variable voltage dc power supply as battery charger

[almac]

so if you use a variable voltage dc power supply to charge 12v FLA battery, say set voltage to 14.4v , as the current drops take S.G. readings till 100%. is ok? sales guy reckons i will wreck the battery with a dc power supply. told me MUST use multi stage charger. iv found multi stage chargers sometimes dont fully charge the battery. they have cut off as "full" when the S.G. was only 1.225 even less.

oh.. i see im now a solar fanatic

[Willy T]

It will work the same as any charger , but requires your manual intervention to turn it off once your satisfied with the absorb. I'd put it on a timer so you don't forget it's on. Mine has a tendency to overshoot the set voltage a tad once it reaches the set display voltage.

The SG level requires rest period before it's 100% accurate from a regular daily charge, some batteries ( tall case ) can rise as much as .015 or so after a couple hrs of rest. Doing a EQ is different as your purposely pushing them to a overcharge.

Getting to know your batteries and how they react is all the fun.

[Sunking]

All chargers are variable DC power supplies. Set it and forget it. Every Ham Radio Operator, Telephone company, and utility company operates that way. Just do not set it to Absorb Voltage, set it to Float Voltage as it is the best kindest, and most gentle algorithm you can use. You can keep the battery on Float Charge for eternity with no problems.

If you want to EQ just up the voltage to 15 to 16 volts and keep it there until the battery SG EQ's and terminate.

[lkruper]

so if you use a variable voltage dc power supply to charge 12v FLA battery, say set voltage to 14.4v , as the current drops take S.G. readings till 100%. is ok? sales guy reckons i will wreck the battery with a dc power supply. told me MUST use multi stage charger. iv found multi stage chargers sometimes dont fully charge the battery. they have cut off as "full" when the S.G. was only 1.225 even less.

oh.. i see im now a solar fanatic

To complicate things (and extend battery life), how about adjusting the voltage based on the battery temperature?

[Sunking]

sales guy reckons i will wreck the battery with a dc power supply. told me MUST use multi stage charger. iv found multi stage chargers sometimes dont fully charge the battery.

He is full of Chit and trying to sell you something.

Every commercial operation uses DC power supplies to charge batteries, they call them Rectifiers and they have only two settings of FLOAT and EQUALIZE. They can adjust the FLOAT AND EQ voltages to anything they want, as both modes are still the exact same 1 stage algorithm of CC/CV. Only difference is the voltage set points. The way you make it work is selecting a power supply to match your battery voltage and current requirements. Of you have a 12 volt 100 AH battery you want a power supply that has a current of 10 to 15 amps, and you can adjust the voltage from 13.2 too 15 or 16 volts.

Three stage charging is useless in a solar application because there is not enough hours in a day. We have been through this a dozen times with you.

Real life example I have an Astron VS-70M pictured below I can adjust current from 1.5 to 70 amps, and voltage from 1.5 to 16 volts. That means I can charge any Lead Acid Battery of 2, 4, 6, 8, and 12 volts sized as small as 12 AH up to 800 AH and everything in between.

Being an RC pilot I also have a Revolectric Powerlab 8 Hobby charger that I can connect to the Astron and charge any battery type to with any algorithm up from 2 to 24 volts @ 360 AH, and allows me to make my own custom charge algorithm.

For you all you need is a simple Float Charger of appropriate voltage and capacity to EQ on a generator. Set it to 15 volts and have at it till the SG comes up. Ot set it to float voltae and run until eternity.

[almac]

To complicate things (and extend battery life), how about adjusting the voltage based on the battery temperature?

yes i read on a site that in winter voltage for a 12v FLA needs to be at about 15v. if below 16 deg C

[inetdog]

yes i read on a site that in winter voltage for a 12v FLA needs to be at about 15v. if below 16 deg C

This is why a good RE CC will at least have the option of a remote temperature sensor located right at the battery stack. Usually mounted to a battery terminal or sandwiched between two batteries.

The most important item that Sunking mentioned is that the variable power supply has to support a variable current limit too. Otherwise a PWM CC may overload the power supply and cause problems or deliver too much current to the battery in Boost phase.

