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08-07-2017 02:50 PM  77 days agoPost 1
Jabber

rrNovice

Hong Kong

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Anybody have any figures for HVLi batteries in terms of capacity/ voltage figures? I am trying to work out what is going on but without reference numbers it is difficult. All I need is one value for the at rest voltage against capacity, so I can calculate the capacity of a battery I have

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08-09-2017 01:52 AM  75 days agoPost 2
Rojoalfa

rrApprentice

Punta de Mata, Monagas-Venezuela

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/
/

Voltage in term of capacity? It is not related.
You can have a 6s lipo battery with 1000 mah and the same 6s lipo with 5000 mah.

Capacity en term of weight? Yes. It is related.

Heavier lipo with same number of cells mean more capacity.

If you want to get a relationship, try to get different lipo configuration and take measurement of weight...

Probably the result is a constant... In term of X mah/grs or Y mah/pound.

/

Saludos cordiales,

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08-09-2017 02:42 AM  75 days agoPost 3
Jabber

rrNovice

Hong Kong

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Thanks, but perhaps I didn't explain. As far as I am aware, there is a correlation between resting voltage and percentage capacity. I take your point that for different capacity batteries it is not an absolute method.

I missed saying 'percentage' which is how most of our field box and charger measuring devices work on.

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08-09-2017 03:58 AM  75 days agoPost 4
Pistol Pete

rrProfessor

Seffner, FL

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https://www.google.com/search?q=lip...mobile&ie=UTF-8

~~Enjoying the hobby one flight at a time~~

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08-09-2017 12:30 PM  75 days agoPost 5
Rojoalfa

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Punta de Mata, Monagas-Venezuela

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/
/

Rule of thumb..

Voltage LIPO 
4.20 100%, 
4.03 76%, 
3.86 52%, 
3.83 42%, 
3.79 30%, 
3.70 11%
3.60 0%

Very important...

This percentage are related to half capacity of pack.

The other half is not available.

For example, a 5000 mah pack, only it has a 2500 mah capacity available...

/

Saludos cordiales,

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08-09-2017 08:40 PM  74 days agoPost 6
Pistol Pete

rrProfessor

Seffner, FL

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Very important...
This percentage are related to half capacity of pack.
The other half is not available.
For example, a 5000 mah pack, only it has a 2500 mah capacity available
Where did you get this information?

Please elaborate and share.

Perhaps you are basing this on not dropping below 3.6V per cell? Which is 0.1V below nominal voltage.

If so, the 80% "rule of thumb" widely used is a ruse?

In the 10 plus years of using LiPos, this is a first of hearing about such a low value.

Perhaps this is the value that you use.

~~Enjoying the hobby one flight at a time~~

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08-10-2017 09:44 AM  74 days agoPost 7
Jabber

rrNovice

Hong Kong

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The question was about HVLi, so the maximum voltage is 4.35V. Most of what is being said here is about standard LiPO and is well known, except the bit about only half the capacity being available, on which I would welcome some elaboration.

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08-10-2017 03:00 PM  74 days agoPost 8
Pistol Pete

rrProfessor

Seffner, FL

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All I need is one value for the at rest voltage against capacity,
Divide the voltage printed on the label by number of cells.

Example using 3S
HVLi
11.4V ÷ 3 = 3.8V
LiPo
11.1V ÷ 3 = 3.7V

Now lets make an average percentage chart!

We start by using max voltage and calculating for 80% of usable voltage as per manufacturers recommendations.

4.35V (max) x .8 (80%) = 3.48V (new min or 20% reserve)

Next we calculate the available usable voltage which is the difference of max and 20% reserve. As an example, Hyperion (mayor distributor for G6 and G7 batts - HVLi) states 10% as absolute min but we will stick with the 20%, so

4.35 - 3.48 = .87 (80% usable voltage)

Next, we calculate for a base 10 chart

.87 ÷ 10 = .087 (10% incremental or decremental value)

So here goes the chart

4.35 = 100%
4.263 = 90%
4.176 = 80%
4.089 = 70%
4.002 = 60%
3.915 = 50%
3.828 = 40%
3.741 = 30%
3.654 = 20%
3.567 = 10%
3.48 = 0%
so I can calculate the capacity of a battery I have
By being consistent with the 80% rule of thumb, you can get this info from charger after it is done charging and use it as a base line to know how your battery is performing and when to replace it.

