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newbie-from-pa Newbie Joined: 20/06/2008 Location: United StatesPosts: 8
Posted: 01:52am 01 Aug 2008
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Greetings to All,
I would like to use a heater element for the diversion/dump load from my c60 controller after my battery bank is fully charged. I have a 12 volt, 1000watt wind turbine. I would like to know what wattage the heater element should be. Please advise. Thnaks.
Gill Senior Member Joined: 11/11/2006 Location: AustraliaPosts: 669
Posted: 03:51am 01 Aug 2008
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Easy, 1000watt or more.
You need to dissipate up to the full output of the generator. Seems a lot doesn't it but that's the go.
Be aware that that wattage will be at your float voltage.
You will need to calculate what will be suitable as it's likely heating elements sold as 1000w will be for other voltages, say like your 110v mains power and this is not suitable. Ohms law is the key.
Does that help? was working fine... til the smoke got out.
Cheers Gill _Cairns, FNQ
Dinges Senior Member Joined: 04/01/2008 Location: AlbaniaPosts: 510
Posted: 11:43am 01 Aug 2008
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You need a 12V heater of at least 1000 W.
I don't recall seeing one, I do have a 12V/150W car heater that I use as a large testload on occasions. 6 or more of those in parallel could do the trick.
I'm not familiar with the specifications of the C60, but 1000W at 12 V means that a current of 83.3 A (P = U * I; 1000W = 12V * 83 A) would flow. Make sure that the charge controller can handle 83A without letting the magic smoke out.
According to Ohm's law, U = I * R ; 12 = 83.3 * R; R = 0.14 ohm.
So the heating element should have a resistance of 0.14 ohm or less. This is *very* little. Make sure the C60 can dump loads into such a small resistance, as the internal resistances of the C60 may be much larger than those of your dumpload and thus the C60 would dissipate much of the heat and not the dumpload. And that is bad.
oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686
Posted: 12:09pm 01 Aug 2008
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If the c60 has difficulty with this current, or you have a problem finding suitable loads at 12v, 1000w inverters are only 50 dollars over where you are (US), and an old 1000w 110v radiator will do the same thing.... you should be able to remote control the inverter from the c60.
This is one of those occasions/applications where a modified sine inverter will perform as well as a pure sine inverter.
.............oztulesEdited by oztules 2008-08-02Village idiot...or... just another hack out of his depth
Dinges Senior Member Joined: 04/01/2008 Location: AlbaniaPosts: 510
Posted: 12:23pm 01 Aug 2008
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This would work if he can't find or build a suitable dumpload (12V @ 1000 W), but it's definitely not a solution to overcome possible current limitations of the C60: the C60 would still have to supply 83A to the inverter if the inverter needs to invert 1000W of power to supply the dumpload. 1000 W is still 1000 W, and it all needs to pass the C60.
...unless you've figured out some OU scheme which you neglected to inform us about...
To the original poster: are you beginning to see why people use higher system voltages for larger systems ? At 48V, for 1000 W of power the current would only be a much more manageable 21A.Edited by Dinges 2008-08-02
oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686
Posted: 09:13pm 01 Aug 2008
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No Peter,
The inverter is connected directly to the battery, but remotely switched via the c60's dump facility.
The C60 need only dump to a switch relay which turns on the inverter... which is connected to the batteries independant of the C60.
The C60 may see a few miliamps, the inverter will see near 100A
I'm keeping the OU plans secret for now. (but I think it involves a herd of soaking wet elephants, some over-ripe lemons and ..... no I have said too much already...)
....... oztulesEdited by oztules 2008-08-03Village idiot...or... just another hack out of his depth
Dinges Senior Member Joined: 04/01/2008 Location: AlbaniaPosts: 510
Posted: 09:31pm 01 Aug 2008
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Ah. That would work, yes. I missed the 'remote control' part in your previous reply.
So, use the C60 just as controller. Clever. He'd still have to find an inverter that can be remotely switched. Or he could perhaps simply let the C60 with relay control the 110V or 220V output of the inverter, if the standby current of the inverter isn't too much of a load for the battery. Switching the low voltage DC input would be a possibility too, but he'd need a heavy duty contactor and wire several decks in parallel to get the ~100A rating he needs. Switching the high-voltage output of the inverter would probably be easiest.
I have another problem with this setup though, and that's the reliability of the inverter; if anything happened to the inverter (they're electronics and can fail), he'd face a runaway mill if the battery was fully charged (or would be overcharging the battery; I don't know how the C60 works exactly). Inverters can and *do* fail. I recall one of Bruce failing recently.
Edited by Dinges 2008-08-03
oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686
Posted: 10:42pm 01 Aug 2008
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Yes Dinges,
The C60 under load has every where near as much chance of failing in dump mode as the inverter, or even a dump (Ghurd) controller would.
