My Dyson v6 Slim is flashing red.I used it earlier in the day.It worked great.I bought my Dyson 2 or 3 years ago had no problems until now.I love my Dyson!!!

two faults, mainly battery.

A flashing blue light indicates that there is no power, please charge the battery. A flashing amber light indicates that there is no power or a temporary fault (e.g. too hot/cold). A flashing red light indicates that there is a fault, please call the Dyson Helpline.

Support and How to Guides for your Dyson V6™ Vacuum

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Here is a link to the manual:
https://www.manua.ls/dyson/v6-slim/manual?p=3

Replacement Vacuum Cleaner Battery for Dyson V6

Chemistry: Li-ion

Voltage: 21.6V

Capacity: 3000mAh

Color: Black

Weight: 340g

Dimensions: 132 x 114 x 88mm

US Office

Dyson Inc.

600 W. Chicago Ave
Suite 275
Chicago, IL
60654
Dyson Helpline 1-844-679-1647
The Dyson Helpline is available during the following times (CST):

Sunday: Closed
Monday - Friday: 8am - 8pm
Saturday: 9am - 6pm

Faulty item contact retailer for repair or replacement

Use the link below. Copy and paste

http://www.manualslib.com/manual/960591/Dyson-V6.html?page=4#manual

Hi Jean, it's Jack at Dyson.

I'm sorry to hear you're having difficulty with your DC31. If it cuts out in use when it's fully charged, we'd need to take you through some quick diagnostic checks when you have the machine at hand. This will help our experts determine what may be causing the issue.

Please give our customer Helpline a call on 0800 298 0298 (UK), or 1-866-693-9766 (US). We'll look forward to hearing from you.

Best wishes,

Jack
Dyson Online Customer Support
www.dyson.com

I had a similar problem when I bought an after market 2Ah battery. Would stay solid red for a few seconds then flash red. I believe my problem was that the battery had gone into "sleep mode" I.e. it was discharged to the point that it "sleeps" in order to protect itself. So......I simply attached a domestic DC multi adapter to the terminals on the battery that are marked + and - (the 2 outside terminals on a DC16 Dyson battery). Switched on the DC adapter for around 10mins and this was enough to "wake" the battery. It now charges as normal attached to the DC16 in the Dyson charge mount.

For a pretty in depth article on lithium battery sleep have a look at this:
http://batteryuniversity.com/learn/article/low_voltage_cut_off