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Old Nov 25, 2012, 04:43 AM
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If anyone is interested I have for sale 3x brand new Quanum v2 2.4Ghz voltage telemetry Current & Heat Sensor.. These were brought for a project, but was never started.
Pm me if anyone is interested.
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Old Nov 25, 2012, 03:37 PM
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Bill and Bill

Wouldn't this be better discussed on another thread? It's really not to do with the Quanum.

thanks, John
Agreed.
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Old Dec 13, 2012, 06:07 AM
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I have been reading through the whole thread and please point me to the topic if i've missed it and it had already been discussed.
I have noticed that when I connected a fully charged 2200mah 4 cell battery while bench testing the quanum and set the readout ro show remaining capacity percentage, I initially got 99 to 100%. So after running the edf motor for about a minute and a half, I still get 70% remaining capacity. Now the individual cell readings indicate around 3.75-3.8 volts.
Then I disconnected the battery and tested it in my watt meter. It shows around 50% remaining capacity. I then again connected the same battery to the transmitter and to my surprise, the remaining capacity appearing on the screen got back to 99% even though the battery is now half charged.
It appears that the capacity indicator bases its initial readings on the assumption that the battery is fully charged. Or maybe I have a faulty transmitter?
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Old Dec 13, 2012, 06:16 AM
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So after running the edf motor for about a minute and a half, I still get 70% remaining capacity. Now the individual cell readings indicate around 3.75-3.8 volts.
...
I then again connected the same battery to the transmitter and to my surprise, the remaining capacity appearing on the screen got back to 99%
What are the cell voltages showing when you reconnect to the TX?
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Old Dec 13, 2012, 06:17 AM
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They're around 3.75-3.8 volts
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Old Dec 13, 2012, 06:20 AM
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Are you sure? You'd normally expect the cell voltages to recover once the load is removed.
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Old Dec 13, 2012, 06:24 AM
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Yes, but not at 99% remaining capacity. This unit would be useful to me if set to with the individual voltage alarms and not on the capacity indicator alarm. Or maybe my tx is faulty.
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Old Dec 13, 2012, 06:59 AM
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Capacity alarm can only be based on what pack size you have told it and the mAh it has measured going out. Looks like the latter is lost when you unplug the pack - this is surely fair enough, as normally you'd be doing that to replace with a new one (not the same one).

Voltage alarms are simpler (that's why I use them).
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Old Dec 13, 2012, 08:33 AM
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This unit, apparently, assumes you are using a fully charged battery, and determines % available from mah used. Measuring the voltage, and using that as % of charge, is only an estimate, so not very useful. The documentation isn't clear on this point, but the voltage readings seem to only be used for display, and to trigger the voltage alarms.
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Old Dec 13, 2012, 08:51 AM
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Voltage measurement of cells that aren't under load is generally a pretty good way to get state of charge. This applies to LiPo, Nicd, Nimh, Lead/acid, etc. So IMO it would be a nice feature to have it derive an estimated % charge from the cell voltages when first connected, and apply that to the stated pack size to get starting mAh (rather than assuming 100%).
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Old Dec 13, 2012, 09:36 AM
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I wonder why the battery capacity is not measured in real time like that of battery cell voltage meters and cell balancers.
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Old Dec 13, 2012, 01:10 PM
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Battery capacity of a lithium battery cannot be directly measured using voltage readings. The voltage varies widely with load, temperature, and internal condition of the battery, so reading a new battery at 50% state of charge can give a very different value than one that has been used 100 times. Also, two batteries that have been used 100 times can give different readings if one was used at relatively low currents, and the other near its C rating. Voltage readings give only a rough estimate.
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Old Dec 13, 2012, 01:53 PM
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At least I wish my quanum unit would measure the no load capacity even if it is not so accurate and not just presume its 99 to 100% full. I just connected the same battery now. The readings show 99% capacity at 3.81 volts average per cell.

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Old Dec 13, 2012, 01:54 PM
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Battery capacity of a lithium battery cannot be directly measured using voltage readings. The voltage varies widely with load, temperature, and internal condition of the battery, so reading a new battery at 50% state of charge can give a very different value than one that has been used 100 times. Also, two batteries that have been used 100 times can give different readings if one was used at relatively low currents, and the other near its C rating. Voltage readings give only a rough estimate.
I disagree. Measuring resting voltage as suggested (not under load) gives a pretty good estimate of percentage charge remaining. What varies based on age (and nature of usage) is the capacity.

Two packs straight off the same charger will show the same voltage (100% charge), regardless of age. Take 10 amps for 5 minutes out of both of them and they may then show different voltages. But that's because one is now further discharged (in percentage terms) than the other.
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Old Dec 13, 2012, 03:33 PM
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At least I wish my quanum unit would measure the no load capacity even if it is not so accurate and not just presume its 99 to 100% full. I just connected the same battery now. The readings show 99% capacity at 3.81 volts average per cell.

It uses current measurement for calculating capacity (mAh). :
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