Run powershell in windows batch file

I needed to run a powershell script in batch file so it would be executed as one line of commands, without requiring to run .ps1 file directly.
The task is fairly simple, I've done this before. But this time I ran into another problem, because the need of using " signs inside " signs that were actually around -command argument.
This leaded me to a problem that I couldn't use escape chars for " because it would escape it from script altogether.
I couldn't use ' signs either, because that would turn variable names into direct strings.

Here is what I had at start (works within powershell):

$date = Get-Content '.\card_dates.txt' | Select-Object -last 1;
Get-ChildItem '.\sql' -Exclude '*.parsed' | ForEach-Object ($_) {
   Get-Content $_.FullName | Foreach-Object {
      $_ -replace '#PARAM_1', $date
   } | Set-Content "$($_.FullName).parsed"
}

Here is the modification that gave me the error (if running from batch):

powershell -Command "& { $date = Get-Content '.\card_dates.txt' | Select-Object -last 1; Get-ChildItem '.\sql' -Exclude '*.parsed' | ForEach-Object ($_) { Get-Content $_.FullName | Foreach-Object {$_ -replace '#PARAM_1', $date} | Set-Content "$($_.FullName).parsed" } } "

This is the error:

Set-Content : Cannot bind argument to parameter 'Path' because it is null.
At line:1 char:222
+ ...  | Set-Content $($_.FullName).parsed } }
+                    ~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidData: (:) [Set-Content], ParameterBinding
   ValidationException
    + FullyQualifiedErrorId : ParameterArgumentValidationErrorNullNotAllowed,M
   icrosoft.PowerShell.Commands.SetContentCommand

So what did I change to make it work?
The solution was actually really simple.
Instead of using:
"$($_.FullName).parsed"

I had to use:
$($($_.FullName) + '.parsed')

And here is the solution that works directly from commandline

powershell -Command "& { $date = Get-Content '.\card_dates.txt' | Select-Object -last 1; Get-ChildItem '.\sql' -Exclude '*.parsed' | ForEach-Object ($_) { Get-Content $_.FullName | Foreach-Object {$_ -replace '#PARAM_1', $date} | Set-Content $($($_.FullName) + '.parsed') } } "

What this script does?

1. Read last line from textfile (it is populated there by other scripts)
2. Read all SQL files inside SQL folder
3. Withing every file, change #PARAM_1 to be the last line from textfile
4. Save the file with .parsed extension

Basically we have templates for SQL sentences and historically all the jobs run as BATCH files.
I'm better with Powershell so I wanted to do it in powershell but at the same time keep the old BATCH-es.

Hopefully this information is a bit helpful for you, I spent quite some time to figure out the simple solution.