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cheap (I mean inexpensive) batteries

Started by bschwartz, November 16, 2010, 04:58:42 PM

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bschwartz

I'm setting up an Outback GVFX3648 grid tie inverter.  I don't plan on using all of it's capabilities such as battery backup.  I will however need a small battery bank for it to work properly feeding the grid with my DC input.

I need a 48v battery bank, but don't need a bunch of capacity, just enough for the inverter to be happy.

What does anyone suggest for a cost/value selection?
- Brett

Metro 6/1, ST-5 - sold :(
1982 300SD
1995 Suburban 6.5 TD
1994 Ford F-250 7.3 TD
1950s ? Oilwell (Witte) CD-12 (Behemoth), ST-12
What else can I run on WVO?
...Oh, and an old R-170

Tom Reed

I'd get 4 of the cheapest car batteries you can find. You can find them new for around $50. I would start with a matched set.
Ashwamegh 6/1 - ST5 @ just over 4000 hrs
ChangChi NM195
Witte BD Generator

Tom

LowGear

I'm building an electric ATV and plan on buying three "cheapski" size matching batteries just to adjust for size and the testing of everything.  The trojans are going to set me back about $200 each while the beginner set will be about that much for all three.

Just to digress a bit.  What is your DC source?  Have you ran this concept past the utilitity?  An engineer?  Outback?

Casey

Crofter

http://www.windsun.com/Batteries/Battery_FAQ.htm

I have been doing some research into the same thing. The above link gives lots of different scenarios and pros and cons to base a decision on. If you are not going to be drawing them down very far the 4 auto batteries is a quick and painless way of getting everything working but it is not much capacity and they wont last long if you are cycling them down deep and often. The next jump up in seriousness is to the golf car 6v deep cycle batteries but you need 8 of them. I just priced them today at a preliminary price in Canada of $188.00 each. That is about the minimum sized units used in most serious sized setups. If you want to go king of the road the Surrette 6cs25ps  1156ahr ones are $1575.00 a shot!
Frank


10-1 Jkson / ST-5

EBI-WPO

Sams Club in Tulsa had golf cart batteries for $69 this past Saturday. They had 3 pallets full, but were going quickly. Maybe not the best, but a decent start.

Terry
To have B.S. aimed at you is an insult to your intelligence......To have B.S. spread about you is an insult to your character.....Neither should be tolerated willingly.   EBI-WPO 2010

rcavictim

Tie your system to the phone line.  The telco keeps that alive with 48 VDC with a humongous battery plant at the central office.  In the lingo of the trade that is called 'talk battery'.  Likely not enough current available though to do what you need.
"There are more worlds than the one you can hold in your hand."   Albert Hosteen, Navajo spiritual elder and code-breaker,  X-Files TV Series.

mike90045

Quote from: Tom on November 16, 2010, 05:56:55 PM
I'd get 4 of the cheapest car batteries you can find. You can find them new for around $50. I would start with a matched set.

I'd say use regular "marine" batteries. They are not true deep cycle batteries, but they are made in mass, and costs are much less than true deep cycle, and will last longer than starting batteries.

mobile_bob

if the system design only calls for the batteries to be a buffer and the batteries will never see more than 5-10% used off the top of them, then the automotive battery can be the most effective and biggest bang for the buck,

the problem is the desire to deep cycle them will lead to rapid failure, often times in less than 50 cycles and sometimes much less.

if you can either automate the process to assure that they are never really cycled, or can discipline yourself then perhaps a car battery would be a good alternative.

car batteries last for years in very hostile conditions, hot underhood temps, often poorly charged, vibration and dirty,  but they hardly ever get cycled over about the top ten percent of capacity.

that ain't much to play with,  but it can be a large amount of power over a very short interval useful for starting heavy loads.

in a very shallow cycle situation, it might be that the car battery holds up better and longer than a true deep cycle that never gets an opportunity to get its electrolyte mixed well, stratifies and erodes the plates prematurely.  a good car battery can last 8 or more years under average conditions, and it might be a very expensive deep cycle that is warranted for 10 doesn't make it as far.

something to consider fwiw

bob g

Crofter

Quote from: rcavictim on November 16, 2010, 09:48:15 PM
Tie your system to the phone line.  The telco keeps that alive with 48 VDC with a humongous battery plant at the central office.  In the lingo of the trade that is called 'talk battery'.  Likely not enough current available though to do what you need.

Now that is just plain sneaky! They dont need to "tap" your phone line; they need to put a meter on it!  ;D
Frank


10-1 Jkson / ST-5

bschwartz

Is there anyone here with an outback that can answer a question that I haven't seen in all of my readings......?

When does the inverter decide to feed the grid, and how much does it pull to do so?

How does it know when I'm feeding my battery bank from the sun (or other source) and know when to stop drawing power?

The manuals don't even mention it.
- Brett

Metro 6/1, ST-5 - sold :(
1982 300SD
1995 Suburban 6.5 TD
1994 Ford F-250 7.3 TD
1950s ? Oilwell (Witte) CD-12 (Behemoth), ST-12
What else can I run on WVO?
...Oh, and an old R-170

mobile_bob

i don't know for sure,  however my bet is they use a setpoint on the dc buss to determine when and how much to feed the grid.

for instance if they use a setpoint of 12.9 volts or so, then the grid tie will technically not draw anything from the batteries, and only draw from the dc buss when the voltage exceeds 12.9 volts.

aside from that there is likely some programming to be done, or it does it on the fly, so that it samples then loads the buss lightly, resamples and if the dc buss still exceeds the setpoint then it loads the buss more, resamples rinse wash and repeat until it samples
and finds that the setpoint has been breached at which point it would reduce the loading on the buss to get back up over the setpoint
value.  this could all be done in milliseconds and there is likely some sort of algorithm they use to speed up the process.

thats how i would do it if i were them

bob g

mike90045

Quote from: bschwartz on November 17, 2010, 07:15:16 AM
Is there anyone here with an outback that can answer a question that I haven't seen in all of my readings......?

When does the inverter decide to feed the grid, and how much does it pull to do so?

How does it know when I'm feeding my battery bank from the sun (or other source) and know when to stop drawing power?

The manuals don't even mention it.

I think with outback, you need a HUB and a MATE to get into the menus.   XW's need a SCP (system control panel)  they don't let you just access your expensive box, you need more boxes to do that.  :-[

Tom Reed

I've got a couple of those inverters and Mike is correct you'll need at least a Mate for the programming interface. I don't think you'll need a hub unless you have more than 1 outback device. Although my system is off grid I've read that the sell feature is triggered by the dc buss voltage. The Mate also gives you access to the internal metering in the inverter so you can see how much you are selling too.
Ashwamegh 6/1 - ST5 @ just over 4000 hrs
ChangChi NM195
Witte BD Generator

Tom

bschwartz

Tom,  do they NEED to be programmed, or will it work with basic defaults.  It would really suck to need to spend another $500 just to make this thing do what it is supposed to do!!!
- Brett

Metro 6/1, ST-5 - sold :(
1982 300SD
1995 Suburban 6.5 TD
1994 Ford F-250 7.3 TD
1950s ? Oilwell (Witte) CD-12 (Behemoth), ST-12
What else can I run on WVO?
...Oh, and an old R-170

LowGear

Hi bschwartz,

QuoteJust to digress a bit.  What is your DC source?  Have you ran this concept past the utilitity?  An engineer?  Outback?

Casey

Casey