Substituting 3 'C Type' Batteries for a single '9V' Battery??

[RandomGrinch]

Just get a few rechargeable C cells. Sorted.

Plus a charger!

...but watch the battery capacity - the Ni-MH could have between 2500 and 5000 mAh @ 3.6V total for the 3 cells.
Whereas some extra work to accommodate a LiPo powerbank, could get up to 20000mAh at 5V and everyone has a USB charger to hand!

 

[lettuce]

Ignoring the losses from a resistor/Stepdown converter (and again comparing like for like batteries with similar energy densities), 3 x C batteries have a volume of approx 80'000mm³ and a single PP3 has a volume of 21'000mm³ (even less if it is a battery derived from AAAA's!).
A PP3 will not last as long, or be cheaper.

Either as above, stick with USB cable, or a far easier modification may be to use a USB power bank.

Yeah oddly on socket on the back of the device is a barrel connector (5.5mm i believe) so the supplied cable is a USB to barrel cable and not the usual USB to micro or USB to USB C

C type batteries are not expensive, and last a long time

https://www.aldi.co.uk/activ-energy-c-batteries-pack-of-12/p/000000467854500

Also in Screwfix and Wilko I think

My mistake there actually type D batteries, though i guess they wont be that much more. My issue maybe though how long they actually last in the device. If they don't last more than a week then its a money pit and not worth it.

I may have though of a solution however, as i can hide the majority of the cable under the fridge and use a bit of hose pipe to cover the few inches of exposed cable and hot glue the cable within the hose pipe leave just enough of the barrel to plug into the food dispenser the hose pipe will be wedge under the fridge and floor so shouldn't be able to be pulled out

 

[mattylad]

You cold use another USB power supply, simply coat the lead in hot sauce, the dog soon learns not to chew it.
Mine certainly leant not to touch anything coated in it.

 

[Alec_t]

a 9v would work out cheaper and possible last much longer if used with a resistor no???

No. The mAh capacity of a 9V PP3 battery is much less than that of an AA or C cell, so the PP3 would have a short life.

C type batteries are not expensive, and last a long time

They would last a long time if genuine C; but many are actually AA cells in C-size casings.