Wow. Good to hear you were able to contain the damage and no one was hurt. Some of those charger/booster boxes use AGM (a lead/acid battery) instead of lithium batteries. I have two with AGMs. It should be noted that all of them, regardless of battery type, can cause a fire under the right circumstances.
If you store them in with other tools that can bounce around on the road and cause a short, a fire is almost certain. Not saying that’s what happened here, just that that is a hazard to be aware of.
Thank you, @mikemc35, for posting and reminding us all to be careful both with lithium batteries and all electrical devices, and especially for reminding us all to have a fire extinguisher in our rigs.