How to Make Solar Batteries Last Longer

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Solar batteries serve as the storage for solar power,. and without it you’ll be forced to use all that power at once. For this reason, solar battery maintenance is an absolute must. Making batteries last longer is the Holy Grail of all solar power users, and fortunately it is not as hard as you might think.

The two most commonly used solar batteries are lithium ion and lead acid. Lithium ion batteries need very little maintenance, but there are ways to extend its life even more as we will show. As long as the battery is properly installed it should run fine.

Lead acid batteries have to be checked every few weeks for loose fittings. Lead acid battery also need water refills every 2-4 weeks to replace its electrolytes. They should also be recharged at the 50% level.

You can make deep cycle lithium batteries last longer by recharging when capacity drops to 15-20%. Lead acid batteries should be recharged at 50% while AGM batteries at 70%.

We will cover both lithium ion and lead acid batteries and their variants. Simply go over the appropriate section below.

Tip: always wear gloves and eye protection when doing battery maintenance. Remove any jewelry you are wearing and tighten loose or flowing hair to avoid making contact with the unit.

How to Make Lithium Battery Last Longer

Lithium ion is becoming more popular for its durability, low maintenance and consistency. They can be used in different weather conditions without deterioration. Two types are commonly used with solar power, lithium ion phospate (LFP) and lithium nickel manganese cobalt oxide (NMC).

LFP and NMC are maintained the same way. The difference between the two is NMC has a greater energy storage capacity. Some prefer one over the other, but generally speaking their lifespan is similar if properly taken care of.

Install in the Proper Location

Every lithium ion battery has a battery management system (BMS). The BMS checks the cycle life, charge state, temperature and other parameters. The BMS will let you know if the battery is running in an acceptable manner or not. Meaning, if you installed the battery in the proper location, almost no maintenance is required.

Use at the Recommended Settings

The product guide tells you the ideal working conditions for the battery. Keep the battery running in the suggested condition for optimum performance. While lithium ion batteries can run under varying weather conditions, it is best not to push it to the limit as it will shorten the lifespan.

Check the Terminals and Cables Regularly

If you placed the batteries in the right location, there should be no worries running it. However it’s a good idea to check the cables and wiring every so often. If you are going on a long RV trip, inspect the cables and make sure that everything is in order.

If you have just just come back from a long journey, park your RV for now and clean the cables. Remove buildup of dust and debris and your batteries should be all right. Tighten any loose cables and replace any that look worn out.

Avoid Very Deep Discharges

Do not wait for the level to drop below 10% before doing a recharge. Repeated deep discharges might lead to internal plating and damage circuitry. A lot of lithium ion solar batteries have short circuit protection that activates when it reaches 2.5V or 2V. Other manufacturers set a different threshold before opening the battery connection.

Steer Clear of High Discharge and Charge Currents

Frequent high charges and discharges reduce a battery’s lifespan. However there are some lithium ion batteries – like phospate and manganese – that prefer high current charges. Check your product guide for more details. Look at the manufacturer’s website for detailed descriptions and specs of he battery you’re interested in.

Avoid Operating in Extreme Temperatures

While lithium ion batteries can operate under extreme heat or cold, it is unhealthy in the long run. You won’t see any immediate effect in performance, but lifespan will decrease. Most lithium ion batteries will get a shortened cycle if charged under 0 Celsius / 32 F.

Constantly charging the battery under extreme conditions makes it susceptible to degradation and shorting. This could damage the battery and render it unusable. Follow the recommended temperature range to avoid this problem,.

Choose the Right Charge Termination

Choose a charger that utilizes the lowest charge current termination. Picking the minimal (either C/x or C10) prolongs battery life by not fully charging it. Yes, you can charge a lithium ion battery up to the fullest, but doing so won’t prolong its life.

By opting to charge up to 85%, you will get maximum mileage out of the battery and enhanced performance. You can terminate the charge at the C5 level as that’s like ending the charge at 85%.

Choose a Lower Float Voltage

One of the first things you will learn when comparing lithium ion and lead acid solar batteries is that lithium ion can be used fully up to 100%. But as we have pointed out, the extra percentage gains are not worth reducing the lifespan for.

One way to do this is to pick a lower float voltage. Cutting down the float voltage in turn boosts the service and cycle life. Yes the battery capacity goes down a little, but in exchange you’ll be able to use the battery for a longer period.

A reduction of 100 MV float voltage increases the life cycle by two, while a 300 MV leads to an extra 5 life cycles. The float voltage in lithium phospate batteries is lower compared to cobalt, so keep that in mind if you want to maximize the life cycle of your battery.

Partial Discharge Cycles are Good

The rule of thumb is to recharge after using 80%-90% of the battery capacity. Avoid full discharge cycles as well. It is better to do short and frequent charges for a lithium ion battery than doing a full recharge. While the short charges will equal a single full charge, it is better for the battery because its internal workings do not get too stressed out.

If you have a mobile phone you’ve probably heard of the suggestion that it’s better to recharge at 35%-40% and end the charge at around 80-85%. The same thing applies to solar lithium ion batteries. Those little charges and discharges are good for the system. Whether it is NMC or LFP, this type of charge / discharge is recommended.

Lithium ion batteries can suffer physical damage or malfunction due to faulty charging. Even if it does happen, the battery does not become hazardous. That’s why lithium ion batteries are considered the best type of solar battery today. With cost going down, expect their usage to increase.

How to Make AGM Battery Last Longer

Lead acid deep cycle battery is the most widely used in solar power systems. While lithium ion requires minimal maintenance, lead acid batteries are cheaper. With proper maintenance they should also last several years.

