Number of battery strings

[Jedon]

I was planning on having a bank consisting of 5 strings of 8 6v golf batteries for a 48V system. I was reading an article in Home Power that said more than 2-3 strings can cause equalization issues.

Thanks!

-Jedon

[dnix71]

Thats a lot of batteries. I'm jealous.  I don't know how you would equalize 8 batteries in series, let alone 5 banks of 8. How many amp-hours are these rated for?

It sounds like you could run a whole house including a/c on that. Or an electric vehicle. I'm guessing you plan to use it for your ride. What's the range (miles)?

[bob g]

i think it could be done effectively if you could divide the strings for charging.

but i don't know what you are using to charge with? genset? windgen? hydro?

i imagine each would have its own seperate concerns and how best to do it.

perhaps you could charge the whole lot together and only divide the strings for equalization periodically, that might be more practical.

there was a guy on ebay that sold some monster dc contactor/relays with 48volt coils

and 300amp capacity a while back, all new take outs made by prestolite.

the priceing was very good in my opinion, i got 4 of them in 24volt coil configurations for my system.

your probably going to need to divide the strings for charging  and certainly for equalization in my opinion.

bob g

[wpowokal]

I have 9 strings of 2V cells in my system and when they are all in service they receive no special care. Checks on charge currents to each string show very litle descripancy.

They are 20 years old I obtained them at age 13.

I would concider two strings normal, in my opinion the main difficulty of so many batteries is the time required for maintaining them.

So if you need 3 strings go for it.

allan down under

[scottsAI]

Jedon,

Beware of perfection. People get hung up on often ridiculous ideals.

If the impedance of each string is equal then the number of strings does not matter.

Key words "impedance of each string is equal".

Again beware of perfection. I used bus bar to connect my batteries together, much lower impedance than the battery. Not a worry.

Some might suggest to connect the middle of the strings together, not sure I would do it. I would start out without, measure it over a period of time, if they were different then might tie them together.

Have fun,

Scott.

[electronbaby]

I would make sure all the cell interconnects are the same resistance (AKA the same length) and that you make sure to feed off opposite ends of the bank. This will make sure to equally distribute your charging current across all strings evenly. Aside from that, scottsAI gives good advice regarding the impedance of each string being equal. This is important.

[Jedon]

Thank you all,

I'm planning on using this to power my house, 13KWh/day.

Initial power will come from 8 Kyocera 205W PV panels, then about 240W of hydro, then some wind.

For charging them I'll use something like a Outback MX60 and add another one as I need for wind.

I am building a 12x16 shed with a slab floor to store all this stuff, I was planning on putting the batteries on industrial shelves, I was thinking one string per shelf.

So what then would I connect the batteries together with? Some thick cable like 0/2 or something?

Then something as big as possible? ( bars woudn't work between shelf levels I guess )