Sunder wrote:I'm planning on getting around this by installing a second LiFePo4 battery in the cavity where the charger sits. I'm hoping to install charger that will charge the LiFePo4 battery when the Lead Acid battery is >12v, but cut off as soon as it's 11.9v, preserving the Lead Acid battery from over discharge.
Not sure how I'm going to do this yet, because I don't want to spend $400+ on a professional kit, but I might be able to fiddle with a battery management system to get it to do this. At worse, I put in a low voltage alarm.
There are a number of DC-DC chargers available. Most (but not all!) will cut out when the supplying battery falls below around 12.8.
They also usually have current limiting, so you don't hit the 12V circuit with a high surge current when the second battery is low, as would happen if you just used a voltage controlled relay. Whenever the PHEV is on, the 12V battery sits at around 14.2V, so this arrangement should work fine. The PHEV with the Wi-Fi module also has an auto battery top-up once a day, so, this could work very well in keeping a second battery topped up as well and not run the risk of running the 12V battery down.