I have already submitted all my information to the IRIS Hardware support forum, so I thought I'd share this video with my fellow IRIS owners.  I had heard about the IRIS props just stopping but I thought I was immune since I have been having so many good flights.  As you will see from the video, the IRIS went down from a pretty good height.  Luckily into grass.  The Tarot Gimbal does a good job of keeping the camera still even during the fall.

Looks like I'm out a Tarot Gimbal mount, one arm and 4 props because it cratered.  The gimbal PCB and motors are all still good.  Even the GoPro survived as you will see.

Now I have to figure out how to get my new parts.

Here's the video:

http://youtu.be/lL8Q3vqx0WI

Views: 3054

Replies to This Discussion

Ken,

I think we need to find a better battery.  Carrying anything with weight (like the gimbal) will severely shorten the battery life.

My advice would be, as soon as you find you need to increase throttle to maintain altitude due to low voltage, LAND THE IRIS.  At wide open throttle on the quad dyno, I noticed that once the LIPO battery gets down under 11v it can drop to single digits within a few seconds.  This may be faster than someone could react and land safely.

The deep or rapid discharge will leave you with a swollen/puffy appearing battery that won't perform very well. 

-Joe

PS: Sorry for your troubles.  I hope the repairs aren't too costly.

Joe, thanks for the advice.  I've made a determination that despite the simple instructions that are provided to us on how to charge, plug in and watch for "puffy" batteries, I need to become an expert on LIPO battery maintenance - and get all the necessary tools to do so.  This charger doesn't seem to be all that is necessary to do it.  Like finding a good internal resistance tester, and investing in a better charger than the one that is provided with the IRIS.

Simply looking for a "puffy" battery pack is apparently NOT the only indication apparently that your battery is damaged, as mine are still the same thickness that they were when I bought them, and I'm talking within a 16th of an inch.

So, what do you use for your batteries?

If anyone wants to sell me some M.A.I.L prototypes I'd be willing to test them for you.

Ken,

To be honest, I'm not sure what I'll use yet.  I'm still doing research and haven't decided if I want to invest in in a good LIPO/LIFE charger or try some more exotic batteries.

I found this URL interesting.  Not sure how much of these options you could actually buy in the US.

http://robotics.stackexchange.com/questions/554/quadcopter-lipo-bat...

-Joe

Ken,

Please post any information you find about the battery maintenance and alternative chargers. I've had my own issues with the battery that I posted about here http://ardupilot.com/forum/viewtopic.php?f=48&t=6774 .

Before my next flight I want to find out a way to check the health of my current 3DR batteries. I believe one of them is damaged somehow because when I charge it the status lights only show 'discharging'.  

Here is some very good information that was sent to my by Craig at 3D Robotics after the findings on the crash.

 

All You Need To Know About - LiPo's
INTRODUCTION

Lithium polymer batteries or LiPo batteries are currently the most
efficient power sources available with the highest possible specific
energy. This means that you get more power and capacity from a smaller and
lighter battery. To accomplish this, a different technology is used
compared to NiCd, NiMH, and Li-lon batteries; subsequently, slightly
different handling and charging applies. Please read the following safety
guidelines to familiarize yourself with the specifics of these batteries.

*TECHNICAL*

Some technical terms explained: Voltage and capacity

Because 1 Lithium element or cell has a (low) fixed voltage of 3.7 V. most
batteries or packs are built up from a number of Lithium cells in series.
The amount of Lithium cells in series is the indicated by the letter 's'
e.g. 3s battery. You can determine the total nominal voltage by multiplying
this number with 3.7V. In our example 3s battery gives 3 x 3.7V = 11.1 V.
this is an important value when It comes to choosing charger parameters,
the charger settings must match the LiPo. (See chapter Lithium polymer
batteries)

3.7V is the average voltage; LiPo can be charged up to 4.20V and discharged
down to 3.0V per cell, any lower or higher in voltage and the cell will
almost certainly be damaged and will become unstable which can be very
dangerous (fire risk).

