48v Battery Charger (from genny)

[rogeriko]

Here is a website that will calculate your off-grid electrical requirements. Choose your location and fill in your usage and production figures.

https://re.jrc.ec.europa.eu/pvg_tools/en/#SA

[billi]

kdmnx,

- If you're off-grid you need a generator. End of story. There are too many weeks in midwinter when PV just doesn't produce any significant power

Oh , so what about data collected  from forum members ?  about on average 1kWh per installed kWp during the winter months .... data logs can be found here https://www.navitron.org.uk/forum/index.php/topic,32329.0.html

So the possible 14 kWh for Andy per day during the winter is what you say not "any significant power"  

Sure the 20° Roof  of Andy will not be ideal in winter

Some people have found there is enough benefit to remove existing, working, lead batteries and replace them
with Lithium. I don't think anyone would chose Lead for a new installation.

Do you think so ?   Lets have a a look  your Li Battery with 12 kW Capacity (from your signature)
cost about 4500 GBP  that could buy  a decent flooded lead acid battery with a capacity of 100 kWh   that then would easily overcome those problems you describe  (even in summer) ,  to have a bad PV production day and runing out of battery  .  Not saying that 100 kWh is the right size here, but just to compare , and as you say to significantly reduce geny  run time  and utilize as much as possible of the PV in an off-grid setup , then certainly a bigger battery is necessary  

[billi]

This was a quote for a  new forklift Lead-Acid battery  including delivery from 2015

When seen/converted to C100 (capacity over 100 hours )  its about 45 kWh

That too will last at-least  a decade (but still works) , has a recycling value of 500 Euro after  and should be fine to  get discharged over night by 16 kWh plus  for an EV to provide  about 100 km  driving the next day 

Even if its cycled  down  to 50 % so take out  22 kWh  over night  it has a rated  cycle life of 3000 cycles ,
And remember these are the numbers provided by the manufacturer  to provide those until the BAT reches 80% of her capacity)

  just lets play a with theoretical numbers
if thats done  150 times (or 3000 times =20 years) a year and 100 km EV are taken out (rest is house-consumption  over night)

That would mean 15.000 km per year driving charged from you roof  .... 

Billi

[knighty]

I bought a ew pack for my forklift a few months ago... 48V 5PzS700

(24x 2v 700ah cells)

it was just short of £4000+vat


I shopped around, that was the best price I could find

[camillitech]

I bought a ew pack for my forklift a few months ago... 48V 5PzS700

(24x 2v 700ah cells)

it was just short of £4000+vat


I shopped around, that was the best price I could find

Me too, in October Knighty, 800Ah, cost me £3500 inc VAT and delivery to 'Timbuktu' (Raasay) from PB solutions St Helens.

Cheers, Paul

[andymb]

thanks to all for your input and info on the battery side of things

biff - I hope that you made a full recovery (even better than the batteries!!  )

could I ask another question to those of you with diesel generators - how do you avoid glazing of the cylinders if you only need to top the batteries up?
or would you try to coincide charging with running the washing machine/doing the hoovering/using power tools? I sometimes cant help that for us (fairly low electricity use apart from power tools) that a smaller LPG genny may still be more efficient? (can't help but aspire to a lister diesel though  )

now i think that I'll have a few days with pencil and paper trying to design a system - so thanks for all of your help and the links too.

andy

[camillitech]

could I ask another question to those of you with diesel generators - how do you avoid glazing of the cylinders if you only need to top the batteries up?

andy

Hi Andy, the answer is you do not 'top up' your batteries with a DG, you do that with your PV. You only use your DG to 'bulk charge' batteries. Configure your inverter to only bring your generator online when battery SOC reaches 60% and shuts down at 80%. You could could as low as 40% but if using FLA batteries I would not go below 50% personally. Another alternative would be to buy a larger DG than you need and 'hard wire' an immersion of 50% the genny's capacity into it. This is what I do but not because it is an efficient method but cos I acquired a 15kVA Lister when a 6kVA would have sufficed. Also, I have a 1500lt thermal store with a 6kW immersion in the bottom.

Good luck, Paul

[billi]

Andy ,

when i needed to start the diesel , or  petrol generator,  i  had both

I generally  run them to charge the battery  until it reached  the absorption phase or 80%  SoC   .

