Designing new 12VDC Off Grid system. Many questions. (Midnite 150)

[vk4akp]

OK. HI guys again!.

Your going to hate me because I am still thinking 12VDC for our initial system but with NiFe batteries.

There are a lot of reasons for this choice. But I do realise that if money was no object that 48VDC would be the go 4sure!

So.. My next question.

If we go with a 12VDC battery system, I totally understand the variable voltage range problem. As specially with regards to NiFe.

So what's available product wise or even just circuit / educational wise with regards to a DC to DC converter @ 12VDC?

Something that would handle the range of 10 - 16VDC input and smooth it to a nice 13.8VDC output? Lotz a amps!

TNX
.-.-.

[zoneblue]

So what's available product wise or even just circuit / educational wise with regards to a DC to DC converter @ 12VDC?

Something that would handle the range of 10 - 16VDC input and smooth it to a nice 13.8VDC output? Lotz a amps!

This is not really easy, because you have buck converters and boost converters, and they both need a bit of leg room. The kind of converter that can handle the situation  where the input and output are close is a auto buck/boost. ie it can operate in either mode. They are less common, more expensive and less efficent. Is that what you wanted to hear?

[Westbranch]

What device is it that needs 13.8V? 

[SgtPepper]

Have you considered a 12v DC laptop powerpack? The one I have you use a coloured plug to change the DC output voltage.

[vk4akp]

OK Thanks, Can you point me to some supplier links for these buck / boost devices please?
(Actually.. Edit: I just found a few on eBay. 97% efficient so not so bad. Largest is 150Watt though. Would need 300 Watt).

Eventually I will go to a higher voltage.
But for now it's going to be a 12VDC system because.

- Less batteries needed to set up and cost will be an issue due to going NiFe.
- Top up generators are easier to get with a 12VDC charge port as opposed to 24 or 48VDC.
- Will be adding a DragonFly wind turbine. But it is auto sensing 12/24VDC.
- Also looking into making a gasifacation unit to produce synth gas to run the top up generator. So cheaper generators are the go as I expect the gas to be a bit dirty and most likely run the generators out early.

Because the Midnite is so flexible and same with NiFe I can simply add more cells later on to the project to eventually go 24VDC.

.-.-.

So what's available product wise or even just circuit / educational wise with regards to a DC to DC converter @ 12VDC?

Something that would handle the range of 10 - 16VDC input and smooth it to a nice 13.8VDC output? Lotz a amps!

This is not really easy, because you have buck converters and boost converters, and they both need a bit of leg room. The kind of converter that can handle the situation  where the input and output are close is a auto buck/boost. ie it can operate in either mode. They are less common, more expensive and less efficent. Is that what you wanted to hear?

[zoneblue]

For more amps you just parallel them. Make a cursory check of the voltage on each to make sure they are pretty close. Works fine.

[Cniemand]

I've read through this post and am curious why you are choosing NiFe Chemistry as opposed to the typical Lead or even the LiFePO4 that I have been using in my system?

[vk4akp]

Hi Cniemand, Well I've actually ended up with some second hand ex government Panasonic lead acid batteries to start out with.
I'll use these until they fail and then I'll move across to the NiFe (Edison Cells).

My main reason's are...
- longevity (Life of the batteries) often these types of cells can be passed down through the generations and still be functional.
- Virtually indestructible. You can even boil these things dry and still not kill them.
- Non acidic. Nothing worse then dealing with acid environments. Acid tends to creep into everything around it.
- Stacking. Unlike lead acid etc. You can add extra capacity by paralleling batteries to older pre existing banks without harm.

You'll find this good reading on the subject.
http://www.nickel-iron-battery.com/

And some good product literature from one of the major manufactures here.
http://www.changhongbatteries.com/down/index/51c6482e4c9c74edf078767c5cf80eaf.pdf

At the moment I'm sad to say that the project has actually stalled.
Currently I still need to source some good DC switches for isolating the main array, batteries, & load. Also chasing a source for wire.

Hopefully we will see this project kick started again before the end of this year.

.-.-.

[Cniemand]

Thanks! Was curious.

