Limiting bulk charge current

[vtmaps]

One advantage of "over-sizing" a solar array is the ability to charge your batteries in overcast conditions.  But when bulk charging, full sunlight can produce too much current for the batteries.  Fortunately, the classic can be configured to limit its output.

The problem with setting an output limit is: the classic cannot put out the full array power to handle opportunity loads. 

My question is: with a WBjr, can the classic reap all the array power for opportunity loads, but still limit its output during BULK (by monitoring battery current) when the load is disconnected?

--vtMaps

[dgd]

One advantage of "over-sizing" a solar array is the ability to charge your batteries in overcast conditions.  But when bulk charging, full sunlight can produce too much current for the batteries.  Fortunately, the classic can be configured to limit its output.

The Classic will limit current to it's rated max current output anyway, no matter how over-sized the pv array is. The only reason I can think of to set the current limit is because the battery bank is pretty small. Since AFAIK most are happy with C/10 to C/5 charge rate then unless the Classic with oversized array is getting to C/2 or greater than C and likely to cause battery problems, then set the output current limit.  The proper solution would be a larger Ah capacity battery.

The problem with setting an output limit is: the classic cannot put out the full array power to handle opportunity loads. 

It can't put out the full array power if the array can generate more than the Classic's max rating, opportunity loads or not.

My question is: with a WBjr, can the classic reap all the array power for opportunity loads, but still limit its output during BULK (by monitoring battery current) when the load is disconnected?

Interesting. Would this not mean the Classic would need to somehow understand separately the current needed by the opportunity load(s) and the battery during bulk? And be able to auto control the output current limit at any time?

Anyway,  maybe this is possible..

Dgd

[tecnodave]

My understanding and from the wiring is that the Whizbang shunt being right at the battery it will see the battery charge and discharge current whereas the internal shunt in the classic is seeing the total current provided by the Classic so then if that is true the Whizbang will control the maximum battery charge current and the shunt in the Classic will see the battery current and the opportunity load as well, I.e. Total output current of the Classic . If that is indeed the case then whatever opportunity loads will be limited only by the classic current and temperature. I would assume that you will be able to use opportunity loads at will up to the limit of the Classic itself, of course assuming that those loads will be coming through the Classic and not tapped off before the Classic.

It would seem to me the only way that the Classic could protect itself is to still read it's internal shunt even if you would be using the Whizbang shunt to set charge amps.

Tecno

[zoneblue]

This is a topic of interest to me as our ssrs arrived today. A previous poster went to great length to try to explain that pwm AUX2 doesnt understand current limiting in bulk. He said that it only considers surplus in absorb or float. Anyway now that WBjr occupies Aux2,  the classics PWM route is now taken out of the equation, so im looking for another solution. I also received the small reference solar panel, and an arduino, so i guess ill be looking at building something over the summer.

Take the reference panel "possible watts", subtract the classic "output watts", that should give how much you can dump to hot water. Theres a whole bunch of logistical problems, the very first of which is getting consistant readings from the classic. I think i have solved that by using newmodbus in a different way, to run in continuous mode, caching data every 10 seconds.  Ironically it works better at faster sample rates than mid range rates. The trick is to not close the modbus connection.

Then reference panel shunt goes into ADC on uC. Beyond that im very much still on the drawing board.

[tecnodave]

vtmaps

After rereading the thread I get what you are getting at, like you I have set my classic output current down from the 96 amps value as I think that is too high a charge rate for my batteries, I do use extra power to run another heating device but only when my batteries are near full charge. This is not controlled by the Classic but through an auxiliary circuit board which looks at the input voltage to the Classic and when it rises 10% over volts at Pmax for more than 10 minutes ,plus sun temp through a cheap photocell and battery volts, then clicks in a relay which turns on a cheap 24 to 12 volt converter (Pyle) to power the electric heating element in my adsorption refrigeration. It also provides the "ignition signal" to the refrigeration which causes it to switch from propane to electric. Not quite that simple as the thermostat output of the frig is in there too so the DC-DC converter does not run unless the thermostat is calling for heat(cooling).
I have not got the Whizbang as yet but ordered it so that I could protect my batteries while at the same time run the refrigeration from the solar when charging only and from propane during the night to conserve battery usage. This system was built when I was using Chinese EP Solar Tracer controllers before I got the classic. I am using iPad and Mac PowerBook so as of now have not been able to tap into the classic's internal data. I am looking into a way to do that without buying a windows laptop.