more out of a battery then the rated capacity

[Desmoboy]

I am new to this and have a pair of 4max purple power 4S 6000mAh batteries.

I charge them at only 1C and in the few flights so far i never go below 14 volts before i land, usually just above that actually. Understand that going below 3.25 /cell is a recipe for trouble so my 3.5v/cell is safe i believe. In truth a couple of minutes after the flight is finished they might actually measure approx 15.5 volts once they have recovered and this is where i start the charge from obviously.

The thing is, my charger has on occassion said that it inputs 6000mAh back into them to a max voltage of 16.8v

So, 6000mAh from a start point something over 15 volts is interesting.

Charger is overlander RC-6S AC Pro 80 watt

[Benjamin Kenobi]

You should be putting back in 4800mah (20% rule). You';ll shorten the life of your lipos if you constantly take too much out of them.

Ideally you';ll be using a timer to time your flights and an OSD to show voltage in flight. You';ll soon get an idea of what time/voltage will only take out 4800mah.

Cool?

[teslahed]

The 20% rule means your lipos will last longer and it also means that if you do misjudge slightly your aircraft wont fall out of the sky.

[Desmoboy]

I am using telemetry and i time the flights. Also watch very closely the voltage drop in flight.

I don';t go below a very conservative lower limit, (review the above figures) so i don';t believe i am taking too much out of them. The voltage when i have finished confirms this i think. The voltage is confirmed by a separate multimeter so that is correct.

[teslahed]

Voltage drop counts for much less than mAh used because it can vary based on many factors including battery temperature and current load. Just because you voltage isn';t dangerously low doesn';t mean you aren';t damaging your battery by using too many mAh.

You really should land with 20% spare if you value the longevity of your LiPos. All voltage tells you for sure is that your multirotor hasn';t fallen out of the sky - yet.

[guest325]

I can only echo what others have said, the thing I have found is that some batteries maintain voltage up to the point where they are nearly completely drained; this doesn';t mean that you are not damaging them by using them to this point. The other downside of letting them get to this point is that they suddenly loose power and will fall out of the sky, time your flights by checking how much you have to put back in - it';s the best way to prevent damage to your batteries and make them last longer!

[flybywire]

Voltage drop becomes more pronounced the older and more used your lipo';s become which makes voltage remaining a less reliable indicator, in my experience.  Osd';s with mah consumed are the best, and most reliable, again in my experience!

[tupoar]

I';m confused. I use a low battery alarm which is set to 3.5v. I land when it goes off. Whenever I charge them, I';m putting back at most 50% of max. So am I safer staying that way or time my flights and stick to that?

[nub]

i usually just time my flights, no hassles.

[flybywire]

Yeah, i do that as well, i don';t think there is perfect system, just experience.  The more you fly and drain your lipo';s, the more you';ll notice a quicker drop of voltage, but you';ll still get a fair capacity, but if you look at voltage only, you';ll be landing well before the safe 20% remaining.  Sorry i';ve had a couple, so i know what i mean if you don';t!

[teslahed]

I';m confused. I use a low battery alarm which is set to 3.5v. I land when it goes off. Whenever I charge them, I';m putting back at most 50% of max. So am I safer staying that way or time my flights and stick to that?

Because your voltage alarm is set quite conservatively you aren';t getting full use out of your lipos. That';s not a problem and your lipos will love you for it - it just means shorter flight times.

Try timing how long it takes until your voltage alarm goes off. Say it';s 10 mins for the sake of argument and to make the maths easy (it';s probably less in reality). You now know that 10 mins of flying the way you usually do runs your lipos down to half based on what the charger says it puts back in. Do a few similar flights to make sure it';s always about the same.

Next time fly for 15 mins. Pay careful attention to how much your charger puts back in. It should put 75% back in - that';s a good level to stick with giving you 25% in reserve for emergencies and to keep your lipos lasting longer in the long run.

Once you';ve done a few flights this way you';ll build up a confidence and a feel for how much you use if you fly a certain way. Now you can dispense with the lipo alarm and just fly using the timer. But it might be a good idea to leave the lipo alarm on and just lower it';s voltage cut off so it still sounds if you misjudge and your lipo is seriously low on voltage.

