capacity after flying

[PatMc]

If you set the timer to be triggered by a low throttle position (say 1/4) then you won't have to remember. Set it to countdown for however long you think is OK for the battery capacity. I think in the T7CP it can be arranged only to run the timer when the throttle is above the trigger point, which means it's only timing when the actual motor is on & not including the glide.

You can determine the time by trial & error, I suggest starting with 5 minutes countdown then check the battery & increase or reduce the time according to what you measure.

I'd set the LVC to 3.4v/cell the actual terminal voltage will be higher when the load is removed.

Edited By PatMc on 23/02/2014 13:36:33

[Rob43]

Hi Dan
You could set your lvc to a higher value but the point I make about using the alarm is that it will go off well before yoh reach the lvc on the esc. I can make 3 approaches under power after the alarm goes off before the lvc cuts the power to the motor whereas if you just set the lvc higher and rely on that you will not have use of the motor to bring your model back on a controlled approach.

[Frank Skilbeck]

You could fit one of these and get an alarm when you've run the battery down to a preset number of mah. Of fit one of the low voltage alarms you can get from HK they are pretty loud

Edited By Frank Skilbeck on 23/02/2014 13:41:17

[Rob43]

Hi frank

I recently bought one of the wireless copilots you mention in your post above and use it now alonside the lv alarm. The copilot works very well, exellent product I think but I like the security of the low voltage alarm as capacity can vary due to many factors and ultimately the low voltage situation is what will determine if you have to land. I admit to using the copilot just as much for the altitude measurments.

[John Privett]

Posted by PatMc on 23/02/2014 13:31:50:

I think in the T7CP it can be arranged only to run the timer when the throttle is above the trigger point, which means it's only timing when the actual motor is on & not including the glide.

Yep - the T7CP (35MHz) and T7C (2.4GHz) let you do this - as I have done.

On the timer setup screen, setup the starting time, and mode (I use Down so it counts down to 0:00) then for "SW" select 3^. Put the throttle stick to the position you want it to switch on at (probably a little bit up from closed) then press and hold the rotary dial to select that point.

That's the setup done, and now for the model it's setup on, the timer will start at the start value when the tx is switched on then start counting when the throttle is opened, and stop counting whilst the throttle is shut.

[PatMc]

Hi John,
I have a couple of E-gliders set up using two timers of a MPX Cockpit SX. Both timers triggered by 25% throttle, #1 is on 30 sec countdown for the climb from launch, #2 is 4 minute countdown to keep the accumulated power runs within the battery capacity. I re-set #1 between launches & keep a record of flight times via a HK altimeter.

[dan c 1]

HI all-
After flying earlier today in wind again! , I have put my two batteries back on charge after 18 & 20 minutes flight times.
The first one was at 11.19v and 3.77,3.77,3.77 per cell and 1857 was pushed back in.
The second was at 10.50 3.59,3.59 & oddly 3.46 but it came back up level within 5 minutes of charging and topped out at 4.20,4.20,4.20. 2158 was pushed back in.
Any thoughts ?

Edited By dan c 1 on 25/02/2014 19:51:27

[John Privett]

I'd say the first is about what I usually end up with - putting around 1800mAh back into a 2200mAh battery. Sometimes I put a little more back, often a bit less.

However, putting 2158 back into a 2200 is way too much - you let the second one get too low - in my opinion. What do others reckon?

[Martin Harris - Moderator]

Apart from not pushing it as far as you did with the second one?

3.77v is about as far as I'd want to go - and I have little or no respect for the finer points of LiPo care!

Edit - looks like we're pretty much in agreement John!

Edited By Martin Harris on 25/02/2014 20:11:31

[dan c 1]

Thanks guys. Yes thats what I was thinking on the first. However 2158 into the 2200 seams odd as that doesnt sound like there is anything left yet it was still flying about ok??? Well, Ill trim the time down to about 17 minutes or so next time. Does that sound ok for a beginner and Bixler2!

[PatMc]

Posted by John Privett on 25/02/2014 20:09:09:

However, putting 2158 back into a 2200 is way too much - you let the second one get too low - in my opinion. What do others reckon?

TBH, I'd be quite relaxed to consider at the second battery voltages quoted, if they're accurate, though I wouldn't want to go lower. What goes in is probably significantly more than what's been taken out.

However I'd use the timer counting down the motor run time on rather than the overall the flight time to assess what's safe.

[Martin Harris - Moderator]

Dan - the capacities are nominal and you often get a little extra for your money. I'd be more concerned with the largish difference than the absolute values - as Pat infers, not all chargers measure voltages accurately. I'd imagine that the last cell was getting very close to the rapid drop off in voltage which comes at the end of the discharge curve - an indication that I certainly wouldn't ignore!

[dan c 1]

Ok well Ill try another outing as see what happens. They are two new batteries only used 9 times each. The wind was bad today so the motor was running most of the time. I guess it sups the power

[Martin Harris - Moderator]

It's quite true that you use more power in a wind. Some people assume that it's swings and roundabouts - the tailwind cancelling the headwind but it isn't so. Taken to an extreme, if the wind speed is 1 mph less than the flat out speed then you'll need to be at full throttle for almost the entire flight just to make excruciatingly slow progress into wind whereas in light wind conditions you will (should) spend most of a training flight at part throttle both into and down wind.