The old Rev113 Cruz Neato XV system board firmware does not support the SetConfig BatteryType USB command. The command may be accepted but does not change the charging algorithm as it does on the newer Rev64 Binky system board.
It is possible to make, or to buy, lithium replacements for the Rev113 board, but it is more complicated than with the lithium charging algorithm.
Compare with replacing the system board with the newer type.
The difference between these procedures is that NiMh charging terminates by thermistor temperature readings rising at the end of charge, and the Lithium charging terminates when the voltage reaches a maximum defined for the type of lithium used (this voltage will be close that specified for tripping over-voltage protection boards). Two methods can be used to translate lithium voltage into temperature for the NiMh charger, making an adapter. For the Neato XV a four-series of lithium cells is used, often with two parallel for capacity, terminating at 16.8v (two-series in each of two compartments, two packs). LiFePo4 cells have a lower voltage, and a five series would be used, with a different terminating voltage. NiMh is a 12 series for Neato XV, 1.2v per cell.
To translate the voltage into heat, a custom circuit can be made which generates a synthetic thermistor reading rising at the terminal voltage. Such circuits are in the commercial replacement lithium battery packs. I made such a circuit for LiFePo4 batteries shown at robotreviews.com, thread "lithium ion revisited".
Caution: when such circuits fail, from any mistake, the NiMh charger will go to its maximum voltage from the docking plates, which damaged a Neato system board. Additional over-voltage cut out circuits for the charger were then added. Another such adapter was made in Germany but i cannot translate the technical article or schematic. As the thermistor resistance falls with higher temperatures, it is sufficient to bypass the thermistor or fixed resistor with a transistor to signal heating to the NiMh charger. Raising temperature 10C at the maximum lithium voltage, read by a comparator component, is fairly simple as electronics goes. The specific thermistor characteristics in Neato are posted in the robotreviews thread. Temperature is reported over USB as Neato uses these signals.
A second method was used in the original German battery project at roboter-forum.com, "lithium ion upgrade". A pack balancer circuit, which evens out the charge on all cells in a pack, will get hot when the battery is full, bypassing the charging current, and can be thermally in contact with the standard thermistor. simulating the NIMh behavior. A custom balancer circuit was manufactured by the German user when the original parts were discontinued by makers. Many new balancer circuits with more advanced IC's do not carry a large enough balancing current to heat sufficiently. However, a battery was made for the Botvac (lower 12v system), with LiFePo4 batteries, where a standard commercial balancing board was enhanced by adding resistors in parallel (lowering the original) to increase the current. (The Botvac also does not support the SetConfig USB command.) See thread at robotreviews.com
http://www.robotreviews.com/chat/viewtopic.php?f=20&t=19149Note the particular balancers used there were for LiFePo4 voltages, not regular lithium ion. Other balancers are sold.
Balancer boards do not always include over-voltage protection which should be added with regular protection boards, important with Lithium Ion, and its fire hazard. The newer and safer LiNMC chemistry cells such as used here in the Rev64 Cruz project are best.
The balancing circuit method requires experimentation to insure sufficient heating. The adapter circuit method allows precise design of the operation, but needs custom, hobby electronics construction and knowledge. A German engineer with his own Neato lithium circuit helped identify the useful component for detecting voltage, the ICL7665 comparator I think (see the robotreviews thread). His circuit is not published at roboter-forum, as he only makes hand drawn sketches.
External NiMh pack chargers can be used to test DIY lithium battery packs with adapter methods of either type, before potential damage to Neato systems. I recommend the over-voltage protection such as I used, to protect those expensive parts.
Individual cell chargers can be used to initially balance the cells for assembling a pack. The best balance is achieved by fully discharging the cells first, through a suitable load resistor; caution under-voltage, excess discharge can damage cells. Under-voltage protection is included in protection boards. Instead of chargers, battery testers are available which cycle individual cells to measure their capacity.
The price of NiMh Neato batteries has fallen over years. Savings from making a DIY battery may be limited. Lithium will last longer than the NIMh.
The Botvac LifePo4 project used a newer cell with higher capacity than those I used to make an experimental LiFePo4 pack for the XV. The older cells I used have insufficient capacity and too many would be needed to fit in the XV (three parallel, 15 in all). The Botvac cells might work in two parallel, 10 in all. Regular lithium typically uses 8, four series two parallel.
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