Kevin.S: my post is specifically about Kitno's situation with his Lithium battery and fooling the internal BMS. Where a flooded battery can't be charged you will usually have a fairly fatal issue with the battery. Some chargers won't charge below 10 volts or so and may be fooled by connecting a 12 volt source but again I don't recommend it unless you are certain that the battery has simply been run completely flat by a load being left connected. It isn't dangerous to try buit the likelyhood that you can resurrect a battery that probably has a terminal fault and then rely on it as a start battery is quite low.

Bloody useful info there Salty, I'll definitely remember this for future reference.  I had a case just a month ago where I had run a car battery right down and my "smart" chargers would not even look at it -this trick may have fooled them into charging it.  In this case it was OK as I got the battery replaced as it was within warranty.  Would this work by connecting one of those booster starter batteries across the terminals while you start charging?

Think I will stick with the flood.

Lithium, opinions vary and dangers abound!

In my opinion, the issue is why the battery is not working. The BMS can disconnect the battery because it detected over voltage or heat, in either case it wouldn't be wise to apply a shock load to the battery by connecting jumper leads and pushing start. Not only does it not fix the reason the BMS disconnected the battery but it can cause a fire and, in the worst case, an explosion.

The other issue is that the load has been disconnected from the charging source by the BMS as well, so when the motor is running again, if it doesn't reconnect successfully then running the charging source with nothing to charge may cause major damage to it! 

Lithiums are used as start batteries for motorbikes and the general recommendation is not to jump start them from another battery.

BMS can be in a charger , as i suggested above or in a battery.. or both early lithuims didnt have built in BMS.

To by pass the BMS for a battery holding a charge below any of the BMS pre sets.. can be fooled by introducing a higher voltage for a very short period... it is potentially dangerous to do so for any more than a few seconds.

 If it then doesnt start to charge then something else is likely to be an issue as noted above by Salty.

 Also the correct charger must be matched to the correct battery type to charge.. and correct alternator in vehicles etc.

 Back in the day of std wet lead acid was never an issue.. then came geled and AGM acid batteries.. these , espec the AGM which we use ad marine batteries should not be charged on a std pb acid charger....

If you have and note a short battery life, that is why.

 Cd batteries also require a dedicated charger, as do lithuim

 They all charge at different rates and have different full charge voltages.

 Now we have introduction of smart chargers that detect type battery, charge rates ans some even have recondition modes.

All which pretty knowledge thru hot rodding, car resto guys, marine workshops, sparkies  And basic 'technicians' on cctv cameras , security, lighting and similar  isolated solar powered systems etc. ,  and considered pretty basic stuff

 Once the higher voltage is detected it then supplies its own voltage to maintain the charge sequence

All this I have posted before many times over the yrs..maybe decade.