Mains-capable ACDCDC charger?

[Pskhaat]

Maybe an RC car/airplane battery charger. I have several that take 110v or 12v input, and output in Lipo/NiCad/Nimh/Lead acid/etc, so depending on what your battery type is, it should work. For example, charger. Mine looks similar to that one.

They look like a good charger, but don't have a back-end DC^x connections.

 

[DaveInDenver]

I mentioned this in another thread Scott but this same solution may work for you.

You can run a AC/DC power supply into the input of a DC-DC charger. For example, I run a Victron Orion-TR 12/12-18, a DC-only charger. But when I have mains available I use a repurposed ham radio power supply, specifically a Powerwerx SS-30DV.

https://powerwerx.com/ss30dv-desktop-dc-power-supply-powerpole

There's cheaper ways to go, I just had this one around already. If I was buying one I'd go with some sort of single voltage industrial power supply, probably the Meanwell LRS series.

For example, this 350W version, which you can tweak up to 13.8V (it needs to be capable of being set high enough for the DC-DC to turn on, which for my Victron I have at 13.0V I think) and costs $32.50.

https://www.jameco.com/z/LRS-350-12...gle-Output-Enclosed-Power-Supply_2219807.html

 

[Pskhaat]

I mentioned this in another thread Scott but this same solution may work for you.

You can run a AC/DC power supply into the input of a DC-DC charger.

I think this is exactly what I'm going to do.

I was debating using a high-power computer PSU, where it would implicit for 120/240 switch and I could combine a number of lines off the 12 rail, but like you had said realized maybe a really clean +12VDC isn't enough voltage?

 

[DaveInDenver]

I think this is exactly what I'm going to do.

I was debating using a high-power computer PSU, where it would implicit for 120/240 switch and I could combine a number of lines off the 12 rail, but like you had said realized maybe a really clean +12VDC isn't enough voltage?

Are you thinking something like a regular ATX sort of supply? That might be an option, the +12V on those can be fairly sizeable.

You may have a couple of options. First make sure you're above the minimum input voltage and can supply the power it'll work.

My Victron says it'll work over an input range of 8V to 17V. So since this is a 220W charger with 87% efficiency I need at least 253 watts (this by the way I've found to be accurate). The output of a full size ATX supply would likely be fine here. I would give yourself some margin, keeping the voltage between 10V and 15V would be easier on the DC-DC converter long term and sizing the mains supply not to run at 100% either.

After that you just need it turn on. If your DC-DC is ignition triggered you could just connect that trigger line to the output or ground (may depend on the design, very likely it'll be high to trigger ignition hot) of the power supply and it should not care about actual input voltage other than it *may* want the ignition hot to be within some tolerance of the battery voltage. IOW if input is 12.0V the ignition sense circuit might not like being 9V.

There is a possibility that you would want to delay the ignition hot signal, so if it was me I'd put a switch on the sense line so that you can turn on the mains power supply, let the DC-DC stabilize and then turn on the ignition hot.

As I mentioned I run a Victron that triggers on input voltage and not ignition status. FWIW, I misremembered in my last post, this is what mine is actually set to. So instant start at greater than 13.6V, start if 13.2V after 120 seconds and shutdown at 12.75V.



Assuming an ATX is 12V +/- 5% (which is typically the spec) it could be 11.4V up to 12.6V. I could make the start voltage 11.4V and lower the shutdown voltage. This would be a bit of a pain since you would not want to let the DC-DC run that low on your truck battery, as you probably already know. But it should do what you want.

Just a word here, remember it's a power transfer. So if you do test the lower voltage limits be sure to meet the power and current. If the DC-DC wants 253W you'll need at an actual 12.0V the current is 253W / 12V = 21.1A constant. In the case of my Victron this will provide an output of 18A bulk up to my absorption target of 14.2V on the battery side. If I wanted to use 8V then the power supply would need to source 253W / 8V = 31.6A.

I suspect (as in I don't remember) but I assume 13.6V I picked because of this power supply. Victron defaults to 14.0V for instant start. These values could also be since my Toyota alternator runs on the low side.

Using a AC/DC power supply that more closely mimics an alternator is convenient of course. If your DC-DC lacks an ignition hot input and cannot be adjusted for turn on voltage, then you would be forced into a power supply with the right voltage, for which an ATX would not work. Most of them can be trimmed but I doubt any of them will let you run them up to quasi-automotive "12V" values on the +12V line. Normal motherboards will fault (or fail) above 12.6V so there's no point most of the time and compliant ATX supplies would trip their overvoltage protection there anyway.

 

[DaveInDenver]

@Pskhaat just looking through options. That cheap supply I mentioned requires you to switch 120V or 240V but there are industrial supplies that will auto switch on AC. This is more common with medical rated supplies and similar critical applications.

They're still not super expensive, $87 for a 324W 12V and can be adjusted up to 13.8V.

https://www.jameco.com/z/HRP-300N3-12-MEAN-WELL-12VDC-27A-324W-Single-Output-Enclosed-Ultra-High-Peak-Power-Supply-with-PFC-Function_2334039.html

This one is $53, 320 watts, can get to 13.2V so it'll be close.

https://www.jameco.com/z/RSP-320-12-MEAN-WELL-AC-to-DC-Switching-Enclosed-Power-Supply-with-PFC-Function-12-Volts-26-7-Amps-320-4-Watts_2172084.html

There is a bit of gotcha with this solution. The AC mains are exposed on a screw terminal block. So you need to put something like this in a box for safety.

 

[craig333]

You could go with something like an IOTA converter. Pretty simple. Reminds me I need to grab the electric heater for my once a year full hookup campground.