Rule of thumb is to replace battery when it can no longer charge to 70% of its rated capacity.

As with all rules of thumb, use it as an "approximate" means.

For what I have read, HVLi batts are not worth the investments unless into racing drones for money or glory.
I am trying to work out what is going on
Hope the above helps you out, otherwise, let us know.

~~Enjoying the hobby one flight at a time~~

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08-11-2017 04:04 AM  73 days agoPost 9
Jabber

rrNovice

Hong Kong

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Thanks for that. I am currently in the middle of doing some cycles with my charger connected to a PC which will give me some accurate information, hopefully. I will see how it compares. Ultimately all I was worried about was over-discharging and how my VBar coped with battery management for HVLi.

I kind of agree about the use of them though, they are expensive, and am told they don't last as long as standard cells, but you do get good flight times from batteries which are quite light.

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08-11-2017 04:29 AM  73 days agoPost 10
EEngineer

rrProfessor

TX

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Just be aware that the charge rate should be much lower than the discharge rate.

Logo 600SXs, 700XX, 800XX

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08-11-2017 05:30 AM  73 days agoPost 11
Pistol Pete

rrProfessor

Seffner, FL

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Found this downloadable PDF graph from Hyperion

HERE

~~Enjoying the hobby one flight at a time~~

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08-11-2017 06:54 AM  73 days agoPost 12
Jabber

rrNovice

Hong Kong

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I saw that, but the numbers are all wrong for standard Lipo, and they bear no resemblance to what I have found with the HVLi, either

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08-11-2017 12:47 PM  73 days agoPost 13
Rojoalfa

rrApprentice

Punta de Mata, Monagas-Venezuela

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erhaps you are basing this on not dropping below 3.6V per cell? Which is 0.1V below nominal voltage.
/
/

That's right.

Lipo real capacity is half of labeled capacity.

The first half is between 3.6 to 4.2 volts.
The other half is from 3.6 to zero.

Obviously, from zero to 3.6 volts is dangerous for lipo health...

We can do some test to probe this...

Discharge a fully charged lipo pack from 4.2 volts to 3.6 volts per cell.
Take note of reading capacity discharged.
Divide this reading from total capacity of pack...

Results... Near 50%

/

Saludos cordiales,

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08-14-2017 02:05 PM  70 days agoPost 14
Pistol Pete

rrProfessor

Seffner, FL

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True C rating...

Obviously, from zero to 3.6 volts is dangerous for lipo health
What is absolutely unhealthy is pulling above the TRUE C rating of the battery which in turn causes high temp and premature failure.

Temperature is critical.

Unfortunately, manufacturers marketing hype, buff the C rating.

The only means we have is to measure (IR) internal resistance at a constant temperature. Extensive data has been collected by a large unbiased group and concluded the best temperature is 72F. Letting battery rest for at least one hour between test will give you your geographical average room temp. As long as it's constant, your results will be consistent.

Apply OHMs law using the nominal voltage of 3.7V divided by the highest IR of any one cell to get the max Amperage you "should be" safely drawing from that one cell (technically the weakest cell). You then multiply the resulting Amperage by amount of cells in the battery pack. Althought it is said that above 140F is the temp where batteries start to suffer, I'd rather stick with keeping below 110F.

The above procedure will give you the true C rating as well as longer life from your battery.

Charging capacity also plays a role in longevity. I for one do not charge above 1C.

Given, manufacturers tolerance as well as the fact that Lithium batteries deteriorate from the date it was made, your life cycles will differ and never be constant. Too bad batteries do not come printed with the date it was made. If it did, suppliers-distributors would really be stuck with old inventory. There is a reason why you see "discounted sales".

Of course, you can continue only using 50% of your battery given you will most likely get the same cycles of those using 80%.

BUT

To state that below 3.6V per cell is "very dangerous" to LiPo health and not provide any data to validate it, well, it brings the likes of me that need such data rather than accepting it as a fact. Your statement invalidates all other data available.

~~Enjoying the hobby one flight at a time~~

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