Charge, Dump, Inverter / Charger Questions

[Dave B]

Hello,

  I plan to set up my 16' to charge batteries as a 48 V system. The more I read the manuals and search the more confused I get. Could someone please help me with these questions ? As a hot water system direct AC typically my machine will peak @ 3 KW fully furling in 25+ MPH winds. If need be I will wind a new stator and would like to keep the machine rating conservative at a 3 KW 48 V system.

1. A C-40 is rated at 40A for 48V. Am I correct in assuming that this charge controller functioning in the diversion load mode can only safely divert 1920 watts ? If so, can mulitple C-40's be parralleled to double / triple etc. the diversion (dump load) capacity ?
   
2. An inverter / charger monitors the battery bank as well. Using Trace / Xantrex again as an example : If the batteries need to charge and there is not enough wind, will the inverter / charger then start charging the batteries from the grid ? Am I correct in that these voltage levels can be operator set so that basically you have "seamless" AC available from your batteries / inverter no matter if charged from your alternator (if wind is available) or then the grid if set to default this way ?
   
3. Assuming the inverter / charger is charging the batteries from the grid, does this then take priority as automatically charging bulk, absorbtion and float ? Or, would the C-40 monitor and control this charge ?
   
4. It's obvious I am confused at how each component functions as the complete charging system. Again, what I wish to do is charge a 48 V deep cycle bank and run the inverted AC to several isolated circuits of my home. I want to safely divert to a dump load when the batteries are fully charged. I wish that the batteries will automatically be charged / maintained from the grid for the down times of little or no wind while still being able to run an AC load from the inverter. Am I dreaming or is this how a system might work ?
   
   

  Thank you to anyone out there who may be able to clear this up for me. I am not lazy and have read several manuals. It just seems that there is very little complete "system" information with regards to function out there.  Dave B.  

[kurt]

 they make 60 amp rated diversion controllers for 48v like the Morningstar Tristar series.

you can set the diversion controller dump voltage higher than the charge voltage of the inverter charger to keep them from interfering with each other  

[electronbaby]

1. Yes
   
2. Yes
   
3. Yes (ill explain further)
   
4. Yes, this will work fine granted you program the inverter AND the charge controller accordingly.
   
   

With regard to question 3:  The priority you want it to take as far as charging, is solely dependent on the voltage level you set it at. If you want the inverter/charger to take priority over charging the batteries, you would program the charge voltage threshold slightly higher than the other controllers on the other charging sources. This would make sure that as the batteries become discharged, they would be recharged first by the grid. You would then program the other charging sources with their own controllers as you go up the food chain depending on their charging priority.

If you wanted the wind to take precedence, you would program this at the higher float voltage to make sure the wind would charge the batteries first. If there was no wind, you might want to program the PV next (this can run open circuit without damage, so no dump load is required for the PV, but it is for the wind). If there is no PV, then you would program the grid threshold next. This means that if you have no wind, and no sun, the grid would top you off (kind of like a last resort before your batteries are seriously drained). I think in the Xantrex inverters, this is called BX mode, but i may be wrong, its been a while since I played with one of those.

Personally I would not use Xantrex controllers for dump load controllers because of their latency.

It is however very important that if you are going to use multiple charging sources, that you realize the effect of charging your battery with the grid and making sure your charging voltage at the top of your bulk cycle does not hit your dump load threshold setting. This happens sometime in the winter when the voltage on the battery bank is allowed to rise because of the cold temperature. If you are not paying attention, it might cross over your dump load threshold and cause your dump load to come on and dump energy from the grid or PV. Quite often the grid charging current is not lowered to an acceptable level dictated by the rating of your dump load controller and this will cause failure of your dump load/load controller/and possibly cause a fire.

Quite often if you are running a wind turbine and a dump load controller, you would connect the turbine directly to the battery bank and program the float voltage higher on the diversion load controller. What this does is allow ALL other charging sources to operate but saves you in the event that the turbine pushes the voltage up higher. This method only allows the diversion load controller to dump the amount of energy produced by the wind turbine and not the other sources. Use a temp sensor on the diversion load controller.

I hope I didnt confuse you.

[SparWeb]

About the Xantrex charge controllers: I remember reading that they should be used only at 80% of their rating when used as a diversion load controller.  Look through the manual to find the details.