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8464Re: [solectria_ev] Re: CALB 100's first drive

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  • Charles Bliss
    Oct 28, 2012
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      It is my understanding that taking them to 2.5 is into the damage zone.
      On my new pack, using a BMS, the batteries are all taken up to max 3.9,
      then balanced down to 3.75. From there, they settle to 3.52.
      On the very first charge, I had to bring up some low cells with a power
      supply but those cells are now balancing to within +/- .01 volts on
      regular charging.

      I am not clear on why you would bottom charge. Please explain.
      We never do it and the race bikes packs have never lost a cell. The
      only cells I have seen damaged are ones taken below 2.5.

      On 10/28/2012 7:31 PM, Tom Hudson wrote:
      >
      > A little status update on my CALB upgrade...
      >
      > I'm working on battery module 36 now (out of 56) -- I'm expecting to
      > have my Force back up
      > and running with the CALBs by Thursday of this week.
      >
      > I've been totally amazed over the fact that the regenerative discharge
      > isn't overcharging
      > the source batteries! Must be some inefficiency in the regenerative
      > discharge mechanism.
      > It turns out to be a great thing -- what I'm doing is individually
      > charging the modules to
      > 3.555 volts, then setting them aside. Each charge takes about 2.5
      > hours from the factory
      > charge level of around 50%.
      >
      > Right before I go to bed at night, I strap together 4 modules in
      > parallel and connect them
      > to a Powerlab 6 and start a 40A discharge into the source batteries
      > with a target voltage
      > of 2.5V -- this process bleeds off about 400Ah of energy (at 3V) which
      > at 40A should take
      > about 10 hours (in reality, since the batteries actually contain more
      > energy than they are
      > spec'd to, it takes about 10:30-10:50). In this way, I'm using my time
      > very efficiently,
      > with no idle time for the chargers with nothing going on. The
      > batteries are sitting at
      > about 2.7V when I get up in the morning after this discharge due to
      > the voltage recovery.
      >
      > My plan is to process all batteries using this individual
      > charge/parallel discharge
      > method, and when all are done, do another discharge cycle to 2.5V on
      > each battery module
      > individually, making sure the batteries are all bottom-balanced to the
      > same voltage before
      > assembling them to a pack in the car.
      >
      > So far I've been very impressed with the Powerlab 6's and the CALB
      > 100Ah modules, which
      > have been remarkably consistent.
      >
      > I really can't wait to get everything back in the car and take a test
      > drive!
      >
      > -Tom
      >
      > On 10/25/2012 3:36 PM, Wade Perry wrote:
      > > Hi Geo-
      > > I noticed! But didn't have time to look into what you said.
      > > I'm assuming you'd need a set of monitoring leads for each cell, but how
      > > does it take more power from one cell and less from another?
      > > Wade
      > >
      > > On Thu, Oct 25, 2012 at 12:29 PM, geo_homsy2 <geo.homsy@...
      > <mailto:geo.homsy%40gmail.com>> wrote:
      > >
      > >> **
      > >>
      > >>
      > >> Tom-
      > >>
      > >> two things. I've mentioned it before here, but maybe no one
      > noticed: The
      > >> Powerlab can perfectly well balance several cells during discharge. You
      > >> have to install the windows utility and alter your profile to
      > include the
      > >> "balance while discharging" check box.
      > >>
      > >> The powerlab will indeed stop regenerative discharging when it sees the
      > >> "source" battery (i.e. not the target battery) go above a certain
      > voltage.
      > >> This voltage is also configurable with the utility program. It may
      > also be
      > >> configurable from the front panel -- I don't remember.
      > >>
      > >> //Geo
      > >>
      > >>
      > >> --- In solectria_ev@yahoogroups.com
      > <mailto:solectria_ev%40yahoogroups.com>, Tom Hudson <tdhudson@...> wrote:
      > >>> Thanks for the info, Wade.
      > >>>
      > >>> Well, I'm finally starting to prep my CALB 100Ah pack for my '97
      > Force.
      > >> Had the batteries
      > >>> for several weeks, but have been doing a lot of traveling and haven't
      > >> had a window
      > >>> sufficient to bottom-balance my entire pack at one go. Just got back
      > >> from (hopefully) my
      > >>> last trip and set up a couple of new group 24 SLA's wired in parallel
      > >> for a power supply
      > >>> for my two Powerlab 6's and am in the process of getting the CALBs all
      > >> balanced.
      > >>> Batteries 3 and 4 are on there now (got a ways to go).
      > >>>
      > >>> I was wondering what I was going to see as far as excess power going
      > >> back into the supply
      > >>> batteries when I do the discharge phase -- I mean, since I'm only
      > >> putting ~50Ah (@3V) , or
      > >>> 150Wh into each battery to initially top them off, but pulling out
      > more
      > >> Wh to bring them
      > >>> down to the ~2.5V and trying to stuff that back into the supply
      > >> batteries, I was worried
      > >>> that it may cause the Powerlabs to stop the discharge prematurely,
      > since
      > >> the supply
      > >>> batteries might get fully charged. Mike Rydjord indicated that he had
      > >> this issue, but it
      > >>> sounds like you didn't. Interesting. We'll see what happens here.
