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Marcus20VT Regular Member Joined: 02/09/2008 Location: WalesPosts: 49
Posted: 09:32pm 07 Oct 2008
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Hello - am I being a bit thick here ??
If I wanted to power a 12V 600W heating element with an external power source, say a wind turbine, I would need;
a battery able to supply the load ie 12V, (600/12=50 A/h at least, or would this need to be bigger to supply 600W continuously?)
a charge controller to regulate power from turbine and charge battery - does this have to be also rated 50A, or do I take the load from the battery as well, or take the load from the charge controller (as this is what happens to my solar lighting in the shed via that charge controller)
Usual isolators, fuses, cable and connections - 50A current carrying capacity.
Anything else?
Sorry if this is a really dumb question
Robb Senior Member Joined: 01/08/2007 Location: AustraliaPosts: 221
Posted: 03:57am 08 Oct 2008
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If the wind blows 50% of the time over a 2 hour window and the batterys are 100% efficient then the mill would need to charge at 100 amps requiring 50Ah* batterys if the wind stops totaly for the second hour.
Wind:
25% of the time = 200 amps.
10% of the time = 500amps
Things aren't that simple in reality however:
Battery inefficiencys
Discharge current at which battery amphour rating is quoted
Safe discharge levels
Wind site surveys
Unexpected wind levels outside those found in the site survey.
*Edited from 600Ah. I was thinking watt hours.Edited by Robb 2008-10-10
Gill Senior Member Joined: 11/11/2006 Location: AustraliaPosts: 669
Posted: 10:49am 08 Oct 2008
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(600/12=50 A/h at least, or would this need to be bigger to supply 600W continuously?)
For your battery to last it is best that you don't cycle it much more than 90% to 80%. In your calculation you are cycling it to 0. A 50Ahr battery will not actually deliver 50Amps for one hour exactly then in the next second be dead flat. It is a guide really. Start looking at well above 500Ahr then re read Robbo's post and start adding, adding and more adding.
Gill EDIT: 'cycling to 100%.' corrected to read 'cycling it to 0.'Edited by Gill 2008-10-12was working fine... til the smoke got out.
Cheers Gill _Cairns, FNQ
Marcus20VT Regular Member Joined: 02/09/2008 Location: WalesPosts: 49
Posted: 08:46am 09 Oct 2008
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OK Point taken - thanks.
Trouble is that as I'm a sparky, I keep thinking there's a continuous supply of energy which there just isn't with wind generation Has anyone used relays before to switch the load on and off with relation to the charge on the battery.
i.e it can be wired that when the battery is fully charged the load is switched on, then wired to a timer so that it switches off after an hour, then when the battery is charged fully again, it is switched on again, etc. etc.
Surely there must be components that we can use from the automotive sector?
I am curious as to the reason you are needing continuous hot water - is it for washing or heating?
What size tank of water is being heated and how many degrees?
From what temp to what temp?
Or is it just a voltage dump?
Just curious. Edited by Clive 2008-10-12
Gill Senior Member Joined: 11/11/2006 Location: AustraliaPosts: 669
Posted: 03:43am 11 Oct 2008
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Yes herbNZ does something like this. His is for load dumping via 240V appliances when the battery is charged and likely turns off at a hysteresis battery voltage though there is no reason it could not be connected via a timer if that is your preference. Search Herb's old posts for 'smart relay' I think it is to see his description of the 'off the shelf' building blocks he used. was working fine... til the smoke got out.
Cheers Gill _Cairns, FNQ
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.
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