RV Batteries and your solar power system

The type of RV batteries you select will have a major impact on your day-to-day lifestyle while you’re using your RV.  The battery plant is one of the most important components of your solar power setup, and we’re going to explain a little about each type of battery available.

Your solar panels collect energy while the sun is up.  Your RV batteries store that energy for future use.  How much power they can store, and how much power you can take from them depends on a few things.  The amount of energy coming from your solar panels, the charge controller you put in between the solar panels and your RV batteries, and the size and type of battery plant you build for your RV.

Today you have a choice between 3 types of RV batteries.  Lithium batteries are the newest type of battery available for your solar installation, and they’ve got a lot of positive features.  AGMs (Absorbed Glass Mats) are also a favored choice for RV power needs.  And finally there’s the old standby, flooded lead acid batteries.

We will only be talking about Lithium and AGMs for your solar battery plant needs.  While the old flooded lead acid batteries are still out there, we’re sticking to what we know really works for our customers.

RV Batteries – Lithium Ion

The most recent innovation in batteries for your RV solar power needs is taking the industry by storm.  Lithium Ion batteries offer much more to RV’ers beyond the standard flooded batteries and AGMs (Absorbed Glass Mats).  In the case of many installations, lithium batteries might just be the right choice.  But, just like everything else available, there are some drawbacks and issues as well.

• A longer life span: With the latest lithium batteries you can expect anywhere from 2000 to 5000 cycles (provided they are well maintained of course).  Additionally, a lithium battery will deliver more than 75% of its capacity after 2000 cycles (according to testing).  In the case of AGM’s, you can expect about 500-1000 cycles.  The longer lifespan of lithium batteries comes with a price, literally.  Lithium batteries cost about three times as much as AGM batteries.  But with a well maintained system, the payoff is pretty clear, lithium offers more.
• Improved usable capacity:  Lithium batteries can regularly discharge 85% or more of their rated capacity.  In the case of  AGM batteries, they are rarely discharged beyond 50%.   As an example, a 100 amp hour battery  lead-acid battery will give you access to only 30 to 50 amp hours.  With a lithium battery you could use up to 85 amp hours.  Bottom line, you get about twice as much charge in a similarly rated lithium battery installation as you would with an AGM battery setup.
• Voltage Sag:  The discharge curve of lithium batteries (especially when compared to lead-acid) is essentially flat, meaning that a lithium battery at 20% will be providing nearly the same output voltage as it would at 80%.  As the charge level on a lead-acid battery decreases so does the voltage.  This is not the case with Lithium, the voltage doesn’t drop.  If lithium batteries are fully discharged, their voltage will drop off. A BMS (Battery Management System) will be used to protect the batteries and prevent full discharge, as the results of full discharge could pose problems.  Completely discharging a lithium battery bank can permanently damage it.  So a BMS is critical to the function and maintenance of your lithium power plant.
• Fast Charging:  Lithium batteries charge very quickly.  Unlike AGMs or flooded batteries, lithiums don’t have to go through the “absorption” phase that other batteries have to.  In the case of standard lead-acid batteries there are 3 phases, bulk, absorption, and float.  Absorption can take hours.  But, with a lithium battery plant, there is no absorption phase.  The bottom line is simple.  Faster charging for your system.
• Low Maintenance:   The battery management system does all the work for you.  It automatically balances the system for you (like equalization in a lead-acid battery planet), and ensures that all the cells in the bank are equally charged.
• High Output:  Lithium batteries can deliver their full rated capacity even at high currents.  In the case of lead-acid batteries you can see as much as a 40% loss of capacity at high loads.  What does that mean?  Lithiums make the perfect choice for high capacity needs like your microwave or air conditioner.
• Weight reduction:  Finally, lithium batteries weigh a lot less than standard AGMs.  A 600 Amp hour lithium system versus a 600 Amp hour AGM system will weigh much less!

There are other benefits to Lithium systems, and there are a few cautions as well.  We are here to help you determine what type of battery plant will work best for you.

RV Batteries – AGMs

Flooded batteries that require the owner to regularly add water are no longer the standard for deep cycle batteries in an RV installation.  Sealed lead-acid AGM (Absorbed Glass Mat) batteries have replaced their flooded cousins, with good reason.  Lower maintenance, more life cycles, and easier installation.

AGMs cost a good deal less than today’s lithium batteries.  But, as noted in the previous section, lithiums out perform on many levels.  So why select AGMs?  Price of course, lower system usage, and maybe fewer RV power needs.  These are a few reasons why customers may opt to go with AGMs on their RV solar power system.

AGM batteries cost about twice as much as flooded batteries, but are well worth the price.  They are still lead-acid batteries but are sealed instead of vented (so you can do indoor installations, unlike flooded batteries).  The electrolyte is held captive in a fibrous glass mat that can’t be spilled.  This glass mat also provides pockets that assist in the recombination of hydrogen and oxygen gases (that are generated during charging) back into water.

AGM batteries typically have a greater charge acceptance than flooded batteries and require significantly less time to recharge.  This translates into higher efficiency, which means a shorter generator runtime when you find it necessary to recharge quickly.  AGM batteries also hold up better and stay at a higher voltage when powering heavy loads like a microwave oven.

AGM batteries have very thick positive plates and belong in the true “deep cycle” class.  They don’t outgas (unless severely overcharged); and because of this, they don’t corrode terminals and do not need to be watered.  The savings in maintenance alone could be worth the extra cost.