battery bank wiring

[defed]

i think i have this correct, but want to make sure.  i was reading about paralleling more than 2 batteries, and it sort of got me confused about the simplicity of my bank, so i figured i should check here.



24v bank, 2 sets of series strings parallel.  can i also take the load off the opposite terminal that the charge is going to?  i figure it won't make a difference and it would prevent stacking too many connectors on a terminal.

[TomW]

Defed;

Electrically they are the same point in the circuit. Assumption being the conductors (wires) are of sufficient size for the length and expected current.

Should not be a problem.

Tom

[ChrisOlson]

24v bank, 2 sets of series strings parallel.  can i also take the load off the opposite terminal that the charge is going to?  i figure it won't make a difference and it would prevent stacking too many connectors on a terminal.

You certainly can.  But I like to pull the load and supply the charge current to the bank at the same points.  That way the load can pull directly from the charge source without having to go thru the bank wiring.
--
Chris

[defed]

ok, thanks, didn't think about that.  but in general, i presume i have it correct...pull pos/neg from opposite corners (since nobody made any negative comments)?

i think i might put some sort of buss bar for the in/out connections just to save on having so many wires stacked.  there will be a turbine and solar panels connected, so that would be about 5 wires on the terminals (turbine in, solar in, parallel connection, load out, dump load).

[ghurd]

Some of the car stereo shops have some neat fuse or distribution blocks that are pretty cool for small bus bars.
Retail shops get pretty big $ for then, but ebay or online is reasonable.

Edit-  There are a couple different types.
Some have a big wire in, smaller wires out.
Some clamp to the battery post, with wires going out.

If you want a negative comment, then the positive line has a bit of a dog leg in the sketch.
Happy now?  
G-

[ChrisOlson]

i think i might put some sort of buss bar for the in/out connections just to save on having so many wires stacked.  there will be a turbine and solar panels connected, so that would be about 5 wires on the terminals (turbine in, solar in, parallel connection, load out, dump load).

What are you going to use for a DC disconnect?  Typically you don't make all those connections at the battery bank.  You have one big set of cables from the bank to a DC disconnect and the disconnect either has built-in, or feeds, a DC distribution bus or panel.  Your inverter(s), turbines, solar panels, etc.. are all hooked to the distribution bus or panel.

A bank with 8 batteries can deliver several thousand amps if something shorts out.  You need some sort of disconnect and fusing to keep the fire as small as possible if that happens.
--
Chris

[defed]

not sure how i'm doing the disconnects/fuses yet.  currently, i have a pair of junk batteries acting as a load on the turbine and solar.  i have a fused disconnect between the solar charge controller and batteries, while the turbine just connects direct.  when i want to put a load on the batteries (to load the solar charger to get it to stop limiting the panels output while in float), i just hook some DC loads to the batteries w/ some clips.  this is my basic experiment stage.  with the new batteries, it will be my intermediate experiment stage....no inverter, just the charge sources and some sort of timed/sensor/voltage activated dc load, and the diversion load thru the solar controller.  i'm not going to get the power to its final destination this year.  it's basically going to be a waste of the power, but should still allow me to get some measurements and other data on output etc.

[ChrisOlson]

not sure how i'm doing the disconnects/fuses yet

Just a hint on how to do it cheap and right - SquareD QO panels and breakers are DC rated up to the amp capacity of the panel and breakers, not to exceed 48 volts DC.  They can be used on 12 and 24 volt systems but not 48 volt because the voltage goes higher than 48 on a 48 volt system.  They make excellent disconnects for solar arrays and turbines at a fraction of the cost of what you'll pay some solar outfit for a DC disconnect.

