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The BT-DN300 battery connects to the rest of the Di2 system using the [EW-SD300 wires](/component/di2-electric-wire-ew-sd300/).

Is it backward compatible? Unfo

BT-DN300-user-manual.pdf

BT-DN300 User Manual

BT-DN300-dealer-manual.pdf

BT-DN300 Dealer Manual

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## Attach dummy plugs to unused ports
With previous generation Di2 systems you could leave unused ports 'disconnected' or 'open', and the bike would work just fine. Sure, water could make its way in, and that can wreak havoc on the system... but that's the risk you take for not using dummy plugs. 

New with 12-speed Di2 and the BT-DN300 battery is that each port must be 'occupied' - you **must** either connect an [EW-SD300 wire](/component/di2-electric-wire-ew-sd300/) to the port, or use a dummy plug. 

If you don't, the system will not function.

This is what the manuals say:

> When using the product, be sure to connect the electric wires to the center E-TUBE port. The product **will not operate normally** if nothing is connected to the center E-TUBE port.

and:

>  Be sure to attach the dummy plugs to any E-TUBE ports that do not have electric wires connected to them.
> The product **will not operate normally** if the dummy plugs are not attached.

So if you've recently taken out the dummy plug - for example [when updating your levers](/update-the-firmware-on-12-speed-hydraulic-shift-levers/) - and now the system doesn't work... this could be why. 

Double-check that dummy plug and make sure each port has either a wire or a dummy plug connected.

![BT-DN300 ports](https://assets.bettershifting.com/bt_dn300_connect_all_ports_c4a7a15bcf.png)


Shimano's first ever 12-speed Di2 groupset, DURA-ACE R9200 was announced September 1st, 2021. It features wireless shifting, improved disc brakes, and of course, 12-speed cassettes.

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DURA-ACE

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Internal Battery

The Shimano [BT-DN300](/component/internal-battery-bt-dn300/) and [BT-DN110](/component/internal-battery-bt-dn110) internal batteries can be installed in a number of places: the fork, MTB handlebar, a really long stem.. anywhere that fits really. 

You will most often find it installed in the seat post and for a good reason: this way it is close to the derailleurs (12-speed Di2) and [junction B](/component/internal-junction-b-sm-jc41) (11-speed Di2).

This guide was originally written for the 11-speed [BT-DN110](/component/internal-battery-bt-dn110), but works just as well for the 12-speed [BT-DN300](/component/internal-battery-bt-dn300/). The dimensions of these batteries are the same, and the only place they differ is the connector block.

Because of the larger connector block, not every seat post battery holder will work with the [BT-DN300](/component/internal-battery-bt-dn300/) battery. Information on which does and which doesn't is on the [BT-DN300 component page](/component/internal-battery-bt-dn300/).

![BT-DN110, washers and seatpost holder](https://assets.bettershifting.com/install_guide_seatpost_bt_dn110_washers_72742d3af8.jpeg)

### Di2 battery washers adapters
Despite many manufacturers advertising “Di2 compatible” seat posts, you can install the battery just fine in a regular seat post – as long as it’s round. All you’ll need to install the battery in a non-Di2-compatible seat post is a seat post battery holder.

Feel like skipping ahead? Use these links:

- [Install the battery into a "Di2 compatible" seatpost](#di2seatpost)
- [Install the battery using a seat post battery holder](#batteryholder)

**Note**: *If your frame is equipped with an aero seatpost please consult your frame manufacturer for Di2 battery installation guidance as regular battery holders won’t do.*

## Install in a Di2 compatible seat post {#di2seatpost}
If you have a Di2 compatible seat post like the PRO Vibe (carbon), you won’t need any additional seat post battery holder.

Your seat post will have come with a Di2 battery collar (holder). It will probably already be installed, but if it isn’t, install it.

![Install BT-DN110 seatpost collar](https://assets.bettershifting.com/install_guide_seatpost_seatpost_di2_collar_8425d4d605.jpeg)
Now take the two black adapter plates that came with your battery and put them around the battery and slide the battery into the seat post collar until the adapters slide into place.

![Battery installation shims](https://assets.bettershifting.com/battery_installation_shim_a2fcdd16b5.png)

 Next you’ll have to install the washers. First install a flat washer, then the wave washer, and finally the second flat washer.

![Install BT-DN110 seatpost washers](https://assets.bettershifting.com/install_guide_seatpost_di2_snapring_and_washers_f76f090853.png)
To fix the battery in the seat post and finish its installation you’ll have to insert the snap ring. Take a set of snap ring pliers with a claw diameter of 2 mm or less to mount the snap ring and place it on top of the final washer.

