step down converter

[Westbranch]

Or alternately just do nothing but talk incessantly and enthusiastically about the new KID on the block and memorize all the features and that it is half the price of the Classic...  finally she will beg you to JUST GET IT so she can talk about something other than a charge controller from dawn till dusk...

[dgd]

Or alternately just do nothing but talk incessantly and enthusiastically about the new KID on the block and memorize all the features and that it is half the price of the Classic...  finally she will beg you to JUST GET IT so she can talk about something other than a charge controller from dawn till dusk...

I thought that only worked the other way about when SWMBO wanted something!
Mike, just buy the jewellery 

dgd

[tecnodave]

Mike,

A lot of Solar controllers treat batteries as 1 size fits all, the charge rate for a group 27 auto battery is the same as a real deepcycle such as a GC-2, T-105 , or L-16  I had to run my generator twice as much as necessary to top the batteries because my sunsavers and tracers would not charge big batteries properly. 14.3 is not high enough voltage for large batteries. The kid and Classic pay for them selves by being able to set voltage , time , and current to the values needed to properly charge true deep cycle batts. The kid can be programmed to charge a 21 volt battery if you can come up with one or the new LiFePo4 lithium Ion 13.3 volt. No limits!  Maybe about 60 volts max charge voltage.
I have used mine to charge a 18 volt Nickle Metal Halide Makita power tool battery.

Sometimes I need 15.6 to equalize my L-16 set and my Classic has already paid for itself in less generator run time, less time in maintaince, and more time gone fishin!

It's really nice to go out somewhere with no utilities and enjoy nature without hearing the gen drink dinosaurs. Now at worst after 6 days of fog I need only 2 hours generator run to bulk the batteries and 3 hours of solar to top everything instead of running gen for 5 hours to keep batteries topped up.
Well worth it, but I am totally off grid. I would be 100% solar except my panels don't work worth a dam through pea soup fog.......none of them do......I just need to fire up my Johnny Porta-Nuke....


Battery state of charge is best determined with a hydrometer. The glass float kind is best full charge an your batteries is 1.275 specific gravity (s.g.)  I recommend that you get one, measure the cells in all your batteries with hydrometer and keep a notebook of the readings.
All the cells should be within .020-.025 of each other with a reading at full charge of 1.275 after letting the battery sit a while after charging. A voltmeter will give you an idea but the hydrometer is the real test for s.o.c.  (state of charge). Auto parts store. About $10-12 . I do not like the plastic float with a pointer and the 4 colored balls is a joke. Real glass float is the way to get accurate readings.

Grounding, the NEC wants you to bond everything togather but with an RV negative is grounded to the chassis so I would suggest 10 Guage green stranded wire bonding wire to all components , charge controller , inverter , and combiner box  grounded to the bare wire buss bar on the left side of your converter box . Connect all negatives to frame ground EXCEPT p.v. panel negative goes directly to p.v. Negative input on the kid charge controller. This is because the kid measures it's current in the negative lead. Some other controllers can have the negatives tied togather but not on the kid cc.

The National Electrical a Code (NEC) is pretty specific that there shall be only bond between (AC) neutral and ground and that should be in the main panel. It is standard practice to ground this ground buss bar to the motorhome frame where the DC ground is located.  The ground rod provided in campgrounds is an added safety bonus, it insures that your coach will be grounded if there is a fault of lightning strike. Not a bad idea to have a braided copper bond wire with a large clamp to attach to an external ground.

I have pounded two ground rods at my stationary motorhome for added protections but then I am a commercial electrician so I need to practice what I do and preach to others.

td

[tecnodave]

Dgd & Wb,

I tried a slightly different, when the GF complained about $610 for the Classic I offered her a deal, I would continue using using one size fits all charge controller if she would give up designer clothes and let me buy her one size fits all. Gotta bunch a flak but I have a Classic and a kid with one more soon.

td

[chris]

Or alternately just do nothing but talk incessantly and enthusiastically about the new KID on the block and memorize all the features and that it is half the price of the Classic...  finally she will beg you to JUST GET IT so she can talk about something other than a charge controller from dawn till dusk...

  LOL, this approach worked well for me 

[opticalmike]

So for clarification, I want to add another panel(a compatible version is the grape 160 watt) this brings my camper to 500 watts & 4- T105s
....4 panels 85watts each and the grape 160 watt.  I want to re-wire them in series to get the voltage as high as possible.The kid will readjust the voltage from whatever the array above ends up at to 12 volts as long as the current isn't over 30 amps.?
This sounds workable??
mike

[vtmaps]

....4 panels 85watts each and the grape 160 watt.  I want to re-wire them in series to get the voltage as high as possible.

