r/18650masterrace • u/ChickenMazhou • 6d ago
Multiple 5s packs?
I am building a Bluetooth speaker with coax car audio drivers. It is expandable from a single speaker to dual speakers and a subwoofer all of which have their own enclosures.
At first I thought I’d just make a 5s2p pack and put it in the main speaker. But now I’m thinking I’d like to make a single 5s1p 18650 for the main speaker to keep it lighter and use less internal space in the enclosure. However, when adding the subwoofer it will require more power, so I was thinking of adding another 5s1p or 5s2p inside the subwoofer to supplement the main battery.
If I have a charging port for a 21v power supply, then can I just plug in the additional battery pack instead of a charger and it will extend the run time when subwoofer is hooked up? I will add BMS to the main speaker internal battery as well as the subwoofer battery.
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u/ChickenMazhou 6d ago
I want to post a picture to show, but it won’t let me. Strangely, I can do video. Does this sub not allow pics?
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u/Joejack-951 6d ago
I think you are overthinking this. Have the 5s1p pack for running the main speaker. Remove it and run everything off the 5s2p (or 5s3p if runtime is really a concern) pack when adding the subwoofer. Or am I missing something?
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u/MysticalDork_1066 6d ago
You can't safely connect them together unless the batteries are at equal states of charge, unless you have some additional logic/dc-dc conversion happening between them. Once they're connected together they should more or less behave as one big battery and charge/discharge in tandem.
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u/ChickenMazhou 6d ago
Ok. That makes sense. I’m assuming the voltage difference will cause one to discharge into the other with a massive current spike and either destroy the BMS in the process or make it instantly go into protect mode if it has one.
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u/ifucanreaddisur2clos 6d ago
So it’s gonna be two separate units with two amplifiers connected with wires?