Charge Controller Opinions - Small RV Install

System

Greetings All --

I am speccing out a system for a small 17' RV that will be my full time technomadic home. Details of the project are posted here:

http://radven.livejournal.com/tag/oliver

I will probably manage 100W to 300W of solar on the roof, and I'd like to make as efficient use of that power as possible. I am looking for opinions and experiences with the following contender MPPT charge controllers:

+ Heliotrope HPV-22B -- 22A, up to 400W of solar. 24V to 12V conversion. Includes temperature cable.

+ BlueSky 2512i -- 25A, up to 250W of solar. No support for 24V array. No support for battery temperature.

+ BlueSky 2512iX -- Same as the above, but adds equalization, battery temperature compensation (sensor is extra cost), and aux output.
(I currently have a 2512iX on my Tab trailer...)

+ MorningStar Sunsaver MPPT - 15A, can handle around 200W of panels with 12V battery output. Supports 24V array.


Are there any other charge controllers I should consider?

- Chris // www.technomadia.com

Solar Guppy

Re: Charge Controller Opinions - Small RV Install

In the power range your looking at the MorningStar Sunsaver Mppt is the best performing unit, both in Mppt tracking and efficiency.

If you do choose to get one, get the external battery sensor as without it the unit uses the internal tempature to adjust the charging compensation values.

The Sunsaver also has the widest input voltage of the bunch ( 75V ), so you can series string upto 3 12 volt panels, less wire and better performance than parralleling panels.

Windsun

Re: Charge Controller Opinions - Small RV Install

The new Sunsaver MPPT also has much better efficiency and better MPPT tracking than the Heliotrope, and they can be used with almost any high voltage panel up to 180 watts or so.

I just hope they come out with a 30 amp unit soonish.

System2

Re: Charge Controller Opinions - Small RV Install

How does the SunSaver compare with the BlueSky 2512iX?

I am concerned about being limited to just 200W of panels with the SunSaver. Having the option to hook up 300W would be nice...

Thanks for the advice!

- Chris // www.technomadia.com

Windsun

Re: Charge Controller Opinions - Small RV Install

The 15 amp limit is the main downside to the SunSaver MPPT, more than that and you will have to go to another controller.

Solar Guppy

Re: Charge Controller Opinions - Small RV Install

The SunSaver is about 3% better efficiency and MUCH better mppt. The Sunsaver is low cost to just add SunSavers as your system needs grown ... a pair is 30 amps and cost wise not much more than a BlueSky 30 amp unit

BlueSky are well built units, buy very dated technology wise

mike95490

Re: Charge Controller Opinions - Small RV Install

Windsun wrote: »

The 15 amp limit is the main downside to the SunSaver MPPT, more than that and you will have to go to another controller.

Here's an off the wall question, say you DO go over the limit for the controller, does it just limit itself at 200W, (Like GT inverters) or does it fry itself ?

Perhaps 1 possibility is to use a buck/boost controller while on the go, and feed that from the car alternator.

another would be an inside stowable array, with it's own cc and tie it in when parked.
Do you use a shade canopy while parked, or shelter over the kitchen ?

The only advantage with the 24V RV panel, is the high heat performance, in that the panel output does not fall below voltage required to run the controller and reach charge levels. If you have a better vented panel, it won't get so hot, but is more prone to be blown off, if not stowed to travel position before you bug-out. All tradeoffs.

Solar Guppy

Re: Charge Controller Opinions - Small RV Install

The SunSaver Mppt is a true step down converter, its current limited to 15amps on the output side and can down convert from as much as 75V. You can hook up an unlimited amount of solar and it will safely limit to 15 amps into the battery. In Warm climates, one can hook up for example a pair of KC130's and barely push the unit ( at solar noon ) into current limit as we all know panels in the real world put out more like 80% of wattage due to heat and sun angle effects.


The 15 amp current limit, IHMO is not a big deal, if you have more solar wattage than can be handled by a single controller, then add more parrallel chargers ( battery side ). This has the added advantage for having Mppt independant , so for example shading can be better handled, with for boat use is a big plus

With a Street price of 190-210 for the Sunsaver, its not much more than other quaility Mppt Controllers ( for example a pair for $380 ) with the advantage your TAR load is MUCH lower than larger mppt units and hence much more efficient.

