Solar system review

[Mike90250]

...I am also looking for a good battery charge indicator.....

Me too! They don't exist.

What do exist are "battery totalizers". They have a shunt, that measures all the current in and out of a battery, and they assume that it need 120% return for power taken out.
They come pretty close, to giving a good acounting of the State of Charge of a bank, but you still periodically have to check each battery, and decide if you need an EQ charge.
Sold as battery meters or whatever snake oil phrase is working that month. The tip-off is it needs a shunt, and look for one that measures both in and out.

[mikejh]

Ok, it sounds like a pure sine is about manditory for me then, although like you said, I will check into it a bit more.

I have heard many diffrent oppinions about how to size the inverter as well. If my draw is say a maximum of 3Kw, then some say I should have a minimum of a 6,000watt inverter. Others say a 4000 would work fine. I think I will end up with a 5000, just so I can expand a bit if I need to, but I am not sure why I would need a 6000watt. Any idea's?

[Mike90250]

.......
I have heard many diffrent oppinions about how to size the inverter as well. If my draw is say a maximum of 3Kw, then some say I should have a minimum of a 6,000watt inverter. Others say a 4000 would work fine. I think I will end up with a 5000, just so I can expand a bit if I need to, but I am not sure why I would need a 6000watt. Any idea's?

Add up the loads you expect to have on at one time. 300 + 200 + 20 + ??????
That gives your baseline. Are any of those loads a motor ? Any large loads expected to come on, while baseline loads are on ? If your inverter cannot handle the starting surge of a fridge, while the lights are on at night, the lights go off ! The inverter will often try to reset it'self and blink the lights a couple more times, while the fridge is also trying to start.
I'm running a farmhouse, with a 1/2 hp well pump, and my inverter is rated for 200% overload for 10 seconds (12 Kw) It's a 6Kw inverter on 48V, so far has been fine running the pumps and the shop tools.

You need to see what the inverter overload specs are. Morningstar has a 300w inverter ,with overload of 600w for 10 min. It generally is not enough to start a fridge though. They are all different.

[Sunking]

There is only one real good battery monitor you can buy, a temperature compensated hydrometer like this one. Once you get a really good lab quality hydrometer you can then exercise your battery and with a good volt meter make a decent SOC graph with this procedure. It is the only way to do it accurately.

[mikejh]

Ok.

Here is what I have as far as wiring my batteries. Is this correct?

Battery bank wiring.jpg

I am assuming that I will connect the charge controller to the same terminals as the inverter, right?

EDIT: these are all 2V batteries in series to make a 12V system.

[mikejh]

Add up the loads you expect to have on at one time. 300 + 200 + 20 + ??????
That gives your baseline. Are any of those loads a motor ? Any large loads expected to come on, while baseline loads are on ? If your inverter cannot handle the starting surge of a fridge, while the lights are on at night, the lights go off ! The inverter will often try to reset it'self and blink the lights a couple more times, while the fridge is also trying to start.
I'm running a farmhouse, with a 1/2 hp well pump, and my inverter is rated for 200% overload for 10 seconds (12 Kw) It's a 6Kw inverter on 48V, so far has been fine running the pumps and the shop tools.

You need to see what the inverter overload specs are. Morningstar has a 300w inverter ,with overload of 600w for 10 min. It generally is not enough to start a fridge though. They are all different.

That is interesting. I was told that I would need at least a 1500watt inverter just to start the compresor for the refrigerator. I guess it probably depends on the unit.

As far as linking my batteries in series, is the diagram I drew up correct?

Also, should I have a in-line fuse in addition to the fuse in the inverter?

[Mike90250]

Ok.

Here is what I have as far as wiring my batteries. Is this correct?

[ATTACH=CONFIG]1232[/ATTACH]

I am assuming that I will connect the charge controller to the same terminals as the inverter, right?

EDIT: these are all 2V batteries in series to make a 12V system.

Yes, this will work for a 12V system. An awfully large 12V system. You need a fuse as close to the + battery terminal as practical, the inverter manual will say what size fuse, and the wires need to be large enough that the fuse melts before the wires melt, in case of an accident.

Inverters vary in their surge capacity, and motors vary on their surge draw. Hard to forcast, some electricatians have a "Peak Read AC Amp meter" you could have them test your fridge, or buy the $200 meter to test it yourself.

[mikejh]

Thank you for confirming the diagram. I will probably just get a large inverter, being that it will allow me to add a few thing if needed. It sounds like a 2000watt (3000watt peak) will work just fine.

Fuses usually say "use with so many watt inverters or less". Should I get a big one, or one that will bairly work? They are usually about 100A per thousand inverter watts. Does that sound about right?

Also, what size wire should I use to link my batteries?

[Mike90250]

for the fuse, use the one suggested in the inverter's manual. Order it from the same place you order the inverter from.

1500W is 125A at 12V
My 300W sure sine can supply huge surges, I belive it recomened a 80 or 100a fuse for it.

This brings up the problem of 12V systems. The amp demand is generally too high for the battteries and wires. Any losses, even half a volt, will bring the inverter close to shutdown. You at least are using huge 2V batteries, which can supply the amps needed. But you still have the copper (ohmic) losses in the wire and inside the inverter to deal with.

A 24V system (use 4v batteries) will only consume half the amps, and needs only to rewire the PV and reset the controller. (unless you have a lot of 12V appliances tou need to run off 12VDC).

[mikejh]

the low input voltage shut down on the AIMs 2000 is 10V. There are more specs listed here:

http://www.theinverterstore.com/the-inverter-store-product.php?model=pwri200012s-top-rgb#

I am not sure I want to spend another $2,300 on batteries to bump it up to a 24V system. How much voltage loss will there be? (if still running 12V)

I just contacted AIMs and they reccomend the 200A fuse, and 1/0 wire for thier 2000watt inverter.

[Mike90250]

I didn't know you had already committed to the batteries

[mikejh]

There sitting in my garage...

[Sunking]

You are operating a 2000 watt inverter at 12 volts? Why? At minimum you want 24 volts and if you ever wanted to go higher wattage 48 volts.

[mikejh]

Its a bit late to find that out How manditory is it to use 24V or higher?

[Sunking]

Its a bit late to find that out How manditory is it to use 24V or higher?

It is not mandatory, just foolish to use low voltage if you do not have too. You will end up burning off a lot of heat in your wiring you can never recover. It also made you installation and material cost a lot higher. In addition you will probable find you inverter tripping off when under heavy load when the voltage sags. In addition you increased your fire risk by 400%.