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Let us first look around the exterior of the battery pack. Figure 1 provides a view of the pack's upper-side, and trailing side (orientation considered as if installed in the robot). On the trailing face, the built-in spring-release tab can be seen spanning the central region. To release the battery from the robot's grip, one must depress that central zone while rotating the battery about pivot-points provided by the pair of "yellow-tab" nubbins (to be seen in Figures 2, and 3) and their receptacles in the upper-chassis.
Figure 1. Top and Trailing Faces of the Pack
The photo of Figure 2 shows the battery-pack's left-end view profile. It is obvious from the shape of that profile that cell-centers are on a parallelogram-grid {not a square-grid) to close-pack them. When you get down to it, about the only things that appear to match -- between this battery and Roomba's -- are the pack's voltage output (still 14.4Vdc, NOM.), and the use of NiMH cells.
Figure 2. Left-End of the Battery Pack
By flipping the pack over, (as if 'roll' rotated -- its left-end is now to our right) the pack's label and two pairs of sockets can be seen (Figure 3). Those yellow-tabs, referred to a moment ago, can also be seen near the ends of the case, on the pack's forward face.
Figure 3. Connector-Side of Battery-Pack
The pair of female-contacts at the viewer's RHS, those with the slot between them, carry cell-temperature data (this pack's thermistor measured 3.02 k-ohms at 22.2C (72F)); while the pair of sockets at the viewer's LHS make battery-power available to the robot. The outboard-socket, at far-left, is the 'positive' side, and its inboard neighbor is the 'power-return', zero-volts-reference, socket.
In addition to the internal temperature sensor, it is a fairly secure assumption that the 're-settable fuse' (in series with the positive lead on Roomba-battery's ) has been carried forward into Scooba's battery-pack.
Have you noticed, iRobot has provided no screws holding the battery's case-halves together? Boy howdy! That's going to make it tougher on owners that need to re-build the pack! Roger, in the UK, knows he will someday have to re-build one or more Scooba batteries. With that self-prodding, he has started investigating what one may do to re-new duff cells.
Roger got the joint separated far enough to see four internal clips that would hold the case together if some bonding agent were not also holding it all together. The front and sides of the case have lap-joints, with the top lapping over the bottom. The rear edge of the joint is a tongue and groove affair which was most difficult to separate. Clarifying the bonding, the cells have been glued into the case, and no realistic amount of prying the covers apart will break its hold.
There is no sense in continuing an investigation that may harm a working battery, so any sort of forced entry will be delayed until the battery asks for it. Here are some thoughts as to why the cells have been bonded together so thoroughly in this battery:
Owners will never know for certain what the reason for bonding is. But, let's say that someone eventually gets inside; what will they likely find? Using the battery-case's shape and external dimensions (41x73x142 mm, not including the connector-boss), it is possible to conclude that the 12 cells will be of size "4/3 Fat A", and arrayed in two layers. Each layer will be three rows of series-connected cell-pairs. The two layers will be seen nested by having offset them, fore & aft, by one cell-radius. '4/3 Fat A' cells have an approximate diameter of 18- mm, and a length of 67-mm, vs. Roomba's Sub-C cells with 23-mm diameter, and 43- mm length.
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