7 Reasons Your Inverter Battery is Not Charging

Not so long ago my inverter battery would not charge.

It became a big problem as I needed it to run my food truck I ran in the evenings.

Without a charged battery and inverter I couldn’t run my lights or refrigerator.

At first, I screamed in frustration as I thought it was going to be expensive to replace the inverter charger.

After calming down for a few minutes I decided to investigate the problem and find the solution.

I wasn’t the first and won’t be the last to experience this problem.

In fact, you’re probably feeling the frustration right now!

But don’t worry, that’s why I’ve written this article from my own first-hand experiences.

Together we’ll go through the most common problems for an inverter battery not charging, plus how to identify and fix it.


Dead Battery

Deep cycle batteries don’t last forever, eventually, all will stop working whether they’ve done too many charge cycles or become too old.

Batteries have a certain amount of charge cycles – the number of times it can’t be fully charged and discharged. Usually, this ranges between 500 – 2000 cycles depending on the battery quality. Adding to this, batteries tend to have a shelf life of around six years. If either of these are the case then it’s time for a new battery!

And of course, there’s always the chase that it becomes damaged in another way. For example, traditional lead-acid batteries can be damaged if you completely discharge them. You might not be able to recharge a completely flat lead-acid battery.

So if you have not used or charged your battery for a long time (a period of months or years) it might be completely dead. It’s always good to use a trickle charger to keep the battery from going flat.

Solution: If your battery is dead, it needs to be replaced.


Burnt Out Rectifier

The rectifier is a key component in charging a battery. It is in transformers to convert AC to DC while lowering voltage. 

Without a function rectifier, your charger won’t work. This is because the electricity supplied by the mains is 120V AC (Alternating Current). As you are not able to store AC electricity in a battery it must be converted into DC (Direct Current) for storage. Adding to this, battery voltage is usually much lower at 12V or 24V. 

You can easily burn your rectifiers if the cooling system isn’t working properly and the system overheats.

Solution: The charger must be repaired by replacing the rectifiers.


Blown Fuse

Virtually all electronics use fuses. They help to protect from power surges and short circuiting. They are designed to blow or burn out in this event to protect electronic circuits.

You might find a fuse becomes damaged during problems such as reverse polarity or short circuiting. Thankfully, it is usually very easy and cheap to replace a fuse. You might find instructions for this in your inverter or charger user manual. Some inverter chargers even arrive with spare fuses as it’s a common occurrence. 

Solution: Replace the blown fuse


Poor Cable Connection

Loose cable connections can appear over time. You might have a snug connection when you first install your charger but every time they can come loose.

This is very common in vehicles such as RVs, vans, trucks, and boats. Vibrations from engines and driving can work connections to lose over time. As you can imagine if the contact between cables and terminal current can’t flow properly. A tell-tale sign of loose cables is a drop in voltage from your charger.

Solution: Check, clean, and tighten all connections between charger and battery.


Charging Current too Small

If you’ve got a new setup or have recently added batteries into your system then you need to make sure your charging current is high enough. 

This is a particular issue if you have multiple inverter batteries connected in parallel. You might find the amperage delivered by your charger can’t meet the demands of your battery bank.

It’s best practice to have a maximum of 12 times battery capacity to charge current. For example, if your charger delivers 12A your battery shouldn’t be larger than 120Ah.

Solution: Use a higher capacity charger or reduce your battery size.


Sensor Failure

Inverters and chargers have many different sensors in them to detect any faults such as overloading, overheating, short circuit, voltage fluctuations. 

If one of these sensors encounters a fault, your system will stop working. This is because the system is trying to protect itself. In the event of a faulty sensor, you might not have an issue with the system. You will need to get a sensor repaired. 

It can be tricky to spot this issue as it presents another problem. You will have to remove the possibility of the alerted issue (e.g. overload) to know if a sensor is faulty.

Solution: Replace faulty sensor


Lack of Battery Water

It’s strange to think, but many lead-acid batteries need watering.

They contain battery acid which is mixed with distilled water. Over time this water evaporates, and without enough water the battery will not charge or deliver energy very well.

You should be able to check the water level on this type of battery to ensure everything is fully submerged or flooded. It’s good to check this every couple of months.

Solution: Refill the battery with distilled water


Tips to Keep an Inverter Battery Well Charged

Hopefully, you have been able to identify and fix the reason your inverter battery is not charging. 

To stop you having problems in the future here are some helpful tips to increase charging performance and overall battery life.

  • Use a trickle charger – If you’re not using your battery for months then get a trickle charger. This helps keep the battery topped up with charge during periods of inactivity.
  • Don’t deplete battery – You should never completely deplete your battery. This can lead to damage, and sometimes you can never recharge a flat deep cycle battery.
  • Keep battery watered – Flooded lead-acid batteries need to be refilled with distilled water regularly. You should check water levels every couple of months. Without enough water performance will be reduced and damage can occur.
  • Carry out regular maintenance – Regular maintenance will help to stop things like corrosion and loose wiring. You can do things like tighten connections and clean contact to get a longer life span for your battery.
  • Consider lithium batteries – Modern lithium batteries give you a much better performance and charging speed. Plus, they don’t suffer so much if you deplete them. It’s the same technology you get in smartphones.

Final Words on Inverter Battery Not Charging

I hope this article helps you through your problems with an inverter battery not charging.

It’s horrible when you run into this issue, especially if you rely heavily on your power inverter to work or live.

Usually, there is a simple explanation for the issue such as poor cable connection or a blown fuse.

On the other hand, you might have a tired battery or charger that simply needs replacing. Need a new battery? Read my guide to the Best Battery for Inverter Use.

Thanks for reading and good luck.