Chassis Battery

I have a five year old Scepter and have replaced the chasis batteries five times. Luckily, the first time Monaco replaced under warranty, the remainder were replaced under warranty by the shop that services the coach. Each time the batteries tested totally dead. After the fourth set, they asked to have the coach to check out the electrical system and found nothing wrong. Even with the battery cut off swich off, there is still a samll drain on the chassis batteries for the various engine and transmission modules. I switched to storage with plug in facilities and still had a problem. Service shop checked with Monaco and discovered that the chassis batteries only charge when engine is running, so being plugged in makes no difference. Monaco offfered a replacement module to charge the chassis batteries while on shore power, but it was less expensive to have the shop instal a trickle charger. No problems since. Amazing what they leave out of the owner's manual. Good Lcuk.