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› Powerlab 8 users, got a question..
05-02-2011 04:59 AM  6 years agoPost 1
big_swede

rrVeteran

Sweden

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Im new to big electrics, and I have a question about the "fuel" value and the "Cap = mAh in" value in the Powerlab 8.

This is for my rave 700 12s 5000 setup

I test hover the heli at 1650 rpm for 6.30 min with my fully charged 2x 6s 5000mAh lipos.

Then I hook up the 2x 6s 5000mah lipos in parallel to my powerlab 8.

The readout whas:

Cell v = 3.85 across
Volt = 23.2
Fuel = 54%

I then startet to charge the pacs at 1c.
After the pack got up to a fuel level of 100% the "Cap = mah in" whas showing 769mAh.
That cant be right?? Or?
It seems to low, only 769mAh in going from 54% to 100% on a 6s 10000mAh ( 2 6s 5000mAh in parallel )?
Do I read this wrong in any way?

Thanks for helping..
Sry for the bad English..

JR Vibe Ito Edition, JR Nex E8, JR E550, TAGS01 FBL system, JR XG8 radio

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05-02-2011 06:02 AM  6 years agoPost 2
TJinGuy

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Socorro, NM - USA

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"Fuel gauges" are not accurate, period. They use voltage to estimate capacity and that is flawed. But aside from that, a voltage of 3.85V is approx 50% discharged. So it should put back in 2500mAh into a 5000mAh pack. I know that the PL8 can "aid" you in parallel charging, so what it reports can be influenced by those settings. Still 769mAh returned is too low for a 6.5min hover at 1650.

- Chris

Team New Mexico
TJinTech

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05-02-2011 06:12 AM  6 years agoPost 3
big_swede

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Sweden

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Thanks for the answer

Yeah somethings is strange here..
Because if I only look at the cell volt and the "fuel gauges" they seems to be "ok" or within reason.
3.85 is approx 50%/fuel gauge is showing 54%..
And when the fuel gauge shows 100% i got 4.2 volt across the cells.

Whats bugging me is the Cap = mAh in" value that seems to be wacky and way to low..

JR Vibe Ito Edition, JR Nex E8, JR E550, TAGS01 FBL system, JR XG8 radio

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05-03-2011 02:59 AM  6 years agoPost 4
Gregor99

rrElite Veteran

Western Wa

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The readout whas:
Cell v = 3.85 across
Volt = 23.2
Fuel = 54%
The PL8 like all FMA chargers uses a "fuel map" to estimate the pack's state of charge. The estimate is based on pack voltage. Many many years ago when this feature was first implimented, this worked quite well. But as packs have evolved and changed, a single fuel map does not accurately describe the state of charge for all packs. Because of this FMA added a custom fuel map wizard which first appeared in the Multi4 and was carried into the PL8. Cycling the pack using the wizard, the software "learns" the fuel map for each pack and from that point forward, the fuel readings are far more accurate.

All that being said, I don't find the fuel gauge very useful and tend to look at cell voltage instead.
It seems to low, only 769mAh in going from 54% to 100% on a 6s 10000mAh ( 2 6s 5000mAh in parallel )?
Do I read this wrong in any way?
When you start the charge, the PL8 will ask you how many packs are being charged in parallel. If you select 2, the mAH reading is divided by 2. So if the charger puts 1538 mah in the packs, the report will be per pack (estimated) at 769mah.

For now, I would forget about using the fuel gauge as your guide and watch the mah values put back in the pack. If you select 2P during the charge, then remember the value is per pack.

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05-03-2011 03:18 AM  6 years agoPost 5
rexxigpilot

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Florida

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Are you using the FMA parallel boards or simple parallel cables from say Progressive RC? I use the Prog. RC parallel cables. I almost always charge in parallel, but when the charger asks if charging in parallel, I tell it no. This will give accurate % fuel level. However, the mAh put back in will be for all packs combined. For instance, if 2,500 mAh was put back into each of 4 packs, the "Cap =" reading would show 10Ah (10,000mAh).

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05-03-2011 04:28 AM  6 years agoPost 6
big_swede

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Sweden

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Thanks

Yes I use the FMA parallel boards.

So its no "danger" to NOT select 2p even if you charge 2 6s lipos?

/a

JR Vibe Ito Edition, JR Nex E8, JR E550, TAGS01 FBL system, JR XG8 radio

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05-03-2011 05:39 AM  6 years agoPost 7
Gregor99

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Western Wa

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Its no problem to not select 2p, but there is no reason not to. The parallel selection does not affect the fuel map.

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