It actually works in our test API for anyone. Check it:
Make a card:
$curl https://api.balancedpayments.com/cards \
-u ak-test-2qEM0Znvd8LIVbZ01LbFHvHgab4fkNr3c: \
-d name="Johannes Bach" \
-d number=4342561111111118 \
-d expiration_month=05 \
-d expiration_year=2017
The 'credit' link in the response is that comes back is '/cards/CC2mEWYlYvod2E1w3TJHOiGh/credits'. So we push:
$ curl https://api.balancedpayments.com/cards/CC2mEWYlYvod2E1w3TJHOiGh/credits \
-u ak-test-2qEM0Znvd8LIVbZ01LbFHvHgab4fkNr3c: \
-d amount=10000
We will turn it on _in production_ for people in the beta period. Some customers have already integrated it in test!