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Forum Index : Electronics : Inverter building using Wiseguys Power board and the Nano drive board
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wiseguy Guru  Joined: 21/06/2018 Location: AustraliaPosts: 1292 |
Toroidal Transformers are not something I have much experience with especially with correct design values so maybe treat what I am suggesting with a grain of salt. My calculations of your cross section are 45 x 120 or 5400sq mm ? If I apply Oztules law, I understood that he said 2800sqmm = 1T/Volt, so your turns per volt should be 5400/2800 = ~1.9286. You used 118 turns which suggests an output of 227.57V ? He also suggested for lower flux that you should calculate for a 240 - 260V secondary when your desired output is 220V which is somewhere between 9% & 18% more turns. Using that theory if we assumed your 227.57 volts was the correct target your secondary turns should have been ~133T if I use 13% more turns (half way between the suggested increased turns%) ? If you have access to a proper wattmeter why not disconnect the transformer from the circuit and check its power draw from the mains (118T winding!!) - do not use RMS Volts and Amps calculations as they will be a long way from reality due to the inductive phase shift involved. That would be a good starting point. Whatever don't get distressed if the answer is a lack of turns. although not ideal you can add a few primary and secondary turns as required and still make it come good. Or maybe someone with real winding experience can chime in and give you more correct advice. Alternatively a quick test might be to adjust your output volts to around 200-205V and tell us what the idling current now is with the 12T chokes. I think the combination of choke inductance a bit low and transformer not at optimum is causing the high idling power? Edited 2026-05-27 09:57 by wiseguy If at first you dont succeed, I suggest you avoid sky diving.... Cheers Mike |
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phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 3248 |
That is correct. Optimum Turns / Volt is a compromise that depends on usage requirements. More T/V = lower core loss, which is there all the time, but the extra resistance increases loss loss in the windings at high power. A transformer intended for a particular piece of equipment may spend most of its time near full power so you aim for lowest loss at full power. If that is what the maker thought it was for then that is what he made. A domestic inverter usually spends little time at full power so low idle loss is more important for minimizing total energy loss. |
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KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 2153 |
The other option, I think wiseguy mentioned, even if you only have one spare core of some type, wind enough turns around it to get another 20uH or so and connect it in series with one of the Inverter chokes, as you are only testing at idle, it should tell you if you need another turn or two in the existing chokes. NANO:Inverter V 8.2ks - Linux AvrDude GUI script V4.1 |
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| KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 2153 |
I finally finished transferring my 16 cell LiFePO4 battery banks into the Vertical Battery boxes I picked up the other day. These boxes weigh 23kG empty, the weight is 120kg with the 16 cells. They are beautifully made, white in colour, and come with four 520kg rated castors with a large red dial wheel that drops 4 hard rubber pads onto the floor, raising the rollers and locking the cabinet in place, very very stable. When I rebuilt the banks, I had my new FNIRIS battery internal resistance meter to help check every terminal and bus bar connection. Most cells are six year old Fake EVE cells, mixed with some Genuine EVE cells, they were all exactly the same internal resistance across the 64 cells. Including one 16 cell bank that is only 2 years old with Genuine EVE cells. I replaced the stupid connection screws on the older cells with new stud threads. I'd bought the threads 4 years ago for the day when I would finally rebuilt them. I also had four spare unused 4 year old cell, I only needed to replace one cell due to a stripped terminal thread. The difference now is amazing. Today I finally had the boxes installed, just as the SUN finally come out, the charging current is now exactly the same between all banks to within a 100mA with a 160A total charge current, I limit bulk charge to 40A per bank, and I've never seen them track like that. They tracked that way all day long, again never seen that before, at the end of the day, the cell voltage deviation across three banks was under 7mV with one at 15mV, but that bank had the replaced cell, and that cell was the one slightly low, so it will take a few days to balance out, and it should come down to 5mV as well. The same results show up when discharging. Looks like they will easily outlive me  NANO:Inverter V 8.2ks - Linux AvrDude GUI script V4.1 |
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Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 1265 |
That all sounds really good  , Whats the terminals on the battery box? I have recently been looking at some and a few are just brass while others state that they are copper some of the smaller pass through terminals are just plain brass round terminals.The 4 I have on the inverter are square base 30mm copper pass through with brass stud and embedded nut, the only one I did see the same was the eel battery square terminal, Or I might just make something like the one. Well done getting it altogether and running sweet.  Cheers Aaron Off The Grid |
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| KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 2153 |
Thanks, the terminals are 35mm square housing pass through, two neg and two positive with bridging bars, nice big clip on covers, these are similar to some EEL boxes, every thing is smooth, no sharp edges, very tough finish, thick fibreglass sheeting sets for insulating the cells and lining the compartments, very happy NANO:Inverter V 8.2ks - Linux AvrDude GUI script V4.1 |
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| analog8484 Senior Member  Joined: 11/11/2021 Location: United StatesPosts: 201 |
That sounds like pretty beefy boxes. Can you share some pictures? I am still uncomfortable with the idea of large always running battery banks attached to the house/garage ... especially when I am not home. After seeing this (https://www.youtube.com/watch?v=6LbBryib8yY) now I am thinking explosion resistant but vented enclosures are necessary in case of rare but high impact battery failures. |
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| KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 2153 |
I've got a few pictures coming I didn't watch the video, but I've seen it referred to many times, that explosions could only be caused by vented gas in a small confined space, possibly combined with high storage temps: Gas from a vented cell(s) likely combined with high current charge / discharge cycles, just because the data sheet says the batteries can charge or discharge at X amps, doesn't mean you should blindly do that. OR in this case abuse from a faulty BMS? If a BMS fails, a cell won't suddenly fail, the system should be checked every few days in any case, it only takes a minute to check a functioning BMS and Cell delta, or a net connection to check if away. This is almost unheard of, especially considering the amount of LiFePO4 installed, and of the very few that have been reported, most were poorly set up, abused, and a disaster waiting to happen. This is why I limit solar charge to 35% of rated charge current and charge voltage to around 3.38V per cell, not 3.65v, that leaves a few hours of tail current before you even get near 95%, cells are usually around 90% SOC, and top balance once a year. . Edited 2026-05-31 14:14 by KeepIS NANO:Inverter V 8.2ks - Linux AvrDude GUI script V4.1 |
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| wiseguy Guru Joined: 21/06/2018 Location: AustraliaPosts: 1292 |
Just a quick post your battery boxes and setup sounds nothing short of amazing. I do think you should look at the video and listen to the preamble. The Guy who set his system up was very cluey and took a lot of care etc and only one small issue that I dont know if even a ventilation fan would have helped got him. If at first you dont succeed, I suggest you avoid sky diving.... Cheers Mike |
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| KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 2153 |
Thanks, when I get the time I might have good look. I'm not dismissing him, just that I've heard this video dissected so many times, and attempts to create an explosion like that have basically failed, even purposely abusing the "absolute crap" out of a LiFePO4 cell. However, they all agree that under the "exact ideal failure conditions" you could get a vented gas explosion, but I'd take my chances with my battery bank over living with an ageing gas main under my house any day. I note that some battery manufactures are apparently fitting spark generators in the housings, harmlessly igniting any vented CELL gas before it can build to a large explosive volume, that's apart from the specialised high volume vent fans and gas detectors others use, but these are usually large industrial battery cabinets. Where is my old electric fence zapper. . Edited 2026-05-31 15:43 by KeepIS NANO:Inverter V 8.2ks - Linux AvrDude GUI script V4.1 |
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