1. Ampere meter can only be connected to 5v input end of the module.
2. It is better that the charging current is 37% of the battery capacity. If you charge to the battery of 1000mAH, current of 400 is enough.
3. The connection wire should not be too thick.
4. Make sure the connect point is good.
5. If the input voltage is too high, like 5.2v, the current will be less than 1000mA, it is normal. It is protection function, auto-substract the charging current to avoid burn damage to chip.
6. NO Reveral polarity.