For RV/Cabin/Boats the SunSaver is the best option out there, nothing else has the input voltage range and efficiency performance that the SunSaver has ... doesn't hurt you can run SC-View on it either:roll:

System2

Re: Charge Controller Opinions - Small RV Install

mike90045 wrote: »

Perhaps 1 possibility is to use a buck/boost controller while on the go, and feed that from the car alternator.

I am confused as to what you are suggesting here. How are you suggesting wiring in the car alternator?

Thanks,

- Chris // www.technomadia.com

System2

Re: Charge Controller Opinions - Small RV Install

Solar Guppy wrote: »

In Warm climates, one can hook up for example a pair of KC130's and barely push the unit ( at solar noon ) into current limit as we all know panels in the real world put out more like 80% of wattage due to heat and sun angle effects.

Excellent point. I think you've sold me on the SunSaver MPPT for my purposes. If I do manage to overload it with two panels, that will be a good problem to have...

Solar Guppy wrote: »

The 15 amp current limit, IHMO is not a big deal, if you have more solar wattage than can be handled by a single controller, then add more parrallel chargers ( battery side ). This has the added advantage for having Mppt independant , so for example shading can be better handled, with for boat use is a big plus.

How big of an issue is unequal sun angle or shading? If I leave one panel on the roof permanently flat, and another deployable when stopped on a ground mount - there will certainly be different sun angle and shading.

In this situation - is parallel or series wiring heading into the charge controller preferable?

Solar Guppy wrote: »

For RV/Cabin/Boats the SunSaver is the best option out there, nothing else has the input voltage range and efficiency performance that the SunSaver has ... doesn't hurt you can run SC-View on it either:roll:

You've convinced me! Now, is there a way to run SC-View on a Macintosh??

Thanks!

- Chris // www.technomadia.com

mike95490

Re: Charge Controller Opinions - Small RV Install

technomadia wrote: »

I am confused as to what you are suggesting here. How are you suggesting wiring in the car alternator?

Buck boost converter, a gadget to step up voltage (boost) so you could get your 13.8V alternator output, boosted up 5 volts or even up to 24V (DC-DC converter , often sold for Big Rig Truckers 12V - 24v upconverters) Feed that thru your power/lighting connector to the trailer. Could be as simple as an extra pair of wires to get 13.8v to the trailer (please don't use the hitch as a ground return) and mount the up-converter in the trailer, where it could feed 24V to a MPPT controller. Voltage input to the controller needs to be at least a couple volts higher than your battery top-off voltage.

They might have one here ( http://store.solar-electric.com/ ) for use with pumps. (I have not spotted it yet)

System2

Re: Charge Controller Opinions - Small RV Install

Solar Guppy wrote: »

The SunSaver is about 3% better efficiency and MUCH better mppt. The Sunsaver is low cost to just add SunSavers as your system needs grown ... a pair is 30 amps and cost wise not much more than a BlueSky 30 amp unit

BlueSky are well built units, buy very dated technology wise

I've been reading the data sheets just now... The older BlueSky models claim to be 95% efficient, and the newer ones (like the 2512iX) claim 97% efficiency. That seems to match what MorningStar claims in their datasheet.

Is there someplace else I should be looking for comparison data?

One other concern I just discovered reading the MorningStar documentation... The float voltage is fixed at 13.7V, which is significantly above the 13.3V recommended by LifeLine.

Should I be concerned about this?

I did also get the documentation for the Heliotrope HPV-22B, which is annoyingly not online. Its max panel voltage is 30V - lower than I had hoped.

Thanks for the great info,

- Chris // www.technomadia.com

Windsun

Re: Charge Controller Opinions - Small RV Install

The catch is in the details.

The Morningstar has a much better MPPT tracking algorithm, so it's overall average efficiency is better. Better in fact than the Outback Power MX60.

While Blue Sky have a max of 95-97%, you will only see that about 60% of the time, with the Morningstar it is more like 80% of the time.

