Recommendations please...

kiwial

Hi all,

stumbled across this site when doing a search for reviews on the BZ MPPT controller & quickly decided they were not right for our application... Have read through some of the threads but would really appreciate some advice for our situation.

We live half the year (summer) in the UK on a canal boat & already have a 12V battery bank of 4 x 270Ah batteries (http://www.tayna.co.uk/ELECSOL-270-Carbon-Fibre-Battery-P5652.html) which we charge through a combination of alternator (via a 4 stage regulator) on the engine and a single 12V 130W panel & basic MPPT regulator. The panel works well but doesn't keep up with our power requirements (small domestic sized fridge etc) so we're looking at adding a couple more panels. Over here, 24V panels are generally a lot better value & I've found a 200W panel at a competitive price (http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=120598896724&ssPageName=STRK:MEWAX:IT).

My question is, which regulator would people here recommend for 2 of these 24V panels into a 12V system? MPPT seems to be a good option & it seems the Morningstar controllers rate well on here (although pricey). Any advice greatly appreciated - we're in the US in a couple of weeks & prices over there are far more reasonable than for the same thing in the UK so we're hoping to pick one up while we're there.

Also, I realise it's not possible to mix the 12 & 24V panels but would there be any issue with inputting them both into the same battery bank through their own regs?

By the way, we're not that concerned with winter performance as the boat goes into storage but even in winter it's always above freezing at some point during the day.

Thanks very much!

Regards,
Allan

mike95490

Re: Recommendations please...

The panel works well but doesn't keep up with our power requirements (small domestic sized fridge etc) so we're looking at adding a couple more panels.

Most fridges will consume 1KW of power, daily. Any panels you add will help, and adding a small eu1000 genset (to avoid running the boat engine) and a charger run off the genset, will GREATLY inprove your watts / liter of fuel.

Likely most your stuff is designed around 12V, so changing battery voltage is out.

The morningstar 60A MPPT charger, into 12V, will only manage 60 A, or 900W of PV (and it has all the web html goodies in it.)

That's about all of my free advice I can think of today.

BB.

Re: Recommendations please...

Controller wise, any of the Xantrex, MorningStar, or Rogue controllers are fine.

MorningStar 45/60 amp MPPT are probably one of the most advanced at this point (efficiency, 60 amp model includes a small web server too). Rogue MPPT is a nice stand-a-lone controller for 12/24 volt systems (30 amp).

For >18 volt Vmp (voltage maxim power) panels, you really need an MPPT controller (as you have said).

And yes, you can run parallel charge controllers and attach them to the common Battery +/- bus.

Some good rules of thumb for charging a battery bank is somewhere around 5% to 13% of the 20 Hour capacity... Your battery bank:

• 4 x 270Ah = 1,080 AH of batteries
• 1,080 AH * 0.05 = 54 amps minimum
• 1,080 AH * 0.13 = 140 amps maximum

You are planning on 2x200 watt panels, an MPPT charge controller rating at 12 volts would be (0.77 is a typical derating we use to reflect the maximum output typically seen from XXX watts of solar panels on a MPPT controller):

• 400 watts * 1/14.5 volts charging * 0.77 panel+charge controller derating = 21 amps

So, a 30 amp MPPT controller is large enough for now (unless you plan to add more panels later).

You are still under the ideal charging current for your battery bank (~54 amps minimum)--so you will still need to use your engine charger to keep them fully charged.

You should probably measure your loads and see if you can do anything more efficiently. The newer energy star refrigerators are much more efficient than those from a decade or more ago. Also, few people have done conversions of a chest freezer to a chest refrigerator and found that saved quite a bit of energy.

Something else you may want to look at--A Battery Monitor (or Victron Energy--a European mfgr) can help you better monitor the state of charge of your battery bank and how your loads/charging are balancing out.

How many solar panels vs how much fuel you use to keep your bank up is your question to answer... However, making sure you treat your batteries well can dramatically improve their chances for a long life.

Deep Cycle Battery FAQ
www.batteryfaq.org

-Bill

niel

Re: Recommendations please...

on a sidenote, you will have a great deal invested here so when you leave it for the winter take all of it with you except for the original 130w pv and the smallest of controllers you'll have or you may lose it to theft. the batteries really only need a small maintenance charge for overwintering.

kiwial

Re: Recommendations please...

Thank you all for your input - greatly appreciated!

We do have a small genset as well but it's petrol & that means storing extra fuel (& carrying it from the nearest gas station...)

The smallest Xantrex MPPT seems to be a 60A, which is overkill for our situation, as Bill said. So that leaves a choice between the 30A Rogue MPT-3024 ($295) & the 45A Morningstar TriStar ($428.40) - a difference in price of around $135...

If we go for the Rogue, that'll be at capacity but with the Morningstar we could add another 200W panel if we wanted. This is probably unlikely but, knowing me, if I know the capacity is there I may just be tempted (which could be another reason to go for the Rogue ) Apart from possible extra capacity, are there $135 worth of other benefits to the Morningstar? I admit it would be interesting to have the "200 days of data logging", because part of this exercise is a bit of a learning experiment for me: in a few years time we intend to build off-grid in New Zealand & I'd rather cut my teeth on a relatively cheap system here first.

When we're out of the UK, the boat goes into a secure marina & we can store the panels inside the boat. She's essentially a 65ft steel box so pretty hard to get into

Thanks again!

- Allan

BB.

Re: Recommendations please...

The Rogue, has some statistics too... Although--I would spend the extra money for a Battery Monitor (I think it is more useful as the battery can be easily killed by under charging).