- Cloud

[tecnodave]

vk4akp,

I have been using SAMLEX brand DC to DC converters for some time now and am very pleased with their performance, my base solar system is 24 volts and most of my loads are 12 volt DC. I use a SAMLEX SDC-30 (about $130 USD) which provides 30 amps at 12.6 volts DC very clean, ripple <50 mv. From 20-32 volts DC from my L-16 battries. I am a communications buff but not a ham radio operator so I have researched which one is lowest EMI-RFI. These are widely used in the communications industry to power land mobile two radio gear in construction vehicles.  I also have some lower quality units that power the 12 volt heater elements in my absorbsion refrigeration from my excess p.v. Power made by Pyle ($37 USD) that are much cheaper but much  more EMI/RFI.

Samlex also makes same voltage isolated converters that are buck/boost and I  have a IDC-360A-12 that is 9-18 volts DC in and 12.6 volts DC out.  30 amps .   Very good regulation but that one was $360 USD

I also have gotten many years out of my XANTREX ProSine inverters. My main solar inverter is the 1800 watt 24 volt to 120 v.a.c. Unit and my service truck has the 12 volt 1000 watt and 1800 watt ProSine units,  never had a problem with them but the Exceltech is preferred in professional communications because their sine wave is one of the best there is. If I had to replace a pro-sine I would get the Exceltech due to their quality and awesome service department.

Hope this info helps, cheers from the left coast,

tecnodave

Edit......SAMLEX makes DC to DC converters up to 60 amps output.....
        ..SAMLEX America in B.C. Canada

[vk4akp]

Thanks for the info TechnoDave!

OK So it's time to go eBay shopping again and try and get some of these panels up on the roof finally.
I'm looking at cables and disconnect breakers today.

System
6x 250Watt Panels in parallel. <<- (Sorry. edit. I'm tired) LOL! Not series. Parallel
Classic 150
2x Panasonic LC-XA12100P (12V, 100Ah/20HR) [In parallel (12VDC)]> Good quality made in China ok Joe!
Rated PV Array current is 47.22 AMPS
Max Current at 14.4 (Battery) 104.2 AMPS
Max VOC 44.4 VDC

6mm cable is harder to find.
I've found a supplier selling 4mm thick x 450mm long with MC4's for about $4 each. (Suitable?)

With the MC4 branch joiners are the plastic "T" type as good as the wire "Y" type?

Now for the Panel string circuit breaker I have found these
(50 Amp, 500 VDC Din rail mountable, Noark)
http://www.ebay.com.au/itm/50A-DC-Breaker-Solar-Isolator-50-Amp-500V-Circuit-Breaker-dual-pole-2-pole-/261247129685

For the battery I haven't found anything yet.
I would prefer din rail. But might mount something closer to the terminals like this.
(200 Amp)
Specifications:
Max. voltage: 42V dc
Interrupt rating: 3000A @ 30V dc
Operating temperature: -32°C to 82°C
Material: UL94V-0
External dimensions: 70 x 50 x 35mm
http://www.ebay.com.au/itm/200A-DC-Circuit-Breaker-high-current-Isolator-200-Amp-surface-mount-single-pole-/390591666445

Comments please?
.-.-.

[Vic]

Hi Ken,

A quick post -- a storm is due in a few hours ...


First,  you do not want to connect all of the PV modules in series (as I read the above post).   This will probably exceed Max Vin spec for the Classic 150.  Most PVs in this power range have a Vmp of about 30 - 31 V,  and a Voc of around 38 V or so.   You could run two strings of three in series,  and not need a Combiner with fuses/breakers.   This 90-ish (I assume) string Vmp is a bit high for a 12 V system.   The Classic would be a bit more efficient with three strings of two,  with a Combiner and DC rated breakers for each string.

The first link is for a Ganged Dual breaker,  probably not what you need.  MidNite (and Outback power for that matter)  sells a line of DIN breakers specifically made for Solar applications,  try to find these locally.

Also,  try to stay away from the surface mount breaker in your second link.  These are Thermal breakers,  and do not really have enough current Interruption ratings for battery connection -- YES some folks do use them,  but,  there is a lot riding on the ability of this breaker to break Fault currents if something shorts ...  a fire could result.

Here are some of the MidNite Breakers,  this one is used commonly for PV strings:
http://www.solar-electric.com/mnepv.html

They make breakers for the CC to battery -- this one is a DIN Double Wide:
http://www.solar-electric.com/misomn150vdc.html

These breakers are nice for PV main breakers (although the DINs are fine for this) and for CC to battery:
http://www.solar-electric.com/pamodccibr.html

Realize that you are down under,  and it is difficult to buy internationally,  but these links are an example of the Real Deal breakers that are rated for the task of Solar use.