This is a 200 amp disconnect I built for an inverter using a SquareD QO outdoor disconnect for $57 - the breaker will hold 200 amps continuous and 230 amps for about 30 seconds on my 12 volt system, and then it trips:







I have no affiliation whatsoever with SquareD or Schnieder Electric - I just use their QO stuff for DC panels.  And note I said QO panels and breakers.  Their Homeline panels and breakers are NOT DC rated and they have aluminum buses in them instead of copper like the QO panels have.
--
Chris

[defed]

i knew about the QO breakers from squareD, but wasn't aware of the 48v limit for DC.  i am debating going 48v when i make my 10' turbine, so not sure how much i want to spend too much on QO items if they won't work on 48v.

i have 2 disconnects on the solar side, i made them from cutler-hammer outdoor 240v/60a fused disconnect boxes.  i used DC rated fuses.  i have one between the panels and controller, and between controller and batteries.  was about $10 for each box/fuse combo.

i have been studying this guys page for ideas:

http://home.comcast.net/~n3qik/Site/Solar_Page_10.html

he uses a QO load center for his battery distribution.

[defed]

this is a simplified diagram of the wiring to my battery bank.  would i fuse/disconnect between the battery and the + distribution block and the + leg of each load?  the solar is already fused/disconnected before the distribution block.

[ghurd]

"would i fuse/disconnect between the battery and the + distribution block and the + leg of each load?"
Yes.

Might contact SqD about the 48VDC limit.
I would think 48VDC nominal rating should handle a 48V battery bank... but not sure.
G-

[defed]

thanks Ghurd.  i think the equalization voltage on a 48v bank is at least 60v, so i will have to look into it.

[defed]

ok, here's a side question in regards to going to 48v.  let's say i have 8 batteries...6v @ 100ah.  wired in 24v (series/parallel), this is 24v @ 200ah.  if i was to wire them for 48v (series), i would have 48v at 100ah.  both banks have 4800 watt hrs, so they are they equal in capacity or does more ah have some bearing on their output?  i presume them to be equal, but there's alot i don't quite understand about battery specs!

[TomW]

"would i fuse/disconnect between the battery and the + distribution block and the + leg of each load?"
Yes.

Might contact SqD about the 48VDC limit.
I would think 48VDC nominal rating should handle a 48V battery bank... but not sure.
G-

G;

I list breakers on Feebay a lot. A lot of the bigger 3 phase units are rated  at 250 VDC. Kind of expensive but those are what I use. But then I get them surplus and wholesale so it is a no brainer. I think I have one 20 amp and one 50 amp DC rated breaker listed now in my Feebay store.

I use the 2 outside phases on the + and - cables for battery protection.

I am using this 225 Amp 250 VDC Magnetic Trip Adjustable 3 phase Siemens breaker on my new 810 AH Absolyte bank:



Just another angle on protection if you can find them.

Shameless pimp follows:

$50 Cutler-Hammer 20 Amp:

http://cgi.ebay.com/Cutler-Hammer-Series-C-Breaker-EHD-14K-20-Amp-AC-DC-/270625374488?pt=BI_Circuit_Breakers_Transformers&hash=item3f02878118

$70 ABB 50 Amp:

http://cgi.ebay.com/ABB-S3N-50-Amp-AC-DC-Breaker-3-Pole-/280545794300?pt=BI_Circuit_Breakers_Transformers&hash=item4151d518fc

Because he is looking into breakers.

Tom

[ghurd]

"side question in regards to going to 48v"
48V is generally for higher power systems.  That's why you don't find 48V 100W inverters.

If you have a 2500W load, that's a slew of losses and amps at 12V.
If the charging system is up to dealing with a 2500W load on a regular basis, then that's a lot of 12V charging amps and money for wire.

If the loads and charging are small, then 12V is fine.
It doesn't make sense to have a 48V system charged by 50W of solar panel and a 0.6 meter diameter windmill.

Another reason could be to have the same watt-hours without paralleling batteries.  A bum battery can be a headache, and its worse if there are a lot of parallel strings.

12V equalization is 15V, but a "12V" breaker better be able to handle it.
And a '12V' breaker better be up to service in my car, which runs at 14.4V or a bit better.
48V is just 4x the same numbers.

TomW's breakers are a good deal, and rated plenty high enough!
G-

[ChrisOlson]

Might contact SqD about the 48VDC limit.

