Trying Off-Grid Solar Again, Looking for Guidance...

matchstc · July 2010

[Note: Moved from this thread to new thread here. -Bill B.]

Very New Guy here

Been off Grid , made all the mistakes and now trying to go off grid again
. New bank will be 16 L-16 HC's (48 volts)and i've read thru this Thread and understand the way to go is with Bus Bars and a fuse on EACH Positive terminal (so 16 in all?)

I have the technical skill to make the plywood,lexan, copper buss bar and understand I need equal length cable from each terminal to the buss bar and then equal length cables to the inverter (taped at least, twisted if possible)

I intend to order a lug setter this week from our hosts (on sale btw)

Currently I have a more traditionally wired set of T105's with the addition of crosswiring.

Can someone explain this simply for my fuddled mind or any relevant threads or webpages

thanks
mike

20 blem evergreeens, xantrex 60/48, xantrex charge controller and central control

matchstc · July 2010

Re: Re doing the Battery Box

One thing that is blowing my mind is all 16 l-16's positive terminals would go to one buss bar and ditto with the negative.

is this correct?

and then with the charge controller and inverter positive and negative going to the same bars.

matchstc · July 2010

Re: Re doing the Battery Box

icarus wrote: »

If you are going to put all the positives together on one bus bar, and all the negs together, you are going to have a 16 cell 6 volt battery!

If you are going to 48 vdc you are going to need to string 8 L-16s together in series (+to -to+ to - etc) and then connect that to a second identical string, making 2 48 vdc series/ parallel batteries.

Tony

Thats what I though then links like this confuse the issue. Right now I'm thing example 3 times 2.

crosswiring itself blew my mind!

thanks
mike:p

BB. · July 2010

Re: Re doing the Battery Box

matchstc wrote: »

Very New Guy here

Been off Grid , made all the mistakes and now trying to go off grid again
. New bank will be 16 L-16 HC's (48 volts)and i've read thru this Thread and understand the way to go is with Bus Bars and a fuse on EACH Positive terminal (so 16 in all?)

No--If I understand you correctly...

L-16 HC (at least from Trojan) are 6 volt batteries and you need 8 of them in series to make 48 volts. And you have 16--so that is two parallel strings.

So, at best you would need two series fuses--one for each series string.

Depending on the rated amperage you want from your system, you may have to go with a larger fuse holder to meet the current rating.

Those BlueSea bolt on fuse holders are rated for 30-300 amp fuses.

The BlueSea "T" holders are rated for up to 400 amps maximum.

You may use the "300 amp" holders for the batteries, and the 400 amp for going to your inverter (if you are looking at ~16,000 watt inverters on your 48 volt system) or the appropriate sized fuse holder for each of the cables/wires leaving the + buss bar common point.

If you ever want/need to isolate a battery bank -- You might look at this 350 amp A+B/A/B/Off switch (made for boats). Could be a nice fit for your system.

I have the technical skill to make the plywood,lexan, copper buss bar and understand I need equal length cable from each terminal to the buss bar and then equal length cables to the inverter (taped at least, twisted if possible)

To be clear--we are typing about "matched" cable lengths between your two parallel battery banks to balance (sharing) current between the two banks... If you have a 3 foot positive cable and a 6 foot negative cable, that is OK as long as Bank A and B both have a 3 foot and 6 foot cable in each of their strings (i.e., same resistance for wiring from +bus to battery to -bus).

For inverters, it is a good idea to keep +/- runs in parallel. Cross wires at 90 degrees (to avoid "cross talk").

I intend to order a lug setter this week from our hosts (on sale btw)

Currently I have a more traditionally wired set of T105's with the addition of crosswiring.

Can someone explain this simply for my fuddled mind or any relevant threads or webpages

Do you have other specific questions?

If you wish a more detailed discussion, I can move these posts to your own thread to keep things focused on your issues.

-Bill

By the way, if you are looking for large AMP*Hour capacity--Trojan and others have made 4 and 2 volt cells that are still manageble by one or two people--like this one:

Trojan L16RE-2V 1110 AH 2-Volt Deep Cycle Battery

I try to avoid going over 3 parallel strings vs 1 string of large capacity cells (3x the number of cells to water, 3x the wiring, 3x the fuses, 3x the connections, etc.)...

So, I really like the idea of this single cell batteries for high amperage strings.

matchstc · July 2010

Re: Re doing the Battery Box

BB. wrote: »

No--If I understand you correctly...

L-16 HC (at least from Trojan) are 6 volt batteries and you need 8 of them in series to make 48 volts. And you have 16--so that is two parallel strings.

So, at best you would need two series fuses--one for each series string.

Depending on the rated amperage you want from your system, you may have to go with a larger fuse holder to meet the current rating.

Okay so make up the 2 48 strings keeping the cabling as common as possible THEN Fuse the positive link to the buss bar so only two fuses

Those BlueSea bolt on fuse holders are rated for 30-300 amp fuses.

The BlueSea "T" holders are rated for up to 400 amps maximum.

