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Author Topic: 48v inverter/charger  (Read 7828 times)
jhinshel
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« on: June 21, 2010, 09:22:55 PM »

In order to interface a 48v wind generator to my off grid system I need a 48v inverter. This is a bit annoying for me because my system is 24v. The inverter at the moment is a 24v outback vfx3024 which is really great. This cannot be upgraded to 24v easily so a new inverter is required. I am thinking of going for a sunny island 5048, but these are expensive bits of kit. I am keen on the sunny island because you can have a use variety of power sources unlike the outback which utilises either the batteries or the ac input.

If you have experience of 48v inverters or useful advice I would be grateful to hear it.

Regards,
Justin
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off grid 4 years: 2.5kw pv,sunny island 5048, 2 mx 60s, proven 2.5 48v, home made charge controller, 1500Ah fork lift batteries, 60 evacuated tube solar heating, vigas 40 kw biomas boiler, 3000l thermal store
Justme
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« Reply #1 on: June 21, 2010, 10:00:11 PM »

You could use a 24v wind charge controller with your 48v turbine & keep the system all 24v.

The power curve does alter & it lowers the start up wind speed & reduces the top end power.
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FX80 Solar controller
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stephendv
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« Reply #2 on: June 22, 2010, 05:15:43 PM »

Or you could use an MPPT charge controller to down convert the 48V output to 24V.
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Justme
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« Reply #3 on: June 22, 2010, 05:41:22 PM »

Or you could use an MPPT charge controller to down convert the 48V output to 24V.

It will need altering to closely match the power curve of the turbine.
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Navitron solar thermal system
30 x 58mm panel 259L TS
1200watts solar 120vdc
FX80 Solar controller
Victron 12v 3000w 120a
6kva genny
6 x 2v cells 1550amp/h 5C
24 x 2v cells 700amp/h 5C
Total bank 4350 amp/h 5C
jhinshel
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« Reply #4 on: June 22, 2010, 06:40:42 PM »

If the wind generator is locked down to 24v won't the speed of the generator be greatly reduced? This will have implications on the efficiency of the generator. Also, the current in the windings will be doubled and could easily exceed the accepted operating limits.

I could use dc-dc converters perhaps in an mppt controller. There is not a controller available that will take the current. A 2.5kw proven machine can generate up to 3.9kw - this will mean a whacking 150amps at 24v. Is there an dc-dc converter or mppt controller that can cope with this?

I am loathe to fork out for replacement batteries and another inverter, but I am not sure if I have any alternative here. Please let me know if you think this can be done in a reliable way.

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off grid 4 years: 2.5kw pv,sunny island 5048, 2 mx 60s, proven 2.5 48v, home made charge controller, 1500Ah fork lift batteries, 60 evacuated tube solar heating, vigas 40 kw biomas boiler, 3000l thermal store
Justme
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« Reply #5 on: June 22, 2010, 07:22:51 PM »

If you use a 48v as a 24v one the peak power in watts will drop to about a quarter of the rated power. The start up speed will be reduced.

There used to be info in a FAQ on the mains Navitron site about doing this.

Found it

Quote
Incidentally, it is possible to boost the performance of the wind turbine in very low wind conditions by using it will a smaller battery bank than intended. For example, if you use a 500W 36v turbine to charge 24v batteries, then the power curve will be shifted towards lower wind speeds, but with a penalty of having a lower maximum output. One customer reported that his Navitron 500W turbine massively exceeded the output of a Proven 2kW turbine in almost all conditions, when used with a 24v battery.
« Last Edit: June 22, 2010, 07:26:46 PM by Justme » Logged

Navitron solar thermal system
30 x 58mm panel 259L TS
1200watts solar 120vdc
FX80 Solar controller
Victron 12v 3000w 120a
6kva genny
6 x 2v cells 1550amp/h 5C
24 x 2v cells 700amp/h 5C
Total bank 4350 amp/h 5C
jhinshel
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« Reply #6 on: June 22, 2010, 10:32:36 PM »

