Posted on 05/10/2023 8:07:46 AM PDT by Paul R.
Ah, I’ll reply to you 1st, as that is the piece of missing information I needed!
No, in fact, I did not realize the outer barrel is double-sided, with metal contacts on both sides. But, sure ‘nuff, there’s an outside sleeve (metal cylinder) insulated from an inside sleeve (metal cylinder), and then the center pin. 3 conductors total. It is a very simple yet clever and strong design that makes it nearly impossible to short out the supply with an errant or forced plug-in attempt.
So, I grabbed my cheapy meter and the outside conductor measures at 19.75 volts. I believe this supply will power just about any small project I might have needing a few amps at around 20 volts, without any trickery needed, and... these are also made in a 240 watt version... :-)
Thanks for the info!
That sounds like the “Mad Magazine” “voltage tester” — a short AC extension cord with a male plug on each hand, available from “Dept. Bzzt!, Blackhand, South Dakota”, IIRC.
:-)
See my post 22. Thanks.
Yes, I have two car chargers that behave exactly that way.
Some chargers of rechargeable AAA-D NiMh batts, and of 18650’s (etc.) also need a decent bit of voltage on the battery for the charger to work.
So, sometimes I have to give a low battery a bit of a charge from a dumb charger or from another battery with a 10 ohm resistor in series, THEN put the run down battery in the smart charger. Often but not always, the “too depleted” battery can be recovered.
(I try to avoid running rechargeables “way down”, because it is quite hard on them, but, that’s sometimes hard to avoid...)
See my post 24. Some chargers will NOT charge a battery exhibiting very low voltage. I’ve not rigorously tested that on the 2 car chargers I mentioned, but, on the one the threshold seems to be 5 volts or so. The charger “thinks” the battery is a short, and stays off. Hook the low battery to a good strong battery through a “light” jumper cable (built in resistance to limit the current a bit) for a moment, remove that connection and hook the charger back up, and now the charger charges the low battery.
(Of course, severe depletion is also not good for car batteries, and severe depletion and a little time left that way is really deadly to them...)
See my post 22. Thanks.
I’m hopeful a “genuine” Dell charger won’t be too hideously noisy. Guess I’ll find out when I get to my next small audio amp / powered speaker project...
Sure, go ahead and argue with me over whether the battery charger I used to try to charge a completely dead battery worked or not.
Hint: It didn’t.
I ended up having to use a variable bench power supply to get enough charge into the battery so that the battery charger would detect it and start charging the battery.
They could put a button or setting on these “smart” car battery chargers that you could push to allow them to start charging a completely dead battery so we don’t have to resort to things like using a dumb charger or temporarily connecting a good battery in parallel or using a power supply.
You’re welcome!
“That should work, assuming the fan wants to see 12 VDC and not AC”
Thanks to you and brian1703 for your informative replies!
I hope our moderators don’t mind if we deviate from politics occasionally.
From what I’ve seen, pretty much any “smart” car battery charger will refuse to charge a completely dead battery. (I think this is because they’re designed to verify that you haven’t connected it backwards, and it needs to see some voltage from the battery to verify before it turns on the power).
The battery chargers with the heavy transformer inside a metal case, and old-school analog ammeter don’t have this problem.
The nitwits on those sites need all the help they can get.
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