the key thing to consider regarding this idea is that
there is no combination of lithium cells/individual batteries
that naturally natively equal 12 volts..
packs such as this are rated at 12 volts because for a short
while when fully charged, they can equal or exceed 12 volts,
but they cannot sustain it.. the native voltage
of a single lithium battery/cell is typically 3.6 volts, so they have 3 cells
to make a "12 volt" pack because when freshly charged they are
more like 4.2 volts each.. sensitive equipment does not like
either the peak overvoltage, or the lower sustainable voltage
since they cannot sustain it, if you look closely at the specs,
for example they have settings for several voltages, and they
can GUARANTEE sustained voltage at 9 volts, or 5 volts, but
not at 12 volts. that is because the natural voltage of the cells
inside is greater than 9 volts or 6 volts, and so can be regulated
down for those levels lower than the natural voltage of the pack
so, briefly, they used to sell a 24 volt talentcell pack
and that had a guaranteed sustained voltage at lower
levels, like 12 volts 9 volts etc, while also being able to run
something at 24 volts for a good while.
however, the 24 volt packs with a 12 volt regulated "tap"
( i had looked at them awhile back ) were too bulky
to slip under the backpad, so i didn't get one.. they
quit making them in 24 volt packs
runtime for lithium packs is based on batteries in parallel..
so a homemade 12 volt regulated setup with 4 cells
that didn't run long enough for you would need to be
upgraded to an 8 cell pack (4 paired cells = 8 batteries)
devices that actually can run on anything from 10 to 14 volts
without hassle are what an "advertised 12 volt" pack like these are
targeted toward. Electronic devices like the Rolands are rather
sensitive and actually require a steady voltage that does not waver
or drop or exceed the needed voltage the device is designed for
the second issue is, a regulator circuit that can control
a custom 4 cell lithium pack may not be able to output
the AMPERAGE the device will draw, especially with the
volume all the way up
so if i take 4 individual lithium batteries (that kinda look like
big fat long AA batteries) and buy a plastic battery holder
for them then wire them to a regulator then wire a plug on
the regulator that fits into the bottom power socket of the Roland,
i would have a steady 12 volt power that the Roland would
be happy with and it would likely last longer than 10 AA NiMh
but if you were gonna be OK with a battery on your music stand and a
wire yea long could also just use a 12 volt sealed lead acid battery
which is for sure 12 volts and come in many sizes/amps
and actually, i have quite a few of my portable battery operated
PA setups and wireless gear and mixers being run from just such
lithium batteries, battery holders, and regulators.. some at 5 volts
some at 9 and some at 12, but those are all in cases or little amps
setups i could fit the stuff inside or velcro it on top
with the Roland, we have our back pocket, or slip a pack under the
backpad as the possible locations
when the FR3 came out, we found a nice flat pack NiMh 10 battery
pack that slipped nicely under the backpad that gave us good runtime
and ease of swapping out, so i understand why you want something like this..
Caps had one and i had one and we published the info way back and others
got them too.. but NiMh flat packs and accompanying chargers are
hard to find now..
www.talentcell.com
