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Choosing the right batteries for your off-grid solar system is highly important because different types of deep cycle batteries have varying levels of energy efficiency, cost effectiveness, and storage capabilities. There are some things you need to consider when choosing the right solar battery, such as battery lifespan, ease of installation, cost, and storage space. Below, we can help guide you to figure out which battery will be the best battery for your solar panel system.

Deep cycle batteries are the recommended batteries to use in solar installations. There are a range of different deep cycle batteries, including lead acid, sealed lea, AGM Batteries, Gel Batteries, and Lithium LiFePO4 batteries.

Lead acid batteries:

• Known as wet cell batteries, and the most inexpensive option, are readily available at most big-box and auto stores. The Benefits of Lead Acid Batteries are they have a fairly low upfront cost, they are quite safe, and fairly reliable.  The downside is they are the most high maintenance as they need to be kept in a well-ventilated environment, suffer from corrosion, and they need to be kept upright to prevent leaking.  Also, they tend to be very large, heavy, and take up a lot of space.

AGM Batteries:

• AGM stands for Absorbent Glass Matt.  This is a non hazardous type of lead acid battery, but one where the electrolytes are absorbed into a glass matt.  The AGM battery has a lower internal resistance, plus they are better at handling temperatures.  These batteries store 10 to 15 percent more energy than standard lead acid batteries, and charge up to four times faster. The plates in an AGM battery can be flat or they can be wound into a spiral. 

Gel Batteries:

• Gel batteries use fumed silica to thicken the electrolyte.  This makes this type of battery sturdier as the nature of this electrolyte prevents the battery from leaking when damage occurs.  Gel batteries do not require much maintenance at all and are resistant to shock and vibration.  They work great in extreme heat or cold conditions, and have excellent life cycles.  Gel batteries do have narrow charging profiles so it is not hard to damage them by improperly charging or overcharging them.   

Lithium LiFePO4 batteries:

• Lithium LiFePO4 batteries have great efficiency, really long lifespans, and are also very safe and stable.  They barely require any maintenance, and don’t require any attention for at least 15 years after installation.  They last four times longer than lead-acid batteries and weigh much less.  The only downside is they are the most expensive option, as they cost up to 4 times as any other solar battery.

HOW LONG DOES YOUR SOLAR KIT TAKE TO CHARGE A 12V 100AH BATTERY?

Sunlight, temperature, and battery will influence specific charging times. To get a general idea, you’ll need to calculate amps delivered from your solar panels (total wattage/voltage of your battery). Then you’ll divide the amp hours of your battery by amps delivered. For example, if you have a 100ah 12v battery with three 100 watt solar panels, your system would deliver 25 amps. By dividing 100Ah by 25 amps, you’ll learn it will take four hours for a 300 watt solar panel system to charge a 12v 100ah battery.

Battery Capacity:

• One of the most important things to consider before buying any solar battery is its capacity, meaning is how much energy the battery in question can store.  Battery capacity is typically measured in units of Amp-Hours (Ah), it states the amount of energy that a battery can hold under specified conditions. For instance, a 12 volt 18 Ah battery can delivery one hour of 18 amps of current at 12 volts.
• One thing to think about when sizing a battery, is that a battery with a low capacity and high power rating can run your entire home, but for just a few hours, whereas one with a high capacity and low power rating can only power a few important appliances, but for a long time. Basically, the higher the capacity and the higher the power rating, the better off you are.

Charging Time:

• The faster a battery charges, the better off you are at keeping your off-grid solar system working effectively.  Lithium-ion and gel batteries are the best for this application as they charge extremely fast.  A lead acid battery can take up to nearly an entire day to charge if not longer, whereas Lithium-ion and Gel Batteries take approximately 3 hours to reach full charge. 

Budget:

• While shopping, we always look for the best bang for your buck.  One thing we want to take note here is an old saying “You always get what you pay for.” Generally speaking, the more expensive the solar battery, the better it will perform and the longer it will last.
• A lithium-ion battery might cost multiple times the amount of an AGM or lead acid battery, but it comes with huge advantages like less maintenance, more resiliency, easier to install, and better overall performance in pretty much every category.

Lifespan:

• Another important consideration is how long the battery will perform and last. Each and every day as your battery gets older, it will have less of an ability to hold a charge. Each battery you buy will come with a certain number of hours, days, and years until it will expire and give out.  This typically depends on the type of battery, size, and brand you go with, but overall the longer you want it to last, the more money you will end up paying.  Another tip is to always pay attention to the ratings on the packaging so you know what you are purchasing. 

Warranty:

• Last but not least, you want to look for how good the manufacturers warranty is.  A 20-30 year warranty is good, but lifetime warranty is the best!   You do not want to end up spending hundreds to thousands of dollars on a battery bank and it ends up breaking in a few years without a warranty.

We recommend wiring batteries of the same type and amp hour rating in your solar installation.  For example, if you go with AGM batteries, all the batteries in your battery bank should be AGM batteries. This will limit any efficiency loss due to having different batteries.