stepping up 12V powerbanks to 30V DC

i bought some RC Lipo battery packs to power a speaker system but since then i've moved and my new landlords have thrown a fit about me charging them on the premises because of the (small) potential fire risk so one possibility im considering is using a powerbank or 2 instead as they have no problem with those.
my problem is that the amplifier requires 30V but most slim powerbanks put out a maximum of 12V so could i either safely step up to 30V from 12V or join 2 powerbanks to step up from 24V?

If your landlord is concerned it usually means you have a quite oversized battery pack.
I had a set of 6 20Ah packs that required to be charged quite often and there were no concerns from my landlord.
But it might be the way you presented the problem ;)

I was already aware of the risks of modern batteries since the first mobile phones and laptops started to make smoking news headlines.
There are several options to make a landlord happy by adding some safeties:
Get a dedicated charger bag, if you can't find one at a reasonable price make one.
Fire blankets are made from glass fibres and available quite cheap.
Fireproof yarn of the same material can be found on Ebay.
Make a bag to store your batteries and another one to be used while charging.
If you want something more solid make a steel box with small holes in the top.
Place another sheet of metal with stands to cover the top from the inside.
Like a wood oven you then have a baffle plate deflecting the flames and the hot gas can escape through the holes.
If done correctly both methods are even suited for indoor use, although I would prefer the metal box if you want to keep and charge inside.

By the way: most powerbanks use LiPO's ,so the fire risk would be the same ;)

ambientvoid (author)  Downunder35m24 days ago
2x 10000mah 4s lipo's, not what i would consider especially sizeable, i think it was partly my fault for being too honest about anything i had that could be a potential fire risk when i moved in and partly because they'd never seen a lipo pack before. that's an interesting point about identical batteries in powerbanks that i hadn't considered, i'm going to pass that point on to them tomorrow. i've misplaced my charging bag but they're pretty cheap to replace and i also made myself a small metal charging box out of one of those little cash/lock box things, it hasn't got a baffle plate yet but that's a good idea...