![Install the washer snap ring](https://assets.bettershifting.com/install_guide_seatpost_di2_battery_washer_snap_ring_b232360612.jpeg)
Your battery installation is now complete – all that’s left to do is to connect the battery to the rest of the system using an electric wire.

## Install the battery with seatpost battery holder {#batteryholder}
You could try to install the battery without a battery holder if you really wanted to, but make sure you secure it well – you do not want it to slide out or start rattling whenever you ride across bumpy terrain.

As far as I'm concerned a Di2 seat post battery holder is the only real option. All the major brands make these, both in the 27.2 mm and 31.6 mm sizes.

The [Ritchey](https://amzn.to/2OfL2pk) and [Zipp](https://amzn.to/2BWysZi) ones below can be bought on Amazon or eBay – click the links to go to their product pages. Of course Shimano makes one too, the [PRO Di2 battery seatpost holder](https://amzn.to/3fjDHAG).
![Seatpost battery holders](https://assets.bettershifting.com/install_guide_seatpost_battery_holders_db0e37f990.jpeg)

So now that you have your seatpost battery holder of choice, it’s time to install the battery. The images we’ll use on this page show [PRO Di2 battery seatpost holder](https://amzn.to/3fjDHAG), but the process is similar for other brands’ holders.

![Install seatpost battery rubber holders](https://assets.bettershifting.com/install_guide_seatpost_pro_seatpost_battery_holder_411ffa65a6.png)
Take the rubber adapters and slide them around the battery as shown above. Make sure you can still access the e-tube port. Now would be a good time to remove the dummy plug from the port.

![Slide the Di2 battery into the seatpost](https://assets.bettershifting.com/install_guide_seatpost_pro_seatpost_battery_holder2_edad628038.png)
Then slide the battery and rubber adapters into the seat post. This will fix the battery in place.

That’s it, you’re all done! You can now connect the rest of the system and finish installing your [Di2 components](/components-and-accessories/).

## A note on removal - or uninstalling
Some Di2 seat post battery holders work *really* well. They work so well that they can make it next to impossible to remove the battery from the seat post. In these cases you can usually get the battery out by taking a **J-bend spoke** and inserting it into the seat post, hooking the bent part of the spoke behind the battery holder. You should now be able to pull it out.

I've written a page on doing exactly this. Interested? Read more on [removing a stuck Di2 seatpost battery](/remove-a-stuck-di2-battery-from-a-seatpost/).

install-guide-seatpost-di2_snapring_and_washers

On this page I'll show you how to install your Di2 seatpost battery BT-DN110 or SM-BTR2 in your bike's seatpost.

Installation guide: Di2 Internal seatpost battery

Ever since the release of the [SM-BTR2 Internal Battery](/component/deprecated-internal-battery-sm-btr2/) years ago, people have been installing their Di2 batteries in the frame. The seatpost is the ideal place for this battery and several brands make seatpost battery holders to securely hold your battery in place.

However, what do you do when you cannot put the battery in the seatpost? Because your bike has a suspension seatpost or perhaps a dropper post? Where do you put the battery?

Some manufacturers put the battery in the down tube - like Canyon do on the VCLS seatpost equipped bikes. Others sometimes use an [external battery](/component/external-battery-sm-btr1/) instead. 

Both of these are not ideal. Putting the battery in the downtube generally means that you have to take out the bottom bracket to get the battery and this can be a real pain. It’s not often that you need to get to the battery, but personally I prefer to have it somewhere easily accessible.

There’s also the [SM-BTC1](/component/external-mount-for-internal-battery-sm-btc1/) of course - the bottle cage battery holder. Unfortunately this is a really chunky unit. I have one on my indoor/commuter bike and it works just fine… it’s just really big.

## Put the battery in the fork steerer
My new favourite solution is to put the battery in the fork steerer. While originally intended to be used on mountain bikes, this works on road bikes too - several [PRO stems](/component/pro-vibe-stem/) have an opening allowing you to route an [EW-SD50 wire](/component/di2-electric-wire-ew-sd50/) from the fork steerer through the stem, into the handlebar.

Sure, this isn’t for everyone and you should always put the battery in the seatpost if you can, but this is a nice alternative. 

Let’s take a look at the different methods of installing the battery in your fork steerer.

## PRO Battery Holders
Besides wedging it in place yourself using a makeshift solution, there are two options available to you. You can use either the *PRO Di2 Battery holder (PRAC0085)* or the *[PRO Gap Cap Expander Di2 Battery holder](/component/pro-fork-steerer-battery-holder/)*.