Two types are available: sealed lead acid batteries and flooded lead acid batteries. While they share some common maintenance routines, there are important differences between the two. These are for SLA (sealed lead acid batteries) like AGM and gel.

Check the SOC regularly

The SOC (battery state of charge) is the best indicator of the unit’s condition. With a multimeter you can check the battery’s voltage charge state. The battery needs to maintain a charge specific to voltage readings. Refer to your battery’s manual for a chart for these readings.

Test the Batteries in a Restive Setting

Allow the battery to rest a couple of hours prior to a voltage reading. By a restive state we mean no discharges or charges the past 2 hours. A healthy battery should get 100% SOC. If it doesn’t, the battery is probably damaged.

Sealed Batteries Should Never be Equalized

That applies only to flooded lead acid batteries. Doing so on sealed lead acid batteries could cause permanent damage. Check the instruction manual for further safety tips specific to your battery.

Clean on a Regular Basis

These batteries work best when clean. Pay close attention to the top and remove any grime and dirt buildup. A dry cloth or rag will suffice for cleaning.

Tighten Loose Cables

Loose battery cable connections can result in poor performance or not run at all. Every now and then, check the wires, cables and fittings around the battery. Tighten any loose fittings. If there is a sudden drop in performance it could probably be due to this.

How to Make Lead Acid Batteries Last Longer

These tips are for FLA (flooded lead acid batteries). AGM and gel are lead acid batteries too, so some of these may apply.

Perform Regular Maintenance

Flooded lead acid batteries require maintenance checks at least every month, preferably every 2 weeks. Tuning the battery on a regular basis is advisable.

Add Distilled Water to the Battery

We suggest adding distilled water to the battery at least every month (every 2 weeks is better). These batteries lose water after every charge and refills are needed to ensure optimum performance. Use only distilled water. Avoid tap water because they contain particles that could alter the battery chemistry.

The 2 to 4 week water refill is a general guideline. Climate settings and battery usage will determine how often a refill is needed. To find out when a refill is needed, full charge the battery.

Open the vent and inspect the water level. If it’s full, close the vent. Check the vent regularly. If it needs refilling, pour water up slightly below the maximum water line.

Keep an Eye on the SOC

A refractometer is a device that assesses the battery’s specific gravity, and the information provided by the refractometer will tell you the battery’s state charge. Your battery should have a specific gravity chart in the manual that you can use for reference with this tool.

Some would recommend you use a battery monitor to check its state. Battery monitors certainly have their uses, but you need to set them up properly. An incorrect installation leads to inaccurate readings. Whether you use a refractometer or a battery monitor is up to you, just make sure the devices are correctly set up.


Flooded lead acid batteries have to be equalized every 1 to 3 months. Equalization makes certain the cells are uniformly charged. Flooded lead acid batteries should have a charge after equalization and a full charge cycle. If there is none, the battery is probably damaged or it is close to the end of its life.

To equalize lead acid batteries:

  1. Inspect the water level.
  2. Shut off all loads.
  3. Position the charger at the equalize voltage recommended in your battery product guide.
  4. Commence the equalizing. Gas and bubbles will appear.
  5. Halt charging every 60 minutes and note the specific gravity. Stop charging altogether when the gravity no longer rises.

Clean Regularly

Keep the battery tidy. Remove dirt, grime and dust. Accumulated debris could lead to leaks and damage the battery. The frequency of cleaning depends on the conditions the battery is exposed to. Clean as often as necessary.

Tighten Loose Cables

Just like sealed lead acid batteries, loose wiring and cables can severely affect performance. The terminals have to be cleaned on a regular basis to prevent corrosion. Your user manual may provide a timetable for cleaning frequency. If not, every couple of weeks or every month will do.

If dry cloth won’t remove the dirt, mix distilled water with some baking soda. Dip a wire brush into the mixture and clean the battery. Rinse with distilled water and pat dry with a clean cloth.

Program the Battery

The first time you use lead aid batteries for a solar power system, the charger has to be programmed to match your solar bank. The voltage set points have to be programmed so the chargers are applied properly when the battery runs. The stages are:

  • Float charge: a trickle charge is sent to the battery so it is 100% charged
  • Absorb: the rate of charge slows as it nears 100%. By 80% the slowdown is evident.
  • Bulk: high current that charges quickly up to 80%.

The charger has to be at the right voltage for every stage. The voltage varies per battery. If the parameters are incorrect, the battery may not function properly or it might hasten its lifespan. This is where you need to refer to your user manual for specific information.

Inspect the Battery Settings

Changing the following battery settings can affect performance for better or worse. Usually you set this during the initial programming stage. We don’t recommend changing any of the settings unless you’re testing the battery or noticed a drop in performance. Among the options are:

  • Temperature Sensor: battery chargers may come with a setting that modifies performance based on temperature.
  • Charge Current Limit: this is an important feature that ensures the battery does not get overcharged. You can use this to modify the output of the charger, but be careful when making adjustments.
  • Maximum Input Current: checks the current from the loads and battery charger. this is used to keep the current from going over the generator’s rating.

Your battery may have other settings, but even if they are the same as those above, the specifications will be different from other batteries. Do not use settings from other batteries unless the manual specifically say you can do so.


Lithium ion and lead acid batteries have their pros and cons. Lithium ion is more expensive but needs little maintenance. Lead acid batteries are cheaper but they don’t require ore regular checkups. Whichever you choose, knowing the right steps for maintaining solar batteries will ensure their longevity and consistent performance.