All of the above breakers are rated for Continuous use at rated current without tripping.   Your rated PV power might possibly  on rare occasions exceed 100 A,  but this is unlikely.   To meet the Codes in the US,  the breaker on the CC output would need to be up-sized to 125% of the rated current.   I am not a Code expert.   On your system,  you will need to use a large diameter cable between the CC,  breaker and battery.

More later,  73  GL,   Vic

[vk4akp]

Back again.

Still plugging away collecting bits for the install here.
Got some roofing screws donated for holding the rail brackets to the roof so that's a few $$'s saved.

Still need to find a affordable source for DC breakers. 100Amp ones are close to impossible to find here
(Edit: Thanks for the DC breaker links. Looking into it now. )
And some cable. Maybe just eBay for that.

Anyhow reason for my post is I've bought a new toy to add to the mix.

eBay kept sending me discount vouchers and I found a discounted Wind turbine with make an offer on it as well.
All up with all the discounts I ended up getting a 400Watt turbine with controller for AU$305 including shipping.

Pictures here: http://shazam.zapto.org/igal/wind-turbine-1/

So here comes the questions.

It didn't come with a dump resistor. I am wondering what can be used there? I'm also wondering about using a water heating element to dump unneeded power into the hot water system as free heating. ? Trouble with this idea is there would have to be a thermostat to disconnect the element at a set temperature. At which point it no longer works as a dump load resistor?

To totally stall the blades, do I just short the dump load resistor lines? Or is that a no no.

Yes you've probably guessed the Chinese instruction manual is close to useless. And I am new to wind turbines. LOL!

The controller is quiet strange. It is a hybrid thing. Allows for a solar panel up to 300 Watts + a wind turbine up to 400 Watts.
It also supposedly senses if it's a 12 or 24VDC battery. ¿¿¿ 
Anyone seen these before? Comments??

If I use my Midnite Classic for the 1.5KWatt grid panels and the new wind turbine controller on the same battery, how will that effect things?

Which is more bird friendly. White or Black blades?







.-.-.

[dgd]

Are you sure that hybrid controller does not have a dump load built in?  That's a lot of heat sinking fins surrounding it AND it appears there is an led to indicate BRAKE which sort of implies a load resistor or maybe a shorting relay being used to slow or halt the turbine.
I would tend to not consider water heating with this as real power output in anything less than a major storm is likely too insignificant to be useful.

Dgd

[vk4akp]

OK, I've had a bit of a chance to catch up with the reading.

Vic - Those DC breakers look good. And the price is about a third compared to the last time I looked so good one thanks!
I as specially like the ones from the first two links.
Midnite Solar MNEPV 150 VDC 80A and 100A Solar Array Breakers - Will use this for he array breaker (As suggested).
The wiring confuses me though. Looks like both switches are combined to try and share the load or something?
Shouldn't solar panels be totally isolated when switched out?
MNEPV Midnite Solar MNEPV 1 to 63 Amp 150 VDC Breakers for Solar Panel Arrays - And will use some of these for the DC fuse box to break out to different DC outlets in the different rooms.
I notice that you reference http://www.solar-electric.com as the supplier. I have been dealing with http://www.altestore.com previously. Any preferences which might be the better one to go with?

I've also decided to run all the panels in parallel. Cable combiners have become a lot cheaper over time and I prefer to work with lower voltages so I'll be doing it that way which is better anyhow.
I might also only start out with 4x panels (1KWatt) for starters as I'm tempted to play around with the other two using Aurora Micro grid tie inverters at another location for a bit.

dgd - I just assumed by the picture of the bulb on the controller that the Yellow Wires go to a dump load resistor?
I'll try emailing the supplier again but their English and listening ability is fairly poor.
As for the lights on the thing. Yes it's like a Christmas tree. LOL. And there is even an IR LED on the thing marked Infrared Communicator. The documentation says nothing about this. Nor is there a remote.

I also have to try and find out some math on what wire I can use that will handle the currents etc.

OK More later. It's almost 4AM here. Burning the Midnight Oil. LOL

TNX 4V advice! Much appreciated.
.-.-.