diff --git a/CMakeLists.txt b/CMakeLists.txt
index 12d6dd6..872b267 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -31,6 +31,7 @@ add_executable(f00bar
   particles/list.c particles/list.h
   particles/map.c particles/map.h
 
+  modules/battery/battery.c modules/battery/battery.h
   modules/i3/i3.c modules/i3/i3.h
   modules/i3/dynlist-exposable.c modules/i3/dynlist-exposable.h
   modules/label/label.c modules/label/label.h
diff --git a/config.c b/config.c
index 9e3eae5..50ed835 100644
--- a/config.c
+++ b/config.c
@@ -13,6 +13,7 @@
 #include "particles/map.h"
 
 #include "module.h"
+#include "modules/battery/battery.h"
 #include "modules/i3/i3.h"
 #include "modules/label/label.h"
 #include "modules/clock/clock.h"
@@ -277,6 +278,27 @@ module_i3_from_config(const struct yml_node *node, const struct font *parent_fon
         right_spacing != NULL ? yml_value_as_int(right_spacing) : 0);
 }
 
+static struct module *
+module_battery_from_config(const struct yml_node *node,
+                           const struct font *parent_font)
+{
+    const struct yml_node *c = yml_get_value(node, "content");
+    const struct yml_node *poll_interval = yml_get_value(node, "poll_interval");
+    const struct yml_node *left_spacing = yml_get_value(node, "left_spacing");
+    const struct yml_node *right_spacing = yml_get_value(node, "right_spacing");
+
+    assert(yml_is_dict(c));
+    assert(poll_interval == NULL || yml_is_scalar(poll_interval));
+    assert(left_spacing == NULL || yml_is_scalar(left_spacing));
+    assert(right_spacing == NULL || yml_is_scalar(right_spacing));
+
+    return module_battery(
+        "BAT0", particle_from_config(c, parent_font),
+        poll_interval != NULL ? yml_value_as_int(poll_interval) : 30,
+        left_spacing != NULL ? yml_value_as_int(left_spacing) : 0,
+        right_spacing != NULL ? yml_value_as_int(right_spacing) : 0);
+}
+
 struct bar *
 conf_to_bar(const struct yml_node *bar)
 {
@@ -379,6 +401,8 @@ conf_to_bar(const struct yml_node *bar)
                     mods[idx] = module_xwindow_from_config(it.node, font);
                 else if (strcmp(mod_name, "i3") == 0)
                     mods[idx] = module_i3_from_config(it.node, font);
+                else if (strcmp(mod_name, "battery") == 0)
+                    mods[idx] = module_battery_from_config(it.node, font);
                 else
                     assert(false);
             }
diff --git a/modules/battery/battery.c b/modules/battery/battery.c
new file mode 100644
index 0000000..ad62164
--- /dev/null
+++ b/modules/battery/battery.c
@@ -0,0 +1,248 @@
+#include "battery.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <assert.h>
+
+#include <poll.h>
+
+#include <sys/stat.h>
+#include <fcntl.h>
+
+#include "../../bar.h"
+
+enum state { STATE_FULL, STATE_CHARGING, STATE_DISCHARGING };
+
+struct private {
+    struct particle *label;
+
+    int poll_interval;
+    char *battery;
+    char *manufacturer;
+    char *model;
+    long energy_full;
+
+    enum state state;
+    long capacity;
+    long energy;
+    long power;
+};
+
+static void
+destroy(struct module *mod)
+{
+    struct private *m = mod->private;
+    free(m->battery);
+    free(m->manufacturer);
+    free(m->model);
+
+    m->label->destroy(m->label);
+
+    free(m);
+    free(mod);
+}
+
+static struct exposable *
+content(const struct module *mod)
+{
+    const struct private *m = mod->private;
+    assert(m->state == STATE_FULL ||
+           m->state == STATE_CHARGING ||
+           m->state == STATE_DISCHARGING);
+
+    unsigned long energy = m->state == STATE_CHARGING
+        ? m->energy_full - m->energy : m->energy;
+
+    double hours_as_float;
+    if (m->state == STATE_FULL)
+        hours_as_float = 0.0;
+    else if (m->power > 0)
+        hours_as_float = (double)energy / m->power;
+    else
+        hours_as_float = 99.0;
+
+    unsigned long hours = hours_as_float;
+    unsigned long minutes = (hours_as_float - (double)hours) * 60;
+
+    char estimate[64];
+    snprintf(estimate, sizeof(estimate), "%02lu:%02lu", hours, minutes);
+
+    struct tag_set tags = {
+        .tags = (struct tag *[]){
+            tag_new_string("name", m->battery),
+            tag_new_string("manufacturer", m->manufacturer),
+            tag_new_string("model", m->model),
+            tag_new_string("state",
+                           m->state == STATE_FULL ? "full" :
+                           m->state == STATE_CHARGING ? "charging" :
+                           m->state == STATE_DISCHARGING ? "discharging" :
+                           "unknown"),
+            tag_new_int_range("capacity", m->capacity, 0, 100),
+            tag_new_string("estimate", estimate),
+        },
