raresserban
10 µW
- Joined
- Jun 17, 2020
- Messages
- 6
Hello guys,
So I have a 5S2P pack I made for a bluetooth speaker (uses TPA3166D2 amp), protected with a BMS board with balancing.
I first used the pack directly to connect to the amplifier, and it worked fine, and the battery life was really good, since pack starts at 21V and then goes down to 14-15V, but this means I was losing amp power.
So I added a boost converter to 24V to get a boost to amp power.
The problem is that now the battery life is much shorter (expected), but the battery doesn't seem to go down to quite "0%" anymore.
I also have one of those cheap battery indicators, the ones that have 4 colored lines and a red outline.
Without the boost converter, I could see the indicator slowly losing lines and then just remained with the red outline (so voltage was below 16.5V for the whole pack, <3.3V per cell).
With the boost converter, the indicator remains at one line (voltage between 16.5V-17.5V for whole pack, between 3.3V-3.5V per cell) and then the battery shuts off, probably because the BMS cuts off. Then, if I remove the load and leave it like 5 minutes, the battery is back, again the indicator displays one line remaining. The indicator never goes to a red outline, so the cells never have <3.3V in them.
I am assuming this is because of a voltage drop when there is a load applied, but I want to know why this is the case and why it impacts the battery so much. Let's say that at half volume the amp has peak power consumption at 24V*3A=72W, so that's ~4.4A at 16.5V. The battery I use is LG INR18650-M36, which should supply up to 5A/cell, so a 2P configuration should provide 10A, so 4.4A doesn't seem that much.
Can somebody better explain to me why the big voltage drop and why the BMS cuts off (even though it should cut off at 2.8V per cell), and how I can improve the battery life?Should I just remove the boost converter, or dial it down to 22V or something else that I can try?
Thanks!
So I have a 5S2P pack I made for a bluetooth speaker (uses TPA3166D2 amp), protected with a BMS board with balancing.
I first used the pack directly to connect to the amplifier, and it worked fine, and the battery life was really good, since pack starts at 21V and then goes down to 14-15V, but this means I was losing amp power.
So I added a boost converter to 24V to get a boost to amp power.
The problem is that now the battery life is much shorter (expected), but the battery doesn't seem to go down to quite "0%" anymore.
I also have one of those cheap battery indicators, the ones that have 4 colored lines and a red outline.
Without the boost converter, I could see the indicator slowly losing lines and then just remained with the red outline (so voltage was below 16.5V for the whole pack, <3.3V per cell).
With the boost converter, the indicator remains at one line (voltage between 16.5V-17.5V for whole pack, between 3.3V-3.5V per cell) and then the battery shuts off, probably because the BMS cuts off. Then, if I remove the load and leave it like 5 minutes, the battery is back, again the indicator displays one line remaining. The indicator never goes to a red outline, so the cells never have <3.3V in them.
I am assuming this is because of a voltage drop when there is a load applied, but I want to know why this is the case and why it impacts the battery so much. Let's say that at half volume the amp has peak power consumption at 24V*3A=72W, so that's ~4.4A at 16.5V. The battery I use is LG INR18650-M36, which should supply up to 5A/cell, so a 2P configuration should provide 10A, so 4.4A doesn't seem that much.
Can somebody better explain to me why the big voltage drop and why the BMS cuts off (even though it should cut off at 2.8V per cell), and how I can improve the battery life?Should I just remove the boost converter, or dial it down to 22V or something else that I can try?
Thanks!