GT

@cw_o Welcome :)

If the price is okay I'd take the risk. Getting actual chips from companies like Mouser, Digikey and LCSC can be pricey once you get to the shipping screen. I've gotten chips from eBay and AliExpress (likely the same source) without many issues for things like IMUs, Mosfets and a handful of logic ICs.
Get multiple though just in case you need to redo it. No more than 5 should be fine. IMU's are fragile so you may need to try a few times.

@cw_o

• If they have a reflow/hot air station then that's the tool you need :) Air for the chip and an iron to touch up the pads.
• Before removing the chip make note of it's orientation for when you replace it.
• Use some isopropyl alcohol and a cotton swab to clean the area and remove some of the conformal coating. It'll get in the way otherwise and possibly compromise a good solder job.
• 180c-200c on the hot air station should be fine to get it off without putting too much heat in the pcb. If you find after a minute it's still not showing signs of moving you can carefully increase the temp but not by much.
• Airflow setting somewhere in the middle. Not so much it flings off parts but not so slow it doesn't put heat in fast enough to fight the power planes heat dissipation.
• Don't hold the heat in one spot as you can popcorn a PCB. Rotate it around the chip so that you get a more even distribution of heat.
• Flux is your friend and will help get under the chip to get the solder molten.
• Don't pry it off, wait for it to be loose and lift up gently with tweezers.

• Once off clean up the pads gently with some solder wick and then use some cotton swabs to take up some flux before cleaning and visual inspection to make sure all pads are good.
• When wicking it's best to cut off a small section and press the iron onto the wick. You can move gently over the top with the iron or if easier use tweezers on the wick.
• Don't pull too hard as the pads can momentarily solder to the wick and tug which can result in a torn pad. If you find the wick has become soldered just apply flux and hold the iron there for a few seconds then try to move it sideways gently while still applying heat. Never pull the wick up.
• As the pads for this chip are under it you'll need to prepare the pads with solder before placing the chip. Go over with a soldering iron and pre-tin them so that they are slightly raised enough that they'll contact and flow onto chip. Not too much that they might squish and bridge. Bit of an art to knowing how much is right. Make sure this iron doesn't get too hot. The pads are delicate and too much heat from an iron can cause them to de-laminate.
• Apply some flus in the middle of the pads where the chip will sit and place it on top as centered as you can get it.
• Bring the hot air back over. The flux will melt and pool around the chip. To stop it shooting off I prefer to try hit it with heat top down so the air doesn't try to blow it away wince we're not holding the chip.
• Eventually you should see it wiggle into place as the solder and flux pull it into alignment. You can give it a gentle tap with the tweezers to make sure it's actually soldered because it'll snap back when slightly poked.
• You can press down a little on top to squish the solder and make sure all pads flowed to the chip. Don't do it with force, just a little to press it down and remove the heat. Hold that for 20-30 seconds to ensure the solder ahs set and you can let go of the chip.
• Use another cotton swab to cleanup the flux and then isopropyl to get the rest of it.

Before powering on I recommend grabbing a multimeter and checking the voltage rails and some of the capacitors for shorts to ground. The caps should have 1 to ground and the other to data so if any are bad then you may have a bridged solder joint under the chip and will have to repeat the process with less solder.

Below is a reference for the traces in the area if it helps at all.

@cw_o Did the seller say what hardware revision it was. It looks like it's pre-serialisation but the 4210-4213 models complain about mismatched BMS's. It can be worked around with additional modding but it's a factor.

4206-4209 are fine so if it's one of those it'll be a simple swap.

@cheesej Great work getting that fixed! Surprised that damage was enough to break the inductor.
Thanks for sharing your process :)

@cheesej Hiya :) That's a 270uH power inductor. If there's actual damage to the windings on it that could cause issues.

The only time I've seen similar when the battery was fine is dodgy caps on the balance IC.
Cell voltages can report incorrectly if any of the caps around the balance chip at the other end of the pcb are slightly detached or faulty. Common to do when unplugging the XT60 and bumping one.

Might be worth giving this post a lookover to see if your board is doing similar if the inductor doesn't solve the issue.
https://owforum.co.uk/topic/403/xr-overcharged-cell-that-isn-t-after-battery-upgrade-repaired

@lia Tire is good, but I'm only a couple rides in. I've been trying out different ride modes, so not sure what's the tire and what's the mode/settings, LOL. I have not noticed any real edge when carving, so that's good. Size increase might also be a factor in why the bumps feel smaller.

@onedangts-xl The tire size increase was a must on the GT side. I mean the frame itself looks so much better now with the larger tire.

Speaking of, how is the tire?

First ride impressions:

• Tons of power. Uphill acceleration, what hill???
• GTS comfortable riding speed 18/19, XL 22/23 (mph).
• All bumps feel half the size they did on the GTS.
• Battery left after 13.5 miles: GTS <20%, XL 42%.
• Overall feels very comfortable and very safe.
• Still not a fan of the concave pads so will probably swap in lowboys or flats eventually.

I do wish they could have a setting in the app for range vs power. I would like to set it to the power of the GTS with the range of my GT (27 actual miles).

Overall, quite happy with the purchase, no regrets.

@lia I saw it, can confirm was awesome 😊