Oct 28, 2011 12:30 pm
Batteries don't seem to hold a charge
Early this summer, I came across 6 Caterpillar Batteries. They are all 12v Deep Cell 100Ah 750ccA batteries.
I already had 4 Remy 6v Deep Cell 204Ah golf cart batteries, connected in series/parallel for a total bank of 12v 408Ah.
This summer, I also expanded my solar array from a single 17v 15w panel, to 6 17v 15w panels.
I understand that this array isn't nearly sufficient to charge even the small bank of 4 batteries that I had, but I only spend a week at the cabin and the batteries have all year to charge. The bank only ever has to run a few florescent bulbs in the cabin, so the system is sufficient for that.
Anyway, When I came across the 6 CAT batteries, I knew that they weren't really the correct batteries for a renewable bank, but that they should easily work for my situation of one or two weeks of use.
The batteries were brand new from 2004. They had never received a charge, so I assumed that they would still be like new. I had plenty of time to charge the batteries, so I charged them all with a digital 3 stage charger at 2A for over 50 hours a piece. Every battery seemed to receive a charge perfectly and they were all at a little over 14 volts when I pulled them off the charger. When I went to my cabin this year in early August, I attached the 6 batteries in parallel to the end leads of the 12v bank of 4 batteries that were already up there. Everything seemed to be OK, and the inverter read a steady 13.6v. I connected the charger to one end of the 6 batteries in parallel, and the very opposite end were the 4 battery bank becomes 12v. I also connected the inverter the same way to get equal charge and discharge across the entire bank.
I used the system for the next 2 weeks, and then left the cabin for the summer. When I left, I had the 6 panel array at an angle calculated for the winter months and the batteries were at about 11.9 v. The temperature if it helps, was about 90 degrees F on average.
I had some complications with where I left my boat this year, and was forced to drive back to the cabin and retrieve the boat just yesterday. While I was up there I checked the battery bank and was surprised to find that the system had dropped to 9.1volts. The average temperature now is about 35 degrees F.
Being incredibly low, I feared the batteries would freeze if I didn't do something. So the next day, I disconnected all 6 of the CAT batteries, and connected the system solely to the bank of 4. Immediately I got a reading of 12.6v and it climbed to 13.6v in about an hour.
Feeling good about the setup, I left the cabin and took the 6 batteries with me. Hoping that one of them was bad, and it was causing the system to drain. However, I tested the batteries this morning, and found that they where ALL between 9 and 10volts.
What I'm wondering is, is there something that i'm missing? Do I have to charge the batteries in some different way on the FIRST ever charge? Should I connect the batteries in some different way in my system? Anything else that you see that could be the cause of this problem?
I thank you in advance for any insight, it would be greatly appreciated. I am at a total loss.