Lead Vs. Lithium Batteries – What Its All About
Lead-Acid Batteries: If It Ain’t Broke Don’t Fix It?
Invented in 1859 by French physicist Gaston Planté, lead-acid batteries have been the standard power storage medium in powersports since, well, forever. Lead-acid batteries are cheap and they work. Yes they will start you bike if you look after them, but that good old black lump of toxic chemicals has a few problems. Let’s start with the chemistry, lead-acid. It’s no secret that lead is quite toxic to your brain. I hope you are not eating your bike battery, but considering most of us ride high-performance motorcycles, a big chunk of heavy lead is the last thing you want on your bike. Let’s look at the second part: Acid. Yes, these batteries contain sulphuric acid. In the old-old days, batteries were not sealed. They had a liquid acid sloshing around it them. Occasionally, you had to top the level off with water as the acid electrolyte boiled off when the battery charged. If you happened to drop your motorcycle, it was always a pleasure to pick it up and have acid spilling out from the overflow tube all over you and your bike. Not only that but, while charging, the battery would give off hydrogen gas. It was not uncommon for the area around the battery to simply be rotted out from all this mess. You can still get the cheap unsealed batteries, but most motorcycles have the AGM, sealed or “Maintenance Free” batteries for this reason.
The term “Maintenance Free” is of course not correct. You may not need to add water (and there is no way to do it if you had too), but they still require some maintenance if you expect to get any performance or life out of your battery. Lead-Acid batteries have a significant self-discharge, which means that if left alone they will simply go dead. Also, if you don’t charge you batteries every couple of weeks, they degrade though a process called sulfation. This lead to the introduction of various battery maintenance products, often called “Battery Tenders” which automatically charge and maintain the battery if you plug it in every time you leave the bike sit for a week or two. These products do help, but it is not uncommon for batteries to last only two seasons if you don’t religiously maintain them. Don’t expect more than four years of service out of a good quality battery even if it is fully maintained.
So let’s review. Lead-Acid batteries are toxic, heavy, have to be maintained and don’t last very long. Basically, they suck. Fortunately, we have an alternative.
Enter Lithium-Phosphate: Not Your Dad’s Battery
Lithium-Ion batteries have been in production since the mid 1990’s and have been the key technology enabler for most of the portable electronic devices you own and love today. Their flexibility and energy density is currently unmatched. I experimented with lithium batteries several years ago by converting a DeWalt power tool battery which then used the innovative A123 Nanophosphate battery. These are not the same batteries that are in your cell phone. This chemistry accepts much more abuse, have longer life and have a much higher discharge rate which is required to spin the starter on you bike. The results? It worked great.
The LiFePO4 (Lithium-Iron-Phosphate) technology does not have the same energy density as some of the other chemistries, but it is much better suited to requirements of a motorcycle. The individual cell voltage matches the charging voltage of your bike at 3.3V per cell. Wired up four cells in series, that gives us 13.2V (most systems are not really 12V but between 13.5V and 14.5V). On my DRZ400 test mule, I was able to use 4 cells in series and they had no problem starting the bike at any time. On that bike the benefits were substantial. The stock battery location was up high near the back of the bike, opposite the muffler. Because of the much smaller size of the 4-cell lithium battery, I was able to move the location closer to the center of the bike and remove 2.6kg (6lbs) of weight. You could definitely feel the difference in the handling. Typically, Lithium batteries are 1/3 the weight of a lead-acid battery. If you want to remove weight from you bike, installing a lithium battery is the best bang for the buck. Motorcycle and automotive manufacturers are starting to see the benefits of a lighter lithium starter battery with KTM notably offering a lithium battery as standard on certain bikes.
It’s All Good Right?
Yes, you can quickly shed pounds of useless weight from your motorcycle in minutes by installing a Lithium battery. Not only that, but they truly are maintenance free. The LiFePO4 has a very low internal discharge rate which means even after sitting around for a year, your motorcycle should crank over no problem without having to keep it on a trickle charger. Since there is no acid, and no fumes, and are much lighter you can mount the battery pack in any angle or location you choose. This brings up some interesting options. Lithium batteries don’t like heat, so stay away from the hot areas, but because they can be physically smaller than regular batteries you have more choices as to where you can put it. My four cell DRZ battery fit nicely in the airbox. Technically my Husaberg 450 could also get away with a four cell pack, but I choose to install an eight cell pack (2S2P) to have twice the capacity. The Berg is fuel injected, has no kick starter and is a beast to start so I was willing to sacrifice the extra 200g of cells for the peace of mind of not getting stranded somewhere in the wilds of Northern Ontario. But, if you have a smaller bike and a kick starter, I can see no reason not to go with the smaller, lighter and cheaper four cell models. If you want to install it into the stock battery location, you can simply stuff foam around it to take up the extra space. But it’s not all puppy dogs and rainbows, there are a few issues as well.
Not all battery cells are exactly the same. Because of this, over time, the voltages each cell provides can vary. This causes some cells to be over charged while others can be undercharged. My custom Husaberg battery is a simple design with no battery management. After a couple seasons of riding, I have checked the voltages on each cell and there have been no issues. I think this is because the battery is never discharged that much. If you constantly have to crank you bike forever to get it started, cell balance might be a problem.
Most newer lithium batteries models have an internal balancing circuit which will automatically correct this. Some older ones require an external balancer be plugged in. Lithium batteries do not like to be totally discharged. Again, the newer batteries will automatically cut out if the voltage gets low to avoid damaging the cells. Another thing to be aware of is cold temperatures. If its cold outside, and your bike cranks over like the battery is dead, be patient, because it isn’t! If you leave the bike on for a couple minutes, the battery will warm up from the load and provide full power.
The lithium battery manufactures advertise the higher cranking power available over the equivalent lead-acid battery. There is some truth to this, but is really not an equivalent comparison. Generally, a properly sized lithium battery will crank your bike faster, but not for as long. They can provide a higher current but usually have a lower amp-hour rating. Is this a problem? I have never found the lower capacity to be an issue. Once you bike is running, it’s running. Just don’t leave the key on (if so equipped) while it’s not running or the lithium battery will go dead faster than the lead-acid one.
Lithium batteries are quite a bit more expensive than there lead counterparts, but I truly believe that the economics are even or favor the lithium batteries. The simple fact is that they last much longer without having to require any maintenance. You will be lucky to get two seasons out of a cheap lead-acid battery, and not much more for a more costly AGM version. A good Lithium battery that is not abused (overcharged, under-charged, over heated) will last at least 4 years. If you take into the weight savings for the money invested, then it’s a no-brainer.
Most Lithium motorcycle batteries use the 18650 form factor which is a standard cylindrical cell. Some use prismatic cells, which are flat packs like your cell phone uses. In my experience, stay away from those, they don’t seem to last as long as the regular 18650 packs.
So we have discovered that traditional lead-acid batteries are heavy, toxic and will go dead in no time if you don’t keep them on a charger. Lithium batteries can be smaller, much lighter (1/3 the weight), and truly maintenance free. If you care about the weight of your motorcycle, there is no easier way to get the lead out than to replace your 160 year old battery technology with something from this century.