Making NiMH Battery Packs

[meb]

I'm planning on building an assortment of small interchangeable & interconnectable NiMH battery packs. Most of my ebikes are 24V SLA, with a single 36V and some 12 V systems and some incomplete 48V systems.

Anyone know the number of cells most "24 Volt" NiMH electric bike battery packs use?

I've heard reports ranging from from 20 to 24.

Likewise, what charging voltages and shutoff voltages do the smart chargers use?

[Abneycat]

Well, single NiMH batteries are typically 1.2v, so at 24v you'd be needing 20 batteries (that is, if you were designing your pack with batteries such as 10ah D cells for instance, where you would be able to meet your amp requirements with only one set of batteries)

One of the *biggest* problems with trying to home make your own NiMH pack is that many of the batteries for sale out there don't have the proper output capacity to work with many e-bike systems.

http://www.batteryspace.com/index.asp?PageAction=VIEWCATS&Category=337

There are some basic specs for some typical chargers here on this page for NiMH.

[meb]

Well, single NiMH batteries are typically 1.2v, so at 24v you'd be needing 20 batteries (that is, if you were designing your pack with batteries such as 10ah D cells for instance, where you would be able to meet your amp requirements with only one set of batteries)

One of the *biggest* problems with trying to home make your own NiMH pack is that many of the batteries for sale out there don't have the proper output capacity to work with many e-bike systems.

http://www.batteryspace.com/index.asp?PageAction=VIEWCATS&Category=337

There are some basic specs for some typical chargers here on this page for NiMH.

I'm needing actual, not approximate voltages. "1 1/2 volt" NiMH cells when fully charged put out 1.2-1.25 volts fully charged. Likewise, SLA smart 24 V chargers put out 28+ volts unloaded while charging and shutoff at 27.6 volts-the voltage is higher than the name suggests. I'm looking for the actual voltages, not the named voltages.

Building a pack with the wrong number of cells would result in overcharged or undercharged situations.

Likewise, I'm needing more precise voltage information than a ballpark 24 V.

[Abneycat]

Well, 20 D cells is whats in the packs that ebikes.ca sells for 24v batteries, which is what I used to double check the statement that I made on those packs.

If you wanted the most help, I would try asking at http://visforvoltage.org/
Some of the members there have extensive experience, and could probably provide you the numbers you need.

[jerryt]

Try this
http://endless-sphere.com/forums/viewtopic.php?f=14&t=2570&hilit=+nimh+voltage

Try a search if you don't get your answer

Also try http://www.rcgroups.com/forums/index.php

[dwainedibbly]

Or get a voltmeter & check a few cells.