Here's an excellent place to buy batteries. I heard about them from people running Lithium batteries for sailboat motors.
https://batteryhookup.com/
One set that I bought was this one, This ONLY shows the busbar kit that holds the batteries. When I bought them they had batteries in them.
https://batteryhookup.com/products/kit-only-6000w-12v-48ah-614wh-busbar-holders?_pos=5&_sid=8539b8858&_ss=r
Warning at the site they are now saying some of these, not necessarily from them, are seconds or do not meet specs.
Came with 24v 48ah 1.23kWh Lifepo4 - 48 HEADWAY CELLS @ $183/kWh for $224 total . I planned on using it for truck battery but changed my mind because I wasn't 100% positive the normal charging would not overcharge. The volume of it is small enough to fit in a rib cage. I'll go over what I think it can do after I note the human power needed.
Here's a reference to power needed by humans
https://hypertextbook.com/facts/2003/WeiLiangMok.shtml
In fact a robowaifu will need less because it doesn't need to keep warm, but...we will want it warm so likely it will be the same. So roughly 100-125W for normal stuff and with active movement. Humans can put out 400W in spurts and athletes can put out big brief spurts of maybe 1,000W but very brief. Call it 400W for Olympic athlete type power. The reason I point that out is that for robocare givers they will need to lift humans so these 400W or slightly better power spurts will be needed to sell them to nursing home type situations.
The battery pack I have is 1.23kWh. So using the numbers above I think you could easily get 12 hours of activity out this one battery pack. Likely much more because it doesn't need to always be moving around. These cells, if they prove to be what they are advertised as, would be perfect for robowaifus. They are designed to put out very high peak amperage. That's exactly what we need.
https://batteryhookup.com/products/used-headway-38120-hp-3-2v-8ah-lifepo4-battery?_pos=3&_sid=8539b8858&_ss=r
These things put out 200A DISCHARGE so let's say we get 8 at $6.99USD each($56) in series. We then have peak power of 4,800Watts. More realistically we could get 1/2 that but that's still 2,400W. Plenty. Mucho plenty and you get 8AH per cell. So 24V x 8Ah gives us 192 Whrs of power. Let's say you move it around you could easily get a couple hours of strong vigorous work out of it before it needs a charge. At a lower rate you could get more. Get four sets of these at $224 and you easily have power for a day with maybe brief charges for super strong activity. Just hanging around with a little movement I bet you could get 24 hours with these.
Now the link I gave on human power is high. I have other notes that say,
"...A labourer over the course of an eight-hour day can sustain an average output of about 75 watts; higher power levels can be achieved for short intervals and by athletes..."
I can't remember where I got that from, so I don't have the link. And "I think" maybe it's only counting the actual work. Not the power needed for metabolism to keep the body warm. That might readily account for the 100-120W figure for total energy. Notice that the lower figure means you can get a lot of work out of the robowaifu if you neglect body heating. So cleaning the house and stuff like that could be very efficient. Furthermore if it remained plugged in for heat while you were away the smaller batteries power could last a long time.
Here's a few other "blurb" figures I saved on power for humans
https://en.wikipedia.org/wiki/Skeletal_muscle
Vertebrate muscle typically produces approximately 25–33 N (5.6–7.4 lbf) of force per square centimeter of muscle cross-sectional area when isometric and at optimal length
For humans,"...According to our data table the body uses 685 W to climb stairs..." (I think this is high but I saved it and it might be a total for climbing all the stairs)
"What do we need for power to run these things? Notice that a average human can only produce about 200 Watts or so of power over a good bit of time with world class athletes at about 400 watts but you can get much higher brief spurts."
Anyways those are notes I saved in a file to give me rough ideas on what is needed. I got these searching all over for human power.