Replacing 12v acid battery with lithium pack
I have made a battery pack using 4.2v lithium cells from old laptops in a 3x7 cell arrangement (multiply voltage by 3 and multiply capacity by 7). I have a dead 12v acid battery in my Honda Insight 2010 and I want to replace it with my homemade lithium battery pack, however, a straight plug-and-play replacement won't work.
To charge this battery pack, I have to use a BMC circuit which regulates the charging of individual cell sections to retain the health of the battery. However, this BMC circuit has 4 terminals -- 2 are for charging the pack and 2 are for discharging. However, the lead-acid battery has only 2 terminals which are used both for charging and discharging. Also, I can't connect the 2 input terminals of the BMC with 2 output terminals of the BMC because that would cause the battery to charge itself, thus creating a short circuit.
Here's the thing, I believe the car's 12v positive terminal is connected to a separate circuit for charging and a separate circuit for discharging of the battery. I want to separate the connections of these circuits and make a separate positive terminal that only charges the battery and a separate terminal that only discharges the battery. And this is my question: what is the name of the charging and discharging circuits that the 2 battery terminals lead to?
I want to use the name of these circuits to find the electrical schematics online that will help me to find the physical location of these circuits in my car and separate the terminals for charging and discharging. Maybe you also know where to find such schematics?
I did find an electrical troubleshooting manual of this forum, but I can't seem to find what I want to look for. insightcentral.net/forums/honda-insight-forum-2nd-gen-discussion/61922-download-2010-2011-insight-service-electrical-troubleshooting-manuals-pdf.html
Any help is appreciated. Thank you.