[Desmoboy]

This confuses the issue even more, sorry.

"Because your voltage alarm is set quite conservatively you aren';t getting full use out of your lipos. That';s not a problem and your lipos will love you for it - it just means shorter flight times."

I have stated that i land at the same voltage and have just been told that voltage is not a reliable method.

When i fly i have a very close second by second monitor of the voltage as it drops and i know when it starts to accelerate. I can visualise that acceleration overlaid on the classic discharge graphs of LIPO voltage drop off. We all know that once it gets towards the cliff it speeds up a lot. I stop before that happens and have at least 3.5v left.

[kilby]

You also state that you are putting 6k back into your LiPo which would imply that you are near using the full batter capacity.

One problem that confused me for ages was that my battery charger was putting much less than my battery checker said should.

Turns out that my battery checker was giving figures almost 30% lower than reality.

Therefore I bought a new monitor and spent some time comparing it';s reading against my Fluke and what the charger  said it was putting back in.

The figures now line up, and I know my 450 has a very happy 6 minutes and a 20% reserve before I have to land.

I got tired of the on board battery alarm as it just whinged about battery sag all the time and was almost as inaccurate as the battery tester.

OK my tester was reading low but no doubt they can also read high

[Desmoboy]

And with respect that is the whole reason for my post in the first place.

Is it possible for Lipo';s to have more capacity than they are rated at ?


There is a mismatch in my eyes between the voltage left and the amps put back in.

[kilby]

I would check the battery with a decent multimeter and also check on another battery charger (it';s not unusual for a charger to he incorrect)

[Desmoboy]

Both of my batteries have been checked on a decent multimeter that has itself been referenced against another quality device.
Both batteries agree to within a couple of hundreth';s of a volt with mission planner. This voltage is a little offset from my charger but that has been taken into account.

Do not have another charger to try.

[dirtyharry]

My turnigy 5000 blue batteries would take 5400mah when new , I have a couple of chargers and they both fill up my batteries to the same levels.

But my 2200 zippy compacts only took 2050 out of the bag .

I guess it depends on the quality of the battery or the claims of the manufacturer.

I usually run them down to 3.5v per cell on the first couple of flights and then set my timer for 3/4 of that time for future jollies.

[Desmoboy]

Thanks dude that';s the first piece of evidence that i might be correct.

[teslahed]

This confuses the issue even more, sorry.

"Because your voltage alarm is set quite conservatively you aren';t getting full use out of your lipos. That';s not a problem and your lipos will love you for it - it just means shorter flight times."

I have stated that i land at the same voltage and have just been told that voltage is not a reliable method.

Voltage is not a reliable method of directly working out battery capacity % remaining. It is a reliable method of telling you the voltage though.

This means  that if you fly twice in a similar way using identical batteries then land both at the same voltages, then you';d expect to see them show a similar level of capacity left, either on your battery capacity checker or later when your charger counts the mAh put back in.

But you can';t use voltage as a way of measuring battery capacity directly because other factors influence the way it changes.

It is possible to use more mAh than a LiPo advertises itself as having. However, if you buy a 5000mAh LiPo you should expect to be able to use 5000mAh safely and reliably. In fact the LiPo might let you use 5400mAh but if you do that more than once or twice it might fail catastrophically.

So it';s always best never to use more than the rated number of mAh and even better to always leave 25% remaining.

[kilby]

Also when using a battery alarm I would not have it alarming at 3.5v as you may already have reached the point where the battery available power is close to dropping like a stone.

At best voltage is very very approximate guideline.

When I was using a lipo alarm I had it up at 3.7 as I wanted to be pretty damn sure that I could get it back to the ground safely, and yes I have had idiots turn up with their dogs (off the lead) and stand right in front of me while I am bring a quad in to land.

With the lipo alarm set as low as 3.5v the damn thing was still triggering when I pushed the 450 to do anything interesting (after it was in the air more than 3 or 4 minutes)

In the end I set up a spreadsheet that logged each battery, flight time, capacity remaining and what the charger claimed was being put back into the battery.

I then set the timer on my transmitter, to give me a full 90 seconds to get landed and still have around 25% left (in case some idiot and their dog wont bug**r off)