Thank you Justin!
Here's what I came up with before punting to Justin's excellent article above!
This is a follow-up blog posting on my first post on how to use an external battery with a Tidalforce electric bike.
Here, I'll outline the many choices you have available to use a 3rd party battery to replace your worn out or dying Tidalforce front hub battery.
Nickel-Metal Hydride or NiMH
First, the battery type used by Wavecrest Labs, creators of the Tidalforce electric bike is called Nickel-Metal Hydride or NiMH for short. This was a pretty good choice for the Tidalforce bike at the time (early to mid 2000s).
The pros for Nickel-metal hydride are:
- They were made from 30 1.2 Volt D sized batteries and good quality NiMH batteries can indeed put out a lot of current when needed.
- They didn't need to be babied too much since they didn't have the dreaded "memory effect" of nickel-cadmium or Ni-CAD batteries.
- They could be configured in a circular arrangement so that they fit into a hub battery.
- They had enough capacity (9AH) to give a medium range ride for the Tidalforce system.
- They were lighter than lead acid batteries and didn't have the inherent problems of lead acid batteries (Weight, Peukert effect, limited lifespan, can't be kept left in a discharged state) for electric bikes.
- They were readily available, albeit they were relatively expensive at the time (for higher quality cells).
- They were a very "safe" chemistry since there were few reports of what seemed like spontaneous combustion issues as we've seen from other battery types.
The cons against nickel-metal hydride are:
- They are heavier and bulkier than newer chemistries like lithium-ion (Li-Ion) or lithium polymer (LiPO).
- They had a relatively short cycle life (charge/discharge cycles) of about 250-300 cycles.
- They had a tendency to self-discharge if left unused.
- They had reduced capacity in cold temperatures.
- For greatest longevity, they need to be discharged and recharged completely every few months.
- If you have parallel packs of NiMH, you need to balance them occasionally.
Lithium Ion or Li-Ion
Lithium ion (Li-Ion) is a newer type of battery and has several advantages over NiMH.
The Pros for Li-Ion are:
The Pros for Li-Ion are:
- Lighter weight than NiMH
- Higher energy density (smaller size for same power).
- Higher weight to power ratio (see 1and 2 above)
- Very low self-discharge rate
- Longer cycle life (charge/discharge cycles) of about 400-500 cycles.
The cons against Li-Ion are:
- Possibility of fire if mistreated.
- Requires a dedicated battery management system (BMS)
- Requires careful attention to charging (in case of #1)
- Typically, it's best to put the charger on a timer (to prevent #1)
- Must plan for possibility of #1
Thanks and more later!