From say 50% - to 80% State of charge,  the Lead acid battery  takes  about all the  power you feed her ( well one should not overdo it , for my 40 kWh Battery i charged with 3-4 kW , as it is  a rule of the thump 1/10 of the BAT capacity) the efficiency  at this charging part of the battery  is supposed to be  way over 90 %
the last 20% of the full charge at a much lower efficiency i left it to the PV to finish that charge  .

I actually  tried to avoid  running washing machine and  powertools as it very often disturbed the smooth  operation of the generator
Also  when the generator is connected to the Inverter /charger  the generator power is switched though into the house and was by no means as clean as  what the Inverter charger would deliver .... so i also had an DC generator at one stage to charge the Battery directly  and left the house loads in peace and no flickering  of lights or the occasional
computer shutdown , or washing maschine  failed to run  .

Regards Billi

Oh  Paul was fast    
 

[heatherhopper]

andymb - interesting, if somewhat disjointed, thread. May have been better as several different posts? It took me some time to follow through the various "topics" and I am familiar with most of the questions/answers.

The decision to be on or off-grid is one you should make before you go any further with planning any kind of RE set-up. The requirements are very different. You have a temporary set-up which appears to be fine for now with presumably temporary low consumption. Frankly though it does not seem adequate for a permanent off-grid situation (excepting the PV), either as building blocks for the future or in it's type/quality. Sure you can start small and improve as you go, and there is merit in doing so, but without some forethought you will be likely end up with a yard full of incompatible and redundant stuff.

You should know just how much money you are prepared to throw into either option and whether this is a "hobby", green ambition, or a way of living - unlimited funds makes things easier of course, as with most things in life. Grid-tied you can tinker as much as you like and there will be little consequence if it doesn't quite work out and/or the initial enthusiasm wanes and some other interest takes over - you have a nice (mostly) dependable grid to fall back on. Off-grid is a way of living with no convenient switches to throw if it gets a bit bumpy and you will need to plan a system to meet all your current and future needs and factor in the inevitable ongoing issues and costs.

My take on a couple of your questions:

with regard to battery types, lots of you seasoned off gridders seem to favour flooded lead acid batteries - can I ask why?

I have been wrestling with the FLA/Lithium conundrum as my own FLA bank may need replacing in the next few years (currently 10 years old). I have no fascination with batteries other than their ability to reliably perform the duty I require and so have no pre-conceived favourite.  Weighing up the pros and cons of each and relating them to an off-grid duty without cherry-picking is not as simple as some would have you believe so I would just say that based on £/kWh alone FLA currently still makes more sense by quite some margin. Personally I don't believe in very big batteries of any kind - lots of storage to use is also lots of storage to refill to get back to the point you started from. I do accept that if you have only one generation source like PV and daily cycling it is logical to specify more storage than with less time limited sources - how you decide at which point the law of diminishing returns kicks in depends on how you operate everything. Having said all that, when I have to, I intend to go from 24v to 48v with a corresponding increase in bank capacity - this is not only about increasing storage though, we get by just fine with a relatively small bank.

could I ask another question to those of you with diesel generators - how do you avoid glazing of the cylinders if you only need to top the batteries up?

As Paul and billi have said depends entirely on how your generator is interfaced to your system and how you operate your charging regime and that depends on how you operate your inverter/charger(s) - a crucial item you haven't really asked about. Put very simply our generator is started (either manually or automatically, depending on my mood), generally as Paul has described, when RE generation has been insufficient to complete the battery charge cycle. We then load it up with all the "time shiftable" domestic duties for which there has also been insufficient RE generation (all diversion loads are automatically isolated during a generator run) such that it runs 50-90% of it's capacity during absorption phase and shuts down when back on float. Our inverter/chargers hand power quality control to the generator when running and we have no issues with flickering lights, white goods etc - depends how good your generator is I guess. With the size of my bank the whole charge process is complete in 60-120 mins if automatically started depending on time of year as I change cycle periods to match seasonal temperature and PV potential. I think the principle is generally sound for generator life (but not volume of diesel use!) but how it all operates is specific to my system and the way I choose to run it.

