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RVing message boards => Tech Talk => Solar => Topic started by: Desert_Rat on December 30, 2016, 05:10:51 PM

Title: 6 ----> 24 volts
Post by: Desert_Rat on December 30, 2016, 05:10:51 PM
Anyone see any issues with this first (test) bank?

1) Double crimped
2) Dialectric grease applied
3) 2 AWG cable. I wanted 2/0 but ordered incorrectly. Based on what I've read, it's fine. Bank will be < 5' from MPPT and Inverter

edit: Couple of questions I have are:
1) I'm surprised + is on the negative lead, and visa versa. I guess I should attach the black cable to the + terminal?
2) How much of a gap between batteries should I have when I move them to the box? I'll have 1 24v fan and a vent, both about 3-4" squared.
Title: Re: 6 ----> 24 volts
Post by: SeilerBird on December 30, 2016, 05:20:09 PM
never mind
Title: Re: 6 ----> 24 volts
Post by: Desert_Rat on December 30, 2016, 05:22:34 PM
Funny, I saw a reference to that an hour ago and was all.... what tha...?

Is that really legit?
Title: Re: 6 ----> 24 volts
Post by: SeilerBird on December 30, 2016, 05:29:07 PM
Funny, I saw a reference to that an hour ago and was all.... what tha...?

Is that really legit?
I am sorry, that is wrong. It only gives you 12 volts and you wanted 24. What do you want 24 volts for?
Title: Re: 6 ----> 24 volts
Post by: Desert_Rat on December 30, 2016, 05:32:05 PM
One MPPT for over 2kw of PV. Pretty much mandatory, and on the low side - I'll still need a 100A MPPT.
Title: Re: 6 ----> 24 volts
Post by: SeilerBird on December 30, 2016, 05:39:01 PM
I don't know much about solar since it is such a losing proposition. I'll let the solar experts chime in.
Title: Re: 6 ----> 24 volts
Post by: HueyPilotVN on December 30, 2016, 06:38:12 PM
The series wiring of the four 6 volt batteries will give you 24 volts.

I am still however not sure that I understand why you want to make your system in a non standard (for RVs) voltage.

There is an advantage in that 24 volt systems might use smaller cables than a 12 volt system just as 110 volt systems also do not need large conductors.

The biggest disadvantage is that you are going to need to convert much of your electrical system back to 12 volts either at the battery bank or multiple times at the loads.

You are also going to have to take this into consideration with every component that you buy or convert to 12 volts.

I am just throwing this out there since you are mostly still in the planning stage.

Good Luck with whatever you do and keep us in the loop so that we can learn from your experience with this different approach.

As a side comment my company does use 24 volt power in our Mobile Hospital Units for certain dedicated uses.  The electric servo motors for the hydraulics in the huge slideouts are 24 volt systems but these are stand alone closed systems and the standard for other DC uses in these unit is 12 volts.
Title: Re: 6 ----> 24 volts
Post by: AStravelers on December 30, 2016, 06:52:11 PM
Anyone see any issues with this first (test) bank?

1) Double crimped
2) Dialectric grease applied
3) 2 AWG cable. I wanted 2/0 but ordered incorrectly. Based on what I've read, it's fine. Bank will be < 5' from MPPT and Inverter

edit: Couple of questions I have are:
1) I'm surprised + is on the negative lead, and visa versa. I guess I should attach the black cable to the + terminal?
2) How much of a gap between batteries should I have when I move them to the box? I'll have 1 24v fan and a vent, both about 3-4" squared.
I don't see anything wrong with the way the batteries are wired for a 24V system.  So don't understand you question #1.

I don't know that you need a gap between the batteries, but they should be tied or clamped down.

These are flooded cell batteries so you need good ventilation.  Using a fan I would push air into the compartment.  I am not sure if an exhaust fan could ignite the hydrogen gas given off by the batteries.   

