Patman3 Solar Expert Posts: 62 ✭✭✭✭
I recently purchased a http://www.evparts.com/shopping/product_details.php?id=312&product_id=4090 DC2461 thinking its a DC to DC converter (used to charge one 12V accessory battery from a pack of 20 6V batts). They sent me an Iota DLS-45 with an A/C plug. Now it says I can connect that A/C plug directly to my 120VDC traction pack to make 13.7VDC, and the polarity doesn't even matter? I want to ask you experts here Before I do this, thanks for your input!
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i would call iota they have great tech support they will answer all the questions for you. then there wont be any warranty issues
:? Something's not quite right here.... The DLS-45 is a 120 VAC to 12 VDC (nominal) power converter. It's not an inverter, and it's input wiring should not be connected to a DC source. Here's a link to Iota's specs for the DLS-45 converter.
Jim / crewzer
Well I took your advice 1/2 and called Iota in Tucson (wow, a company in MY timezone!). I talked to Don Bull, no bull, and he thought for a second and said ya sure, it's switching technology. So I have the go ahead to connect this to DC and use it as a DC to DC converter. In fact, if I use a regular 110V socket on my EV I can charge 12V from a DC or an AC source just by changing where the DLS is plugged in. Learn something new everyday!
let us know how it works i want to build a ev soon and that seems like a grand idea it can be wired right in the car and could ve used either way that would be to cool
I hooked up the DLS-45 to 120VDC and sure enough it works! I first made sure it worked by plugging into 120VAC outlet, fine, 13.5V or 14.1VDC output with the little RJ-11 plug in. OK, I wired a socket into the 120VDC EV battery bank so I could plug it right in. Being cautious I used some clip leads to test the final connection left to made, thinking if I did anything wrong the clip lead will act as a fusable link. One thing about switching technology, when you first connect it, IT SPARKS, capacitors charging I guess, so it was exciting and worrysome, but sure enough this works as a DC to DC converter. Comes on when the ignition comes on so my headlights and all accessories get 13.5 volts instead of 12.4 which makes a BIG difference. I see some new possibilitys with wild ac and or DC input to this unit, even maybe connecting solar panels directly to its AC/DC input and using it as a charger that way?
I have to admit that I'm surprised to learn that this application worked, as I'm not one for specifying items outside of the manufacturer's specs. The spark you saw is common on high-current DC applications. Make sure you use a DC-rated switch for the input, as they're designed to handle the DC arcing.
I hope you'll keep us updated on the unit's long term performance.
Jim / crewzer
WOW, that is very intresting. I wonder what the voltage range the DLS line will accept on the input side. That would be a cheap and dirty way to get 48vdc to 12vdc, if it worked with voltage that low.
48V prob to low, I read 96V-180V although Don thought the 180V was a bit high for it. I might get another one and experiment, now I know they can be had for ~$150.
I just put the lug for it onto the relay that's switched on from the ignition key for the EV which is high current DC already, like 400 amps.
Switch Mode Power supplies are pretty neat items... Their input stage takes the AC voltage and rectifies it into DC (older ones would do this through a voltage doubler).
So taking an AC power supply and connecting it to DC could simply look like just a reallllllyyyyyy loooonnnnngggg Sinewave peak and simply pass the DC input right into the converter's DC input.
Of course, this is going to be design dependent--but I would not be surprised to find more than a few plain vanilla AC switch mode supplies that would work OK on DC input...
In fact, I was toying with the idea of modifying a switch mode DC battery charger to take raw high voltage solar panel input (like that required for a Xantrex 3.x) Grid Tie only inverters as a emergency backup (charge the batteries the 99.9% of the time simply plugged into an AC outlet... During a power failure, switch the 200-400 VAC solar panel connection to the modified AC to DC battery charger). The one issue I saw was how to ensure that solar power input is not swamped by the battery demand for current (need to match input power available to power requested to charge batteries--normal for a solar charger--not a normal function for a line powered battery charger).
May not be worthwhile to hack something up--but it seems a perfect option for IOTA or some manufacturer to join the Solar Market on the cheap.
Bill that was exactly the use I was thinking of. For grid ties higher voltage arrays getting them down to smaller backup battery setups. Very interesting. Do you think the voltage fluctuation from solar panels might mess with the regulation? Or are they pretty good at that?
The common(now old fashion) Switch Mode Power supplies with a voltage doubler front end would typically operate on an AC range of 95-180VAC. Multiply that by sq rt of 2 (AC crest voltage) and 2x (voltage doubler), and the intermediate stage high voltage cap/section should be around 268-510 VDC (the 240 vac version of the supply take out the voltage doubler). The output voltage is very stable (for those supplies using voltage feedback loop).
But, those types of supplies are getting rare now. Because, of the simple diode rectification on the front end, the supply basically draws all of its current on the voltage peaks--creating a very bad power factor and for any supply over a few hand full of watts, not allowed in Europe now.
Many (if not most) newer supplies (last 10+ years or so), are power factor corrected supplies--make the supply input look, more or less, resistive in nature (input current is proportional to input voltage). One method to do this is to have another switch mode front end that "samples" the input voltage and converters the energy across the whole sign wave and use the to power the high voltage DC intermediate voltage section...
It has been many years, and at the time, I was not thinking of passing DC power through such a front end--so I never studied how it would respond to a DC input. One of the advantages of this type of Power Factor Correction circuit is that the supply would operate (without internal or manual range select) from 95-265 VAC (versus a non-operational zone of 180-200 VAC or so of the old voltage doubler models).
If, a PFC could take DC, the wide range input would be a really neat setup.
Slap on a good size Schockty blocking diode and heat sink, plus remote sensing back to the battery posts, a supply with current limiting (rather than crowbar voltage/current safety limits) would make an interesting emergency backup.
One of the other issues that I was concerned about was what I mentioned above. This is the nature of a standard computer/battery-charger type power supply that assumes an unlimited amount of input power (example 0-15 amps of 120 vac) and only is setup to regulate the output voltage and current.
With solar panels, you can generate the voltages, but as soon as the load exceeds the current output of sun available, the solar panel voltage sages (or crashes). For a switch mode supply, these are typically constant power type devices.
For example: 13 volts DC @ 20 amps would be 260 watts... Call it 300 watts at the input power to the supply.
The solar panel (like mine) is setup to supply typically ~280-330 VDC at 9.8 amps (max sun). 300 watts to the supply at 300 volts is only 1 amp. For my panels, an MPPT controller (Xantrex 3.0 GT) I can get 300 watts over much of the day (morning to evening) and even under a fairly heavy overcast day. But, on those days/morning/evening transition periods (or if I want a higher power DC to DC converter) as soon as the sun available current meets the current required (1 amp in this case), the voltage will start to sag on the solar panel output--But, the power supply being a constant power device wants to keep passing 300 watts, so it will crank up the current to compensate. But the solar panel is already current limited, the solar panel voltage will collapse and the power supply will shut down--restarting the whole process again.
A solar charger/controller, would simple pass less energy to the batteries. The DC-DC power supply is almost the anti-MPPT controller in this configuration.
For smaller backup systems with large arrays, this may be perfectly OK behaviour (may need some inhibit/delay function for the modified power supply to prevent nasty oscillations). But if you have a 3.5 kW (STC Rated) array and want anywhere more than 10% or 20% of solar array capacity usage--I would have to think really hard how to modify a supply to make the output current available some how do a MPPT job on the solar input....
Anything I typed make sense?