how do i work out solar

[m1cdq]

how do i work out the wattage i need from solar panels to charge my battery banks

I 3 banks  made up of batteries in 3 rows each row is of different AH

each row is about 200ah  

If a total of 600ah up to now at 12vdc

im in the uk

the idea is to use one bank, charge another and have the 3rd in reserve

and poss in future  add more banks as i get more batteries

at moment  batteries are being kept charged from the grin on float charge

the 3 banks are paralleled  up for float charge at moment

my idea is

solar panels..................................    bank1            

Generator.....................................    bank2   ......... load  

Grid to  powersupply 12v dc 25 amp...   bank3

poss windturbine in future.............      poss

                                                     bank 4

                                                     bank 5

any suggestions on charge controllers

the reason for 12 volts is my radio shack  

just out curiosity   the guys who live totally of grid  what the AH size of your banks

whos has the biggest AH    LOL

[boB]

Roughly,  600 Amp-hours at C/10 charge rate is 60 Amps of charge current.

(you 'could' use less current, but that's a good number, generally)

It's a fairly typical battery size for a 12V system pretty much.  I've seen

much bigger (way too big IMHO).  It really all depends on your energy needs, but

most people make do with what they can afford and what they have at the moment.

At 12 Volts, this is  60Amps X 12Volts = 720 Watts of PV  (STC, or nameplate rating)

Actual output is normally somewhat less than this (~20% less)

You'll most likely want an MPPT controller for this one.

OutBack MX60, Apollo T80, Xantrex XW60, MidNite Classic (coming soon I hope),

and maybe some others out there...

boB

[Volvo farmer]

I've got about 800Ahr on two strings of L16s at 24V, one bank.

I'm running my entire household off of it and can't remember the last time I saw the Trimetric at -100Ahrs. I reckon I bought more battery than I need but I don't see a real down-side to it yet. It won't be long before the old Servel gets it's valve shut off and I'll need that capacity for an electric fridge.

Some more information would be helpful. What are the requirements of your system? Do you have any idea of how many watt/hours or amp/hours you plan on drawing from this system on a daily basis? If that number is close to zero, your solar requirements will be much less than if actually plan on using a lot of power every day.

Your three bank idea is a novel one. Do you have to go out and physically switch from one bank to another when they get depleted? Is your goal to be totally off grid? or just power a radio shack? For off-grid persons, most usually don't like the idea of constantly switching between multiple banks every time the voltage gets low. Most systems I've seen charge one bank to lessen the hassle and babysit factor.

[boB]

I suggest to use only one battery bank instead of what you have listed.  People

do this but I'm not sure why.

I think it will be too hard to divide the energy sources up the way you've

got it listed here.  Why not use all your sources to keep one bank in good shape?

Also, any one battery will have a shallower depth of discharge this way

and the overall charging source issue will be much less confusing.  Use

the generator when the sun ain't blowing and wind ain't shining.

boB

[m1cdq]

Thanks for the replies

on further reading it looks like i my string them all together to form one bank

my main aims  and im starting from scratch and some back ground

Im in the UK  and on the grid

so in the short term going out and spending loads of cash to go off grid  it would be long time before i saw any money savings if any at all.So im trying to reduce my draw from the grid.

I have so far replace all bulbs to low energy

shut down what i dont need ie TV not on standby ect

Im hoping to borrow a watt hour meter next week to do an accurate check on what my radio shack uses as its got a fair bit of kit in it sever pcs  router  printers ect

aim number one...To  make the radio shack off grid.this includes radios pcs  and network.

aim number two  to try and convert all lighting in house to 12v led lights.If I can do this then all i would need to do is disconnect the lighting circuit from mains and resupply it with 12v DC

As a radio ham ive deep pocket and short arms  so i dont like to spend money unless I have to. so i like to do things as cheap as poss or if its free even better LOL

looking at my site  solar seems the better choice as we do get wind  but not enough

so long term while i build up panels i will use grid to keep batteries topped up

but intend hopefully to mainly use solar with a little wind. and use grid as little as poss  

I hope this all makes sense

 

[Bruce S]

m1cdq;

   It seems as if you have thought this out very well. Since changing the lights out to low energy, I'll assume you're talking about CFLs, I was wondering if you've had freq. noise problems across the bands you're on?

The 12Vdc LEDs make very good sense in the realm of not creating noise,  the Newer MR16 LEDs bulbs look like they would be a good fit for your needs and the prices are dropping very nicely.

There's an older thread over in lights that deal with making use of old MR16 bulb caseings and retrofitting them with Lux LEDs or multiples of white LEDs.

Cheers

Bruce S

[DamonHD]

Hi,

Maybe take a quick look at my PV pilot taking first my office lighting off-grid (going for nearly 3 months now, but winter will be the real test, and I know that it won't have enough juice) and then my main servers moved onto a low-power laptop requiring 10 times the capacity.

http://www.earth.org.uk/solar-PV-pilot-summer-2007.html

http://www.earth.org.uk/saving-electricity.html

You won't be saving money compared to UK grid prices.

Remember that your first task has to be to eliminate wastage.  That's a good thing to do anyway, wether you go PV or stay on-grid.

Rgds

Damon

[m1cdq]

Bruce  no ive not noticed any increase in band noise across any of the bands

160m- 23cms

the CFL im using are by GE lighting

www.Gelighting.com

most of them are the 20 watts

Id like to find some led light fittings that ar Gu10 fitting and BC  fitting

[Bruce S]

m1cdq;

  Good to hear the GE's are holding down on the noise. There's a hammer close to the house who I believe is in the meter band ( I haven't touched one since '72 and even then wasn't sure of what I was doing  :-))

However the neighbor was telling us of the problems he ahs with the new CFLs throwing off noise and stuff.

For the BC fitting, try going to the truck repair centers. Here , a lot of the petrol stops have replaceable bulbs that are built for the drivers to be able to replace them and they are of this type. Also, a lot of Automotive aftermarket places are carrying them as well. They love the pretty blues ones:-)

Ghurd, and a couple guru types can help with the design if you want to do a DIY thing. I constantly pick his brain to make sure I don't try to cook the house :-D

Cheers

Bruce S

[bob g]

the main reason i can think of for having a divided battery bank is if you have

dissimilar battery types, sizes or ages

for instance if you have bank

A: new and large deepcycle flooded cells

B: nickle cadmium

C: old and small deep cycle flooded cells

each of which have differing charge concerns, or

A. new large deep cycle batteries

B. 3 year old batteries of the same type as above

C. and old set of deep cycle batteries

each of which while being virtually the same in size and type, still have

signigicantly different charging concerns

now if all are the same type and size and relative age,, then i would

suggest putting them all in one bank,,, but only if all of these criteria are true

not 2 out of 3, but all three.

bob g

[peter nap]

There is another reason for breaking up banks although in my case, they are very small banks. That's to have dedicated power supplies for items that are just too far from the main bank to be worth the trouble.

For instance, I use mine on weekends only so the power is shut off to the main house during the week. This allows full charging of a too big battery bank on too little solar and wind.

I have a composting toilet that really needs the vent fan to run all the time I have a very small dedicated panel and battery just for it.

I also have a few lights that have their own panels and several security cameras on dedicated systems.

If I was there full time, I would probably tie it all into one.