This is NOT workable, unless the Imp of the grape is the same as the 85 watt panels.   --vtMaps

[opticalmike]

within 5% or less

[vtmaps]

within 5% or less

That will work OK  --vtMaps

[dgd]

within 5% or less

Thats impossible, you are saying that a 160watt 12 volt nominal PV with a mpv of 18.5v has a Imp within 5% of an 85watt panel that is also a nominal 12v PV with an mpv between 17 and 18volts ?
Vtmaps was correct first time, these PVs cannot all just be wired up in series,

You seem to be having some basic difficulty with understanding how PVs can be configured in series/parallel and when voltages OR currents have to be the same.

I cannot find any info on the 85 watt panels, you have not posted details so assuming a standard PV type these are likely 36cell types with Vmp 17.4volts and Imp 4.8Amps (or figures close to these)

When you connect the 4 85watters and the 160watt pv all in series the voltages will simply add together 17.4 + 17.4 +17.4 + 17.4 +18.5
The problem arises with the current that can flow through these series connected PV and it will be restricted to that maximum current that can flow through an 85watt PV - ie about 4.8A
This means your nice new 160 watt PV will only make 4.8A and NOT 8.65A.
the 160 watt panel will behave just like a 90 watt panel.

The solution (are you already planning this?) is the four 85 watt pvs in two groups of two in parallel then each group in series with the 160 watt panel.
Total array voltage mpv about 52volts and Imp 8.65Amps.

dgd

[vtmaps]

The solution (are you already planning this?) is the four 85 watt pvs in two groups of two in parallel then each group in series with the 160 watt panel.
Total array voltage mpv about 52volts and Imp 8.65Amps.

dgd, I suspect your analysis is correct.   What do you think the series fuse rating is of the 85 watt panels?  You see where this is going... 

--vtMaps

[opticalmike]

Sorry about not listing the panel specs LDK 085P
Vmp 17.3v
Imp  4.93 a
Fuse rating 10 a
IEC: 1000 Vdc / UL: 600Vdc

What about the difference in fuse rating? the grape 160 has a 15 amp max fuse and the LDK 085P has a max 10 amp
2 x 4.93 amps is still under the fuse rating.
Perhaps it may be better to add 2 more 85's than one grape 160
That way Im all matched up and run them all in series

[dgd]

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

[tecnodave]

Optical mike and the group,

I've posted this before so forgive me for being redundant but this is very basic to solar:

Panels in series must have the same current (Imp) within a few percent to be efficient.
Panels in parallel must have the same voltage (Vmp) within a few percent to be efficient.

Strings should be all panels the same with few exceptions,

Series / parallel strings will have a problem in current sharing,

In Optical's case the 85 watt panels internal bypass diodes will not be able to pass the current of the larger panels and would not divide the current equally leading to the over current in one panel and blowing the bypass diode. Since these are internal some cannot be serviced leading to the loss of the panel.  (They can be accessed in panels with junction boxes)

The worst case is when the 160 is in full sun and one or both pairs of 85's are shaded

It has been recommended by one manufacturer (Siemens) that external bypass diodes be wired across any panels that are wired in such a configuration. In Optical's case this would mean adding a diode wired across each pair of 85 watt panels to protect the internal bypass diodes. The reverse flow diodes will not be affected.

These diodes should have a rating of 2 times the panel current and 2 times the total string voltage.
It is not necessary to use Schottky diodes here as we are not concerned with forward voltage drop but Schottky's can be used here.

I try to limit my suggestions to the skill level of the person doing the work, not to my skill level.


Point missed by everyone:   This is a 12 volt system.......5 "12 volt " nominal panels in series is about 90 volts @ max power........this puts the kid at a voltage conversion ratio of 7.5 to 1........not in it's "sweet spot"..... Efficiency will be much better at 2 to 3:1 down conversion ratio.


My suggestion.   Three strings of two panels each.....two with two 85's in series....and one with two 160's in series.....way more reliable....way more understandable for the newcomer...use a combiner box with approiate breakers for each panel rating........Isc (short circuit current)  times 1.25 (NEC safety factor)

This configuration will make shading issues less of a problem, and put the kid at 3:1 conversion ratio, the kid will be more efficient and radiate less heat.

td

[opticalmike]

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