Just started a large project .. ~2000 watts and building own panels.

[Paul54]

If you have a lot invested in 12 volt appliances you may want to consider splitting up your system. I run a small system for 12 volt lighting and small 12 volt loads, under 200 watt hours total per day.

As has been pointed out, the savings you think you may be getting by not using inverters on a high wattage 12 volt system, could very well be lost in your wiring.

Another consideration is how many parallel battery strings you will end up with for a 2kW system.

[Sunking]

My reasoning is simple. Many appliances operate off 12v. If I can maintain a 12v system that would be that many watts that do not have to go through an inverter.

One minor problem you have overlooked. Power loss in the wiring at 12 volts is extraordinary. From panels to utilization devices I bet you are loosing 30 to 50% of you power lost as heat on the wring. Use higher voltages, MPPT charge controller, a good inverter and you cut your losses to 10% or less. Saves a lot of money on panels and wiring.

[TTG]

I could explain but it is pointless to have that large of a 12 volt system. Once you get above 500 watts solar panel wattage you enter 24 and 48 volt battery territory.

My reasoning is simple. Many appliances operate off 12v. If I can maintain a 12v system that would be that many watts that do not have to go through an inverter. Since, the inverter takes a percentage of the wattage, it makes since to bypass it. And, I plan on turning the inverter off at times to maintain or increase charge. So, I have and plan two systems one 12v and the other 110v. Also, small voltages tend not to jump. Yet, not much wattage can go through the 12v system because it requires very very heavy wire at higher wattages. So, my max is going to be 100 watts 12v. This can power lights, tv, internet, computer. That requires explanation. Lights that are LED and mainly used for browsing a room. A 7" TV that is in the range of 15 watts. And, a small laptop. Thanks for the reply.

[TTG]

You are building a 2000 W array ? @ 15V, thats 133 amps. I suspect that you could do it with 2, 80A chargers. Outback, http://www.solar-electric.com/oufl80sochco.html but they are actually $600, don't know why someone thought $400, maybe they are better shoppers than I.

Wire 1,000 w of panels to each controller, and then the charger output goes to the battery. Repeat. OMG What a nightmare that battery bank will be.

Check out this article about battery wiring on the www.smartgauge.co.uk/batt_con.html

On the "wiring", I'm using #2 method. That was very helpful. Thank you.

I have not built the final panels. But, an estimate on what I have and will be able to produce has a "listed" output of aroung 2196 watts. So, two probably wouldn't do it. Would PWM charge controllers be adequate ? Is the bank wired as one bank or two ? Thanks.

[Sunking]

That's a very good price on MPPT's. Still, with that price it would be $1200 if I could wire them to the bank in that manner. And yet still, I might do that. Can you expand on how you would wire 3 MPPT's to a bank that goes to one inverter? Sorry, if this sounds a little stupid.

I could explain but it is pointless to have that large of a 12 volt system. Once you get above 500 watts solar panel wattage you enter 24 and 48 volt battery territory.

[Mike90250]

That's a very good price on MPPT's. Still, with that price it would be $1200 if I could wire them to the bank in that manner. And yet still, I might do that. Can you expand on how you would wire 3 MPPT's to a bank that goes to one inverter? Sorry, if this sounds a little stupid.

You are building a 2000 W array ? @ 15V, thats 133 amps. I suspect that you could do it with 2, 80A chargers. Outback, http://www.solar-electric.com/oufl80sochco.html but they are actually $600, don't know why someone thought $400, maybe they are better shoppers than I.

Wire 1,000 w of panels to each controller, and then the charger output goes to the battery. Repeat. OMG What a nightmare that battery bank will be.

Check out this article about battery wiring on the diagonal

[TTG]

Well for one thing MPPT controllers do not cost $1500. The largest top of the line 80 amp MPPT controllers sell for around $400. Where you are fooling yourself using a diversion dump load controller made for wind turbines is robbing you of 50% of power production, and significantly shortening your battery life cycle count. What you are doing is going to cost you a lot more in the long term by having to use more panels than is necessary and frequent battery replacement.

That's a very good price on MPPT's. Still, with that price it would be $1200 if I could wire them to the bank in that manner. And yet still, I might do that. Can you expand on how you would wire 3 MPPT's to a bank that goes to one inverter? Sorry, if this sounds a little stupid.

[Sunking]

That said, it would be nice to spend $1500 on MPPT chargers and the like. I don't got that to spend.

Well for one thing MPPT controllers do not cost $1500. The largest top of the line 80 amp MPPT controllers sell for around $400. Where you are fooling yourself using a diversion dump load controller made for wind turbines is robbing you of 50% of power production, and significantly shortening your battery life cycle count. What you are doing is going to cost you a lot more in the long term by having to use more panels than is necessary and frequent battery replacement.

[TTG]

there is problem for your storage battery group, golf cart battery is not good for storage
and also use 12V or 24v battery system for storage,

Golf cart is the best I can do on budget.

[TTG]

This http://www.solar-electric.com/c40.html is a REAL C40. the coleman air is a rip-off of the 20 year old name. it is a DIVERSION/DUMP controller designed for Wind systems. It will take it about 2 years to destroy your batteries that should last 8 years.