      > >>>
      > >>> I'm really excited to get this car back up and running again on the
      > >> CALBs.
      > >>> -Tom
      > >>>
      > >>>
      > >>> On 10/9/2012 10:38 PM, Wade Perry wrote:
      > >>>> Hi Charles-
      > >>>> I'm using a pretty cool tool, borrowed from my friend Robin. Like I
      > >> said
      > >>>> earlier in this thread:
      > >>>>
      > >>>> My fourth-last pair is being balanced "on the bench" as I type this.
      > >> By a
      > >>>> pair of Revolectrix Powerlab 6s. Using a 2S2P arrangement of 4 gel
      > >> cells
      > >>>> as a nominal 24v DC power source for the PL6s. One full cycle- charge
      > >> to
      > >>>> the top and discharge all the way to the bottom (regenerative
      > discharge
      > >>>> back into the gels). 2.0v cutoff. Cells spring back to around 2.92 or
      > >> so.
      > >>>> Noting the capacity of each cell. I may bring them all down a bit
      > >> further
      > >>>> to balance them evenly a bit lower down.
      > >>>>
      > >>>> The Powerlab 6
      > http://www.revolectrix.com/pl6_description_tab.htm(PL6) is
      > >>>> targeted to the remote-controlled plane/helicopter/boat industry (or
      > >> "RC").
      > >>>> Which is actually a big business (unlike the EV industry so far). So
      > >> this
      > >>>> gear has really matured because of its economy of scale. With the PL6
      > >> you
      > >>>> can use any DC power source between 10 (8?) and 32 Volts DC. So what
      > >> these
      > >>>> RC guys do is pack up all their gear on a Saturday morning, including
      > >> some
      > >>>> fully charged large capacity deep cycle batteries, and head to the RC
      > >>>> airstrip to fly their stuff. They use the PL6 or a device like it to
      > >> hook
      > >>>> up to their DC battery bank to draw power and recharge their tiny
      > Li-Po
      > >>>> packs they put into their helicopters. The PL6 is very programmable,
      > >> you
      > >>>> can hook it up to a windows computer for control and programming and
      > >>>> generating cool graphs too. You can do full discharges, full charges,
      > >> full
      > >>>> cycles, even multiple cycles, and graph the whole thing. You set what
      > >> the
      > >>>> "fully charged" voltage is at the top and what the cutoff voltage is
      > >> at the
      > >>>> bottom. Then you set it running and walk away. It takes perhaps 2 1/2
      > >>>> hours in my case to run one cycle. It's very precise and does
      > Constant
      > >>>> Current Constant Voltage charging, meaning it charges at full power
      > >>>> "Constant Current" (~40A is the max for the PL6) until it reaches the
      > >>>> charge voltage, in this case 3.65v, then it gradually decreases the
      > >> current
      > >>>> while maintaining the voltage precisely at 3.65volts. It does
      > this very
      > >>>> well, I've watched it more than a few times. When the current
      > decreases
      > >>>> down to say 1 amp (this part is also adjustable but I'm fuzzy on the
      > >>>> details) it cuts off and the charge is complete. I used 4 of the gel
      > >> cells
      > >>>> from my car's previous pack ("yes, this used to be a lead-acid
      > battery
      > >>>> powered car", he said modestly) as a power source: 2S2P = 2 Serial, 2
      > >>>> Parallel. So the 4 gels together form a 24 volt pack that I can
      > charge
      > >> 1/2
      > >>>> at a time with a standard 12 volt car battery charger when necessary.
      > >> Even
      > >>>> while the PL6 is doing its thing.
      > >>>> After charging, the PL6 sits for a minute, and begins the discharge.
      > >> It's
      > >>>> actually a REGENERATIVE discharge. Very cool because the energy
      > the PL6
      > >>>> takes from the CALBs it puts back into the "source" pack. (sounds
      > >> familiar
      > >>>> don't it- This is one of the cool reasons why I wanted to own a
      > >> Solectria
      > >>>> in the first place) The CALBs come at ~50% S.O.C. (state of charge,
      > >> trying
      > >>>> to maintain coolness here even though I don't really know what I'm
      > >> talking
      > >>>> about), get charged up to full by taking energy from the source pack,
      > >> then
      > >>>> discharged down to empty by putting energy back into the source
      > pack. I
      > >>>> thought for sure I'd have extra energy because the CALBs are
      > giving me
      > >>>> electricity manufactured in China, shipped across the ocean and
      > >> imported,
      > >>>> then the cells are leaving the process empty, having contributed all
      > >> their
      > >>>> power to the source pack. ("All" is of course relative, it can indeed
      > >> go
      > >>>> lower and it will go lower if asked to, but according to spec it's
      > >> close
      > >>>> enough to fully discharged when the PL6 is done with it.) But I don't
      > >> seem
      > >>>> to end up with extra energy, I guess there's enough losses in the
      > >>>> back-and-forth (the PL6 has a fan, after all) and in the resistance?
