We’ve all turned the ignition on our cars only to hear nothing when we expect it to crank. Usually we hitch a ride to the auto parts store and grab a new battery and turn in the old one to eliminate the dreaded core charge which is mandated by our lovely government. Before you turn the battery in, let me offer you an alternative use for those old car batteries.
While restoring old car batteries will not necessarily make them useful in a car again, they can serve as very good batteries for a solar powered system. There have been circumstances where people have actually used them in their cars again for a long time, but most do not maintain a standing voltage above 12 volts, which is what is required. This conversion method isn’t always guaranteed to work because some batteries have been heavily sulfated or abused, therefore the lead plating inside the battery has broken into several pieces. You can usually tell this if the sides of the battery casing is bulged. If you buy high performance car batteries these are much better for this type of conversion because the lead plating is sturdier. Like anything else in life, you get what you pay for.
You can also check out your local auto parts store and ask if they have old batteries. They will sell them to you at the core charge. Look through their selection and pick one with a recent manufacturing date and preferably a premium battery.
Emptying the Acid
The next thing you want to do is to get the acid out of the battery. First get some protective clothing and eye-wear and some disposable gloves. Find a plastic tote or storage bin, remove the compartment covers on the battery and slowly turn the battery over inside the tote to avoid splashing. Wait 30-45 mins until it empties completely. You should be able to hear the acid trickling out if it’s not finished. Once it’s emptied, use distilled water (not tap water) and fill all six cell compartments. Empty the water out and repeat two more times.
Mixing the Alum
First purchase some alum. The one pound bag for $3 will work just fine for one battery. You can either boil tap water for 10 minutes or purchase distilled water and heat it up in a pot on the stove – then you want to pour the entire contents of the one pound bag into the heated water so it will dissolve. Mix it up with a spoon to make sure all the crystals have dissolved. Next, use a funnel so you can pour the alum water into the battery and fill all six cell compartments. Make sure you let it cool some first (especially if you boiled water) otherwise it will melt the funnel.
Using alum in the battery essentially makes it a lead alum battery or crystal battery. It’s no longer a lead acid battery. This means the discharge properties are much different. Lead acid batteries can be ruined by letting them discharge below 12 volts on multiple occasions. This isn’t the case with the lead alum batteries. While they will not stand at 12 volts, their properties allow them to be discharged all the way to zero without damaging them. The discharge pattern is also different. In a lead acid battery, the discharge crashes rather quickly whereas in a lead alum battery, the discharge rate is much slower. You will see that alum batteries do not have the amp capacity that a regular car battery would. The awesome thing about this is that you can keep adding batteries in parallel to form a large solar battery bank. Alum batteries will last you a very long time and require very little maintenance.
Charging the Battery
It’s better to charge these batteries initially with a slow charge. If you have a solar panel hook it up and allow it to charge over a few days, then put a load on the battery and discharge it completely. Old CPU fans or 12 volt lights work as good loads. Once it’s discharged, charge it again and repeat the process for a few weeks. This helps form the battery – the more you charge it, the better it gets over time.
I have a couple of these batteries in my garage that will run adequate lighting and will power and charge CB radios, walkie talkies, am/fm radios, cell phones any most other small electronic devices. If you get lucky and have quality batteries, you may even be able to run power inverters to power laptops and other items that require 110 volts.