This came from my upgraded Lectric Leopard with only 1300 miles that was parted out before its time. It was a result of not having any space in my conversion, which netted me a strong DC-DC converter that takes up very little space.
It is nothing more than a cold plate made from two flat .095" thick aluminum plates, separated by 1/8" spacers and serpentine paths of three Ø1/8" copper tubes, all epoxied and screwed together. The tubes are joined together at the ends and have Ø1/4" quick-connect swivel fittings for coolant lines, which in my case was just a branch off my controller cooling loop.
On one side of the cold plate is the two coolant fittings and a 200 W Vicor BatMod that accepts 100-200 VDC input. It's controlled with a DIY project board that was based on Vicor app notes. It plugs directly onto the Vicor posts. It drives the matching triple MegaMod on the other side of the cold plate in a master-slave arrangement.
I couldn't be happier with how it turned out. The fact that it is driven by a BatMod means it acts like a real battery charger, not just a dumb DC-DC. Vicor modules are hyper-reliable, and the two used in this device alone would cost over $1000 retail. (Yes, you can find them surplus, but it can take years before you come across the right ones.) You're not likely to find a more power-dense DC-DC than this, especially at this price.
Price: $200 Shipping weight: 6 lbs. (estimate)
Payment by Paypal or cash in person. I'm in the Philly Metro area. Shipping is extra.