Introduction to Lithium
Lithium motorcycle batteries boast loads of advantages over lead-acid motorcycle batteries. They used to be more than twice the price of a regular lead-acid battery but over the past two years prices have tumbled and they’re now comparable in cost to a quality lead-acid battery.
Lithium Iron Phosphate (LiFePO4) batteries have a power density that is 3 to 4 times higher than an equivalent lead-acid battery. That means that to delivery the same cranking capacity as a lead-acid battery, a lithium one can be 3 to 4 times lighter than the lead-acid.
A lithium motorcycle battery can also deliver this cranking ability when the battery is down to around 10-15% of peak charge, but a lead-acid battery’s ability to crank diminishes rapidly when the battery is not at – or near – fully charged status.
Because lithium is more expensive than lead, manufacturers set up their lithium batteries to deliver the same or higher cranking ability than a lead-acid but a lithium batter will have a low amp-hour (Ah) rating. Let’s say a battery has an Ah rating of 10Ah, this means it can delivery 1-amp of power for 10 hours. If this rating is lower, let’s say 7Ah, then it can delivery 1-amp of power for 7 hours. This reduced Ah capacity of a lithium batter won’t affect its ability to crank over an engine when the battery is fully charged but it will affect how many auxiliary current draws (i.e. USB ports, heated grips, fog lights etc) that your battery can handle. For most bikers, this isn’t a problem because they’re not using these things with the engine switched off.
Now that the prices of these batteries have dropped, there’s never been a better time to upgrade your bike’s battery. With a lithium battery you’ll save weight and say goodbye to those dead-battery woes.
This guide is written to quickly help you understand the benefits of a lithium motorcycle battery, dispel the common myths and help you avoid the common pitfalls.
Lithium Motorcycle Battery Pros
- Lithium motorcycle batteries have a power density 3 to 4 times higher than lead acid, therefore the battery can be much lighter, often 25% of the weight of a lead-acid equivalent
- Lithium batteries don’t contain any acid and therefore can’t leak
- They have a cranking power 3 to 4 times that of a lead acid battery
- Lithium batteries have a lower self-discharge rate compared to lead-acid batteries, roughly 3-5% per month
- Lithium batteries charge faster than a standard battery (roughly 3 hours compared to 12 hours for a standard)
- Lithium batteries can last between 5 to 10 years, compared to 2 to 3 for a lead-acid, making them far better value for money
Lithium Motorcycle Battery Cons
- You won’t be able to safely charge a lithium battery with a lead-acid battery charger
- Lithium batteries don’t perform well at temperatures close to or below freezing
- They are roughly 30% more expensive than an equivalent lead-acid battery
- A truly flat lithium motorcycle battery cannot be recovered but it takes a long time for them to self-discharge
- A charger which isn’t designed for Lithium batteries will most likely damage the battery through too much voltage
Lithium vs Lead Acid Weight Comparsion
Lithium batteries are SO much lighter than a regular motorcycle battery. When we hand them to customers to compare the difference, they can’t quite believe it.
The picture above shows a YTX9-BS, a very common motorbike battery. The lithium equivalent weighs just 738g, which is 2.3kg lighter than the Yuasa lead-acid battery that came as the original battery in this Triumph Street Triple. If you’re chasing weight savings, lithium batteries offer great bang for your buck. It’s also good to know they’ll last twice as long as a lead-acid and they have around 30% more cranking power.
Common motorcycle batteries and their weights
YTX9-BS – Lead acid weight 3.1kg, Lithium weight 0.75kg. Weight saving of 2.35kg
YTZ10S – Lead acid weight 3.2kg, Lithium weight 0.9kg. Weight saving of 2.3kg
YT12B-BS – Lead acid weight 4.1kg, Lithium weight 0.95kg. Weight saving of 3.15kg
YTX14-BS – Lead acid weight 0.9kg, Lithium weight 4.6kg. Weight saving of 3.7kg
YTX20CH-BS – Lead acid weight 1.2kg, Lithium weight 6.1kg. Weight saving of 4.9kg
Don’t lithium motorcycle batteries catch fire?
If you look on internet forums where people are talking about lithium motorcycle batteries, it won’t be too long before someone posts a picture of a melted battery or even worse, a bike that’s on fire.
Yes, some lithium batteries can catch on fire.
In order to explain this, we first need to understand that lithium batteries can have different properties. Rather confusingly there are two common types of lithium batteries: lithium-iron and lithium-ion.
A lithium-iron (LiFePo4) battery has a slight advantage over the Lithium-ion (LiCoO2) battery in terms of safety. We sell lithium batteries which use iron phosphate (LiFePo4) as the cathode material and use the lithium-polymer process in their manufacture. As a result, they can neither go up in flames nor explode in normal operation.
