> For the complete documentation index, see [llms.txt](https://open-rt.gitbook.io/open-surfacert/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://open-rt.gitbook.io/open-surfacert/surface-rt/hardware/battery.md).

# Battery

Information about the battery pack and BMS

![Surface RT battery pack with exposed BMS circuit](https://2395005476-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MJQb34R_xPz0ll0scbM%2F-Mc4AC-pl_CpQ18wRqBI%2F-Mc4BKGtS16DdM12TRPE%2FPXL_20210612_224811310.jpg?alt=media\&token=432336a7-3526-435b-b020-aa6ba90a7734)

{% hint style="danger" %}

#### Batteries are dangerous, working on one is difficult and require patience and skills! Do not disassemble, peel or remove one from the device unless you know what you're doing!

{% endhint %}

## Specifications of the battery pack

| Specifications | Title   |
| -------------- | ------- |
| Manufacturer   | Samsung |
| Capacity       | 31.5Wh  |
| Voltage        | 7.4V    |
| Model number   | P21GK3  |

## BMS (Battery Management System)

A battery pack requires a reliable BMS. Without it you can't control and balance the cells, leading to fire hazards.

{% tabs %}
{% tab title="Overview" %}
![](https://2395005476-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MJQb34R_xPz0ll0scbM%2F-McAdxsHNKXengcC3Daf%2F-McAfi-Cu0_9iTOp0bS7%2FBMS_OVERVIEW.png?alt=media\&token=b3a3d201-afd3-41dd-bcbb-51f6114d1478)
{% endtab %}

{% tab title="BMS" %}
![](https://2395005476-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MJQb34R_xPz0ll0scbM%2F-Mc8ryGXALCTkUk33b74%2F-Mc8yNGps0TgpyEQkToL%2Fbms.png?alt=media\&token=858c07a5-0b7d-4513-8167-4f8f72e8282c)
{% endtab %}

{% tab title="Cable" %}
![](https://2395005476-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MJQb34R_xPz0ll0scbM%2F-McAdxsHNKXengcC3Daf%2F-McAilhgoi0oNaAhcI3B%2FBattery_Cable.png?alt=media\&token=f0b847fe-902a-423d-803c-0c7772cbdd5f)
{% endtab %}
{% endtabs %}

#### IC's marked with 1-3:

1. <https://www.dexerials.jp/en/products/surface-mounted-type-fuse/sfh0412.html>
2. ???
3. <https://www.ti.com/product/BQ28400#product-details##params>

## High resolution mock-up of BMS board

{% tabs %}
{% tab title="BMS board part 1" %}
![](https://2395005476-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MJQb34R_xPz0ll0scbM%2F-Mc3zQtaJzzGLi1qtgm0%2F-Mc41OWgt-q9fIjxSZBN%2Fbattery-bms1.png?alt=media\&token=3726e3b9-88a6-491a-be6e-bd08a52b560c)
{% endtab %}

{% tab title="BMS board part 2" %}
![](https://2395005476-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MJQb34R_xPz0ll0scbM%2F-Mc3zQtaJzzGLi1qtgm0%2F-Mc41OWhLgsc5fSVbHvi%2Fbattery-bms2.png?alt=media\&token=16649838-0887-433a-bee6-4276a0378cdc)
{% endtab %}

{% tab title="BMS board part 3" %}
![](https://2395005476-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MJQb34R_xPz0ll0scbM%2F-Mc3zQtaJzzGLi1qtgm0%2F-Mc41OWiGcVj5fbkh1nz%2Fbattery-bms3.png?alt=media\&token=1194f5a2-486e-4863-92e4-26b1a8e75d7c)
{% endtab %}

{% tab title="BMS board part 4" %}
![](https://2395005476-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MJQb34R_xPz0ll0scbM%2F-Mc3zQtaJzzGLi1qtgm0%2F-Mc41OWcrEbz2d22lQSt%2Fbattery-bms4.png?alt=media\&token=5f494e80-72d6-4a48-8ad0-e7d91e04e6e6)
{% endtab %}

{% tab title="Cable" %}
![](https://2395005476-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MJQb34R_xPz0ll0scbM%2F-McAdxsHNKXengcC3Daf%2F-McAipRwmeUDfF5ZE2dE%2FBattery_Cable.png?alt=media\&token=f7985e38-90a5-46e4-97ac-5da2fa6bed3c)
{% endtab %}
{% endtabs %}

## Macro shots of the various IC's

{% tabs %}
{% tab title="Chip 1" %}
![10 Amperes SFH Series Self Control Protector(SCP)](https://2395005476-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MJQb34R_xPz0ll0scbM%2F-Mc47OKbE9hdJOBfGn1S%2F-Mc49GKYUAkOvO3taTf-%2FPXL_20210613_142937978.jpg?alt=media\&token=a7360da2-fd7b-4a25-bae6-1239faaf7931)
{% endtab %}

{% tab title="Chips 2" %}
![??? - Guessing both are balance chips](https://2395005476-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MJQb34R_xPz0ll0scbM%2F-Mc47OKbE9hdJOBfGn1S%2F-Mc49GKU-Ynz9T4_bZre%2FPXL_20210613_142735502.jpg?alt=media\&token=5b1becbe-626c-45cb-bd04-0c54604985f0)
{% endtab %}

{% tab title="Chip 3" %}
![BQ28400 Netbook and Tablet Lithium ion gas gauge and protector](https://2395005476-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MJQb34R_xPz0ll0scbM%2F-Mc47OKbE9hdJOBfGn1S%2F-Mc49GK_-uAUE0A0HDmI%2FPXL_20210613_142719270.jpg?alt=media\&token=62f083f8-fd21-411a-ade5-7404f94548ec)
{% endtab %}

{% tab title="Chip 4" %}
![??? - Chip is unmarked, suspecting it's a temp probe logic](https://2395005476-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MJQb34R_xPz0ll0scbM%2F-Mc47OKbE9hdJOBfGn1S%2F-Mc49GKZWE03FI6o-atc%2FPXL_20210613_142658484.jpg?alt=media\&token=ddc120dc-bcf3-451e-99c5-133818211e52)
{% endtab %}
{% endtabs %}