20,000 mAh li-ion battery + 12v-220v inverter?

I provide some stage lighting and video/laser equipment for rent and offer custom content for them on demand.

Sometimes customers want to see the device in action in a location where there is no power source nearby.

I’ve already asked the manufacturer of my laser light equipment to include a rechareable battery in one of the laser projectrors to use that one for presentations.
He’s put a 1000W 12v-220v inverter in it and a 10,000 mAh li-ion battery which allows to use the device with no power cable attached and it can be recharged. Hes also put a volt meter to have an idea how much battery life is left.

Now I’m thinking of putting these parts in a custom case and using that box to power any of my devices like this.
What do I need? Just a 10,000-20,000 mAh li-ion battery pack properly connected to a 1000W+ inverter, with a voltmeter on the cables that go from the battery to the inverter? Or something more?
Can I charge the li-ion while the inverter is on and the device is consuming power? I can do that with my laser projector right now, but I don’t know if the manufacturer has added something extra for that to work right.

The Li-ion battery requires specialised charging or you risk a fire. With the correct charger, you can use the inverter while charging.

You would probably require a sine wave inverter.

Weedpharma

Thank you. What do you mean by specialized charger? The one which supplies correct amount of current? Or something more? Because if its something more I don't know if even the stock one will be the "correct" one, being chinese and all.

Li-ion batteries are notorious for bursting into flames when not treated correctly.

Do Google search on charging the batteries.

Weedpharma

For a 10,000 mAH battery, you will want a industrial charger to charge quickly and safely.

Your 12V battery will be composed of three cells ("3S") with a charged voltage of 4.2V. If those three cells charge unevenly, e.g. one cell reaches 4.3V, then there's a risk of a nasty fire. A proper 3S lithium charger will provide the typical positive and negative charge leads plus another jack for four wires so that each cell's voltage can be monitored and balanced.

Due to the risks of fire with lithium batteries, it's typical for the battery to contain a "battery protection circuit" inside it to prevent over/under voltage and excess current draw. That will save you from those risks, but again without a balancing charger you'll never be able to charge the battery at a high rate and still keep each cell even and full.