diff --git a/health/aidl/default/Health.cpp b/health/aidl/default/Health.cpp
new file mode 100644
index 0000000..2d91ce0
--- /dev/null
+++ b/health/aidl/default/Health.cpp
@@ -0,0 +1,341 @@
+/*
+ * Copyright (C) 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "health-impl/Health.h"
+
+#include <android-base/file.h>
+#include <android-base/logging.h>
+#include <android/binder_manager.h>
+#include <android/binder_process.h>
+#include <android/hardware/health/translate-ndk.h>
+#include <health/utils.h>
+
+#include "LinkedCallback.h"
+#include "health-convert.h"
+
+using std::string_literals::operator""s;
+
+namespace aidl::android::hardware::health {
+
+namespace {
+// Wrap LinkedCallback::OnCallbackDied() into a void(void*).
+void OnCallbackDiedWrapped(void* cookie) {
+    LinkedCallback* linked = reinterpret_cast<LinkedCallback*>(cookie);
+    linked->OnCallbackDied();
+}
+}  // namespace
+
+/*
+// If you need to call healthd_board_init, construct the Health instance with
+// the healthd_config after calling healthd_board_init:
+class MyHealth : public Health {
+  protected:
+    MyHealth() : Health(CreateConfig()) {}
+  private:
+    static std::unique_ptr<healthd_config> CreateConfig() {
+      auto config = std::make_unique<healthd_config>();
+      ::android::hardware::health::InitHealthdConfig(config.get());
+      healthd_board_init(config.get());
+      return std::move(config);
+    }
+};
+*/
+Health::Health(std::string_view instance_name, std::unique_ptr<struct healthd_config>&& config)
+    : instance_name_(instance_name),
+      healthd_config_(std::move(config)),
+      death_recipient_(AIBinder_DeathRecipient_new(&OnCallbackDiedWrapped)) {
+    battery_monitor_.init(healthd_config_.get());
+}
+
+//
+// Getters.
+//
+
+template <typename T>
+static ndk::ScopedAStatus GetProperty(::android::BatteryMonitor* monitor, int id, T defaultValue,
+                                      T* out) {
+    *out = defaultValue;
+    struct ::android::BatteryProperty prop;
+    ::android::status_t err = monitor->getProperty(static_cast<int>(id), &prop);
+    if (err == ::android::OK) {
+        *out = static_cast<T>(prop.valueInt64);
+    } else {
+        LOG(DEBUG) << "getProperty(" << id << ")"
+                   << " fails: (" << err << ") " << ::android::statusToString(err);
+    }
+
+    switch (err) {
+        case ::android::OK:
+            return ndk::ScopedAStatus::ok();
+        case ::android::NAME_NOT_FOUND:
+            return ndk::ScopedAStatus::fromExceptionCode(EX_UNSUPPORTED_OPERATION);
+        default:
+            return ndk::ScopedAStatus::fromServiceSpecificErrorWithMessage(
+                    IHealth::STATUS_UNKNOWN, ::android::statusToString(err).c_str());
+    }
+}
+
+ndk::ScopedAStatus Health::getChargeCounterUah(int32_t* out) {
+    return GetProperty<int32_t>(&battery_monitor_, ::android::BATTERY_PROP_CHARGE_COUNTER, 0, out);
+}
+
+ndk::ScopedAStatus Health::getCurrentNowMicroamps(int32_t* out) {
+    return GetProperty<int32_t>(&battery_monitor_, ::android::BATTERY_PROP_CURRENT_NOW, 0, out);
+}
+
+ndk::ScopedAStatus Health::getCurrentAverageMicroamps(int32_t* out) {
+    return GetProperty<int32_t>(&battery_monitor_, ::android::BATTERY_PROP_CURRENT_AVG, 0, out);
+}
+
+ndk::ScopedAStatus Health::getCapacity(int32_t* out) {
+    return GetProperty<int32_t>(&battery_monitor_, ::android::BATTERY_PROP_CAPACITY, 0, out);
+}
+
+ndk::ScopedAStatus Health::getEnergyCounterNwh(int64_t* out) {
+    return GetProperty<int64_t>(&battery_monitor_, ::android::BATTERY_PROP_ENERGY_COUNTER, 0, out);
+}
+
+ndk::ScopedAStatus Health::getChargeStatus(BatteryStatus* out) {
+    return GetProperty(&battery_monitor_, ::android::BATTERY_PROP_BATTERY_STATUS,
+                       BatteryStatus::UNKNOWN, out);
+}
+
+ndk::ScopedAStatus Health::getDiskStats(std::vector<DiskStats>*) {
+    // This implementation does not support DiskStats. An implementation may extend this
+    // class and override this function to support disk stats.
+    return ndk::ScopedAStatus::fromExceptionCode(EX_UNSUPPORTED_OPERATION);
+}
+
+ndk::ScopedAStatus Health::getStorageInfo(std::vector<StorageInfo>*) {
+    // This implementation does not support StorageInfo. An implementation may extend this
+    // class and override this function to support storage info.