If you’ve ever seen a picture of a lithium battery in flames or melted, it’s highly likely this is a Li-ion battery not a Li-iron. The Li-ion is more volatile and may suffer thermal runaway. The Li-ion is not a good choice for a motorcycle or car battery as it is not as chemically stable and heats up faster under similar charging conditions.
So why can they melt?
If you fit a quality lithium-iron battery, like the JMT ones we sell, there is no greater risk of it melting or catching fire than a standard lead-acid battery. However you can still kill your lithium battery by hooking it up to a regular battery charger. These can overcharge the lithium battery, which is far more sensitive to voltage than a lead-acid battery. Fortunately you can buy motorcycle battery chargers that can charge both lead-acid and lithium batteries.
Some lithium batteries also don’t come with a BMS (Battery Management System, a small circuit board built into the battery housing that regulates the charge). In some cases, a non BMS lithium battery will charge its cells at different, uncontrolled rates, causing a cell to be overcharged and therefore overheat. With a Li-ion battery this could lead to a fire or explosion. With a LiFePo4 battery the worst scenario is that the battery will warp a bit and you’ll essentially turn it into an expensive doorstop. This is why it’s important not to use a normal charger on a lithium battery.
Some lithium batteries don’t have short circuit protection built in, i.e. a fuse to shut it down should things start to go awry and these batteries can fail if overworked.
Your motorcycle or scooter’s charging system won’t kill or overheat a lithium motorcycle battery as they charge at a lower voltage than a wall-plug charger. But if you’re in any doubt, put a voltmeter across your battery when the bike is running and if it’s reading over 14.6 volts, it risks overcharging your lithium battery. The vast majority of bikes will charge at 13.8v to 14.4v maximum.
Never try and desulphate a lithium battery
Some battery chargers have a desulphate mode, which pumps in a higher voltage and usually higher amps into a battery. This is for lead-acid batteries only and is designed to physically break down the oxidisation of the lead cells, to enable them to work more efficiently.
Lithium batteries don’t sulphate like lead-acid ones do. Charging a lithium battery with a regular charger is risky at best (you have a fairly high chance of damaging your battery) but using a desulphate mode is asking for trouble. You will kill your battery and you might even make it explode. Be warned.
Google a bit harder and you’ll see that standard lead-acid batteries can and do melt or explode, if they’re over charged, damaged or not properly vented. It’s a rare occasion for any battery to fail in such a spectacular way but as is the way these days; if it does, it’ll no doubt end up being plastered around the internet.
Do lithium batteries have quicker charging times?
Yes, typically a lithium motorcycle battery will charge around 4 to 5 times as quickly as an equivalent lead-acid, but this does vary. The charge time depends on whether your lithium battery has a BMS (Battery Management System) which will optimise the charge rate.
You cannot charge a lithium motorcycle battery with a regular batter charger. A lithium battery typically charges well at 13.8v to 14.4v. A lead-acid motorcycle battery charger will charge at 14.4+v which will rapidly cause heat build-up and cause the lithium battery to fail.
Do lithium batteries have a longer service life than lead acid?
Yes, a lithium battery with a built in BMS should last a minimum of 5 years and up to 10 years. By comparison, over one-third of lead acid batteries will fail within 3 years. The failure rate of the JMT lithium batteries that we sell is around 2% in the first 2 years and our JMT batteries are covered by a 24-month warranty for peace of mind.
What are Cold Cranking Amps (CCA)?
CCA is mentioned on a lot of battery specifications. It stands for Cold Cranking Amps. In short, the higher the number the more ‘kick’ your battery has. So if you have a large v-twin engine, you’ll need a battery with a high CCA. If you have a single-cylinder 125cc motorcycle, the CCA required is much lower.
CCA is interesting but don’t get hung up on it. Battery manufacturers, like JMT produce their lithium batteries with a casing that is pretty much exactly the same size as the lead-acid battery that came in your bike and the model numbers are virtually identical too, to make it easy for you to find the right one.
What are Amp hours?
In battery terms, Amp hours is the storage capacity of your battery. The one area that Lithium batteries ‘lose out’ to the old lead-acid ones is that their Ah rating is lower, usually around 40%. So if a lead-acid battery could keep the headlights on for 4 hours before the battery went flat, a lithium could keep them on for just under 2 hours.
However the reduced Ah rating has little significance in the real world. Unless you regularly operate the bike’s electrics without the engine on or, for some reason, you like to leave the ignition on with the headlights running while the engine’s off.
Lithium Motorcycle Batteries – Frequently Asked Questions
Are lithium batteries smaller?
