txaggie08

Joining the 21st century and converting to LI-po as my receiver pack in this tiger 60.


What I'm concerned with is a lack of airflow over the pack, and the CC BEC I'm using to regulate voltage and power the servos. How big of a concern is this as I'm not discharging the pack heavily? what about the BEC, There will be little to no airflow in the fuse where I planned to mount it....




Thanks alot, beginner forum is still the easiest place to get good answers on this forum.

tIANci

I converted a few GP planes to EP and did not really bother to work on airflow as the current draw was not high, it worked fine. What is high or low is relative. Let's say you have a 60A ESC that is operating around 30A most of the times then there would be no issue. As for your packs I will say that if you are discharging them at a 8C then usually it will not heat up much. In any event its not hard to get air flow over the ESC, just mount it in front of the firewall, there will always be space there as your motor will be extended to clear the cowl/cowl cheeks. For the batt you can always make simple air scoops using spoons etc.

w8ye

My Feedback: (16)

If in doubt - Vent it

txaggie08

tianci- there's no ESC, the plane is staying glow, the servos will be run of li-po batts however, using a BEC as a voltage regulator and low-voltage shutdown.

w8- I'll look into the easiest way to do that.

The Ghost

Won't need the airflow, The reg's don't even get hot only just warm. the RX and servos don't draw the current that motor BEC's see. You will be lucky if you draw 0.5C of the battery pack.

Cheers

tIANci

My bad!!! From what I seen and used regulators don't get hot ...

CGRetired

My Feedback: (1)

Just remember one thing. All this conversion to LiPo receiver packs with voltage regulators is cool and very "trendy", but adds a new point of failure into the picture.

Many RC'ers of the old school will tell you that "simple is best", meaning a proper battery pack to do the job with one switch. If you do parallel battery packs, well, that's two batteries with two switches. (I've added Voltwatch to the equation, but that is not in the battery/switch path, but parallel to it)

No matter what some others might say, most of the pattern folks that I know are still using NiCd packs, as small as they can get them, to reduce weight, and yes, they are concerned with even the smallest increase in weight. And most of them will tell you that keeping it simple is the best thing, and introducing another point of failure has to be weighed against the benefits that this will provide. And, most will tell you, keep it simple.

If you fly a lot, then you really ought to be monitoring your battery pack by looking closely at it before your first flight, then upon landing, then again before and after the next flight of the day. If you do, you don't need to get to sophisticated with your setup... meaning, keeping it simple, of course.

Perhaps I don't quite understand the reasoning behind using LiPo packs on glow powered receiver packs.

pdm52956

My Feedback: (1)

I don't know, I use a 7.4, 1350 mah lipo for my rx along with a 5.6 voltage regulator. I switched from a 4.8, 1600 mah pack. I found that I get much more consistant voltage drop over a much longer period of time giving me more flights before recharging. I still have one switch, which is what gave up on me and caused my last plane to go in beyond repair.

I have not checked the overall weight difference, but I suspect that it would come in lighter with the lipo/regulator combination.

Works for me anyway.

CGRetired

My Feedback: (1)

pdm52956

Yeah, I understand, and believe that most people will do what they think is good for them. But, I've talked to a few and it seems that the paranoia about "less is best" seems to have prevailed with me. But, if it works, what can I say.. I like the standard NiMH or NiCd packs (I use 6 volt packs) and one switch per battery pack with one voltwatch in a vacant channel, and this works well for me.

I get my share of flying in. I usually get in about 5 or may be 6 flights when I go out and fly, a lot of the time is just spent shooting the breeze with other pilots.. ha.. so we often get in more talking in than flying.

Later..

CGr

pdm52956

My Feedback: (1)

Yupper............last I checked, I got 5 to 6 flights per trip to the field, 5 to 6 hours talking each trip to the field, almost 2 weeks before recharging the battery on the rx............

I like simple too. I probably would have been better off if I had used a 6 volt rx pack in the plane that went in, but it's neither here nor there because it was the switch that failed. I guess the biggest problem, at least in my case, wasn't so much with the battery but with the switch. I hear alot about problems with the DX6i and glitches. I haven't had that issue, but I would have sworn to you that it was that tx that caused the first plane to nose in. Next thought was that the battery had depleted itself. Nope, it was the simple switch. I don't know, my setup works for me but that's not to say that when the next one ends up burried to the wing in the asphault runway, that it wouldn't be something else I didn't expect. It's the nature of my beast.

It's all good.

CGRetired

My Feedback: (1)

I am using the Spektrum DX7 system. I bought mine back when it first came out, and have about 6 receivers now, converted many of my RC aircraft, mostly glow, over to the 2.4 system. My old, still functional radio is an Airtronics RD8000, channel 11.

I switched over to 6 volt packs even before I started out with the DX7, though. I got more speed out of the servos and, of course, more torque.. not that I really needed it, but that was a benefit of the change. Then, when I went over to the DX7, and with that reveiver re-boot issue due to low voltage 4.8 packs (discharged to the point of reboot threshold), well, I was glad to have the 6 volt packs.

But, I never experienced a switch going bad on me. I did, however, have one of two batteries go sour on me in my Venus II pattern plane. I was glad I was running the pair of 6 volt packs in parallel AND that I had Voltwatch on board. The packs were set up with two switches into two separate slots on the RX with the voltwatch on a Y connector to one of the RX battery slots. After the forth or fifth flight (not sure now, that was last year some time), I did my normal battery check after each flight (got to be a habit that I am glad I developed). I simply shut battery 1 off, looked at the voltwatch, it was ok, then turned on battery 2, shut off battery 1, and looked at the voltwatch. It was in the RED. So, I checked it again. Then took the wing off and checked each pack with a voltmeter mainly cuz I couldn't believe what I was seeing... battery 2 was bad. Checked it with someone else's voltmeter because I STILL couldn't believe what I was seeing.. sure enough, battery #2 was bad.

