I have (x3) 150W panels, and need 1600Wh a day. Suggestions for battery banks?

[Fractalcathedral]

Thanks, that's all enourmously helpful. I will note the precaution, but what are the reasons for avoiding parallel batteries? Are they based in safety or efficiency, or both?

And wouldn't the disadvantages of 12v vs. 24v, (i.e., 12v systems requiring larger cords due to increased amperage, and the increased danger associated with higher amperage when the freezer kicks on and draws power from the a lower voltage inverter) make 2,4,and 6v batteries even worse choices?

[Sunking]

Thanks, that's all enourmously helpful. I will note the precaution, but what are the reasons for avoiding parallel batteries? Are they based in safety or efficiency, or both?

Neither. It is about balancing equally between the parallel strings. You cannot balance them because each string has different internal resistance. That forces the strongest string to do most of the work which quickly weakens it, and shortens th ecycle life of every string. That of it as the Fast Lane to Death. LFP can be done, but they use a Ladder Method.

And wouldn't the disadvantages of 12v vs. 24v, (i.e., 12v systems requiring larger cords due to increased amperage, and the increased danger associated with higher amperage when the freezer kicks on and draws power from the a lower voltage inverter) make 2,4,and 6v batteries even worse choices?

You are talking two different animals which have nothing to do with each other.

You are correct higher voltage (24 )means half the current and wire losses of lower voltage (12), but that has nothing to do with what voltage batteries you use. If you use 6 volt batteries, you use two in series to make 12 volts, four in series to make 24 volts, or eight in series to make 48 volts.

[Fractalcathedral]

You are talking two different animals which have nothing to do with each other.

You are correct higher voltage (24 )means half the current and wire losses of lower voltage (12), but that has nothing to do with what voltage batteries you use. If you use 6 volt batteries, you use two in series to make 12 volts, four in series to make 24 volts, or eight in series to make 48 volts.

Well, I was proposing x3 12v batteries in series, producing a 36v battery in effect, and then adding a parallel string. So I'm unsure why that counts as being stuck in a 12v box. What about having x4 12v in series, producing a 48v bank? Would that be chargeable by a 48v-series module? I know the "vmp being too close to the batteries voltage will make fully charge an issue". But the vmp is still 22, even though the string of panels will be operating at 48v, presumably. (x4) 6v in series would seem to be preferable, but could it be done without too terrible of consequences if options were limited?

The charging of the batteries via engine running hadn't been a consideration until now, but I am eager to research it (via the alternator, I presume?). I'd like to have both options though, rather than either/or. It's a 2004 Ford E-450 with a Triton V10, so it's gas mileage is pretty terrible, but I got a good deal on it and it's pretty reliable from having been well maintained during its run as a shuttle bus. I'd like to be able to just hunker down in it for a couple days at a time without having to move it.

Quick math: Bus gets 8mpg. If I drove it on the highway for one hour a day at 60mph, it would take 7.5 gallons of gas, @ 2.50 a gallon = $18.75 in gas. How long would it take for a full charge? 30 Minutes is still $9.37. 10 Minutes is still $3.123. Again: the option would be great, but as a standalone source it seems less than ideal. But if it's going to be running anyways, (or I have a string of cloudy days) it sounds great.

[Sunking]

Well, I was proposing x3 12v batteries in series, producing a 36v battery in effect, and then adding a parallel string. So I'm unsure why that counts as being stuck in a 12v box.

That is a 12 volt box because you used 12 volt batteries to build your box. Don't get me wrong, 12 volt batteries can work providing they have the required Amp Hour capacity but there is a limit. Largest 12 volt battery capacity you can buy is around 200 AH. At 200 watt hours would be difficult to work with weighing 175 or pounds. A 12 volt 500 AH battery would weigh in at 300+m pounds. That is where you got caught stuck inside a 12 volt box, and used parallel strings. You never considered using 4 or 6 volt batteries of 450 to 500 AH because all you knew is 12 volts batteries.

What about having x4 12v in series, producing a 48v bank? Would that be chargeable by a 48v-series module? I know the "vmp being too close to the batteries voltage will make fully charge an issue". But the vmp is still 22, even though the string of panels will be operating at 48v, presumably. (x4) 6v in series would seem to be preferable, but could it be done without too terrible of consequences if options were limited?

For every 12 volt of battery requires roughly 18 volts. So at 48 volt battery minimum panel voltage is around 70 volts. Good charge controllers have a Voc input of 150 and 600 volts. You want to run panel voltage as high as possible. Yes you can run a panel voltage of 500 volts on a 12 volt battery

The charging of the batteries via engine running hadn't been a consideration until now, but I am eager to research it (via the alternator, I presume?). I'd like to have both options though, rather than either/or. It's a 2004 Ford E-450 with a Triton V10, so it's gas mileage is pretty terrible, but I got a good deal on it and it's pretty reliable from having been well maintained during its run as a shuttle bus. I'd like to be able to just hunker down in it for a couple days at a time without having to move it.

Who said anything about driving and wasting fuel? Certainly not me. That is a diesel engine right? Diesel engines at idle sip fuel. Granted it is over kill.

But here is the reality, any full time off-grid battery system requires a generator. That gives you two options. Use the Engine alternator, or buy a portable generator and battery charge. Take your pick. If it were me I would do both, but that is just me.

[Fractalcathedral]

Thanks for answering all my questions man, I really appreciate it. Just so you know, I copied and pasted the entirety of that thread you posted regarding 2kw 12v inverters to the Amazon review page for that Microsolar Inverter I bought/returned along with a 1-star rating. They reviewed the post, let it pass, but added "You had better know what you are doing or have professional training-" as the byline to cover everyone's asses. Haha.

