my 64 plate b-max was completely flat last wk end when i charged battery it came up transmission error code take it to dealership for service straight away ,so bristol s m had it for 3 days and said there was a couple of errors which they sorted said battery is ok ,so i had it back ,with this i turned engine over everyday as ive got work van ,then tonite battery completely flat and showing transmission service code any one have any ideas what the problem is