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Old Oct 15, 2011, 07:23 AM
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Due to I^2 losses you might get marginally better efficiency from both the PS and the charger at 30V than at 25V but I agree with Charles that it most likely will not make any noticeable difference in use.
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Old Oct 15, 2011, 10:59 AM
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Cheers guys!
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Old Oct 15, 2011, 01:30 PM
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Calibration with reference voltage possible?

Hi Junsi,

I have a question concerning the calibration. Normally, one is supposed to attach a 10s pack and to compare the voltage of the several cells, checked with a DMM, to th ereadings of the charger and adjust until they match.

Well, my DMMs ar not very accurate. So, what about using a reference voltage like this?
What I intend to do is to make a little adapter that allows me to remove one cell from the 10s pack and to replace it with the 5.000V circuit. The iCharger will now "see" one cell of the pack having 5.000V. Is this correct? Then I adjust the reading on the iCharger for that cell to 5.000V as well. I continue this for every cell, until every cell has been replaced once and the respective reading has been calibrated.
Will the balance port withstand a 5V voltage, or will something be damaged this way?

Cheers,

Julian
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Old Oct 15, 2011, 01:40 PM
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Julez, "other voltages available are: ..."

Quote:
Originally Posted by Patriek View Post
Okay so I'm using a iCharger 306B and I'm stepping up from a MeanWell SP-750-24 PSU to this 1000W PSU.
Don't play soft - take 2000W version
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Old Oct 15, 2011, 03:11 PM
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I know, but I think the higher the voltage, the smaller the respective error is.
And 5V is such a nice round number as well
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Old Oct 15, 2011, 06:47 PM
jrb
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IMO you should select the voltage based on your meter's resolution; here's a couple threads where I posted some info about refernces and resolution:

http://www.rcgroups.com/forums/showthread.php?t=1453650

http://www.rcgroups.com/forums/showthread.php?t=1448442
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Old Oct 16, 2011, 10:41 AM
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Well, I don`t plan to calibrate my DMMs (although I could do it as well), but my Chargers.
I just checked with a BEC having 4.92V according to My DMM, and the iChager read just that. But when I connected a 5.30V BEC, it read 4.95V. So I assume that the iCharger stops reading correctly at close to 5V or so, thus making 4.5V a good reference voltage.
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Old Oct 16, 2011, 03:22 PM
BGR
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Is +/- .05 volts really that critical? Will you notice that your battery lasted a week or a month longer if the charger was perfect? Did the battery die sooner than another due to manufacturing tollerances? Does your Model do exactly the same thing to the battery every time you run it?

Are we getting too critical?
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Old Oct 16, 2011, 03:52 PM
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Quote:
Is +/- .05 volts really that critical?
Well that could mean up to 0.1 volt difference which is approx. 10% so IMO yes that is way to much for a balancing circuit to be out of calibration.

I consider + / - 0.015 close enough which is at most 3% and I am refering to the finished charge state of LiPolys not balancer's calibration which should be much closer since the LiPoly cells will vary enough on thier own over time unless they are very good cells and well managed.

Charles
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Old Oct 16, 2011, 04:11 PM
BGR
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Quote:
Originally Posted by everydayflyer View Post
Well that could mean up to 0.1 volt difference which is approx. 10% so IMO yes that is way to much for a balancing circuit to be out of calibration.

I consider + / - 0.015 close enough which is at most 3% and I am refering to the finished charge state of LiPolys not balancer's calibration which should be much closer since the LiPoly cells will vary enough on thier own over time unless they are very good cells and well managed.

Charles
Yea I did not consider the percentage of full voltage that .05v represents.

On another note. I wish that the ICharger had an option to automatically lower the charge rate at a chosen voltage before going into the CV phase. I have found that this is much better for charging my little 1s UM batteries. The voltage climbs very fast on them and as a result the charger goes into CV too soon and the charge cycle takes longer than it should.
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Old Oct 16, 2011, 04:23 PM
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Even if a DVM is not 100% accurate, it will still read the same for all cells. All cell voltages will be equally calibrated, and that's the important part.
Junsi mentioned some time ago an upper limit of 4.8V within the firmware. Don't know if this still applies.

Fred
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Old Oct 16, 2011, 04:26 PM
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Originally Posted by flarssen View Post
Junsi mentioned some time ago an upper limit of 4.8V within the firmware. Don't know if this still applies.

Fred
If you are talking about 4.8v in a cell of a LiPo I would think it would be junk.
That is too high.
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Old Oct 16, 2011, 04:49 PM
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http://www.rcgroups.com/forums/showp...&postcount=516
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Old Oct 16, 2011, 05:09 PM
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Quote:
The voltage climbs very fast on them and as a result the charger goes into CV too soon and the charge cycle takes longer than it should.
Have you tried adding balancing leads? Yes I know a 1S in theory does not require balancing leads however most balancing chargers really do need both the main leads and balancing leads on these 1S LiPolys.
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Old Oct 16, 2011, 06:18 PM
BGR
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Quote:
Originally Posted by everydayflyer View Post
Have you tried adding balancing leads? Yes I know a 1S in theory does not require balancing leads however most balancing chargers really do need both the main leads and balancing leads on these 1S LiPolys.
No I have not done that but I am willing to give it a try because although I have developed a work around it is cumbersome. I assume that the negative side of the battery goes to the balance port pin marked -. Since the cells are in parallel where does the + side go, the next pin over?

The voltage on the balance port should be the same as the total voltage on a 1s cell. What does the charger do differently when connected in this way?
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