@ianmackie your phone may not support fast charging. Go to Settings>Battery and Device Care> Battery> More Battery Options and see if it gives you a fast charging option. If it does, turn it on. You will need a 15W power adapter to achieve that. If it is not supported there is nothing you can do to fast charge it.
=== Update (03/17/24) ===
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@ianmackie ah now that makes sense. It is not properly charging. Let's forget about that whole fast charging stuff :-). Have you checked your charger to make sure it has proper output. If yes, and if this would be my phone, I would consider replacing the charging board. Those are known to get a bit flaky and not being sure how old your phone is, I would also replace the battery. It may be at a point where it just no longer either holds a charge or takes a charge because of issues with the battery management board.
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@ianmackie ah now that makes sense. It is not properly charging. Let's forget about that whole fast charging stuff :-). Have you checked your charger to make sure it has proper output. If yes, and if this would be my phone, I would consider replacing the charging board. Those are known to get a bit flaky and not being sure how old your phone is, I would also replace the battery. It may be at a point where it just no longer either holds a charge or takes a charge because of issues with the battery management board.
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Since iFixit does not yet have specific guides for those tasks, use this onehttps://www.ifixit.com/Guide/Samsung+Galaxy+A03s+Screen+Replacement/162344 to replace the battery, the charging board and do check the flex cable from the charging board to the main board, those tear and do come loose as well.
@ianmackie your phone may not support fast charging. Go to Settings>Battery and Device Care> Battery> More Battery Options and see if it gives you a fast charging option. If it does, turn it on. You will need a 15W power adapter to achieve that. If it is not supported there is nothing you can do to fast charge it.
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=== Update (03/17/24) ===
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@ianmackie ah now that makes sense. It is not properly charging. Let's forget about that whole fast charging stuff :-). Have you checked your charger to make sure it has proper output. If yes, and if this would be my phone, I would consider replacing the charging board. Those are known to get a bit flaky and not being sure how old your phone is, I would also replace the battery. It may be at a point where it just no longer either holds a charge or takes a charge because of issues with the battery management board.
@ianmackie your phone may not support fast charging. Go to Settings>Battery and Device Care> Battery> More Battery Options and see if it gives you a fast charging option. If it does, turn it on. You will need a 15W power adapter to achieve that. If it is not supported there is nothing you can do to fast charge it.