Author Topic: 48v Battery Bank Charge level  (Read 10583 times)

0 Members and 1 Guest are viewing this topic.

(unknown)

  • Guest
48v Battery Bank Charge level
« on: January 22, 2010, 03:46:26 PM »
I am planning to wire up 24 6V golf cart batteries in series and parallel to get 48V and 660 AHrs of storage.


When I set the charge controller what charge (V or A) would indicate full, time to dump, float, half full, and when to stop sucking the life out of my batteries.


Thanks...

« Last Edit: January 22, 2010, 03:46:26 PM by (unknown) »

ghurd

  • Super Hero Member Plus
  • *******
  • Posts: 8059
Re: 48v Battery Bank Charge level
« Reply #1 on: January 22, 2010, 04:44:14 PM »
Ginger or Mary Ann?

Blond/Brunette/Redhead?

T or A?  (tall or artistic)


Then naturally 'none of the above' because you should not have used 6V 220AH in the first place.


Most controllers use V.

Hard sulfation start below 6.1V.

G-

« Last Edit: January 22, 2010, 04:44:14 PM by ghurd »
www.ghurd.info<<<-----Information on my Controller

bob g

  • Hero Member
  • *****
  • Posts: 1107
  • 8.8kwatt idi diesel thermal conversion unit
    • microcogen.info
Re: 48v Battery Bank Charge level
« Reply #2 on: January 22, 2010, 05:58:46 PM »
for what its worth, i set my controller to 57.6 at 70 degree F ambient temperature

for bulk and absorption, and i would probably cut back to 55.2 to float.


ymmv

bob g

« Last Edit: January 22, 2010, 05:58:46 PM by bob g »
research and development of a S195 changfa based trigenerator, modified
large frame automotive alternators for high output/high efficiency project X alternator for 24, 48 and higher voltages, and related cogen components.
www.microcogen.info and a SOMRAD member

dnix71

  • SuperHero Member
  • ******
  • Posts: 2513
Re: 48v Battery Bank Charge level
« Reply #3 on: January 22, 2010, 07:04:06 PM »
Mary Anne.

"gingers" are fine, just not that one.

Tall and athletic would be nice, thanks.


But yeah, 8 six-volters in series is too many, you'll have a tough time equalizing a string that long.

« Last Edit: January 22, 2010, 07:04:06 PM by dnix71 »

Ungrounded Lightning Rod

  • SuperHero Member
  • ******
  • Posts: 2865
Re: 48v Battery Bank Charge level
« Reply #4 on: January 22, 2010, 07:36:50 PM »
Take the numbers for maintaining 12V batteries of the same technology (available all over the place) and multiply voltages by four.
« Last Edit: January 22, 2010, 07:36:50 PM by Ungrounded Lightning Rod »

southpaw

  • Full Member
  • ***
  • Posts: 103
Re: 48v Battery Bank Charge level
« Reply #5 on: January 23, 2010, 06:12:45 AM »
Hi

Are you saying you cant equalize a 48v battery bank as well as a 12 or 24v bank?


Why does it matter whether you have 8 3 cell batteries or 6 4 cell batteries


or 24 1 cell batteries in series, you still require 24 2v cells in series to


get 48v.


I can understand the difficulty in keeping 3 parallel banks in balance when


charging, equalizing and discharging, hence 1 bank of 660 ah cells would be


preferable.


Please help me understand the proper way to set up a 48v bank.


 

« Last Edit: January 23, 2010, 06:12:45 AM by southpaw »

Beowulf

  • Guest
Re: 48v Battery Bank Charge level
« Reply #6 on: January 23, 2010, 07:59:49 AM »
T or A?  Hmmmm tough question....I prefer Tits.


So a long string of batteries is bad?  Glad I couldn't get the 2V telco batteries I was looking for.  That would be a heck of string!  But think of the Amps I would have!


The batteries will probably be store in a 60 degree environment (a buried shipping container with vent) so I probably would want to raise the dump point a bit.


I guess I better pick up a battery book to fill in my knowledge gaps.  This was one of the reasons I thought I would start with golf cart batteries.  I figured if I screwed up I would not be out as much money as comparied to Trojan 105's or L-16's.  Kinda like training wheels.....


