You could always buy an inexpensive lead-acid battery and charger and jumper the battery into your system.
I did this a couple of months ago, and then had a battery-no-longer-charging problem, about which I started another thread here on vansairforce. Eventually -- with the help of others on vansairforce -- I determined that my problem was two-fold: a bad Ducati Rectifier/Regulator, and a blown fuse hidden and soldered inside the Switch & Fuse Module.
I now wonder whether my use of a jumpered battery to operate my avionics was the initial cause of my problem. This is what I
speculate; if you disagree, please say so.
1. Even though I thought my external battery was well-charged, I suspect it wasn't as fully charged as the battery in my plane. Thus, instead of the external battery feeding the internal battery as I used the avionics, the internal battery was actually feeding the external battery and was losing voltage as a result.
2. When I next started the engine in order to fly, I suspect the internal battery was weak, and thus, the Ducati worked extra hard in order to power my avionics and recharge the plane's battery at the same time. That, I suspect, is what killed the Ducati.
3. While trouble-shooting the charging problem, I pulled and replaced the visible fuses, one at a time, to see whether one of my plane's components was drawing excessive amps. I also pulled and replaced my Dynon Wifi Adapters. In order to see the effect this had on amps, my Dynon had to be on, so my Master Switch was on. I suspect this may have been why the fuse that's hidden and soldered inside the Switch & Fuse Module blew.
Again, if this doesn't seem correct, please so.
But this is why I've been looking for something that can be charged at home and then attached to my plane's battery (I have pigtail wires attached to the battery) that will -- with certainty -- charge, rather than drain, my plane's battery.