HI Ed,Hi Spec, did some more tests on it, I connected the extra battery to give me 4 in total and connected the transformer via the bridge rectifier on its own with out the capacitor, and here are the results:
DC V across the end terminal posts gave me 53.2V at the start which rose to 53.90V after 25 minutes of run time (13.375 V/battery). V at the 3rd battery went from 40.1 to 40.5V this is without any load on the batteries and the temp of the transformer frame went from 33C to 38C in an ambient of 26C air temp.
So now I need to find something that will suck out 40A @ 36V out of the 3 batteries and then measure the voltages. So overall I don't think that it is too bad assuming that the 100Hz rate of the charging voltage won't interfere with anything on the heater module or the extra ).5V, which I can't test for a while till I repair the module.
I already have a 32A circuit breaker installed but will swap that to a 40A when I get one, I know I have one some where in the shed but finding it could be a bit of an issue.
The only other "transformer" that I have that is capable of that amperage is my large inverter MIG welder which I can select from 10V to 39V DC in 0.1 of a volt, however there is a problem in that is has a voltage spike which is about 75V for a very short time just before dropping down to the required set voltage. The main problem is using it is, that if something goes wrong and I short something the MIG will vapourise what ever it is powering as it will supply about 24Kw instantly at that voltage. Ideally a variable voltage power supply unit would be ideal as I could also use it to power other little projects I had in mind. and I had thought about using the MIG to do this, but had the spike issue to deal with and the worry of a short circuit.
I see a lot of worrying about theoretical ideals based 'what ifs' and very little reality and practical logical approach being applied here.
The blown Mosfet were the result of me not paying attention and occidentally contacting the bottom of the circuit board to my steel table which shorted the lot, with lots of big sparks and and a big bang. It was working well up to that point.
So what is so difficult about hooking the MIG power supply up to the batteries or the induction heater circuit a few seconds after the start up spike drops off?
I see a lot of worrying about theoretical ideals based 'what ifs' and very little reality and practical logical approach being applied here.
Hook you MIG power supply up to your battery bank turn it up to 39 volts and activate it. I guarantee the 75 volt start up spike that happens for a fraction of second won't do a damn thing to the batteries ever unless they are junk to begin with then hook up you induction heater driver circuit.[/QUOTE
tcmtech, I am new to fairly new to electronics with no knowledge except what I pick up, and while you are correct in that I may be worrying about nothing and no damage may occur, however until I learn more about it I have to be overly cautious about what I do especially if one of the items contains sulphuric acid and there are huge amps involved, which can heat up and destroy something by vaporising it in an instant if something goes wrong. Now you are free to express your view as as I am to do likewise, but for me I believe in being a bit more cautious and safe then sorry! Incidently the MIG I have has melted through 19mm steel plate in about 1 second and that was at half power! 39V would be full power.
I do not want to end up with a "Darwin Award" with the title "Guy burned and killed by blowing up batteries with a MIG welder" Sure it may not happen and I may have worried needlessly, however if it does then I may have saved myself from getting an award. I prefer to take baby steps and keep the risks to a minimum. After all this is just a new hobby for me.
You may be willing to take more risks but I am not, but that is my prerogative. I need to learn more about this before taking a gungho attitude about doing things as I don't have the benefit of knowledge to guide me, as this is forum with lots of different levels of experience and knowledge, and I am no stranger to different forums. I know that on all forums there are members which are very knowledgable and there are some who just talk waffle, so don't take offence if until I work out who is who, I am not about to take just your word or your "guarantee" that it is safe especially if I perceive a potential danger, as in the possibility of superheated rapidly expanding sulphuric acid accompanied by a loud bang!
So in the mean time if you don't like my methods or worrying then feel free to ignore my posts. As for myself, I will listen to what everyone writes and make a decision based I what I feel comfortable with. Fair enough?
Making a short circuit on a power circuit is a rite of passage for an electronics experimenter.
As long as you don't electrocute or burn yourself, components are just that, components which can be replaced.
but for me I believe in being a bit more cautious and safe then sorry! Incidently the MIG I have has melted through 19mm steel plate in about 1 second and that was at half power! 39V would be full power.
Back in the old times people put fuses in their experimental circuits to prevent that from happening and the really creative ones put in big power resistors to limit the current instead or as well.
Wanting to half ass it out of cheap salvaged miss matched parts and then worrying about safety is counter productive so either build it right or don't build it at all.
As far as shorting things out and killing yourself with it you do know what a welding power supply is designed to do on purpose while its electrodes are in your hands right?
I can respect due caution to a point but there comes a point where it's time to either poop or get off the pot which means at some point you either have to let go of that security blanket of theory and what ifs and take that first step and trust that those who went before you obviously didn't die from it or just abandon the project and let 'what if' rule your life unimpeded by the reality of what others do without a second thought.
I don't mind discussing them but at some point a guy has to pick up some parts and tools and just do something with them to confirm or dispel their concerns before any further discussion of the concept or project can continue.
1) That would be good if I knew what size power resistor to use and I did have a circuit breaker in place from the battery to the heater, unfortunately that wasn't where the problem was, it was from shorting out the circuit board on the steel bench and the power came from the onboard capacitors. I did say in my first post that I was a newb and so I have a little bit of knowledge , probably enough to be dangerous, hence I posted on here to get the advice from more knowledgable people, the more I learn, the quicker my methods will become but it will be at my own pace.