The wire size depends on how much current you push though the wire.  Assuming you used a wire size calculator and accounted for 10' of wire and not the one way distance of 5' then you should be OK. 
Title: Re: 6 ----> 24 volts
Post by: HueyPilotVN on December 30, 2016, 07:15:38 PM
One MPPT for over 2kw of PV. Pretty much mandatory, and on the low side - I'll still need a 100A MPPT.

As I reread your post it may be that your choice of 24 volts may be mostly driven by your plans for the way you intend to handle the "Solar Charging" side of the system.

Most Solar Power systems in RVs take advantage of the fact that there may well be several sources of recharging your batteries.  These input sources include a convertor/charger, possibly an Invertor/Charger, the Alternator from the vehicles engine, as well as the fact that you can have multiple charge lines from different Solar Charge Controllers.

If in fact you are committed to using a single very large charge controller, then you will need large heavy cables to carry the amperage to the batteries.  However this is not the only way to get lots of electrical charge back into your batteries.  You can use multiple charge controllers, (all with smaller cables feeding into a common point).

This will allow you to leave all of your 12 volt system intact.

I have also mentioned in other posts that another alternative is using more than one dedicated battery bank and splitting the loads and the charging sources.
This option would also reduce the weight as opposed to mounting one large battery bank on your trailer tongue.

Just trying to help with alternate suggestions.
Title: Re: 6 ----> 24 volts
Post by: HappyWanderer on December 30, 2016, 07:56:52 PM
Positive is on the negative post because your test leads are reversed on the meter.
Title: Re: 6 ----> 24 volts
Post by: Ernie n Tara on December 31, 2016, 08:24:51 AM
I'd reconsider the 24 V issue. There are two reasons for that; first conversion back from 24 to 12 V is going to be perhaps 90% efficient so you're giving away 200 W of that hard earned power when you use your standard appliances. Second, 24 V equipment is usually much more expensive, if you elect not to down convert, since it is less used and usually designed for commercial applications.

I can't believe it won't be more eficient and less costly to just use larger cables (or more of them).

Ernie
Title: Re: 6 ----> 24 volts
Post by: Desert_Rat on December 31, 2016, 09:07:37 AM
I don't see anything wrong with the way the batteries are wired for a 24V system.  So don't understand you question #1.

If you notice, the red lead (standard + lead)  is tied to the + terminal, but my voltmeter is connected in reverse to get its positive reading. I'm just curious why the positive charge is at the negative terminal on the bank instead of at its positive terminal. It's obviously inherent to a series connect but I found it odd is all.
Title: Re: 6 ----> 24 volts
Post by: Desert_Rat on December 31, 2016, 09:12:53 AM
Y'all may not believe it, but if I chose to share this project on a board centrally dedicated to solar, this 12v curiosity would be about 48v instead. 'You can't use 24v, that's just wrong!' 'I would highly recommend you move to 36 or 48v instead'

Yup

Understand that I've been researching this project for a good while, and while my conclusions may not be perfect, they are conclusions I'm determined to run with. I understand the advantages and disadvantages of 12, 24, 48v. Each has been thoroughly weighed, and my reasoning to go 24v has been addressed here for all to see. This is not a 400 watt project that would be more suitable at 12v, it's gonna be over 2kW and you simply cannot competently manage that at 12v, or you shouldn't have to anyway.

The reason I'm sharing is because I'm a novice with all skills necessary to build the system properly, so I'm seeking more informed guidance along the way. Like I said on my battery box post, 'I'm not a carpenter or metal worker, but I think it came out ok'. But did it? Will 1.5" pine be able to withstand 720lb of batteries... on the road no less? How about tongue weight (that was covered). Was my 2 AWG fitting crimped properly? Are the different cable lengths used considered ok?

Thank you for any and all input.
Title: Re: 6 ----> 24 volts
Post by: markbarendt on December 31, 2016, 09:25:40 AM
If you notice, the red lead (standard + lead)  is tied to the + terminal, but my voltmeter is connected in reverse to get its positive reading. I'm just curious why the positive charge is at the negative terminal on the bank instead of at its positive terminal. It's obviously inherent to a series connect but I found it odd is all.

