Motorizing 7715 with 810

[genISD]

Hello

This is my first post here. I got 7715 from my childhood and just recently by a luck I got complete 810 motorizatioon set which can be used with 7715, according to instruction sheet. However I have no idea how to put battery box from 810. It's almost 7 studs wide (6 studs plus half a stud on every side - battery box thicker cover. I think I must build additinal train car from this battery box but grey is not so good looking. Have you ever tried using this approach?  

[Carrera124]

You need a battery car, e.g. the one which was used in 7722.

[genISD]

My idea was to build grey tender using battery box from 810.

[Reza]

Since the train 7715 is red and blue and if you insist on using this type of battery box, then you can find a black one or a blue one.

https://www.bricklink.com/v2/catalog/catalogitem.page?P=bb45c03&name=Electric 4.5V Battery Box 6 x 11 x 3 1/3 Type III Complete Assembly for 1-Prong & 2-Prong Connectors&category=[Electric, Battery Box]#T=C

https://www.bricklink.com/v2/catalog/catalogitem.page?P=bb45c02&name=Electric 4.5V Battery Box 6 x 11 x 3 Type II Complete Assembly for 1-Prong & 2-Prong Connectors&category=[Electric, Battery Box]#T=S&C=7&O={"color":7,"iconly":0}

If you live in Canada, I think I have one blue (and also black, I need to check) that I can ship to you. But the battery wagon for trains 7720 or 7722 is a better option (that Carrera124 suggested).

[Paperinik77pk]

You can copy the solution from some 70s lego sets (e.g. set 119) which used the black battery box, with some bricks on top of the battery box cover to emulate a tender.

The only problem is that the small steam locomotives of the 80s were intended as locotenders, so a tender is not too appropriate (but who cares...if it works!) :)

I personally use a modified red battery wagon from 7722. I simply changed the wheels from black to red (these were taken from a broken blue battery wagon) to match the color of train's wheels (all red). In order to reduce weight, I use C to AA battery adapters bought somewhere in China :)