Outback FX voltage fun [RE-wrenches]

[Christopher Freitas --- OutBack Power]

Hugh - 

Glad to hear that you are using an OutBack inverter. Sorry for the slow 
response - I was testing inverters (and myself) in the Black Rock Desert 
of Nevada all last week.   

I think the issue you saw with the generator is due to the rather high 
impedance of your battery combined with the type of voltage regulator on 
the generator.  Effectively - The OutBack charger is sending the power 
from the generator to the battery - but since the battery is so "stiff" 
some of the energy gets reflected back at the generator.  Often the 
response time of the generator's voltage regulator is fairly slow - so 
the AC output voltage of the generator jumps up since there is nowhere 
for the power to flow.  You are effectively getting a standing wave 
effect where the two waveforms are added together.  I have seen this 
when we have tried to push very high currents into small batteries with 
some specific models of generators.  

The two solutions I have used with issues like this on OutBack and other 
inverters is to add some HV motor run capacitors (20 to 50 mF) across 
the AC output of the generator itself or to ensure that there is a 
resistive load on the generator when the charger is running.  The 
capacitors rarely cause any probelms when wired across the generator's 
output and can also help the generator run electronic loads much more 
smoothly - such as compact fluorescent lights and TVs.   The caps will 
also dampen this "reflected" power issue to prevent the high voltage 
spikes you saw. The resistive load provides a load on the regulator / 
generator and also consumes this reflected power as well.   

I would start with 20mF and then watch the waveform unloaded on a scope 
- if it looks OK then increase the amount. 

Let me know if this addresses your issue.  

Christopher


Christopher Freitas
OutBack Power Systems, Inc.
cfreitas @ outbackpower.com  
www.outbackpower.com
Arlington WA USA
Tel 360 435 6030  


Hugh wrote:
> 
> Hi Wrenches,
> 
> I have recently got a VFX 3048 50Hz and installed it in my own home. 
> Very solid and quiet.


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