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Forum Index : Electronics : Rafael Inverter project (Poida Powerboard + Picoverter)
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InPhase Senior Member  Joined: 15/12/2020 Location: United StatesPosts: 178 |
California has a huge solar industry, so maybe call some of the local solar or electrical contractors to ask if they have any dead inverters pulled from the field. |
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Murphy's friend Guru  Joined: 04/10/2019 Location: AustraliaPosts: 648 |
I got mine from a solar installer, its usually not economical to repair these things so they sell them for scrap. The price you quoted above for a dead ebay inverter is ridiculous. The going price here for a dead 3KW inverter with a BIG toroid inside was $A50.- Try to get to talk to a solar installer, you may get a dead inverter for beer money. They often have other useful parts inside as well. Steer away from water ingress damaged ones, their inside is usually charcoal from the high Voltage DC arcing. |
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renewableMark Guru Joined: 09/12/2017 Location: AustraliaPosts: 1678 |
If you have the ability to buy more transformers I would buy three times what you need. I bet you $50 in 6 months you'll want more and the locals will have all sold out and you'll be searching all around for them. When good parts come along buy heaps more, you never know if you'll need them or you might meet someone that needs them. I have got 4008 from alowizic and also lcsc, both are fine. Cheers Caveman Mark Off grid eastern Melb |
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Haxby Guru Joined: 07/07/2008 Location: AustraliaPosts: 423 |
I agree! The scrap copper price in AU is $6 per kilo at the moment. Crazy times. There is a small risk that there is a design fault of some sort with them, why would they have so many identical ones ...., but even if you have to re-wind them, it's best to have a selection of identical cores to stack. |
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| flyingfishfinger Senior Member Joined: 12/09/2020 Location: United StatesPosts: 110 |
Well, I just got a nice surprise... A local solar guy gave me a working (!) Xantrex SW4048 for nothing:  Now I'm wondering (and the solar guy asked too )- if this works already, why harvest it for the DIY one? It doesn't have a toroid but I can get lots of goodies out of it (heatsinks, battery connectors, giant relays...) if I do though. Side note: He said it was bad to add more batteries to an existing system, because the old batteries would degrade the new ones more quickly - is that true? R |
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| renewableMark Guru Joined: 09/12/2017 Location: AustraliaPosts: 1678 |
F yeah, just use it as is, you'll need a 48v bank though. I found this vid on youtube I didn't watch all of it but you can hook up a generator input to it as well, so it has sync ability, very nice indeed. Go buy some batteries! And yes you should try and match the batteries. Cheers Caveman Mark Off grid eastern Melb |
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| Murphy's friend Guru Joined: 04/10/2019 Location: AustraliaPosts: 648 |
Yes, I would leave a still working inverter as it is. I got a 3 string input dead inverter from one installer, all that was wrong with it was the relays inside were faulty. At $1.20 ea on ebay it was cheap to replace them. I now use this inverter to 'backcharge' my 48V (nom) battery bank. Using high voltage DC from the solar panels is cheaper cable wise than connecting the panels in 48V 2S pairs. These torodial inverters we build have the ability to form a self contained mini grid with a standard GTI and if the GTI 'pushed' power into this grid the batteries get charged from the home built inverter. (in case you did not know this  )All that's required is a battery voltage sensing relay to turn the GTI's AC connection off as the charging from it is completely un regulated. |
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| flyingfishfinger Senior Member Joined: 12/09/2020 Location: United StatesPosts: 110 |
The oldest battery is ~ 1 year old, the 2nd is 6 months. Both have hardly been used (we've only been out there 3 times this year) so I hope it's not too late to add 2 more. I guess this also answers the original purpose of this thread if the thing works properly ... thanks everyone for the help! If I need to DIY an inverter in the future I know where to look. The good thing is now I have one project less to build this summer - saves me time and $$. I still need the MPPT though, and Peter's project there looks good. I shall start a thread for it. Cheers, R |
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| nickskethisniks Guru Joined: 17/10/2017 Location: BelgiumPosts: 458 |
You could use something like this: https://www.banggood.com/BE48-48V-Battery-Equalizer-Solar-System-Balancer-with-Reverse-Connection-Protection-Energy-Supplies-p-1782292.html I use that on my batteries to keep the voltage over the 4 batteries the same. It's working great, but when using heavely mismatched batteries this will not be enough. |
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| flyingfishfinger Senior Member Joined: 12/09/2020 Location: United StatesPosts: 110 |
Hmm actually, I can't build a 48V system just yet. I just remembered that our little PV system runs on Victron BlueSolars which cannot charge 48V batteries, just 12V and 24V. That means until I get / build a 48V MPPT I can't really use the new inverter. Food for thought... R |
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| renewableMark Guru Joined: 09/12/2017 Location: AustraliaPosts: 1678 |
If I were in your shoes I would say OK I need power for tools and to live while I am up at the cabin. I need it quickly. I have a working inverter. But I need 2 more batteries and a 48v charge controller. So basically to get yourself running just buy 2 more batteries and an off the shelf controller for now, you can build something to add later. You could buy all the bits you need, go to your cabin on the next trip and set it up. Boom, move on to next job. like this or a pwm Cheers Caveman Mark Off grid eastern Melb |
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| flyingfishfinger Senior Member Joined: 12/09/2020 Location: United StatesPosts: 110 |
We have two trips coming up. First one in a month, probably will be OK with existing 12/24V & BlueSolar situation. Second one in August, we will be up there for 2 weeks and that's when the power tools will be needed. I feel that should be enough time to make one of Wiseguy's MPPTs. I'm also sort of itching for a fun DIY project :) But yes, if I needed the power tools next week I would 100% go with the above options. R |
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| oreo Regular Member  Joined: 11/12/2020 Location: CanadaPosts: 49 |
FWIW, I see some vendors selling this transformer with electronics on the board. For example Low power isolated transformer with electronics for voltage sense. I am going to buy a couple to see how they work. Greg |
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wiseguy Guru Joined: 21/06/2018 Location: AustraliaPosts: 1156 |
When I was investigating this stuff ~ 18 months ago I found a schematic which I believe is what those modules used. They are certainly cheap enough but their other issue for me was that they still output AC. The gain/level can be varied but it would have been nice if there was a DC level output module - I couldnt find one when I looked. The modules input resistor on the AC input looks like a standard 0805 which typically only has a maximum voltage rating of 150V RMS or DC. Ok for 110VAC but it worried me for 240VAC. Here are 2 schematics I found which may be of use to you. The LHS R6 (first schematic - 2 x R6's lol) is missing from the second schematic and I'm not sure if it will work ok without it.   Edited 2021-07-24 09:48 by wiseguy If at first you dont succeed, I suggest you avoid sky diving.... Cheers Mike |
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| oreo Regular Member Joined: 11/12/2020 Location: CanadaPosts: 49 |
Great info, thanks Mike! Greg |
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