The capacity of the battery is indicated with 'mAH' e.g. 1500 mAH. This
tells you how much energy it can contain. MAH is the abbreviation of milli
Ampere Hour or 1/1000th Ampere Hour. (1000 mAH = 1Ah)

The capacity tells you how long it takes to discharge a battery of 1500 mAH
can provide 15000 mA (milli-Ampere) or 1.5A during 1 hour, or twice as much
(3000 mA or 3A) during half an hour, ect. Because Lithium batteries come in
variety of capacities, the 'C' rating is used to determine the maximum
allowable current x C value e.g. 1500 mAh x 30C = 45000 mAh or 45 A.

Maximum allowable discharge current is usually between 10C and 50C, *maximum
charge current is always 1C*. (Whilst some LiPos can be charged at higher C ratings up to 5C, doing so will shorten the life of the battery, so it is
good practice never to exceed 1C)

 

In case of a 3s 1500 mAh battery with a 30C rating, the maximum
(continuous) discharge is 45A and the current is 45A and the charge current
is 1.5A (15000mAh x 1C = 15000 mA or 1.5A)
CHARGING LITHIUM POLYMER BATTERIES

As mentioned before: if the voltage of a single Lithium cell exceeds 4.20V,
it will become unstable. When this happens the cell will over heat, swell
up and rupture whereby the electrolyte can spill and catch fire! Because
the technology of the LiPo batteries is different from other batteries, you

must always use specialized LiPo charger. *Under no circumstances attempt
to charge a LiPo with a NiCd/NiMH charger.*

The charger parameters must match the LiPo and must be verified each time
before you start the charging process:

- The programmed number of cells must be the same as the LiPo or the nominal voltage must be equivalent. A 3s must be charged with 3s or 11.1V
setting etc.

- The charge current must never exceed 1C (for a 1500 mAh battery: 1.5A)
- A balancer must be used to balance the voltage of individual cells during charge. (See chapter: Balancing)

To further avoid fire risk always respect the following precautions:

- *Never charge the battery unattended*
- If you have a multifunction charger, thoroughly read the instructions and make sure it is in LiPo mode.

- Verify that the total voltage in the pack never exceeds the amount of cells the amount of cells in the pack may never exceed (5 x 4.20V =) 21.00V

- Put the charger and battery on a non-flammable surface, like a ceramic tile, during charge and make sure no flammable objects are within a radius of 1m.

- If possible, put the battery inside a special LiPo bag or in a
fireproof container during charge.

- Never charge inside a car, clubhouse or garage and if possible, keep a dry extinguisher or fire blanket ready. Never charge the battery while it
is in the model.

- Stop charging immediately if the battery gets warm or swells, disconnect the pack and put it in a safe place for observation for a few
hours.

- Never charge or recover a battery pack that damaged/bad/swollen cells, or cells that are below 3.0V

- Use properly insulated connectors and charge leads at all time.

BALANCING

Because the charger only measures the total voltage of the pack during the
charge, the individual cells must all have the same voltage at all time.
Otherwise the total pack voltage might be correct, but some individual
cells might already exceeded 4.20V. E.g. a 2s pack that has reached 8.4V is
fully charged, but if one cell has a voltage of 4.10V, the other cell will
be at 4.30V and will overheat. To avoid this situation, specialized
balancing circuits or balancers are available or are built into the
charger. Make sure that the connector type of your balancer match the
battery and always check if all cells are recognized. (The indicated number
of cells on the balancer must match the number of cells in the pack.)

*Always use a balancer during charging *and preferably use a charger with integrated balancer. If a separate unit is used, always use an active
balancer that has the ability to interrupt the charging process if
necessary.

 

*USING LITHIUM POLYMER BATTERIES*

Lithium Polymer batteries can store a tremendous amount of energy and
therefore must be handled with care. A fire risk exists and precautions
should be taken to minimize this risk. There are two main factors that can
possibly cause a fire during use:

- Physical damage: one or more cells are punctured, deformed or exposed
to extreme conditions
- Internal damage: one or more cells are punctured, deformed or exposed
to extreme conditions.
- Internal damage: one or more cells are discharged too fast or too deep.

