Losses when controlling 48 volt PV system for 12 volt battery bank

[asdex]

Hi, can someone tell me what sort of controller loss would you expect when connecting PV panels for 48 volts to a Midnite 150 but charging a 12 volt battery bank. The panels are 6 x JA Solar JAM6 320w. 8.67 Imp/A, 36.91 Vmp/V.
I would connect them into 2 strings of 3 panels. Also is there any advantage of a 48 volt array compared to 24 volts if the panels are close to the controller and batteries?
I may change to a 24 volt battery bank but as all my cabling is short runs don't think it's needed. I would have to replace my 12 volt inverter, LED lights, radio, water pump.
Thanks,

[boB]

24V array and 12V battery would be the lowest losses.   48V array and 12V battery is fine too,  but 24V array
wiring is pretty low losses, especially if the wire run is fairly short.

Very good ratio of 2 to 1 there.

boB

[vtmaps]

Hi, can someone tell me what sort of controller loss would you expect when connecting PV panels for 48 volts to a Midnite 150 but charging a 12 volt battery bank. The panels are 6 x JA Solar JAM6 320w. 8.67 Imp/A, 36.91 Vmp/V.
I would connect them into 2 strings of 3 panels. Also is there any advantage of a 48 volt array compared to 24 volts if the panels are close to the controller and batteries?
I may change to a 24 volt battery bank but as all my cabling is short runs don't think it's needed. I would have to replace my 12 volt inverter, LED lights, radio, water pump.

That's quite a bit of panel for a Classic on a 12 volt system.  If you ever produced anywhere near your panel ratings you could be putting more than 150 amps into your batteries... except that's way more than the Classic can handle. 

The same array and the same classic would be very happy charging a 24 volt battery bank.

Regarding your other question, yes it is better to wire the panels as 24 volts if you are using a classic on a 12 volt battery.

--vtMaps

[asdex]

Hi, thanks for your replies. Sounds like I shouldn't have much of a problem as long as the PV array is not to high a current.
My preference is 48 v (2 strings of 3 panels) feeding into a 12 volt battery bank. The panels are about 15 meters from the controller but I will be using 16mm2 cable.
I am also looking at using a PWM controller as well as the Midnite in diversion mode to dump excess current to a load.
That will be connected to the battery bank. I expect the voltage this would run at would be battery bank level or maybe around 14v. Would that be correct?
Thanks,

[Tons001]

You should be able to setup your dump load using your Classic 150 and a relay without a PVM controller.

[dgd]

Hi, thanks for your replies. Sounds like I shouldn't have much of a problem as long as the PV array is not to high a current.
My preference is 48 v (2 strings of 3 panels) feeding into a 12 volt battery bank. The panels are about 15 meters from the controller but I will be using 16mm2 cable.

Panel voltage in this configuration is very high. A string of three will make over 110v (3*36.9v) and having the Classic reduce this for a 12v battery will not be the most efficient use of the panels.
Better in 3 strings of two panels for about 73v especially if you plan to go to 24v battery system.
If staying with 12v battery then I would consider no strings and just have all the panels parallel connected together to give 36v into 12v.
Also too many panels for a 12v system, 4 of these 300watt+ in parallel fora 12v battery system
I would strongly recommend going to 24v even though it means getting a 24v inverter.

dgd

[asdex]

Ok thanks, as you say 24 volt sounds the best voltage for the  battery bank. I expect I could use a 24/12 volt converter for the smaller items. I'll look into the circuit for using the Midnite 150 to feed the dump load. I'll be using a 24 volt hot water element for this.
I'm not exactly sure how much current would be supplied to the element once the batteries are charged. from the Midenite string calculator would it be the rated pv array current of 26 amps or would it be the battery charging current of 66.7 amps@28.8 volts?
Cheers,