when to stop flying??

[Hughes500Bob]

http://www.espritmodel.com/index.asp?PageAction=VIEWPROD&ProdID=5740 Here is a link to the one I am currently installing on my new Trex 450 V2. There are many others .... and you can even build your own as schematics and parts lists are readily available if you search for Li-Po Alarms. You can build your own for around $10 if you want.

AND .... I charge my Li-Po bats in a Li-Po charge sack .... so I won't burn down the house.

If you are going to fly E-Helis you should consider a quality charger, balancer, and L.E.D. or screamer Li-Po alarms. Cut-off circuits are mostly for plankers.

[FearNot]

http://www.espritmodel.com/index.asp?PageAction=VIEWPROD&ProdID=5740 Here is a link to the one I am currently installing on my new Trex 450 V2. There are many others .... and you can even build your own as schematics and parts lists are readily available if you search for Li-Po Alarms. You can build your own for around $10 if you want.

AND .... I charge my Li-Po bats in a Li-Po charge sack .... so I won't burn down the house.

If you are going to fly E-Helis you should consider a quality charger, balancer, and L.E.D. or screamer Li-Po alarms. Cut-off circuits are mostly for plankers.


Thats the one I have ... it is close to impossible to see the LED in sunlight ... ona cloudy day or when the sun goes down its great ... You will also NOT be able to hear the alarm ...

Its from british company and they make an extra LED cluster for it:

http://customidea.com/shop/product_info.php?cPath=33&products_id=104


In regards to the Lipo sac .. do we know if they actually help? What will happen if a Lipo goes up vs Lipo goes up IN the sac?

Matt

[PsychoPilot145]

More importantly look at the 1010 when you are done to see how many amps you put back into the pack and adjust flying times to shoot for 80% capacity.

Now this is what I am looking for. If I have a 4600mah LiPo, if I burn off 80% of the mah, I should want up to 3680mah going back in. Is this correct, or do I have it backwards?

Thanks!

[Tomas Ahl]

Now this is what I am looking for. If I have a 4600mah LiPo, if I burn off 80% of the mah, I should want up to 3680mah going back in. Is this correct, or do I have it backwards?
You are quite right.

And earlier you said that you tend to put back 2200 to 2500 mAh after a flight. I interpreted your statement to mean "a five minute flight". If my interpretation is correct that means that your heli is consuming 500 mAh per minute (2500 / 5, I took the safest figure - highest consumption) so you should be able to fly approximately 3680 / 500 ~ 7.36 min (decimal minutes, so that means 7 min 20 sec approx) on your pack to wring out all those 80%.

Note that the whole calculation depends heavily on both how long your flights actually are and how much mAh:s you do put back into your packs so the more precise numbers you have the better. Then again the 80% rule is a rough recommendation so don't overdo the timings and amp-readings, we don't need sub-seconds resolution or down to the last digit mAh readings!

[Pinecone]

Pardon me, but I'm new. I'm going to need the elementary school explanation. Lucy... Please 'splain the 80% rule. :oops:

OK, I am currently using the Align 22.2v 4600mah LiPo's. I am not using an alarm yet, so all I have to go on is the timer on my DX7.

Now, my packs are new, so I have not yet intentionally ventured beyond five minutes of run time.

Charging back up, I note that at the beginning of the charge, the cells are averaging 3.8v each. I seem to be putting about 2200-2500mah back into them upon charge completion. So, what would be my 80% target number to shoot for??? I feel like I can safely go beyond five minutes, but have so far been afraid to try... On a 4600 mah pack, how much amperage should I be pumping back in if I am running them down far enough to get the nominal time out of them???

Many thanks from the FNG. :D

You are shooting for 80% of the pack capacity. So for your 4600 mAH packs you want to put back in no more than 0.8 x 4600 mAH = 3680 mAH.

So in your case, you use about 2500 mAH after 5 minutes, so you are using 2500 mAH / 5 minutes = 500 mAH per minute. So you can safely run about 3680 mAH (max safe usage)/ 500 mAH per mnute = 7.36 minutes, or safely about 7 minutes flying the way you are. If you start flying more aggressively, you should recheck the numbers

[PsychoPilot145]

Thanks guys!!! Another mystery solved by the freak. :)

That explains it perfectly. I am just learning right now, so I am just doing hovering with slow forward flight... With training gear. :shock: Hopefully that will come off today, or next week at the latest. The low drain on the cells is probably from the low head speed (1800) and low pitch values (+10/-4) I am running for training.

Once I learn how to shred the bird, I imagine that time will fall. I'll step up the time today, and monitor the charging a little more closely. I have about four cycles on each pack now, so I think they are breaking in OK.

[Hughes500Bob]

Here is the link to the Lipo Sack containment video http://www.rchover.com/inc/sdetail/55966

Judge for yourself. I say it works as advertised! :bomb:

You can also use a Pyrex baking dish or other fireproof container THAT WILL VENT. Maybe you could put it inside an Ov-Glove :?:

[FearNot]

Thats pretty wild ... makes you wonder how healthy those fumes are ...

I think i will charge batteries outside from now on ...

Matt

[PsychoPilot145]

I have been attending my chargings using extra vigilance. But what the heck, you can't be too safe.

I have a fireplace with a rugged spark screen... Hmmmm. I would say, issue solved. :thumbup:

[Hughes500Bob]

The fireplace or a wood stove is an excellent idea :!: :lolol Keep the flu open while charging.

[528hemi]

I set my soft cutoff to 3.6 volts on a 2170 FP 3s1p pack and as soon as I feel the power drop, I land...The voltage is about 3.6 on a Tp210 balancer which I hear is OK but I find I put back 90 to 95 capacity?

So What I think I understand is you can discharge safely to 3.0Volts and use almost the full capacity BUT that will shorten the packs life?

Is this a correct statment?

Thanks for the help

[Gary JP4]

So What I think I understand is you can discharge safely to 3.0Volts and use almost the full capacity BUT that will shorten the packs life?


That is probably correct as far as damage if you are acknologing you will be doing some "shorten the packs life?" I guess you are asking so, yes. As far as safe it is debatable. You are probably not going to catch it on fire.

3.6 after recovery sounds about right but I wouldn't base it on that. Damage happens somewhere between 3.0 and a little below while it is under load. So the problem is what was your voltage during discharge. Under higher loads it will be lower then when the load is taken off so you don't really know how low it was. If you had a lipo warning on the heli and you stopped at 3.3 volts that should be fine but you are not measuring that.

If a cell becomes lower then the rest (out of balance) the problem becomes bigger. I would base it on how much you put back in. Timing the flight so you have to put back 75% or 80% of capacity to be fully charged would give you a better chance of avoiding damage to the pack.

The flight power is a nice pack and it would be a shame to damage it over say 1 minute of flying. I just ordered two.

[Pinecone]

My packs are more like 3.7 - 3.75 volts per cell when they go on the charger. And that is putting back in almost exactly 80%

[Gary JP4]

It is interesting to note but, I just wouldn't base it on battery voltage going to the charger.