propjobbill

How long can I expect the flight time to be with a 250mh battery. Using 2 of the small 9 gram servos? I understand that there are many variables. But on average would you say 30, 45, 60, 75, or 90 minutes. I am new to these small 1/2A planes with the new miniature gear.

Thanks in advance

flyinrog

My Feedback: (1)

Hard to say pjb, I have read where guys have sat on the couch and wiggle the servos at home for 45 minutes with no drain on the battery, of course theres no load in your living room either...I have one plane that eats power to the point I dont want to fly it more than 2, 10 minute flights, however I am beginning to get a little suspect about the accuracy of a "voltwatch" I have one on every plane....I've seen many 2 channel 1/2a reedy racers do 10, 3 minute flights on smaller paks and watched Bobhh thermal a .020 plane for about 20 minutes once...so as long as every thing works with no binding, I would think the 45-60 minute mark would be ok, but I probably wouldnt go that long myself....there are alot of factors to check out....Rog

eroc144

My Feedback: (1)

I tested a few of my 270 mah NiCDs a few years ago using Tower's Expanded scale voltmeter, and found that after four 10 minute flights the battery voltage was still in the "safe" zone and could have taken another 2 flights. I think the total voltage drop was from 5.7 to 5.4 volts on a 4.8 V system. Of course there are a lot of factors that affect this - the age and state of your batteries, servo wattage, total circuit resistance (wire length, # of devices, etc).

EG

vicman

My Feedback: (10)

I have seen others do things with small batteries I can only dream of. Whenever I have tried it doesn't yeild near as favorable results. Anymore I just use 730mah nimh and fly without worry.

Yuu

I would charge MY batteries, then hook the Radio Shack lamp [4.8volts @ 400 mAh...or whatever] and watch my volt meter go down to 1.1 volts per cell. Say, 45 minutes @ 400 mAh pack... do the math, that's roughly 300 mAh in the battery pack. That's 75% of the original capacity... time to junk them, or put them in the kid's toy car. Another example: Using new [or my existing] batteries, I would charge them and put them in the fuse, and tie the fuse to a stool with a big 19" window fan blowing into the prop... simulated loads on the servos. Then sit on the couch with a watch and a volt meter, and "fly" the plane into the wind and look for the batteries to go down to 1.1 volt per cell [4.4 on the ESVM]. Stop. Using THAT length of time, do the math backwards...say it took one hour to use up your 350 mAh pack... NOW you have an answer to how much 'juice' YOUR rig uses....each servo, each Rx, each 'drag' on the ny-rod or the hinge or the clevis on YOUR plane uses This much juice in This much time. Excellent information! Say in an hour you use 350 mAh... be safe and figure 75% of that hour is "safe", so you can fly 45 minutes 'safely'. Of course, if a cell dies during the year, all bets are off! Check your batteries before EACH flight, and if there's a big difference from the usual reading, DO NOT FLY. Check it out first. I've had a cell go bad in a three month old pack..... and I've had a weld come loose on the 'store-bought' Rx pack. Remember that in the year, the pack will loose some of its capacity, so next year that same pack might only have the capacity of 320 mAh... if you're flying the same plane and Rx and servos, 75% of 320 mAh capacity leaves 240 mAh, 91% of the original capacity. 45 minutes times 0.91 leaves you only 41 minutes to fly safely now.

ptulmer

My Feedback: (5)

Using Hitec 270mah Nicds, I frequently make five or six flights of ten plus minutes each and at the end of the day it will still show a good charge on a loaded tester. You can bring two planes and go home tired and sunburnt. (even in the winter here!)

somegeek

My Feedback: (2)

The Hobbico HydriMax 4-Cell 4.8V 750mAh NiMH is another option in the <2oz pack range(1.9oz).

somegeek

Remby

My Feedback: (3)

I would suggest using (4) 400mha ,2/3 AAA bats. I find you can build the pack, and with everything included, (wire, switch, connectors and charge jack), it is ready to fly at 1.9oz with bats.

Cox has some packs like this on sale at the site, or try Cheapbatterypacks.com for the loose cells, around 1$ each, if you can build your own.

270 is pretty small, although many look to use that from what I read here.

somegeek

My Feedback: (2)

Excellent suggestion -

$1.25 / 400mah NiMH cells at .27oz each
$.30 for a foot of shrink

Provide your own leads.

Cheap ~1.2oz 400mAh pack

somegeek

flyswatter

pjb:

I get at, a minimum, 4 flights (about 45 min) on a 270mah bat. My advice is to measure your battery after each flight with a esvm to verify YOUR battery performance. The problem with buying bigger batteries is that you have to lug around the weight. For 1/4 A planes, I take a 9.6 - 300mah NiMH and split it to get two 4.8v packs. Great performance - minimum of 4 flights on a charge and the weight is about 1 oz per pack.

AMB

Just weighed my 700mil triple A 4 cell NiMih 1.9 oz leads and all martin

Remby

My Feedback: (3)

dieseldan,
Thats good and light for that size of bats, I use two like that, but are a good bit more weight than that.

Another factor in flight time is temp;, cold eats the battery's reserve fast. Should keep that in mind this time of year with small battery packs.

Nikola Sljivic

My source for 1/2a rx battery is 9v nimh battery block (usually 150-250 mAh consists of 7 cells).

Of two 9v blocs you get 3 rx pacs (two 6v one 4.8v) ,6v pac weights less than an 1oz (23grams!)

With that 250mah battery I made usually four to six 15min+ fligts and battery needs lot of discarge at home. (i asume that 100-120mah are used in fligts).

(the plane has four 9gr servos, rtf weight 12.3oz 22sqinches)

But I wouldnt put less than 600mah in my 2m sailplane (using only two servos same type as above)

More weight, more inertia, more stres on control surfaces and servos, less weight...

vicman

My Feedback: (10)

Yeah, I'm in the same boat as Nikola.
All my stuff is so fast they need a bunch of extra power to move the control surfaces and wipe the battery out too quick.[8D]