I've already talked directly to the engineers at Schneider Electric (manufacturer of SquareD equipment) about that.  The 48 VDC is a hard limit - QO panels and breakers are suitable for 12, 24 and 36 VDC applications.  They cannot be used on any application where the voltage exceeds 48 VDC.

SquareD's bigger two and three pole heavy duty safety switches are rated to 250 VDC, and some of their panels are rated to 600 VDC.  But not the QO line - 48 VDC max.  When I talked to the engineer there (his name was Glen) he said you could probably use it on a 48 volt system where the voltage can rise to 60, but the QO line is not UL Listed for that.

--
Chris

[defed]

"side question in regards to going to 48v"
48V is generally for higher power systems.  That's why you don't find 48V 100W inverters.

If you have a 2500W load, that's a slew of losses and amps at 12V.
If the charging system is up to dealing with a 2500W load on a regular basis, then that's a lot of 12V charging amps and money for wire.

If the loads and charging are small, then 12V is fine.
It doesn't make sense to have a 48V system charged by 50W of solar panel and a 0.6 meter diameter windmill.

Another reason could be to have the same watt-hours without paralleling batteries.  A bum battery can be a headache, and its worse if there are a lot of parallel strings.

12V equalization is 15V, but a "12V" breaker better be able to handle it.
And a '12V' breaker better be up to service in my car, which runs at 14.4V or a bit better.
48V is just 4x the same numbers.

TomW's breakers are a good deal, and rated plenty high enough!
G-

the main reason for me to go 48v is for less voltage drop for a given length.  it doesn't matter that much for the solar because it will already be outputting 60v minimum to the mppt controller, which then makes it 24v or 48v or whatever battery i have.  i will run the 60v for the longest distance, and the 24v short as possible.  the turbine will be run on the AC side for most of the length.  more volts will still help limit the losses.  i have a 4' turbine (test model) and 700w of solar, and plan to get the 10' turbine going soon and add more solar as i can.  so 48v would be useful to me in the future.  for now, i have everything at 24v.  i have the batteries to do a single string of 48v when needed...just wasn't 100% sure if i want to.

[ChrisOlson]

the main reason for me to go 48v is for less voltage drop for a given length.

I originally had 12 volt in my house and did a lot of 12 volt wiring in the house - putting in 12 volt florescent lighting in some rooms, 12 volt LED night lights, and 12 volt power receptacles in various rooms for charging cell phones with mobile chargers and running laptops with 12 v -> 19 volt mobile converters that we got from Dell.

Then I went to 48 volt, which basically only required changing the stators in the turbines because I didn't have solar at that time.  I still wanted to use the 12 volt stuff so I tapped off one string of 12 volts in the battery bank to run that stuff.  Keeping the battery bank balanced was somewhat of a challenge.

Then we bought a solar array, that I got a real good deal on, made of up ten 123 watt Sharp 12 volt panels.  I made the decision to go back to 12 volt because the cost of equipment is cheaper.  I wired the panels to a 100 amp QO box with a 15 amp breaker going to each pair panels hooked in parallel and all the panels paralleled at the bus in the panel.  I changed the turbine stators back to 12 volt, got rid of my 240 split phase XW6048 inverter and put in a AIMS Power 3 kW 120 volt inverter and two Schumacher 2 kW 120 volt inverters, all powering their own panels, with power supplied by a 3,000 amp-hour battery bank.

I've been totally happy with the 12 volt system.  I've seen the solar put out up to 80 amps on a nice sunny day, and the turbines can put out up to 200 amps on a good windy day.  All it really takes is bigger wire from the turbines and bigger cables going to the inverters, and the rest is the same as any of them, other than the dump load.  My TS-60 that I used on the 48 volt system would no longer work on this high-amp system so I went to a relay-type controller that closes the relay at 14.7 volts, that relay turns on 120 volt power to the coil in a three pole contactor, which in turn turns on power to two 1.8 kW AC water heater elements powered by the inverters.  I put a timer on the water heater elements that holds the element contactor on for 12 minutes once it's turned on so the relays aren't clicking in and out all the time.  It works really good - it instantly drops the bank to 13.5 loaded volts and holds it there for 12 minutes, turns off the load and tests to see whether it should be done again.  And I actually get hot water out of the deal, as well as powering the rest of the house.