The black lead should be plugged into the "common" on the meter. Once you correct the plug positions it will read correctly.
Title: Re: 6 ----> 24 volts
Post by: Desert_Rat on December 31, 2016, 09:30:47 AM
Look at the voltmeter, it's reading correctly as is - backwards

Must be inherent to a series connect. positive charge on - terminal, negative charge on + terminal.
Title: Re: 6 ----> 24 volts
Post by: markbarendt on December 31, 2016, 09:36:29 AM
If you notice, the red lead (standard + lead)  is tied to the + terminal, but my voltmeter is connected in reverse to get its positive reading. I'm just curious why the positive charge is at the negative terminal on the bank instead of at its positive terminal. It's obviously inherent to a series connect but I found it odd is all.
Second point. No.

When working with electricity and meters it is important that you understand what to expect.

Finding it odd was the correct response to the reading you got.

When you get an unexpected reading like that asking why is the next step, you did well asking here.

Never assume odd results are inherent, they almost never are.

Title: Re: 6 ----> 24 volts
Post by: Desert_Rat on December 31, 2016, 09:38:15 AM
Excellent point. Electricity is not to be trifled with.
Title: Re: 6 ----> 24 volts
Post by: markbarendt on December 31, 2016, 09:39:49 AM
Look at the voltmeter, it's reading correctly as is - backwards

Must be inherent to a series connect. positive charge on - terminal, negative charge on + terminal.
No

Swap the wires on your meter.

Black to "Com" Red to V
Title: Re: 6 ----> 24 volts
Post by: Desert_Rat on December 31, 2016, 09:44:11 AM
What tha... didn't notice that. I'm blaming it on the dog. yeah, that's it!
Title: Re: 6 ----> 24 volts
Post by: markbarendt on December 31, 2016, 09:57:13 AM
Can't tell what the dog breed is exactly from your avatar but both Ausies and Border Collies are too smart to get that wrong.
Title: Re: 6 ----> 24 volts
Post by: Desert_Rat on December 31, 2016, 10:12:34 AM
Definitely, although the new Aussie pup is presently destroying the joint. Teething stages are terrible.

I'm sitting here wondering what kind of crap I would have caused if I took this voltmeter's readings for fact and used my other one to finish the wiring. Jesus. I recall this old supervisor I had way back when who used to insist we start electronic troubleshooting at its source. "Is it plugged in" and on from there. I thought it was patronizing at the time but have learned that he was right.
Title: Re: 6 ----> 24 volts
Post by: SeilerBird on December 31, 2016, 10:42:46 AM
I don't wish to insult you but I am worried that if you can't hook up a volt meter properly you might not have the chops to wire up a solar project like this.
Title: Re: 6 ----> 24 volts
Post by: Lou Schneider on December 31, 2016, 12:02:23 PM
The only thing wrong is the color of the test leads.  They're reversed at the meter and also reversed at the batteries, with black going to the + terminal and red going to -.

So in this case two wrongs do make it right.  And in San Francisco, three rights make a left turn.
Title: Re: 6 ----> 24 volts
Post by: Gary RV_Wizard on December 31, 2016, 02:40:15 PM
Back to the 24v vs 12v question, I think the sources used in your research are for static systems rather vehicles. The arguments for using a higher voltage are sound, but [in my opinion] the more overwhelming consideration in a mobile solar set-up is that the vehicle & RV systems all run off 12v. It would be much better if they upgraded their operating voltage, but until that happens it's a fact of life.  The conversion of the system run voltage down to 12v will surely cost whatever is gained by using 24 (or 48) volt for the storage system. It may even cost more than what can be gained at 24v.