As I understand, only the 60 amp MorningStar MPPT has the Ethernet server (I could be wrong too).

-Bill

kiwial

Re: Recommendations please...

Thanks Bill,

the server's of little value to us, but the 45A version still has logging capabilities - you just have to plug comp directly into it.

Already have a battery monitor that works pretty well - although it's near impossible (afaik) to give a completely accurate battery state, this one adjusts over the life of the battery & is supposed to be within 5% accuracy.

Leaning towards the Morningstar...

Thanks,
Allan

kiwial

Re: Recommendations please...

Hi again,

I misread your post Bill & now I realise what you mean about stats. After speaking with the solar panel supplier, he'll give me a tiny discount to buy 3 panels instead of 2 so I can't see a lot of value in getting the extra 15A capacity. After reading a few reviews, my thoughts have moved to the Rogue simply because the extra cost of the Morningstar probably won't be justified... Have to order tomorrow so that I can get whichever one I decide on delivered to the in-laws in NJ by the end of the week as we're over that way in 8 days time.

Thanks,
Allan

BB.

Re: Recommendations please...

The EBay information has "gone away"... One thing to double check is the Voc of the solar panels vs the Vmax input of the Rogue.

If I remember correctly, your panels are fine for the Rogue--But I just want to make sure. The MorningStar MPPT (and Xantrex+other higher capacity) controllers have a higher input voltage rating than the Rogue.

For your needs--either type of controller will be fine for your setup.

-Bill

dmiller

Re: Recommendations please...

Any pics you would share of the canal boat?

You can probably derate the panels for calculations if kept flat at northern latitude. Unless you plan to take to the open sea and head south. Using a lower watt calculation would matter if the Rogue was borderline as far as capacity.
But sizing a controller to allow the addition of a panel in the future is probably the way to go, unless you absolutely can not fit a future additional unit.
Another issue for cc with some mobile applications is being at lower numbers in thermal design. Probably not an issue in a canal boat as it would be in a vehicle in the U.S. Most mobile CC in the U.S. will spend a portion of the time running in 100F plus air temps. Probably not something that's good to do near 100% capacity.

I'm not sure if it was mentioned that in your app you wouldn't want to put any panels in series.

dmiller

Re: Recommendations please...

BB. wrote: »

.......

As I understand, only the 60 amp MorningStar MPPT has the Ethernet server (I could be wrong too).

-Bill

The 45 amp does not have the simple RJ45 connection that is on the 60amp, but it does seem to have a data collection system. Their meterbus system likely runs over ethernet and the 45 amp units must participate. So it may be possible to read the 45 amp unit over a serial or other connection.
So the questions are how and how much extra $$, if any, to connect
Since I run an always on ethernet network anyways, the 60 amp unit is just about ideal for me. That is if the RFI is more like the XW and less like the outback cc.
Morningstar setup is pretty ancient, with the dip switches and an optional serial interface. Nice for the installer who doesn't want his system messed with. But not as friendly or interesting for the do-it-yourselfer.
I'm a bit surprised you guys are completely comfortable recommending the Rogue with 400w of panels and 1000ah of storage. Especially with that much storage capacity it's an evolutionary process to figure out the preferred way to run the boat. The Rogue an "evolutionary" dead end at 30 amps. There has to be an efficiency cost of multiple cc's past the bulk stage. With any more panels in the future he's at 3 cc on one bank. There is no way that past bulk that a bunch of different charge controllers can make near optimal decisions. If the system isn't designed for high efficiency why pay for MPPT controllers?

BB.

Re: Recommendations please...

The recommendation was based on the amount of solar panels that the original poster wanted to add (for whatever reason). More of a $$$/features ratio for him.

Having a large charge controller with a small amount of solar panels does not do anyone much good (note that the MorningStar 45/60 amp MPPT controllers are supposed to be quite efficient at lower power levels too).

If I recall correctly, the Vmp of the solar panels Allan is looking at is well above the ~17.5 volts that is around optimum for charging a 12 volt bank with a PWM controller... So MPPT was the next logical choice. And the Rogue seems to fill a nice space at 30 amps and below with a "just works" functionality at a nice price point.

-Bill

kiwial

Re: Recommendations please...

Ok, the last 2 posts are getting a bit beyond my knowledge of this stuff so I'll just agree & nod wisely

Just to reiterate - this is partially practical & partially an experiment to learn a bit for when we go completely off grid in New Zealand (& will need a pretty full-on combination system but that's a story for another day). Techology will undoubtedly change in the next 5 years so there's little point in having the capacity for future-proofing given the situation. We go back & forth between UK & NZ (i.e. no summers) but it's unlikely we will do this for any significant length of time. For 2 years we've mainly relied on the engine for charging so we're not expecting to totally rely on solar. Have also decided we won't be extending the system past the 2 extra panels.

Bear in mind that it will never be optimal conditions on the roof of a boat as 1) we move around & will probably not go to the trouble of getting fully adjustable mounts 2) this is England & we rarely even see the sun

Link to the panel is still working for me but here are the specs:

* Rated Power: 200 W
* Tolerance: (+/-) 3 W
* Max Vm Voltage: 26.24 V
* Max Im Current: 7.63 A
* Voc Open Circuit: 32.89 V
* Isc Short Circuit: 8.02 A

FYI, I got an email from the makers of the Rogue device who said the panels will be fine as long as they are in parallel (series would make the Vmax too high). So apart from some extra cable, there's no big issue with that.

Will keep you all posted & will also get a few pics once it's sorted.

Thanks very much!!

Regards,
Allan