Replacing dtdp relay with mosfets

[longpole001]

Hi Guys

i would like to replace a DTDP relay with some descrete mosfets N and P pairs

, but am having some issues with the cct i have made so far


Description

CCT A : works

Q20 , Q18 pairs ensure polarity of the battery is correct as the battery charger modules dont have polarity protection

Q19 isolates the bat charger MOD1 from the 7.2v when USB PWR is not on
RLY1:B N/C connects the bat:B to bat:A when no USB PWR
RLY1:B N/O connects bat:A to gnd so that MOD1 charger can charge it
RLY1:C N/C uses the battery power when no USB Pwr
RLY1:C N/O - connect USB to pwr cct , and charges battery

Relay activated by USB pwr at 5v

Note: USB power can be connected prior to batteries been installed in cct , as such incorrect battery polarity must be isolated , until corrected
---------------------------

CCt B: does not work
q100 = q20 IN CCT A
q103 = q18 IN CCTA
q101A works same as Q19 as described in cct A

q102A: NCH replaces RLy1:B N/O in CCTA
Q102B: Pch replaces Rly1:B N/C in CCtA
Q101:B Pch replaces Rly1:C by isolating the 7.2v when USB PWr is on


Problem:
when q102A has USB_pwr = H , q102B remains on
when q101:B remains on when USB_pwr is on

suggestions ?
77567757

[Demon]

I keep thinking about the "chicken or the egg".

I'm trying to wrap my head around circuit B but can't find the exact problem.

Robert

[longpole001]

i think it has to do with the voltages on q102b , gate vers drain voltage

gate has 5v when usb_pwr is on , Drain has 3.7v , so differance is - 1.3v and is still on as a result ???