How to use variable AC/DC power supply

Hi, I bought a variable voltage variable amp power supply to use charging my RC batteries:

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I don't really understand it much though. First, should I never turn it on if there is no load?

I will use it with either a nicd/nimh charger or a lipoly charger. In either case, should I turn the voltage to 12 volts, and the amps to the maximum (10), then turn on the charger? Should the charger be hooked up and turned on with a battery connected to be charged, before I turn on the power supply?

Thanks very much in advance for any guidance.

Jim

Reply to
CharlesBlackstone
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Seems to be a very expensive way to buy a battery charger. A bench power supply like this is designed to provide clean stable DC for electronics use - which you pay dearly for. Nor will it monitor the battery condition and adjust the charge to suit.

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*Some people are only alive because it is illegal to kill.

    Dave Plowman        dave@davenoise.co.uk           London SW
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Reply to
Dave Plowman (News)

ARRRGGGHHH! I hope this is a joke!

The cells you're trying to recharge require constant-current charging, not constant-voltage. And the bench supply you claim to have purchased is not only wrong for that purpose, but total over-kill. If you connect your batteries to it, you're likely to destroy them -- not to mention having to clean up a major mess, perhaps even put out a fire.

You need chargers specifically designed for the batteries you own.

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I just re-read what you wrote. If you have the chargers for these batteries, they should come with their own power supplies. You don't buy a bench supply to power them.

Reply to
William Sommerwerck

Thanks for the replies.

I bought this power supply for $300, because I have other uses for it, such as in my laboratory at work. But in some applications, I will use it to its max to charger very large battery packs for very large planes. It is what other people who do what I do buy.

RC battery chargers do not come with power supplies.

This is the charger:

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Thanks for any helpful replies.

Reply to
CharlesBlackstone

Okay. This is finally making some sense.

You'd set the power supply to a voltage in the range acceptable for the charger (say, 12V).

The current setting on the power supply is probably a limit -- the supply won't put out more than that (just in case you short it). So you'd set it to a bit more than the maximum you expect the charger to draw.

It's no more complicated than that.

Reply to
William Sommerwerck

Note: You can get a large selection of batteries (including Tenergy) chargers, packs, etc MUCH cheaper here:

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Than at the Batteryjunction site posted below. No affiliation, just where I buy all by stuff from... JR

HOME PAGE:

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Reply to
JR North

CharlesBlackstone wrote in news:17fdbbc6- snipped-for-privacy@s50g2000hsb.googlegroups.com:

Your supply seems to have two kinds of limits. Voltage and current.

This means that you can regulate the 'open circuit voltage'. You would want to make sure that never exceeds your battery voltage by more than a few percent.

The current regulation means you can regulate the 'short circuit current'. You would want to make sure this never exceeds the safe charging current for your battery (which should be something on the order of 10% of the discharge current).

You should look up the charging conditions for your particular battery, with nothing connected to the supply, set the open circuit voltage. Then, with an amp meter (perhaps the supply has one built in), short the output and set the current to less than the max charging current.

NOW, you can connect your battery to be charged.

Since you have a 'dumb charger', you will need to monitor the charging to make sure you don't overcharge the battery. If your voltage and current settings are correct, that shouldn't happen, but .... it is better to be safe than sorry.

What you do NOT want to do with a TRUE current supply (one that could go to any voltage) would be to open circuit it, because it would go to infinite voltage. What you do NOT want to do with a TRUE voltage supply (one that could go to any current) would be to short the output because the current would be infinite. A supply that regulates BOTH, however, is limited in both and thus kind of the best of both worlds.

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bz    	73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an 
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bz

t
o
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What is the voltage and current that is specified to charge the batteries that you are planning to charge????

Reply to
hrhofmann

From the website you listed

I would have just bought a 10A 12vdc transformer and hooked it up to that charger or I would have used a car battery charger hooked up to your electronic charger. The bench supply is the wrong tool for this although it should work fine. It is just like using a military tank to go buy groceries, sure it works but it is huge, costs 100 times more and has all sorts of things you don`t need to get the job done.

Mike

Reply to
Michael Kennedy

IMHO the charge voltage is pretty irrelevant. It's the current that matters.

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*I took an IQ test and the results were negative.

    Dave Plowman        dave@davenoise.co.uk           London SW
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Dave Plowman (News)

"Dave Plowman (News)" wrote in news: snipped-for-privacy@davenoise.co.uk:

I agree that the current IS the most relevant parameter.

