Author Topic: Number of Batteries  (Read 3064 times)

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aidanhydro

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Number of Batteries
« on: June 27, 2006, 06:41:41 PM »
Hi


Which would be better to do: Buy one 12v 100 amp hour sealed gel battery or get 6 x 12v 17 amp hour SLA batteries (102 amp total) and connect them in parallel? The way i see it - a large battery would take up less space and would be a little cheaper. Many batteries would allow for replacement of a single damaged cell with less costs.


Or is there more to it than that?  


Aidan

« Last Edit: June 27, 2006, 06:41:41 PM by (unknown) »

RogerAS

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Re: Number of Batteries
« Reply #1 on: June 27, 2006, 02:13:18 PM »
aidanhydro,


First of all what are you trying to do with this battery? Are you running an inverter with constant drain? So many questions! We need more info. Tell us what you are expecting the batteries to do.


I'm assuming you're using this in a renewable setting, putting something into the battery from somewhere amps wise, and drawing them (amps) as well.


Personally I would get the one big battery. Why? Cable and connectors alone becomes an issue with a bunch of batteries. More points of possible failure=more failures. I know, I have 12 6V flodded golf carts, and wish I had 24. I still have to keep an eye on all those points of failure.


If you're only gonna have 100 amp hrs I assume this isn't really a mission critical battery/power system. 100 amps may sound like a lot but it really isn't. Used very wisely it still ain't a lot of juice.


I say keep it simple, but remember that normally in an off-grid or heavily depended upon system, the battery is going to get a workout. Period! If this battery is going to be a standby, one getting a charge when it isn't used, it won't be as bad or if you don't cycle it too deeply or for too long. Low voltage states for extended periods of time are mortal enemies of the common flooded battery. Never let a flooded bat stil drained any longer than you have to.


Bigger batteries are like bigger aquariums. If the chemistry gets off a little the sheer volume of liquid dilutes the error. On the con side it takes more effort to equalize, if you don't run a desulphator. Also usually a large flooded bat will use proportionally more water by increased surface area vs a group of smaller bats. Bigger batteries usually have more space and or cell division material than small batteries. Short-out issues are reduced in bigger batteries, and the "dregs" that fall from plates has a deeper resevoir. Kepping that sludge away from the plates is good.


Bigger batteries have less sensitivity to thermal changes. Just like big dinosaurs were less responsive to change in temperature, big batteries take longer to heat up or cool down. Rapid temperature changes are not good for normal batteries, but I hear gels are less susucptable. We know the dinosaurs went the way of the 10 year old "Die-Hard", but it wasn't because of rapid temperature shock. All this is irrelavent if one protects those batteries from the elements to begin with.


If your charging system(s) goes down the bigger your battery bank (not size physical, real amp hrs) is all you'll care about. So however you choose, for whatever you're doing, I'd go with as many, and as well made, true deep cycle batteries as I could afford. In my mind the battery bank is the guts of the system. I'd also go with a big meaty battery, just 'cause they can take some abuse. Not that I wouldn't love to have 6 new glass jar 2V batteries like we saw here recently or anything.


uuuuummmmmm glass jar batteries..... uuuuuummmmmmm ( drool puddling on desktop ;~Ô ).


RogerAS

« Last Edit: June 27, 2006, 02:13:18 PM by RogerAS »

wind pirate

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Re: Number of Batteries
« Reply #2 on: June 27, 2006, 05:54:11 PM »
It really depends on what you are doing with them. If you want to maintain an off grid home, 100 AH won't do you much good. If you just want to keep a light available in a cabin, it will be fine.


A good "cheap" way to get started is to use golf cart batteries (6V x 74 AH). You can buy them new for about $50 each at Walmart or Sams club.


Here's a good resource right here on this site.


http://www.otherpower.com/otherpower_battery_compare.html


Hope that helps.


wind pirate

« Last Edit: June 27, 2006, 05:54:11 PM by wind pirate »

nothing to lose

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Re: Number of Batteries
« Reply #3 on: June 27, 2006, 07:53:13 PM »
I would get one large battery. Must be some reason the big guys love to get forklift batteries weighing 3/4 ton :)


Last time I bought a Wallmart 12V deepcycle it was 115 amphr and only $55 each, I have 3 of them. Still working good after a couple years but I don't consider them the best. I have lots of others also, mostly bought used and cheap, 12V and 6V ones.


I think 2 decent 6V used T105 golf cart batteries (if you can get them) would do you far better for less money than 6 x 12v 17 amp hour ones will.

« Last Edit: June 27, 2006, 07:53:13 PM by nothing to lose »

iFred

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Re: Number of Batteries
« Reply #4 on: June 28, 2006, 06:18:39 AM »


how much power do you need to store? how much power are you going to use?

« Last Edit: June 28, 2006, 06:18:39 AM by iFred »

ZooT

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Re: Number of Batteries
« Reply #5 on: June 28, 2006, 11:21:08 AM »


You can buy them new for about $50 each at Walmart or Sams club.(115 amp hour deep cycle battery)

I have one of these batteries sitting here

Yet I'm having a bit of a problem defining exactly where this battery fits into the Dan's battery comparison article.

The battery is advertised as being a "deep cycle" type and thus would it fit in as a golf cart battery (better) or as a RV/marine battery (not as good)?
« Last Edit: June 28, 2006, 11:21:08 AM by ZooT »

nothing to lose

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Re: Number of Batteries
« Reply #6 on: June 30, 2006, 05:03:19 AM »
"The battery is advertised as being a "deep cycle" type and thus would it fit in as a golf cart battery (better) or as a RV/marine battery (not as good)?"