Solar Guppy

Re: Charge Controller Opinions - Small RV Install

The Bluesky 3024i I did comparative testing on for MS ran about 92%, if you look at the data sheet, they are using 24V as the output, not 12V, they are also using a Vin/Vout of only 4 volts

http://www.blueskyenergyinc.com/pdf/SB3024i_datasheet.pdf

http://www.morningstarcorp.com/products/SunSaverMPPT/info/SSM_Manual.pdf

The MorningStar has full graphs for both 12V and 24V ... in the 12V testing I was seeing SunSaver @95% and the BlueSky@92%

A float of 13.7V won't hurt anything, just make sure to get the remote battery tempature sensor

While neither units are FCC compliant, the BlueSky radiates @45khz and harmonics MUCH greater than the MorningStar unit, so in a small space and other electronics that could be an issue.

Solar Guppy

Re: Charge Controller Opinions - Small RV Install

Windsun wrote: »

The catch is in the details.

The Morningstar has a much better MPPT tracking algorithm, so it's overall average efficiency is better. Better in fact than the Outback Power MX60.

While Blue Sky have a max of 95-97%, you will only see that about 60% of the time, with the Morningstar it is more like 80% of the time.

In the 15amp power range, there are no controllers better performance wise, efficiency and harvest ( harvest is how good the mppt tracks )

As I just posted, the MorningStar unit will be in the mid 90's, even at low power, its has to below 5 watts to get down to 80%, its less than 500 mw active and switching tar loss, compared to 4-8 watts on Large Mppt units like the WX units

BB.

Re: Charge Controller Opinions - Small RV Install

technomadia wrote: »

One other concern I just discovered reading the MorningStar documentation... The float voltage is fixed at 13.7V, which is significantly above the 13.3V recommended by LifeLine.

From the Morning Star manual link (PDF) posted above:

Custom charging and load setpoints can be programmed into
SSMPPT non-volatile memory using a PC with Morningstar MSView
software installed and a Meterbus to Serial Adapter (model: MSC).
Refer to the MSView help fi les for detailed instructions. MSView PC
software is available for free on our website at:

http://www.morningstarcorp.com/

A setup wizard will guide you through the set point configuration
process. Refer to MSView help fi les for more information.

Nice looking controller... Well documented.

-Bill

System2

Re: Charge Controller Opinions - Small RV Install

Solar Guppy wrote: »

The SunSaver is about 3% better efficiency and MUCH better mppt. The Sunsaver is low cost to just add SunSavers as your system needs grown ... a pair is 30 amps and cost wise not much more than a BlueSky 30 amp unit

BlueSky are well built units, buy very dated technology wise

I'm looking to put together a solar install on my boat, and it is fairly similar in size.

I have a 184AH AGM 12V battery bank, and need something to charge it up now that I'm off shore-power.

I was planning to start with one Kyocera 135W panel, and I believe I have room for two or three total later. I will probably want the second one, but don't know if I'll need the third.

I was looking at the Blue Sky 2512iX here...but the Sunsaver MPPT-15 looks good, and is said to be more efficient around here, and looks like it will hold up in a marine environment better...EXCEPT for two things that make me uncertain.

1. It isn't rated for the output of two panels (270W vs. 200W)
2. I thought I read somewhere that these units won't behave well in parallel with eachother.

Am I worrying about nothing here?

FYI -- Until I found this forum I was looking at BZ Products MPPT250 / MPPT500 units. Thanks for the warnings!!!

BB.

Re: Charge Controller Opinions - Small RV Install

whimsy wrote: »

I was planning to start with one Kyocera 135W panel, and I believe I have room for two or three total later. I will probably want the second one, but don't know if I'll need the third.

...but the Sunsaver MPPT-15 looks good, and is said to be more efficient around here, and looks like it will hold up in a marine environment better...EXCEPT for two things that make me uncertain.

1. It isn't rated for the output of two panels (270W vs. 200W)

First, virtually all (the little that I know) MPPT charge controllers self limit their output current to the "rated output"... So there is no issue/damage from installing more Watts of solar panels than the unit is designed to output (within reason--you have to meet the Vmp/Voc/Imp/Isc ratings input ratings and may need to install an extra input fuse.