Automotive designers have known they need to switch to 24v or 48v for over 25 years now.  There were plans in place to make the change-over back in the 1980's, but the cost & difficulty of making the transition has kept it on the back-burner all this time.
Title: Re: 6 ----> 24 volts
Post by: HueyPilotVN on December 31, 2016, 03:31:49 PM
I value Gary's opinion as one of the most if not the most respected on this Forum.

I agree with what he said for several reasons.

I also have come to the opinion that your planning is more inline with a residential system than a RV or vehicle solution.

There is nothing wrong with thinking out of the box, However mobile electrical systems are built around a long established 12 volt standard for everything from light bulbs to electric motors to relays, entertainment systems and appliance controls.  I could list even more but I think the point is established.

Having said that if you are willing to address all of these challenges, you may well design a system that works for you.

There is also at least one more major hurdle that you will need to consider if you go with 2,000 watts of solar panels.

I have just over 1,500 watts of panels, (10 panels), and it take up much of the roof space of both a 40 foot diesel pusher and about half of a 30+ foot Stacker Trailer.

Here are two pictures of the 5 panels on the stacker and the 5 on the dp.

Edit for Lou:  Towing a Stacker I have been known to make three left turns to make a right turn.   LOL


 
Title: Re: 6 ----> 24 volts
Post by: Desert_Rat on December 31, 2016, 07:17:24 PM
Back to the 24v vs 12v question, I think the sources used in your research are for static systems rather vehicles. The arguments for using a higher voltage are sound, but [in my opinion] the more overwhelming consideration in a mobile solar set-up is that the vehicle & RV systems all run off 12v. It would be much better if they upgraded their operating voltage, but until that happens it's a fact of life.  The conversion of the system run voltage down to 12v will surely cost whatever is gained by using 24 (or 48) volt for the storage system. It may even cost more than what can be gained at 24v.

Automotive designers have known they need to switch to 24v or 48v for over 25 years now.  There were plans in place to make the change-over back in the 1980's, but the cost & difficulty of making the transition has kept it on the back-burner all this time.

Maybe it won't work reliably but where I'm at is just adding a 24 > 12v step down. Very small, very easy, very efficient. I don't see the problem.

edit: I should be done with the wiring tomorrow and I'll be sure to update on my results (minus actual PV). The step down (image) is rated at 40 amps, and AIMS didn't see an issue with how I was to use it. I was initially concerned with its small terminals for connectivity, but I'll just use a bus to resolve. The only real 12v issue I've faced is with the slider motor which the manufacturer says needs up to 100A @ 12vDC to pull the slider in. I'm going to resolve that by adding a 13th battery, this one much smaller so I can fit it into a nook in my battery box. I figure a 200+ CCA unit will work fine but I may be test driving a few.
Title: Re: 6 ----> 24 volts
Post by: Desert_Rat on December 31, 2016, 07:38:14 PM
I value Gary's opinion as one of the most if not the most respected on this Forum.

I agree with what he said for several reasons.

I also have come to the opinion that your planning is more inline with a residential system than a RV or vehicle solution.

There is nothing wrong with thinking out of the box, However mobile electrical systems are built around a long established 12 volt standard for everything from light bulbs to electric motors to relays, entertainment systems and appliance controls.  I could list even more but I think the point is established.

Having said that if you are willing to address all of these challenges, you may well design a system that works for you.

There is also at least one more major hurdle that you will need to consider if you go with 2,000 watts of solar panels.

I have just over 1,500 watts of panels, (10 panels), and it take up much of the roof space of both a 40 foot diesel pusher and about half of a 30+ foot Stacker Trailer.

Here are two pictures of the 5 panels on the stacker and the 5 on the dp.

Edit for Lou:  Towing a Stacker I have been known to make three left turns to make a right turn.   LOL

I've mapped the roof out thoroughly. I'll have to relocate the TV and radio antennas, or maybe I'll just toss them. I don't use either anyway. Don't miss the video at the bottom https://www.altestore.com/store/solar-panels/solarworld-340-watt-solar-panel-sunmodule-sw340-xl-mono-p40538/ (https://www.altestore.com/store/solar-panels/solarworld-340-watt-solar-panel-sunmodule-sw340-xl-mono-p40538/)
Title: Re: 6 ----> 24 volts
Post by: HueyPilotVN on December 31, 2016, 08:42:17 PM
I checked out your website for the solar panels.