![pro steerer tube battery holder](https://assets.bettershifting.com/pro_steerer_tube_battery_holder_177cd60750.jpg)

The first one looks a lot like a regular seatpost battery holder, except you use it in the fork steerer. It is placed below the top cap (and star nut) and will work in standard fork steerers.

More interesting is the [PRO Gap Cap Exp. Di2](/component/pro-fork-steerer-battery-holder/). This is basically an expander plug that will also hold the battery in place securely. There is a non-Di2 version available too, without the battery holder, so make sure you get the right one.

![PRO steerer battery holder product shot](https://assets.bettershifting.com/product_shot_9a4a1386cc.jpg)

There is a general version, meant to be used with all stems (PRHS0110) and a Tharsis specific version (PRHS0111) - this last one comes with a Tharsis-specific cap. Other than that, they’re identical.

When you take the [Gap Cap Expander](/component/pro-fork-steerer-battery-holder/) out of its packaging you’ll end up with the expander/battery holder, top-cap and bolt, three tie-wraps, an O-ring and the manual.

![PRO steerer battery holder parts laid out](https://assets.bettershifting.com/all_components_laid_out_3e06bda290.jpg)

## Requirements
In order to safely and securely store the battery in your fork steerer, it needs to be at least **180mm long** or high, as measured from top of the fork to the bottom. Now.. on this specific bike I got lucky. I cut the fork steerer a long time ago, and it turns out it’s only 185mm long.

<LImage alt="PRO steerer battery holder 180mm requirement" src="https://assets.bettershifting.com/pro_gap_cap_length_9bf8fca747.jpg" width="800" height="652" />

So why is 180mm the *minimum steerer length*? If yours is any shorter than that you run the risk of having the battery come out the bottom of the fork and get damaged… or worse.. And besides that, it’d look a bit silly having your battery come out the bottom of your fork.

<LImage alt="Di2 battery under fork" src="https://assets.bettershifting.com/di2_battery_in_fork_e648b9d30d.jpg" width="900" height="533" />

If your fork currently has a star nut installed in it, that’ll have to go. I’m not a bike mechanic, but there seem to be two obvious ways to remove the star nut. 

You can either take a long, old screwdriver and hammer the star nut down until it comes out the bottom - or you can use a drill to take out the center of the star nut, after which it should collapse and fall out by itself.

I used the second method, because it seemed more fork friendly. The internet is a bit divided on the subject though. Just use the method you think works best for you.

If you do take a drill to the bike, make sure you wear safety glasses to protect your eyes. Small bits of metal can shoot up when the star nut collapses and you **do not want** those in your eye. Some cutting oil can help too.

With all that out of the way, let’s actually get it installed. 

## Installation Process

The expander/battery holder comes with a set of tie wraps, an O-ring and a top-cap. It also comes with a manual, which is surprisingly useful. It actually shows how to install the expander and the battery:

<LImage alt="PRO steerer battery holder manual" src="https://assets.bettershifting.com/pro_expander_battery_holder_manual_20d006f076.jpg" width="1000" height="725" />

I get that posting the PRO instructions might defeat the purpose of this page, but stick with me for a while and you’ll see there are some things the instructions manual does not mention.

Sure, it seems easy enough, right? Stick the battery in the holder, slap the tie-wraps on and insert it into your fork steerer. That’s it. 

This is what it looks like with the tie-wraps installed. You are meant to cut the top two short, but leave the bottom one as is. The manual itself seems to suggest you cut all three, but this doesn’t match the next image - and the PRO instruction videos on YouTube say you keep it long too.

<LImage alt="PRO steerer battery holder all zip ties installed" src="https://assets.bettershifting.com/pro_cap_gap_zips_installed_247dc1d594.jpg" width="950" height="698" />

With the last one left intact, this is what it looks like:

<LImage alt="PRO steerer battery holder with tie wraps" src="https://assets.bettershifting.com/pro_battery_holder_with_tie_wraps_d3d40e5fbc.jpg" width="800" height="429" />

The next step is to attach the EW-SD50 electric wire and slide it into the frame.

Before you actually do that though, try pushing it in without the wire attached. This will help you do a couple of things:

- You can check the length of your steerer tube and required spacers
- Figure out the wire length you need and wire routing
- Make sure it actually fits in the fork steerer

This is as far as it would go:

<LImage alt="PRO steerer battery holder stuck, not going in" src="https://assets.bettershifting.com/pro_gap_cap_stuck_336f5ec782.jpg" width="1100" height="588" />

If this happens to you then there are two things you can do: find some smaller or low-profile tie-wraps, or modify the ones you have. 

