Battery Tender 800 Flashing Green Light

Very good device but hardly fast speed and external light keep flashing green. But over all everything seem fine

This is a very nice headlamp, without two levels of white light, a red light and a flashing red light.  Having the battery pack on the back makes it much easier to balance and the straps are adjustable over a wide range.

As many others mentioned in the reviews, these batteries are now new old stock, as the newest ones were made in 2022 and will arrive completely discharged. DO NOT give up on them - the charger will initially show an error (chamber and calibration light flashing) - keep taking the battery off and putting it back on, and eventually it will start to charge. The key is to not leave it in the charger if the charger is showing the error code, you have to remove and replace the battery until the charger shows that it is charging (chamber light and 50% light flashing). After a few hours the 50% light should glow solid and 80% should start flashing, and eventually it will charge fully

My APC UPS sounded off every few hours with beeps and a flashing red light to let me know it was time to replace the battery. I ordered online and the battery arrived sooner than expected. I installed it and it's been working fine since. The part I especially like, I didn't have to shut everything off to install.

I bought this a month ago when the battery died (I unfortunately did not notice the low battery flashing light indicator). The replacement battery arrived very promptly, was easy to install, and my backup is operational again — and just in time because a tornado hit here a few days later and I lost power for 8 hours.

but it is unsettling to have the upstream light flashing

Needed a replacement battery for my D 800 and this one worked well.

Works great with the Bescor battery...the light turns green on it when it's fully charged.

Sturdy charger, green lights indicate when each battery is fully charged. Light weight.

Seriously, this thing is great. Just plop in up to 2 batteries, tells you their status and juices them up. They still have a good load, just take out the battery and skip the charge. Very easy to manage your set of batteries. Clear indication of battery status no reading, arcane, flashing / not flashing, is that amber or orange.... Works well in car also and does not require a power brick just a universal 2 prong power cord. Charging is quick but not overly (quicker = less battery life due to the heat). I have use mine with Fujifilm X I understand other adaptors are available. Most fujifilm users have or should have multiple batteries: I Higly recommended this