Trojan, Crown or Powerline?

[Scruff]

Steam's what turns magnetic fields in an awful lottov our power stations to this day. 

[Pord]

Ach, every step brings unfamiliar territory with a new challenge!  Scruff, can I ask for your further help please? 

I've now had the Crowns for around 2.5 weeks. They came fully charged (I'm informed) and I expected to have the panels and kit all connected by now but unexpected delays means this won't happen for possibly another two weeks.  I went to test the SG yesterday but my brand new hydrometer came out the box broken and the replacement won't be here for a couple of days.  I'm assuming they will gradually lose charge and need a top up soon.  I'm assuming my genny would take way too many hours to charge so would the simplest short term option be an off-the-shelf mains battery charger and a favour from a nearby friend with mains power?  Any suggested make or model to choose/avoid? Presumably I could use either a 6v or 12v model, but I don't yet have battery connectors for the 12v/series option and I was waiting for my electrician to bring those (with relevant knowledge).

Thanks...

[offthegridandy]

Hi Pord,

I shouldn't worry to much about the stae if charge (SOC).  If they were delivered fully charge, which is normal and are not connected or in use they shouldn't come to any harm for a few eeeks.  You could check the battery voltage if your conncerned. Just put a accurate voltmeter across each pos and neg terminal ideally you'd expect get 2.2V.

Andy

[splyn]

I'm assuming my genny would take way too many hours to charge so would the simplest short term option be an off-the-shelf mains battery charger and a favour from a nearby friend with mains power?

Hmm, that could be a problem. Have you used PVGIS to estimate your PV generation and battery useage? If not you really should as it's a fabulous resource:

http://re.jrc.ec.europa.eu/pvgis/apps4/pvest.php?lang=en&map=europe

Select your location on the map and select the Standalone-PV tab. I entered Aberfoyle, 1000W panel, Discharge cutoff limit (%) set to 20% ( ie. the absolute maximum you'd want to discharge to), 24V 220Ah battery, 1000Wh daily consumption and 82 degrees module inclination (for best winter performance). If your location has any shading issues from local topology, trees etc. (which will be much worse in winter of course) then create and upload a horizon file to improve results.

The results estimate that the batteries will be empty on (ie. 80% discharged) on 30% of days in November and 60% in December! You might need the genset rather more than you'd hoped in winter - especially since you don't want to run the batteries down to 20% then leaving them discharged for days or weeks. You will also need to equalize them periodically which will take many hours on the generator. Good luck.

For those who haven't seen/tried it, there is a beta of a newer version available as well:

http://re.jrc.ec.europa.eu/pvg_tools/en/tools.html#DR

This has two big new features: (a) you can select from 4 different databases (2 in the current version) and (b) you can download the solar insolation data for your location for periods between 2005 and 2016 (varies between databases). That allows you to model your consumption and battery state of choice to get more detail than the summaries provided by the online tools. For instance, you could find out the longest periods when the battery gets little to no charge rather than the average over many years.

Select 'HOURLY DATA', select the year(s), slope and azimuth of the panel, select 'Radiation components' and click 'Download csv' to get hourly data for the whole period.

Now the worse news is that the new version of the tool produces even worse results with the default (PVGIS-CMSAF) database. Selecting OFF-GRID, 5280Wh battery, 20% cutoff and 82 degree slope, click 'Vizualize results' and selecting PDF gave 96% of days in December with the battery empty!

[Scruff]

Hi Pord,

I'd expect your 6v batteries to be 6.3V from factory. It's not normal for battery handlers to charge batteries and I believe they'll accept an 8 hour charge as you have them.
They're shipped dry. The handler fills them with acid (sometimes incorrectly) level and specific gravity ought to be checked after first charge completion to verify fidelity.

Battery sellers tell me the batteries are inert after this process as no degenerative cycling has taken place there is no upsetting chemistry inside to be transmuted with electricity. Don't worry about storing them the sellar has had them on the shelf for months. You can find the manufacture date in the code ingraved on top.
Chargers I say morningstar or nought...never met another like 'em. I heart them so much I run them as mains chargers too because I'm tired of wasting money on other brands just to say I found one that's fit for porpoise too so I don't sound biased on the subject.
ProNautic make the best mains charger I've tested and it still only cuts a specific gravity of 1.265

You can make links from drilled copper/aluminium flat bar or just use an old set of jump leads replacing the croc clips with automotive terminals for battery interconnects.


 
Notes on drawing..old draft;
PE to DC Ground Bus ought to be 25mm² (one size smaller than cable on largest fixture) and system could benefit from a dedicated inverter DC Isolator for service work ie. work on the AC system can be carried out in isolation from an operational 24V system.

[Pord]

Thanks gents for such great input (again).

Scruff, really appreciate that advice and the wiring diagram. I'm relieved that the batteries will be ok in storage for a wee while yet. I had to put everything on hold to prepare for the visit by Ophelia, including dismantling my workshop marquee before the storm did it for me...

Splyn, thanks for that. Yes, I have done my calcs and had seen that website, although I used the calculators on Michael Boxwell's Solar Electricity Handbook site (as recommended elsewhere on this very forum). I now need to move beyond the theoretical stage if I'm ever going to get to grips with this stuff, hence doing my calcs, taking the plunge and buying the kit. Something odd about the average daily energy production displayed by the jrc site, though. It calculates a max daily average generated of just 800wh even at the peak month of May, which has an average irradiance value of between 4 and 5 and theoretically should give me an average of 4-5kw production.

Regardless, I'll find out the hard way in good time! What is guaranteed is that I'll have more questions...

[splyn]

Something odd about the average daily energy production displayed by the jrc site, though. It calculates a max daily average generated of just 800wh even at the peak month of May, which has an average irradiance value of between 4 and 5 and theoretically should give me an average of 4-5kw production.

The panels won't generate any more energy than is actually used (or wasted) thus the daily generation figure shown will be the lower of the actual total generated each day or the energy consumed plus the energy that can be stored in the battery. Thus in May the panels aren't going to produce more than the 800Wh (that I presume you entered as your daily consumption) given that the batteries are going to be fully charged most of the time.

I assume the simulation doesn't account for battery charging losses.