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Old May 14, 2012, 06:43 AM
Southern Pride
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Haralson County GA. USA
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Originally Posted by BVH View Post
If I remember correctly, my PL8 begins limiting output when it reaches 325 - 350 Watts or so when using my Iota 12V, 55 Amp supply. Low voltage is the problem, not the Iota's Amp capacity. The Iota is working at 14.4V or so when maxed out.
How long ago was that ? Back when the PowerLab 8s first became available and a buch of users were rying different power supplies with it there were many power supplies which had issues. It was found that many had very poor regulation with the PL8 due to the way that it changes the load very fast and often. Some added large Caps. to smooth out the ripples,some went to other power supplies and FMA modified the firmware to help out. Those of us using server power supplies did not have any power supply issues that I am aware of.

On line power calc.

http://www.revolectrix.com/Calculators_main.htm

Charles
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Old May 16, 2012, 07:57 PM
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MPA board

Ive just purchased a MPA board with the fly leads and have soldered EC5 connectors onto the leads..

When using the MPA board to charge my 6S lipos the IR reading is really high (e.g. 24ohms with 4packs)... There is nothing wrong with the packs as i get a correct reading if i charge them using my old parallel charge/balance leads or charge the pack on its own..

Should I be worried about this high reading on the MPA board? Could this cause issues if its giving false high readings on cell 6?
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Old May 16, 2012, 08:21 PM
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Originally Posted by Geffect View Post
Ive just purchased a MPA board with the fly leads and have soldered EC5 connectors onto the leads..

When using the MPA board to charge my 6S lipos the IR reading is really high (e.g. 24ohms with 4packs)... There is nothing wrong with the packs as i get a correct reading if i charge them using my old parallel charge/balance leads or charge the pack on its own..

Should I be worried about this high reading on the MPA board? Could this cause issues if its giving false high readings on cell 6?
What charger are you using?
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Old May 17, 2012, 05:52 AM
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Originally Posted by gregor99 View Post
what charger are you using?
pl8.
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Old May 17, 2012, 10:08 AM
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Originally Posted by Geffect View Post
pl8.
If you are not already on firmware 3.31, upgade and report your results.
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Old May 18, 2012, 01:02 PM
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When parallel charging with the MPA, I noticed that the PL6 doesn't give an error if the number of batteries connected to the MPA does not match the number of batteries I select in the PL6. For example, I can connect 2 batteries to the MPA and the charge will charge them even if I select No to parallel charging. Is this a safety issue? I'm new to parallel charging so am trying to understand the dos and don'ts with the MPA. Thanks.
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Old May 18, 2012, 01:09 PM
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Well, it could be a safety issue if you erred on the high side, but as you are entering "no," you are erring on the low side, so it is fine.

When you enter the number of batteries, the charger simply accounts for that number in fixing amperage.

So, if you enter "no," it will treat the entire board as "one" battery.

Now, here is where you could get into trouble: fitting only one battery, answering with a high multiplier, like 6, which I suppose would cause the current to get too high-just a guess.
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Old May 18, 2012, 01:34 PM
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I would have assumed that too for all charges except Cellpros. I'm assuming that there is some safety feature built into Cellpro chargers that would detect any anomalies caused by a very high charge rate and would therefore adjust automatically. I have no plans to misuse the charger to check this but I'm simply curious to the effects of what would happen if the wrong multiplier is used.
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Old May 18, 2012, 01:44 PM
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We'll have to wait for Tim or Charles to answer that query!
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Old May 18, 2012, 02:27 PM
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Originally Posted by JohnathanSwift View Post
We'll have to wait for Tim or Charles to answer that query!
There's no way for the PL 6 or 8 to know that you "lied" to it about the number of batteries.

When charging in parallel, six 1000mAH cells in parallel behave like a single 6000mAHr cell.
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Old May 18, 2012, 02:35 PM
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Agreed, but that does not (1) feed the bulldog, nor (2) answer this guy's question.
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Old May 18, 2012, 03:02 PM
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Quote:
Originally Posted by falcon7a View Post
I would have assumed that too for all charges except Cellpros. I'm assuming that there is some safety feature built into Cellpro chargers that would detect any anomalies caused by a very high charge rate and would therefore adjust automatically. I have no plans to misuse the charger to check this but I'm simply curious to the effects of what would happen if the wrong multiplier is used.
Hi:

If you tell the PL you are charing multiple packs in parallel, but you only have one pack connected, there is no way for the PL to determine that there is only one pack connected. It will charge the pack at, e.g., n * Preset charge rate, where n = the number of P you entered prior to starting the charge. There is no way for the PL to tell the difference between 1P and 2P or 6P if you do not enter the number correctly. It's really not that different from the fact that the PL can not distinguish between chemistries. That's why we have the VERIFY CHEMISTRY screen pop up before the charge process begins. Guess we could also offer a verify "P" count, but pretty soon it's going to take 20 button presses to start a charge which is not a good thing.

Only way around this would be to specify 1P always and select one of the AUTO charge rates.

Tim Marks
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Old May 18, 2012, 03:15 PM
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Makes sense, thank you. I will be careful and will ensure that I select the right P.

If I don't want to use the Auto charge rate, should I simply manually set the maximum charge that the smallest battery connected to the MPA can take? So if I like to charge at 3C and I have 2 2,000mah and 2 5,000mah connected (same cell count), I should select a manual charge rate of 6amps (3C x 2,000mah)?
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Old May 18, 2012, 03:20 PM
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Hm.
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Old May 18, 2012, 05:47 PM
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Originally Posted by falcon7a View Post
if I like to charge at 3C and I have 2 2,000mah and 2 5,000mah connected (same cell count), I should select a manual charge rate of 6amps (3C x 2,000mah)?
If you have two 2000 and two 5000 packs all connected in parallel, you effectively have a 14000 pack. To charge this combination at 1c would 14 amps, to charge at 3c would be 42 amps. As to how the current would be divided between packs is dependant on the IR and condition of the pack. In general larger packs have lower IR and will experience current proportional to thier size, and relative to the other packs in parallel. For instance the 5000 packs should experience a little more than twice the current that the 2000 packs are experiencing.

As there is no intelligent control over the current distribution of packs in parallel, the actual results may vary depending the specific packs connected. This one of the reasons for the guide line to parallel charge packs of similar size. Though not a requirement it can produce better results. When in doubt use a high quality cell checker to check the packs after the charge. As soon as the charge cycle has completed, disconnect the packs from the MPA and check thier voltage. If all packs are within acceptable norms, you are fine.
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