They can be. There are two types of lithium batteries: ones that are as small as they can be and ones that are designed to fit into the same caddy your old lead-acid came from. They both weigh about the same. We stock the latter as it means you can easily remove your old battery and insert your new lighter lithium one. The smaller lithium batteries are designed more for race bikes or customs, where size as well as weight matters. But if you put one of these in your normal bike, you’ll have to fashion some packing to hold the battery in place, which is a huge faff.
Can you jumpstart a lithium motorcycle battery?
This is risky and can cause the battery to fail. If you do jump start a motorcycle battery, connect it in parallel, not series. Connecting the battery in series will make it 24 volts, which will cause the BMS to trigger. Do not try and jump the battery from a vehicle that is running. A far safer method is to connect your lithium battery to a dedicated charger for 5 minutes, which should be enough to start the bike.
Do lithium batteries need a special charger?
Yes they do. Lithium batteries are sensitive to voltage and a lead-acid charger uses a voltage that is too high. We sell this NOCO Genius motorcycle battery charger which charges both lead-acid and lithium batteries.
Should I trickle charge my lithium battery?
You can but you really don’t need to. Lithium batteries don’t like to be trickle-charged in the way a lead-acid does and frankly, they don’t need to be. Lithium batteries don’t lose their charge like a lead acid would. In 6 months, a lead-acid would lose around 50% of its voltage, mainly due to sulphation of the lead plates. However a lithium battery would lose around 15-20% of its charge in this time. The other crucial point is that a lead-acid battery has virtually no cranking ability when it reaches 50% charge state whereas a lithium battery can crank all the way down to 10%. So a lithium battery sat for 12 months will most likely still start your bike, a lead-acid very probably won’t. If you run a tracker or alarm from your bike’s battery and therefore you have battery draw, if your bike is sat and not being run for months, then you can top up the battery with a charger but unplug it once it is done.
Why do motorcycle batteries die so quickly?
There are many reasons your motorcycle battery will die but the main reasons are: Faulty charging system, Faulty battery, Parasitic draw, Damaged wiring and short journeys.
If you only do short journeys, your bike might not have time to properly charge the battery back up to where it needs to be. Lead-acid batteries rapidly lose their cranking ability when their charge state is lower than 50%. If you also add in any of the other factors above and you’re going to get through a lot of batteries. A faulty charging system is often due to your regulator rectifier or generator giving up the ghost. If these don’t work or aren’t working as efficiently as they should, then your battery won’t be getting the rate of charge it needs. Your reg/rec can overheat (especially if you commute) and this can kill it. To rule this out, test your voltage across the battery when the bike is running. It should be at least 13.5 volts at 2,000rpm. Parasitic draw is when things like alarms, trackers, or anything else you have wired into your bike uses power when the bike’s engine is off. In these cases it makes sense to use a trickle charger which will counter the draw. Damaged wiring can cause your charging system to become less efficient and it can also cause the bike to ‘leak’ power in certain cases, like when exposed wiring gets wet. Finally, a faulty battery can be the issue. Batteries have a given shelf life and most lead-acid batteries will last between 2 and 3 years. Vibrations from the bike can damage the battery’s internals and sulphation can also cause the battery to become inefficient. It makes sense to connect your battery to a trickle charger and also desulphate it form time to time to prolong its life.
Can you recharge a dead lithium motorcycle battery?
Yes you can. Lithium batteries can reach around 3v before they are no longer recoverable. If your lithium battery won’t start your bike, connect it to a battery charger for an hour and that will give the battery enough juice to start your bike. If the voltage of the battery is seriously low, i.e. between 2.5 and 3v, remove the battery from the bike and put it on a lithium charger. It may take up to two days but in most cases it will be recoverable.
Do lithium batteries die if not used?
Yes, like all batteries they lose charge but their self-discharge rate is far lower than a lead-acid battery. If you are not using the bike for a period of more than a month, you might nee a lithium charger to hand to boost the battery prior to using the bike. If you are not using the bike for a prolonger period of time, you can disconnect the battery but you don’t need to connect it to a trickle charger as it will barely lose any charge over a period of a few months.
At what voltage is a lithium battery dead?
Between 2.5v to 3v is the point where a lithium motorcycle battery is not recoverable.
Can you revive a dead motorcycle battery?
In most cases yes, because ‘dead’ isn’t definitive. With a lead acid battery, 24 hours on a desulphation charger should recover it enough. If your battery can power the bike’s instruments or lights but not crank the engine over, it is most likely a battery that can be ‘brought back from the dead’
Can you desulphate a lithium motorcycle battery?
No because lithium batteries don’t sulphate.