User review Fenix BT20
I was chosen to review the new Fenix BT20 from a list of applicants that applied back in October 2012. This product was sent to me free of charge and I have no direct affiliations with this company.
My objectives for this test will be to provide my option on:
1 - Quality of the components
2 - Run times
3 – Beam patterns and its usefulness on the trail.
This will be an ongoing review as I have not yet been able to make time to ride with this light. But since receiving the Fenix BT20 only three days ago, I have been out to shoot some beam shots on one of my favorite trails. I was quite surprise on the results.
But first some pictures of what’s included in Fenix’s BT20 “The World’s First Bike Light with Dual Distance Beams.”
With battery case
The components that are included in the box are, user manual, warranty card, helmet strap, extension cable, three O-rings, battery case and battery case holder.
Oh…Batteries are not included!
The user manual came in English and Chinese. It’s pretty straight forward, gave good descriptions on the products features, parts included, technical info on battery to use and run times. Also has instructions on mounting and operation of the light. As well as the all-important safety tips with diagrams to along with certain sections.
Warranty period is 24 months and Fenix will repair any defective product for free.
The helmet strap is made from plastic with nylon straps and a plastic push down clamp. I would of preferred Velcro strap instead as the push down clamp seem kind of thin. The mount has a foam bottom to prevent it from moving once clamp down to your helmet. As for this type of mount, the height of the light is about the same as most other brands out there. I guess this is an issue companies have when they want their lights mounted both on the handle bars and on the helmets.
The extension cable is stiffer than I would like. It’s only 70 cm / 27.5 inches in length, while most other companies have their extension cable at the 1 meter mark (about 39 inches). So this extension cable falls a little short, especially if you’re a tall person.
Battery case holder is made from plastic has a screw down lid and holds two 18650 or four CR123A lithium batteries. The holder fits in a nylon pouch which you can attach via Velcro to the back of your helmet, bike frame or just put it in your water pack pocket. My dilemma is, it only holds two 18650’s. Why? There is no option to use four 18650 for longer run times. To me this is a deal breaker, as I would like to have longer run times with my lights without having to change them while on the trail. The holder itself appears to be of quality. Opening the case, you’ll see it has a washer around the top making this water resistant if not proof when screwed down tight. The case can only be closed one way and has markings on how the two pieces should come together. So there is no worries in reversing the terminals.
You get three O-rings, small, medium and large. Small and medium would be used the most. Medium mounts the light to the helmet strap. Depending on the type on handle bar you have, you’ll either use the small or medium O-rings. I found the small O-ring gave me a tighter grip on my handle bars. The O-rings are about middle of the pack, it’s not the thinnest and not the thickest that I’ve seen.
The light head is about 67mm in length, 38mm wide and 39mm in height not including the stand. Made out of aluminum, it’s light weight and compact. It uses a reflector and has a glass lens. As you can see from the picture, the lens itself has an engrave etching on it at the top. Now this could be what gives the Fenix BT20 the dual beam pattern, which is what I’m guessing at. The light head has no openings, seem to be water resistant and can swivel 360 degrees to help with mounting.
The power button at the top of the light is made from rubber/silicone. Hold it about one second to turn it on and each press after will cycle through the four modes, low, mid, high and turbo. I love this feature as the flashing mode is not included in the cycle. To access the flashing mode you’ll have to double press the power button. To return the normal press the power button once. The light also has memory, so it will remember the last mode you’re in when you turn it off (except flash).
The power button is also an indicator of the battery capacity.
100% - 50% - Solid Green.
50% -20% - Solid Red.
Less than 20% blinks red.
I love this feature also. I always wanted to include this in my light build, but I’m just to lazy!
Light modes and run time are as follows:
Low – 100 lumens, 21 hrs run time.
Mid – 300 Lumens, 6.5hrs run time.
High – 450 lumens, 4hr run time.
Turbo – 750 lumens, 2hr run time.
Flash – 300 lumens, 21+hrs run time.
Now I did have an issue with run times. I ran a test for “Turbo Mode” to see if the 2hr run time was accurate and ran the test in front of a fan on mid setting. Batteries were fresh out of the charger. Both had a voltage of 4.1v according to my multimeter.
Place both in the holder and took voltage reading again.
No load – 8.0v
Low – 7.9v
Mid – 7.8v
High – 7.5v
Turbo – 7.1v
Now to my surprise, after about 2-3mins the battery indicator went red on the power button. WTF? I let the test continue and after about 40mins the light automatically switches from Turbo to High mode. I would manually switch it back to Turbo but after about 5mins would switch back to High. At about the 1hr and 15min mark, the light drop to Mid. At about the 1hr and 35min mark drop to Low. At this point the power indicator was a solid red. I can manually switch to Turbo mode but the light would automatically cycle it down to low mode. At the two hour mark the light was at “Low mode” with a solid red indicator.
