San Diego California Campground Sunset

RV Solar Series: Lithium/Lead Acid Final Analysis

This is my Lithium/Lead Acid Final Analysis where the determination isn’t necessarily all data-driven. Live style makes a big difference in the end result conclusion on the Lead/Lithium debate is going to happen.

One of the biggest problems with lead-acid is that they don’t like to give up electricity without a fight. Tell this to anyone who has seen sparks or watched a lead-acid weld two tools together, and they would think I’m a nut.

I have babied my AGM (lead-acid) battery for a year, I have asked only a little of the energy potential never asking for more than 36% of their electrons before I charged them back to 100%. I do admit not to allowing the float charge periods from the generator, so there was a little adversity in their life. My AGM battery should have at least 1000 cycles remaining in their future, four or more years as I use them while living full time. (perhaps four years is optimistic)

Microwave

I want to use my battery more and here I hit another problem. The reason behind this decision is the microwave with a wonderful built-in convection oven. If I were to connect this device of culinary delight to my AGM battery the demand for immediate sustained high energy flow would trigger the stingy character of the battery and it would resist my attempts and result in early battery failure. For the uninitiated, this description is called Peukert’s law. “If the rate of discharge increases, then the available capacity of the battery decreases.”  This detail is the reason my 300 amp hour battery is unable to run high energy demand devices including my microwave.  It is also the reason that hybrid cars use lithium batteries and not lead-acid batteries.

The opposite is also true and this reason is why I can’t charge my batteries to the full potential output of my solar panel array. My panels could recharge up to 600 amps of a lithium iron battery. Lead-acid batteries would fail if I attempted a fast recharge like this. This is because the output in amps could be held higher almost all the way to the end of the charge cycle with lithium batteries. Lead-acid batteries demand much slower recharging.

I should note that both lead-acid and lithium iron batteries love to be re-charged slowly and a slow recharge extends the life of both batteries.  Also, remember that Lead Acid batteries love to be fully charged and lithium batteries would have an extended life if they were left partially empty.

Stingy Batteries

None of the stingy nature of discharge rates applies to lithium iron batteries although there are limits on how much can come out and how much can go back in during short term charge cycles.  However, you can charge lithium batteries at a much faster rate than you can charge lead-acid batteries without ever getting to the point of recharging too fast. Remember the Bulk, Absorb and Float charge description of my solar design.  Almost all the charging up to full capacity of the lithium battery will be in the bulk mode which will be at least four times faster than  I can charge my battery.

Lithium/Lead Acid Final Analysis, Lithium’s biggest limitation

If you camp in the winter, in cold-country, lithium may not be for you. Lithium batteries hate to be cold.  They don’t like giving up their energy when they are cold (around 26 degrees Fahrenheit, -3.3 Celsius).  To be fair lead-acid batteries also don’t like to be cold and this dislike of being cold amplifies the Peukert effect explained above. Anyone who lives in cold country knows that cars don’t like to start when they are cold, it is not just the engine that doesn’t like the cold, the batteries don’t like the cold.

No Cold Charging

Even worse than being unwilling to discharge is the fact that lithium is unwilling to be charged when it is cold. Attempted cold recharge will ruin lithium batteries.

The battery management computer, will not allow you to charge the battery if it is too cold.  Too cold means below too cold means that the inside of the battery is less than 32 degrees Fahrenheit, 0 degrees Celsius.  In this case, if you needed to charge the battery, the battery would first have to be heated to above freezing.

This cold charging limitation is why most lithium batteries are installed inside the RV…. Not outside where my battery is located.

Conclusion: Lithium/Lead Acid

  • If you never camp without hookups you don’t need solar or an expensive battery.
  • You can’t expect a small solar panel to recharge your battery. A small solar panel will sustain a charge for an RV in storage.
  • Pointing a medium-sized solar panel(s) at the sun is better than a large, flat-mounted solar panel(s).
  • Most of the available solar energy hitting your solar panel will be unused.
  • If you only camp a few weekends a year, solar and a small lead-acid battery will probably be enough.
  • If you over-drain or don’t fully re-charge a lead-acid battery including float charging, it will lead to early battery death. And lithium battery(s) do not require full recharge on a daily basis.
  • To bridge multiple days without charging you need a large battery. A large enough lead-acid battery weighs too much for an RV. Lithium is the only battery that will be sufficiently large enough to power my RV when cloudy. Lithium batteries are the only battery light enough to perform this task.
  • A slow recharge for both lead-acid and lithium leads to a longer life. Lithium is willing to accept a charge must faster than a lead-acid battery.
  • To use lots of energy, during a short time period, like running a microwave, you need a lithium battery. To run an air conditioner or convection oven you need a big lithium battery.
  • In the long run, lithium batteries cost less than lead-acid batteries of all types.

Lithium/Lead Acid Final Analysis: Big decision: 

I’m ready for lithium, but my RV is not. Yes, I could just swap my AGM batteries with drop-in lithium batteries. This would bridge multiple days of poor weather. Yes, I could continue living as if my electricity was still limited.  But what I want is a big jump in useability when I get lithium batteries. This means I want everything to work, at least until the battery can no longer deliver. And I want to recharge my lithium at a quicker rate — all this means that before or at the same time as I get lithium, I first need a big inverter so that I can run that microwave from solar power.

If I doubled my solar added a big inverter and had lots the same weight dedicated to lithium batteries as a currently carry in lead-acid, I could also run my air conditioner from my solar panels. 

In this Lithium/Lead Acid Final Analysis, I have tried to couple lifestyle into the question. Should I make a big upgrade? Should I make a big investment in or in terms of lead, make do with.

Update: June 27, 2020, We are now powering our RV using a major electrical remodel. We don’t have solar yet but the battery remodel has changed our life (yes it is lithium). Here is the story. Hybrid Mongrel Battery and Massive Electric Bucket

We created this site to help our friends with their RV questions. Feel free to ask questions or comment and we will address them to our best abilities.

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4 thoughts on “RV Solar Series: Lithium/Lead Acid Final Analysis”

  1. Stephen Monteith Albers

    One important correction needs fixing. Just like lead/acid, there are numerous different lithium technologies, each with its own set of characteristics. Specifically, there are lithium technologies that do not have the cold weather limitations of iron phosphate that as of now, are undeveloped. I’m nearing a working prototype. It is the potential ultimate solution to adequate, reliable RV power.

  2. If you’re looking for better cold-weather charging limitations than those offered by ‘typical’ LiFePo4 batteries, you might consider LifeBlue’s LB-HCLT series. They feature a built-in, low-power-draw electric heater that allows charging in temperatures as low as -4 degrees F.

    I camp almost exclusively during the fall, winter & spring (I really dislike crowds & having to make reservations, sometimes months in advance!) and have had many 5 to 10 degree nights, camping in the snow without ANY battery charging issues.

    I love these batteries; they are available in an 8D size, fit in my RV’s original (basement) battery compartment & include a 10-year warranty! What’s not to like?
    Felix

    1. Felix. I thought I would have a problem with keeping my batteries warm. But I was worrying about nothing.

      Our battery compartment temperature taken at the battery terminal has never dropped below 40 degrees. No reason to stress or apply extra heat.

      We just monitor and can apply heat if necessary.

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