There is not much info on the FAQ. What will happen in high winds if the wind generator is held down to 24v? It seems to me that the current will go high.
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off grid 4 years: 2.5kw pv,sunny island 5048, 2 mx 60s, proven 2.5 48v, home made charge controller, 1500Ah fork lift batteries, 60 evacuated tube solar heating, vigas 40 kw biomas boiler, 3000l thermal store
billi
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« Reply #7 on: June 22, 2010, 10:46:03 PM »

perhaps they can help

http://www.schams-solar.de/windmppt-ENG.html

Quote
There is not a controller available that will take the current. A 2.5kw proven machine can generate up to 3.9kw - this will mean a whacking 150amps at 24v

ok this one does "only"  2800 Watt


Once a year , or twice  perhaps you have the Turbine at more  ....   the average watt will be below 500 Watt i guess per hour (guess!)

Billi


« Last Edit: June 22, 2010, 10:58:24 PM by billi » Logged

1.6 kw and 2.4 kw   PV array  , Outback MX 60 and FM80 charge controller  ,24 volt 1600 AH Battery ,6 Kw Victron inverter charger, 1.1 kw high head hydro turbine as a back up generator , 5 kw woodburner, 36 solar tubes with 360 l water tank, 1.6 kw  windturbine
jhinshel
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« Reply #8 on: June 23, 2010, 06:52:22 AM »

Thanks for that link to the schams site. These controllers look interesting, but unfortunately will not cover the operational range. It does give me hope that there may be a mppt charge controller that can cope with the high current. Midnite solar have been promising a classic controller for some time which sounds interesting. If anyone knows of a system/product which can routinely take 100a at 24v I would be grateful to hear about it. I could knock the top of the operational range with some electronics.
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off grid 4 years: 2.5kw pv,sunny island 5048, 2 mx 60s, proven 2.5 48v, home made charge controller, 1500Ah fork lift batteries, 60 evacuated tube solar heating, vigas 40 kw biomas boiler, 3000l thermal store
billi
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« Reply #9 on: June 23, 2010, 09:53:09 AM »

Quote
These controllers look interesting, but unfortunately will not cover the operational range

I think the dump element in the controller  is kicking in at 160 VDC  and reduces the turbines output and passes excess to a heatelement 

I am sure the build you a bigger MPPT unit if you ask


Billi
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1.6 kw and 2.4 kw   PV array  , Outback MX 60 and FM80 charge controller  ,24 volt 1600 AH Battery ,6 Kw Victron inverter charger, 1.1 kw high head hydro turbine as a back up generator , 5 kw woodburner, 36 solar tubes with 360 l water tank, 1.6 kw  windturbine
jhinshel
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« Reply #10 on: July 16, 2010, 09:38:13 PM »

There seems to be no available mppt controller available that will handle the potential currents of this machine. To keep the system at 24 volt the regulator/controller needs to handle 120amps (3kw). It is possible that the  power goes up to 3.9kw so this really does mean 48v. So I am thinking of the following setup:
sunny island 5048 around 3k - please let me know the best possible price for this  unit
home made diversion load controller using heavy duty rectifier, outback mx60 (70 amps max), voltage monitoring relays: http://www.nortonicsfoxtam.co.uk/pdf/76%20YW-8W-11WRTU.pdf/

Please update with useful comments.
J
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off grid 4 years: 2.5kw pv,sunny island 5048, 2 mx 60s, proven 2.5 48v, home made charge controller, 1500Ah fork lift batteries, 60 evacuated tube solar heating, vigas 40 kw biomas boiler, 3000l thermal store
stephendv
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« Reply #11 on: July 17, 2010, 08:20:12 AM »

Yeah I've seen the Sunny Island advertised for at a german online site for 3110 Euro.  If you're not doing AC side coupling then any other 48V inverter will also do the trick, the Victron Multiplus 5k goes for about 2400 GBP.  Check with Outback, but I don't think you can use the MX60 with a wind turbine because of it's MPPT algorithm.  It doesn't sweep continuously - which is mostly fine for solar panels, but will be a problem with a turbine that changes voltage every second.  You could just use a PWM charge controller for the turbine like a Xantrex C60 with dump load.
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http://www.casanogaldelasbrujas.com
2.8kW PV, SMA Sunny Island 5048, 5 PzS 700 battery bank, stinky diesel.
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