It started as the barest of whispers by Terry in the RV community, but the chorus of lithium lovers is steadily growing. So what is it that everyone is raving about?
Faster charging and discharging
Lithium batteries will accept a charge much faster than lead acid. This means your battery can take the charge from your solar panels, DC to DC charger and/or mains charger as fast as they can give it. This can mean the difference of an hour vs a day to recharge from mains power.
A lithium battery will charge in boost mode right up to 99% state of charge, unlike a lead acid battery which will only boost charge until 70% state of charge, after which it spends a long time dropping back the charge current until just trickle-charging that last bit.
This ability to fast discharge allows you to run appliances that require a sudden peak load, without a serious drop in voltage. This would apply to air conditioner start up, microwave ovens, induction stoves, coffee machines, bread maker, etc.
Our lithium battery can accept 100% of its advertised capacity (100amps per 100Ah) of advertised capacity before the battery voltage starts to climb excessively. This is because our lithium batteries have a very low internal resistance. They have a very low internal resistance because they work by lithium ion transfer rather than the chemical reaction that lead acid batteries use. A lead acid battery cannot accept a high current charge for very long before the voltage rises above the safe level for the battery and causes damage to the battery.
You can safely have 100% of the advertised capacity of a lithium battery - this is not the same as draining a cell below 2.8 volts, which is a lot more than the advertised capacity.
A lead acid battery can only give you a maximum of 50% of its available charge before it drops below 12 volts under a relatively light load. A heavy load will see the voltage drop below 12V long before 50% of the capacity is delivered. The older the battery, the less you can have.
They weigh less per amp hour
Lithium batteries weigh a lot less than lead acid per useable amp hour, so you can either save some precious weight allowance in your RV, or upgrade to a higher-capacity battery for the same weight.
A 100Ah lead acid battery weighs between 30kg and 32kg. If your 100Ah lead acid battery weighs less than 30kg, it is not a 100Ah battery - you've been ripped off.
A 100Ah lithium battery weighs 16kg. They don't make light-weight lead or light-weight lithium. A lead acid battery can supply 50% of its capacity from fully charged before it drops below 12V under load when the battery is new. A lithium battery can supply 100% of its advertised capacity from fully charged without dropping below 12V. This means effectively, per useable amp hour, lithium weighs a quarter of the equivalent usable amp hours of lead acid.
They like to work
The days of keeping a close eye on your battery voltage for fear of shortening the life of the battery are over when you switch to lithium. Lithium batteries discharge without a serious voltage drop due to their low internal resistance. They don’t have to be returned to 100% state of charge (SOC) each time they’re discharged in order to keep a good cycle life. They like to work, so there is no need to fear shortening their life by working them hard. They will actually thank you for it.
There's no need to keep them fully charged
If a lead acid battery is not brought back to 100% SOC, its life span will be seriously shortened due to sulphation of the plates. Lithium batteries don't have that requirement to return to 100% SOC all the time. It does need to happen from time to time, and it will generally happen anyway in sunny weather, but it's not something you have to keep an eagle eye on the way you do with lead acid batteries.
Lithium batteries don't like to be stored at 100% capacity and don't need to be regularly recharged the way lead acid batteries do. Hard to get your head around, but it's the complete opposite of what you've known about batteries so far.
If you're going to store your RV for more than six months, we recommend you bring your T1 lithium battery down to 50% State of Charge (SOC), and then disconnect/isolate your battery.
If you're going to store your RV for less than six months, and it's going to be outside, we recommend just leaving the compressor fridge or something similar on to supply a load, and let your solar panels supply charge. Your T1 Lithium system will monitor your cells and keep it within the SOC (100% to 5%) and voltage limits that we've set, whether you're there or not. If you're worried about low solar days bringing the SOC too low, it would pay to make sure your fridge is empty, because your T1 Lithium control system will automatically isolate your battery at 5% SOC. Turn off any other loads such as inverter.
They have a much longer cycle life
Just how long, we don't really know, as we haven't had any die of old age yet, and we're in our ninth year of installing lithium in RVs. So let's take a look at what manufacturers say:
A cycle for a lithium battery is measured by charging the battery to 100% state of charge, then discharging to 0% state of charge. This is one laboratory cycle. Even though this is not how most people use their batteries, this is how good lithium battery manufacturers describe a life cycle, so we'll work with what they give us:
- A lithium battery will cycle from 100% to 0% state of charge for 1000 cycles while retaining 100% capacity.
- It will cycle a further 4,000 cycles (total 5,000 cycles) and still have 80% capacity remaining
- It will cycle a further 2,000 cycles (total 7,000 cycles) and still have 70% capacity still remaining.
A cycle for a lead acid battery is measured by charging the battery to 100% state of charge, then discharging to 50% state of charge.
- A lead acid battery will cycle from 100% to 50% state of charge for 600 to 700 cycles before it will permanently drop below 60% capacity, in other words, 10% usable capacity remaining before the battery you can no longer safely take any more power out.
You can use more of the available amp hours
A 100Ah lead acid battery can only give you a maximum of 50Ah of its available capacity before it drops below 12 volts under load. One of our 100Ah lithium batteries can give you 100Ah without a damaging voltage drop.
In 2011 we were one of the early adopters of lithium for RVs. Information that was available was confusing and inconsistent, so we decided to work it out for ourselves. The effort and expense paid off.
Many different chemistries come under the banner of 'lithium', but they all have different efficiencies and stability. It's important to know that not all lithium chemistries are suited to RV use.
A simple explanation of how lithium batteries work that explains their superior performance over lead acid batteries.