Navitron Renewable Energy and Sustainability Forum

Energy/Electricity Storage and Use/Grid Connection => Off-Grid, Batteries & Inverters => Topic started by: shadiya on May 02, 2010, 01:22:17 PM

Title: Newbie help please
Post by: shadiya on May 02, 2010, 01:22:17 PM
Looking at buying some secondhand equipment for my off grid system that doesn't exist properly yet.... By which I mean, I live off grid but the sysem is highly Heath Robinson and not very efficient and is on the list of things to do to sort out. I understand very little about electrickery so looking things up on the internet is a bit of a waste of time as it makes no sense to me.... Could somebody clever tell me whether the Victron Phoenix inverter charger is a good buy? And also the Steca charge controller? Thank you  :)

Title: Re: Newbie help please
Post by: martin on May 02, 2010, 01:36:36 PM
both are top notch and recommended pieces of kit, BUT, if you have a lack of knowledge, have a good read of the forum, it should give you some good pointers, and if you can't find an answer - ask! There's lots of helpful people who've probably trodden the same path before, and using their experience could save you literally thousands of pounds...... ;)
Do your sums very carefully first, start with your projected consumption, then get things like battery bank size correct etc...... "Work backwards" is a good adage

Title: Re: Newbie help please
Post by: Justme on May 02, 2010, 05:35:05 PM
As has been said both are good bits of kit but could be the wrong good bits of kit for what you need / want.

If you post more information (the more the better) about your system then you might get a more accurate reply.

Title: Re: Newbie help please
Post by: Billy on May 02, 2010, 07:17:04 PM
Hi Shadiya,

I concur, both Victron and Stecca are good brands, but it does depend on what you do with them!



Title: Re: Newbie help please
Post by: shadiya on May 03, 2010, 12:10:07 PM
Well, the small problem with having a Heath Robinson off grid system is that it doesn't work that well and so trawling the internet isn't really an option unfortunately, which is why I've asked for advice. Plus there is the comprehension problem, don't seem to be able to retain the electrical know how for some reason, despite scores of explanations that make sense at the time....

I have a small farm and at the moment have this system -

2 x 30w BP solar panels and 1 x 43w Solar Technology panel which are wired up to a 12volt lighting system that a friend put in using car wire I think and a rather ancient battery, which works reasonably well though probably not as well as it should.

I also have 6 x 80w panels that I bought ex BT from ebay that are wired up to a battery bank of four 105 batteries and wired through a 300w inverter. This system hardly works at all as the so called expert who wired it up has put the battery bank etc a good 25m from the panels, we are sited in trees so they had to be in the sun and obviously, as he only used 2.5 household cable, very little power actuallyt arrives this end, hence I can't spend hours on the internet. Obviously, the solution to this is to move the batteries but this is a very busy time of year on farms and I haven't had time.....

In June, we will be having a 4.2kw wind turbine built and installed, based on the Hugh Piggott design that will run a separate system, possibly with some solar on top, not sure yet. It is also possible that I may move the large panel bank to add on to this system, but again, not quite sure. The system will be for the farm buildings and workshop, office and kitchen. I also have a Lister generator that hopefully will be working one day, again on the list of things to do.

I need to run various tools, normal sort of stuff really though I have just bought a welder. Not sure how much power that pulls so it may have to be a genny job. I do really need to be able to run a fridge as am starting small scale dairy production and need to be able to keep the milk chilled. I haven't got the fridge yet but will be looking for something of a reasonable size but will buy the most energy efficient one I can find - suggestions gratefully received.

This is a very broad overview but I am half way through building a solar shower block and have to go and get on with it as have some people here to help. I have lived off grid for the last three and a half years and am totally committed to using as little power as possible, so apart form power tool use and lighting and laptop, the only thing that really happens is battery charging.

Has been talk of 48 systems but this is where my eyes start to glaze over.... Was planning on leaving the decision on that to the people running the course who know far more about these things than I do.

