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Old 05-19-16, 03:45 AM   #52
Redmohawk
Lurking Renovator
 
Join Date: Jul 2015
Location: Victoria , Australia
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Quote:
Originally Posted by Robaroni View Post
What do you do when a single cell goes bad on your lithium battery? How do you detect it?
If you have a lithium battery pack, then you have a lot of low voltage single cells. How do you change it?

With all the problems of L/A batteries they still have a place in home installs.

You keep saying "To go off grid is completely in reach." For whom? Certainly not the person living in the suburbs on a 100 x 100 lot. you can't use your situation as the paradigm for everyone. This is how people get in trouble, you have to qualify your statement.

Rob
First :- Lead acid is a series of lower voltage cells ...... 2.15V as opposed to 3.65v for lithium . So really lead acid has more cells per volt than lithium.

Depending on what sort of lead acid battery you use (IE single cell flooded or sealed lead acid AGM) swapping out a single cell or loosing 5 good cells because one goes dead in a 12v unit is either the same or worse than a single lithium cell going bad.

Second :- Most large format lead acid management systems do not look on a per cell basis , a few do , most rely on you personally checking with a hydrometer for single cells or management burps cells for balance (not best setup for cell life long term.

Third:- Lithium battery management generally works on a per cell basis and most good units can switch out a bad cell, if it goes bad or in charging , more modern lithium "packs" like the Tesla unit run direct PV voltages (350v etc) so run more cells than your average lead acid unit and can operate with several dead cells switched out. Really smart units are linked to the web and could call out maintenance before total battery failure is an issue.

Forth :- several off grid systems operate here in Aus in our larger city's one comes to mind that is a particularly difficult install. Located in Melbourne Victoria Australia , coastal town in a major capital city of mainland Aus

Latitude: 37°48′50″ S
Longitude: 144°57′47″ E
Elevation above sea level: 25 m = 82 ft

Average weather data

Climate statistics for Australian locations

As you can see not Arctic conditions of cooler parts of Europe/Canada but far from sunny ideal Solar conditions.

Yet with a 14m X 45m plot surrounded by 12m high vibrated concrete and brick industrial buildings and only a single car width lane way a 2 bedroom house was built from recycled building materials for less than $40,000 Aus (average build price for an Aus 4 bedroom home is $360,000).

It uses evacuated tube hot water , 100% battery backed (lead acid) off grid solar , 100% rain water , reticulation system removed (at great pain of council and nashing of teath in protest) , All waste water is processed on site to better than drinking water status on site using composting/worm toilet/reed bed system.

Heating is wood fired with a grain heater planed I believe (I haven't visited the site in many years, have lost touch with them) 3 people lived there , 2 adults and an older teen.

They had a significant garden, one being Vegetarian this was a strong priority , large parts of their diet came from the house plot.

This all "just" out of the CBD (about 5km) in an industrial area on a site no one wanted (to small for a industrial shed, bad access etc, dark and surrounded by sheds scared off most people looking to build a house) block sold for a pittance because of this , in an area just 2km up the road a block half the size sells for $1.1 million with a Victorian style terrace house .

100% off grid is not out of reach of most , Settlers lived in wood shacks in places with permafrost areas for 100's of years "Off grid" .

What it comes down to is what are you happy to live with ? Live in a tent year round and a led light powered by a 12v AGM and solar panel might be enough to keep you happy. Live in a 6 bedroom house in the Arctic circle with energy hungry kids and like to weld with a 250 amp welder every day consuming 30 kw/h a day and your up for some big coin. BUT its not imposable .
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