The voltage is relevant if there is a cell that is failing or if you want to safely charge different kinds of batteries and avoid overcharging.

There is no harm to limiting the voltage.

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bz    	73 de N5BZ k

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bz

OK, this is what you do. You will need a diode with at least a one ampere rating. Connect the cathode, that is the lead that is next to the band around the body, to the positive binding post. If your batter is rated at, say 12 volts, get a 12volt auto lamp rated at one amp, like one for the tail light. Hook it to the remaining lead of the diode. Now set the voltage on power supply to 13.6 volts. Next connect the positive terminal of the battery to the free lead of the lamp. Connect the negative lead to the negative binding post.

If the battery is not charged at all, the lamp will glow brightly as the current flows into the battery. It should dim over time as the battery charges up. If it doesn't, then the battery may be dead. If you have a voltmeter, check the voltage of the battery every now and then. If it reaches 13 volts or so, it will be fairly charged.

If it is a 6 volt battery, get a 6 volt, 1 amp lamp, and set the power supply to 7.2 volts.

Other battery voltages will take other values for the lamp. If you have a

7.2 battery, put a 6 volt and a 1.5 volt lamp in series. Set the voltage to 9 volts on the power supply.

What does the lamp do for you? It limits the current inrush to a discharged battery and gives you a rough idea of the state of charge of the battery.

The diode prevents a mistake where the voltage on the battery is higher than that set at your power supply. You don't want the battery to be pushing current into your power supply.

Experiment and have fun!

Al

Reply to
Al

"Dave Plowman (News)" wrote in news: snipped-for-privacy@davenoise.co.uk:

Here is a current regulator that can be used for 0-2A with supplies that don't have current regulation built in.

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bz

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bz

avenoise.co.uk:

s.HTM

Hey thanks everyone for all the great answers. I have been busy and not returned (and I thought the thread had sort of faded away).

bz, what is the purpose of regulating the current, when the power supply can supply current from 0 to 10 amps (or if I parallel the two PS in it, 20 amps)?

Al, thanks. When people charge batteries directly with these PSs they do use a diode. I may do that eventually but for the moment am using the PS to power pretty smart chargers. In that situation your idea of having the bulb in circuit is brilliant, it's a way to monitor charge status. Cool.

Mike, this is down the road, and why I got this monster:

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Thats' 44 volts he's putting in those batteries starting at 10 amps, and as you can see it just takes a few minutes to replenish a pack that holds 2300 mah. The objective is to charge a pack in the same amount of time it will keep your plane in the air, so with a couple batteries and the Mastech PS, you can fly all day. People either use a Honda generator/inverter or a couple deep cycle marine batteries with an inverter. This is not a cheap hobby. Probably more than you wanted to know but.....

Thanks to your help I set the voltage at a little over 12 (since I dont' have a diode between charger and PS), put the amps at max, turned the PS on, connected it to the charger which was already connected to the battery, and the charger nicely started pulse charging the nimh transmitter pack. I'm so new to this stuff I was afraid to turn the Mastech on which I just got. All is good now.

Wow, this is a great group and lot's of nice folks, I'll come back for help and let you know how my learning curve goes.

Jim

Reply to
CharlesBlackstone

=A0 London SW

Hi Dave, I know what you mean by expensive, but this Chinese Mastech switching triple power supply (30v10a cccv, 30v10a cccv, constant 5v) cost less than $300. I looked up the price of a similar Agilent or Tektronics PS and they were about 1500 percent of that.

Jim

Reply to
CharlesBlackstone

CharlesBlackstone wrote in news: snipped-for-privacy@i76g2000hsf.googlegroups.com:

I was assuming directly charging batteries from a DC power supply.

If you have a supply that has an adjustable current regulator built in, the cicuit I showed is not needed. I didn't look at the specs on YOUR supply so I was just giving a link to a nice current regulator I had seen. If you were charging batteries directly from a voltage regulated supply, without any current regulation or limiting, you can damage your batteries.

....

Check the specs for the batteries you are charging and be sure that you never exceed the 'maximum charging current' ratings. Otherwise you will damage your batteries and shorten their life.

I had a small battery blow up when I tried to recharge it.

You have a charger that is [I assume] designed for the batteries you are using. Its job is to regulate the current flow so as to charge as fast as possible without damage to the battery.

Good luck and be careful.

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bz    	73 de N5BZ k

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bz

snipped-for-privacy@i76g2000hsf.googlegroups.com:

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Thanks, will do, same to you.

Reply to
CharlesBlackstone

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