This site seems to mostly be geared to residential or commercial uses which may be fine and is in line with your wanting to use large panels in higher voltages than commonly used in RV applications.

That does not mean that they will not work, However I would look carefully at the mounting system, framework and frame systems needed to support and mount the panels.

They are rated for high winds but I would ask questions about going down the road and road vibrations.  Not being negative, just saying be sure that you know what you are getting.

There may be a difference in mounting a large array on a stationary platform and a mobile solution.

Each panel measures about 6.5 feet by a little less than 4 feet or 26 square feet.  Six panels would require about 156 square feet of roof space for 2,040 watts.

Be sure to mount them where no shadows will fall across the panels.  You might also try to plan the layout to allow you to move around them or otherwise access them.

The cost per watt is very low but you may make it up with the frame structure and mounting UFO's.

Good Luck and keep us advised of your progress as this will be a learning experience for us traditional guys.

Edit:  These 24 volt panels wired in parallel could certainly also be used with MPPT controllers to work with a 12 volt battery bank
Title: Re: 6 ----> 24 volts
Post by: Desert_Rat on December 31, 2016, 08:45:31 PM
All good info, and which brings a question to mind...
Title: Re: 6 ----> 24 volts
Post by: AStravelers on January 02, 2017, 08:29:18 PM
If you notice, the red lead (standard + lead)  is tied to the + terminal, but my voltmeter is connected in reverse to get its positive reading. I'm just curious why the positive charge is at the negative terminal on the bank instead of at its positive terminal. It's obviously inherent to a series connect but I found it odd is all.
Sorry, but in the photo in the OP does NOT show where the meter leads are attached.  The leads go off the bottom of the photo.  I just went back and looked at the photo in the OP.  I suppose my Firefox browser doesn't show the full photo. 

Since I can't see where the meter is attached all I can go by is the way the battery is wired and it looks like the black cable comes to the top left neg terminal and the 4 batteries are wired in series to the red cable on the plus terminal.  Looks OK to me. 
Title: Re: 6 ----> 24 volts
Post by: xrated on January 03, 2017, 02:32:14 AM
If you look at the very bottom of the photo.....right side, directly below the negative battery terminal, you can just see the tip of the black probe being pushed into the end of a red cable that goes to the Positive battery post at the top right.  Now look at the meter....the black lead is plugged into the voltage lead of the meter.  That makes the red lead from the meter to be plugged into the common and that lead will end up at the negative post of the battery array.  The meter doesn't care what color the leads are, all it's looking for is a positive or negative voltage reading with respect to which lead is on which terminal.....thus the correct voltage reading, but visually, you would think something is wrong because of the meter lead color.
Title: Re: 6 ----> 24 volts
Post by: Desert_Rat on January 13, 2017, 05:00:23 PM
Can I do the attached, and would the result be 1840AH @ 24v?

edit: larger image: http://imgur.com/a/S923b
Title: Re: 6 ----> 24 volts
Post by: Lou Schneider on January 13, 2017, 05:15:40 PM
Series connections add voltage, parallel connections add amp-hours.

I see (4) parallel connected rows of (3) 6 volt batteries in series.  That gives 18 volts per string, not 24 volts.  You need (4) 6 volt batteries in series for 24 volts.

Each series string stores 220 amp-hours, the same as a single battery.

If you reconfigure for (4) batteries in series per row, you'll have 24 volts with (3) rows in parallel at 220 amp-hours each.  This is 660 amp-hours total storage.