To avoid this please respect following guidelines at all time:

- Never expose LiPo batteries to extreme heat (heater, fire, flame, exhaust, sun); never leave them inside a car for a long time.

- Never puncture a LiPo cell, as it will immediately catch fire. When installed in the model, make sure it cannot touch protruding screws, or
sharp metal parts. Make sure the battery is well protected in the case the
model should crash.

- Never put a LiPo in your pocket, as key chains or other objects may
puncture it.
- Do not deform the battery. If it should have deformed during a crash or transport, never try to force it back into its original shape but
dispose of it safely. (See chapter: disposal)

- Always transport LiPo batteries in a fireproof case where it cannot come in contact with other objects.

- After a crash, put the battery in a safe (fireproof) place for observation for 24 hours before using it again. It might have suffered
internal damage, which might cause a delayed reaction.

- When one or more cells have swollen, dispose of the battery pack immediately, do not try to recover it or recuperate separate cells.
Reassembling packs from different cells is dangerous if not done by
professionals. Furthermore all factory assembled packs are composed of
matched cells, when random cells are used to compose a battery packs, the
different characteristics of the cells will affect performance adversely
and this can be dangerous.

- Don't let the LiPo cells come in contact with water, if this should happen; dry them quickly with a towel.

- *Never exceed the maximum stated discharge rate. (e.g. 30C)*
- Never allow the battery to short circuit. Use properly insulated connectors and isolate them additionally during transport if necessary.

- Never allow a battery to exceed 60°C (140°F) at any time.
- Never allow the pack to be discharged below 3.0V per cell; preferably use an ESC with LiPo low voltage safety cut-off. Over discharging causes
permanent damage to the cell.

- When one or more cells are below 3.0V after use, don't try to recharge
them.
- Stop driving as soon as you notice a drop in power. However tempting it may be to continue, you will almost certainly discharge one or more
cells in the pack.

- *After use, let the battery pack cool down completely before
recharging.* Failure to do this will result in the rapid deterioration of your battery pack and can be dangerous!

- When the battery consistently gets very hot after use, check the gearing and make adjustments if possible. Discharging batteries at maximum
discharge rate for prolonged times will shorten the life of the battery
considerably.

- Disconnect the battery from the ESC or load after use avoid slow over
discharge.
- Make sure the battery is well ventilated in the model to avoid heat
build-up or thermal runaway.
- Don't let children handle these batteries without adult supervision.

STORAGE OF LITHIUM BATTERIES

For long time storage it is recommended to
discharge/charge the batteries to 50-40% of their capacity (or 3.8V per
cell). Never store LiPo batteries fully charged, not even for a week, the
performance will degrade noticeably. Keep the LiPo batteries stored in a
fireproof location at room temperature.DAMAGED LITHIUM BATTERIES AND

DISPOSAL Please take great care when a battery has been involved in a crash:

there might be visible and/or invisible damage to the cells, which may
cause a violent (delayed) chemical reaction. If possible, remove the
battery from the model as soon as possible and put it in a fireproof
location for at least 1 hour for observation. Be careful as the cells may
be very hot and they might be leaking electolyte; wash your hands with soap
immediately. Should you get the electrolyte in your eyes, flush generously
with water during 10 minutes and seek medical attention. Wait at least

24hours and inspect thoroughly before reusing the battery.If the battery should catch fire immediately after the crash, don't attempt to remove it
from the model, use a fire extinguisher!

 

When a Lithium battery pack is damaged or needs to be disposed of, proceed
as follows:

- Submerse the battery into a container filled with about 10L of salt water. (Add a cup of salt per 10L)

- Leave the battery submerged for 2 weeks; this will slowly and safely discharge the battery until the voltage has dropped to 0V, which eliminates
the risk of any chemical reaction.

- After 2 weeks, place the battery in the trash.

I've had the IRIS shut down completely twice. Once it was at 11.3 volts and then slam. All data stopped in the logs at that time and the Pixhaw quit telemetering. Both times it was when I was using the stock batts. I have a ThunderPro battery that it has never happened with. 