Second, realistically in anything other than cold conditions (near freezing or lower)--It is reasonable to expect a charge controller to output ~0.77 of the solar panel rating (sort of the cost effective point for solar panel _ charge controller costs)... Working backwards, a 15 amp charge controller charging the batteries at 14.5 volts and 0.77 derating:

• 15 amps * 14.5 volts * 1/0.77 derating = 282 watts

So, roughly it will "cost effectively" manage a ~282 watt array very nicely... If you go much higher, you will begin to lose significant energy on good solar days as the controller hits its 15 amp output limit.

2. I thought I read somewhere that these units won't behave well in parallel with each other.

With many/most PWM charge controllers (the less expensive type), you can actually share one solar array with paralleled charge controllers/battery banks. May be nice when you want to charge the RV starting battery and the RV house battery from the same array.

MPPT charge controllers cannot share a common solar array for several technical reasons (MPPT won't work correctly).

However, within reason, any properly wired battery bank can support paralleled solar charge controllers, as well as other charging sources (AC battery charger, engine driven alternator, wind turbine--with correct charge controller, etc.).

What will happen with most charge controllers is that as the battery passes ~80-90% state of charge (getting nearly full), the chargers will not change states (bulk to absorb to float) in a synchronized manner. Also in absorb or float, one charge controller will probably supply the majority of the current (one may be at 14.5 volts and another set to 14.4 volts).

But this is not a problem--each controller is making its own charging decision and in these states, the battery bank is no longer accepting maximum charging current anyway--so it is natural for the charge controllers to cut back on charging current to keep from overcharging the battery bank. Outback (and possibly a couple other brands) do have a digital networking connection that "sync's" the charge states (as I understand)--but it is not needed.

Am I worrying about nothing here?

Ask your questions... You don't know if there is a problem until you get the answer(s) (and sometimes, there is more than one answer---the old "it depends" and "assumptions made" issues).

FYI -- Until I found this forum I was looking at BZ Products MPPT250 / MPPT500 units. Thanks for the warnings!!!

I have not read about anyone's experiences with BZ's controllers that are current production (the last reports were several years old)--Things can change (I have not heard anything changing--but I am not in the Solar RE business either).

Always confirm what you read here (and elsewhere)--We try to be clear and exact--but we (or at least me:roll:) are not perfect.

-Bill

niel

Re: Charge Controller Opinions - Small RV Install

my thought was to go for the controller that will fit your future needs as you mention 2 or 3 kc135 pvs and 3 pvs would certainly need more than one of the controllers you have mentioned. bluesky works, but is older technology so why pay big $ for something older? if one is going to shell out for the cost of 2 controllers then put that same money into one bigger and better controller and don't worry about if it will work right or be enough as it won't have to be paired with anything else and may even give you better wiring options over the 2 you just considered not to mention much farther capacity that just those 2 smaller paired controllers.

now in the smaller cc line you could go with one rogue mppt cc if certification of the cc won't be an issue for you as it has 30a capability and would solve your 2 controller dilemma in your future expansion, but will also limit the pv wiring options just as the 2 cc choices you mentioned would.

see this thread,
http://forum.solar-electric.com/showthread.php?t=4751

tallgirl

Re: Charge Controller Opinions - Small RV Install

I know everyone is hot for MPPT, but in an RV install I'd consider a SunSaver Duo. The advantage is that it will keep both PV and RV batteries charged with a single controller. It's a shame the Duo isn't MPPT, but ...

As for the question about running SC View on a Mac -- if it won't run on a Mac, my software supports the Morningstar gear and it runs natively on a Mac. As an added bonus, it will also support MS inverters and a PentaMetric, if you've got to know what's going on with your batteries.

System2

Re: Charge Controller Opinions - Small Marine Install

niel wrote: »

.... you could go with one rogue mppt cc if certification of the cc won't be an issue for you as it has 30a capability and would solve your 2 controller dilemma in your future expansion, but will also limit the pv wiring options just as the 2 cc choices you mentioned would.

see this thread,
http://forum.solar-electric.com/showthread.php?t=4751

I read quite a bit of that thread--and I'm really impressed to see EE's who could/have designed solar controllers discussing them. (My EE background doesn't include any power work, mostly digital stuff) From the discussion here, I like the system for places where it is a good fit.

