Porsche A123 12v 40ah Lifepo4 660a Starter Battery
These batteries might just be the best option for car audio. They are compact and can pack a punch up to 660 amps in a burst. They also have a BMS inside already too which adds a layer of safety and they have the standard studs where you can make your connections with actual car wiring and clamp connectors.
These batteries are made where the BMS shuts off around 12.8v (3.2v per cell) at discharge. If you remove the BMS and put your own BMS in to let these discharge down to 10v you will get around full capacity. With the BMS cutoff at 12.75v we are getting around 31ah. The best part is you can pair these with an alternator for car audio and keep the packs above 12.75v. These can charge up to 14.8v, it even says it on the sticker of the battery. Of course, for longevity, we recommend to limit charge to 14.6v but these are made for Porsche and the specs show 14.8v max full charge. Since these were for starting cars they were not cycled too many times which is why they are testing so good.
Bottom line, amazing value for car audio if you can keep your voltage above 12.8v. For solar energy storage and RV applications just remember with the built in BMS cut off at 12.8v you will get around 75% of the capacity. You can unlock the other 25% by installing your own BMS and removing the one included.
In our opinion, having an actual Porsche battery bank is pretty awesome. Here you can buy Porsche batteries at Kia prices.
Model of the battery is 9j1.915.105.e. If you google this part number you will see they are crazy expensive elsewhere. We test every battery to make sure they charge fully and discharge down to 12.8v so they are all testing consistently.
Length: 6.25 inches
Width: 6.75 inches
Height: 7.5 inches
14.3lb.
Note: these are made with 8 3.2v 20ah Lifepo4 A123 cells in 4s2p configuration. The battery will likely read 0 volts when you get it. Just apply a 14.6v charge and after a few seconds you will hear the contactor trigger on. Then the battery will charge and discharge like normal so long as it is above 12.8v. Do not use an alternator that is above 14.8v output. Recommended max alternator output voltage for longevity is 14.6v.