Measuring output voltage of a battery charger

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bigato
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Joined: Sat Mar 05, 2011 12:43 pm

Re: Measuring output voltage of a battery charger

Post by bigato » Wed May 29, 2019 1:14 pm

Building an ac/dc converter from electronic parts could be another interesting project. A lot of electronics courses have this device as one of the first circuits students study, because it is simple enough to be good for learning but also diverse enough to teach you a lot of basic electronics concepts.

Sclass
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Joined: Tue Jul 10, 2012 5:15 pm
Location: Orange County, CA

Re: Measuring output voltage of a battery charger

Post by Sclass » Wed May 29, 2019 1:55 pm

Ok. I’m not sure the power adapter is done yet. Who knows what that thing is or what it does. The circuit may see open as a low current state and it tapers down the voltage. Just a theory. Maybe the lights don’t turn on till a good battery is hooked up.

The solar charger sounds like a fun idea. I mentioned on another thread that I use a solar panel to float charge my car. All you need is a diode to keep the current in the battery at night.

12v supplies can be found everywhere. I just set aside one that my dsl modem used when my modem blew out last week.

Lucky C
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Re: Measuring output voltage of a battery charger

Post by Lucky C » Thu May 30, 2019 4:22 am

If you could wire the charger to a battery (temporarily) such that you can probe while attempting to charge, you can at least see if the Vout is still the same with the battery is attached. Then you can connect a low value resistor (e.g. 1 Ohm 1/4 W) in series with the battery so you can check if there is current flowing by measuring V drop over the R. I'm guessing you will still see 7V with about zero current but worth trying if it's easy.

1 Ohm resistors are a cheap way to add troubleshoot probe points to check current draw for each active device in any board design, as long as the V drop is insignificant.

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Ego
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Re: Measuring output voltage of a battery charger

Post by Ego » Thu May 30, 2019 7:13 am

Cordless stuff is made to die. Screw that! Make it a corded.

https://www.instructables.com/id/Cordle ... dd-a-Cord/

Sclass
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Location: Orange County, CA

Re: Measuring output voltage of a battery charger

Post by Sclass » Thu May 30, 2019 7:16 am

Lucky C wrote:
Thu May 30, 2019 4:22 am
If you could wire the charger to a battery (temporarily) such that you can probe while attempting to charge, you can at least see if the Vout is still the same with the battery is attached.
Brilliant, this is what we should have suggested first. Clip the wires that were once leading to the old battery to a car battery and see if the charge lights on the charger light up. Car off of course. Jacob has a battery on the way so I guess he won’t have to go this route.

Sclass
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Joined: Tue Jul 10, 2012 5:15 pm
Location: Orange County, CA

Re: Measuring output voltage of a battery charger

Post by Sclass » Thu May 30, 2019 7:38 am

Ego wrote:
Thu May 30, 2019 7:13 am
Cordless stuff is made to die. Screw that! Make it a corded.

https://www.instructables.com/id/Cordle ... dd-a-Cord/
Agreed. There’s nothing more awful than having a battery powered tool with a dead battery that is very expensive to replace. I started avoiding cordless tools a decade ago when buying new stuff.

Interesting how many of these thumbnails use laptop supplies. They put out a hefty amount of current for their size and weight. I never throw those away when trashing an old laptop.

On the other hand, the new brushless dc/lithium ion tools are quite amazing. Nothing like the 12V Nicad Makita stuff I threw in the trash can because of expensive batteries and the availability of more powerful cordless tools. Like a Tesla of hand tools. The neat thing about Li Ion is you can buy replacement batteries from Hobby King (toy car cells) or 18650s from eBay to rebuild them.

I’m on the fence right now on which brushless dc chainsaw I’m going to get to replace my corded unit. I have a Smokey two stroke that needs a carb clean but I’m sick of the carcinogenic premix and noise. The cost for BLDC is expensive but after driving drywall screws a day with my friend’s new cordless drill I can see myself converting to the new tech (at least for a chainsaw). It is amazingly high performance in terms of weight, torque and speed control. They just kill you on the batteries.

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