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Old 09-29-2019, 12:22 PM   #1
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Please please help with solar! Almost there!

Hello all!
I am really hoping to get some help with a few questions regarding my solar setup...I have done my best to research and install what I can so far and the last few qís are ones I just canít seem to find an answer to!!! Some super basic- I have been moving at a turtles pace in understanding this all and installing but any and all help would be sooooooooo appreciated!

Below is a list of what I have and that is already installed.
AIMS 3000W inverter/charger - wired for shore power as well
Midnite classic 150SL
4 12volt SLD batteries wired parallel
Breaker box
Switch

Below is what I have on hand hoping to install this week.
Four 250 watt mono pv panels
Bogart tri-metric battery system and fuse
500 amp dc shunt
midnite solar jr whiz bang
Midnite battery temp sensor
Aims battery temp sensor

I will try and post pics below
Wow, just spent $6 and a few hours on photobucket putting my pics on to find out thatís not allowed anymore. Bummer. I can email pics if anyone can help out.


I am feeling close to the install but still have these questions...

The positive and negative wires coming from the panels are 12 awg, I ordered 10 awg extension wire and am wondering if I should try and get into the box and change out their wiring for 10 awg or order 12 awg wires for everything running down to the charge controller?

I have four panels, two of which I will be connecting together in a series on both sides of the bus connected together in parallel. 2 in a series on one side, 2 in a series on the other side, then bring both sides together parallel with Y connectors. I am hoping the Y connectors I got are suffice for joining the two negative leads and two positive leads from both sides - I have seen some different ones out there and have yet to notice a difference in function. My next question is - in putting all this info into the midnite solar calculator I seamed to be fine with my 150 so classic. I am looking into coming through the roof and am wondering if I should get a combiner box or not? Does it make any sense? Will a combiner box just nullify the function of two series in parallel which is what I am hoping to keep?

My plan so far has been to, as mentioned, put both series in parallel, order 12 awg wire and do my own mc4 connections, connect the two series together in parallel with y branches and run a positive and negative down to the charge controller with a fuse(30 or 50 amp in the middle of the positive?) is there anything I am missing here guys?????? PLEASE LET ME KNOW!!!!! So very appreciated.

The panels will be on the back of the bus with two panels joined together on gas hinges at the outside of the bus so that they can tilt to match the opposing side. I am looking into roof entry options....any suggestions would be sooo appreciated. I still have so many qís but Iíll start there.



THANK YOU THANK YOU THANK YOU!
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Old 09-29-2019, 12:32 PM   #2
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First thing that caught my attention Was The four 12 volt batteries in parallel.

Not a good idea unless you like buying batteries.

There is a great stickie over on solarpaneltalk.com that explains it better than I can.

I will see if I can find the link and post it here.
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Old 09-29-2019, 12:38 PM   #3
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https://www.solarpaneltalk.com/forum...ry-connections

Quoted from solarpaneltalk:
First a little background. When you parallel batteries, it is almost impossible to balance Battery Internal Resistances, Cable and Connector Resistances. This forces one string to do most of the work. It weakens the strings and results in early failure.
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Old 09-29-2019, 12:43 PM   #4
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Eeeek! Thanks for the info! I was starting to rethink my batteries anyway. Any personal suggestions? I’ve been reading a ton but my brain is mashed potatoes at this point.
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Old 09-29-2019, 01:11 PM   #5
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On a side note I thought I had to keep them parallel to keep at 12 volts? Doing them in a series would create 48 correct?
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Old 09-29-2019, 01:24 PM   #6
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Quote:
Originally Posted by Nickentloper View Post
On a side note I thought I had to keep them parallel to keep at 12 volts? Doing them in a series would create 48 correct?
You run strings of series in parallel
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Old 09-29-2019, 03:56 PM   #7
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The solarpaneltalk link info seems dubious.

Quote:
You must equalize the string voltage before connecting. Otherwise if you have more than 1/4 volt difference between strings, you will weld the disconnect contacts together.
Unless I misunderstand what "strings" means, this seems like nonsense. I've connected batteries in parallel with _far_ more than 1/4 of a volt difference and you don't see sparks flying. In fact, lots of people do it all the time- when jumping a car with a dead battery.

Most notably I've connected my Tesla packs together in parallel with >1V difference. They are extremely low resistance, and will happily discharge at 1000A given the right circumstances. And yet, connected to my bus bars via 150A breakers on each pack, none of the breakers tripped. They WOULD trip with current like the kind required to melt/weld the contacts as cited.