[Sunking]

They reviewed the post, let it pass, but added "You had better know what you are doing or have professional training-" as the byline to cover everyone's asses. Haha.

If someone knew what they were doing or a pro would never buy it.

[Mike90250]

Who said anything about driving and wasting fuel? Certainly not me. That is a diesel engine right? Diesel engines at idle sip fuel. Granted it is over kill.

Vehicle engine at idle, the alternator puts out minimal power, you have to increase engine RPM's to get the alternator up to full speed to get charging power. 3,000 watts takes about 6 hp to spin, so you are still not burning much fuel. Time to recharge depends on the size of both the alternator and battery size. An average 100A alternator can continually produce about 70A without overheating, so that's about 1,190watts at 17v charging voltage.

[Fractalcathedral]

I am thinking about buying the Midnite Classic 150 for Charge Controller and was looking at the Samlex PST 600W 24v Pure Sine Wave for Inverter. It's UL Listed, apparently, and only $221. It does not, as far as I see, have a built in AC breaker. Does anyone know of any UL Listed 24v, 600w inverters that do? Or should those components be kept separate?

Features of Samlex PST 600W: built-in electronic GFCI, overload protection, low battery alarm / shut down, low idle power draw of less than 0.5 Amps.

[LETitROLL]

Features of Samlex PST 600W: built-in electronic GFCI, overload protection,

I believe the overload protection they speak of is for the AC side and would serve acceptably as your ac breaker? Plus the listed GFCI protection.

[Sunking]

I am thinking about buying the Midnite Classic 150 for Charge Controller and was looking at the Samlex PST 600W 24v Pure Sine Wave for Inverter. It's UL Listed, apparently, and only $221. It does not, as far as I see, have a built in AC breaker.

It is a mobile Inverter and like any mobile Inverter does not need any AC protection. It does not generate enough power to operate a breaker. 600 watts dead bolt fault only generates a whopping 5 amps of current. A 14 AWG plug cord can handle 15 amps of current all day long and never break a sweat.

5 amps will kill you dead in a second, but breakers are not there to protect you, they are there to protect the wiring only from catching fire. What does protect you and the Inverter uses is a GFCI NEMA 5-15 socket to plug in your cords. Before you ask your next question NO GROUND REQUIRED so don't ask.

What you do need is a DC fuses, 4 of them installed directly onto the battery term post. Two fuses facing the CC, and the other two facing the Inverter. You need two Blue Seas 2151 Battery Fuse Blocks, and four MRB Fuses.

BLU_Terminal_Fuse_Blocks.gif

Click on pictures to enlarge for connection detail.

DualBatteryFuse_zps19afcf46.jpg

[Fractalcathedral]

I called Midnite Solar today to ask a couple questions about the Midnite Classic 150, and the woman I talked to referred me to this http://www.midnitesolar.com/pdfs/MNE...150-120VAC.pdf

After having studied it, and read Sunking's last post, I put together this wiring diagram. Wiring Diagram 2.0.JPG

She tried pretty hard to sell me on that Whizbang Jr. thing, so I threw that in there. (Although it's an axiom of mine to remain skeptical about any claim of safety or usefulness, least not from the person whose trying to sell you the thing in question.)

$60 for an accurate reading on battery charge was the jist of it, from what I understand (hence requiring a shunt instead of one of those Blueseas Busbars?)

I am confused though, because I read that
"If your system has a shunt, one side must be connected DIRECTLY to the battery terminal and there must be NO other cables attached to that battery terminal. To attach cables to the battery terminal that the shunt is connected to is to by-pass the shunt." Although Midnite Solar's diagram has the Whizbang attached to a DC Shunt which is attached to battery, inverter, DC surge protector, and Charge controller.

Sunking- I've also read that fuses should be placed on positive terminals, so would the second set on negative terminal be necessary? or added protection?

And would having those MRBF fuses placed on the battery terminal posts make the 120A breaker switch that I drew (on the charge controller side) redundant, or will it function just as an added level of protection?

[inetdog]

What you need to insure is that the only path for that part of the current that you want to measure is through the shunt.
If you want the shunt to measure total current into and out of the battery there must be no parallel connection to the battery terminal from any equipment that would bypass the shunt.
If you want to measure inverter load current, you would put the shunt in series with the inverter's negative input.
If you want to measure charging current, you would put the shunt in series with the negative connection between the charger and the battery.

[Sunking]

She tried pretty hard to sell me on that Whizbang Jr. thing, so I threw that in there. (Although it's an axiom of mine to remain skeptical about any claim of safety or usefulness, least not from the person whose trying to sell you the thing in question.)

$60 for an accurate reading on battery charge was the jist of it, from what I understand (hence requiring a shunt instead of one of those Blueseas Busbars?)

Two separate issue. Fo rcurrent counting you will need 2 shunts which basically don't tell you a dang thing. Just more money for the seller.

Sunking- I've also read that fuses should be placed on positive terminals, so would the second set on negative terminal be necessary? or added protection?

Depends if you operate the system Grounded or Floating. If Grounded then only on the Ungrounded Circuit Conductor. If Floating then both polarities must be protected.

[Sunking]

Tear your drawing up, it is worthless. Quit talking to sales people and factory reps telling you what you need or do not need. Cheese and Rice dude they are trying to sell you a Lightning Arrestor, Combiner with fuse for a stinking RV. That is a few hundred dollars of stuff you have no use for like a shunt. Ask them if they can sell you four flat tires for the RV while you are talking to them. I am sure you could use those too. Give me a couple of hours and I wil draw up what you need.

Answer these questions.

Panel Wattage
Battery Voltage and Capacity
Inverter Size

[Sunking]

Try This On For Size

Try this.