Parallel charging

JamesC

Esteemed Pedelecer
Sep 1, 2007
435
5
Peterborough, UK
Hi, being new to electric bikes and keen to pick up tips I've been looking around the various contributions and topics, having just fitted my new SLA battery packs and put on charge. I was interested to look at batteries as a topic and noticed many experimenting with NiMh types. Fine for those who know and understand their characteristics but dangerous if not charged and monitored correctly. A sensible warning I noticed previously posted as a result of a fire. These batteries should be charge controlled as an individual series combination_ the characteristics being that as they reach their fully charged point (constant current of course) the terminal voltage begins to fall and this is when the charge should be terminated, and reduced to a low trickle charge state. If this situation is overlooked the cells will go into thermal runaway and eventually explode! I'm not familiar with bikes that use these NiMh cell packs, but i would not trust charging methods that don't detect a change in the charging characteristics_ most low voltage chargers either use dedicated micro controller devices and sometimes include thermistors as an added precaution should the charge not terminate. I've designed my own low voltage chargers using a combination of charge level termination, thermal sensing and time out. A bit belt and brases but better safe than sorry. Nothing wrong with experimenting and learning from the results but please be careful. Regards Merv
Merv, thanks for the reminder.

NiMH is certainly popular with the battery makers on the forum, and there have been a number of good threads discussing the means to do it.

As Flecc says, NiMH is less readily available now in the "new bike" market, making it difficult for some of the successful designs of 2006/07 that were based around the particular virtues of the NiMH battery.

Latest designs seem to be more in balance with the Li-ion technology, which is expected to develop in capability.

Meanwhile, there remains an aftersales market for replacement NiMH batteries.

It has been a huge difficulty for one of our ebike suppliers during 2007 in wanting to retain NiMH with the older spec bikes, but having difficulty getting supplies and support with this technology from the battery industry.

James
 

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