What's the word for someone who knows what you need in advance?

thoughtful

showing consideration for the needs of other people.

• He was attentive and thoughtful. (OxfordL)

or

given to or chosen or made with heedful anticipation of the needs and wants of others

• a kind and thoughtful friend (M-W)

And you could definitely call a mother or a wife thoughtful. This article considers things much more in depth. Among other things, it says:

We have seen that thoughtful implies wanting to alleviate another's pain or suffering. It can also be used to mean wanting to do something for the benefit of another.

The connotation is further described by showing the thinking mechanism of a thoughtful person:

It is important, then, to include in the definition that not only does a thoughtful person not want others to feel bad, they want to do something to cause them to feel good. This can be captured with the following components:

• X often thinks something like this about people:
• I think this person will feel something good if I do something (W)
• I want to do something (W) because of this

solicitous _{(Merriam-Webster)}
Synonyms attentive, considerate, kind, thoughtful

In my experience, the term nearly always implies providing [exactly] whatever is needed (by the person who is being attended to by the solicitous person).

They are provident.

provident [adj]

1. Providing for future needs or events:

• "a shelter with bunks, springs only, intended for provident hikers who carried sleeping bags" (Donald Hall).

[American Heritage® Dictionary of the English Language]

This is a hypernym, as these provident hikers might only carry their own requirements.

She could be described as prescient:

a.1. Having knowledge of coming events; foreseeing; conscious beforehand.

foresightful

[having] the ability or action of imagining or anticipating what might happen in the future. Free Dictionary

Someone who knows what someone else will need in advance could be described as foresightful, or having foresight. The fact that the person then meets those needs is a strong implication although it is not included in the meaning of the word.

What's wrong with directly stating "anticipating their need?" Or, "anticipated his need", to better match the example? "My mother anticipated that my father's battery would need to be charged." This captures the intended meaning exactly. I don't see a need to rely on just one word.

"Foresaw" works pretty well, but it's not an adjective. "My mother foresaw that my father's battery would need to be charged." My thoughts are that "foresightful" doesn't work, because "foresightful" pulls in too much of a sense of "having foresight", which can mean literally being able to see the future in a supernatural sense, and that doesn't work for a case of reasoned foresight.

To be descriptive, a phrase might be better than trying to find an adjective. For example, "My mother very often anticipates other's needs." Or, "My mother is very good at foreseeing what others will need."

Attentive is an adjective that suits someone who anticipates the needs of others.

From Lexico

1.1 Assiduously attending to the comfort or wishes of others; very polite or courteous.

Synonyms include conscientious, considerate, and accommodating. From your description, "She is attentive to those around her, anticipating the need to charge his phone before he does."

I'd say they are proactive.

proactive

adjective
acting in anticipation of future problems, needs, or changes

// Once patients have the big data about their bodies, the thinking goes, they can be proactive about their health, cut care costs and foster better relationships with their doctors.

[Merriam Webster]

Or forward-thinking.

forward-thinking

adjective
thinking about and planning for the future, not just the present:

• Forward-thinking architects focus on the long-term environmental impact of their buildings.
• The City has consistently shown an innovative and forward-thinking approach to providing services.

[Cambridge English Dictionary]

intuitive is the word which will fit in.

ADJECTIVE 1 Using or based on what one feels to be true even without conscious reasoning; instinctive.

(Lexico)

I suggest "Johnny on the spot," an idiom referring to someone who is readily available to fulfill a need -- especially an urgent one

Source: writingexplained.org

Cognizant may be a strong contender for what you are looking for.

Adj. 1. cognizant - (usually followed by `of') having knowledge or understanding; "our youth are cognizant of the law"; "I am well aware of his limitations"

Justification: you asked for an adjective describing one who knows what one needs in advance and what to do for you. The connotation appears to be a social awareness in consideration of another's needs such that one can supply for the other's deficiencies when they occur. To be aware, or cognizant of, one's needs seems fitting given the immediately following definition of incognizant on the same page:

incognizant, unaware - (often followed by `of') lacking knowledge or awareness; "incognizant of the new political situation"

Here is how it sounds in a sentence:

My mother was cognizant of my father's needs, always looking out for him, and preventing even the slightest misfortune from befalling him.

The word that strikes closest for me is anticipation and you'll see that used in the definition of several words above. There's no direct adjective, but to steal a quote from the movie Gosford Park you could say they 'have the gift of anticipation' .. https://www.youtube.com/watch?v=cXkfnowZrNM