Title: Re: 6 ----> 24 volts
Post by: Desert_Rat on January 13, 2017, 05:50:07 PM
Yeah, I see that now. And it's how I presently am wired up.

just trying to get more AH. Any ideas? Can I connect 3 batteries in parallel, then connect 4 of those in series or does it not work that way?
Title: Re: 6 ----> 24 volts
Post by: SeilerBird on January 13, 2017, 05:54:02 PM
The only way to get more AH is by adding more batteries.
Title: Re: 6 ----> 24 volts
Post by: Desert_Rat on January 13, 2017, 06:06:01 PM
Can't do that, I'm stuffed to the gills as it is. just appears to me (theoretically) that if 2 batteries in series make one bigger battery, why can't I connect those bigger batteries in parallel to get more AH? I guess the answer to that is I'm nuts, theoretically.
Title: Re: 6 ----> 24 volts
Post by: Lou Schneider on January 13, 2017, 09:28:45 PM
Amp-hours are only half the story - Amperage x Voltage equals power.

200 amp-hours at 24 volts is 4800 watt-hours ... twice as much power as 200 amp-hours at 12 volts.
Title: Re: 6 ----> 24 volts
Post by: SeilerBird on January 13, 2017, 10:10:33 PM
Can't do that, I'm stuffed to the gills as it is. just appears to me (theoretically) that if 2 batteries in series make one bigger battery, why can't I connect those bigger batteries in parallel to get more AH? I guess the answer to that is I'm nuts, theoretically.
Two batteries in series doubles the voltage. Two batteries in parallel doubles the amperage. But either way you still are getting the same amount of wattage or amp hours. No magic tricks.
Title: Re: 6 ----> 24 volts
Post by: Desert_Rat on January 14, 2017, 08:33:19 AM
Amp-hours are only half the story - Amperage x Voltage equals power.

200 amp-hours at 24 volts is 4800 watt-hours ... twice as much power as 200 amp-hours at 12 volts.

For sure. But I've been looking into this series/parallel connect and it seems to challenge ohms law? Example attached. Source is indicating that 5040w of energy (8*6v*105a) can be wired to create 7440 (24v*310a) of energy with this series/parallel connect.
Title: Re: 6 ----> 24 volts
Post by: prfcdoc on January 14, 2017, 09:14:55 AM
That looks like 210 Ah to me. =5040w
Bob
Title: Re: 6 ----> 24 volts
Post by: Desert_Rat on January 14, 2017, 09:19:53 AM
I thought the same - a typo. But the source does have another parallel lead connected. My connect is attached.

BTW, source: http://solarcity.business/Xwes/deep-cycle-battery-basics/
Title: Re: 6 ----> 24 volts
Post by: Gary RV_Wizard on January 14, 2017, 09:57:31 AM
Once that error in the diagram is corrected (310AH vs 210 AH), all the arithmetic works and Ohms Law is safe.

Quote
just appears to me (theoretically) that if 2 batteries in series make one bigger battery, why can't I connect those bigger batteries in parallel to get more AH?

You can, but that's the "more batteries" that Seilerbird stated. In your case, more sets of 4 batteries, since you have a 24v system. So you have these sets of 4x6v batteries that produce 230AH @ 24v, and you can parallel as many sets as you have room for and bump the AH by 230 for each full set.
Title: Re: 6 ----> 24 volts
Post by: Desert_Rat on January 14, 2017, 10:45:25 AM
What do you think of the images above your response. Why do you suppose the source has those 2 extra parallel leads and is claiming more AH from it?

"Once that error in the diagram is corrected (310AH vs 210 AH), all the arithmetic works and Ohms Law is safe"
I missed that on first read of your response. I agree.
Title: Re: 6 ----> 24 volts
Post by: markbarendt on January 14, 2017, 10:52:48 AM
What do you think of the images above your response. Why do you suppose the source has those 2 extra parallel leads and is claiming more AH from it?

The green lines add nothing except redundancy and don't change the math.

Each battery only has 2 terminals, the total amount of energy available from those terminals is limited absolutely by that fact. Regardless of how many ways you wire it, that is an absolute limit.