      > >> of the
      > >>>> Lead Acid batteries, that I do need to periodically charge the Pb
      > >> pack. I
      > >>>> have two 12v car battery chargers on a timer and I just let that run
      > >> for an
      > >>>> hour or so during the charging phase of the full cycle, to keep
      > the Pb
      > >>>> voltage up. You want the source pack to stay somewhere in the middle,
      > >> not
      > >>>> fully charged, because you want room for the regenerative
      > discharge to
      > >> get
      > >>>> stored. Probably not being charged up isn't great for the gels... But
      > >> at
      > >>>> least they're being useful!
      > >>>> The PL6s can be connected together and run as a set- I'm running two,
      > >> so I
      > >>>> can cycle two cells at a time. The one that finished the charge first
      > >>>> waits for the 2nd one before it begins the "cool down period" of one
      > >>>> minute, then they start down again. For 56 cells that means I have to
      > >> do
      > >>>> this 28 times. I only have one more pair left to do, and I've already
      > >>>> re-done my lowest pair...
      > >>>> I'd said I was using
      > >>>> 2.0v cutoff. Cells spring back to around 2.92 or so.
      > >>>> Which was true until yesterday? I dunno, it's a blur. Perhaps it
      > >>>> shouldn't be a blur when you're balancing your expensive batteries...
      > >>>> But I changed it recently because I wanted the bottom-balanced
      > resting
      > >>>> voltage to be lower than 2.92- I'd messed around with a resistor
      > >> trying to
      > >>>> bring it down that last bit and the resistor got HOT man hot. :) I'm
      > >> new
      > >>>> at this and learning tons.
      > >>>> So I changed the settings to a CCCV discharge also, with target
      > voltage
      > >>>> 2.5v.
      > >>>> So instead of just discharging at constant current of ~40A until the
      > >>>> voltage drops to 2.0v and then shutting off suddenly (and when the
      > >> load is
      > >>>> removed the voltage on the CALB springs back up quite quickly,
      > >> eventually
      > >>>> resting at ~2.92), for the last few batches I've had it discharge at
      > >>>> constant current until the voltage falls to 2.5v, then the discharge
      > >>>> current drops off gradually while holding the voltage down to 2.5v.
      > >>>> Eventually the discharge current required to hold the cell's
      > voltage at
      > >>>> 2.5v is very small (details), and the PL6 stops. The resulting spring
      > >> back
      > >>>> in voltage is also smaller, and the cells are coming back to rest
      > >> at... I
      > >>>> dunno that was last night and I haven't looked at them yet but I'm
      > >> hoping
      > >>>> somewhere around 2.60, where I'll bottom-balance the whole pack as
      > >>>> precisely as I can- holding a resistor on a cell for a second or so,
      > >> then
      > >>>> leaving it and measuring the next cell, etc.
      > >>>> So I'm testing capacity in the sense that the PL6s measure how many
      > >> Ahr was
      > >>>> put into the cell during the charge phase, and how many Ahr were
      > taken
      > >> out
      > >>>> of the cell during the discharge phase.
      > >>>> I think it's safe and I'm not stressed letting the PL6s run in my
      > >> basement
      > >>>> and going to bed.
      > >>>> Wade.
      > >>>>
      > >>>>
      > >>>> On Tue, Oct 9, 2012 at 12:21 AM, Charles Bliss <cbliss@...> wrote:
      > >>>>
      > >>>>> **
      > >>>>>
      > >>>>>
      > >>>>> How are you testing the capacity without risking cell damage?
      > >>>>> I have yet to determine what is a conservative / safe range for
      > my 93
      > >>>>> Solectria Hatchback.
      > >>>>> I installed 46 Thundersky 100ah. I keep them charged and balanced.
      > >>>>>
      > >>>>>
      > >>>>> On 10/8/2012 10:26 PM, Wade Perry wrote:
      > >>>>>> Thanks Bouty, I certainly hope so.
      > >>>>>> My lowest cell so far is 61.743 Ahr. Highest is 64.208.
      > >>>>>> Or ~3% to ~7% above rated capacity.
      > >>>>>> So it appears for these smaller CALB cells the "overrating"
      > factor is
      > >>>>> also
      > >>>>>> smaller.
      > >>>>>>
      > >>>>>> Wade
      > >>>>>>
      > >>>>>
      > >>>> [Non-text portions of this message have been removed]
      > >>>>
      > >>>>
      > >>>>
      > >>>> ------------------------------------
      > >>>>
      > >>>> Yahoo! Groups Links
      > >>>>
      > >>>>
      > >>>>
      > >>>>
      > >>>>
      > >>>>
      > >>> --
      > >>> Thomas Hudson
      > >>> http://portev.org -- Electric Vehicles, Solar Power & More
      > >>> http://klanky.com -- Animation Projects
      > >>>
      > >>
      > >>
      > >
      > > [Non-text portions of this message have been removed]
      > >
      > >
      > >
      > > ------------------------------------
      > >
      > > Yahoo! Groups Links
      > >
      > >
      > >
      > >
      > >
      > >
      >
      > --
      > Thomas Hudson
      > http://portev.org -- Electric Vehicles, Solar Power & More
      > http://klanky.com -- Animation Projects
      >
      >



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