I stop the test at this point. Re-did the test with a new set of fresh batteries and got the same results as above. I don’t know why this has happened, was it the light or my batteries? I have about eight blue TrustFire 18650 from DX. I know they’re not the best, but I haven’t had any issue using them on my light builds. So what gives? I’ve sent an email to Bob at Fenix regarding this issue and waiting to hear back from them. Or maybe they’ll come on hear with an answer. Stay tune for an update. This is a major concern for me and anyone looking into buying this product. My option is…four 18650s is better than two. Would it cost any more to make a holder for four 18650s as batteries are not included with this set?
Another concern is that Fenix has reversed the power plugs. The male end of the plug is now on the battery and the female part is on the light. Not sure if this was indented to deter using existing battery packs that you may have. Or how safe it is to have the male metal plug on the battery end? Will having this on the battery make it easier for them to short out?
Also it would be nice to know what the max input voltage is. Maybe Fenix should include this in their manual under “Safety Tips” just in case anyone is trying to use a DIY battery pack. So that they don’t short out the light.
Now to the good part…beam shots!
Before I show you the pictures, I have to say that I was very impressed with the amount of light and the beam patterns the Fenix BT20 produces. It does give you the best of both worlds. If I have to ride with one light and one light only, the Fenix BT20 would be at the top of my list. Hands down this would be my choice for a handle bar light. Not sure about a helmet light just yet, I guess I have to ride with it to be sure. But I’m sure that having two Fenix BT20s will be all the light you’ll need for riding your favorite trails at night. Unfortunately Fenix was not able to provide me with a second light to cement my option.
The LED used is an XM-L T6. My understanding that it has a neutral tint to it. I compared it to my neutral set up and the BT20 is more on the coolish side of things. I would say just below the 5000k mark.
So instead of using another thousand words, I’ll let the picture tell the story.
Camera settings: Nikon D70s
ISO – 200
WB – Daylight
Shutter – 3 second
F stop – f4
Control No Lights
As you can see, to me you have a very useful beam pattern. A lot of light in-front of the bike and a good amount of throw so that you can see what is up ahead. My estimate is the amount of light thrown forward is usable to about 80ft. Having a second light should improve on this.
Comparing the beam pattern to my lights and that of my friends, I would need two lights to produces the same pattern. A wide flood on the handle bars and a tight spot on my helmet. The Fenix BT20 does both with one light set up pretty darn well!
I'll update this review after I have a chance to ride with the BT20. Posting more pictures and maybe a video.
Last edited by pucked up; 08-30-2013 at 09:24 AM.
Wow, TURBO mode looks sick! Great review, thanks for the detailed post.
just a Newbie
Thanks for the review.
The 7.1 initial volt on start up in turbo mode is most likely an indicator that the battery is sagging under the load. I would think that if the setup was to use two cell , then higher quality battery like Panasonic NCR will keep the voltage in the 7.4 nominal range better and helps prevent the premature cutdown from Turbo to High mode.
Is there any protection circuit on the battery holder? Or do you have to use protected 18650?
I am interested in the dual beam pattern. Can you take a white wall beam shot at a distant where it will show the dual beam pattern? That may give us a better ideal of the beam shape pattern. Thanks
As far as the battery holder, I was under the assumption that there was a 4-cell case available.
Is the mount removable if we wanted to change to a cateye or similar mounting solution?
This light looks like it would be awesome if they had just switched the connectors on the battery and lighthead. Any light manufacturer that uses a unique battery connection is shooting themselves in the foot if they want my business.
The 4 cell case is for AA batteries only and did not come with the test package. I'm not familiar with the cateye mounts, but the battery sleeve is removable via Velcro straps.
Originally Posted by irv_usc
If nothing comes up tonight, I may be able to take the BT20 out for a quick spin. The light and battery pack mounted on my helmet. It's well balanced, the battery not too heavy, it just feels weird. I guess I'm not the mount the battery to my helmet type of rider.
Right, I remembered wrong about the battery case.
Originally Posted by pucked up
My second thought was whether the mount on the bottom of the light is easily removable?
The beamshot looks good with a nice crisp cut off to the sides. The helmet mount is bad IMO. Way too high off the helmet crown.
So far nice review. Am I right to assume that the complete light head is made out of aluminum? Looks like this is using a two cell holder. Not great for long rides but if you conserve power by using high and mid level you should do well. I think this light is basically designed with commuting in mind and would likely work best on the bars.
I like the look and function of this lamp. I think it should do well as a commuter light.
Like Colleen said, better to use this with the a good set of batteries. Yes, buying a set of Panasonic 3100mAh cells or 3400 cells might cost a bit but well worth the money. The fact that this light powers down automatically is a nice feature because it will keep you from being caught without light for a longer period. However, expect this feature not to work so well in cold weather or with old batteries.
It should be, it's held on by one screw.
Originally Posted by irv_usc
From what I can feel, I assume it's all aluminum. But I'm no metal expert.
Originally Posted by Cat-man-do
I feel even with the best batteries you may only have about 1.5hrs run time on Turbo. A little short for even my low standards.
