updated May 2019

Lithium-ion batteries in RVs

Lithium-ion batteries in RVs – they are safe to use. They deliver a lot of energy and pack a lot of power but need specialised knowledge to use safely and reliably. Here’s how and why for the LiFePO4 variety.

Pic: the lithium battery co.

Lithium-ion batteries in RVs – they are safe to use. They provide ample energy and power but need specialised installation to do so safely and reliably. The type generally used are the so-called LiFeP04. That term denotes their chemical make-up. It is not a trade-name. These batteries are not the lithium-ion type that initially had fire issues.

Lithium-ion batteries – they are safe to use: energy and power

Energy enables work to be done. Power is a measure of how fast that energy is used. A child readily stacks 200 one kg cans on a shelf two metres high. An Olympic weight lifter heaves 200 kg two metres high in a second or two. Both use the same energy but the weightlifter exerts hugely more power. Lithium-ion batteries in RVs – they are safe to use. They have both energy and power. For RV use, however, their power is far greater than needed.

Microwave ovens apart, an RV needs only minor power. There are good reasons to use lithium-ion batteries in RVs. Power is not a major one. Doing so is like having an Olympics weightlifter stack shelves in a supermarket. If their weight is no issue, a 300 amp hour AGM battery bank is ample for RV loads and a fraction of their price.

Safe to use: lighter and smaller

Lithium-ion batteries are of real value in RVs where space and weight are at a premium. They are about one-third of the size and weight of conventional rechargeable batteries.

Chargeable very fast

Lithium-ion batteries can be charged at massively high current. One of 12 volt 100 amp hour will readily accept a 300 amp charge.  RV alternators usually supply up to about 70 amps so that is a major plus. Grid-voltage chargers that size are made – but cost over $1000.

Almost constant voltage

In RV use, lithium-ion batteries maintain a constant 13.1-13.0 volts. This only drops to 12.9 volts when they have about 20% remaining. When used like that, they are good for about 2000 such cycles. Most other batteries’ life is limited to about 500 cycles if routinely discharged below 50%.

This graph shows the typical (per cell) voltage during discharge. That most probable for an RV is slightly above the dark blue line. That shown by the other lines are of high constant discharge and do not apply to RV use.

Such constant voltage (and in RV use) almost regardless of load, ensures that lights do not flicker when the fridge or water pump cycles on/off. Nor the fridge loses cooling, as with conventional batteries as their voltage falls.

Another lithium-ion battery plus is that energy loss whilst charging LiFePO4 is only 5% or so. That of most other types is about 20%.

Lithium-ion batteries – a truer comparison is ‘usable amp-hours’

The LiFePO4 batteries used in RVs must be compared on a ‘usable amp-hour basis. A 100 amp-hour such battery in typical RV use has much same usable capacity as a 130-150 amp hour AGM. They do, however, cost three times an AGM’s price. For RVs with limited space and weight carrying, particularly if away from grid power, such batteries are ideal.

Coach conversions and large fifth-wheelers

Where space/weight capacity is less limited a 350 amp hour or so AGM battery bank supplies ample energy and power at a third of the cost. Their life-span is shorter if routinely discharged to 50%. Increasing that bank to 450 amp hour brings it close to lithium-ion.

Lithium-ion batteries – installation and charging

This was initially a major issue. Until recent years expertise was rare. Most auto-electricians now know how it must be done. A few LiFePO4 vendors offer ‘drop-in’ direct replacements but qualify that in the small print.

Some LiFePO4 vendors claim ‘normal’ alternator charging is fine. This cannot be. There has been no such thing as a ‘normal alternator since 2000. Then, alternator outputs began to vary:  from 12.7 volts to +14.7 volts. Many had voltage varying with load and/or temperature. Some now vary from +15 volts to 12.3 volts. Or, at times, even none.

Many major alternator chargers makers have units specifically for LiFePO4, or with a LiFePO4 option. Such chargers include under/over voltage protection and cell balancing. Some also accept solar input.

Lithium-ion batteries – pricing

This is still an issue. Unlike AGM batteries (where capacity relates to lead content weight), there are fewer lithium-ion battery makers. Many are the same product sold under various brand names. There can be varying supply chains. Each adds a profit margin. As a result, totally identical products may vary in price. This issue is lessening as competition increases. It still cannot be assumed, however, that higher price equals higher quality.

Installing lithium-ion batteries in RVs – they are safe to use

As this article on Lithium-ion batteries in RVs – they are safe to use, installing lithium-ion batteries and/or alternator chargers is too complex to explain in article form. It is totally covered in our associated books Caravan & Motorhome Electrics, and Solar That Really Works!  Both are now in a choice of digital and print versions.

This area constantly changes – so this article (and our associated books) are updated when necessary.