Monday, March 19, 2012

Battery Choices for the Tidalforce Electric Bike to Replace Your Weak or Dying Front Hub Battery

I started on the above titled blog post shortly after posting part 1. However, after many words and multiple edits, I didn't think I could do justice to this vast/ever changing topic! I did a quick look to see if there was any site that had comprehensive and well researched information both theoretical and practical real-world knowledge. I came upon my good friend Justin Lemire-Elmore's excellent and highly recommended webiste, He has an excellent page on batteries and in particular, batteries for ebikes!

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:

  1. 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. 
  2. 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.
  3. They could be configured in a circular arrangement so that they fit into a hub battery.
  4. They had enough capacity (9AH) to give a medium range ride for the Tidalforce system.
  5. 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.
  6. They were readily available, albeit they were relatively expensive at the time (for higher quality cells).
  7. 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:
  1. They are heavier and bulkier than newer chemistries like lithium-ion (Li-Ion) or lithium polymer (LiPO).
  2. They had a relatively short cycle life (charge/discharge cycles) of about 250-300 cycles.
  3. They had a tendency to self-discharge if left unused.
  4. They had reduced capacity in cold temperatures.
  5. For greatest longevity, they need to be discharged and recharged completely every few months.
  6. 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:
  1. Lighter weight than NiMH
  2. Higher energy density (smaller size for same power).
  3. Higher weight to power ratio (see 1and 2 above)
  4. Very low self-discharge rate
  5. Longer cycle life (charge/discharge cycles) of about 400-500 cycles.
  6. Convenient 
The cons against Li-Ion are:
  1. Possibility of fire if mistreated.
  2. Requires a dedicated battery management system (BMS)
  3. Requires careful attention to charging (in case of #1)
  4. Typically, it's best to put the charger on a timer (to prevent #1)
  5. Must plan for possibility of #1
Thanks and more later!


  1. I saw your post about the Lifepo4 batteries for the Tidal force. Dont know if these will fit in the hub.

    1. The V-Power battery packs are way too large for the front hub of the Tidalforce bikes. They are very large and rectangular.