Charging Ecycle lipo batteries with a lead acid charger

I have got the mrs a ebike, it has a 36v 15ah battery pack.
I have a 1.8a 'intelligent' lead acid charger, only its not intelligent, it charges at 1.8a constant current, up to some voltage then switches to a taper charge, it has a uc3842 smps chip and a Lm358 op amp.
Open circuit voltage is 42v, which is correct for a 10s lipo, the question is would the lipos 'like' the taper charge, or woudl the charger not even get into that mode.
I got the pack as a load of panasonic cells welded together, and I of course got a Bms Pcb to go with it.

Since you will use a charger that is completely wrong to charge a Lithium battery then the battery will probably explode and/or catch on fire.
A multi-cell Lithium battery is usually charged with a "balanced" charger so that each cell gets a maximum of 4.20V. Without the balancing then the weakest cell will over-charge then explode/and or catch on fire.
A Lithium charger senses the charging current dropping near a full charge then shuts off the charging to avoid an over-charge explosion and/or..... because a trickle charge must be avoided.
We do not know any of the features of the Bms that you have.

As AG noted, use that charger for your lithium batteries only if you are looking to be a candidate for this year's Darwin Award.

Don't do it. Period.

Already done.
The overcharge stage is disabled, the charger is now a 1.8a current limited power supply, just as per a lipo charger, in fact probably better than some imported ones.
The Bms does the rest for me.