The advantage here is that the inverter is only driving a straight resistance load, and so the inductive spikes which usually cause the demise of the inverters, is not there. Soft starting a resistive load is the kindest way of treating switching electronics, so if any thing were to survive it would be this system.
It is improtant to remote switch the inverter, as this mitigates the shock start of switching in full load instantly via other switching methods.
As a rule, all inverters are capable of remote control, simply put a N/O relay in parallel with the switch on the inverter. The relay can be controlled by a "Ghurd" or the C60). This will allow remote start with all the safety features of turning it on normally. (usually has post check and soft start).
Like I said, a resistive load on the inverter is as kind as it gets. If it is going to survive, it will be in these circumstances.
The chances of extended periods of 100A loads are unusual events (unless your in Jamies location), but in event of a failure, the batteries still provide the load to prevent runaway. Jamies has pulse width dump control, so has the same inherent failure problems as all electronic stuff.
As an added extra, you could also "interfere" with the feedback system in the inverter, and control it with the dump converter you built. Use the incremental voltage increase to fool the pwm driver in the inverter to control the power step up stage (the push-pull 12v stage) and you then have a variable 1kw dump load for 50 bucks.
If you are paranoid, another relay and a second 50 dollar inverter interlocked to the output of the first, could build in redundancy for just such an occasion..
...........oztules
Village idiot...or... just another hack out of his depth
Dinges Senior Member Joined: 04/01/2008 Location: AlbaniaPosts: 510
Posted: 11:13pm 01 Aug 2008
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Thanks, I learned a few new things in this thread. I hope the OP was helped too.
And yes, I'm paranoid. Or rather, mr. Murphy likes to visit me on occasion.
He could of course also get 4-5 automotive relays that can handle 30 A and drive the coils of them with the output of the C60. Or use a car starter solenoid. Use the relays or solenoid to drive a few heavy loads, perhaps H4 car headlights in parallel (55-60W each) or several 12V/150W car heaters. Or perhaps a 12V water heater, the kind that you can put in a cup.)
The downside is the wearing of the relays (arcing/pitting of the contacts) in this case, but it seems to me the easiest (low-tech) solution and relatively cheap too.
Of course, another question is whether his generator can *really* put out 1kW or whether that is a marketing figure. If in a real-life situation his genny puts out, say, 500(*) W maximum in a blazing gale, everything could be controlled easily by the C60. Actually, part of me thinks (hopes ?) that the C60 may just be able to handle the 83 A... If it were mine I'd research this a little more, and whether the genny would ever really put out 1kW.
(*) on closer thought, at 13.8V and 60 A the maximum power the C60 could handle would be 830 W. At 14.4 V it would be 860 W. This would be the absolute maximum that the C60 would be rated for (if it's really 60A max), and is getting pretty close to the 1kW the OP's mill is (marketing) rated for...Edited by Dinges 2008-08-03
oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686
Posted: 02:36am 02 Aug 2008
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Yep, the downside of dump loading is that everything will be under stress at this time (usually strong winds then).
This is why I am going to use the Southern Cross furling system. Seems to make life simpler.
It will also be power driven by the dump control at some later date. Fully auto and default fully furled on power loss. (small air ram with air held on via relay. Loose power relay drops, furls up fully..... to keep Ron happy)
.......oztulesVillage idiot...or... just another hack out of his depth
I just signed up today and I have to say this is the most informative site around ,also the amount of photo's is great,as a picture is worth etc,for a beginner like me.Your suggestion for the inverter is just what I need,would it be cheeky of me to ask you if you could show a scematic of the connections (or a photo) to the batterys and the relay type that I should buy for the connections,wire size and type of remote switch I need to get.my small hydro has a 2200w 24v pmg producing about 80a (if it ever gets going) turned by a waterwheel,it can hit 450 rpm geared up with pulleys.I have a numax 2500w inverter and a c60 and the idea to use 2 inverters is what i had in mind as the holy grail is to heat my cottage which is 125 yds away,using the diversion load from the c60,ambitious I know.I would be most grateful IF you could help me with it.
p.s.on mp3car.com there is a remote switch and pictures on how to connect it into an inverter would this be ok ?
Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.
Print this post
,also the amount of photo's is great,as a picture is worth etc,for a beginner like me.Your suggestion for the inverter is just what I need,would it be cheeky of me to ask you if you could show a scematic of the connections (or a photo) to the batterys and the relay type that I should buy for the connections,wire size and type of remote switch I need to get.my small hydro has a 2200w 24v pmg producing about 80a (if it ever gets going) turned by a waterwheel,it can hit 450 rpm geared up with pulleys.I have a numax 2500w inverter and a c60 and the idea to use 2 inverters is what i had in mind as the holy grail is to heat my cottage which is 125 yds away,using the diversion load from the c60,ambitious I know.I would be most grateful IF you could help me with it.
