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Is my charger bad?

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Old 09-08-2003, 02:02 PM
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neal scoggin
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Default Is my charger bad?

I have a Wingo parkflyer. The first 10 or so flights lasted about 10 minutes. (What fun!)LATELY, THOUGH, THEY HAVE DROPPED TO ABOUT 30 SECONDS. This has happened on two different battery packs. I have the small Jeti recharger. I got a Voltmeter off eBay to help me troubleshoot the problem. When the Jeti is attached to my car battery, I read @9.3v. When I select DCA (200m scale) on my Voltmeter, it read @89.5 and varied up and down 3 or 4 units. When I attached my Plane Battery to the charger, the DCAs went to zero. Volts remained at around 9. After detaching my plane battery, I still couldn't get any amperage reading other than zero. I am flummoxed. Do I have a bad charger or two bad battery packs? Something else?
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Old 09-08-2003, 03:42 PM
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Matt Kirsch
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Default RE: Is my charger bad?

What does your car battery measure for voltage? It sounds to me like your car battery is dead.
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Old 09-08-2003, 08:03 PM
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neal scoggin
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Default RE: Is my charger bad?

Car battery's fine. Any other thoughts?
Thanks, Neal
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Old 09-08-2003, 08:23 PM
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Default RE: Is my charger bad?

meter should be set to read dc volts. when attached to car battery,it should read 12 volts dc. if it reads 9 volts either the meter is no good or your car battery is very dead. do not use meter in dca position.set meter to dc volts position and place across the battery that you are trying to charge. turn on charger. voltage on meter should indicate a value slightiy high than the nominal value of the battery.as long as the voltage is greater than the nominal value of your battery the battery will be charging.
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Old 09-09-2003, 07:27 AM
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Matt Kirsch
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Default RE: Is my charger bad?

One thing you do NOT want to do is connect the meter to the + and - terminals of a battery or charger and set it to AMPS mode. You'll burn the meter out. The correct way to connect a meter in AMPS mode is to connect it inline, i.e. to the + terminal on the charger and the + terminal on the battery.

When you measure Volts, you connect to the + and - terminals because you're measuring the potential difference between the two terminals. When you measure Amps, you're measuring current flow, like water through a hose.

My next question is, how does this charger work? Is there a button to press, or is it supposed to be automatic? Are there any indicator lights or a readout? How long were you charging before, and how long are you charging now?

Either the charger is not working at all, or it is "false peaking."
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Old 09-09-2003, 12:38 PM
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neal scoggin
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Default RE: Is my charger bad?

Thanks for the quick replies.

The 9.3v indication was from the Charger output, not my good'n'healthy 12v car battery.

Thanks for the warnings about how not to try to measure Amps- I was thoroughly clueless on that.

Charge times have ranged from 3 hours to overnight w/out luck. One clue is this- the battery packs have not been heating up as I suspect they should.

Battery volts indicate @7.4.

The $4.99 "multi-tester" has a 20-position rotator switch for DCV, ACV, DCA, hFE, Ohms and, I think, capacitance. One of the positions is "OFF". It has a 4 digit readout that comes on when the switch is out of the "off" position.

As the charger output > battery rating, could the ship-board system that stops the motor when voltage is too low be activating itself too early?

To measure Amps do I put the red probe on the power source and the black probe on the draw?

Again, thanks,
Neal
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Old 09-10-2003, 07:56 AM
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Matt Kirsch
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Default RE: Is my charger bad?

As long as you connect the meter leads to the + on the battery and + on the charger, that is, inline, it does not matter which lead is going where. You might get a negative reading, but you can then change the leads. Of course, the - side needs to be connected as you normally would.

I don't think the LVC, low-voltage cutoff, is activating itself too early. 7.4 Volts is pretty close to fully discharged on a 7-cell pack. Fully charged, the pack should read between 9.5 and 10 Volts. The charger is definitely not working.

Your best bet is to call Hobby Lobby and see what they say.
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Old 09-10-2003, 09:29 AM
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Default RE: Is my charger bad?

Willco! Thanks!
Neal
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Old 09-11-2003, 11:13 AM
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Default RE: Is my charger bad?

I opened up the charger, cleaned out a small spider's nest, and recharged all my batteries, each getting 8 hours on the charger.
Then I got scientific.
I named my batteries A, B, & C.
A & C are NiCads, B is NiMH.

------V-------Duration before cut-out---------V (after cut-out)
A----9.6-----------59 sec--------------------8.72
B----8.01-----------.5 sec--------------------7.98
C----9.17----------29 sec--------------------8.54


Does anybody have any thoughts before I buy a new charger?

Thanks again,
Neal
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Old 09-16-2003, 11:25 AM
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Default RE: Is my charger bad?

Neal-

What are the capacities of your battery packs? And what charge current is supposed to be coming out of the charger? Do you have a way to set charge current?

From your description, the charger could be dead, your packs could simply be under-charged, or you could have cooked the packs.

And simply sticking a voltmeter on the battery isn't very useful. It's like testing an automobile battery- it has to be done with a load on the battery to mean anything.

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Old 09-16-2003, 12:23 PM
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Default RE: Is my charger bad?

Packs A & C are 7 Cell 600 AE nicad packs. Pack B is a 7-cell 1000mAh Nimh pack.

My Jeti minicharger 4-7 NC has 3 output options. 50-110, 150-300, and 350-800 mAh. I have the bridge set up for the 350-800 configuration.

Apologies in advance for these dumb questions:
To test the battery voltage with a load, I should do it with the plane's motor running?
To test charger output voltage, I should test it with a battery charging?

sincere thanks,
Neal
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Old 09-16-2003, 12:55 PM
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Default RE: Is my charger bad?

Neal:

I guess you could check batteries that way, but I found a voltmeter from Hobbico that has a load built-in. Much easier. It's called an Expanded Scale Voltmeter. I doubt that Hobbico makes the only such device.

As for the charger, buy or borrow a Whattmeter, or something similar. When you hook it up between the battery and the charger, it can tell you what the charger is putting into the battery. If not, is there any way you could find someone with a charger with a display? If you can, charge one of your packs with it, and it will tell you how much charge the battery took and what its voltage is all during the charge process.

It's hard to diagnose a problem like this without good data. That's why I like "smarter" chargers like the Triton. The data it gives me on what the battery's taking during a charge (and putting out during a discharge cycle) makes it easier to spot problems and pinpoint where they are.
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Old 09-19-2003, 01:52 PM
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Default RE: Is my charger bad?

Taking Matt's advice to heart, I got another Jeti charger and it seems to have fixed the problem. I bench-tested a freshly charged pack and got 4 minutes at max power.

Also, I fabricated a canopy out of a 2 liter bottle using an idea gleaned from a different thread on this web site. It really improved the looks and will probably improve the flight characteristics of my Wingo. Winds are out of limits, so I'll have to wait'n'see on that.

Sincere thanks to all for the guidence and suggestions!

Fly safe,
Neal
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Old 09-19-2003, 08:59 PM
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Default RE: Is my charger bad?

OH cool! the quick reply window's working!!!

FWIW, you might not want to do extended bench runs. You don't get adequate cooling air over the motor (prop wash don't count!) and the motor, batteries, ESC, etc. can get overheated.
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Old 09-19-2003, 09:27 PM
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Default RE: Is my charger bad?

rog!
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