Xantrex C35

55 Posts
Mar 3, 2011 09:19 pm
Xantrex C35

I have a question for anyone that has a C series controller? Does anyone use this controller in diversion mode with both solar AND wind inputs? So long as you dont exceed the amp rating. Will that work? I am currently using just a 60W 12V panel.
220 Posts
Mar 5, 2011 01:40 pm
Re: Xantrex C35

Hi Max,

No problem with multiple charging sources with the C series controllers running in diversion mode charge control.

In this mode all charging sources feed directly into the battery bank (each source through a rectifier or blocking diode)and our controller controls the battery bank (at our set points) by "dumping" an incremental amount of current into an appropriately sized resistive load.

for a resistive dump load we want something in the order of 0.5ohms with a ~500 watt power rating...sounds BIG?..not really, when our controller senses any overcharge it pulses just enough to the dump to keep us at the battery voltage set points..10 watts too much it sends 10 watts to the resistor and so on.

not sure what the max output of your wind turbine is? but you are right..as long as we keep the TOTAL input on the battery side below the max controller output (about 28 amps in this case with the 0.5ohm dump) we are good to go!

some maths:

C35 x .8 (safety factor)= 28 amps

14.4v (approximate dump voltage)/0.5ohms = 28.8amps

28.8amps x 14.4v = 414 watts (minimum power rating of resistor) and (maximum combined dump capabilities)

kind regards, dave
55 Posts
Mar 6, 2011 11:26 am
Re: Xantrex C35

Much like with batteries you cant mix div loads either correct. I have a 125w and a 300w.
220 Posts
Mar 7, 2011 02:09 pm
Re: Xantrex C35

Much like with batteries you cant mix div loads either correct. I have a 125w and a 300w.

sometimes we can mix and match our resistive loads to get to our needed size.

the final wattage of the diversion load will be based on the operating voltage and the total resistance value in ohms...(this calculated value must always be below the power rating of the resistor being used)

that 300 watt load (resistor?) might make for fine dump load all by itself, depending on the size of your whirlybird.. does it have an ohms value printed on it? or it might be expressed as 300watts at such and such voltage? if we see 0.75 ohms printed on it that would be nice...about 20 amps at our dump voltage.

good clean fun, dave
55 Posts
Mar 7, 2011 07:19 pm
Re: Xantrex C35

It is printed with a .75 on it. One last question does the resistive air heater loads you use make a squeeling noise when voltage is applied or is it just me. I am on a learning curve up here in Il. Trial and error and error.
220 Posts
Mar 8, 2011 05:09 pm
Re: Xantrex C35

hehe..yes they do make strange noises, seems to change pitch with how much load is on them. figured it was the PWM frequency of the pulses but no so sure? i notice my hot water heater (grid) makes similar sounds as well.

hehe again..with the learning curve, sometimes it seems like two steps forward then one step back..other days it's one step forward then TWO steps back.

it's all good fun!

cheers, dave
27 Posts
Apr 25, 2011 12:09 pm
Re: Xantrex C35


Just watch your battery voltages carefully with that charge controller.  My Xantrex C40 would go for weeks left alone at my off grid cabin and I would come back to go camping and see that my batteries were never getting charged adequately with my solar only setup.  Everytime I would use them, the c40 would just match the voltage and effectively make my solar panel input less and less voltage until coming to the cabin this spring and seeing everything dead as a door nail - and that was with me running the generator and charger for an entire day each time I'd visit.  Fast forward one month later with an Outback FM-80 and I can go a weekend of camping with my battieres not dropping below 12v, no generator and even heavier usage.  The batteries were ultimately toast thanks to the c40, but the FM-80 has brought them back from the brink.....so just watch that c35 closely...
55 Posts
Apr 30, 2011 09:41 pm
Re: Xantrex C35

I will keep a wary eye on it then. Money's getting tight to have a failure of 2 parts of my solar equipment.

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