Either I'm misunderstanding something or _some_ of the information presented just isn't correct.


Edit: Are they saying the order of parallel/series matters (series-then-parallel vs parallel-then-series)? I doubt it with the other information presented.
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Old 09-29-2019, 05:29 PM   #8
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IMHO, 4 batteries in parallel is not a bad thing. Going more than that will make matters more drastic. BUT, if you make EVERY wire from the distribution block to each battery the exact same length, and of the same high gauge/ quality, the effects are very minimal. I build 18650 lithium packs for renewable energy and EV's, they can consist of HUNDREDS of cells in parallel, and series. THOSE need battery management systems to balance and keep properly charged/ temp controlled. 12V is the least efficient setup, 48v being much better, but in a vehicle, I too go with 12v battery set ups. If 4 batteries are not enough storage for you, then you are purchasing too low of ah's(amp hours) per battery. I have my system set up for almost a full year now, not even installed on a vehicle to test and find the right donor step van. The batteries have lost less than 1% of their storage capacity in that time. Mine are 255ah rated x4. Changing to higher voltage batteries can up efficiency, but cause other headaches as well. Such as integrating "engine" electronics to the "coach" electronics for emergency jump starting, or in my case using high current alternators for charging while on the road. Many pluses and minuses to either set up. It is like most things DIY here....what works best for you?
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Old 09-29-2019, 05:50 PM   #9
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Yes putting strings in parallel is suboptimal, but done all the time. Two for redundancy is fine IMO more than three will cause balancing issues.

Ideal if redundancy is not a concern is a single string by right-sizing the cells for capacity desired.

This issue has nothing to do with cells in parallel at the lowest level. Only problem there is inability to monitor individual cells.

The Whizbang Jr and Trimetric are redundant, why both?

Use Imgur for free hosting, or just resize and upload here.

No problem extending #12 wire with thicker, but do crimp properly, heat-shrink insulation.

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Lead being self-regulating wrt current, matching voltage before paralleling isn't so critical as with lithium.
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Old 09-29-2019, 05:58 PM   #10
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This issue has nothing to do with cells in parallel at the lowest level.
Exactly. As OP seems to have 4x 12V batteries, all in parallel, so this conversation about balancing is a complete distraction.



Whenever you run anything in _series_ you will have balancing issues. Even if it is just one set. Cells don't equalize their voltages when in series- but they do when in parallel.



One way or another, in series you have to balance each cell, so it makes more sense to run sets of parallel cells in series to get your desired voltage. That way you can balance the whole bank with one balancer.


In my case I can't avoid running series in parallel since each pack is its own series, so I have to have a balancer for each pack.
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Old 09-29-2019, 06:03 PM   #11
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Think I’m good on the batteries. I’ll try to keep researching my other questions. If anyone has a good source for information it would be much appreciated. Scouring the web until then. Thanks for the input
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Old 09-29-2019, 06:21 PM   #12
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Quote:
Originally Posted by kazetsukai View Post
Exactly. As OP seems to have 4x 12V batteries, all in parallel, so this conversation about balancing is a complete distraction.



Whenever you run anything in _series_ you will have balancing issues. Even if it is just one set. Cells don't equalize their voltages when in series- but they do when in parallel.



One way or another, in series you have to balance each cell, so it makes more sense to run sets of parallel cells in series to get your desired voltage. That way you can balance the whole bank with one balancer.


In my case I can't avoid running series in parallel since each pack is its own series, so I have to have a balancer for each pack.

I don't know how to respond politely.

