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Old 01-06-2012, 05:01 PM   #21 (permalink)
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Originally Posted by Formula413 View Post
As a matter of fact I have, I don't own one but I did get to give it a grid charging once, for several hours.
How did you decide on the time to let it charge? I was under the impression a re-balancing trickle charge is quite a bit longer than several hours.

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Old 01-06-2012, 05:19 PM   #22 (permalink)
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Could you just connect them in a paralled cricuit with two sticks in each circuit then use a standard automotive type charger. You would end up with 10 sets of two sticks and they should charge to about the same as a standard lead acid battery. The amperage would be spread out in .1 increments. Might take a while.
Just a guess on my part.

edit: I think I got my math wrong, was trying to figure out a way to use what I already have to do the job. Nominal stick voltage would be about 9 volts?


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Old 01-06-2012, 05:34 PM   #23 (permalink)
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I think nominal stick voltage would be ~7.2. (144 nominal pack voltage /20 sticks).

I'm still at the veeeeerrrrrrry bottom of the learning curve... but I don't think that'd do the trick.
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Old 01-06-2012, 06:50 PM   #24 (permalink)
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Quote:
Originally Posted by MetroMPG View Post
How did you decide on the time to let it charge? I was under the impression a re-balancing trickle charge is quite a bit longer than several hours.
I was told that once the voltage stops increasing, that's when you stop charging, usually around 170 volts.

How managable was the car driving without the battery for an extended period? I have heard that it will not charge the 12 volt battery effectively at idle and you can kill the battery if you're not carefull. I was planning on driving without the battery if/when I refurbish mine, rather than drive the Firebird the whole time.
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Old 01-06-2012, 07:09 PM   #25 (permalink)
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Re: grid charging - I'm a noob about all this. But Mr Smalls says: "Leave it charging your battery (with the battery fan running) for 36 hours or so, and it will top off ALL your cells, restoring state of charge balance." I've also read that you need to wait until pack voltage peaks, then declines before considering it fully balanced.

Quote:
How managable was the car driving without the battery for an extended period?
Re: non-hybrid performance - I could happily drive the car without the hybrid functions forever.

Keep in mind my starting point, though. The non-hybrid performance of the Insight is better than the Firefly I'm used to driving. ~67 hp vs. ~50, similar vehicle weight, though taller gearing in the Insight. Maybe they're about the same.

Quote:
I have heard that it will not charge the 12 volt battery effectively at idle and you can kill the battery if you're not carefull.
If the 12v battery is not being charged by the DC-DC converter, the 12v/battery dashboard idiot light will be on, just like a "regular" car.

I have noticed that often there's a delay after starting the car before the DC-DC converter kicks in (anywhere from a few seconds to a minute or so). And once or twice it has stayed off long enough after a start/restart that I began to wonder if it was going to come back. It always has.

The DC-DC will also not function above a certain engine RPM (~3k+). I'm rarely up there, though, so that's not a concern to me. But if you rev it up once in a while to pass or otherwise accelerate quickly, the dashboard idiot light will come on.

My car's 12v battery was already weak when I got the car though - resting voltage after a few days is in the low 12.x V range. Could just be due to normal aging, or because the car was parked for 5-6 months after the previous owners traded it in. I wouldn't be surprised if it had been flat-lined a few times before I got it.
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Old 01-06-2012, 07:18 PM   #26 (permalink)
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Best of luck.


Just figure I'd give my 2 bits from what I've seen from doing this kind of thing several times myself... and discussions with others.

Although I guess it is a bit late now ... but for future reference of others ... I've done the subpack testing without removing the subpacks ... or disconnecting the orange terminal plates on the two sides ... it has risks , because the connected voltage is higher than with the side connection boards off ... but a set of alligator clips can connect to the + of one side and the - of the other side and do one subpack at a time that way ... has it's risks ... but is a bit faster ... and doesn't have the risk of the PTC strip damage from bending the thin metal.

When you do the testing ... I would suggest the following 4 steps / order:
#1> Do a Initial SoC discharge test of each subpack stick... how many Ah or Wh was each stick charged to initially?

#2> Do a discharge capacity check of each subpack stick from a fully charged state... once fully charged ... how many Ah or Wh will each stick give during a discharge?

#3> Note the subpack internal resistance estimate for each stick ... what is the change in terminal voltage from the resting state to the discharging state at a known amount of amps ... V=IR ... this can be noted during the above discharge capacity test.

#4> Note the estimated self discharge rate of each subpack stick ... fully charge the subpack stick after #2 above ... after a consistent number of days do a 2nd discharge SoC check ... note the difference in SoC Wh or Ah after the number of days compared to the capacity of Wh or Ah from a fully charged state.

