Roomba 400 NiCD and NiMH batteries

rracct3 · Joined: 02 Jul 2008 Posts: 1

I bought 2 new 400 roombas, and both have different batteries - NiCD and NiMH.

Which one is the newer? I felt ripped off with the NiCD batteries because usually NiCD don't run as long on a charge.

However, are there any advantages with the NiCD?

Fraggboy · Posted: July 3, 2008, 4:47 am Post subject:

rracct3, Welcome to RoombaReview!! :D

The Newer technology is the NiMH. I don't think one can tell if a battery is brand new(Not used). I can't come up with any advantages with the NiCD technology.

Sorry :(

Snippet from ApexBattery wrote: Difference between Nickel Cadmium (NiCad) and Nickel Metal Hydride (NIMH) batteries?
Both NiCad and NiMH batteries are rechargeable. The main difference between the two is the fact that NIMH batteries offer higher energy densities than NiCads. In other words, pound for pound, NIMH delivers approximately 30% more capacity than its NiCad counterpart. What this translates into is increased runtime from the battery with no additional bulk. NIMH also offers another major advantage: NiCad batteries tend to suffer from what is called a "memory effect". What this means is that when a NiCad battery is only partially discharged before charging, the battery "forgets" that it has the capacity to further discharge all the way down.

To illustrate: If you, on a regular basis, fully charge your battery and then use only 40% of its capacity before the next recharge, eventually the battery will become unaware of its extra 60% capacity which had remained unused. Your battery will remain functional, but only at 40% of its original capacity.

The way to avoid the dreaded "memory effect" is to fully cycle your NiCad battery at least once a month. In other words, fully discharge your battery and then fully charge it.

Batteries can be discharged by allowing the device to run on the battery until it ceases to function. This will insure your battery remains healthy. NIMH batteries are "memory free" - they do not suffer from this affliction. Thus, if you have a NIMH battery, the only time it is necessary to cycle it is during its initial use and after a long storage period. This is done to "exercise" the battery and bring it up to full capacity.

Source of Snippet

glo69 · Posted: July 3, 2008, 12:14 pm Post subject:

A question and a comment.

Quote: I bought 2 new 400 roombas, and both have different batteries - NiCD and NiMH. What makes you think that one of the batteries is NiCd. As far as I know, none of the 4 series Roombas ever came with NiCd batteries. I think some of the very , very early Roombas started with NiCd, but nothing recent. There is an unethical company selling NiCd replacement cell kits, but the cells have to be installed by the customer.

Quote: NIMH batteries are "memory free" - they do not suffer from this affliction. I don't know how old this information is but it is not accurate. NiMH does have a memory problem, just not as bad as NiCd. It was only very, very early in NiMH production that this claim was made, but now NiMH reconditioning is completely accepted as needing deep discharge occasionally to break up the crystallization known as *memory*. Here is a much better (It's old, but not that old, Chris :) ) book to quote http://www.buchmann.ca/default.asp

Jeff Carver · Joined: 19 Jan 2008 Posts: 117 Location: Massachusetts

My first Roomba (Pro Elite) had a NiCd battery. I recently got careless and bought a couple of replacement NiCd sets instead of Nimh. I installed one for a Discovery; it's okay, gets about 55 minutes on a run, which is enough for what I use that Roomba for. But I wouldn't intentionally buy a NiCd. (These were very inexpensive.)