I just ordered a custom BattEQ unit for the 5 battery XM-2000. They are basically taking the 6 battery version (which is also now available) and modifying it to work with 5 batteries by soldering it somewhere to disable that last battery. They're charging $199 for this version. Unfortunately, they're not going to give it the limited 2 year warranty because it hasn't been road tested, but they seem confident that it will work.
The price is $40 cheaper than purchasing 4 Powercheqs, so that's a selling point. I was swayed by Andrew's dissatisfaction with the Powercheqs that he mentioned in a post and thought I'd give these a try. As long as it works, I'll be happy. I'll keep ya posted.
If anybody else is interested in the 5 or 6 battery version of BattEQ, here is the contact info you'll need:
Brian E. Precious
Business Development Manager
SmartSpark Energy Systems
b.precious [at] SmartSparkEnergy.com
Moss Green "Charger" ebike