The Xantrex/Trace c-40 is a real, 3 stage solar charge controller, that is also flexible enough to be a diversion controller for wind/hydro. But it's can't be both.

Batteries need a 3 stage charge , Bulk, Absorb, Float. Occasionally, they need an Equalize cycle, which the C40 does also.

You need to have at least 18-19V available (under load, not open circuit) to feed the charge controller, so it can properly manage the battery charging.

You cannot use the 8V batteries in any combination with a 12V system. ( well, you can, but something will fail )

I've read that the absorb, float, and equalize are nice things to have but not necessary. The charger is for solar, wind, hydro, or a combination of these.

http://colemanair.us/ebay/Images/C40_HookupDrawingDualWindSolar.gif

That said, it would be nice to spend $1500 on MPPT chargers and the like. I don't got that to spend. Possibly in the future. I can pick up another one of these and wire them in series so that if one stops working the other can pick up the load. If you can find a way to control the charge at 2200 watts and 12v (Yes, if I don't go 14v, I'll go 12v) for under $800 I'd very seriously consider doing that.

[ericzc]

battery issue

And, thus the reason I'm here. Although, parts of the system have been functioning for awhile... I'd still rather avoid the smoke/fire if at all possible. What seems to be the worst problem(s)??

The batteries are now at 14v (8+6), the panels put out ~17.8 volts(200 watts). I've never had it keep a charge above 15v. I get a quick curve upward after about 14.8 volts. This seems to me to be the limit. Thank you. I am underutilizing my capability at this time. As, it is not enough to power large appliances. Am I wrong?
The rheostat (DC dimmer) is for less than 100 watts total and haven't used it yet. Up until the time I use it, when my supply goes over about 14.7v I jump to a transformer off the inverter supply. But, I want the ability to not use the inverter when my supply is low. The 200 amp charge controller is being utilized without problems. Using an 800 watt inverter that can handle the <15 volts it gets. Aldready have a 2500 watt with the same voltage specifications. Don't need it yet.

The 12v rheostat is for appliances that won't use the inverter. As, I'd like to turn it off at times in order to conserve power.

I'm on the darkside of the day now. A little bit of sun is out. My controller has stopped clicking on and off. Checked my voltage and it's at 14.7. My charge controller is a Coleman Air that uses a 200 amp relay. So, a direct connection/or not. Does that help.

there is problem for your storage battery group, golf cart battery is not good for storage
and also use 12V or 24v battery system for storage,

[Mike90250]

This http://www.solar-electric.com/c40.html is a REAL C40. the coleman air is a rip-off of the 20 year old name. it is a DIVERSION/DUMP controller designed for Wind systems. It will take it about 2 years to destroy your batteries that should last 8 years.

The Xantrex/Trace c-40 is a real, 3 stage solar charge controller, that is also flexible enough to be a diversion controller for wind/hydro. But it's can't be both.

Batteries need a 3 stage charge , Bulk, Absorb, Float. Occasionally, they need an Equalize cycle, which the C40 does also.

You need to have at least 18-19V available (under load, not open circuit) to feed the charge controller, so it can properly manage the battery charging.

You cannot use the 8V batteries in any combination with a 12V system. ( well, you can, but something will fail )

I have a concern that you are building a very large homebrew system and don't even know the right questions to ask about it

[TTG]

I'm sorry I do have a tendency to give too much information in a slightly disorganized fashion. (ie Sunking - thinking the C40 isn't a charge controller and Mike - thinking the rheostat was integral to the overall system) It really is not your fault. It is mine. I do appreciate you both for spending the time to read and reply. And, value your insights tremendously. Please continue, I realize misunderstandings are more than likely my fault. Thank you.

[TTG]

You do understand neither of the Coleman devices are charge controllers right? They are Diversion Dump Load Controolers

As I understand it, the C40 is a charge controller. It measures the voltage and if it's "too high" it switches off. And, when it reaches a "low" it turns back on. It does not change the voltage in order to "top off" the battery. It does not protect the battery from over discharge. Although, one could.
(And, it is being considered to use one for that purpose. But, it would require the "power to" the main relay to be reversed by a relay in order to maintain "mostly unpowered" status. And, since this small reversing relay would be always on it would have to be robust. Any other ideas about a really cheap system disconnect for low voltage at 14v 200 amps?)
The "diversion load controller" aspect is for wind power in order to protect the windmill turbine. In solar applications a diversion load is unnecessary. Is that what you mean? And, thanks for the reply.

http://colemanair.us/ebay/Images/C40_HookupDrawingDisconnect.gif

[Sunking]

Coleman Air C40 controller w/200 amp relay

https://www.colemanair.us/vp_asp/scripts/shopexd.asp?bc=no&ccode=C40-12SG

They have a 440 amp relay

https://www.colemanair.us/vp_asp/scripts/shopexd.asp?bc=no&ccode=SEA440

I bought my relay through a retailer of their product.

You do understand neither of the Coleman devices are charge controllers right? They are Diversion Dump Load Controllers