You may use the "300 amp" holders for the batteries, and the 400 amp for going to your inverter (if you are looking at ~16,000 watt inverters on your 48 volt system) or the appropriate sized fuse holder for each of the cables/wires leaving the + buss bar common point.

Thank You these look great does our host carry them?

If you ever want/need to isolate a battery bank -- You might look at this 350 amp A+B/A/B/Off switch (made for boats). Could be a nice fit for your system.

A Possibility

To be clear--we are typing about "matched" cable lengths between your two parallel battery banks to balance (sharing) current between the two banks... If you have a 3 foot positive cable and a 6 foot negative cable, that is OK as long as Bank A and B both have a 3 foot and 6 foot cable in each of their strings (i.e., same resistance for wiring from +bus to battery to -bus).

For inverters, it is a good idea to keep +/- runs in parallel. Cross wires at 90 degrees (to avoid "cross talk").

And to keep those lengths the same also ((which entails replacing an expensive cable)

Do you have other specific questions?

If you wish a more detailed discussion, I can move these posts to your own thread to keep things focused on your issues.

-Bill

That might be a good idea thank you for the help

mike

BB. · July 2010

Re: Trying Off-Grid Solar Again, Looking for Guidance...

Mike,

Feel free to talk all about your system plans here.

-Bill

matchstc · July 2010

Re: Trying Off-Grid Solar Again, Looking for Guidance...

okay handful of new questions mostly battery and fusing related.

I have a xantrex 6048

currently I have 4/0 welding cable to it. Do I need to provide for the possible surge (12K I Think) IS 4/0 and a 300 watt breaker overkill for it? (I need to replace the cable anyway ) Also does the battery cable need a fuse AND a breaker?

IF I use 4/0 to my inverter do all my battery interconnect cables need to be 4/0 also? or would say #1 be sufficient?

IF I need to use the mega cable where can I find a buss bar big enough?

The bank will be two runs of L16 HC wired in series to get 48 volts, then wired toa set of central bus bars. The battery runs will need a fuse on each positive terminal..again how large 300 amps?

The forums here have been such an aid I'm up to page 56 on the beginner forum and then off to the next.

thanks
mike

mikeo · July 2010

Re: Trying Off-Grid Solar Again, Looking for Guidance...

Thanks for all the answers, to clarify the Evergreen panels are 12V X 5 in series to yield 60V, 2 strings into the combiner for 120V into the MX60.

I would keep the 4/0 to the inverters and use 4/0 jumpers to series each battery. You really don't need a battery fuse if you are within 2 or 3 ft of your inverter breaker and protect the wiring from the battery box to the breaker enclosure. A 250 amp breaker would be sufficient for the 6048 inverter surge. I would take the neg lead to the system ground lug, or 500 amp shunt if you have one and the pos lead from the opposite bank to better keep the battery's balanced. If you have more then 3 banks of batteries, then the buss bars would be warranted

solorone · July 2010

Re: Trying Off-Grid Solar Again, Looking for Guidance...

I don't think we paid too much attention to equal length battery cables decades ago.

I hesitate to measure mine, knowing they are not equal.

Could someone point me to a good read about this, I need to see if a fix is worth the effort at this late stage in my current battery banks life cycle. All my many books have been packed away, wife laid claim to my tool/library/hideout room.

In cleaning up this week, I found an abundance of 4 ought stranded and hard wire and #1 wire. Maybe the finding the 4 Ought was a sign:D

BB. · July 2010

Re: Trying Off-Grid Solar Again, Looking for Guidance...

Here is one web page that we commonly recommend here:

www.smartgauge.co.uk/batt_con.html

-Bill

niel · July 2010

Re: Trying Off-Grid Solar Again, Looking for Guidance...

you might try a quick determination by allowing the batteries to rest for several hours and measure the voltages of each battery (noting here than specific gravity may also be substituted as what is measured if it is accurate). if they are in parallel you may need to disconnect them at the beginning of the rest period as it will eventually try to equal out. it does not have to be off of a charge to do this and it may even show up better after it had been loaded down. make note of what batteries are where and what their voltages are. if they should have variations in voltages, even slightly, this is a sign of them being unequal. you could place lower reading batteries where higher reading batteries were. this is also why eqing became necessary as it is an overcharge to the batteries that are good and a final charge to those that are shy to bring them up to the same point. overcharging expels more water from a battery and increases maintenance.
so you may ask why not just eq all of the time or just rearrange them often? you could, but in the meantime some of the batteries will charge and discharge better than others and the ones doing just that are used heavier and cycled more than the others and will likely die first. of course this is the black and white scenario of either perfectly equal or very unequal, but there are varying degrees in between and it will never technically be perfectly equal. now if you have the wire to a battery as being 1ft in length and another battery at 1.5ft then it is advisable to rework them to be equal even if it means upping the 1ft wires to 1.5ft.
i can't say for certain at some point it will be necessary to rework the wiring to be equal as differences in connectors and how well they were put on can vary, plus it is what one may consider acceptable for you may eq once every month rather than once every 2 months. i think you follow me in the gist of what i'm trying to say or at least i hope you do.

Trying Off-Grid Solar Again, Looking for Guidance...

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