[almac]

This is why a good RE CC will at least have the option of a remote temperature sensor located right at the battery stack. Usually mounted to a battery terminal or sandwiched between two batteries.

The most important item that Sunking mentioned is that the variable power supply has to support a variable current limit too. Otherwise a PWM CC may overload the power supply and cause problems or deliver too much current to the battery in Boost phase.

at the moment the solar panels and CC are almost useless being middle of winter with 3 out of 5 days cloudy. so the temp sensor is a moot point. iv just bought myself a small cheap gen set dedicated to recharging my battery bank. i only need a small battery bank of 24v 160ah , so iv got a 1100w gen and will get a 30amp variable voltage dc power supply for recharging 24v batteries. for now just using a 25amp variable voltage for 12v batteries.

[PNjunction]

Real life example I have an Astron VS-70M pictured below I can adjust current from 1.5 to 70 amps, and voltage from 1.5 to 16 volts. That means I can charge any Lead Acid Battery of 2, 4, 6, 8, and 12 volts sized as small as 12 AH up to 800 AH and everything in between.

Careful there big guy. Not being designed as a battery charger, you don't want to remove the AC power to the Astron while under charge - say by accident, remote wall switch etc. Poof. Or making the battery connection and then trying to power up. If you are going to do that the BB option for the Astron is the way to go. Maybe yours has been modified ... all you have is a simple series limiting resistor which can go poof when the ac is removed I believe. That or the battery, discharged as it might be is enough to fry the 723 and associated circuitry..

http://www.repeater-builder.com/astron/astron-bb-info.html

For safety reasons, if one is going to use a variable supply, be sure it is capable of handling batteries. I think the salesman just really meant to use a charger designed for batteries, and not any old power supply laying around without making sure it will handle things - especially if the ac is removed while under a battery load. Some do, some don't.

[Sunking]

Careful there big guy. Not being designed as a battery charger, you don't want to remove the AC power to the Astron while under charge - say by accident, remote wall switch etc. Poof. Or making the battery connection and then trying to power up. If you are going to do that the BB option for the Astron is the way to go.

Yep I am aware of it. Learned that lesson 30 years ago.

[PNjunction]

For me, about 20 years.

Still, you point out the great utility a variable supply is for us battery-geeks that roll our own, be it lead or lifepo4. Either stand-alone or as a supply to a specialized charger.

I think the info from Mastech about their "Volteq" line of switching pwm variable supplies that can safely deal with batteries with the "EX" line is very informative near the bottom:

http://www.mastechpowersupply.com/linear-vs-switching-power-supply.html

I don't own one of these, but I might consider when I pick up 200ah lifepo4 cells and do the diy maintenance thing...

[Sunking]

I think the info from Mastech about their "Volteq" line of switching pwm variable supplies that can safely deal with batteries with the "EX" line is very informative near the bottom:

Personally I am not a fan of switch mode power supplies for my use. I use my Astron to charge batteries which any SMPS can do, but I also use it to power radio equipment and sensitive electronics which SMPS are not known to play nice with. They are just simply generate too much RFI. As you know the Astron is an old fashion Boat Anchor DC power supply with massive transformer, heavy duty Bridge Rectifiers, huge Brute Force filter capacitors, and very accurate good ole fashion series analog regulators. They are super easy and cheap to repair and easy to modify. I have two of them. One I bought 35 years ago when I first got my ham radio operator license.

I get emails almost every day for ham radio operators wonder why their solar charge controllers and 12 volt SMPS FUBAR their RX.

[lkruper]

Real life example I have an Astron VS-70M pictured below I can adjust current from 1.5 to 70 amps, and voltage from 1.5 to 16 volts. That means I can charge any Lead Acid Battery of 2, 4, 6, 8, and 12 volts sized as small as 12 AH up to 800 AH and everything in between.

Sunking,
The descriptions of the Astron VS-70M online say it has a voltage range of 1-15v and the picture seems to confirm this. How do you get 16v? The Mastech 1-30v/1-30a is said by the manufacture to go as high as 32v, so apparently there is a way to get more out of them?