Extending Battery Life of Bicycle Batteries

barnstar2077

So, just ordered a new battery for my bike, but not sure what to do for optimal longevity of the batteries life.

It is a 36v/19ah battery from cyclotricity, which I assume is lithium ion.

When I bought the last one they told me to completely run down the battery before recharging to extend it's life (as in fewer recharges), but googling, it says that recharging at 20% is better.

Also, I have heard they degrade over time anyway, even if you don't use them, so am I wasting my time trying to make it last longer anyway?

Thoughts?

PhilNunya

Follow the 80/20 rule, i.e. don't charge over 80% and don't discharge below 20%. This of course limits you to 60% usable capacity but you can break the rule occasionally e.g 90/10 if your trip necessitates it. Never charge the battery until it has cooled to room temperature which could be a couple of hours.

Nasqueron

Batteries do degrade over time though they should have a warranty on level/capacity after x number of charges with caveats about how many and what type you did. Conventional wisdom was charge 20-80% to reduce battery wear but you might be better posting on an ebike forum as there aren't that many active posters on here for this subject so you may only get 2-3 replies and maybe none have used that brand.

barnstar2077

PhilNunya said:

Follow the 80/20 rule, i.e. don't charge over 80% and don't discharge below 20%. This of course limits you to 60% usable capacity but you can break the rule occasionally e.g 90/10 if your trip necessitates it. Never charge the battery until it has cooled to room temperature which could be a couple of hours.

This is difficult to do, as it doesn't tell you the percentage of charge it has as it is charging, the  light just goes green when it is completed.

Also, as it takes six or aeven hours to charge to full when the battery is new it has to be left charging over night.

I will post on a dedicated cycling forum as suggested and see what people think.

MilesT6060842

Not showing percentage charge on the battery or the charging device is a bit cr*p. 

Presumably you can see the charge state on the bike itself, and then work out how much % per hour you get when charging. 

There are inexpensive timer plugs that can be simply set to turn off after a set number of hours to help with charge management;  also Horstmann makes wall switches which do this (30/60/120 and 2/4/6), intended for use with e.g. immersion heaters and heating boost in public spaces but can be built into a simple battery charge control setup if you have electrical wiring knowledge (don't update your house wiring with one of these yourself unless you have electricians qualifications, but could safely build a special extension cable with a Horstmann controller "inline" mounted into a surface mount back box and then ask a a friendly electrician to check your work and do a PAT test if they will do that for you at low cost). 

I'm not 100% sure that all modern rechargeable battery chemistries follow the 80/20 rule exactly, and some of the better battery systems have internal battery management which controls rate and amount of charge to maximise battery life, but based on the description the safe assumption is 80/20 with a simplistic charger, also ensure you try and avoid the battery getting unnecessarily hot while charging: charge in a cooler area, away from radiators, with good airflow, maybe even make a special "charging stand" to improve airflow while charging--use basic hot air flow physics as a inspiration.  And make sure there is a smoke detector alarm and a electricals CO2 fire extinguisher nearby just in case, ideally make it possible to remove a possibly burning battery outside as quickly as possible without directly touching the battery.