I read someplace that all battery makers (Every one of them) lie about the amperage rating of the batteries they make. The best you can hope to get out of even the newest battery is 75% to 80% of its amp ratings.

As far as the trickle charge for the jump boxes if it doesn’t have a good controller to cut off the charge (and they don’t) it will overcharge the batteries. When a battery is fully charged, the charge needs to be turned off, even a small charge is too much.