+    return ndk::ScopedAStatus::fromExceptionCode(EX_UNSUPPORTED_OPERATION);
+}
+
+ndk::ScopedAStatus Health::getHealthInfo(HealthInfo* out) {
+    battery_monitor_.updateValues();
+
+    // TODO(b/177269435): BatteryMonitor should store AIDL HealthInfo instead.
+    auto health_info_2_1 = battery_monitor_.getHealthInfo_2_1();
+    if (!::android::h2a::translate(health_info_2_1, out)) {
+        return ndk::ScopedAStatus::fromServiceSpecificErrorWithMessage(
+                IHealth::STATUS_UNKNOWN, "Cannot translate HIDL HealthInfo to AIDL");
+    }
+
+    // Fill in storage infos; these aren't retrieved by BatteryMonitor.
+    if (auto res = getStorageInfo(&out->storageInfos); !res.isOk()) {
+        if (res.getServiceSpecificError() == 0 &&
+            res.getExceptionCode() != EX_UNSUPPORTED_OPERATION) {
+            return ndk::ScopedAStatus::fromServiceSpecificErrorWithMessage(
+                    IHealth::STATUS_UNKNOWN,
+                    ("getStorageInfo fails: " + res.getDescription()).c_str());
+        }
+        LOG(DEBUG) << "getHealthInfo: getStorageInfo fails with service-specific error, clearing: "
+                   << res.getDescription();
+        out->storageInfos = {};
+    }
+    if (auto res = getDiskStats(&out->diskStats); !res.isOk()) {
+        if (res.getServiceSpecificError() == 0 &&
+            res.getExceptionCode() != EX_UNSUPPORTED_OPERATION) {
+            return ndk::ScopedAStatus::fromServiceSpecificErrorWithMessage(
+                    IHealth::STATUS_UNKNOWN,
+                    ("getDiskStats fails: " + res.getDescription()).c_str());
+        }
+        LOG(DEBUG) << "getHealthInfo: getDiskStats fails with service-specific error, clearing: "
+                   << res.getDescription();
+        out->diskStats = {};
+    }
+
+    // A subclass may want to update health info struct before returning it.
+    UpdateHealthInfo(out);
+
+    return ndk::ScopedAStatus::ok();
+}
+
+binder_status_t Health::dump(int fd, const char**, uint32_t) {
+    battery_monitor_.dumpState(fd);
+
+    ::android::base::WriteStringToFd("\ngetHealthInfo -> ", fd);
+    HealthInfo health_info;
+    auto res = getHealthInfo(&health_info);
+    if (res.isOk()) {
+        ::android::base::WriteStringToFd(health_info.toString(), fd);
+    } else {
+        ::android::base::WriteStringToFd(res.getDescription(), fd);
+    }
+
+    fsync(fd);
+    return STATUS_OK;
+}
+
+std::optional<bool> Health::ShouldKeepScreenOn() {
+    if (!healthd_config_->screen_on) {
+        return std::nullopt;
+    }
+
+    HealthInfo health_info;
+    auto res = getHealthInfo(&health_info);
+    if (!res.isOk()) {
+        return std::nullopt;
+    }
+
+    ::android::BatteryProperties props = {};
+    convert(health_info, &props);
+    return healthd_config_->screen_on(&props);
+}
+
+namespace {
+bool IsDeadObjectLogged(const ndk::ScopedAStatus& ret) {
+    if (ret.isOk()) return false;
+    if (ret.getStatus() == ::STATUS_DEAD_OBJECT) return true;
+    LOG(ERROR) << "Cannot call healthInfoChanged on callback: " << ret.getDescription();
+    return false;
+}
+}  // namespace
+
+//
+// Subclass helpers / overrides
+//
+
+void Health::UpdateHealthInfo(HealthInfo* /* health_info */) {
+    /*
+        // Sample code for a subclass to implement this:
+        // If you need to modify values (e.g. batteryChargeTimeToFullNowSeconds), do it here.
+        health_info->batteryChargeTimeToFullNowSeconds = calculate_charge_time_seconds();
+
+        // If you need to call healthd_board_battery_update, modify its signature
+        // and implementation to operate on HealthInfo directly, then call:
+        healthd_board_battery_update(health_info);
+    */
+}
+
+//
+// Methods that handle callbacks.
+//
+
+ndk::ScopedAStatus Health::registerCallback(const std::shared_ptr<IHealthInfoCallback>& callback) {
+    if (callback == nullptr) {
+        // For now, this shouldn't happen because argument is not nullable.
+        return ndk::ScopedAStatus::fromExceptionCode(EX_NULL_POINTER);
+    }
+
+    {
+        std::lock_guard<decltype(callbacks_lock_)> lock(callbacks_lock_);
+        callbacks_.emplace_back(LinkedCallback::Make(ref<Health>(), callback));
+        // unlock
+    }
+
+    HealthInfo health_info;
+    if (auto res = getHealthInfo(&health_info); !res.isOk()) {
+        LOG(WARNING) << "Cannot call getHealthInfo: " << res.getDescription();
+        // No health info to send, so return early.
