Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community - FT86CLUB - View Single Post - light weight battery kills the alternator?

geraldjust · 06-13-2022, 03:33 AM

Controversial take but I wouldn't recommend lithium ion batteries for these cars. These cars were actually meant for AGM type. So the charging curve for the current sensor/temperature sensor. They have a very specific type on how it charges the battery. thats why these cars need the current sensor on the neg side of the battery.

The way the electrical charging system works is for any given current the car wants to then bring up the charge voltage on the alternator up. To counteract it and when averaging out current going in and out of the battery constantly, its basically net slightly positive tp be able to charge it.

Lithium ion battery on the other hand will charge with as much current you can throw at them. (as long as you dont exceed its max charging current). If you do, thats what the BMS is for. But how BMS works normally is by shutting off the "in" on the post on the battery. this will keep the battery safe but can cause huge voltage spikes from the alternator. So every 10-15 second sounds like the BMS interfering somehow.

Unfortunately, if those huge spiked did occur, they is always a chance you can damage internal charing components in the alternator. Or the BMS inside the lithium battery. Or both.

Honestly maybe try and get a smaller quality AMG type of battery.

06-13-2022, 03:33 AM	#4
geraldjust Senior Member Join Date: Jun 2018 Drives: MR2, Sliver BRZ Location: San Diego, CA Posts: 316 Thanks: 5 Thanked 261 Times in 123 Posts Mentioned: 40 Post(s)	Controversial take but I wouldn't recommend lithium ion batteries for these cars. These cars were actually meant for AGM type. So the charging curve for the current sensor/temperature sensor. They have a very specific type on how it charges the battery. thats why these cars need the current sensor on the neg side of the battery. The way the electrical charging system works is for any given current the car wants to then bring up the charge voltage on the alternator up. To counteract it and when averaging out current going in and out of the battery constantly, its basically net slightly positive tp be able to charge it. Lithium ion battery on the other hand will charge with as much current you can throw at them. (as long as you dont exceed its max charging current). If you do, thats what the BMS is for. But how BMS works normally is by shutting off the "in" on the post on the battery. this will keep the battery safe but can cause huge voltage spikes from the alternator. So every 10-15 second sounds like the BMS interfering somehow. Unfortunately, if those huge spiked did occur, they is always a chance you can damage internal charing components in the alternator. Or the BMS inside the lithium battery. Or both. Honestly maybe try and get a smaller quality AMG type of battery. __________________ Always looking to tinker with something..