I imagine you have plenty more homework to do if off-grid is the aim.

[Countrypaul]

One aspect that has not been mentioned as far as I can see on this thread is the use of heat from a generator. Several people have successfully utilised the heat from a water cooled generator to contribute to heating the house/garage etc.  One rule of thumb for a water cooled diesel generator is that 1/3 f the energy goes to generation, 1/3 to the coolant and 1/3 out the exhaust - though exhaust heat recovery has also been implemented to change that somewhat.

Depending in the diesel engine it is also possible to run the generator on (waste) vegetable oil - certainly a Lister but probably not a modern CR based one.  Waste veg oil would need settling, filtering and dewatering before use but if you have a free supply - local restaurants etc. it can make a significant impact. Beware that in cold weather (<0C) vegetable oil can wax up easily.

[camillitech]

One aspect that has not been mentioned as far as I can see on this thread is the use of heat from a generator. Several people have successfully utilised the heat from a water cooled generator to contribute to heating the house/garage etc.  One rule of thumb for a water cooled diesel generator is that 1/3 f the energy goes to generation, 1/3 to the coolant and 1/3 out the exhaust - though exhaust heat recovery has also been implemented to change that somewhat.

Personally, I would steer well clear of water cooled generators and CHP. The whole point in RE and being 'off grid' (for me at least) is to run the generator as little as possible. That's not to say it is not worth doing but do you really want to integrate the generator into your heating system thus encouraging you to use it 

Also, air cooled DG's tend to be far more reliable, some 70% of all failures on prime movers are related to the water cooling system. Head gaskets, water pumps, belts, hoses, frozen coolant, etc. You really need to be siting your generator as far from your house as is practical which is not conducive to an efficient plumbing system and extracting heat from the exhaust can lead to blocked exhaust systems. Especially if using alternative fuels.

That's not to say it cannot be made to work if done properly, there are some cracking water cooled generators out there these days. I just prefer the simplicity of using my generator shed as a drying room even if it does make my clothes smell like an oil refinery 

On the face of it CHP is the ideal solution but after years of mulling it over, it's not for me.

Good luck, Paul

[biff]

I agree with Paul,
              Water cooled is just another serious problem to go wrong in the off grid world. I Also like keystart or button.
 I have swung enough old Listers and Petters engines to life that my right arm is 6 inches longer than my left. There should be a law against those starting handles. Sometimes we scattere like rabbits when the handle jammed on the shaft. Horrible carryon at 7.30am. And still half asleep. 2 pulling on the drum 1 swinging the handle and the 4thman, with a lump of cement bag dipped in diesel and burning bright being sucked in the air intake.
Then smoke everywhere,  Blue smoke  White smoke and dirty black smoke we called it revenge.But I cannot remember one of them dying unless they were run out of Diesel. I knew a few Listers in my time.
     Biff

[billi]

well ,  i had my go/thoughts  on CHP ideas too , but then came the sun    (PV down in price and a bigger battery) that resulted  very little generator running hours  in winter  and even further until nil hours  a year

as the priority  was battery charging, with the generator  to keep the .... erhm.... the/my Bank happy fully charged

When battery is full , but one is cold, it seems a waste to start a generator for heating purpose  only









 

[Alan D]

Ref “ I have swung enough old Listers and Petters engines  “

Same here. Push button / Auto start 5 Kw Diesel Genny has never failed.

One of my Dumper trucks has got.
Hydraulic brakes.
Hydraulic steering.
Hydraulic raise / lower / latch on the dumper.

Brilliant design.

Downside. Its got a rotating handle on the back to start it.
The people that design these things should be made to start it from cold a thousand times.

Maybeeeeee then a bit more thought might go into the design.

[oliver90owner]

I quite like my Hatz driven genny.  Auto decompression, cold start and reliable.  The genny is a good ‘un, too.  A good old Stamford rolled steel magnet frame, armature wound -  and IMO, runs rings round stator-wound genny’s with electronic AVRs.  A bit different when it comes to moving it, mind🙂.

I reckon the old slow revving CS and CD/CE engines were probably some of the best Lister diesels - for longevity with fuel economy.  Starting dumper and cement mixers were not my job, I’m glad to say.🙂