Author Topic: High Voltage DC Charger (OUCH) 🤔  (Read 57 times)

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Offline Solarnewbee

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High Voltage DC Charger (OUCH) 🤔
« on: February 11, 2020, 06:54:29 pm »
Salutations All

Here is my attempt at building a high voltage dc power supply-charger for use in conjunction with an mppt charge controller. The charge controller has a high limit of 150vdc and 95a. The charge controller can be set to limit the amount of current that can be drawn from the source which is a concern since who know how much a Midnite can suck thru the mains with its got inside. My 60v 5a power supply connected to the Midnite equals 9.9a out so it def boosts the power.

Supply cord will be a 20a desktop style cord into a switched/fused inlet with 20a fuse. Cord will be plugged into a 3000w step/down transformer 120v For use as an isolation transformer. Better to trip the transformer breaker than the mains 😳.

From the switch we go to a 1000v 100a bridge rectifier mounted on sheet of aluminum for cooling if that’s even a thing. I’m squeezing all this in an old broken power supply case. After the bridge rectifier the 120v passes thru an AC line filter from an inverter mini split HVAC. I was just trying to find a way to get a smooth wave form so I tried this board I had laying around. The wave went from an absolute mess to a sine wave with flats. I will add a pic later and a diagram as well.

As soon as I added caps as you know the volts went up and sits right at 160v. I tried a voltage divider 3.9k x 3.9k bringing down to 81.6v but my grasp of voltage dividers and passing current is lacking quite a bit apparently. Another scenario might be r1=300r r2=1k 100w each. According to the divider tool that brings 120v to 90v a 30v difference which brings 160v in this case down to 130v safe for the Midnite but at what usable current. Still have room on the heatsink for the 100w resistors.

So, go ahead let it out. Anyway is there something I could use to test this on besides a $600 midnite and myself? I have 4-24v lfp packs i could discharge, series together and let er rip! 😝

Until next time!

Seriously if there’s
SN

Any day above ground is a day for potential mishaps

Offline noneyabussiness

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Re: High Voltage DC Charger (OUCH) 🤔
« Reply #1 on: February 12, 2020, 04:29:33 am »
Just a suggestion,  have you thought of using one of these

https://www.ebay.com.au/itm/272834881672

If you wind 2 - 3 more turns on the primary transformer,  it will bring the voltage up enough to be a current controllable charger on its own..

I have one, and use it regularly.  Comfortably does 3kw , high 80%  - low 90% efficiency.. and cheap..

Offline noneyabussiness

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Re: High Voltage DC Charger (OUCH) 🤔
« Reply #2 on: February 12, 2020, 04:38:15 am »
Just remembered your system is 24v... so its should be fine out of the box.

Offline Solarnewbee

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Re: High Voltage DC Charger (OUCH) 🤔
« Reply #3 on: February 12, 2020, 10:39:25 am »
Hi Noneya!

I see what you mean there. eBay is silly with these things so skies the limit on choice. If that brand is better I can find a seller that ships US. I just bought the 48v 15kw version like dochubert and have been experimenting stateside with the 24v version.

I am still want to try and make this work somehow being a stubborn old sailor and all. Question: your mains is L1~N 220v bonded at panel to earth is that correct? Philippines is bonded/grounded to nothing pretty much. Had to ship and drive my own 8ft copper rod so I would have and earth. The grid brings something resembling a neutral into the breaker box which shows 96v to L1 or L2 and still runs my grinding coffee brewer but only if I shut down the inverter and give back the grid. I don’t trust the grid there’s no grid tie no way.

I’m gonna order a welder and check that out too and see where that takes me.

Regards!
SN

Any day above ground is a day for potential mishaps

Offline noneyabussiness

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Re: High Voltage DC Charger (OUCH) 🤔
« Reply #4 on: February 12, 2020, 02:54:43 pm »
Thats correct, we have neutral and active, with neutral bonded to earth at the board.. it allows the safety switch to operate if there is a fault.

Don't quote me,  but im sure the states has " neutral " bonded to earth and L1 (110v) and L2 (110v) , sort of like our 3 phase.. but someone with actual knowledge may chime in here please..

Im sure there is a 110v version of these welders, honestly, ive bought a few for different reasons and all been pretty good. Most of the time they pretty much the same internally.

Another thought, you could use Oztules trick and add a motor start capacitor in series with your primary to limit current, but not sure if that will work with a transformer... again, smarter people please chime in ...

Offline rossw

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Re: High Voltage DC Charger (OUCH) 🤔
« Reply #5 on: February 12, 2020, 03:53:27 pm »
Don't quote me,  but im sure the states has " neutral " bonded to earth and L1 (110v) and L2 (110v) , sort of like our 3 phase..

They have basically a "centre-tapped 220V", with the centre tap being grounded (mostly, sorta-kinda, sometimes).
From the "neutral" as you put it, to either L1 or L2 thus gives you 110V (but opposite phases).
From L1 to L2 gives you 220V

It doesn't give you a nice way to drive 3phase motors. It pretty much gives you the "worst of all possible options" IMHO!

Offline Solarnewbee

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Re: High Voltage DC Charger (OUCH) 🤔
« Reply #6 on: February 12, 2020, 04:33:43 pm »
Hey Ross,

Pretty much. The xfmr on the pole is just like you said center tapped. 13,250v down to 220v L1 N L2. It would run 3 phase because the motor would just sit and heat up without a, phase shift?, I think so they install 3 phase pole transformers that tap 3 phases from the top line plus neutral and in some places they have a high leg which is like yours but 208v commercial rate to neutral. I found out about high legs the hard way and ran a new receptacle in a restaurant for a 120v cooler, spun the blades right off the evap motors, in pieces. Compressor protected itself, that’s how I noticed something was up. That’s when the inspector behind me says you forgot about the high leg didn’t you. Yep, like I knew 🙄.

Motor start cap huh? Interesting. I remember a discussion on here about 120v and a row of caps and HV charging fla batteries and the fallout thereof. I also remember my brain running away from that idea.

How about a Variac? Turn up the power a little at a time. As long as the Midnite controller doesn’t record a voltage over 150v they will replace for free. Ha!

Too much time on my hands I guess.

Thanks

Cheerios!
SN

Any day above ground is a day for potential mishaps

Offline Solarnewbee

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Re: High Voltage DC Charger (OUCH) 🤔
« Reply #7 on: Yesterday at 10:22:51 am »

Short Answer,

Some whom may have predicted this scenario is a NOPE! I did set up a 150r x 1kr divider for 144v. The Midnite immediately pulled it down to 59v and 1.9 amps. The 150r 100w got hot as hell even with heat sink and fan and was wanting to let out the smoke. I guess most of the current is lost as heat.

Experiment done.

I never could bring myself to remove the 470mfd cap and plug it straight thru the controller.

Adios Muchachos!
SN

Any day above ground is a day for potential mishaps