If you have a Steam Deck with an LCD screen and its battery is starting to fail, repairing it has become surprisingly expensive. The official replacement battery for the original model has gone up in price again at iFixit and now costs $179.99 for the battery alone, or $184.99 for the complete repair kit. To put this into perspective, the battery originally launched at $79.99. Just a few weeks ago, it returned after a period of limited stock at $129.99, and this new $50 increase means its price has now jumped by 125% compared to the original price. Steam Deck
Often the charge controller isn’t even part of the battery. A BMS is but that is only a safety precaution against overcurrent or over/undercharge.
The charging itself, from the usb cable to the battery is usually done elsewhere.