Flat battery

Go and buy a inteligent battery charger, that is one which gives you the option to leave the battery on trickle charge. If you let the forum know what model motorhome you have further advice could be forth coming from owners of similar models.

peedee

why can't you jump start it from your car?  Depending on how flat your battery is, depends on whether a smart charger will start to charge it .... they often need to see a certain voltage to start off with.

I notice you say      It is parked outside our flat roadside

This may prevent you from charging with a charger which needs a mains supply.

I'm not sure why it isn't starting from a jump start from your car. If your van battery is very flat, you will need to connect the jump leads between the 2 vehicles and run the engine in the car at a rate faster than tick over for at least 5 mins to get some charge into the vans battery. Then it may well start.

How do you prevent it in the future ? Take your van for at least a 30 min run every week or perhaps invest in a small solar panel..

If its like mine you need to read the M/H instructions carefully. My elct board slows charging of the habitation batteries by default. However you can switch to "vehicle battery" at a touch. Only found out when I had your problem. Now whenever I put on 240 V from the house mains I switch to ensure vehicle battery also charges. Doesn't your bank account goodies have breakdown? Mine does and it includes home assistance.

are your jump leads of a good quality? There are a lot of cheap aluminium or thin copper wire sets out there, that just aren't capable of delivering the high starting amperage.

Leaving the slave car running for a short while should boost up the vehicle to assist with starting, but do make sure that nothing is left switched on or you will just waste your time.

When a battery lets you down, it's either down to something being left on or end of life is near. Some batteries can self-discharge over a period of time but not to the point that a boost won't start a vehicle. 

When a battery lets you down, it's time to start thinking about replacement.

another thought - is the starter or engine seized?

and being pedantic, from my college days, "you only get flat batteries by running over then - batteries that are low on voltage are discharged"!🤔

Two ideas for the future – 1. Take M’Home out for a run on a regular basis. 2. If your M’home isn’t going to be run regularly then you could consider a solar panel to charge the leisure battery & a battery transfer unit to transfer power from the leisure battery [when it is full] to the vehicle battery.

Is  the  inability  to  jump  start  your  'van  due  to  not  being  sure  of  where  the  battery  is  ??

If  that's  your  problem  --  read  the  vehicle  h/book  carefully  'cos  it  should  tell  you  where  to  connect  the  jump  leads  under  the  bonnet.  There  have  made  arrangements  for  this  very  problem  !!

Or  if  you  just  cannot  get  enough  waft  from  your  Mazdas  battery  can  you  make  the  connections  and  then  run the  Mazda  for  a  while  to  give  'm  both  a  bit  of  ooomph.

B

You can buy a heavy duty charger with jump start facility or better (and cheaper) still find a local mobile mechanic who has one. This happened to me once when we due to go off touring. The problem with jump starting from a car battery is that the current needed to start a battery for a 2 litre plus Diesel engine is way beyond what a normal car can put out unless you have an equivalent sized engine eg a Landrover.
If the battery is too far gone (sulfated) even driving around to recharge it won't work and you will need a new one.

After 10 days is the OP still scratching their head at the roadside or is the OP having trouble replying to the helpful advice given on here?

Without stars to guide us we will never know if this was a new poster (I think it was).