Hi Luc, Yes to get the full output of these amplifiers (70 or 100w depending upon model) - you need to run them on 16V - so a LIPO 4S battery.
I’ve found any more than 3 watts drive is not necessary, so an increase for 3 watts to even 40 or 50 watts is a big jump.
There are now some new kits quoting 180 or even 200 watts output but I suspect they will really kill the battery when portable! The increased signal over the 70 watt model is less than one S-Point in any case.
73 Ed.
UPDATE 29/10/2020:
Similar Chinese amplifiers that use the same PC board. Some using a power module rather than the two power MOSfets (mounted in the same place) are now advertised as kits or ready built producing either 180 or 220 watts - some need a 24v DC supply at many amps I expect. Some claim 180watts at 13.8v. I can’t see these being intended for “backpack portable” - more likely for shack use as they are sensitive to bad VSWR. Interesting that it’s still the same design, however.
https://www.ebay.co.uk/itm/180W-Linear-Power-Amplifier-Amp-Kit-For-Transceiver-Intercom-Radio-HF-FM-Ham-SZ/164293911961?
MiNi 200W HF Power Amplifier Shortwave Power Amplifier Unassemble | eBay?
Perhaps it’s good timing that the cheap spectrum analysers are now available out of China - to look at what off-frequency signals these higher-powered amplifiers are producing?