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Battery consumption, capacity etc.

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Hello ensemble,

I have read several posts mentioning batteries, consumption, capacity but never found a concrete value about that. Did I miss something?
This is a technical subject, where suppositions, statements and claims are worth nothing.
I did then a concrete test.
There was no wind at all. Temperature was 6°C.
Batteries are charged with a Thunder Power 1010 charger and its dedicated balancer at 5.4A

1. Battery consumption at ground.
I left the TH switched on for 30 minutes with a freshly charged battery, with video on and everything ready to run.
I recharged the battery with 489mAh.
Round it to 500mAh for 30 minutes and that means a consumption of 1A. Plenty of juice to take off and make a long flight, even after long waitings.
2. Battery consumption when hovering.
Took off and landing gear up. Left hovering for exactly 15 minutes, including takeoff and landing. Landing gear down, landed, switched off. I did not compute the couple of minutes to get GPS lock and video as those are something ridiculous (about 30mAh).
Consumption was 4751mAh, 317mAh/min.
This means 19A total consumption and 3.2A each motor.
Assuming a battery of 6400mAh this means discharging it at a rate of 3C, almost nothing.
3. Battery consumption under charge.
For that flight I did like the previous, but climbed and dived all the time at the maximum speed allowed.
Flight duration 10min 50sec. (was planned 10 min, but I had problems to land it. See my other post on the firmware thread)
Battery consumption was 3650mAh, 337mAh/min.
This means 20A total consumption (well 20.22A), 3.4A each motor.
This means a discharge rate of 3.16C, just slightly higher than hovering.
Considering a battery discharge level of 70%, from a 6400mAh battery we can expect 4480mAh usable.
This gives 14 minutes of hovering or 13 minutes climbing and diving.
Just for fun the TH could be left on at ground for 297 minutes, almost 5 hours.

Let consider a discharge level of 80%, probably still safe but at the limits. Capacity available from 6400mAh battery is then 5120mAh.
This gives 16 minutes hovering and 15 minutes climbing and diving.

To finally go to an end what can I expect if I use a 7000mAh?
70% of it makes 4900mAh usable.
Hovering 15min 45sec.
Climbing and diving slightly less than 15min (14:54).
This in theory, because if aftermarket batteries with a lower internal resistance are used, this could lead to an increase in current delivery and then consumption. Ok better performances, slightly better, but at the end, ... surprise! less flight time ...
So before any more claim etc., I expect real tests, just to have a concrete base of discussion.

Best regards,
Ric

P.s.: I would suggest a way to check if batteries are sound and of good quality. The balancer is a good, simple tool to check that. If batteries after a flight, are balanced within thousanths or hundreths of Volt, they are sound and the pack is a well balanced pack. Values I get usually are 0.009V to 0.02V, so mine are really good packs. Avoiding deep discharge means first of all avoiding big voltage differences between cells, which could be a real problem for pack life.
 

PatR

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Thanks for your efforts. I don't have the time to do a lot of testing but what you've done confirmed my max flight time estimates, which I stay on the conservative side with.


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i posted similar info a while back of my own testing but it will do no harm to post more info again.

unfortunately though many people simply don't understand these batts and there is no real need for them to do so either if they don't want to.

the issue is people who shouldn't comment do so and you end up with a lot of drivel on batts being posted....this is the same on every forum though.
 
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Thanks for comments!

To make this test more readable, I would add some information about batteries discharging.

A battery is considered discharged when it reaches its minimum allowed voltage, under a load, usually 1C.
C is a value relative to battery capacity. Discharging at 1A a 1000mAh battery, means applying a load of 1000mA, or 1A. At 2C it is the double, 2A, ad so on.
E.g. a NiCd has a nominal voltage of 1.2V, a full charge voltage of 1.25-1.35V and a discharged voltage of 1V.
So discharging it a 1C, means reaching 1V and measure how many mAh where discharged.
It does not mean discharging it completely.

Lipo batteries are more delicate.
Nominal voltage is 3.7/cell, maximum voltage 4.2V, minimum voltage 3V. Go under 2.7V means starting to degrade the chemicals.
Capacity is measured discharging it to 3V/cell, under load, but a good practice is to not discharge it below 3.4V/cell. Capacity does not change a lot, because under 3.4V there will be a sudden voltage dive.
Deep discharge Lipo batteries means increasing a lot internal resistance, with really bad things following, the least being getting hot and inflating.

Lipo discharge is a perfectly safe operation, until it is done under strict conditions. This means discharging it with a charger and a balancer that don't allow it to go under a given voltage. The balancer is mandatory for packs, where it checks constantly each cell and don't allow single cells to go into a deep discharge.
I do that occasionally to check capacity and batteries health.

At the end discharging TH original battery to 70% means getting the values I already reported in the first post. Check for voltage also, because if to get those values you are getting too much low voltage, it means that the battery has an increased internal resistance (because of usage, misuse, low temperature, previous deep discharges, etc.).

Ric
 

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