But I don't expect a guy living inland off the grid and designing something primarily for his own use to be giving the attention I want to durability in a marine environment (humid, salty, damp, possibility of splashes, etc.) For this environment, I would like to see at least a conformal coating, if not full epoxy potting of the electronics. (Given the heat dissipation needs, fully potting the controller has its downside)

I'm also not as interested in higher voltage arrays--I'll have pretty short wiring runs, and from looking at specs, the higher wire losses will probably be a wash with the controller losing a percent or two of efficiency converting higher voltages down to ~12V for the batteries. (This wouldn't apply for higher voltage battery banks, but I'm sticking with 12V)

BB.

Re: Charge Controller Opinions - Small RV Install

I believe some of the Morning Star controllers are potted or conformal coated (Tropicalization)--For example the TS PWM family (PDF spec. sheet).

Don't think that you would want any charge controller subjected to salt spray.

-Bill

lorelec

Re: Charge Controller Opinions - Small Marine Install

whimsy wrote: »

But I don't expect a guy living inland off the grid and designing something primarily for his own use to be giving the attention I want to durability in a marine environment (humid, salty, damp, possibility of splashes, etc.) For this environment, I would like to see at least a conformal coating, if not full epoxy potting of the electronics. (Given the heat dissipation needs, fully potting the controller has its downside)

True, my controller wasn't designed with a marine environment in mind. I'm pretty clear in the manual that using it in such an environment isn't recommended, and will invalidate the warranty. But as Bill said, you don't really want to be using any controller in an environment that is subject to excessive humidity or especially salt. Even if the board is conformal coated, you still have connectors and possibly pushbuttons and a display that won't have any protection.

Marc

System2

Re: Charge Controller Opinions - Small Marine Install

No, I don't plan to immerse it or spray it with salt water. In fact I hope to keep such things away from it where I will be installing it. But this is a boat, and there is a lot of water around, and it can go unexpected places. So anything done to make the electronics less susceptible is good in my book.

The SunSaver MPPT-15 looks better protected than any other MPPT controller I have considered--at least from online pictures, brochures, and manuals. It appears to be partially epoxy potted and partly have a conformal coating from what I have read.

Also, they have replied to my email and assured me that as BB was saying--the 200W limit is that it won't push more than 15A into the batteries, and it won't be damaged by providing more than 200W of solar. They also told me that paralleling two of them will behave well as long as I keep the wires to the battery bank about the same length.

Thanks to BB and everybody else who offered me opinions around here!

Tallguy

Re: Charge Controller Opinions - Small RV Install

BB. wrote: »

MPPT charge controllers cannot share a common solar array for several technical reasons (MPPT won't work correctly).



-Bill

Bill, are you saying I cannot use a single MPPT controller for a "bank of batteries"?

I am also working on solar'izing my boat, starting up with a single 85 w / 12v panel but will want to expand, probably up to around 250W nominal.
I have been doing a lot of research on controllers.
Until yesterday I was pretty set on either Blueskies 1524IX, KZ 250 or sunsaver mppt.
My boat has 4 AGM (sealed 12v) batteries.
My plan is to install two 85W panels in series to make it 24V and later expand with 2 x 50W panels also in series, then wire the two pairs parallel into the controller.
The controller would be mounted inside (engine room or electrical panel), so the concern for salt water splashing etc is not present.

mike95490

Re: Charge Controller Opinions - Small RV Install

Several Charge Controllers can "share" one battery bank.

But you cannot (well, should not) mix different solar PV arrays to the input of a MPPT controller, as it will get confused, and not track mx power well.

Cariboocoot

Re: Charge Controller Opinions - Small RV Install

Tallguy wrote: »

Bill, are you saying I cannot use a single MPPT controller for a "bank of batteries"?

It's the other way 'round: you can not power more than one charge controller from the same solar panel array. Within the technical specifications for the equipment, a single charge controller may have any number of solar panels on its input and any number of batteries on its output. You can also charge a battery bank from more than one array/controller.