Hope this is enough to be getting on with and thank you so much for your time, very much appreciated.

Title: Re: Newbie help please
Post by: shadiya on May 03, 2010, 12:13:30 PM
I forgot, I also have a Future Energy turbine that isn't up yet, rated at 1kw but think it only does 850

Title: Re: Newbie help please
Post by: billi on May 03, 2010, 05:43:00 PM
Hi shadiya

Less is more and keep it simple , get your basic system right , with potential to expand !
It sounds to me , you start in each corner and not in the centre !
Not that i am well organized , but you have to sit down and plan your system . You have to understand Your system Yourself (even only the Basics)

It is very satisfying to get positive results from own thoughts/installations

It is very  unsatisfying to get many things somehow connected and none is working ideal

Basic system is sure your mentioned  Victron Multi Plus (but what size ?) (it can use/utilise  your Lister Geny for battery charging- backup ) , the battery has to be big enough to deal with your desired Windturbines to absorb that power   ( or in other words you have to transfer power away from the battery in high wind situations )
Not every Steca  is a clever  Steca solar  charge controller , or in other words it needs thoughts how to combine your three to four different types of PV Modules


Title: Re: Newbie help please
Post by: Outtasight on May 04, 2010, 12:35:58 PM
Hi Shadiya,

The Victron is a good bit of kit.  As you mentioned, the main problem with the 6x 80W solar array is that it's very far from the battery bank and connected to it with damp string :D.

If you want to keep with the batteries and inverter as a 12V system you've only got three real choices:

A. Move the batteries to be right next to / under the panels.

B. Use a MPPT charge controller (like an Outback or a Morningstar - Stecca also make a low power one but 20A isn't enough for your amount of panels).  The Outback FM60 or Morningstar TriStar MPPT 60 would be my recommendations.  Using these controllers will allow you to connect all 6 panels in series and boost the DC voltage to about 140V while still charging a 12V battery at the other side.  This would allow you to keep the 2.5mm2 wiring from the panels to the controller.  It's an expensive option though as the controllers cost about 500-600.

C. Massively upgrade the wiring to the solar array.  At 25m length with 2.5mm2 cable the voltage drop for 37A of current is about 12.5V so it's little wonder you don't see much power going into the battery!  To keep the voltage loss to no more than 5% over that distance you'd need to be using 35mm2.  50m of 35mm2 cable isn't cheap either...

D. (Nobody expects D Spanish Inquisition!)..  Go for a higher voltage battery bank (24V or 48V) and a cheaper controller and upgrade the wiring (but not to such crazy sizes as you need for 12V).  Means binning the inverter and getting a new one that works at 24V or 48V though (also costs ).  No escaping this money-pit syndrome...

Option A is obviously the cheapest one.  Put the panels, batteries, charge controller and inverter close together and use the long 2.5mm2 cable run to deliver the 230VAC from the inverter to where you need it.  You'll have to build a weather-proof hut or something to keep the inverter from getting damp though.

The attached chart gives you an idea of the wiring sizes available / required for a given current and distance.  Conveniently your 6x 80W panels would put out about 480W and into a 13V battery (as it's charging) this is about 37A (or 10x the current I used in the table).  Just multiply the voltage losses by 10 and that tells you the total loss for 5m distance (round trip - there and back).  As you've got 25m to cover, just multiply that figure by another 5 to get the total.

So at 37A with 2.5mm2 cable you get 2.5V loss per 5m... so about 12.5V for the whole 25m wire run.  Obviously after the first 3V of loss your 12V battery stops charging properly and I reckon you're lucky if you see more than about 7A into your battery due to the wiring losses :(.

Title: Re: Newbie help please
Post by: shadiya on May 05, 2010, 09:50:49 PM
Thanks for your advice. As it happens, we moved the batteries on Tuesday so that's a good thing but the bad news is that we just realised that the wind turbine we were planning on building is 1kw not 4.2 so back to the drawing board on that one.... darn it.