Take proper care of your expensive eBike batteries with some ground-rules, a schedule, and a good charger. Knowing how and when to charge your battery will save you money and let you enjoy riding your eBike more.
Help, my bike won’t turn on….
I’m a member of several MATE X and eBike groups on Facebook, and the most common battery-related question that gets asked, gets asked too late. It goes something like this:
“Why won’t my bike turn on? I didn’t use it for (3/4/5/6) months. I charge the battery and it says it’s full, but when I unplug the charger and try to turn on my bike, it won’t power up!”
(crying emoji)
Yeah sorry mate, that battery is dead as Disco. The individual cells inside the battery have lost all their power, and reached a point of no return.
Why did this happen?
Inside the battery it’s made up of of smaller batteries (cells), and their health/charge is maintained and monitored by a device inside the case called the Battery Management System (BMS). Its job is to:
- Tell your bike’s display how much power is left
- Ensure the cells aren’t charged over max capacity (bang! fire!)
- Ensure the cells don’t drop below minimum safe capacity (cell death)
- Ignore cells that are no longer performing. This is usually done in groups rather than individual cells, so one dead cell can mean several healthy ones also get taken out of service.
Your BMS has decided that the cells inside the battery are all underperforming, and is refusing to let power go in or out of the cells. The exact reason is a bit beyond the scope of this post, but let’s just say that if a cell’s charge drops below a certain percentage, it is considered dead. If it actually reaches 0%, the chemistry inside the cell will not receive charge.
How to keep your battery healthy
It’s hard to think of anything in this world that benefits from living life too fast or too slow, to the max or the very minimum, too much food or too little. Same goes for batteries. Without going in to too many nerdy details, here are some ground rules:
1. Cycles (number of charges/discharges) – how much to charge?
Batteries are built differently, so I can’t say how many cycles they have. What I can say is the best way to ensure a longer total lifespan for your battery is to avoid charging it above 80%. The actual benefits are probably documented scientifically somewhere, but is it worth it? I personally don’t do the 80% thing, unless I’m storing the battery for long periods. This is because I run out of power faster, can’t go as far, and the bike performs so much better when the battery can dish out the volts. Yeah I could save money by never going above 80, but fun isn’t free. It’s up to you.
You need to charge it to 100% every 6-8 recharges. This is called balancing, and allows the BMS to more accurately know and report the true maximum capacity or percentage of the battery.
2. How low can you go?
If you’re running a MATE X with the standard display, the battery reaches about 15%-20% when your display says 0%. So that’s a safety limit designed to prevent damage to the battery. The battery’s BMS should also prevent the bike from drawing power from the battery when the cells are too drained. As a rule, avoid letting the battery go below 20% charge. Again: The bike should automatically shut down the motor when this happens, so you can let it get to zero – it’s actually about 15-20%.
3. How to charge? What is a “smart charger”?
MATE X bikes have been sold with many different chargers over the years. None of them have a cooling fan, and they eventually die due to constant overheating and cooling down. This is where our eBike Parts Combo Pro Charger comes into the picture. You can get smart chargers from others, sure, but very few support both 48V and 52V batteries. Here are the features in short:
- 110V (US) and 220V (EU) switch
- Interchangeable plugs at both ends for different AC power plugs and different batteries.
- Digital LED display shows current voltage and how many Amps are being input.
- 48V/52V switch for different batteris
- Supports 17.5Ah and 20Ah batteries with 58.8V capacity
- 80/90/100 percent charge setting dial
- 1A to 5A speed setting dial
- Fan for cooling internal components
Percentage
The charger has a percent dial that allows you to stop charging at 80%, 90% or 100% depending on what you prefer. For this to work, I recommend inserting your key and turning it all the way to the ON position, so the BMS and the charger can talk to each other. Some batteries have an incompatible BMS that will not correctly tell the charger to stop, so you get this issue where it stops and starts charging all the time. Easily remedied by turning the key to ON.
Amps
The 1-5A setting can be a considered a “speed setting”. So…why not always charge as fast as possible? Because higher speed is less accurate, meaning the individual cells aren’t charged as precisely. But more importantly, fast charging stresses the cells and will result in a shorter total lifespan for your battery. If you have the time, always charge at 1 A or 2A rather than 5A. It may take 10 hours for a large capacity battery to charge fully if it’s empty, but it’s the one thing that really makes a difference and protects your battery. There are exception like Tesla cells, which are designed to handle fast charging.
4. When to charge
You can basically charge modern Lithium Ion batteries as needed – with one exception. Don’t charge an ice-cold battery. Let it reach room temperature before you start. I may also add that you should check your peak hours and electricity prices, to avoid nasty surprise bills.
5. Long-term storage: The battery killer
For long term storage it’s a good idea to charge to 70%, and keep it indoors at room temperature. The battery will lose power slowly during storage, and it’s important to recharge it periodically to avoid it dropping below the minimum safe limit, where cells begin to die off. I personally make sure the battery key is turned all the way to “off” as the BMS consumes power.
What I do is charge to 70% capacity, let the battery sit for 3 weeks, then plug it in to the smart charger to see how many volts are left. I actually have a recurring reminder in my phone to avoid forgetting. Each battery is labelled 1, 2, 3, 4 to avoid confusion.
I let the batteries charge for at least 20 minutes at 1 Amp, longer if it hasn’t reached 70% yet. This way I’m sure each cell has been “woken up” – even if that means going above 70%. That’s why I start at 70% – gives me room to charge a bit over while avoiding 80%, as batteries don’t like being stored for long periods with more than 80% power.
Percentage to Volts:
These charts may help you determine how much charge is in your battery. Please be aware that these values are approximate.
52V batteries:
| Percent | Volts |
|---|---|
| 100 | 58.6 – 58.8 |
| 90 | 57 |
| 80 | 55.5 |
| 70 | 53.8 |
| 20 | 45 |
| 15 | 43 |
48V batteries:
| Percent | Volts |
|---|---|
| 100 | 54.6 |
| 90 | 53 |
| 80 | 52.5 |
| 70 | 48.8 |
| 20 | 42 |
| 15 | 41 |