the esky charger you are probably used to 3-4 hour charge times. With a decent charger, and it doesnt have to be the best money can buy, you will charge batteries in a hour. This allows more flying. I am using a Kong Power charger and a Imax b5. I recommend either they both do what they are supposed to.

Once you know what you are taking out of the pack you will know how long you can fly for. I have been told that you should leave some headroom and not discharge all the way to 80% but around 60-70% this will help your packs, and they will give you a long life for it.

Hope this helps.


Darin

[kianhon]

The Esky stock charger is good enough for your lama Lipo. But is almost a must to spend money on a decent charger when you get into 400 size or above heli's Lipo. The Turnigy Charger you are getting is a good one for the price, I'm using one too. LED battery monitor is not necessary, just get a battery monitor. Since you are not planning to get more Lipo then you should take good care of the one you having.

What Sparky said is true about reading the miliamp going back into the pack while charging, but that is too technical for me, I'm a very simple person:YeaBaby:. To take good care of your Lipo is very simple:

1st, Get the TurnigyCharger and the battery monitor. Unless you have a power supply, otherwise get the IMAX AC adapter from Hobbycity for your turnigy charger, only cost like $16.

2nd, When your charger arrive, charge your Lipo at 1c (eg. 1800mah charge at 1.8a, 2200mah charge at 2.2a). After charging (it takes around 1 hr), use your battery monitor and you will see each cell will have around 4.2v+-.

3rd, Let's just assume you are just doing hovering. My 2200mah 20c can give me 7+- minutes of flight before I use more then 80% of the Lipo pack. Time yourself, first fly it for 5mins, then use your battery monitor to see the voltage for each cell, and if it is still above 3.75c per cell, then fly it another minute. Do until you read each cell have 3.75v+- then stop and recall how many minutes you have been flying and stick to that from then onwards. 3.70-3.75v for each cell is around 80% usage.

Never charge your Lipo right after each flight, let it cool down for like 15 minutes or so.

Wahhh laaaa, you just completed one of the the simplest steps to take good care of your Lipo.

Hope this helps you, I hope my way is right or someone will jump out and put me down:bomb:

[kent83]

Thanks Darin and Kainhon. Looks like no way around buying a better charger and your specific numbers and recommendations are very, very helpful. Thanks!

[psilo]

For monitoring battery in flight I use the HRPoly-X (http://customidea.com/shop/product_info.php?products_id=102) device. It fits in line and prewarns (audible and visual warning) when your battery drops below a user defined amount. You can also then download from the device to your PC to view the discharge curves.

[Real_Sparky]

You find the best stuff Gerd.........You should open a shop:YeaBaby:



Darin

[Darthdrk]

I usually fly my helis until I notice a power drop. You can basically tell when it starts to require more collective to keep in in the air. You can also land and let the heli sit a few seconds and take back off ( Do not fly like that you are sure to fly your batteries into the zone of no return) battery health is going to also depend on how smooth you gear mesh and how tight your belt is. Put to much a strain on your batteries if things are to tight, youre going to run into your batteries having a short life because the tighter things are the more amps and the more amps, the more heat. Its good to go with the higher C rated batteries such as the 20C. I myself do not have a very highly sofisticated Battery charger but it does tell me voltages and I can set charge rate. It automatically shuts off when battery is fully charged and it will shut off if it detects something is wrong. The rule im familiar with is never fly (Discharge) your batteries past 3 volts per cell on the Lipos. So, if you have a 3 cell pack you shouldnt let the voltage drop below 9 volts. (use a balance charger often to keep cells balanced) When my helis are finished after a flight, I put batteries on charger and they always read above 11 volts. There is no way any of my helis will keep flying anything lower than this except I sit them down and let the battery sit a few seconds and then hit the throttle, I may be able to punch a few more 10 second flights. if I keep doing this but it will destroy my batteries. Ive read so many times where some new person has done this and had went on a tyraid about having crappy batteries because they would not charge up. A good rule of thumb that works for me is when it takes me 3/4 throttle to stay airborne, its about time to recharge. Alot in post #3 is what I adhere to and advise especially referencing the charging of the battery(ies)