In the third part of our deep cycle battery series, you will learn which batteries were selected for a new smaller set of batteries to be restored if possible. Initial performance of the new setup is discussed and a video of the process is presented. You may want to see the previous article, deep cycle batteries [2] retirement data, to see how bad the initial battery bank was.
To recap, I’m on a mission to save money, and try to add some new life to my worn out, off grid battery bank. The initial array had 12 batteries, and 5 had to be removed. Here is a video of the process, and a few tips:
I selected the batteries numbered 2 and 3 because all the cells were functioning with one good cell in each. I also selected batteries #8 and #10 because they had identical measurements indicating they were above 75%.
Our Deep Cycle Battery Data
Of the 7 batteries not removed, we have a 4 battery bank to work on reconditioning, #2, #3, #8, and #10. Finally, I’ve set batteries #6 and #12 aside to add soon as the other 4 are ready. These two appear good, and we don’t want to drag them down with the weaker ones until they’ve been treated.
New Setup – 4 better than 12
Instant good news with this small array: It works better than all 12 batteries did before! The old setup would go from fully charged, 14V to 10V and inverter shutoff in less than 10 hours. Many mornings we wake up with the inverter beeping and no power. My trimetric battery monitor would indicate that 130Amp-Hours were used. That’s a pitifully poor showing for the once mighty array that boasted a good 1000AH of storage.
This morning it was different, quiet and peaceful. I ran things until about about 11am when the 10.8V beep went off making espresso briefly. Without the espresso load, the voltage was at 11.5V. I decided to run the generator when this battery bank was 67% discharged, or at about 230AH.
I look forward to restoring these 4 batteries however much possible, and then expanding the array with the two additional ‘good’ batteries. Sure glad I took the time to look into this old, “in need of replacement” battery array before spending more!
In this situation, I found that so far, less is more, when it comes to worn out deep cycle batteries. Have you ever found “less is more” in other areas of life? Getting closer to your off grid move? Tell us in the comments below!
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Large commercial installations have for years been built up using individual 2V cells. And in most cases they are using voltages greater than 12V for several good reasons. The first reason is greater efficiencies due to lower system losses in the wiring. Secondly if one cell goes bad, you can easily jumper out the single bad cell in a pinch until you can get a replacement cell. We have all heard the advice that adding new batteries to old is bad practice. This primarily true when talking about placing batteries in parallel.
Adding once 2V cell into a series string is less noticable because the charging current must pass through the entire series string thus ensuring a equal charge goes into each cell. When you place several cells in parallel, a weak cell will simply stop accepting current but the current will continue to flow through the other parallel cells.
When you have one bad cell in a 6 volt battery you end up having to remove the two good cells as well. If you had built up the bank with individual 2V cells you would only have to remove the one defective cell. Because the battery bank is one series string it will be less prone to premature failure due to unequal charge current flow in several parallel strings of 12V batteries.
Traction batteries for floor polishers, golf carts and even fork lifts are composed of individual 2V cells each having as much as 800 or 1000 amp hours capacity. When these are assembled into 24 V or 48 V banks they store a tremendous amount of watt hours.