In this case I decided to do the latter. I took a file to my tie-wrap and took a fair bit off. This is what it looked like when I was done:

<LImage alt="PRO steerer battery holder modified zip tie" src="https://assets.bettershifting.com/pro_gap_cap_files_tiewraps_3af9f55cb2.jpg" width="750" height="312" />

With this done I gave it another go and this time it went straight in. Next up is figuring out what wire length you need. This depends a bit on what you are connecting the battery to, where that component is located and what the wire routing is like.

You’ll need **at least a 250mm wire**, since the battery is positioned with the connector at the bottom and the distance from bottom to top is **180mm**. On this mountain bike I’m using an [SC-MT800 display](/component/xt-display-junction-sc-mt800/) which is located right next to the stem. I installed a [300mm wire](/component/di2-electric-wire-ew-sd50/) and that seems to get the job done just fine.

After deciding on the wire length it’s time to insert the battery holder and the battery in for real. Before you do so though, slide the **O-ring** on at the bottom. It’ll help keep the wire in place. 

<LImage alt="PRO steerer battery holder almost ready to go in" src="https://assets.bettershifting.com/pro_battery_holder_ready_to_go_in_68ad69c495.jpg" width="1100" height="454" />

Another quick tip: position the tie-wrap ends or locking mechanisms on the same side as the wire. This will help it go in easier.

Which side is that you ask? Well.. the expander part has a big groove in it. Large enough for **three** [EW-SD50 wires](/component/di2-electric-wire-ew-sd50/). 

If you’re installing this in a full carbon fork steerer you’ll want to apply some carbon paste to the expander and then slide it in gently. Note: if gently doesn’t do the trick, hitting it with your fist is perfectly acceptable too in my book.

<LImage alt="PRO steerer battery holder going in" src="https://assets.bettershifting.com/pro_gap_cap_expander_going_in_d6215a7cf0.jpg" width="1100" height="675" />

The top part of the expander can rotate, so make sure its orientation matches that of the expander itself. The **F** should be on the **Front** and the **R** goes on the **rear**. The rear also has the torque spec on it - **7Nm**.

<LImage alt="PRO steerer battery holder torque it up" src="https://assets.bettershifting.com/pro_battery_holder_torque_it_up_f50f0202f5.jpg" width="1100" height="576" />

Next, add any spacers and use the top cap to eliminate any headset play. If you’re thinking of using a different top cap - you’ll probably have to shorten (cut) the bolt. The one provided is relatively short and there is a perfectly good reason for that. There just isn’t a whole lot of space for longer bolts, due to the battery being in the way.

### Route the wire through the stem.. or not
So if you’re looking at this battery holder then you may want to route the electric wire through the stem and into the handlebar. As you have perhaps noticed from the pictures, my MTB stem is only 4cm and there is no way you would be able to route a wire through that.

Besides that, my Cube handlebar does not have a hole facing the stem so there would be no way for the wire to enter the handlebar. All of the PRO Di2 compatible stems and handlebars do have these holes and these would be the perfect handlebar/stem to use with this battery holder.

The **alternative** I’ve chosen is to use a file to make my own cable routing hole. 

<LImage alt="Modified steerer tube spacer" src="https://assets.bettershifting.com/pro_top_cap_spacer_hole_d94fee5135.jpg" width="1100" height="416" />

You can then route the wire through the hole, out of the fork steerer. With the top cap installed and the wire connected to the [SC-MT800 display](/component/xt-display-junction-sc-mt800/), that looks like this:

![PRO steerer battery holder and top cap installed](https://assets.bettershifting.com/pro_battery_holder_top_cap_on_38352dd762.jpg)

I think it looks pretty good, even though the wire isn’t routed 100% internally. I’ll post a full building-this-bike post soon and I’ll link it on this page.

This is what it looks like from the other side:

<LImage alt="PRO top gap from rider view" src="https://assets.bettershifting.com/pro_top_cap_installed_from_rider_484c70672f.jpg" width="1100" height="553" />

For now though, this should help you decide whether or not the fork steerer battery holder is worth it or not. 

If you have any questions or comments, please [send me a message](/contact/) or leave a comment below. For more information on installing Di2 components, visit the [Bike Building Hub](/di2-bike-building/) or the [Installation Guides section](/installation-guides/).




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Where do you install your Di2 internal battery if the seatpost isn't an option? On a full-sus mountain bike, or if you run a dropper post? One of the options you have is to install it in the fork steerer.

This page explains how to do just that, using the PRO Gap Cap Exp. Di2

Internal Battery

Semi-wireless Di2

Charge time

Seatpost battery holder compatibility

Attach dummy plugs to unused ports

Details & Specifications

Shopping links

More images