Are my batteries dying?


So yes to get started here I am new to solar but have on and off studied it over the years. I jumped in head first 6 months ago and love it. I have pretty well just been experimenting to see what works.

I managed to acquire some 12v marine batteries from salvage and revive them to a pretty even balance. I am currently using 12 marine batteries that were paralleled but now are run in a 24volt series. They are charged with 4 renogy 100 watt panels also series and 4 Photowatt 50w panels in series.

Question is that on my Renogy Rover 40a CC once the sun goes down…the charge will read out between a 25.1 and a 25.5. I would assume this means my batteries are maintaining a charge but that charge is on the very low end of a life cycle. Is this correct?

also yes I am upgrading to 6 volt batteries just searching out what is best for that type of battery yet cost effective.


Hi Jarrod,
Remember when a battery is under any load then the voltage will drop according the load. Ie high loads could easily drop the voltage to 24.5V but it will return to a higher voltage once the load is removed.
If the battery voltage drops to 25.5V immediately after the sun goes down then either a small load is on or the batteries are simply old and not holding charge as well as new batteries. This just means the capacity of the battery is reduced but it may also indicate that one of the battery cells is faulty and drops voltage even under a small load.


If your Batteries are “Tired”, the likely cause is the dreaded sulphation. You have two options if that is he case. One, google “Sulfation circuit”. You will come across a circuit designed many years ago that back pulses a short sharp negative pulse into the battery. You will have to build this: which if you are hands on is not difficult. This pulse generated by the circuit, begins the gentle break down of the sulphation and will extend the life of flooded lead acid batteries for many more years. Up to 20 has been recorded for Lead Acid batteries. Depending upon how sulphated your batteries are or might be will determine the time to desuphate. One circuit per battery is a good way to go.
Two, get onto Ebay and search for “Battery Conditioner”. There are no end of people who have taken this circuit and made their own modifications or not and will sell you a conditioner. The likelihood is when you see the uncomplicated circuit and the price being charged by some, you might start thinking of learning Electronics 101, if that is the case!

If you are using “Gel” batteries, do not use this technique!!! The Gel will catalyse into a solid white mass and the battery will be literally stuffed.

Hope this helps