Newbie. Hi and comments please

System · April 2007

Hi all. Been perusing this forum for a while now, it's a great source of info, thanks.

I'm about to DIY install a stand-alone 24V PV system for the first time. I'm living in Andalucia in Spain BTW. After much reading, shopping around etc I think I've finally decided on the combination of elements I'm going to employ which are:

4no MSK monocrystalline 210W panels
12no Hoppecke batteries, either 750Ah or 1125Ah - the latter being quite a bit more expensive obviously!
Victron Phoenix 24V/2000/60A invertor/charger.
Outback MX60 regulator (charge controller)

I've sourced all these locally to me but may purchase the Outback controller from an online (eBay) supplier in the States as it's quite a bit cheaper that way (about 300 euros cheaper!).
I'm not intending to use a genny for back-up charging just yet (although I do have an old petrol (gasoline) one....for emergencies!) but am thinking of adding a gas (butane) converted genny to the system next year, once I've got my first solar-powered winter under my belt, which is why I'm going for an invertor/charger rather than just an invertor at this stage. I have disounted a tracking system so this will be a fixed array. This is for a single-person household, running lighting, household appliances etc but not cooking/refrigeration which will all be by butane gas.

I would welcome any comments, positive or otherwise, on the pros and cons etc of my proposed system, cos you guys are the experts! The next project, once this is up and running, is a solar pumping system!

Thanks!

BB. · April 2007

Re: Newbie. Hi and comments please

Welcome HB,

My questions/concerns... Watch your battery charge (should you get a battery meter like below?)--Batteries are easy to kill in a few months with excessive discharging and poor charging (both over and undercharging can destroy batteries). Monitoring current in / out is about the best way to ensure that your batteries remain healthy.

http://store.solar-electric.com/metersmonitors.html

My next question is are you on-grid or off-grid (do you have utility power or only generator power). Basically, this is again regarding the health of the batteries. You can always turn off the TV/Radio or go a few days without clean cloths--but you don't want to let the batteries sit around discharged for any major period of time (even a few days at >50% discharge--if I understand correctly) will slowly begin to cause the battery to lose capacity to fully recharge.

So--even if you gas generator is not the most efficient and automatically controlled by your inverter/solar charger system--ensuring you do have an operating generator handy for charging--when needed--will probably save you money in the long term with regards to the health of your battery.

My 2 cents worth.

Have Fun!
-Bill

crewzer · April 2007

Re: Newbie. Hi and comments please

Hillybilly,

Can you tell us more about the Hoppecke batteries (for example, model number)?

More later,
Jim / crewzer

System2 · April 2007

Re: Newbie. Hi and comments please

Hi and thanks. This is an off-grid system.
The Hoppecke batteries are the translucent Solarpower4 (750Ah) / Solarpower6 (1125Ah) models i.e. not the transparent OPzS ones but similar (apparently).
http://www.hoppecke.com/produkte/anwendungen__1/solar/solar_power

crewzer · April 2007

Re: Newbie. Hi and comments please

I'm about to DIY install a stand-alone 24V PV system…in Andalucia in Spain.

(Quantity 4) MSK monocrystalline 210W panels
(Quantity 12) Hoppecke batteries, either 750Ah or 1125Ah
Victron Phoenix 24V/2000/60A invertor/charger.
Outback MX60 regulator (charge controller)

The Hoppecke batteries are the translucent Solarpower4 (750Ah) / Solarpower6 (1125Ah) models

I would welcome any comments, positive or otherwise, on the pros and cons etc of my proposed system

Hillybilly,

Thanks for the additional information. Some comments and suggestions:

1) The Vmp for the MSK 210 PV modules is 25.8 V. For a nominal “24 V” system, I recommend you wire the 4 modules in a 2 x 2 array (51.6 V x 16.28 A total). The Outback MX60 controller’s DC-to-DC stepdown voltage conversion feature will make the necessary conversion to the battery voltage.

2) Assuming ~85% operating efficiency, the summertime mid-day charge current from the MX60 controller will be ~25 A. At just ~3% of the Ah capacity of a 24 V x 750 Ah battery bank, that’s a bit low, especially if you have daytime loads that will divert charging current from the batteries. Accordingly, I’d suggest the 750 Ah bank should be the largest that you consider. If you chose the larger batteries, you may have to also buy another pair of MSK 210 PV modules.

3) The Hoppecke site offers a lot of very good and useful technical information for your batteries. I recommend a thorough read of this material.

4) You may wish to double check the inverter/charger model number. I was only able to find a 24 V / 2000 W / 50 A model in the Victron Phoenix line. See:

5) High quality solar charge controllers use temperature compensation to vary the charging voltage according to battery temperature. I don’t believe that it ever gets very cold in Andalusia (north of Gibraltar?), but I suspect it can get quite warm (>35 C?). Accordingly, I recommend you also purchase the optional remote battery temperature sensor (RTS or BTS) for your MX60 controller, and perhaps for the inverter/charger as well.

I hope these comments and suggestions are helpful to you, and good luck with your system!

Regards,
Jim / crewzer

System2 · April 2007

Re: Newbie. Hi and comments please

Thanks once again.
I was indeed planning the 2x2 arrangement.

Hadn't thought about the battery sizing in that way so thanks! Will save me money too!