Some blue TrustFire batteries have had problems with protection PCB. And they usually degrade significantly with time, for example see
Originally Posted by pucked up
I think that two batteries are enough, battery pack is light and compact. But do not use junk cells, go and buy something better... Sanyo cells are very cheap, Panasonic mentioned before is good choice too. But they have different discharge curves and I am not sure what is better for this light.
I think the listed run times are a little over the top. I would think if you ran the light on high (450 lumen ) you should get about 3-3.5hr depending on how good your batteries are. Of course you're still going to have to deal with the auto-power down feature at some point. If this light is using an XM-L emitter no way it will get 2hrs on turbo mode with a two cell battery.
Originally Posted by pucked up
The auto-power down feature is nice but a lamp like this is really not intended to be run on the turbo mode for more than a couple minutes. I think if you run the lamp on high most of the time you will likely be able to ride a couple hours before the auto-power stuff begins to kick in. If I was going to buy this light that is what I would be wondering.
pucked....Can you start the lamp in high and then tell us when the auto-power down kicks in. Also to be on the safe side make sure you have a fan blowing on the lamp. Dont won't to confuse the auto-power down with the thermal management circuits as both have the capability of powering down the lamp.
Last edited by Cat-man-do; 11-06-2012 at 12:28 PM.
Very nice review pucked up... I am about ready to get a helmet mounted light myself. Pretty much narrowed it down to Xera, 808U, BT20. Been patiently awaiting the release of the Gloworm X1 before I make my decision. Was wondering if you are able do some side by side beam shots comparing the BT20 to another light ??? It would be interested to know how the BT20's performance would be like using Panasonic's 3100mAh or 3400mAh batteries ???
That's what I was thinking. I'm guessing you'll need 3 cells minimum and I may have something that I can use for this light.
Originally Posted by Cat-man-do
I was told by Fenix that the max voltage for this light is 12V. I'll keep you guys updated.
This was going to be my next test. Hopefully sometime this week and yes I will have a fan blowing on the light which I had during the original test.
Originally Posted by Cat-man-do
those blue Ultrafires are sagging badly under load. You'd be able to use 4 of them (2S2P) easily enough, but 2 of them can't provide the current. I found this out with a light I built for a friend and ended up rebuilding the battery pack with Panasonic cells instead which worked just fine. I doubt that there's a PCB in that pack, but if you can unscrew it and take a picture of the other side we'd know for sure.
Other than the dated UI and the crazy high helmet mount, the buying your own batteries kills it for me from a value perspective. I forgot what the retail was ($110?) but adding a couple of decent cells is going to run to ~$20 give or take at which point you're heading into Gemini Xera territory, which looks like a far better light. Or save $30-40 and get a half decent Magicshine from a reputable reseller with higher ouput and longer runtime.
The dual beam thing looks like it works pretty well though.
just a Newbie
2hr runtime from 2cells driving a XML is doable. Gemini gets 2hrs off of their 2600 mah 2cells pack when they had the Xera outfitted with T6 producing 800 lumens. You should be able to get close to 2hrs running off two cell if those cell can handle the load and rated 2900 mah or higher.
I concur with Matthemuppet with the idea of looking behind the board on the battery holder. If indeed there is a PCB built in, then running protected 18650 just add more total resistant to the circuit and creating more sag. If there is no protection board, then a test with something like AW18650 or Redilast should be perform. Personally I feel Fenix should have provided the tester with whatever cell they used for testing to the reviewer in case of any doubts.
Agreed...and looking forward to a response from Fenix...I am really interested in getting one of these..
For me, the cutoff beam adds value because I am primarily looking for a commuting light for use around lots of other cyclists and cars. A 4 cell pack would be nice too. I was hoping someone would have a review up. Nice job!
At this point, I am undecided on a purchase.
I hope the driver is rated to >8.4V otherwise it won't last long - I know that Magicshine drivers (the standard for Chinese bike lights I guess) don't tolerate 12V well. The better way to test the light properly with those batteries is to make a 2S2P pack with 4 cells, which will halve the current draw per cell.
TBH, if I was in the market for a light like this I'd either go for an all-in-one light (commuter) or a semi-decent single LED light like the Xera. The Fenix might be better if you're a flashoholic with a bucketfull of quality 18650s lying around and a decent charger (Cat?!), but otherwise there are lots of better options for similar money. Understandable given that Fenix is a flashlight maker, but this isn't a flashlight
I bought the Fenix bt20 about a week and a half ago and just received this email:
"It is with great regret that we received an email from Fenix (the manufacturer) last night asking that we NOT ship the BT20 lights we had just gotten in and had already starting processing for shipping. Apparently, there is a slight issue with the light that causes the "low battery indicator" to come on when in Turbo Mode after just a few minutes. We are told this does not affect illumination or run time so I'm sure Fenix will resolve this issue quickly. In the meantime, we are going to refund your purchase price. If you paid by PayPal, your refund should show up quickly. If you paid by credit card, it takes 2-3 days for a credit to appear on your statement.
We do apologize and hope you will re-order once Fenix has resolved this issue. "