Batteries don't seem to hold a charge

8 Posts
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.
 
65 Posts
Oct 28, 2011 01:18 pm
Re: Batteries don't seem to hold a charge

Hey Steven - the first thing that stands from what you wrote above is that the batteries were "brand new" from 2004 and never received a charge. When batteries are brand spanking new they should be very close to fully charged. Batteries not left with some trickle charge on them (at the very least) will self discharge at a rate of around 5-10% per month.

It sounds like years went by since these CAT batteries were last charged. As a result, I would estimate that these batteries were almost entirely discharged and most likely had been that way for some time. That's the death knell for any lead acid battery (i.e. being left fully discharged for nearly any length of time). In essence they were probably dead the day you bought them.

So it's not surprising that they can't hold a charge. Sadly your 100AH batteries have probably become so deteriorated by having been completely discharged that they're more like 1AH batteries.

Also, as you probably knew and realized, you really don't want to mix different batteries together (nor, if you can help it, batteries of the same model but of different ages). The reason is, especially when the batteries are in parallel, they will only work as well as your worst battery in that whole bank.... bringing all of your batteries down to the lowest common denominator.

hope that helps!

AltE
"Making Renewable Do-able" (tm)
http://www.altEstore.com/
« Last Edit: Oct 28, 2011 01:20 pm by Sascha Deri »
 
8 Posts
Oct 28, 2011 03:21 pm
Re: Batteries don't seem to hold a charge

Hey, thanks for the reply, I never gave it thought that there non-charge might have ment that they had just died...

Is it at all possible that they were made and shipped without a charge?

I didn't get these batteries the traditional way. I know that when you go to a store, new batteries are all charged and ready to go. But these batteries were made by CAT and shipped to a friend of mine's companies warehouse. The instruction was for the company (a hydraulics company) to do the finishing work on the CAT machines, and then charge and insert the batteries into them before shipping back to Caterpillar. Something came up, and the company accidentally got a double shipment of the batteries. They got 800 instead of 400. When they called CAT about the mistake, they were told to dispose of the batteries rather than ship them back. I'm not a part of the company, so I'm not 100% sure what happened, but somehow, they sat in the warehouse until my friend happened upon them, and talked with his boss to get about 60 of them. It saves the company money to not have to pay for disposal, so he agreed.
My friend just asked me how many I wanted, and I took 6 of them. So thankfully, if they are dead, I didn't pay a cent for them.

But is it possible in that situation, that CAT would make the batteries and not give them a charge at all? My friend (a hydraulics engineer, not an electrical engineer) assured me that CAT sent them completely uncharged so that they had an infinite shelf life. Could this be possible, or should I walk up and tell my friend that the pyramid of 54 batteries he has in his garage are just a waist of space?
 
65 Posts
Oct 31, 2011 02:11 pm
Re: Batteries don't seem to hold a charge

Is it at all possible that they were made and shipped without a charge?
 
But is it possible in that situation, that CAT would make the batteries and not give them a charge at all? My friend (a hydraulics engineer, not an electrical engineer) assured me that CAT sent them completely uncharged so that they had an infinite shelf life. Could this be possible, or should I walk up and tell my friend that the pyramid of 54 batteries he has in his garage are just a waist of space?

I'd say it's pretty unlikely at all they weren't made without a charge. My understanding of the manufacturing process is that inherently once they are made, they have a charge and from there on out if you don't keep them trickle charged they discharge over time.

The only exception I can think of is where the batteries would've been shipped without the electrolyte/acid, which I'm sure wasn't your case.

AltE
"Making Renewable Do-able" (tm)
http://www.altEstore.com/
 

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