I am also working on solar'izing my boat, starting up with a single 85 w / 12v panel but will want to expand, probably up to around 250W nominal.
I have been doing a lot of research on controllers.
Until yesterday I was pretty set on either Blueskies 1524IX, KZ 250 or sunsaver mppt.
My boat has 4 AGM (sealed 12v) batteries.
My plan is to install two 85W panels in series to make it 24V and later expand with 2 x 50W panels also in series, then wire the two pairs parallel into the controller.
The controller would be mounted inside (engine room or electrical panel), so the concern for salt water splashing etc is not present.

Planning for expansion can be tricky. Make sure any charge controller you choose now can handle all the panels you plan to add later and that the wiring is heavy enough to handle any increase in current from the extra panels, both going in to the controller and going out of it.

Then you have to make sure your panels are compatible with each other, according to how they will be connected. For paralleling panels it is most important to have very close Vmp on all panels (within 10%). For adding them in series it is most important to have similar Imp (within 10%). This can be a problem if too much time elapses between "now" and "later" as sometimes panels go out of production and you can't find a match for your older panels.

BB.

Re: Charge Controller Opinions - Small RV Install

No---

The issue is that one solar array must go only to one MPPT charge controller.

You cannot, for example, have one solar array and two MPPT charge controllers charging separate battery banks (many PWM controllers can share a single solar array and charge multiple battery banks).

Basically, the MPPT charge controller is measuring the voltage and current it is drawing from the solar array and doing a Power-maximum=Vmp*Imp ...

If there are a couple MPPT controllers, they will confuse each other as each tries to measure and adjust the MPPT operating point on the solar panels. Basically, two or more MPPT controllers on one array will not collect the maximum power available.

On the other hand, you can have several arrays and several charge controllers (MPPT and/or PWM) and they can all charge the same battery bank just fine. Just "home run" the cables from each charge controller to the battery +/- bus connections. Using small wire and sharing a run back to the battery bank can confuse the charge controllers as to how full the battery bank really is.

I do not know what a "KZ" controller is... The Morning Star MPPT line if very nice, and the small SunSaver 15 amp MPPT controller is probably the best one out there for is size (most MPPT controllers are larger).

MPPT controllers when used on warmer locations (not freezing) are useful because they can take high voltage/low current from a solar array and down converter it efficiently to low voltage/high current to charge a battery bank.

Basically, you can run an array at 35-100 VDC or so (depending on controller) and reduce your current and wire gauge requirements to 1/2 or to 1/4 of what a PWM controller would require... Also allows you to run your panels much father away from your controller/battery bank too.

-Bill

Tallguy

Re: Charge Controller Opinions - Small RV Install

BB. wrote: »

No---



I do not know what a "KZ" controller is... The Morning Star MPPT line if very nice, and the small SunSaver 15 amp MPPT controller is probably the best one out there for is size (most MPPT controllers are larger).

MPPT controllers when used on warmer locations (not freezing) are useful because they can take high voltage/low current from a solar array and down converter it efficiently to low voltage/high current to charge a battery bank.

Basically, you can run an array at 35-100 VDC or so (depending on controller) and reduce your current and wire gauge requirements to 1/2 or to 1/4 of what a PWM controller would require... Also allows you to run your panels much father away from your controller/battery bank too.

-Bill

WOW, you guys are great.. and fast.
I meant the BZ mppt 250.. or the sunsaver 15 amp.
but there are some awful reviews on this forum of the BZ, though those reviews are all from 2-3 years ago.. wonder if there are any new'er reviews.

it makes sense that the cc mppt really will be most effective if onle one panel is attached, but if the other panels are identical, and mounted nearly the same position and in similar azimuth then i would guess the Vmp/Imp would be very similar in both pv arrays?
would the system be more effective wired in series or parallel?