This is a great site for info.  The feed back I have been receiving is great.  Thanks all!  Any other insights are always welcome..........


The reason I was thinking Amps was that alot of need to know info comes from the energy production in a 48V genny is in the form of A's.  But in battery systems it is in V's that determine how full the batteries are.  Sometimes this electrical stuff get's confusing.......but I am learning.


Thanks!


 

« Last Edit: January 23, 2010, 07:59:49 AM by Beowulf »

ghurd

  • Super Hero Member Plus
  • *******
  • Posts: 8059
Re: 48v Battery Bank Charge level
« Reply #7 on: January 23, 2010, 08:52:16 AM »
I meant everybody has their own experiences and ideas about what is good.  Trying to sort it out is a headache.


I like 6V golf cart batteries, but 500W is pretty big for what I do.


I also like 14.4V per 12V.  And since the power I work with doesn't get them to 14.4V very long per day, I just leave it at 14.4V.

It's good enough for Morningstar's standard solar controllers set to flooded cells.

But Blue Sky's defaults are considerably lower, about 13.8V IIRC.

Others use 14.1V, etc...


If the big companies can't decide what is perfect... online info will be a mess to sort out.

G-

« Last Edit: January 23, 2010, 08:52:16 AM by ghurd »
www.ghurd.info<<<-----Information on my Controller

dnix71

  • SuperHero Member
  • ******
  • Posts: 2513
Re: 48v Battery Bank Charge level
« Reply #8 on: January 23, 2010, 09:58:26 AM »
The TelCos use 2v primary cells in series mainly for maintenance and balance. If one primary cell fails, it can be replaced, where with a 6v or 12v box if one primary cell fails inside the box you have to replace the whole box.


If you have used 6 volters of varying capacity, then a 48v string is okay. You know you're going to have some R and R to do and you will be swapping out when 1/3 go bad instead of 1/6.


But if you are buying a new matched set, there is a lot less wiring involved to properly balance 12 12v boxes (3 series strings of 4) than to balance 3 strings of 8 six volters.


12v-----12v-----12v-----12v

/           /            /          /

12v-----12v-----12v-----12v

/           /            /          /

12v-----12v-----12v-----12v


Those slashes between the 12v are balance bridges. If you used 6v batteries then you just doubled the set. Keeping all those connections clean and tight is no small matter, either.

« Last Edit: January 23, 2010, 09:58:26 AM by dnix71 »

Ronnn

  • Full Member
  • ***
  • Posts: 131
    • Myspase profile
Re: 48v Battery Bank Charge level
« Reply #9 on: January 23, 2010, 02:47:56 PM »
I like both my self and not too much of either.


But you question would be better answered by the battery manufacturer.  They often have different numbers from one  company to another but they shouldn't vary much more than a few tenths of a volt.


Ron

« Last Edit: January 23, 2010, 02:47:56 PM by Ronnn »

WineGuy

  • Newbie
  • *
  • Posts: 28
Re: 48v Battery Bank Charge level
« Reply #10 on: January 23, 2010, 05:25:29 PM »
Could you please elaborate on the "balance bridges"?

I'm not familiar with that term.


Thanks

« Last Edit: January 23, 2010, 05:25:29 PM by WineGuy »

wpowokal

  • Hero Member
  • *****
  • Posts: 1271
  • Country: au
  • Far North Queensland (FNQ) Australia
Re: 48v Battery Bank Charge level
« Reply #11 on: January 23, 2010, 09:30:57 PM »
It is simply a cross connection between common voltage points of parallel strings. That is in the diagram above all the positive ends of each string are presumably connected to a common point, so the positives of the next 12V batteries in the string are connected to each other and so on.


Not something I have done, I see difficulties isolating each string, you will/do have them independently isolate able  don't you. But would have the effect of keeping each 12v battery equal to it's mate.


I have run 8 strings of 2V cells @24V for a number of years, when a single cell fails the others in that string take up the extra volts while in the remaining strings they remain relatively equal, I just don't see the point in stressing all batteries should one cell/battery fail. As mine are now 21 years old I keep a good eye on them, at times not good enough though.


