I am trying to make some GameBoys use rechargeable LiPo batteries. I wanted to utilize a circuit that would allow me to play and charge at the same time and so I settled on the MCP73871.
I purchased a circuit fabricated by diymore from eBay for about $2.80 a piece.
Overview - I have the consoles connected via the LOAD section of the circuit, the battery on the BAT section, and a USB C connector on the PWR section.
I am new to electronics and have a few questions -
The circuit comes with a 4700 microfarad electrolytic capacitor. There is no way to fit this in any GameBoy model. According to the spec sheet it says 4.7 micro farad is plenty so I replaced it with a 4.7 microfarad tantalum capacitor which fit much better.
Is this replacement capacitor ok?
I purchased a 3.7v 4700mah LiPo battery for an original DMG GameBoy. Its quite overkill, but I thought it would be great to have a 60 hour battery life on the console.The board outputs 4.7 volts and this seems to be enough even though the system runs closer to 5 volts and might need more if I decide to use a backlight or IPS display. I have the circuit hooked up and powering the system via LiPo battery. I get the "charge in progress" status LEDs when charging the console, but its only pulling about 20 milliamps tops when charging/playing.
The system plays fine, but seems to not charge at any realistic current rate. I thought it was supposed to be 200 milliamps at minimum and up to 1amp. I even tried draining the battery to around 3.8 volts and it still doesn't charge more than 20 milliamps.
What have I done wrong that is causing such a low charge current?
If I need to bump up the current to somewhere above 5v and below 6v is it ok to add a step-up converter after the MCP73871 ? I think it has a built-in converter and I could replace that, but is having 2 bad?
I have done a similar mod on a GameBoy Color. It runs on 2.5v normally on 2x AA batteries, but seems to be running fine on a similar configuration. I purchased a 3.7v 2500mah battery. However it charges around the same rate 20 milliamp hours.
I am not sure why the circuit would ship with some kind of limitation where it only charges around 20 milliamps? What am I doing wrong? I get confused when I read the spec sheet and it seems by default charging should be at 200mah to 1 amp.
To measure milliamps I use a USB tester in between the supply and the circuit across the LOAD section. When I try to use my current measuring multimeter I get some odd readings, LED errors, and the chip heats up quite a bit. What am I doing wrong to measure current?
I got a 30V 5A power supply and I've been doing some more investigating.
It looks like I can only pull 50mA when I read with my meter. This makes me think its stuck in preconditioning. PROG has a 2KOhm resistor which should allow up to 500mA of charging current, but we don't seem to be getting there for some reason. When I crank the voltage above 5V the current can get to 150mA but that's nowhere near the 500mA or 1000mA fast charging rate.