Wphew..

I had a spare so I installed it and put both batteries on the field charger, and, while they were charging, took a close look at the failed pack and didn't see anything in particular. One of the fellow RC'ers was there talking to me and he said he could take it home and check it out for me. He said that he took it apart, and checked each individual cell.. one was bad, or low, the others were ok. He put it back together and cycled it a couple of times and said it was ok. But, I told him he could keep it if he wanted it, but I would not recommend that he use it in one of his planes, which he has not done.

So, things happen, I guess, and no matter what the battery pack is, if you have a problem, well, you have a problem and there isn't much to do about it but hope it does not crash the airplane, as, unfortunately, it did for you.

Best of luck in 2009, enjoy RC, and have a safe, healthy, prosperous and happy 2009!!

CGr

CGRetired

My Feedback: (1)

Sorry, back to the original subject. I converted a glow to electric last year. I know, this is not about that sort of conversion, but the conversion did not actually provide for air circulation because the plane had a firewall for mounting a glow engine.

I cut four holes in the firewall so as to provide a route for the air to pass into the fuselage. Then I removed a length of the covering on the bottom of the fuselage aft of the wing on the bottom of the plane. I put some 1/16 balsa where the hole was between the formers, then carefully cut two larger holes in the balsa to provide an exit route for the air passage. I recovered the fuselage and of course, cut out the covering where I had made the air-flow holes. This proved to be adequate for cooling circulation.

If you want, you can do something like that, to provide some circulation within. There will be some minor heat generated by the regulator, perhaps not to worry about, but some heat will be generated. If you feel comfortable with that then don't sweat the holes. If you do not feel comfortable with the heat, then go ahead and make some path for circulation. Make the exit holes larger than the inlet holes.

CGr.

The Ghost

I agree, in 40 or 60 sized aircraft wit 4 or 5 standard servos you don't need the Lipo conversion as the standard flight pack will give you aprox 10 - 15 flights with out a problem. The reason that I use a Lipo pack and a reg is because I have replaced the RX pack(5cell 3300 nimh) and onboard glow battery(3 cell 3300 nimh) total weight 468 grams, 2cell 2500mah, reg, for rx and 2cell 4400mah pack for the onboard glow total weight 243 grams. This is in a Christen Eagle Running 7 digital, a mini throtal and choke servos. I done this because the RX pack failed a load test and I found a dead cell, and to replace it was going to cost 3 time the cost of the full Lipo setup.

Cheers

CGRetired

My Feedback: (1)

Ghost: This is a gasser, not a glow, right? With all that load, I don't doubt that you require the LiPo with the regulator. And, besides that, arn't the digital servo's a tad more sensitive to 'over voltage'?

CGr

The Ghost

No its a glow, Magumn 160FS twin, I have the voltage reg set to 5Vcc. The reason that I went with the Lipo's is that it was about 1/4 the cost of replacing the NiMh and also the weight saving. I don't know if people have noticed or not but the cost of NiMh cells and batteries are going up as the cost of Lipo's are coming down.

Cheers

txaggie08

I find the value in the fact that the battery last A LOT longer, in lifespan and duration of useful charge, and they don't weigh anymore.

The regulator is an extra step to fail, but the castle creations BEC i'm using weighs next to nothing(the whole rig wwighs less than a standard pack), and is very dependable. I'll trade a remote chance of failure for a more efficient and longer lasting battery pack.

jrcaster

Thing that are bad about the lithiums are that

1. The current output drops when they are cold. In warmer weather they run great but as the temperature drops, like in snowy weather and colder they may not have the current to drive the servo's.

2. As said before, they can be dangerous. You would need to remove the pack from the plane to recharge them. In the fuselage you would probably have the pack wrapped in foam to protect it from vibration. In this configuration charging would allow the pack to heat up quickly.

Before you make your final decision about lithiums, do a search on here and watch the videos of the packs bursting.

CGRetired

My Feedback: (1)

txaggie08: Well, that makes perfect sense, however, I have full trust in my dual battery pack setup and it is simple and reliable. Most Pattern folks, who fly a heck of a lot more than I do, have simple battery setups in their aircraft and have had very little problems with it. It is very rare indeed when I hear of a pattern plane crashing because of a failed battery pack. That's because an awful lot of them go to dual parallel packs and check them like I do, before and after every flight. And, don't have to remove their packs from the airframe to recharge.

CGr.

txaggie08

I've blown a lithium pack up before....I already have a hatch built for easy removal!(my entire canopy is removable....). However, even checking them often I shouldn't have to remove them at the field TO charge them unless I fly 10+ times...

Lithium doesn't bother me as I've been using them for 3 or 4 years in diff applications. I already have all the charging equipment here, I simply purchased a new pack and BEC. This is actually about my fourth plane, I've also had heli's and cars that ran on them. I like asking question questions here because you get realistic answers quickly


Might add, I live in SEtexas, it snowed here for the first time in 20yrs last week.....temperature on the sub freezing level is not an issue.

jrcaster

You may want to peruse the giant scale forums to see how they set up their systems. They are the only ones I can think of that use the lithium cells regularly other than going totally electric.