I'm not saying it's wrong just not to my taste.


allan

« Last Edit: January 23, 2010, 09:30:57 PM by wpowokal »
A gentleman is man who can disagree without being disagreeable.

dnix71

  • SuperHero Member
  • ******
  • Posts: 2513
Re: 48v Battery Bank Charge level
« Reply #12 on: January 23, 2010, 09:43:31 PM »
The bridges on the outside exist because you have wired series strings in parallel.

The three inside exist so if you need to tap out less than 48 volts you get a 3 parallel set instead of one. If you need to equalize with a regular 12v battery charger you can do three at a time instead of one.


This is a 12v series/parallel string to make 48v without internal connections between strings. You would bridge where the _ (underlines marks) are if you wished to allow for easier equalizing or multiple voltage tapping.


   1       2      3       4

   + - _ + - _ + - _ + -

   (                            )

   + - _ + - _ + - _ + -

   (                            )

   + - _ + - _ + - _ + -  

« Last Edit: January 23, 2010, 09:43:31 PM by dnix71 »

tecker

  • SuperHero Member
  • ******
  • Posts: 2183
Re: 48v Battery Bank Charge level
« Reply #13 on: January 24, 2010, 01:37:47 AM »
There's no substitute for pulse charging over a float charge at low cycle the charge you pick up is very fast  and the amperage is less at that time . Another method is to bring the batteries up slow and then add in 120 ac cap circuit to charge them over the top.
« Last Edit: January 24, 2010, 01:37:47 AM by tecker »

scoraigwind

  • Sr. Member
  • ****
  • Posts: 423
  • Country: gb
    • www.scoraigwind.co.uk
Re: 48v Battery Bank Charge level
« Reply #14 on: January 24, 2010, 05:23:06 AM »
If your charge controller supports 3 stages, bulk (with voltage rising), absorption at a set voltage, and float at a lower set voltage, then there will be two voltages to set.  In such cases I would set the first one (the one for the absorption charging has many names) quite high around 60 volts to make sure that the batteries do get a proper charge.  However the temperature here is not often 25 degrees - usually a bit lower.  


Most charge controllers have optional temperature sensors.  The best charging voltage changes by about one volt for every 8 degrees C or 14 degrees F(48 volt system).  So it ought to be about 3 volts higher at 0 deg. C than at 25 deg. C  You can make these changes yourself manually for different seasons or use a temperature sensor.


I like to choose quite a high voltage for charging so as to reduce or remove the need for equalising.  The controller will switch to floating the battery after a short while and you can set the float voltage at a much less stressful level such as 55 volts.


If you are using a lot of water then you can take the voltage setting down but if the batteries never need topping up then I suggest you need a higher voltage to get them properly charged.


You will find that people have very strong opinions about batteries but it's hard to find two people who agree.


On discharge the effects of temperature are opposite but more subtle.  A discharging battery will be at a lower voltage and I am personally trying to find a formula or even some hard data on this but have not managed.  I usually stop discharging at 47 volts, but its a strategic decision based on many factors.  I have a poll on my blog about it just now and it shows quite a spread of views.  See http://www.scoraigwind.blogspot.com

« Last Edit: January 24, 2010, 05:23:06 AM by scoraigwind »
Hugh Piggott scoraigwind.co.uk

domeguy

  • Newbie
  • *
  • Posts: 42
Re: 48v Battery Bank Charge level
« Reply #15 on: January 24, 2010, 06:30:16 PM »
I like your rule-of-thumb about setting the charging cut-off voltage based on water usage.  One of the things I've never understood was how to know the "true" battery voltage when the batteries are constantly being either charged or discharged.  My bulk cut-off voltage is now set to that recommended in the SW4024 manual.  I think I'll try raising them a little at a time until I begin to see water usage.  Naturally, I'll need to monitor water levels rather closely...


-Lee

« Last Edit: January 24, 2010, 06:30:16 PM by domeguy »

jclaudii

  • Newbie
  • *
  • Posts: 29
Re: 48v Battery Bank Charge level
« Reply #16 on: January 25, 2010, 02:09:24 PM »
Wouldn't a full battery have a specific gravity that you could check with a hydrometer?  The mfc's should have a number of what indicates full, 90%, 80, etc.  
« Last Edit: January 25, 2010, 02:09:24 PM by jclaudii »