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Forum Index : Electronics : Power Voltage Up-Converter
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| Solar Mike Guru  Joined: 08/02/2015 Location: New ZealandPosts: 1138 |
Our temporary off grid project for a garden center is now running in limited capacity 24 volt form until the full project can be built and assembled into a container, which I'm still waiting to arrive, along with the 20 remaining 300 Ah 6V lead carbon batteries. At least we have some off grid power, managed to pickup a Honda DC generator for charging the batteries during cloudy weather, it has a 140 Amp DC 24V alternator fitted with a fancy Balmar microprocessor controller, all seems to be working fine and easily adjusted to limit charge current to 60a with the small number of temp batteries. However when the 48v bank is finally made up later next year I will require a higher output voltage and I don't want to pull the alternator to bits and alter it; so planning to make a high freq voltage power doubler using some large ferrite cores and HF rectifier. Basically an DC to DC H-Bridge HF transformer + rectifier stepping up the voltage to match the batteries. Thought perhaps a simple push-pull would work and it probably would, but uses more wire, so bigger cores are required, which I dont have. Thus the layout below, sorry no schema, I just built the pcb design as is, thought would just build a generic opto-coupled H-Bridge that can also be used as an inverter. 4 mosfets on each leg, they are mounted under the board on an alloy plate for heat sinking, each device has its own driver chip. Copper bars are soldered along the +- rails. Plug a cpu board into it to suit whatever function is required. Cannot wait to try out Poida's Nanoverter driver on it with a toroidal core. Bottom: Have colored some power nets to see better any errors. Size is 200mm x 146mm.  Top:  Cheers Mike |
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renewableMark Guru Joined: 09/12/2017 Location: AustraliaPosts: 1678 |
I have been thinking your plan would suit my place. I have a small off grid 24v set up in the shed. A 24v alternator could be fitted to my diesel stationary engine, then boost voltage to feed the big 48v battery. I wonder how 3 of these in parallel would go. Cheers Caveman Mark Off grid eastern Melb |
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| davef Guru Joined: 14/05/2006 Location: New ZealandPosts: 499 |
90V at 22A is about 1800W. I have some similar units and when you consider both the input current and output current "ratings" and the operating voltages I ended up with about 1/2 the power rating! In your case 24V times 40A = 960Watts. I have reverse-engineered my units so that I can control them externally. They will feed separate loads so I am NOT worried about them competing with each other as to who is going to deliver all the current. I see paralleling them as a bigger challenge. Dave |
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| Solar Mike Guru Joined: 08/02/2015 Location: New ZealandPosts: 1138 |
I did order one of those, arrived last week, havent tested it yet, one pot allows a current limit, so in theory multiple devices in parallel might current share. The device I received may run at the quoted current, but not for long I suspect, pcb tracks are quite light, coil wire isnt very thick, heat sink would be too small. I will see if I can blow this one up and report back... I have made the test PCB for my converter unit, now working on a suitable controller; actually designing 2 controllers, one for use as an up-converter charger using the HF ferrite transformer, the other for a small low frequency 24v-230 vac 2.5kw inverter using a small toroidal core, both can use the same H-Bridge power board, some of the mosfets can be left off. I have a small portable 24v 2.5kw HF inverter box powered by Lifepo4 batteries that I use off site to power various tools etc, however after purchasing a new drop saw a week or so ago, it wont run on the existing HF inverter, startup current kills it, so now I have to build another bloody inverter, its never ending, I will get the charger up converter going at some point... Cheers Mike |
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| renewableMark Guru Joined: 09/12/2017 Location: AustraliaPosts: 1678 |
Reckon one of these might be handy, I got a reply from them, it's rated at 2750w @48v output. Nice compact little unit. Cheers Caveman Mark Off grid eastern Melb |
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| Solar Mike Guru Joined: 08/02/2015 Location: New ZealandPosts: 1138 |
Good find, however US$320 to NZ + 15% GST + Customs import fees of $100 make it quite expensive, with possibly little quality control on the motor make it dubious at best. You can also buy $400 AC generators at the likes of Bunnings with about 3KW output, just bung a toroidal core with 65 VAC output winding + big rectifier would also work, reason we didnt go that way is again quality, I would only expect 100 Hrs use before the motor crapped out. The 24 vdc unit we currently have was a spare for the antarctic base, but never used, so should last many years, chews through the petrol though, a diesel generator would be preferable and less expensive to run. Cheers Mike |
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| renewableMark Guru Joined: 09/12/2017 Location: AustraliaPosts: 1678 |
Yeah NZ shipping..... ouch. Landed here total is $448 Aust dollar, pretty tempting. I wondered about the reliability of those things too but they are made for range extenders on electric taxi type vehicles, you would assume they cop a flogging in that type of use, so possibly could be ok???????? Doesn't look like it was aimed at our market at all, more for local drivers. I have my 9hp diesel rk9, but have to frigg around wiring an F&P and it still may not make enough, so may need a second mounted somewhere awkward, starting to become a bigger job than I thought it would. Might give Mad's idea a crack and test an unmodified F&P rectified through a GTI into the Madinverter. Cheers Caveman Mark Off grid eastern Melb |
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| Solar Mike Guru Joined: 08/02/2015 Location: New ZealandPosts: 1138 |
... they are made for range extenders on electric taxi type vehicles. Then reliability may be ok, guess, if its anything like my petrol lawn mover engine, gets a thrashing and finally threw a rod after about 10 years and probably only 2 oil changes in that time! If you went to the wreckers and got an old lucas 140A alternator or similar, removed the regulator block, bolted an external rectifier and supplied the field winding via a 12v light bulb, spun it at 10,000 rpm it would put out 60 volts or so, 100 amps. |
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| Solar Mike Guru Joined: 08/02/2015 Location: New ZealandPosts: 1138 |
Bugger, we had our 24v 140amp petrol DC generator stolen a week ago, bastards smashed down several locked steel gates, $80 padlocks cut with a grinder; so this project is now on hold permanently as I doubt we will ever see the generator again. Its going to cost 3K or more to replace it, so will probably get a diesel Genny (230 ac) instead, once we have beefed up security and electrified the fences, gates, locks with an electric fence unit. Mike  |
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mackoffgrid Guru Joined: 13/03/2017 Location: AustraliaPosts: 460 |
Jeez - I feel for you Mike. The bastards obviously knew the stuff was there, could they see it from the road. |
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LadyN Guru Joined: 26/01/2019 Location: United StatesPosts: 408 |
 OK, have you seen my thread https://www.thebackshed.com/forum/forum_posts.asp?TID=11075&PN=1&TPN=1 TL494 can be configured in master-slave configuration so it should be possible to paralleling them |
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