step down converter

[Westbranch]

If you put all 6 in series you will be WAY over the sweet spot as Dave put it. 
Why? because you have the formula wrong, in series configuration you add the voltage ONLY , in Parallel configuration you add the Amps.
So in your case you will have a nominal Voltage of 6 x 12v = 72V nominal, Voc much higher.
A ratio of 6:1

[vtmaps]

would it be better to just go with 2 more 85's and run all 6 panels in series
4.93 x 6 = 29.58 amps

Putting 6 of those 85 watt panels in series will mean multiplying the VOLTAGE by 6.  The current will be 4.93 amps.

Why don't you do what I suggested back in reply #6 in this thread:

You can keep your old panels and controllers as they are, and add a kid and new panel.  No problem having multiple controllers all charging the same battery.

--vtMaps

[vtmaps]

would it be better to just go with 2 more 85's and run all 6 panels in series
4.93 x 6 = 29.58 amps

If you want to run six of those 85 watt panels, you could put them all in PARALLEL with your current controller (if it can handle the 29.58 amps... you haven't told us what controller you have).  Your combiner would need six circuit breakers.

You could also hook up the six 85 watt panels in three parallel strings (with two panels in series per string).  In this case you would be combining three strings and your current circuit breakers would be OK.  You would need an MPPT controller such as the kid.

--vtMaps

[tecnodave]

Vt,

I did not recommend that course due to the fact that his existing controller is a Chinese PWM  controller. When the kid pulls up the voltage to a true charge for t-105's it will cause the Chinese controller to shut down as it will see a "full battery" . I have this situation with my Chinese Tracer MPPT controllers on same battery with a kid or Classic. I can use my Tracers to assist with bulking, but at adsorb they shut down, leaving all the work to the controllers that can be tailored to the battery type.

This is exactly what I am referring to when I say  "1 size fits all"  , most Chinese controllers assume a group 27 auto start/deep cycle , there is no provision for a true deep cycle such as T-105's , GC-2's , and L-16's.

My opinion on batteries that have a listed CCA (cold cranking amps) : this is not a "true deep cycle" it is an auto start battery! Not suitable for solar work! It will not stand the repeated cycling found in RE systems and will fail in 90 days or so.

To mimic TomW,  that is my story and I'm sticking with it.

td

[tecnodave]

Optical mike,

I may have misidentified wires in your converter box,  going back to the pic's you posted there are two stranded wires in that converter box. On #5 breaker there is a stranded wire going to the bottom portion of the converter, this one is probably the AC to DC converter power, I'm not sure just what the other stranded wire is. Trace it back and see if it exits the back of the box or stays inside. This is on the water heater breaker and might  power the transfer relay. There are two open breaker spots and you could easily add one SquareD Homeline HOM1515CP breaker to separate the circuits. The relay when energized makes a clack sound as the relay switches.

td

[opticalmike]

Mike,
Your original first post in this thread is the way to go. Hanwa panel would be good and rewiring the 85w PVs for 24v. Then the two 24 volt strings of 85s and the hanwa, at 24 volts, can wire into you midnite combiner using  3 breakers.
The answer to your question is that the KID will be perfect for this setup and will do all the voltage down conversion to charge your 12 volt battery bank.

Dgd

would I still be able to use my 12 volt inverter?
mike

[Vic]

Mike,

Think that the rub in dgd's suggestion,   is that when you mentioned that the Hanwah PV was 24 V,  it is NOT really a 24 V PV.   td did mention this fact previously.   Almost all PVs in the 230 - 275 W range are 60 cell.   Many folks call these PVs 24 Volters,  but the Vmp of this PV is just under 30 V.  A REAL 24 V PV has a Vmp of about 35.5-ish Vmp.  Some will be a bit above 36 Vmp.

As such,  strings of two of the real 12 V 85s will not get along well with 30-ish V Vmp PVs,  like the Hanwah.    FWIW.  Vic

[dgd]

Ahh, the danger of making assumptions 
Having goooggledd the hanwha PVs they all appear to be the 60 cell type so my original suggestion about using one is completely wrong.
Thanks for pointing out this info Vic..

Mike, your suggestion about getting another two 85W pvs looks good.
I would suggest wiring each two in series (ie connect positive from one panel to negative on other then remaining +ve and -ve go to junction box).
So you have three sets of wires going to junction box.

This would mean about 35volts at 14.5A going to KID, ideal for mppt to charge a 12v battery.

Your 12v inverter connects to battery and is not effected by how you configure the PVs into the KID.

dgd

[opticalmike]

I did manage to get two more 85 watt panels, so if I rewire them into 3 strings of 2 panels what about the 10 amp breakers I have?....do I need to buy the 15 amp breakers?
KID and temp probe and Wbjr and shunt...on their way
These are the panel specs:
Vmp 17.3v
Imp  4.93a
Voc  21.6v
Isc   5.28a
Location Northern Alberta
winters ~ -40C
what would the final voltage be on a cold winter day...we see lots of these!
thanx,
mike

[Westbranch]

If you use the sizing tool for which ever CC you are going to get it will tell you how high V cold will get for your desired temp...

KID   http://www.midnitesolar.com/sizingTool_kid/index.php

Classic  http://www.midnitesolar.com/sizingTool/index.php

[chris]

  I believe the kid is rated for 150 volts......so I don't think you have anything to worry about there.....I'm not in northern alberta.....but here in the Kootenays BC I didn't have any problems.

  Besides....running them in stings of 2 will only bring you up to 34.6 volts

[opticalmike]

whats better? I dont use in winter at all. 6 in series, 2 strings of 3, or 6 in parallel? is it better to have more amps or more volts?

[Westbranch]

Assumption:  I believe you are wanting a 12 V b. bank...(?)

So, how efficient or, contrarily, how inefficient do you want the system to be?

The larger the difference of the V going into the CC and the V coming out of the CC determines both!

The recommended difference is to go from one step ie 24 V to the next lower step, ie 12V,
or 48V to 24V... or 96V to 48V.

So in your case you are going from 6 x 17.3 =103.8V too much differential to 12 V
3 x 17.3 =51.9  ... better
2 x 17.3 = 34.6 .... better still
1 x 17.3= 17.3 ...  best for 12 v system

Then you have to consider the distance between the array and the b. bank and the line losses.
I believe you are talking about a camper/trailer so losses may be small, now the kicker:  the higher the V, the less loss per foot or meter that Voltage has to travel between the panel and the battery... so you trade one efficiency for another loss.

here is a voltage drop calculator you can use

http://www.solar-guppy.com/download/voltage_drop_calculator.zip

[opticalmike]

My panels are less than 20 ft to the cc and battery bank
Loss on wire is less than 2 % so highest amperage ?
I need 2 more 10 amp breakers 

[Westbranch]

Highest amperage  would be 6 x 4.93A = 29.58A from combiner to CC, and depending on what the CC sends to the battery, there could be  a (modest) boost in amps depending on battery SoC.

hth