Cariboocoot

Re: Charge Controller Opinions - Small RV Install

Stories of the BZ controller's shortcomings are legend around here. They include two brand new ones not working right out of the box, and output that was actually far less than input. The latest "update" on them is wanting to charge people money for "upgrading" their dysfunctional equipment to something that supposedly works. When a company taints itself with poor product and support as badly as they have it is highly unlikely they'll get many repeat customers.

it makes sense that the cc mppt really will be most effective if onle one panel is attached, but if the other panels are identical, and mounted nearly the same position and in similar azimuth then i would guess the Vmp/Imp would be very similar in both pv arrays?
would the system be more effective wired in series or parallel?

I think you're still missing it. One MPPT charge controller can have an array consisting of many panels. In fact they're rather a waste of money on a small array. What you can not do is power two MPPT controllers from one array. A single array is considered to be made up of similar PV panels connected in serial, parallel, or a combination of both and having the same physical location/orientation (i.e. next to each other).

The other problem which i think is influencing your understanding is trying to power one MPPT controller off two arrays with different power values (either due to differences in the panel specifications or orientations). That also does not work.

Bill's description of them becoming "confused" is something of an understatement. :roll:

BB.

Re: Charge Controller Opinions - Small RV Install

You are very welcome TallGuy.

Tallguy wrote: »

...but there are some awful reviews on this forum of the BZ, though those reviews are all from 2-3 years ago.. wonder if there are any new'er reviews.

I have not seen any updated controllers--But I am not in the solar business (what you see here is me+solar). There is enough good hardware out there that you probably don't need to take a chance on a new BZ model (older models can have worse performance than a light switch and a piece of wire).

In the end, you get what you pay for. We have seen many controllers over the years that advertise they are "MPPT"--and, of course, they are not. Don't even have the hardware required to make MPPT controller (basically, you need some inductors to store and down convert voltage/current efficiently).

Morning Star MPPT, Midnite Solar, Rogue (although, it appears that we are waiting for a new model for shipments to resume), Outback, Xantrex, etc. all make very nice and functional MPPT charge controllers (lots of experience here by many posters/users).

If you need a ~30 amp 12/24 volt MPPT controller, you might check with Rogue for a very nice price performance (when new unit comes out--I hope).

MorningStar makes very nice units--but they do add costs with their "accessories" (digital display, comm. adapter for PC comm., etc.).

it makes sense that the cc mppt really will be most effective if onle one panel is attached, but if the other panels are identical, and mounted nearly the same position and in similar azimuth then i would guess the Vmp/Imp would be very similar in both pv arrays?

The array can be 1-XX set of solar panels, typically of the same brand/model number, matched to series/parallel connections that match the total number of panels/watts and controller input requirements (which also have to take into account battery bank voltage rating too).

would the system be more effective wired in series or parallel?

For PWM (cheaper, but certainly rugged, reliable, functional). the solar Vmp-array should be matched as follows:

• 12 VDC battery bank => Vmp~17.5 volts
• 24 VDC battery bank => Vmp~35 volts
• 48 VDC battery bank => Vmp~70 volts

Lower voltage, and you may have problems fully charging your battery bank. Higher than the above, your panels are "wasting energy" (PWM can only use ~17.5 volts, a 35 volt Vmp on a 12 volt battery will waste ~1/2 the available panel wattage).

MPPT controllers have the same Vmp-array minimum voltage requirements as above...

However, their maximum input voltage may run from ~40 volts to ~150 volts input for Voc-array-cold... The smaller/less expensive controllers have lower input voltage limits. The more expensive have the 150 VDC (or even 250+VDC) voltage limits...

For a typical larger MPPT controller, they have ~150 VDC Voc-cold limit... Which usually works out to around Vmp~100 VDC maximum (low ambient temperatures increase Vmp/Voc).

So, depending on the controller and your requirements, you will probably have a series/parallel arrangement to meet your controller's input requirements.

Some MPPT controllers have Voc only a little above Vbatt... Others are most efficient with Vmp~2xVbatt, and others are efficient throughout pretty much the whole range.

Usually, it is better to setup your basic requirements (load, battery size, solar array size), then pick/massage your hardware picks for "optimum" price/performance for your need.

It is easier to give an "exact" answer to specific brand/model/configuration questions than a "generic" answer--Because there are so many variations between vendors / products.

-Bill