Re: [pvusers] Batteries

["Robert Warren" <robertwarren@mail.com>]

 Chris,

 It is good that you tested your batteries before buying them, but even though your friend says they are still 100%, I don't believe it for a minute. I have seen too many batteries die after sitting uncharged for a yr to 1.5 yrs. The positive plates build sulphate crystals. They may take a charge, but the efficiency will be lower than the usual 80%. I strongly suggest you install either a Trace TM500 or an Emeter or any other type of sophitsicated battery monitor which has a shunt and truly measures amps in vs. amps out with some type of internal algorithym based on Puekaerts equation. Then you will know when your batteries are really down (it will have a simple percentage value, showing how much is left) and try to put a charge back on them or reduce your loads and not run them below 60% of their normal capacity.  You should be able to get a couple years out  of them that way, but if they were really new, you might have get 5.The Trace TM500 was ! formerly called the Trimetric meter, designed and sold by Ralph Hiesey of Bogart Engineering, and is one of the best meters available at a reasonable cost.

 Your PV array, at 900 watts will give you around  37.5 amps (900W/24V=37.5a) when the batteries are low, but as they start to gain charge, the controller will give you only about 20 amps. So even though it seems that 4 hours of charge would be enough (4hrs*37.5a=150amphrs), it really won't be. You will be shorting your batteries day by day, even when you have full sun for at least 4 hrs. So reduce your loads, or increase your PV, or better, get a tracker. The Zomeworks is the easiest to install and the most troublefree, even though it is only single axis.

You could get a better inverter than Exeltech. It has a remote off switch so you can switch things off at night to reduce standby losses.

. I live in London and don't sell any of the stuff I am recommending, so this is a fairly impartial view. I hope this helps.

Robert Warren,

 Senior engineer, Solar Century

http://www.solarcentury.co.uk

----- Original Message -----
From: csnake@attglobal.net
Date: Sat, 27 Apr 2002 01:10:18 -0400
To:
Subject: [pvusers] Batteries


Content-Type: text/html; charset="iso-8859-1"

Greetings solar siblings

I posted a question about finding used batteries a few months ago and I wanted to thank all those who responded and ask for some follow-up advice.

 I located through a friend a 3yr. old set of AGM batteries. They were unused and sat uncharged on some distributor's shelf.

They were charged and load tested by my friend with state of the art equipment - he is an engineer with a battery manufacturer-and they tested out at 100% capacity.

 Now for my ? The battery is 410 amp hrs. at 24volts . Problem is my load calculation for my system is approx. 133 amp hours/day

which makes this battery a wee bit small for my needs. My friend assures me that these are great deep cycle batteries and they can take the abuse. They were originally designed for deep cycle use but they worked so well for float use that most of these batteries were sold to telecoms and we know telecoms aren't buying much of anything these days.Anyway my investment in these batteries so far is goodwill and a little bit of sweat so I am not out if they quickly die.

   Other relevant info. I am planning on 12 SP-75 Siemen panels (900 watts) to charge this battery. I haven't decided on an inverter yet. I really like the Exeltech XP -1100 it is clean and big enough to power everything I have except a piggish air compressor I have-but the downside for it is the lack of sleep-mode and the 10watt constant draw.I am also considering the Statpower Prosine 1800 which is big enough even for my energy hog, sleep mode,  etc. but I have a bit of an anti-Xantrex bias.

 Back to the battery conundrum. one idea I had was to set up a small 12volt system to power things like answering machine, cordless phone charger, and a few lights. this could take some pressure of my 24v AGM batt. and provide some redundancy. On the other had do I really want 2 systems?

Thanks to anyone who makes it thru this long saga and  can laugh, cry or advise

 

Chris

 

 

 

 

What will we do if there is another fuel shortage? Did you know that there is a pollution free, completely renewable fuel which you can use right now in your own car? Don't replace the engine, replace the fuel. Check out my website on making your own fuel: http://running_on_alcohol.tripod.com Preview my new book, "25 years as a moonshiner" by Robert Warren robertwarren@mail.com

--

What will we do if there is another fuel shortage? 
Did you know that there is a pollution free, completely renewable fuel which you can use right now in your own car? 
Don't replace the engine, replace the fuel. Check out my website on making your own fuel: http://running_on_alcohol.tripod.com 
Preview my new book, "25 years as a moonshiner" 
by Robert Warren 
robertwarren@mail.com

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