2) As for wanting to half ass things out of cheap parts ect. I may be using used parts, that doesn't mean they are cheap and isn't that what a hobby is, making something out of something else? At least I do, I enjoy recycling things and converting them into something else which is useful to me.
3) As for the welder, I do know how it operates as I have been using them for over 40 years and I have a healthy respect for the stored and readily available power coming out of them.For the record it is a MIG so it doesn't use electrodes as such and uses a continuous coil of wire and operates in a different fashion to an "electrode welder". So I am not worried about the MIG, just the sudden massive influx of energy into the batteries which can cause a rapid temperature rise which may cause them to explode showering me with super heated acid, that is the part I am concerned with, and as accidents can and do happen I do not want to find out the hard way.. ooops I should not have done that. I have seen a large capacitor destroy itself before any fuses tripped and I do not want to find out the hard way if batteries do the same. This is especially true with my limited knowledge, as I said the more I learn the more confidence I will have to do these things but I am not going to be rushed!
4) As for "those going before me "ect. I did some research and couldn't find a single entry where someone had connected up a MIG to a set of batteries, so I am not going to try and nominate myself for a Darwin Award.
You may think of me as being overcautious and it obviously annoys you, you have the right to your opinion and you are welcome to it, so now that you have stated it a couple of times and I have posted my views lets leave it at that with out it getting personal. I don't think that it is productive to continue these sort of posts, so if you have something constructive to say in this post I am willing to consider it otherwise......
But that is the very point TCM. That is TCM's point of view and personal things have no part to play in a design. If you get bored/frustrated/annoyed by a particular post, you can do what most of us do and exit. After all, there always many threads on ETO that you could develop and would benefit from your experience.
spec
What I see is people coming here wanting advice on how to solve a problem then not doing anything because they're afraid to apply that advice to the actual problem they have so they just dig up more largely irrelevant 'what if's' to justify not actually doing anything to solve their problem they came here for.
By nature I am a doer not a what if'er. When I see a problem I figure out how to solve it and I get back to doing what it was I was going for. I don't keep digging for more what if based scenarios to justify not moving forward towards my goal.
The OP here want's to reduce the output voltage of his salvaged power transformer to work within the range he needs. I posted a very workable and cheap solution on how to do that by converting a common battery charger transformer into a autotransformer to buck the input voltage down to where he wants.
No replies or discussion came of it so I take it that either it was never read, never understood or that an actual working solution is not really what's wanted.
I've also posted multiple comments on using the welder power supply and how to get around start up surge issue that seems to be such a high level concern despite every bit of information I can find on the subject saying that when its connected to a battery bank it totally irrelevant because the energy magnitude and time duration is to short to be of consequence.
So what up with that? Not read, not understood or what? Is at worst turning the power supply on then waiting a few seconds before connecting it to either the battery bank or load or both an insurmountable problem?
As for the rest of the threads on the site I don't post where I see no point worth contributing my knowledge or experience. Either I have no solution, someone has already given a workable solution or the OP is in so far over head head I don't can't do a thing with their problem.
In the case of this thread I initially saw something that related well to my life's experiences being I have worked with high power industrial electronics such as welders and high capacity battery banks all my life and thus have a comfortable familiarity with what they are capable of doing and to what limits they can be run.
For me tens of volts at hundreds or even thousands of amps just makes a lot of sparks when things go wrong. It's too low of voltage to realistically electrocute anyone, even standard electrical codes agree with that, and at worst the current can cause burns of various sorts of which all are easily avoided with the most basic of protective gear.
The rest is just the the scare factor behind the sparks and easily overcome when what is happening is understood.
Same with the batteries. Its extremely unlikely to near irrelevantly possible that one will blow up for any reason even if abusively over charged for some time and even then a good heavy wet towel over a battery goes a long way towards preventing any severe acid spewing explosions for going anywhere.
That what I see here. Too many basic issues that are easily solvable and avoidable just by using the most basic efforts to understand them and use that knowledge neutralize them against even the worst case scenarios.
When I learn new things and I have experienced people to teach me and they say don't worry about something I tend to make an effort to believe that they have reason to not feel concern about something even if initially do. They have been there done that and know things I don't yet.
As for me getting up tight aobut things I think some people read way too much negativity into what isn't there to begin with and that's not a problem I can solve either.
All valid points by TCM, SPAC and Ed.
However, consider that designing something to the nth degree is a good principle, but when the item is finally built and put into service, there is still the "Oh, I never thought of that!" which detracts from the overall usability of the item.
What I often do when I am building something which I have never done before, after doing the initial design calculations, I build a prototype and try it out.
That way I can evaluate the design and refine if necessary, or, tidy it up and use it as is, or as is often the case think "What a bad idea that was! I will never do that again!" and consign the prototype to the "junk box".
When NASA built the Apollo project, they did not just design it, build it and fly it, they had numerous prototypes and I am sure that many of them were just quietly pushed into the corner and never spoken of again.
So, is it time in your project to make a prototype or proof of concept test system ?
JimB
This thread is getting way off the objective of doing what the OP wants and is turning into the TCM show again.
You can argue anything by assumptions, generalizations and morals.
For example take your point about adding another transformer, I had already mentioned that and the OP had said that he did not have another transformer.
Lets get back to electronics.
To be honest, that's largely part of why I, and quite a few others, dropped off this forum and either outrightly left or went into the shadows. I and many others enjoy doing things and helping others to do the same but it's largely unwelcomed when it goes beyond actually 'what if' ing something to death opposed to doing it and it just turns into a meaningless fight in the end.
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