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Off the grid systems often run inverter batteries continuously, but if you won’t be using them for a while, storage is a good idea. Lithium batteries however, must be stored correctly or they might become unusable. The following guidelines explain how to store LifePO4 lithium batteries, and these are applicable for other battery types too.
Inverter lithium batteries should be stored indoors during winter at 50% or higher capacity. For 3 months’ storage, keep the battery in temperature between 14-95 degrees F. If you are going to store a battery for more than 3 months, a range of 60-95 F is ideal.
How to Store an Inverter Lithium Battery
- Charge the LifePO4 battery until capacity is at least 50% full. You can also charge it to 100%. This is an important step and you must not proceed until this is complete
- The battery must be at least half full so there is power left even when it self-discharges. It also helps if you have a high quality lithium battery like the CHINS LiFePO4 which does not get damaged even during long storage.
- Once done, move to step 2.
- If the inverter is still running, turn it off. Disconnect all loads and unplug everything.
- Turn off the battery. Disconnect the wires connecting it to the inverter.
- If it is winter, move the battery indoors. It can be anywhere as long as the temperature is ideal. The temperature depends on how long you plan to store the battery.
- A few weeks storage: 23-95 F (-5-35 C)
- 1 month storage: 4-140 F (-20-60 C)
- 3 months storage 14-95 F (-10-35 C)
- Longer than 3 months storage: 60-95 F (15-35 C)
If you are going to store the battery for a long time, cycle it every 6 months. This is necessary to keep the battery going.
Do not store a lithium battery that has been completely discharged. Doing so will cause permanent damage.
It is important to store the inverter battery properly, otherwise this can cause all sorts of problems. Once you are ready to use the inverter again, check if the battery is fully charged.
Please note that these temperature ranges is a general guideline. Some lithium batteries may require a specific temperature setting. Refer to the owner’s manual that came with your battery.
Do You Have to Disconnect Inverter Batteries Before Storage?
All inverter batteries have to be disconnected prior to storage. This is necessary to prevent permanent damage. Batteries also self-discharge during storage. If the capacity is low, there might not be enough power to make it usable.
- If the battery is connected to the inverter, it is tempting to just leave it there. But if you are not going to use it for a long time, proper storage is still the best.
- Most RVs and solar powered homes run a lot of devices on their inverters.
- Unless you actually disconnect the positive and negative cables, the battery could discharge while in storage. If the battery keeps discharging there will not be enough power left when you take it out and want to use it.
Inverter batteries have a self-discharge rate of 1-2% per month. This is true for lithium and AGM batteries alike. As the battery gets older, the discharge rate can increase to 2% per week. You can avoid this by getting a high quality battery like the Ampere Time 12V.
Battery Self-Discharge Rate
The following scenario makes it clear why inverter batteries must have some power left when stored.
Suppose you want to store a lithium battery for 6 months. If it has only 8% charge left, it will run out of power by the end of the storage.
At 2% self-discharge per month, it will lose all charge at 4 months. If the battery is old and discharges 2% a week, there will be nothing left after just a month.
Recharging a completely empty battery is possible but difficult. Especially if the battery is coming out of winter storage. If the battery is old, recharging might be impossible. If you maintain 50% capacity or more, there will be enough power left when you take the battery out of storage.
If you are going to store the battery for longer than 6 months, a full charge is better. This is definitely the case if the battery is several years old and self-discharges faster.
How to Prevent Inverter Battery Damage in Storage
Apart from the guidelines that we have already stated, there are other things to keep in mind. Follow these and you can be confident about storing the battery during winter, or any time.
Read the manual that comes with your battery. While lifepo4 batteries generally work the same way there might be differences due to the manufacturing. Having a good battery also helps.
Keep the battery at least half full. Never store a battery without any charge. Lithium batteries have to be stored in a cool, dry place. Follow the temperature guide given above. Never store or run the battery in 149 F / 65 C.
- Once the battery is stored, try to keep the temperature in the suggested range. Clean the cables and terminals with a dry cloth. Wipe away all the dirt and watch out for corrosion.
- Do not use corroded batteries. This can damage the inverter when you plug it in and possibly even the appliances you connect.
- If you removed the battery from storage and it is not able to discharge or charge, the cable connection might be loose. Other possibilities are the voltage is too low or the connection between the inverter and battery is loose. Tighten these wires and try again.
How Cold Weather Affects Battery Storage and Performance
Never store inverter batteries in cold weather. This could lead to permanent damage if the temperature drops too much the battery casing might crack. And as explained earlier, high temperature will also cause damage.
Discharging the battery at 32 F / 0 C also leads to capacity loss and subpar performance. A 12V 100ah lithium battery might only run at 80ah, or an 80ah at 70ah capacity.
This does not mean the battery is damaged. That is just how deep cycle inverter batteries run in the cold. When the temperature starts to rise, the capacity will increase also.
The risk of lithium plating increases when you discharge a battery in freezing temperature. This usually results in a short circuit and therefore should be avoided.
Troubleshooting Inverter Battery Storage Guide
I stored the battery for a couple of months. Now the voltage is so low. What should I do?
The battery probably self-discharged rapidly during storage and is now completely empty. Recharge it as soon as you can. Charging can take a while especially if the battery is old. Once the battery is up and running, ensure the battery and the loader are properly connected. This is necessary to avoid overheating.
Why is the battery temperature so low / so high?
The battery was subjected to extreme cold or heat. Unplug it from the inverter and disconnect everything from it. Let the battery warm up or cool down until it reaches room temperature.
After the battery warms up or cools down, you can start charging it. If you stored the battery at full charge you can connect it to the inverter right away. If not, charge until it is full.
Both the inverter and battery have to be installed in a cool, dry place. Make certain the wires are connected tightly. Refer to your battery owner’s manual for specific parameters during the charge. Usually though the default settings are fine.
What should I do if the battery voltage drops to zero?
You need an external charger that can work with the battery.
Why is there so much current going in the battery?
If you have a charge controller this should not be an issue. If it keeps happening, disconnect the battery and remove all load on the inverter. Reconnect the battery and wait for the current to flow normally. Once it does, reconnect each inverter load.
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