Thursday, May 27, 2010

Plan B

This morning I implemented Plan B.

I installed the batteries for our photovoltaic system six years ago. I've tried to take good care of the system and hoped to get more than six years out of the batteries. The typical lifespan of the batteries is three to five years so I'm already ahead.

Three weeks ago the batteries failed to fill on a day with plenty of wind and sun. I checked the system, equalized the batteries and topped them off with distilled water. The next two days they filled but just barely and failed to recharge fully each day for the next few days. Yesterday they filled but I noticed the low voltage reading was an unheard of 20 volts. I reset the memory and checked it again this morning -- 18 volts. I had a problem. I easily identified the battery that failed.

It's not wise to replace one battery in an array. The older batteries will significantly shorten the life of the one new battery. The best choice is to replace all sixteen batteries. I paid $65 each in 2004. The current price for the same battery is $140 to $153. To replace 16 batteries will cost approximately $2,600. That's $1,400 more than I paid six years ago.

This is were Plan B begins. Since I have a 24 volt system I need multiples of 4. I removed the bad battery and 3 good batteries leaving an array of 12. I can easily function with this number but won't have the extra capacity for extended cloudy periods which won't be a real problem. I'll take care of the 3 good batteries and keep them charged. When another battery fails I'll replace it with one of the 3. I can repeat this process twice more until I have 12 good and 4 bad batteries. When the fifth battery fails I can replace all the batteries or drop to an array of 8 depending on my experience with 12. I'll balance this plan with the cost of fuel to recharge the smaller array during cloudy periods.

Plan B is not just an attempt to save money. It's a reaction to discarding 15 good batteries prematurely just because one battery failed. That is irresponsible in my value system.

I'll work Plan B until it's time for Plan C. I refuse to pay $2,600 for a set of batteries.


Blogger Tim Hodgens said...


I like that. Who says that everything has to be top of the line and bomb proof all the time.

I heard a story about how in Michigan (?) last year they decided to repair the more rural roads in a way that they worked well enough.

Well enough is well enough. Heck it's good enough for government work, isn't it?


5/28/2010 04:41:00 AM  
Blogger Paul said...

Tim, when I thought about writing this post I thought of the concept of the best. Somehow we've learned we need the best. I suspect marketing has influenced us but there is a downside.

From what I've read some retailers are removing items from shelves because shoppers can't decide which item is the best? Customers are not making a choice in fear of not making the right choice for the best and thus make no purchase.

I like the concept of good enough. It leaves time, energy and resources for the important things.

5/28/2010 06:46:00 AM  
Blogger Alex Pendragon said...

Might be a good time to investigate state-of-the-art and see if there are now much more efficeint lithium systems that could last longer or give you what you need with less. It might even save you money over the old lead-acid tech.

5/28/2010 05:31:00 PM  

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