My brand new road bike that has 12 sp Di2 shifting won't charge properly. I checked the pins, snapped in the charging cable to the RD and tried several different charging blocks. Now, when It's plugged in to charge I get 1 Red led light followed by 3 Blue led lights. No green! My LBS sent me a new battery and cable but I haven't tried that yet.Any ideas what's going on?

When and from what are you getting these lights? Are you are pressing the function button and then changing up the shift mode? Maybe you are too slow pressing and releasing the button.

Try https://bettershifting.com. Terry knows most everything about Di2 and is very helpful.

According to the manual when charging the derailleur you'll only get two LED colours, blue for charging and red for error. It sounds to me that you're getting momentary red until the connection is established, then blue as it tries to charge, then nothing because charge is already complete, and fully charged is indicated by ... nothing. Seems like poor design, what's wrong with green for good, Shimano?

Sometimes it helps to have a Garmin Edge that you can connect to the DI2 system. You can add a data field somewhere to display DI2 battery status, that’s where I check mine,

Yep, Garmin definitely does that -- I think any other decent computer will, too.

Wahoo might. Hammerhead does not after SRAM purchased them, Shimano dropped the license that allowed Hammerhead devices to connect to DI2. Somebody created a side loaded app for the K2 to access DI2, don’t think they have that for the newer K3.

Found this:

That's it! the LED will light up blue, indicating that the battery is being charged.

Charging the bike should take between 1 and 3 hours, depending on the adapter used, as well as the remaining battery level. The LED will turn off when the battery is fully charged.

If you're trying to charge the bike and the LED flashes red, then you may need to use a different USB port or adapter.

Note that any adapter you use should have a current capacity of 1.0A or higher.

Finally, you cannot operate the derailleurs while charging - they won't respond to shift commands. Charging the battery using a dynamo hub or power bank while riding isn't an option, unfortunately.

You can obviously check the charge level in the etube app too

UPDATE: I have a RD-R8150 Ultegra Di2 12 speed. I've been reading the manual, calling LBSs, posting here on BikeForums, calling Shimano and chatting with BikesDirect.com. I've got the E-TUBE Cyclist app on my phone but since the battery is dead it won't connect to the Di2 now. I've learned about the 3 different shift modes and what the different colored lights mean. When I first charged the battery I got a flashing green light indicating a partial charge. But now, when I press the program button on the RD, I don't ever get green. Only red, then blue which indicates dead battery and normal shift mode. And, when I plug in the charging cable, I don;t get the blue light that indicates charging. So, at this point I'm going to take it to the LBS and have them diagnose what is going on using a PCE02 linkage tool. Bikes Direct.com did send me a new battery and charging cable but I still have to pay the LBS a labor charge for diagnosing the problem. I love the bike, but not the Di2 headache! What irritates me is when BikesDirect.com says, "We've sold 100 of those bikes and never had a problem!" Well lucky me!

The brain of the system is in the rear mech so if there’s something wrong with that, a new battery won’t solve it. It’s a great system but feel your frustration / disappointment

Unplug the Di2 wire going into the rear derailleur--Use the [should have been included] TL-EW300; the small forked end wraps around a notch in the wire (accessed by pulling the small cone-shaped boot upwards), and you simply pull up. You will feel a pop. Assembly uses the opposite end of the tool, and more complete manuals can be found at si.shimano.com . Look for a dealer manual (DM) after typing your derailleur's model "RD-8150" into the search bar.

My assumption is that the wire is either not seated in the derailleur, the wire is not seated in the battery, or the wire itself is damaged. Component faults (ie, the derailleur or battery) that happen outside update faults are rare, and most troubleshooting starts with the wiring.

A shop with the PC Link Device will be able to rule out several things in quick order, as all the peripherals are logged when it is plugged in. A bad/no connection shows up as a missing component, depending where the system is plugged in.

Update #2: the diagnosis was that the charging port was faulty on the RD. That's why it wouldn't charge when I connected the Charging cord to the charging port. What follows is the professional diagnosis: Item/Labor # Price Labor Di2/AXS Firmware Update with Problem Diagnosis (Repair Not Included)
"Everything works except the rear derail charging port, which isn't tested in the error check. So everything came back normal, charged this battery off of a floor bike, and tried to charge the floor bike off of this derail, and it wouldn't. To test, I had 2 different charge cables, 3 batteries, and 2 rear derails. Every combination charges UNLESS his derail is used, then no combination works. Rear derail is otherwise functional but cannot be used for charging. Also: I can connect his rear derail to E-Tube while the charge cable is plugged in, and E-Tube will normally not allow this: so the rear derail does not know it's plugged in to the charge cable. Charged his battery to 100% using our rear derail so he can ride for now." I take the bike back to the LBS this week to get the RD replaced with a new RD under warranty. wschruba, I will also share your input with the mechanic to see what he thinks. I saved $ buying the bike online, but not without several inconvenient glitches!

I think Wahoo can connect to DI2. Hammerhead K3 cannot since that disagreement between Shimano and SRAM

Shimano is good about warranty on the R derailer. I accidentally kicked mine in December, it broke at the upper pivot, Shimano replaced it. It’s a $410 derailer.