The batteries in this car go flat after some weeks non-use. Next time I leave it, I intend to attach a trickle charger. Do I need to disconnect any leads? Do I connect across both batteries or just one?
You won't do any harm by connecting a trickle charger while the battery is in circuit, I would assume that if it has two batteries they are connected in parallel so connecting to one will charge both.
You won't do any harm by connecting a trickle charger while the battery is in circuit, I would assume that if it has two batteries they are connected in parallel so connecting to one will charge both.