+        return ndk::ScopedAStatus::ok();
+    }
+
+    if (auto res = callback->healthInfoChanged(health_info); IsDeadObjectLogged(res)) {
+        (void)unregisterCallback(callback);
+    }
+    return ndk::ScopedAStatus::ok();
+}
+
+ndk::ScopedAStatus Health::unregisterCallback(
+        const std::shared_ptr<IHealthInfoCallback>& callback) {
+    if (callback == nullptr) {
+        // For now, this shouldn't happen because argument is not nullable.
+        return ndk::ScopedAStatus::fromExceptionCode(EX_NULL_POINTER);
+    }
+
+    std::lock_guard<decltype(callbacks_lock_)> lock(callbacks_lock_);
+
+    auto matches = [callback](const auto& linked) {
+        return linked->callback() == callback;  // compares shared_ptr
+    };
+    auto it = std::remove_if(callbacks_.begin(), callbacks_.end(), matches);
+    bool removed = (it != callbacks_.end());
+    callbacks_.erase(it, callbacks_.end());  // calls unlinkToDeath on deleted callbacks.
+    return removed ? ndk::ScopedAStatus::ok()
+                   : ndk::ScopedAStatus::fromExceptionCode(EX_ILLEGAL_ARGUMENT);
+}
+
+// A combination of the HIDL version
+//   android::hardware::health::V2_1::implementation::Health::update() and
+//   android::hardware::health::V2_1::implementation::BinderHealth::update()
+ndk::ScopedAStatus Health::update() {
+    HealthInfo health_info;
+    if (auto res = getHealthInfo(&health_info); !res.isOk()) {
+        LOG(DEBUG) << "Cannot call getHealthInfo for update(): " << res.getDescription();
+        // Propagate service specific errors. If there's none, report unknown error.
+        if (res.getServiceSpecificError() != 0 ||
+            res.getExceptionCode() == EX_UNSUPPORTED_OPERATION) {
+            return res;
+        }
+        return ndk::ScopedAStatus::fromServiceSpecificErrorWithMessage(
+                IHealth::STATUS_UNKNOWN, res.getDescription().c_str());
+    }
+    battery_monitor_.logValues();
+    OnHealthInfoChanged(health_info);
+    return ndk::ScopedAStatus::ok();
+}
+
+void Health::OnHealthInfoChanged(const HealthInfo& health_info) {
+    // Notify all callbacks
+    std::unique_lock<decltype(callbacks_lock_)> lock(callbacks_lock_);
+    // is_dead notifies a callback and return true if it is dead.
+    auto is_dead = [&](const auto& linked) {
+        auto res = linked->callback()->healthInfoChanged(health_info);
+        return IsDeadObjectLogged(res);
+    };
+    auto it = std::remove_if(callbacks_.begin(), callbacks_.end(), is_dead);
+    callbacks_.erase(it, callbacks_.end());  // calls unlinkToDeath on deleted callbacks.
+    lock.unlock();
+
+    // Let HalHealthLoop::OnHealthInfoChanged() adjusts uevent / wakealarm periods
+}
+
+void Health::BinderEvent(uint32_t /*epevents*/) {
+    if (binder_fd_ >= 0) {
+        ABinderProcess_handlePolledCommands();
+    }
+}
+
+void Health::OnInit(HalHealthLoop* hal_health_loop, struct healthd_config* config) {
+    LOG(INFO) << instance_name_ << " instance initializing with healthd_config...";
+
+    // Similar to HIDL's android::hardware::health::V2_1::implementation::HalHealthLoop::Init,
+    // copy configuration parameters to |config| for HealthLoop (e.g. uevent / wake alarm periods)
+    *config = *healthd_config_.get();
+
+    binder_status_t status = ABinderProcess_setupPolling(&binder_fd_);
+
+    if (status == ::STATUS_OK && binder_fd_ >= 0) {
+        std::shared_ptr<Health> thiz = ref<Health>();
+        auto binder_event = [thiz](auto*, uint32_t epevents) { thiz->BinderEvent(epevents); };
+        if (hal_health_loop->RegisterEvent(binder_fd_, binder_event, EVENT_NO_WAKEUP_FD) != 0) {
+            PLOG(ERROR) << instance_name_ << " instance: Register for binder events failed";
+        }
+    }
+
+    std::string health_name = IHealth::descriptor + "/"s + instance_name_;
+    CHECK_EQ(STATUS_OK, AServiceManager_addService(this->asBinder().get(), health_name.c_str()))
+            << instance_name_ << ": Failed to register HAL";
+
+    LOG(INFO) << instance_name_ << ": Hal init done";
+}
+
+// Unlike hwbinder, for binder, there's no need to explicitly call flushCommands()
+// in PrepareToWait(). See b/139697085.
+
+}  // namespace aidl::android::hardware::health