HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Mar 15, 2015, 11:50 PM
Registered User
United States, MA, Lowell
Joined May 2004
1,141 Posts
But discharging down to a resting voltage of 3.20v/cell IS overdischarged, isn't it? If you routinely flew your LiPos long enough each flight so that the resting voltage was 3.20V/cell after the flight, that battery is overdischarged. I understand that under load they routinely drop to 3.3V/cell near the end of the flight if you go WOT, but they don't stay there.
Neil_SC is offline Find More Posts by Neil_SC
Reply With Quote
Sign up now
to remove ads between posts
Old Mar 16, 2015, 05:23 PM
Registered User
Seattle
Joined Sep 2007
2,349 Posts
Quote:
Originally Posted by Neil_SC View Post
But discharging down to a resting voltage of 3.20v/cell IS overdischarged, isn't it?
Well yes. But that was not the point of the users post. His concern is that the charge failed to stop at the set voltage.
Gregor99 is offline Find More Posts by Gregor99
Reply With Quote
Old Mar 23, 2015, 03:20 AM
Registered User
Joined Mar 2014
9 Posts
Does anyone know if you can use the powerlab 8 as a bench power supply? surely the hardware is more than capable of doing this.. it would be an awesome feature that would make this incredibly useful charger even more amazing! I've seen the "Foam Cutter" mode but that doesn't appear to let you set the voltage.. only current.
F1nn is offline Find More Posts by F1nn
Reply With Quote
Old Mar 23, 2015, 06:15 AM
ancora imparo
jj604's Avatar
Melbourne, Australia
Joined Jul 2005
7,452 Posts
I do not think you can use a buck/boost switched mode power supply (which is what the PL8 fundamentally is) for that purpose. It is inherently unstable when the output voltage is around the same value as the input voltage.
jj604 is offline Find More Posts by jj604
Reply With Quote
Old Mar 23, 2015, 07:25 AM
Registered User
USA
Joined Jan 2002
4,999 Posts
Quote:
Originally Posted by F1nn View Post
Does anyone know if you can use the powerlab 8 as a bench power supply? surely the hardware is more than capable of doing this.. it would be an awesome feature that would make this incredibly useful charger even more amazing! I've seen the "Foam Cutter" mode but that doesn't appear to let you set the voltage.. only current.
There are no provisions for this, the charger was never intended to be used as a power supply.
Ohmic is offline Find More Posts by Ohmic
Reply With Quote
Old Mar 24, 2015, 08:42 AM
Registered User
Joined Jun 2005
41 Posts
Quote:
Originally Posted by Gregor99 View Post
Correct. Its a setting on the discharge tab, as well as configurable via the console. Bryon01 uploaded his preset and he has it set to 3.20v. I looked through the preset and didn't see any issues that would cause an over discharge. I'd like to see if his second attempt at discharging provides the same results.
I can do this, just been busy. Anyone else want to try as well?
bryon01 is offline Find More Posts by bryon01
Reply With Quote
Old Mar 25, 2015, 12:21 AM
Registered User
Joined Mar 2014
9 Posts
Quote:
Originally Posted by jj604 View Post
I do not think you can use a buck/boost switched mode power supply (which is what the PL8 fundamentally is) for that purpose. It is inherently unstable when the output voltage is around the same value as the input voltage.
Any decent buck/boost/sepic power supply will work well enough when input and output voltage are the same. besides i don't mind running the input at 24V to get 12V output in a purely buck situation, i believe the hardware is capable but there is just no preset mode for it.
F1nn is offline Find More Posts by F1nn
Reply With Quote
Old Mar 25, 2015, 05:51 AM
ancora imparo
jj604's Avatar
Melbourne, Australia
Joined Jul 2005
7,452 Posts
That may be true but some LiPo chargers (which are buck/boost systems) are well documented as having problems with power supplies that are around their switch over point. I just wondered if the same thing might apply to the PL8 when used as a precison constant voltage source (constant current may not be an issue).

John
Quote:
Originally Posted by F1nn View Post
Any decent buck/boost/sepic power supply will work well enough when input and output voltage are the same. besides i don't mind running the input at 24V to get 12V output in a purely buck situation, i believe the hardware is capable but there is just no preset mode for it.
jj604 is offline Find More Posts by jj604
Reply With Quote
Old Yesterday, 06:35 PM
Registered User
Joined Jun 2005
41 Posts
PL8 overdischarging at low current with CCCV and cell balance on

All I have learned is I don't trust this charger with these settings on so I recommend nobody else use it with CCCV and cell balance on discharge either. My biggest concern is whatever logic bug exists may also occur in some other combo of settings. I would like FMA to look into this.

Here is a graph with 1C discharge on a 4000mah pack. CCCV and cell balance on, does exactly what it should, and stopped correctly at 3.3V. The hysteresis in the cell balance was set to 3mV which was 1mV more than default.

Also attached is the same pack, only at 1/8th C discharge rate and 3.2V setpoint. I didn't charge it to test 3.3V cutoff, just set it to 3.2V and went. The only change to this discharge was the rate, the cuttoff, and I went back to 2mV hysteresis which I believe is the default. Again, the result would be a runaway dead battery if I wasn't watching it.
bryon01 is offline Find More Posts by bryon01
Reply With Quote
Old Yesterday, 09:13 PM
Registered User
Seattle
Joined Sep 2007
2,349 Posts
Quote:
Originally Posted by bryon01 View Post
Also attached is the same pack, only at 1/8th C discharge rate and 3.2V setpoint. .
OK so it works fine at 3.3v, but not at 3.2v? Not sure the charge rate has any impact, but I can look at that as well.

What wiring mode are you using? What balance adapter are you using? It may not be relevant, but in case I can't repro, it'd be good to know these things.
Gregor99 is offline Find More Posts by Gregor99
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Sneak Peek! 2, 1:8 scale scratchbuilts ooby Scale Boats 32 Sep 17, 2014 03:09 PM
Discussion Proposed schemes for 2010 season RAF BAe Hawk display-sneak peek! Matt Halton Electric Ducted Fan Jet Talk 3 Dec 20, 2009 03:11 AM
Discussion Sneak Peek at the New Creation Museum Miami Mike Life, The Universe, and Politics 38 May 30, 2007 05:01 PM
Hey Mr. Lin, how about a sneak peek at the Hellcat? splatman GWS (Grand Wing Servo) 1 Jul 05, 2003 04:43 AM