If you’ve got an off-grid solar system with one or more solar batteries, you may find that solar batteries appear to be draining quickly, in some cases overnight.
Could it be that the batteries are damaged?
What causes this and what should you do to not only troubleshoot this but fix it too?
This post explains why solar batteries may be draining quickly and what you may be able to do to get them working again.
What Causes Solar Batteries to Discharge Quickly (+Solutions)
If the batteries in your solar system appear to be discharging faster than usual, check that:
1. The Solar Batteries are being charged fully. The batteries may only be partially charged because:
- The days are mostly cloudy, overcast and there’s not enough sunshine to keep the batteries charged, Or
- The solar panels are shaded, and covered with dust or there’s another obstruction casting shadows on the panels
The end result is that when batteries are only partially charged, they appear to drain faster and one may be mistaken in thinking that they’re damaged yet in actual fact it’s because they are not charging fully anymore!
What to Do
- Check that the charge controller is set to charge the battery type – AGM, LiFeP04, or GEL that’s used in your solar system. The battery may not be charging properly because the wrong settings are used!
- Check that there are no shadows or dust covering the solar panels. Inspect the solar panels from time to time. Clean them should there be any buildup of dust to keep them working efficiently.
- Consider increasing the size of your solar panels to make up for the drop in energy produced during winter.
2. There are no appliances draining the battery power. It could be that there’s an appliance that’s switched on and continues draining the battery without you being aware.
Does the inverter remain switched off too when there’re no appliances running?
Some inverters draw a considerable amount of power even when no appliance is switched on!
In fact, you’d be surprised that an inverter with a no-load power draw of about 10 watts can use up as much power as you’ll have in a typical 60 Ah car battery over 3 days!
On the other hand, a good quality inverter that has an energy-saving mode when on standby can draw as little as 5W or about 40 mA at 12V.
You might also be interested in the article: How much power an inverter draw on no load
Tips to check for power draw by appliances
Measure the current drawn by the inverter from the battery using a clamp on the power meter.
Compare the power draw with the no-load power draw of the inverter.
You may have to switch off the inverter if it has a considerable no-load power draw and or switch any appliances that may still be ON.
Do this first before you condemn the batteries!
3. Have you increased the number of appliances connected to the batteries or increased the power draw on the solar batteries?
Perhaps the space heater is running longer than usual? Or, there’s a new member of the household who may be responsible for the additional energy draw?
One tip that has worked for me is to keep a record of how much energy is generated by the solar panels daily and how much is used up by the appliances.
If your off-grid solar system can automatically log or record this data then fine.
This way you can always note a change in the power generated or drawn from the batteries.
The point is, you can easily go back and check if there’ve been any major changes to the energy use that may explain why the batteries are discharging quickly!
4. Solar batteries may be damaged or failing. Batteries don’t last forever.
In fact, they can fail prematurely too if they’re deeply discharged often or left partially discharged for a long time.
As a rough guide, it is not uncommon for AGM batteries to last for 3-4 years and LiFeP04 to last for 5+ years.
Note though that there’re many variables that determine how long the solar batteries last from the quality of batteries installed, and whether they are charged or discharged as recommended by the manufacturer.
What to Do
Probably the surest test to perform is a charge them fully and conduct a capacity test. Perhaps there’s a qualified technician who can support you.
You’d need to connect a fixed load (check your battery recommendations) to a fully charged battery for a limited time, and check to see how the battery voltage holds up.
A bad or failing battery’s voltage will drop rapidly within a short time.
Signs Solar Batteries are Draining Too Fast
Your solar batteries are probably draining too fast if you notice a considerable drop in the runtime (hours) of the connected appliances or even when no appliances are connected.
Note, this in and of itself is not confirmation, as it is possible that your location is receiving fewer sunshine hours or the appliances, are being used for a longer than usual duration.
Read on for other likely reasons why the batteries may be draining fast.
Batteries Failing? What Signs Show
In addition to batteries draining too fast with or without any appliances connected, look out for failure for the battery voltage to rise to the expected battery voltage during the charging process – 14.5V for AGM.
They’re batteries whose voltage does not raise beyond 11 or 12V
These are some of the signs that may point to a failing battery. Arrange for additional tests to confirm that indeed the batteries are bad.
Related Questions
1. Why Solar Batteries Fail Prematurely (+ Tips to Extend their Lifespan)
1. Undercharging and overcharging batteries. Solar batteries may fail prematurely if not properly charged.
Make sure the charge controller is set to charge the correct battery type to guard against both undercharging and overcharging.
2. Storing partially charged batteries. Batteries in storage should be topped up. In the case of AGM batteries, monitor their voltage every 3-6 months and recharge them should the voltage drop to below 12.4V.
3. Deeply discharging the batteries. Avoid draining the batteries beyond the recommended depth of discharge – 50% for AGM and about 80% for LiFePO4 batteries.
2. Do Solar Batteries Need Servicing?
Check the manufacturer guidelines for servicing the batteries. The older flooded-type batteries will need to be topped up with distilled water in addition to making sure that battery posts are clean and firmly connected with no corrosion.
Both AGM and Flooded lead acid batteries may need to be desulfated from time to time to not only improve their capacity but in some cases, extend their battery life.
You may also be interested in this post: Car Battery Dead -Will a Desulfator Revive it?
It’s best that you check what the battery manufacturer recommends.
Closing Thoughts
If your solar batteries are discharging quickly, as a first step, make sure they are charging fully.
Check that there are no appliances draining the battery that you’re not aware of.
Don’t rule out the batteries failing too!
Related Topics
