It’s five o’clock in the afternoon and as soon as we got home I, as usual, check the status of our new solar power system.
To my dismay, the charge controllers are only showing that the batteries have a 11.9 volt charge or forty percent state of charge (SAC). They should never be discharged below fifty percent.
It appears as if the batteries are either not charging or they are not holding a charge. To find out, we’ll have to test them. It’s also overcast and when there are multiple possible causes, the fun begins.
When we bought the solar power system we learned a lot about deep-cycle batteries (their are other types you can use for solar) including the fact that you’re only supposed to discharge them no lower than fifty-percent. If you do, the battery won’t work as well the next time around and it’ll get worse the more times you over-discharge them.
So basically, when you buy one battery you’re buying one-half of a battery and you only get to use half of the amp hours listed on the label if you don’t want to ruin it.
Plan to buy twice as many batteries as you think you’ll need.
But wait, there’s more.
The batteries are where all of that free energy will be stored until you use it. If it isn’t set up properly, all of that sunshine is going somewhere besides your refrigerator. It’s a good idea to learn a little about them if you’re going solar.
Setting up a battery array can be confusing and the topic of batteries in general, is hotly debated in the online forums. Some issues you will have to deal with are:
- How to connect them correctly (there are many different configurations).
- How many solar panels at how many watts per panel will you need per battery to charge them each day?
- How many batteries will you need to meet your power needs?
- How to calculate how much power you’ll need.
- How to equalize the batteries in your array or does your controller do that for you?
- What is equalization?
- What type of battery is best and how much of it’s charge can you use to prevent rendering it useless?
- How to tell if it’s useless (one bad battery will compromise the performance of the rest)
Try browsing any forum looking for answers and you’ll find certain personality types:
- The guy with the overly scientific approach who posts mathematical formulas broken down into several categories depending on the type battery, panels, geographical location and whether or not you like peanuts.
- The guy who gets right to the point; “your batteries are dead, done, depleted, sulfated.”
- The poor newbie who dared ask a question without all of the information needed for the first guy to apply his scientific formulas.
Another thing we didn’t know about batteries is that they may be bad but appear to be good if you don’t test them the right way. A surface charge is the false reading a bad battery will have right after it’s fully charged – but it’s temporary. Make sure you test a battery at least four hours (preferably twenty-four), after it’s been fully charged in order to get an accurate result.
We’ve had batteries tested at stores that had a surface charge showing they were full that, when tested later, dropped volts – they were bad.
We’ll test our batteries and if they’re good, the problem lies elsewhere in the system.
Learn the basics about batteries before you buy a DIY solar power system. It’ll help you to not ruin them like we may have ours. Not everything is in the instruction manual.
And get a low-voltage-disconnect to protect them from over discharging. HUGE Industry-Wide Problems With Solar
Stories From Off The Grid. 