This is the Victron invertor/charger
http://generador-electrico.com/tienda/product_info.php?cPath=59&products_id=288&language=uk

You'd be surprised at how cold it gets here in the winter sometimes! >40C in the summer to just below freezing in the winter. Had snow the last 2 winters! I think I've been offered the temp sensor as an extra but had forgotten about it so will make sure that's included.

crewzer · April 2007

Re: Newbie. Hi and comments please

Hillybilly,

Sounds good! The link you provided does indeed describe a -60 model, but I'm still unable to find it in Victron's on-line catalog. Perhaps it is detail error (a "typo") by the vendor, perhaps it's a discontinued model, or perhaps sightly different models are available in different countries. It probably doesn't really matter, as either a -50 or a -60 model should work for your application.

Here's another Victron link for reference: http://www.victronenergy.com/upload/documents/Victron_MultiPlus_brochure_UK2.pdf

The standard temperature for battery specifications is 25 C (77 F). With your range of <0 C (<32 F) to >40 C (>104 F), the temp sensor is probably a basic requirement.

Best of luck with your system!

Regards,
Jim / crewzer

System2 · May 2007

Re: Newbie. Hi and comments please

crewzer wrote:

I'm about to DIY install a stand-alone 24V PV system…in Andalucia in Spain.

(Quantity 4) MSK monocrystalline 210W panels
(Quantity 12) Hoppecke batteries, either 750Ah or 1125Ah
Victron Phoenix 24V/2000/60A invertor/charger.
Outback MX60 regulator (charge controller)

The Hoppecke batteries are the translucent Solarpower4 (750Ah) / Solarpower6 (1125Ah) models

I would welcome any comments, positive or otherwise, on the pros and cons etc of my proposed system

Hillybilly,

Thanks for the additional information. Some comments and suggestions:

1) The Vmp for the MSK 210 PV modules is 25.8 V. For a nominal “24 V” system, I recommend you wire the 4 modules in a 2 x 2 array (51.6 V x 16.28 A total). The Outback MX60 controller’s DC-to-DC stepdown voltage conversion feature will make the necessary conversion to the battery voltage.

Hi Again. Sorry, probably just the next in a series of dumb q's!
Re your suggestion above, could you explain why a 2x2 array (51.6V x 16.28A) would be better than 4 in parallel (25.8V x 32.56A). Am trying to get my head round this and failing!

Also could somebody confirm that 2/0 wire gauge is actually 00 wire gauge?! I've seen it written both ways and of course I'm metric so want to make sure my conversions are correct!
Thanks again.

crewzer · May 2007

Re: Newbie. Hi and comments please

could you explain why a 2x2 array (51.6V x 16.28A) would be better than 4 in parallel (25.8V x 32.56A). Am trying to get my head round this and failing!

HB,

The Hoppecke specs suggest your “24 V” battery bank (12 x "2 V"/cell) will require ~28.8 V (@ ~ 20 C to 25 C) to reach the Absorb or EQ charging stages. The STC Vmp of your PV modules is just 25.8 V, and, due to the effects of PV cell warming in the Sun, the mid-day operating Vmp will usually be even lower (~-10%). Adding the voltage drop losses in the wiring and the controller will reduce the available charge voltage even further. The end result of trying to charge your batteries from a 1x4 array (“25.8V” x 32.56A) is that the batteries will likely never be driven to their target charge voltage, and their both their performance and longevity will suffer.

Configuring your four modules into a 2x2 array (51.6V x 16.28A) will deliver a relatively high source voltage to your MX60 controller. The controller will dynamically down-convert this input to the right combination of charge voltage and current for your batteries and their SOC.

A plus of using a 2X higher input voltage and 50% lower input current is that the power loss in the array-to-controller wiring will be reduced by 75%. A minus of this configuration is that the MX will suffer a slight reduction in operating efficiency.

I’m curious about your previous comment that you were already planning on the 2x2 configuration… why was that?

Also could somebody confirm that 2/0 wire gauge is actually 00 wire gauge?!

Yes, 2/0 = 00.

HTH,
Jim / crewzer

niel · May 2007

Re: Newbie. Hi and comments please

belated hello to you hillybilly,
i agree with all crewzer is saying except i'd recommend getting 6 of the pvs minimumly for your system making it a 3x2 and still using 2 in series, but 3 of these paralleled. being off grid you don't want to run marginally on the charging of the batteries especially when you'll be putting a drain on the batteries at the same time they are charging. if the bulk of the drain is during the times of solar charging even more pvs may be needed. i figured the 2 pv series pairs to roughly be at 3.2% of your capacity and if you drain the batteries down to 50% in a day you'll need to generate half of that 750ah for 375ah. this will take over 2 days to bring the batteries to full with the 2 series pairs. i did not reread it but i'm assuming that you will have 750ah at 24v for the battery capacity. if not then my calculations are not accurate and you may need even more charge current from pvs.
REMINDER- GET THE BATTERY TEMPERATURE SENSOR.

mike95490 · May 2007

Re: Newbie. Hi and comments please

Hi and thanks. This is an off-grid system.

Any chance you will install a diesel or some other emergency generator, or maybe plan on running a generator for a couple of hours in the AM, to get a bulk charge on the batteries, and let the solar top them off ?

System2 · May 2007

Re: Newbie. Hi and comments please

Thanks all once again - would have been back sooner but have dodgy internet connection!
I was originally planning the 2x2 array but then managed to talk myself out of it - I confused myself with pages of calcs into thinking that the regulator wouldn't cope with >50V. You've set my mind at rest now by explaining it to me!
I now have all the elements apart from the Outback - so, too late to change the array size. The Victron is definitely 60A.
Yes, I have a genny (petrol) and can connect it in via the invertor/charger.

Newbie. Hi and comments please

Comments

Categories