I've seen a few "battery powered milking machines" on the market. Most are small, handheld, cheap and very appealing but they lack pulsation which is a very important part to a proper milking machines, mostly of maintain udder health.
A battery powered milking machine is possible with your traditional milking machine setups. You just need the right parts to make it work. I've done the legwork here and below you will see specifications listed out for what you might need to run your milker off of a battery.
AGM Deep Cycle Battery 35 ah (amp-hour) or more is ideal.
1000watt Modified Sine Wave inverter. Higher is better but this is the minimum you will generally need to get one of these pumps starting up and keep it running.
A smart battery charger. One that will charge your battery quickly and then once it is full, will switch to trickle charge to maintain it until you are ready to use it again. Most smart charge/fast charger battery chargers will charge a battery of 30-60 amp-hours in 2.5 to 5 hours.
This set-up will run on battery power for around a half hour. Ideally you will not want to discharge the battery less than 50% because this shortens the battery life. But with batteries of these sizes costing anywhere from $60 to $120. Even if you had to replace one every year, it would be worth the money for the convenience of being able to milk anywhere that you could transport the setup to. A good cart is recommended.
You can watch the video below for an example of this set-up working with one of my goat milkers with Welch pump. A larger pump can be used but it will of course run for less time.
I hope to sell ready-made battery packs in the near future for those who just want a plug and play option for a battery powered portable milking machine.