So there's pros and cons, but I found that everything you want to buy for 48 volt, from controllers to inverters, is more expensive.  I spent some extra money on wire but I don't think there's any significant losses compared to 48 volt.  At 250 amps of power coming in, none of my electrical equipment even warms up because it's all coming from different sources that are combined at the battery bank.  And now all my 12 volt stuff in the house works without having to worry about keeping the bank balanced.

So it can be done on a lower voltage system - all you need to do is buy some bigger wire to hook things up and keep the inverter(s) as close to the batteries as possible.
--
Chris

[defed]

So it can be done on a lower voltage system - all you need to do is buy some bigger wire to hook things up and keep the inverter(s) as close to the batteries as possible.

how long are your wire runs from turbine to batts and solar to charge controller/batts?  mine would be at least 100', and even at 60v from the solar, i need like #4 to stay within 1% voltage drop.  maybe i'll stick w/ 24v then...compromise between slightly cheaper wiring (than 12v), (maybe) cheaper inverters than 48v, and the QO stuff seems relatively inexpensive that i couldn't use on 48v.

[ChrisOlson]

how long are your wire runs from turbine to batts and solar to charge controller/batts?  mine would be at least 100', and even at 60v from the solar, i need like #4 to stay within 1% voltage drop.  maybe i'll stick w/ 24v then...compromise between slightly cheaper wiring (than 12v), (maybe) cheaper inverters than 48v, and the QO stuff seems relatively inexpensive that i couldn't use on 48v.

On the solar array, the run from the panels to the QO Load Center is about 35 feet from the closest pair of panels, about about 50 feet from the furthest ones, and there's one red and one black 10 AWG wire coming from each pair of panels to the breaker for that pair.  From the QO box to the main DC bus is about 4 feet and that's connected with #4 copper.

I have a 200 amp outdoor DC disconnect mounted on the wall of the back of the house.  All the turbines feed the bus in that disconnect, and that disconnect feeds the main DC bus in the garage.  All three turbines are rectified at the tower bases and DC is run underground to the disconnect so I only had to run two conductors instead of three.  The run from the 13 footer is 12 feet.  The run from one 10 footer is 133 feet.  The run from the other 10 footer is 161 feet.  All three turbines feed the outdoor disconnect with 1/0 direct-bury copper.  The outdoor disconnect is about 10 feet from the main DC bus and feeds it with 2/0 copper.

All the inverters pull their power from the main DC bus.  The 3 kW AIMS Power inverter is connected with 3 feet of 1/0 copper, the two Schumachers are connected with dual #4 copper each, and each inverter has a DC disconnect.  The battery bank is arranged in six strings, each string is 500 amp-hours, and each string is hooked to the main DC bus with #4 copper.  So there's six #4 positive and six #4 negative wires feeding that main bus with 500 amp inline fuses on each positive right at the battery.

The most dangerous part of the whole system is that main DC bus.  The supply to that bus is a potential 5,000 amps surge and continuous 3,000 amps if it were shorted negative to positive.  In the old days I didn't have it fused to the batteries.  I accidentally dropped a steel handled Craftsman hammer across it once.  That hammer was instantly vaporized and disappeared with a loud BANG, spraying me with molten metal in the process.  Since then I've fused the battery stings and got the negative and positive sides of that bus in separate boxes.
--
Chris

[defed]

getting further along in my projects, and i stumbled on this old thread of mine thru a yahoo search.

i am working on getting my solar stuff into the house, and and having some trouble w/ my DC disconnects...i'm sure this is right up Chris' alley.

from my charge controller to the batteries...i need to fuse for 75a.  was going to use a simple 100a siemens AC/DC safety switch disconnect, but the thing is HUGE (24"x 10").  same going from the batteries to the inverter.  will be a smaller inverter (for now), so 75a is what i need right now.

