EEMB Lithium Polymer battery 3.7V 3700mAh 103395 Lipo Rechargeable Battery Pack with wire JST Connector for LED and Wireless Device-confirm device & connector polarity before purchase

I am currently amusing myself making portable audio equipment. The main concern with Lithium battery power is safety. This battery has battery protection built in. I can use it with cheap chargers and with cheap and poorly specified Bluetooth modules and class D amps with confidence that abuse cannot be catastrophic. It also has a handsom capacity. My diy Bluetooth amp lasts ages using it 3.7Ahrs! I must add a further caution for users after having read other comments. Li batteries are dangerous when charged incorrectly particularly when overcharged. This one has a protection circuit built-in. However, I would say that it should not be charged directly from the likes of phone or other plugin usb power supplies. Use one of the many cheap charger boards available that will automatically reduce the charge current near full charge and shut off charging when the voltage reaches 4.2v. the battery will also last longer and be safer if the charge current is limited to 1/3rd of capacity or less. No more that about 1A to 1.2A. This increases charge time but is safer and less fatiguing on batter life. Some usb supplies only limit at 2A or even 3A and have no shut down. Be cautious!

Had to swap the connector polarity, it's annoying that there is no standardisation

Bought to experiment with RasPi zero, pico etc with suitable power adapters. It needs to have the polarity of the connector changed to match the needs of the boards. Some careful work with a very small screwdriver to ease the connectors out of the housing and swap over.

Used to replace a battery in a radio which had stopped holding a charge. Came well packaged, connector was as described. Works great

Good quality 3700mAh battery but be mindful of the polarity of your application, as clearly stated by the manufacturer. These appeared to have a JST connector who's polarity is typically found in Radio Controlled toy world; the Internet of Things seems to use the opposite (i.e. there is no "standard" for polarity on these type of connectors) If you're very careful it's possible to poke out the metal conductors from the plastic housing of the JST connector and reinsert the desired way around.

No problems, took approx 1hr to fully charge. Using the chsrger module.

Yet to try these in a circuit but noticed the JST connector is the opposite way round to everything else I've ever come across. Please check your polarity!

Packaging could be a little better and more sturdy but okay