Boots to retropie splash then shuts off

[Flavor]

I don't see anything obviously wrong with what you did.  I guess it could be a bad cell or maybe a bad wire.  
Edit:  I do see that the JST is wired backwards.  It's not difficult to fix.  You can just pull the pins out of the plastic and swap them.

OH, where did you get the JST wire/connector?  I have seen ones that are wired backward.  I can't be sure from your photos, but I think that may be the problem.  Please see the info/photos here.
https://docs.google.com/document/d/1keiQ...psx3ttonfv

[r0ckarong]

I don't see anything obviously wrong with what you did.  I guess it could be a bad cell or maybe a bad wire.  
Edit:  I do see that the JST is wired backwards.  It's not difficult to fix.  You can just pull the pins out of the plastic and swap them.

OH, where did you get the JST wire/connector?  I have seen ones that are wired backward.  I can't be sure from your photos, but I think that may be the problem.  Please see the info/photos here.
https://docs.google.com/document/d/1keiQ...psx3ttonfv

I bought a dozen or so including sockets from some seller on eBay. They're all wired that way. I have reversed the contacts in the connectors now and will proceed from here.

Why would the batteries appear to charge when the wires are backwards though? I left them plugged in with the leads the wrong way and after a few hours the green LED on the back came on indicating that they were full. When I reversed the leads and tried to boot I got the red "Low battery" led on the front immediately. What is the green LED on the back actually indicating if it's not full charge?

[Flavor]

Why would the batteries appear to charge when the wires are backwards though? I left them plugged in with the leads the wrong way and after a few hours the green LED on the back came on indicating that they were full. When I reversed the leads and tried to boot I got the red "Low battery" led on the front immediately. What is the green LED on the back actually indicating if it's not full charge?

I think this was a bit of an artifact from the charging circuitry becoming "confused" in a way.

We built in reverse-polarity protection, so that nothing would get damaged if you hooked it up backward. That doesn't mean it will function properly in that configuration. Here's our best guess.

Hooked up backward, the machine won't run. When you hook up power to the charging port, there is a tiny bit of current draw when it tries to charge the battery (even though the reverse-polarity protection has kicked in). The charging circuit is "testing" the battery and thinks that it will try to charge it. The charging LED goes blue.

The charging circuitry also has a timeout "error" condition where it will set both blue AND green on. I think this is what will happen after it tries to charge for a while with no result. It may appear that the green LED is lighting up (because it is), but the blue LED will also (likely) be on in this error state.

What SHOULD happen (to the 2 back LEDs) is the blue LED indicates charging. When charged the blue should turn off and the green should turn on. If you see both blue and green, that's an error. This can sometimes happen if the microUSB power/cable doesn't supply enough amperage.

I'm guessing also that you saw the red LED on front, because the microUSB cable was powering your console, but the charging circuit thought that the battery was dead (in this case in the reverse-polarity shutdown state).

[r0ckarong]

So the fact that both blue and green LED on the back would have led me to suspect there's something wrong much earlier.

Can you provide me with a list of conditions what LED should be doing what and I am happy to sort them into something usable. My profession is in technical documentation so I am used to this kind of work. Same goes for other "alternate states" of the hardware that you shouldn't be seeing when doing it right but you spend much more time explaining how NOT to do things then how to do it the right way just to make sure.

EDIT: I have started to collect this stuff and hope to come up with some more during my build. I will supply that information to you as I move along.

[r0ckarong]

I've got plenty of other questions about this:

* How long does a typical charge cycle for a 1000maH battery last?
** What is the charge current/voltage going through the board to the battery ports?
*** If it takes significantly longer, might the batteries be faulty?
*** Does that simply double with two batteries or is it split between ports?
*** How do I even tell that my battery cells are charging?
* What is the recommended current/voltage supplied by the power supply/charger to reach ideal results?

I am currently powering the board with two batteries connected from a phone charger with 5,2V / 2A output. No idea what is actually being put throug or what I would need.

You must have some recommendations or experiences of what type of charger (voltage/current) works fine with the board.

I would also love to have some way to verify that the batteries I have are just not duds and I need to get new ones. I was on that wild goose chase because of the two back LEDs lighting at once so I thought they at least charged but now I've had both of them hooked up and I still don't see a green light. Is there anything you can share about how to measure if a LiPo cell is actually dead?

[a-butta]

In addition to your table, if there are no batteries connected and you plug in a USB cable then DS4 will be green until you plug a battery in.

[a-butta]

* How long does a typical charge cycle for a 1000maH battery last? 

-The MCP73871 Lipo charger is configured on the Freeplay board to charge at a rate of 500mA which is also what is recommend for the Lipo batteries sold on the Freeplay Tech website. At the current configuration a 1000mAh battery will take about 2hrs to go from fully depleted to charged.

** What is the charge current/voltage going through the board to the battery ports?
-The MCP73871 is the 2CC/ML version which is preset to charge the battery to 4.2V. The charge rate is 500mA,

*** If it takes significantly longer, might the batteries be faulty?
-It is possible to have faulty batteries however it depends on how depleted they are. Verify the voltage is greater than 2.4V

*** Does that simply double with two batteries or is it split between ports?
-Yes, the time it takes to charge is doubled with two batteries.  

*** How do I even tell that my battery cells are charging?
-If the batteries are wired correctly then when only the blue light is showing on the back, then the battery should be charging.  Measure battery voltage and it should be increasing towards 4.2V

* What is the recommended current/voltage supplied by the power supply/charger to reach ideal results?
-The best results via the micro usb charge port is 5.1 to 5.2V

I am currently powering the board with two batteries connected from a phone charger with 5,2V / 2A output. No idea what is actually being put throug or what I would need.
-That should work great for charging the batteries.

You must have some recommendations or experiences of what type of charger (voltage/current) works fine with the board.

I would also love to have some way to verify that the batteries I have are just not duds and I need to get new ones. I was on that wild goose chase because of the two back LEDs lighting at once so I thought they at least charged but now I've had both of them hooked up and I still don't see a green light. Is there anything you can share about how to measure if a LiPo cell is actually dead?
 
-You can measure the batteries and at the least they should be 2.4V but ideally above 2.9V. I would connect the batteries and charger, and monitor if the voltage goes up. If it the voltage doesn’t go up then your batteries might be damage. They will take a long to go up in voltage if they are heavily depleted due to the lipo charger trickle charges in what the datasheet calls a “precondition” to make sure the batteries is ok before if turns on the full charge rate.