Direct Battery to Battery Charging
Posted: Mon Jul 28, 2025 2:05 pm
Let me start by saying I'm not sure this is the right part of the forum, so feel free to yell at me and move this thread.
Also, I fully understand just connecting two different batteries directly is unsafe - I don't plan to do that.
What I'm wondering about is what it would take to basically DC-DC charge high voltage batteries. Specifically, my next race car project will likely involve events in remote locations (salt flats, lake beds, abandoned runways, etc) where I will need to recharge the car between runs, and will only have the power source I bring with me (generator, battery). I seems wasteful and slow to have a high voltage battery to store power and then use an inverter to create AC that a typical on board charger then converts back to DC to charge the car's battery. I'd love to have a solution where I could simply use something to control the charge of the race car battery using a pack of similar voltage but much higher capacity. (ex: The race car will likely have a roughly 20-30kWh battery, and I can find used Tesla 75kWh batteries pretty cheap right now)
First, does anyone know of a commercially available component that can do this? All I can find are the components for DIY RVs/vans that are for 48V or below)
If not, is there a way to do this by modifying available EV/hybrid components?
Also, I fully understand just connecting two different batteries directly is unsafe - I don't plan to do that.
What I'm wondering about is what it would take to basically DC-DC charge high voltage batteries. Specifically, my next race car project will likely involve events in remote locations (salt flats, lake beds, abandoned runways, etc) where I will need to recharge the car between runs, and will only have the power source I bring with me (generator, battery). I seems wasteful and slow to have a high voltage battery to store power and then use an inverter to create AC that a typical on board charger then converts back to DC to charge the car's battery. I'd love to have a solution where I could simply use something to control the charge of the race car battery using a pack of similar voltage but much higher capacity. (ex: The race car will likely have a roughly 20-30kWh battery, and I can find used Tesla 75kWh batteries pretty cheap right now)
First, does anyone know of a commercially available component that can do this? All I can find are the components for DIY RVs/vans that are for 48V or below)
If not, is there a way to do this by modifying available EV/hybrid components?
I believe there is a thread on controlling the monster, it has a 30kw limit so recharging in an hr from completely drained .... LTO cells or something that can handle very high rate charging and discharging without heat or cycle life being affected ..... I'm guessing weight distribution in a land speed vehicle would be able to accommodate the added weight LTO cells would create, offset by the ability to hold voltage at a very high discharge rate and no thermal runaway fire risk ......