A123 for 48 Volt Controller, will this work..
I have 3x dewalt 36v batteries and a 48 volt controller. I was thinking that if I split the connection between 5 cells in one of the batteries that would give 18 volts, which when connected to one 36v battery in series (total 54v), might be within tolerances of the 48v controller I have.
To allow charging of the modified battery with a standard dewalt charger, I will use a switch to re-establish the connection between each 5 cells.
To keep each 5 cells with similar consumption sync with each other, I would run each 1 and 1/2 batteries in parallel so current usage should be the same.
Does anybody see a failure in this logic.
I see no problem doing what you purpose I would like to let you know the DeWalt pack is really 33 volts not 36. So if you take 1.5 batteries your voltage would be 49.5 volts which should work fine with a 48-volt controller. When I charge my DeWalt packs I normally get a full charge reading of about 35.4-volts but when I apply a load to them they drop to about 33.3-volts at full charge. I think you are on the right track. Let us know how it works.
My Bicycle Pages
You can't really split these packs and expect to use the stock BMS and charger. DeWalt has announced a 5-cell (16.5V nominal) A123 pack they'll be releasing in the future, and that will be a good thing to use in series.
Meanwhile, you can wire up a switch to split a pack for discharge but reconnect it for charging. Cut a tab in half, then solder a switch & wire inbetween the two halves.