Yep, exactly. You can bypass the charger that way, which isn’t recommended but can be done to revive batteries that are too low of voltage for your charger to recognize. Can be a bit of a fire hazard as you’re charging a questionable battery at like 30 amps, but the BMS should hopefully do something to prevent a fire. Maybe.
The BMS should *already* have done something, if the charger itself won't charge it because it's too low it should mean the BMS has turned it's output off. If it hasn't, or can't, then connecting an essentially unlimited current source to the pack could set the cells, wiring, BMS itself, etc on fire.
If a fire doesn't occur now, it can still have damaged the cells in a way that could lead to a fire at any moment anytime in the future, and you cannot know if this has happened.
The BMS FETs could also be damaged from the current, and in such a way as to leave the BMS unable to ever disconnect the pack from the charger (or load, in the case of single-port BMS). When that happens, then the cells are completely unprotected; no matter what limit they exceed, the BMS can do nothing about it. And unless you test the BMS to verify it still correctly functions, and that the FETs still perform exactly as their spec sheet says they should, you won't know this has happened either, and will still be expecting the BMS to protect your cells, which it isn't doing...so any form of damage can happen to the cells at any time from any excursion outside their limits, and you won't know that's happened either.
At least, not until that funny smell starts.... :/
Sometimes it’s the BMS that won’t let you charge the battery because of low voltage, not just the charger, in which case connecting the battery to another battery won’t do anything. The only way to bypass the BMS in a pack like this would be to disassemble the pack and charge the cells directly, but that’s even more of a fire hazard.
Keep in mind that the entire reason the pack won't charge in those situations is because the safety mechanisms built into it have found a problem with the cells that has been determined to be unsafe to recharge.
You may never have a problem with a cell that has had an excursion outside it's limits, or you could have a fire in the next few minutes with it.
The problem is that you cannot know if such damage has occured, and you cannot predict it's future behavior except that the likelihood of a catastrophic failure increases with usage and time.
That's the whole reason these things *have* the protection devices.
If you're not going to "listen" to them, you might as well just take them out entirely and run the cells bare. :/