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Old Jul 02, 2009, 02:04 AM
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Question
charge through balancer without main wires connected?

Can the Hyperion EOS 0403i charge through the balancer without the main wires connected, or is it necessary to connect both?
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Old Jul 02, 2009, 03:10 AM
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Christchurch, New Zealand
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It's necessary to connect both. Most more recent charges only charge through the main wires because charging through the balance taps is MUCH less accurate.
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Old Jul 02, 2009, 04:19 AM
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Balance tabs usually use connectors rated at 1A Max. Better be careflu about those "parallel charger", some of them charge through the balance tab with a 2~5A current, it an overkill.
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Old Jul 02, 2009, 09:49 AM
Are there crawfish in heaven??
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Quote:
Originally Posted by Andrew McGregor
It's necessary to connect both. Most more recent charges only charge through the main wires because charging through the balance taps is MUCH less accurate.
Why is charging through the balance plug "much less accurate". What data do you have to support this? Not all chargers require the use of the discharge leads to charge a pack. My understanding is that the limiting factor for charging through the balance leads is their lower current handling capacity. This is clearly stated in the manual for my Cellpro 10S. Any charge rate over 4 amps and the discharge leads must also be connected. Just curious.
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Old Jul 02, 2009, 10:15 AM
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It's less accurate because the resistance on the balance leads is an "unknown" and because you're passing a moderate current over it the voltage drop across the wire is also unknown hence the true voltage of the pack cells cannot be reliably determined during the charge process.

By charging via the main leads and sensing the voltage off the taps it's a lot more reliable because the current required to 'sense' voltage is insignificant at the resistances encountered with the balance leads.

For a explanation on the theory, look up "4 wire kelvin leads/tests".

Paul.
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Old Jul 02, 2009, 10:26 AM
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To add to Paul's comment - This condition is exacerbated as charge current increases (in accordance with Ohm's law). At low currents (a few amps) it's not a big deal and will simply take longer to complete charging as the balancer is in effect 'fighting itself' throughout the charge cycle.

This issue was first pointed out when Hyperion released their LBA6 balancer. It prompted many (myself included) to modify their balancers to provide charge current via the main discharge leads. Hyperion has since changed the design of their LBA10 to have this as a standard feature.

Bottom line, if your charger has provision to be able to charge via the main discharge connector - use it if you want the fastest and most accurate charge.

Background on LBA6 mod here.

Mark
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Old Jul 02, 2009, 10:28 AM
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In y experience the FMA Cell Pro chargers do a betterr job charging using only the balancing leads than most chargers which only use the balancing leads however IMO it is best to limit charge rates to 3 amps. or less even with the Cell Pros and then only using thier balancing leads which are better than a lot of the others out there.

Everyone should try and remember that a lot of statements tha are made are in general.

In general if you use any of the run of the mill balancing leads and balancing leads only charger then 1A should be about max. charge rate.


http://www.rcgroups.com/forums/showp...&postcount=189



http://www.rcgroups.com/forums/showp...&postcount=64u


Try and remember that some balancing chargers sucha s the Cell Pro 4 that only charge trought the balancing leads do in fact monitor each cell all of the time and adjust bleeding current to maintaing balance.

Some mukti channel chargers such as the DN Power are really 4 seprate chargers in a single case so each cell is charged with it's own charger.

Some balancing chargers which use the balancing leads only in fact only charge one cell at a time and switch from one cell to the next,then next,etc.


Bottom line balancing leads used on most LiPolys were not designed to carry high current. It woud be foolish to use servo leads as the main power leads from the battery to the ESC even on a 6 oz. park flyer.

