EZGO TXT 875E: Battery Help Needed

[Bruiser Smith]

Originally Posted by BobBoyce

48V lead acid pack chargers tend to cut off around 60V +/- 1V

The lithium pack itself powers the BMS on most of the lower end BMSs. You plug in the charger, and the BMS shuts off the charger port when it reaches the charger shutoff voltage. Once the pack is balanced during or after charging, the BMS goes into a low power idle state where it draws very little power. The BMS stays in the idle state most of the time, then checks the pack for balance quickly once in a while, then goes back into idle state until the pack voltage drops to the low power cutoff voltage. Then it shuts off the load (cart). Most people charge their packs before they get anywhere near the low voltage cutoff point. It extends the life of the pack to not run it down too much. When you power up the charger, the cycle repeats.

I used one relay contact to control AC power to shut off the charger, and the other contact to shut down the cart if battery voltage dropped too low.

Ok, so far I've got the Leaf cells hooked up in series along with the 14s BMS from your post instructions, but it's not connected to the cart or anything else at the moment. In theory can I just connect this to my cart electrical system and then charge off the old lead acid charger? When you say that the BMS 'shuts off the charger port', do you mean in the individual Leaf cells or somewhere else? And is there a wiring diagram for the relay somewhere? I have one ordered but am trying to wrap my head around using it with the old lead acid charger.

Also, how does switching to Leaf cells affect getting power to the 12v circuit? Previously there was just a wire going to one of the batteries tops. I'm pretty sure it was hooked to the 2nd in the series, hence 12v - I think, anyways. I've seen that folks buy converters and am happy to do so if this is the right way to get 12v powered as well for the accessory harness.

Here's some progress pics for the body - it's a Burning Man *sound* art car. Yes, those are subwoofers which will go on the platform

[BobBoyce]

Originally Posted by Bruiser Smith

Ok, so far I've got the Leaf cells hooked up in series along with the 14s BMS from your post instructions, but it's not connected to the cart or anything else at the moment. In theory can I just connect this to my cart electrical system and then charge off the old lead acid charger? When you say that the BMS 'shuts off the charger port', do you mean in the individual Leaf cells or somewhere else? And is there a wiring diagram for the relay somewhere? I have one ordered but am trying to wrap my head around using it with the old lead acid charger.

Also, how does switching to Leaf cells affect getting power to the 12v circuit? Previously there was just a wire going to one of the batteries tops. I'm pretty sure it was hooked to the 2nd in the series, hence 12v - I think, anyways. I've seen that folks buy converters and am happy to do so if this is the right way to get 12v powered as well for the accessory harness.

Here's some progress pics for the body - it's a Burning Man *sound* art car. Yes, those are subwoofers which will go on the platform

There were wiring diagrams in that thread that showed the relay wiring. I used one set of the relay contacts to turn the 120VAC power on and off to my charger. As for 12V, use a voltage reducer wired to the controller B+ side of the solenoid. That turns off when the key is off, and if the pack voltage drops to the cutoff voltage.