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Old Feb 14, 2013, 09:52 AM
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Accucel-8 voltage readouts faulty, or just me?

(Sorry if this is a stupid question, first time I've played with LiPos and 4 hours of Google didn't help)

Bought one of the HK Turnigy Accucel-8 chargers (http://www.hobbyking.com/hobbyking/s...idproduct=7523) and decided to road test it with a few AA cells and a 12V SLA I had lying around before hooking it up to a pack. I've already calibrated the voltage readings with the aforementioned SLA.

Just wondering, the voltage readout on the LCD when charging - is that the voltage the charger is putting out, or the voltage of the actual battery connected? Measuring directly across the terminals of the AA and SLA:

AA: 1.815V actual, display readout 2.05V
SLA 13.8V actual, display readout 13.9

I've remeasured it at various times with several multimeters, it's always a ~0.2V and ~0.1V difference.

Then when discharging, the difference seems to vary from 50mV to 200mV

AA: 1.25V actual, display readout 1.08V
SLA: 11.9V, display readout 11.84

I'm worried I'll fry my new LiPo packs is the charger is indeed dodgy. Is this kinda thing normal? Any help is appreciated
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Old Feb 14, 2013, 10:16 AM
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United States, WA, Seattle
Joined Jan 2007
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NiXX charging method is not the same as lipo. Over voltage is required to charge NiXX.
In either case what you see on the screen is output, not battery with NiXX.
With lipo hooked up you can toggle to a screen to see the actual battery voltage. In the main screen you see the output.
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Old Feb 14, 2013, 11:42 AM
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Joined Aug 2004
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Make sure you have a low resistance connection from the charger output to the battery. Try to use high quality connectors and heavy gauge wire - 14AWG to 12AWG.

Ron
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Old Feb 14, 2013, 10:27 PM
wandering aimlessly...
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Thanks for the replies, rsasaki and flydiver.

@rsasaki - how low resistance are we talking here? Say I'm going to charge 3x 5S 2700mAh packs in parallel at 1C, is 12G wire and XT60/HXT 4mm bullets sufficient?
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Old Feb 14, 2013, 11:50 PM
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How long is the charge lead?

The Accucell-8 bingos out at 7 amps so the difference between 12AWG and 14AWG is inconsequential if the charge lead is no longer than 1 foot.

Better chargers (iCharger, FMA) compensate for charge lead voltage drop and it's unfortunate that the cheaper Chinese chargers do not do the same. It's really rather simple programming of the charge algorithm and can cut charge times dramatically, especially at higher currents. This is one of the reasons why I personally recommend nothing less than the iCharger 106B+.

Welcome to RCGroups, BTW!

Mark
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Old Feb 15, 2013, 02:34 AM
wandering aimlessly...
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Quote:
Originally Posted by mrforsyth View Post
How long is the charge lead?

The Accucell-8 bingos out at 7 amps so the difference between 12AWG and 14AWG is inconsequential if the charge lead is no longer than 1 foot.

Better chargers (iCharger, FMA) compensate for charge lead voltage drop and it's unfortunate that the cheaper Chinese chargers do not do the same...

Welcome to RCGroups, BTW!

Mark
Thanks!

I did wonder why there was no remote vsense of sorts to compensate for leads, tis standard on precision PSUs and measurement equipment I've tinkered with in electronics. Guess it's because I was stingy and didn't look at any chargers over the $60 mark - hobby stuff isn't cheap down under

Total lead length from charger to where it goes into the physical lipo cells will hopefully be about ~25cm (4/5ft) max. Will probably use 10 or 12G wire as that's what the local electronics store sells.
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Old Feb 15, 2013, 06:40 PM
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Originally Posted by fudgemaster View Post
I did wonder why there was no remote vsense of sorts to compensate for leads, tis standard on precision PSUs and measurement equipment I've tinkered with in electronics.
It really is troubling. It seems that nearly all of these chargers are cut from the same cloth and the designers did not really understand what they were doing or how to properly design the charger for optimal operation. There's a lot of monkey see, monkey do among manufacturers.

While remote Vsense won't help a great deal with a 5 amp charger, this becomes far more important when operating at higher currents. I am currently testing a 1kW, 40A charger that does not have remote Vsense and it enters CV mode almost immediately due to high voltage drop in the charger output and charge lead. The resultant charge cycle takes forever, giving back a good portion of the benefit of having a high power charger. I've voiced my concerns to the manufacturer and I'm hopeful that this gets corrected.

Cheers,
Mark
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Old Feb 16, 2013, 01:27 AM
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Well, seems like this Turnigy Accucell-8150 charger is a lemon. Not sure whether there's a manufacturing/silicon fault or just buggy firmware but I'm going to try and get a refund on this.

When charging NiXX and Pb batteries, it's already locked up thrice in the 72 hours I've had it and spewed jibberish characters scrolling across the LCD screen Nor can I get it to sense voltage accurately when charging/discharging even at 0.1A with thick beefy wiring where losses should be negligible. And on top of that the timers get to 255 minutes and tick over back to zero. Haven't dared to connect a LiPo to it.

I suspect the latter issue is just poor design and the 8-bit timer on the microprocessor overflowing.

iCharger106B+ seems to have a pretty good rep. Looks like I will be forking out for one. Charger is useless to me if it can't even charge a 1.3AH SLA battery or a few Ni-MH AAs. Lesson learnt...

Thanks to everyone who's responded.
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