Any one system can pull 100%, if there are 2 systems attached the systems have to share that 100%, 50/50, 90/10 or whatever.
Title: Re: 6 ----> 24 volts
Post by: Desert_Rat on January 14, 2017, 11:07:27 AM
So you think the source's claim of 310 ah is a typo. I think that makes more sense but I'd still like to know why the 2 parallel leads are added. What's the point of that?
Title: Re: 6 ----> 24 volts
Post by: markbarendt on January 14, 2017, 11:50:46 AM
Electricity is like black magic for the untrained, the extra leads are a form of wishful thinking.
Title: Re: 6 ----> 24 volts
Post by: prfcdoc on January 14, 2017, 01:15:41 PM
Electricity is like black magic for the untrained, the extra leads are a form of wishful thinking.
Yes sir! My thought as well.
Title: Re: 6 ----> 24 volts
Post by: Desert_Rat on January 14, 2017, 02:50:52 PM
Electricity is like black magic for the untrained, the extra leads are a form of wishful thinking.

With that I'll assume you mean the source believes the bank is better balanced by doing it in that manner. The source is theoretically correct but I agree that it seems overly redundant.
Title: Re: 6 ----> 24 volts
Post by: markbarendt on January 14, 2017, 03:04:39 PM
With that I'll assume you mean the source believes the bank is better balanced by doing it in that manner. The source is theoretically correct but I agree that it seems overly redundant.
No, the green drawn in wires do nothing extra. Zero, zip, zilch, nada, squat... The green wires have no value and should not be used IMO.

The source is not correct.
Title: Re: 6 ----> 24 volts
Post by: markbarendt on January 14, 2017, 03:20:45 PM
In this picture each bank of 4 batteries provides a total potential of 230ah at 24 volts, that's it. The green lines change absolutely nothing.

3 banksx230ah at 24volts=690ah at 24 volts all in with all 3 banks.
Title: Re: 6 ----> 24 volts
Post by: markbarendt on January 15, 2017, 08:15:10 AM
One way to think of "a battery bank wired in series" is as "a single battery".

Bear with me Desert_Rat.

The batteries you are using are made up of smaller 2-volt batteries (cells).

To build a 6-volt battery one simply puts three 2-volt batteries (cells) in a box and then wire them in series.

A 12 volt battery can be built in the same manner by simply putting six 2-volt batteries (cells) together, a 24-volt battery is a collection of twelve 2-volt batteries (cells) wired in series.

The number of boxes the 2-volt batteries (cells) are housed in is irrelevant.

Whether the bank is wired internally or externally is irrelevant.

Any bank that is wired in series effectively acts as a single battery.
Title: Re: 6 ----> 24 volts
Post by: Gary RV_Wizard on January 15, 2017, 09:57:17 AM
About the most you can say for the 4 green wires is that they may be shorter than the blacks & reds that make the same electrical connection. Maybe that helps balance the loading by providing a slightly lower resistance alternate path, but that's true only if the Reds & Blacks are undersize or just marginal in size.
Title: Re: 6 ----> 24 volts
Post by: Desert_Rat on January 16, 2017, 07:55:34 AM
"Good morning Robert,

Thank you for the email, I can confirm that indeed we have made a typing error on the website which we will fix right away. The correct value should be 210Ah and not 310Ah as indicated on the website. I personally thank you for bringing it to my attention.

I do hope that the rest of the website content is of great value to you Robert and please feel free to alert me to any other discrepancies you may find on the website, it will be greatly appreciated.