In general I would say in between. I have 3 of the 12V 115 amp Wall mart deepcycles, of course I never took one apart yet to look inside nor a T105 golf cart type either :)

 I think we are getting into a Brand area on this. I certainly think Trojans are better than what Wal-mart sells, rather a 12V deepcycle or a golf cart 6V.

Trojans cost more and I am sure the quality is batter inside and they will last longer.

At Wal-mart the price is lower for either 12V or 6V deepcycles and I am pretty sure neither the golf carts or deepcycle would be as good.


Comparing a Wal-mart deep cycle 12V and a Wal-mart golf cart 6V, if made by the same company I would expect them to be close to the same quality on a price per amp basis.


I have used and abused mine various times various ways, they still work fine, but it was not a normal steady use. Sometimes lots of heavy loads then sat dead a few days, sometimes stored full charge for weeks or a month of no use. For a portable use where they needed moved (loaded unloaded) I preffered 3 of those 12V over 6 of the 6V.

Less batteries to move around and less cables to mess with.


For a permanant location like normal I would preffer 6V trojans T105 golfcart or better.

« Last Edit: June 30, 2006, 05:03:19 AM by nothing to lose »

ghurd

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Re: Number of Batteries
« Reply #7 on: June 30, 2006, 02:04:53 PM »
Either way, I don't believe I would use gel or SLA batteries for most purposes over 25AH.


"getting into a Brand area"

Several (6~8?) years ago, Trojan had a recall that included 'house stickered' batteries, including some of those sold at Wally-World & Sam's at the time.

Interesting?

Maybe it was ~110AH G27 batteries with a loose connection between the terminal and 1st plate?


Someone with access to terminal stamp codes could compare current Wally-World terminal stamps to current trojan stamps... Just for fun.

G-

« Last Edit: June 30, 2006, 02:04:53 PM by ghurd »
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nothing to lose

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Re: Number of Batteries
« Reply #8 on: July 04, 2006, 05:33:38 AM »
"Several (6~8?) years ago, Trojan had a recall that included 'house stickered' batteries, including some of those sold at Wally-World & Sam's at the time."


Hmm, I wonder if they were lower quality Trojans sold as house brands? Even if manufactured by Trojan they may not be T105 quality. Yes, Interesting though.

« Last Edit: July 04, 2006, 05:33:38 AM by nothing to lose »

Clifford

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Re: Number of Batteries
« Reply #9 on: July 05, 2006, 07:59:20 PM »
I've got 4 - Wallmart Deep Cycle Batts and am having some "issues", although I think I'm finally getting them back into shape ....


I'm currently looking for some 2V batts to add to my set.


Anyway, a few things to consider:



  • "Golfcart" batteries are supposed to have somewhat thicker plates and are made for a bit more abuse than standard Deep Cycle Batteries.  I haven't confirmed this, and in reality, you may not know the truth for 5 years.
  • Multiple batteries allow flexabilities in configurations (6V, 12V, 18V, 24V, 36V, 48V, etc) (good if you are still experimenting).
  • Consider "half tapping" and similar configurations.  For example, you can "half tap" a string of 6V batteries to give you 12V for your inverters and lights, and 6V that some radios may require without using any transformers or power converters.  You could half tap strings of 2 Volt batteries to give you 2V, 4V, 6V, 8V, 10V, 12V, 14V, 16V, 18V, etc.
  • If you "kill" one cell in one battery in parallel with others, then you will "kill" one cell in all of the batteries.  In my case, in each of my batteries, I have 5 cells that put out 2.1V (or so), and one cell that puts out < 0.5 V.
  • In a low amp system, you may not have the power to equalize an "Industrial" battery.  Whereas you may be able to dump all your power into a single battery to bring it's power up sufficiently to equalize it.
  • If you have 2V batteries...  it is much easier to isolate "problem cells" for rejuvination.  Currently, I have to "equalize" all the cells in my 12V batteries.  Thus, I have 5 cells that are boiling away so that a single cell can absorb energy.
  • There is supposed to be an intrinsic power loss of batteries.  If you undersize your batteries, you will be deep cycling your batteries too much....  If you oversize your batteries, you may be just making up for the intrinsic power loss.
  • If you are trickle charging a battery bank, then a large inverter may suck down the voltage on your 12V system enough that it may transiently drop below your low voltage cuttoff when doing a high amp power drain (of course, this may be in part due to my having some weak cells).  This is something that I'm fighting with...  matching my high voltage cutoff, and low voltage cutoff, and power drain, and realizing, of course, that there is a reason for the high and low voltage cutoffs.  Thus, I'm wanting to experiment running at 14V.
  • All batteries last longer with "shallow cycles" than "deep cycles".  However, it is unclear if the "cost" is actually less.  For example, if you repeatedly deep cycle a single battery, it might only last 1 year.  However, if you "shallow cycle" 4 batteries in parallel, they might last for 4 years.  Thus you have a net gain of ZERO (and Wallmart might even give you a replacement if you bring in the dead battery after a year).


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Oh,

I just saw a new article posted on the Homepower Board about batteries.  It is worth reviewing.


http://www.homepower.com/files/featured/HP114_pg54_Dankoff.pdf

« Last Edit: July 05, 2006, 07:59:20 PM by Clifford »