PEV Battery Maintenance and Health

PEV Battery Maintenance and Health

We asked you what you wanted to know about battery maintenance and health! We got a lot of great responses, so we put together this guide to help answer some of the most common questions!

Should I avoid draining my battery all the way? Will it damage my battery?

No, it is not damaging to your battery, but it is also not that simple. All cells coming from the manufacturer are rated to certain standards. For example a cell might be rated for 500 cycles. This would be under the assumption that you are charging each cell to 4.2V (Volts) and discharging to 2.8V. If the cells go lower than 2.8V it can start causing significant damage to the cell, but the battery management system (BMS) in the device prevents this from happening. So as long as your BMS is working properly, draining your battery all the way is not damaging the battery according to the manufacturers rating. 

Here is the caveat to all of that. If you want to extend the cycle life of your battery as much as possible, it is healthier to never drain or charge the battery all the way. When the cells are at an extreme (all the way full or all the way empty) they will degrade faster - but not faster than the manufacturer expects them to. (More on charging to 100% later)


What percentage should I store my board over the winter?

You will want to store your board not based on percent, but based on Voltage. Just below nominal Voltage is going to be the healthiest for your battery. Nominal voltage for lithium-ion cells is 3.6V. 

To calculate the best storage Voltage, you multiply your target cell Voltage by the number of cells in series in your battery pack. So let's do an example with a Onewheel XR. The battery has 15 cell groups in series, so you multiply 3.6*15 to get 54V. The lowest voltage you would want to store at per-series is 3.4V, so 3.4*15 = 51V. So for winter storage, you will want to store your Onewheel XR battery between 51V - 54V.

 

How long should I keep my board fully charged without riding?

There is no magic number with this question. The longer you leave your board at 100%, the more impact it will have, as the strain on the cells wears them down faster. If you plan to charge and then ride the next day, the convenience it offers you will almost certainty outweigh the detriment. 

 

Is it okay to leave my board plugged in all the time?

You should not leave your board plugged in all the time. Doing this is not any more unhealthy for the battery than leaving it stored at 100%, but it introduces a general safety risk. You should never leave electronic devices charging while unattended.

 

How bad is fast charging actually for your board in the long term?

On the cell manufacturer’s data sheet, they will recommend a certain number of cycles based around a max charge rate. Anything above that rate will cause significant degradation for the batteries cycle life. With health in mind, most of our chargers fall below the max charge rate possible, as to maintain cycle life. It is true that the faster you charge, the faster your battery will degrade, but it will not degrade faster than the manufacturer rates it for. If you want to get the benefits of fast charging but minimize any detriment, only use your fast charger when you need to! We recommend to use fast chargers as a secondary charger as opposed to a replacement for your stock one.

 

What is balance changing?

Cells have variances in their capacity, and the BMS works to even that out. This happens at the end of the charge unless your BMS has active balancing (most do not). When you charge to 100% battery, that is actually about 95% if the battery is healthy. That 0%-95% range is where 99% of your battery's energy will come from. The top 5% is where you will see balancing activity, which is why you might have noticed it sometimes takes longer to charge that last 5%.

So you might be wondering: Earlier we said charging to 100% isn’t as healthy, but now we are saying you need to charge to 100% to balance - so what do I do if I want to to be as healthy as possible? You can navigate this by charging to 100% right before you plan to leave again. As an example: You get home from a ride with 20% left and you’re probably not going to ride again for a few days. You charge your board up to 80% and unplug it (if you are using a Variable Rapid Charger you can set the charge dial to 80%). A few days pass, and before leaving on your ride, you plug it in again to charge to full. Once you’re full you head out!

 

How often should I balance charge?

The more you balance charge, the less energy will be required when charging and balancing on a day to day basis. Balance charging can be a preventative measure - it keeps the cells more in-line long term and helps counter imbalance issues before they even happen. How often you should balance charge can really depend on what you ride, but in general we recommend once every 10 cycles. It is done balance charging when all the cell Voltages are even. 

 

What if my cells balance lower than 4.2V such as 4.16V, or are not all perfectly the same?

This is okay and your battery is still perfectly healthy. Sometimes on the data sheet manufacturers will provide acceptable capacity variations. The BMS does a pretty good job at balancing all of that out, but in general if they are all within 0.05V, there is no need to worry. As your battery ages there is a concept called cell drift where the values will start to move overtime. These variations are generally insignificant and reflect an aging battery. 

 

Is there an ideal temperature for battery storage?

In general, you always want to leave your batteries in room temperature locations. If you leave your battery in the trunk of a car on a hot day, that is not going to be an issue if it is only for a short time. Long term you will want to avoid leaving your battery in places with extreme temperature fluctuations, such as an unheated garage during the winter. 

 

We hope you found this helpful! If you have any questions you can always reach out to us at support@chibatterysystems.com


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