Best Regards"

Title: Re: 6 ----> 24 volts
Post by: Artcele on January 18, 2017, 06:19:37 AM
Your schematic shows a 4 in serie first, then a 3 in parallel, 3S4P.
There is also the 3 in parallel first, then 4 in serie, 4S3P.
In your 3SP4, take in account that if any of the battery/cell fails, the whole string in this 4S will be faulty, not supplying anymore, turning into 2S4P
In a 4S3P, if a battery fails in a 3P, the impact is less, the 2 others in the 3P go on supplying.
(Batteries are the same model, considering having the same voltage/SOC in any 3P)

Also, you could add diode insulation and fault protection, by adding diodes (good amperage) isolating the 4 (3S4P), or the 3 (4S3P), for both charging and discharging. Not very costly.
The advise is also to add fuses (good amperage) in the battery to converter, unless already in the converter setup.

If you stick with your 3S4P schematic, the batteries voltage in any string can vary independently of each other, and in the long run, it is always safe to monitor the voltage of each battery, even with a very simple battery monitor.

The green lines are outlining the idea of a "bus bar" type connection, it is better being shorter, linking each string. The negative/black line then just need one connection to this green "bus bar".
Title: Re: 6 ----> 24 volts
Post by: Desert_Rat on January 18, 2017, 08:05:13 PM
354P, 453R? Sorry, I don't understand this terminology. I understand the gist and will look into implementing it. Also, further explanation of diode use would be appreciated.

The attached image is what I have so far. Again, PV is not in yet, will be in a month or so and will be 2040w.

Products:
Deca GC15: http://www.dekabatteries.com/assets/base/0248.pdf (http://www.dekabatteries.com/assets/base/0248.pdf)
AIMS 120/24/3000: https://www.amazon.com/AIMS-Power-PICOGLF30W24V120VR-Inverter-Charger/dp/B00NLLSGMY/ref=sr_1_1?s=automotive&ie=UTF8&qid=1484791027&sr=1-1&keywords=AIMS+Power+PICOGLF30W24V120VR+24V+Pure+Sine+Inverter+Charger (https://www.amazon.com/AIMS-Power-PICOGLF30W24V120VR-Inverter-Charger/dp/B00NLLSGMY/ref=sr_1_1?s=automotive&ie=UTF8&qid=1484791027&sr=1-1&keywords=AIMS+Power+PICOGLF30W24V120VR+24V+Pure+Sine+Inverter+Charger)
AIMS 24 to 12v step down: https://www.amazon.com/AIMS-Power-CON40A2412-Amp-Converter/dp/B01JIZWX52/ref=sr_1_1?s=automotive&ie=UTF8&qid=1484791122&sr=1-1&keywords=AIMS+Power+CON40A2412+40+Amp+24V+DC+to+12V+DC+Converter (https://www.amazon.com/AIMS-Power-CON40A2412-Amp-Converter/dp/B01JIZWX52/ref=sr_1_1?s=automotive&ie=UTF8&qid=1484791122&sr=1-1&keywords=AIMS+Power+CON40A2412+40+Amp+24V+DC+to+12V+DC+Converter)
Ammeter: https://www.amazon.com/bayite-6-5-100V-Display-Multimeter-Voltmeter/dp/B013PKYILS/ref=sr_1_1?s=hi&ie=UTF8&qid=1484791435&sr=1-1&keywords=bayite+DC+6.5-100V+0-100A+LCD+Display+Digital+Current+Voltage+Power+Energy+Meter+Multimeter+Ammeter+Voltmeter+with+100A+Current+Shunt (https://www.amazon.com/bayite-6-5-100V-Display-Multimeter-Voltmeter/dp/B013PKYILS/ref=sr_1_1?s=hi&ie=UTF8&qid=1484791435&sr=1-1&keywords=bayite+DC+6.5-100V+0-100A+LCD+Display+Digital+Current+Voltage+Power+Energy+Meter+Multimeter+Ammeter+Voltmeter+with+100A+Current+Shunt)

Cables, terminators, fuses, etc also via Amazon.
Title: Re: 6 ----> 24 volts
Post by: Desert_Rat on January 18, 2017, 08:07:18 PM
edit: Larger http://imgur.com/a/Z8eAh (http://imgur.com/a/Z8eAh)