I will simply caution folks to seek advice from a professional before following advice here.
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Old 09-29-2019, 06:28 PM   #13
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I don't know how to respond politely.
You could point out the specifics you may find inaccurate. I'm up for being corrected. Perhaps I misused terminology or got something wrong. I think that's more constructive and polite than the almost rhetorical "seek a professional" response, although it is probably good advice.
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Old 09-29-2019, 06:40 PM   #14
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EVERYTHING on this site are opinions. I will be the 1st to admit many of my personal designs and creations do not 100% follow federal/ agency guidlines, but will still pass any inspection/ safety check. BUT, there is ALWAYS some loss, it is up to each of us to decide what is best for our situation, and wallet. I could change to a 48V set up, by replacing inverter/charger, Batteries, and adding in voltage converters to step down voltage before integrating coach to engine electronics, but the cost to benefit ratio just does not add up. Thousands to extend the life of my battery bank by maybe a year, when I could save that $$ and buy new batteries with it in 5-10years. Thats just MY personal feelings on that. I hope nobody takes my opinions as gospel, or attack. I give info on how I see it, based on my experiences. It is up to each of us to decide how we choose to proceed. On my ebike, I run dual 70v battery packs at 80amps in parallel, the manufacturer says it cannot take over 58.8v @50amps, but with the proper knowledge(and hiding that fact from police if stopped) I do it daily at 45MPH+ Granted those packs NEED BMS units to monitor and balance the cells, but thats 280 individual cells in a series/ parallel combination. When it is a single string of 4 batteries in parallel, the losses and variances are minimal, but DO exist.
Again, none of this is meant to attack or demean any others opinion. It is just my own.
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Old 09-29-2019, 07:00 PM   #15
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I found it cheaper to buy some crimps, pins and appropriate wire and make my own wires with MC4 connectors.
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Old 09-29-2019, 07:01 PM   #16
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When you want to paint your roof with Henry's I won't argue with you. I wouldn't use it myself. But It's your bus.

If you want to paint it hot pink, I wouldn't but I won't argue with you.

If you want to put in a filter so you can recycle shower water, have at it. I certainly don't want that.

If I think that you are getting bad electrical advice I will speak up. People die from electrical failures. Two of them were family members.

I took some of Mike Holt's seminars when I was working on my electricians license and he started one of them with a slide show with news stories of people who have died due to faulty electrical. It made an impression.
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Old 09-29-2019, 07:47 PM   #17
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Exactly. As OP seems to have 4x 12V batteries, all in parallel, so this conversation about balancing is a complete distraction.
Wut? Each of those 12V batteries is a series string, 6S * 2V each.

As I said 3-4 in parallel is very commonly done, not a disaster, but certainly not optimal if a rig is being planned from the ground up.

> Cells don't equalize their voltages when in series- but they do when in parallel.

Cells may, but that is not the case here.

> One way or another, in series you have to balance each cell, so it makes more sense to run sets of parallel cells in series to get your desired voltage. That way you can balance the whole bank with one balancer.

Again, true if we were talking about cells, but we're not.


However, moot point in this case if OP is happy so be it.
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Old 09-29-2019, 08:16 PM   #18
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Originally Posted by Nickentloper View Post
My plan so far has been to, as mentioned, put both series in parallel, order 12 awg wire and do my own mc4 connections, connect the two series together in parallel with y branches and run a positive and negative down to the charge controller with a fuse(30 or 50 amp in the middle of the positive?) is there anything I am missing here guys?????? PLEASE LET ME KNOW!!!!! So very appreciated.
That's how we did ours. We used 10ga wire for 4-280w panels and (I think?) a 40A double pole breaker on the + and - wires to the charge controller. The solar dealer set us up with all the wiring, breakers and connections. If you do your own MC4 connections, buy a good crimper for MC4 connections....don't just use regular pliers or something. I think ours was like 20 bucks on Amazon. From the charge controller to the batteries, we used 5ft. of 4ga cable with a 100A breaker.
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Old 09-29-2019, 08:46 PM   #19
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On a side note I thought I had to keep them parallel to keep at 12 volts? Doing them in a series would create 48 correct?
Connecting 4 - 12 volt batteries in series will yield a 48 volt bank. The a/h rating of your bank will be the same as the batteries.

Assume 12v - 150 a/h batteries. I don't know if that's what you have but for illustration we will assume.

Connected in series the voltage is additive and a/h remains the same. Four 12v 150a/h batteries in series will give you 48v 150 a/h.

Connected in parallel the a/h rating is additive and voltage remains the same. Four 12v 150a/h batteries connected in parallel will give you 12v 600a/h.

The power available from either configuration is the same.

P=I*E. Power equals current in amps times voltage in volts.

48v x 150a/h = 7200what hours or 7.2kwh

12v x 600a/h = 7.2kwh.

The advantages to the higher voltage, lower current that you get with the series connected batteries is that you can use smaller gauge wire and save $ and you avoid the equalization issues that can be problematic with parallel connected batteries.

Folks get "stuck in 12v box". When dealing with larger solar arrays and battery banks the higher voltage solutions make a lot of sense.

You can build a 48v 1000a/h bank without any parallel batteries....., Why bother with the pitfalls of 4 or more parallel batteries?
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Old 09-29-2019, 08:49 PM   #20
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Because of all the added complexity of stepping down to 12V for all the load devices not available in higher DC increments.

Avoid inverters like the plague if living off-grid for extended periods on (mostly-) solar
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