Not enough data to prove anything yet just stating some facts. Both times it shut down I was in loiter and about 5 feet from the ground. It could be a problem with loitering so close to the ground?

Mark,

When you are looking at your logs, are you downloading them from the IRIS with Mission Planner or are you physically taking them from the SDCard inside the PixHawk?  If you download them from Mission Planner, it will appear that they just stop, but in reality the logs are getting truncated.  That was my exact situation.

You get a much better reading of your logs when you get the .bin files right off of your SD Card.  That's why they sent that SDCard adapter with the IRIS.

I discovered the hard way that when LIPO batteries experience too many deep discharges they suddenly drop in voltage like "off a cliff" instead of slowly discharging.

Ken,

I am retrieving them directly from the card. Don't get me wrong, I have had plenty of successful flights. Those 2 times when it dropped out of the sky it lost comm with the computer, props stopped and it fell but when it hit the ground motors were still trying to run. Lost 3 props on that one. The logs showed desired yaw, pitch and roll going all over place and then data stopped. Battery was at 11.3 when it happened. None of my batteries have been below 9.9 volts but I noticed the Thunder Pro battery I bought has a much flatter discharge curve below 11 volts where the 3dr batts discharge much faster below 11 vdc.

like I said I may have been too low in loiter. I was only about 5 feet off the ground. I had telemetry going both times it died as well. I have many flights where the computer wasn't on (no telemetry ) and have never had any issues. 

I'm sure I will learn more about it as I go forward. I'll be doing more flights next weekend. I'm going to fly it around a lot in loiter before I do an auto mission.

thanx,

mp

@Ken

Sorry for your loss. Here's a simple way to prevent this sort of thing, without telemetry, and also maximize battery life (my practice for the past 7 or 8 years of using LiPos in everything from big helis through planes, very fast r/c cars, and multis).

1. Use only quality chargers that give you data and that are made for LiPo batteries.

2. Always balance-charge. Every time.

3. Charge at 1C (some new batteries claim to be safe at higher rates, I'm still sticking to 1C).

4. Never intentionally discharge below 80% of capacity. This is key.

5. Determine by observation the consumption per minute of your aircraft. First flights with a new battery and/or new aircraft should be very conservative in terms of time in the air. Be sure to log the time if the aircraft doesn't do it for you (or if you have video recording on or off the aircraft you can pick the time up from that later). When you charge the battery, note how much it's taken to fill it and do the simple math to determine how long you can fly on 80% of nominal battery capacity (meaning for example using 4000 Mah of a 5000 Mah battery). Repeat this a few times to verify the figure.

6. Use a timer during flight. Have it set for your 80% figure. Best is if your Tx has one built in, and best within that is if it can be configured so it counts when the throttle is open and not when it's closed. Obey the timer.

7. Be aware that conditions may vary and affect "fuel" use. But most the time you won't see much difference in consumption from flight to flight, and the 20% cushion should cover you. If you do suddenly fly a lot differently than usual, or if it's unusually cold or hot, be conservative and later look at the numbers.  (Note that the cushion is not just "reserve" fuel, but also in my experience it's better for the battery's longevity to not run it down further routinely.)    

8, Each time you recharge a battery, do the quick simple math and see that there hasn't been any significant change. If you see a significant change, investigate. Another advantage of this system is that it can give you an early warning of trouble with the battery or with the aircraft.

This is really a simple system that can easily become a habit, it's worked well for me. Hope it helps.

 

Olver,

Thanx for the wise advice. I bought a better charger and started logging the total mah and time for each charge to spot anomalies. Also using storage charge for when I"m away on business for a week or two. Been doing lipos for a while but never anything the draws this kind of current.

Do you recommend any specific brand of batteries? My local hobby shop will order just about anything. I don't mind paying extra for reliability.

mp

Hi-
I think using a radio with telemetry is really helpful here, too!
(Monitor Voltage / consumed mAh if possible)
Greets

Oliver,

Thanks for the information it was very beneficial.

Do you have a recommendation for a charger that can meet all of your criteria? 

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