Consistency is important ... it is more important that the cells / subpacks be close to matched to each other than being stronger ... similar SoC Ah/Wh is more important than higher Ah/Wh ... similar capacity Ah/Wh is more important than higher capacity Ah/Wh ... similar internal resistance is more important than lower less internal resistance ... similar self discharge rates is more important than lower self discharge rates... in order to compare the results yo get from each battery tested ... it is important the testing method is as consistent as is reasonably possible.

If you start at one subpack ... and proceed systematically ... by the time you finish doing the #2 & #3 testing and fully recharging of the 20th subpack stick ... many hours will have passed ... and you may be ready to start doing the #4 test of the 1st subpack stick.

The main benefit of this kind of subpack level testing is to quantify the condition of the battery pack.

A slow grid charger is a good method of doing occasional maintenance of a out of balanced SoC ... just keep in mind it treats the effect ... it does not fix the root cause of things like different internal resistance ... or different capacity ... or different rates of self discharge.
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Old 01-06-2012, 10:56 PM   #27 (permalink)
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Quote:
Originally Posted by IamIan View Post
I've done the subpack testing without removing the subpacks ... or disconnecting the orange terminal plates on the two sides ... it has risks , because the connected voltage is higher than with the side connection boards off ... but a set of alligator clips can connect to the + of one side and the - of the other side and do one subpack at a time that way ...
More convenient still, I've found, is to get a couple of ring terminals with diameter large enough to accept the bolts that normally connect the sticks in the pack. Undo all the bolts (thus eliminating the risk of current from all the batteries), and use a couple of the metal stand-off pieces (the thick metal "washers") that are in the terminals that are outside connections to screw the ring terminals to each stick to charge it. A cordless drill with a 10 mm socket is a great help here.
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Old 01-07-2012, 05:55 PM   #28 (permalink)
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Quote:
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Best of luck.
Thanks! And thanks for the additional suggestions. One comment and one quick question:

I had another specific suggestion that it may be advantageous to remove the sticks for testing specifically to keep tabs on which cell/s is/are getting particularly hot during charging. Might be a useful data point to have.

But it certainly speeds up the process by leaving everything in place.

Question (pardon my noob-ness):

Quote:
#3>Note the subpack internal resistance estimate for each stick ... what is the change in terminal voltage from the resting state to the discharging state at a known amount of amps ... V=IR ... this can be noted during the above discharge capacity test.
Good idea. But since voltage begins falling as soon as the discharge begins, at what point do I record V to get a best estimate? 1 second after starting to discharge? 10?
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Old 01-07-2012, 06:55 PM   #29 (permalink)
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Subpack testing begins!



Sitting on top of the battery pack case:

Top left: power supply, with additional external cooling fan (added by me), which powers ...

Top right: Super Brain 989 battery dis/charger/tester, also with additional external cooling fan added (duct tape is awesome) by me

Bottom: subpack "11" undergoing its 3rd charging

Out of frame: a box fan, blowing across everything in the pic

A note on cooling fans: additional cooling for the Super Brain is necessary - it apparently goes into current limit on discharge when its heat sink/dissipator gets too warm (~70 F / 21 C ambient). I am using 10 A for discharge, and before adding the extra air flow, I noticed it had automatically halted discharging at one point while its internal fan continued running. It resumed automatically too. I assume it got too hot. At one other point, it reduced discharge current to 7A, but continued going. With the 3 added fans it will indefinitely give all the power she's got, captain.

Impromptu pack analysis workshop

I spent a few very interesting hours at a neighbour's place this afternoon with the pack & dis/charger. When he found out I was planning to analyze the pack, he insisted on being involved, and could he bring a friend? He offered the use of his bright, clean workspace for our "workshop/seminar".

Why not? The more the merrier!

He and his friend - both technically minded - have been avid remote control airplane flyers for years, and one has lots of experience with NiMH chemistry in his planes (before everyone adopted LiPo). Lots of experience with battery charging/cycling, etc. Lots of learning went on in many directions.

A few interesting notes from this afternoon's play time:
  • 11 (out of 20): the number of sticks/subpacks that were able to offer just 65 mAh or less on their initial discharge. They were basically "empty", with less than 1% (65 mAh) of nominal capacity (6500 mAh)
  • The rest of the sticks were scattered randomly from there up to the maximum (outlier) of 2848 mAh (44% of rated capacity). A pretty unbalanced and discharged pack indeed.
  • I have put one of those 11 "empty" subpacks through 3 charge/discharge cycles so far, and its charge capacity has risen to 6825 mAh, according to le Cerveau Super.
I'm recording the results to share of course, and will update again tomorrow.
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Old 01-07-2012, 07:04 PM   #30 (permalink)
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Was there a pattern to the state of charge relative to the location in the series of sticks?
As if they were all in a straight line from positive to negative connection.
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