Chris, how exactly did you built that 200a disconnect?  i thought the QO breakers were rated at 70a max for DC?  or did you just use the QO enclosure and non-QO breaker?  any details that you can provide on that (enclosure part #, breaker #) would be greatly appreciated.  i have everything else figured out except these 2 larger DC disconnects.

thanks.

[roosaw]

As far as a mains disconnect you can get a 300 amp 3-way switch from West Marine (and others) it allows you to break the bank into 2 smaller ones in case you have a problem on one side without loosing total capability, allows you to combine the banks into one large one (prefered mode of operation) and allows you to turn both off.  this is a marine piece of equipment so I'm not sure of the max voltage but as long as you are not going too high where arching would become a problem 300 amps is 300 amps.  they also have plane old on-off switches.

[ChrisOlson]

Chris, how exactly did you built that 200a disconnect?  i thought the QO breakers were rated at 70a max for DC?

I don't know if it's up my alley or not.  But I called Schneider Electric when I did that.  The breaker I used was a 100 amp and it was rated for 100 amps DC but no more than 50 volts (I believe that was the max voltage).  The engineer told me it can be used with 24 volt, but not 48 volt because 48 volt exceeds the limit.

I "cheated" by using each pole of the breaker to carry 100 amps to the load.  The engineer told me this would work fine, but it is outside the UL listing for it because the enclosure was only rated for 100 amps total.  He said the proper way to do it was to use the breaker for only 100 amps and jumper the poles.

Again, it worked OK and did not exceed the rating of the breaker using each pole to carry 100 amps of the load.  It is just the UL listing requirement.  I did not care about the UL listing requirement.

I can get the part # off the breaker if you want.  But it is just a standard QO 2 pole 100 amp in an outdoor enclosure.
--
Chris

[defed]

As far as a mains disconnect you can get a 300 amp 3-way switch from West Marine (and others) it allows you to break the bank into 2 smaller ones in case you have a problem on one side without loosing total capability, allows you to combine the banks into one large one (prefered mode of operation) and allows you to turn both off.  this is a marine piece of equipment so I'm not sure of the max voltage but as long as you are not going too high where arching would become a problem 300 amps is 300 amps.  they also have plane old on-off switches.

i was looking at them, and some say that 32v UL listed....but i think i would prefer what Chris did.  just have to figure out exactly WHAT he did!

[defed]

Chris, how exactly did you built that 200a disconnect?  i thought the QO breakers were rated at 70a max for DC?

I don't know if it's up my alley or not.  But I called Schneider Electric when I did that.  The breaker I used was a 100 amp and it was rated for 100 amps DC but no more than 50 volts (I believe that was the max voltage).  The engineer told me it can be used with 24 volt, but not 48 volt because 48 volt exceeds the limit.

I "cheated" by using each pole of the breaker to carry 100 amps to the load.  The engineer told me this would work fine, but it is outside the UL listing for it because the enclosure was only rated for 100 amps total.  He said the proper way to do it was to use the breaker for only 100 amps and jumper the poles.

Again, it worked OK and did not exceed the rating of the breaker using each pole to carry 100 amps of the load.  It is just the UL listing requirement.  I did not care about the UL listing requirement.

I can get the part # off the breaker if you want.  But it is just a standard QO 2 pole 100 amp in an outdoor enclosure.
--
Chris

i only need a single pole, and 75a breaker, so i think i could do what you did w/o messing up the UL...which unfortunately i do care about somewhat.  i may grid tie some day so it will probably better if everything is labeled.

i guess i am just confused about what you did because i thought i read the spec sheet that QO's only went to 70a DC.  i will only be at 24v, so that is not a problem.  also, your box looks so simple, i don't recall seeing anything like that.  i mean, it looks like my fused disconnect except fuses go where your breaker is, with the neutral bar attached...i don't recall seeing a 'breaker' type.

[ChrisOlson]

i guess i am just confused about what you did because i thought i read the spec sheet that QO's only went to 70a DC.

I don't ever recall seeing any 70 amp limit.  Whatever the breaker is rated at for AC, it is also good for DC, the way I understood it.

