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Thread: Gayrad battery cherger
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24th Sep 2020, 08:17 PM #16Since the transformer output would be, say 16 volts AC for argument, the peak DC would be 1.414 times that, around 22.5 volts. But this is not a pure DC output, there is no smoothing capacitance to knock off the peaks.
With a battery connected this will do the smoothing and any measured voltage will be related to the load and how close to fully charged the battery is, it will still attempt to reach the 22.5 which will not be good for a lead acid battery. I would hope the secondary on the transformer is somewhat less than 15-16v.
Measurement of the DC voltage without load will be inaccurate as most volt meters are not designed for measuring pulsed DC particularly modern low impedance digital meters.
For electrolysis changing the distance of the electrodes or solution strength will assist if no voltage or current controls are available on the power supply.
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25th Sep 2020, 08:15 PM #17
I'm following along, I have a old awesome charger for over 20 years, my son used it and blew it up somehow but didn't know anything.
Looks simple enough but I haven't looked into it.Using Tapatalk
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26th Sep 2020, 03:13 AM #18
Hi Dave, Guys,
The usual cause of damage to those old style chargers is shorting out the terminals or reversing the polarity. The rectifiers don't like it and tend to stink the place out before going open circuit.
But if the transformer is OK, the wax runs out when they get hot, a new bridge rectifier and a couple of diodes in series with the output should get you up and running again.Best Regards:
Baron J.
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26th Sep 2020, 09:07 AM #19Senior Member
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28th Sep 2020, 01:25 PM #20Senior Member
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Hi guys.. Even though the switch tested OK for continuity, It appears that this may have been the fault after all... will replace the switch and see what happens after that.
Ken
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29th Sep 2020, 02:59 AM #21
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29th Sep 2020, 09:36 AM #22
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29th Sep 2020, 10:12 AM #23
A thought just occurred to me:
@ Kenny_10, when you say you have 6v but not 12v is that the voltage you measured on the output leads or are you saying that when the unit is switched to 6v you have output and if switched to 12v there is none ?
Without something connected to smooth the pulsed DC any measurement with a multimeter is going to be inaccurate.
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29th Sep 2020, 07:28 PM #24
Hi Guys,
That is the reason that I suggested using a side light bulb to test with ! A bulb will easily show up the difference between 6 and 12 volts and show any high resistance or open circuits.
For instance if the switch is just Hi Z in one position a multimeter could lie and tell you that there is a circuit there.
This is a known problem with high impedance meters when measuring voltages. This problem was known way back in the early 1900's and was the reason that the "AVO" with its known 20K ohms per volt input impedance was always the specified reference when measuring voltages. So much so that "AVO" manufactured the model "7" with a 2000 ohms per volt specification, this multimeter was intended for use on circuits like this battery charger and other low voltage high current equipment.Best Regards:
Baron J.
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29th Sep 2020, 07:55 PM #25
May not even be high resistance, I wonder if his high impedance meter is reading 6v DC while it is connected to 12v pulsed DC there is absolutely nothing to store the charge. Sounds like a bit of a low reading if that is the case but worth the confirmation of what is being checked.
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