When should I charge my battery?

[duggie]

Hi folks. I'm sure this will have been covered, but my computer is old and it seems my browser will not let me browse to find battery charging posts. Anyway, I'm new to ebikes and just been using my first ebike....love it...., but now I'm thinking about charging it. My question is in three parts.

a) Does the charge in the battery affect the performance of the bike (is a fully charged the same as a half charged)?

b) When should I charge......when the battery is half charged, or does it not matter?

c) What are some dos and don'ts for good battery maintenance? Thanks

My battery is a 48v type. Fully charged it shows about 52v. Now it is 46v. Also, I tried to use my multimeter to measure the battery. I clearly made contact with the battery terminals but couldn't get any reading. I had the multimeter set to 20v DC. Am I doing something wrong?

 

[indianajo]

For longest life people say to charge between 85% full and 20% full. Once a month they say to balance charge to 100%. I balance charge every 3 months and my battery is 4 1/2 years old with maybe 250 charges.
To measure 52 v meter should be set to 200 v scale.
I find battery just as peppy at 1/2 charge as full. Around 25% performance up hills with full load of groceries suffers.

 

[duggie]

indianajo.......Thanks for that chart. I'll take it down to 25%. I did try with 200v setting, and just tried again, but nothing. My meter is working, so I just don't know, but I'll go off the control panel readout. Thanks

 

[6zfshdb]

A. Unless your bike's controller is voltage regulated (most are not) you will see diminished assist as the voltage drops. This is easily compensated by raising the PAS a level a notch or two.

B. Indianajoe covered this in his post above.

C. The only thing I can add here is to store the battery for long periods at 40 to 60% charge level in a heated space. Never charge it when It's been exposed to sub freezing or high temperatures for an extended length of time. let it reach room temperature first.

Protect the battery from physical abuse. If you transport the bike. Remove the battery and place it out of harms way in your vehicle, preferably in a protective container. I've seen several batteries damaged by transporting them on the back seat. A sudden stop can send them flying or get damaged by some other object. Never charge a battery that has physical damage without first getting it checked out.

The BMS puts some batteries into a "sleep" state after a period of disuse. This removes voltage from the output terminals. Put the battery on charge for 30 seconds or so to "wake" it.

Welcome to the forum! You've come to the right place to ask your questions!

 

[harryS]

In my opinion, you're better off charging the bike up to your 80% or 90% level after every ride. Avoiding battery operation under the 40-50% level, if your usage allows it, is even less stress on the chemicals.

I doubt you could get down much under 25% anyway. That's 42-43 volts on a 48V battery, and almost all ebikes will shut down near that point, for long term battery safety/longevity.

 

[tomjasz]

For longest life people say to charge between 85% full and 20% full. Once a month they say to balance charge to 100%. I balance charge every 3 months and my battery is 4 1/2 years old with maybe 250 charges.
To measure 52 v meter should be set to 200 v scale.
I find battery just as peppy at 1/2 charge as full. Around 25% performance up hills with full load of groceries suffers.

Amazing how often I see my edited chart. I might be famous...
Originally posted on Luna's forum and highlighted by me in a 2015 post. It's a small world! But I wouldn't want to paint it...

 

[Elkman]

The type of batteries used on most bikes cannot have their healh or SOC measured with a voltmeter. They are designed to provide a high voltage output until they are exhausted. I use a special ZTS pulse load tester with my smaller lithium batteries to determine their health.

Best to follow the manufacturer's recommendations if you can find them. What is not good is to top them off after every ride. Many lithium can be fully discharged with no problems and have an internal electronic limiter to reserve 5-10 percent so they can be recharged. Some batteries when taken down to 0% SOC can not be recharged by the user.

 

[AHicks]

I think most will advise against running the battery at the lower end of it's capacity/range in the name of being battery friendly/trying to extend the battery's useful lifetime. While it's possible to run the battery down under 43v or so, you're going to have to baby it to avoid having it shut down on you. These concepts in mind, I will generally charge when I start seeing 46v readings.

 

[HCooke]

What instructions came with the bike? My bike's instructions says to charge completely after each ride. Bike and battery on my bike is warranted for 5 years.

 

[duggie]

I seem to have picked up some mixed messages about lithium batteries over the years with drills, circular saws, phones, etc. I used to believe that they will develop a memory for what is low if you keep topping them up before they are well down, so i don't want to reduce the capacity in this way. I have some c-type batteries I use a lot for radios, and the charger comes with a button to drain them totally before recharging, and manufacturer recommends this every now and then to achieve max capacity. My bike, from China, came with no manual, well not one for my bike, so i can't go off that. I once ran a drill down and really squeezed every drop out, and that wouldn't recharge for a good day or so. I once had a hedge trimmer that went flat from no use and that had to be thrown away. So I don't know. I'll just take it down below half and then top up. But I would love there to be a really good documentary about batteries, how they work and maintenance. Reckon we all need one of those the way things are going.

 

[indianajo]

The battery I referred to in post 2, I ran it into the red light of the controller on the last big hill most trips of the uphill leg of my 27 mile commute. The controller would shut off briefly. When I got to destination the battery stopped was 25% volts. That was the first 2 1/2 years. Then I got a Mac12t motor that used less electricity on the trip. No more running to shutdown. The battery, 4 1/2 years old, is still okay. I wouldn't be to worried about running a LiIon battery down to the bottom (briefly). Batteries with an internal computer may be programmed to shut down near zero and force purchase of a new battery. Mine just has a BMS that shuts off each stack from the input if it reaches 100% voltage.
Post 7 is non-sensical. Manufacturer's recommendation on bike batteries is in ****ese if available at all. The cell datasheets aren't even available in english. According to wikipedia SOC is science operation center.

 

[fauconnier]

Never heard about lithium batteries "memory", it's something that affect nickel batteries.
The usual storage voltage ( less deterioration ) is just over the nominal voltage, in your case approx. 49v but voltage is not a true measure of capacity. I personally rarely go under 46v ( at rest) but I consider 43v to be safe. See the graphic, a 48v battery is 13S, 13x 1 cell voltage. Voltage drop very fast after 3.6 per cell. After my ride, I bring back my battery to 49v, storage value, if I don't need it.
Lithium batteries don't like to be full charge. I charge my batteries full if needed for a long ride, but I try to coordinate the end of the charging period with my departure.

 

[AHicks]

That "memory" thing dates back a couple of generations in battery tech to the days when Ni-CAD was king. Those you need to be mindful of. Newer stuff pretty much makes that unnecessary.

 

[tomjasz]

I seem to have picked up some mixed messages about lithium batteries over the years with drills, circular saws, phones, etc. I used to believe that they will develop a memory for what is low if you keep topping them up before they are well down, so i don't want to reduce the capacity in this way. I have some c-type batteries I use a lot for radios, and the charger comes with a button to drain them totally before recharging, and manufacturer recommends this every now and then to achieve max capacity. My bike, from China, came with no manual, well not one for my bike, so i can't go off that. I once ran a drill down and really squeezed every drop out, and that wouldn't recharge for a good day or so. I once had a hedge trimmer that went flat from no use and that had to be thrown away. So I don't know. I'll just take it down below half and then top up. But I would love there to be a really good documentary about batteries, how they work and maintenance. Reckon we all need one of those the way things are going.

Thankfully there is an LVC. low voltage cutout. Without which dangerously low voltages would kill the pack prematurely. I have a high quality and expensive Polly pack with 35E cells. Never used. I forgot about it and it self discharged and the cells dropped below 2.7v (1.8v)and it’s now a boat anchor. I have battery repair welder and all the tools and spare parts, but it’s not recoverable.