Charles
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Old Jul 02, 2009, 04:54 PM
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Quote:
Originally Posted by jcg1112
Why is charging through the balance plug "much less accurate". What data do you have to support this? Not all chargers require the use of the discharge leads to charge a pack. My understanding is that the limiting factor for charging through the balance leads is their lower current handling capacity. This is clearly stated in the manual for my Cellpro 10S. Any charge rate over 4 amps and the discharge leads must also be connected. Just curious.
Just exactly as the next poster said: you're trying to measure something (cell voltage loaded with charge current) with the complication of an unknown resistance in the circuit, and without the extra data from having more connection points, you can't get a reliable answer. It's a standard bit of electrical measurement technique, you don't need data to know this because it comes out of the math describing the circuit.

Of course, that doesn't say you can't charge through the balance leads, it's just that you will lose accuracy and then risk unbalancing the pack. You might notice that if you charge that way and then leave the balancer on until it finishes that it will probably take longer to finish balancing (on a 3s or more pack). That's the balancer sorting out the slight imbalance that should have resulted from the charging method; the middle cells will be just a fraction lower in voltage. The real risk is that the outer cells might have slightly overcharged, which will slowly damage them.
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Old Jul 03, 2009, 02:08 AM
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I have no axe to grind one way or the other. But I would point out that the voltage-measurement inaccuracy inherent in the use of balance leads only, due to the resistance of the leads, becomes less as the charge progresses towards its conclusion. This is because the amps reduce to a very low value during the final phase of the charge, so the voltage loss in the leads is correspondingly less.
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Old Jul 03, 2009, 02:23 AM
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True. And charger firmware can also shut off the current briefly to get a measurement to improve the accuracy.

Still, it's now standard to put the charge current through the main leads, and works well. It's the simpler solution, which implies it is probably easier to get right.
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Old Jul 03, 2009, 10:31 AM
Are there crawfish in heaven??
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I follow the electrical reasoning and theory why there may be some inaccuracies charging thru the balancing leads. But, as Charles said, this is a general statement. The Cellpro chargers monitor each cell individually and bleed off current as needed to maintain balance. In the 1 1/2 years I've had my 4s and since I bought my 10S at the beginning of this year, I've not had any issues with any cells in any of my packs going out of balance by charging thru the balancing lead. I would be careful about implying that charging thru the main leads is done because it is probably easier to get right. Obviously it does get it right, but due to the design of the Cellpro chargers they also get it right. As such, I'll keep using my 4S along with my 10S.
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Old Jul 03, 2009, 08:04 PM
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Ok, so the Cellpros work... that's great. I didn't say it was impossible, it isn't, it's just harder. So they did the hard thing and succeeded.

The point about balance taps having a fairly small current rating is also true, which matters with packs rated for high-C charging.

In any case, the original poster's Hyperion, like all recent Hyperion chargers, will refuse to start if all the wires are not connected.
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Old Jul 04, 2009, 05:50 AM
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Quote:
Originally Posted by everydayflyer

Try and remember that some balancing chargers sucha s the Cell Pro 4 that only charge trought the balancing leads do in fact monitor each cell all of the time and adjust bleeding current to maintaing balance.

Charles
Not to add to the confusion, but to be technically correct, it's my understanding that the FMA Cellpro 4S and Multi4 have no current bleeding capability whatsoever. Rather, they achieve balancing by adding additional charging current to the lower voltage cells rather than bleeding current from the higher voltage cells. Thus, they work in reverse of the way a typical bleed balancer works.
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Old Jul 04, 2009, 09:15 AM
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Quote:
In any case, the original poster's Hyperion, like all recent Hyperion chargers, will refuse to start if all the wires are not connected.
Not entirely accurate. Hyperion chargers and most others will charge through the power leads only. Cell Pros must have balancing leads connected.
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Old Jul 04, 2009, 10:28 PM
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Quote:
Originally Posted by everydayflyer
Not entirely accurate. Hyperion chargers and most others will charge through the power leads only. Cell Pros must have balancing leads connected.
That's not entirely accurate either. In the case of the Cellpro Multi4, it will charge a 1s-2s Lithium battery unbalanced and it will charge a 1s-5s A123 pack unbalanced. Thus, not all Cellpros require balancing leads connected.
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