RE: [pvusers] Fw: Advice on finding Used batteries?

[Michael Welch <michael.welch@homepower.com>]

Purcell, Mike wrote at 02:07 PM 01/02/2002 -0700:
  
>I would be wary of spending money on used batteries. Without the knowledge and equipment to test them, it can be a real crapshoot. If they offer them to you for free, that would be a slightly different story. But either way, if you are off grid, batteries are the backbone of your system. Take them seriously and treat them well. If you need to skimp, skimp on production. It is easier to expand production than battery banks.

Hi Mike. For the most part, I agree with you. But I want to make 2 points.
1. Most batteries that come from Telcos, and other folks needing high capacity backup, are kept in float service. That means they are hardly ever exercised, and can be a great bargain. But, those batteries are also often physically designed to be kept in float service, which makes them a bit less than ideal for us RE folks that want to cycle our batteries deeply and often.

That said, I got my battery bank almost 10 years ago as it was being retired from a hospital's telephone system backup. It came with some great racks and 2 incredibly heavy duty chargers. I traded for a right angle grinder that the hospital maintenance crew wanted. This battery was meant to be in float service. So if they get used a bit, I immediately get a lower voltage than normal RE system batteries would see. Fortunately, once the voltage depresses a little, it does not depress much more as I take more amp hours out. 

The biggest problem that I have is that they are hard to charge with my generator and the charger in my inverter. Because of the physical makeup of the batteries, the voltage comes up very quickly, and that makes my charger cut back. These batteries are almost impossible to equalize with my generator/charger combo as the voltage skyrockets when the batteries are full and they are under charge.

2. The "more batteries are better" concept only works up to a point. If you get too many, the self-discharge rate of the batteries can be more than your PV can provide. That means that you will be regularly running the generator to keep up, even when you are NOT USING ANY ENERGY in your household.
  
Michael Welch
  
------------------------
"The only nuke plant we need is already 93 million miles away."
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Michael Welch, michael.welch@homepower.com www.homepower.com
     Managing Editor, Home Power magazine
     Office Coordinator, Redwood Alliance
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