+        .count = 6,
+    };
+
+    struct exposable *exposable = m->label->instantiate(m->label, &tags);
+
+    tag_set_destroy(&tags);
+    return exposable;
+}
+
+static const char *
+readline_from_fd(int fd)
+{
+    static char buf[4096];
+
+    ssize_t sz = read(fd, buf, sizeof(buf) - 1);
+    lseek(fd, 0, SEEK_SET);
+
+    if (sz < 0)
+        return NULL;
+
+    buf[sz] = '\0';
+    for (ssize_t i = sz - 1; i >= 0 && buf[i] == '\n'; sz--)
+        buf[i] = '\0';
+
+    return buf;
+}
+
+static long
+readint_from_fd(int fd)
+{
+    const char *s = readline_from_fd(fd);
+    assert(s != NULL);
+
+    long ret;
+    int r = sscanf(s, "%lu", &ret);
+    assert(r == 1);
+
+    return ret;
+}
+
+static int
+run(struct module_run_context *ctx)
+{
+    const struct bar *bar = ctx->module->bar;
+    struct private *m = ctx->module->private;
+
+    int pw_fd = open("/sys/class/power_supply", O_RDONLY);
+    assert(pw_fd != -1);
+
+    int base_dir_fd = openat(pw_fd, m->battery, O_RDONLY);
+    assert(base_dir_fd != -1);
+
+    {
+        int fd = openat(base_dir_fd, "manufacturer", O_RDONLY);
+        assert(fd != -1);
+
+        m->manufacturer = strdup(readline_from_fd(fd));
+        close(fd);
+    }
+
+    {
+        int fd = openat(base_dir_fd, "model_name", O_RDONLY);
+        assert(fd != -1);
+
+        m->model = strdup(readline_from_fd(fd));
+        close(fd);
+    }
+
+    long energy_full_design = 0;
+    {
+        int fd = openat(base_dir_fd, "energy_full_design", O_RDONLY);
+        assert(fd != -1);
+
+        energy_full_design = readint_from_fd(fd);
+        close(fd);
+    }
+
+    {
+        int fd = openat(base_dir_fd, "energy_full", O_RDONLY);
+        assert(fd != -1);
+
+        m->energy_full = readint_from_fd(fd);
+        close(fd);
+    }
+
+    printf("%s: %s %s (at %.1f%% of original capacity)\n",
+           m->battery, m->manufacturer, m->model,
+           100.0 * m->energy_full / energy_full_design);
+
+    int status_fd = openat(base_dir_fd, "status", O_RDONLY);
+    assert(status_fd != -1);
+
+    int capacity_fd = openat(base_dir_fd, "capacity", O_RDONLY);
+    assert(capacity_fd != -1);
+
+    int energy_fd = openat(base_dir_fd, "energy_now", O_RDONLY);
+    assert(energy_fd != -1);
+
+    int power_fd = openat(base_dir_fd, "power_now", O_RDONLY);
+    assert(power_fd != -1);
+
+    do {
+        const char *status = readline_from_fd(status_fd);
+        if (strcmp(status, "Full") == 0)
+            m->state = STATE_FULL;
+        else if (strcmp(status, "Charging") == 0)
+            m->state = STATE_CHARGING;
+        else if (strcmp(status, "Discharging") == 0)
+            m->state = STATE_DISCHARGING;
+        else if (strcmp(status, "Unknown") == 0)
+            m->state = STATE_DISCHARGING;
+        else {
+            printf("unrecognized battery state: %s\n", status);
+            m->state = STATE_DISCHARGING;
+            assert(false && "unrecognized battery state");
+        }
+
+        m->capacity = readint_from_fd(capacity_fd);
+        m->energy = readint_from_fd(energy_fd);
+        m->power = readint_from_fd(power_fd);
+
+        //printf("capacity: %lu, energy: %lu, power: %lu\n",
+        //       m->capacity, m->energy, m->power);
+
+        bar->refresh(bar);
+
+        struct pollfd fds[] = {{.fd = ctx->abort_fd, .events = POLLIN}};
+        poll(fds, 1, m->poll_interval * 1000);
+
+        if (fds[0].revents & POLLIN)
+            break;
+    } while (true);
+
+    close(power_fd);
+    close(energy_fd);
+    close(capacity_fd);
+    close(status_fd);
+    close(base_dir_fd);
+    close(pw_fd);
+    return 0;
+}
+
+struct module *
+module_battery(const char *battery, struct particle *label,
+               int poll_interval_secs, int left_spacing, int right_spacing)
+{
+    struct private *m = malloc(sizeof(*m));
+    m->label = label;
+    m->poll_interval = poll_interval_secs;
+    m->battery = strdup(battery);
+    m->manufacturer = NULL;
+    m->model = NULL;
+
+    struct module *mod = malloc(sizeof(*mod));
+    mod->bar = NULL;
+    mod->private = m;
+    mod->run = &run;
+    mod->destroy = &destroy;
+    mod->content = &content;
+    mod->begin_expose = &module_default_begin_expose;
+    mod->expose = &module_default_expose;
+    mod->end_expose = &module_default_end_expose;
+    return mod;
+}
diff --git a/modules/battery/battery.h b/modules/battery/battery.h
new file mode 100644
index 0000000..400b3c1
--- /dev/null
+++ b/modules/battery/battery.h
@@ -0,0 +1,8 @@
+#pragma once
+
+#include "../../module.h"
+#include "../../particle.h"
+
+struct module *module_battery(
+    const char *battery, struct particle *label,
+    int poll_interval_secs, int left_spacing, int right_spacing);