At any rate, what I did is parallel the loading on the breaker poles.  A 2 pole breaker will handle 100 amps on either leg, and go over that on even one leg and it will trip it.  So your load is 200 amps.  You run one 4 gauge wire to one pole from the battery and another one to the other pole.  Then you run the load wires off the other side of the breaker to the load.  100 amps is carried on each wire, which in parallel is 200 amps to the load with a 100 amp 2 pole breaker.

That that was sticky part - the box enclosure was only listed for 100 amps.
--
Chris

[defed]

http://ecatalog.squared.com/pubs/Circuit%20Protection/Miniature%20Circuit%20Breakers/QO-QOB%20Circuit%20Breakers/0730CT9801R108.pdf

presuming the link works, page 4 under "voltage rating":

48vdc (10-70a for 1 and 2 pole circuit breakers, 10-60a for 3 pole circuit breakers).

then on page 5, there is a chart that seems to say the same thing.  to me, that says 70a is the limit, but i could be misunderstanding it.

[defed]

been doing more (more like non-stop) research on ways to do this, and i found plenty of breakers that will do what i want.  they are 'panel mount' breakers tho, and i am having some issues find an outdoor enclosure made to accept them.

from my understanding, panel mount breakers are secured thru their front w/ 2 screws and wiring is attached via 2 studs on the back.  seems like it should be a relatively simple thing to find an outdoor enclosure w/ an isolated bus bar...

[birdhouse]

*most* (square d, siemens, eaton, ect) panel mount breakers are just a friction fit.  there are two ears below the screw that holds the wire in place.  these hook to a thin "u" channel along side the bus bar.  then, the breaker has two metal spring loaded tabs that slide onto the buss bar to hold them there. 

some of the larger double pole breakers do have a screw right down the middle to hold them in place. 

if you're in the states, home depot should have a fused disconnect enclosure with a grounding bar.  they hold one double pole breaker.  they're pretty small too.  i think like 8" wide, 12" tall, and 3-4" deep.  large on off handle sticking out the right side of the box. 

isolated "neutral" buss kits are also really easy to add to a box and cost 10-12 bucks.

hope this helps!

adam

[kitestrings]

defed,

My comment dates back to your origninal diagram, and you may have this already done, but I prefer to rotate pairs of batteries in a string.  This way the connecting wires are a bit shorter and don't have to cross the tops (which can make cleaning a bit easier).

Regards,

~kitestrings

[defed]

*most* (square d, siemens, eaton, ect) panel mount breakers are just a friction fit.  there are two ears below the screw that holds the wire in place.  these hook to a thin "u" channel along side the bus bar.  then, the breaker has two metal spring loaded tabs that slide onto the buss bar to hold them there. 

some of the larger double pole breakers do have a screw right down the middle to hold them in place. 

if you're in the states, home depot should have a fused disconnect enclosure with a grounding bar.  they hold one double pole breaker.  they're pretty small too.  i think like 8" wide, 12" tall, and 3-4" deep.  large on off handle sticking out the right side of the box. 

isolated "neutral" buss kits are also really easy to add to a box and cost 10-12 bucks.

hope this helps!

adam

this is the type of breaker i was looking at:

http://solar-catalog.com/discon.html#Panel_%28Front%29_Mount_

the way i've seen them mounted, with screws thru the front, i figured the proper box for them would have rectangular knockout w/ holes pre-drilled.  perhaps i just use a regular breaker box and make my own holes.

[defed]

defed,

My comment dates back to your origninal diagram, and you may have this already done, but I prefer to rotate pairs of batteries in a string.  This way the connecting wires are a bit shorter and don't have to cross the tops (which can make cleaning a bit easier).

Regards,

~kitestrings

i think i did have the batts laid out both ways, and for some reason i decided on the "criss cross" method.  i don't remember why tho.

[kitestrings]

Electrically it is the same of course.  I've seen some creative solid bus bars that lend themselves better to your layout.

Depending on the dimensions it can be (minimally) shorter wires to flip pairs.  I've found it can help keep them out of the way of venting.  Here's ours (48V bank):

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~kitestrings