Direct Battery to Battery Charging

[P.S.Mangelsdorf]

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?

[tom91]

https://store.advantics.fr/power-conver ... ct_variant

Something like this could do it. Or any other DC-DC converter, like ones sometimes used in charging station or large PV setups.

https://www.tame-power.com/en/guide/dc- ... tric-cars/
https://www.evchargermodule.com/product ... ule-dc-dc/

[Zieg]

Don't forget to check the rulebook, SCCA regs have certain requirements for dc charging that you'll have to make sure you comply with. Is battery swapping an option?

[P.S.Mangelsdorf]

Don't forget to check the rulebook, SCCA regs have certain requirements for dc charging that you'll have to make sure you comply with. Is battery swapping an option?

Its SCTA, and the rules are not terribly detailed, but do require submitting detailed info to the EV committee ahead of time.

I don't love the idea of an easily swapable battery in a land speed car, but that's probably an option.

[P.S.Mangelsdorf]

https://store.advantics.fr/power-conver ... ct_variant

Something like this could do it. Or any other DC-DC converter, like ones sometimes used in charging station or large PV setups.

https://www.tame-power.com/en/guide/dc- ... tric-cars/
https://www.evchargermodule.com/product ... ule-dc-dc/

Thanks! I'll take a look at those.

[Jacobsmess]

Just throwing stuff out here but wouldn't a Prius inverter and an OI board be able to handle this sort of application?

[johu]

Yes, in battery charging mode. Just need to make sure the source battery is always lower voltage than the target battery (when using boost mode)

[T1Terry]

What voltages are you talking about here with you land speed racer? Could the Buck/Boost section of a Lexus GS450H inverter perform a function like that ..... I watched Gregski's video of the Buck/Boost section being expertly disassembled .... where Greg held the video camera 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 ......

T1 Terry

[P.S.Mangelsdorf]

Just throwing stuff out here but wouldn't a Prius inverter and an OI board be able to handle this sort of application?

Well that would be awesome because the local pull-your-own junkyard always has a bunch of Priuses. And their prices are dirt cheap.

Yes, in battery charging mode. Just need to make sure the source battery is always lower voltage than the target battery (when using boost mode)

So, in practice would that basically look like your charger in Lab update 55 (https://www.youtube.com/watch?v=_BDJ7N_YjAU) but without the rectifier, and using the Prius specific control board rather than the generic?

[johu]

Sort of, even the generic one would be easy to adapt as it's just 1 nfet to make the PWM 12V

[P.S.Mangelsdorf]

Thanks all for the input and help! I will definitely report back when I build this, but it's going to be a couple of months. Glad to have an idea of feasibility and the semblance of a plan in place.

[Also Johannes I tried to use the "Accept this answer"/"Solved" button and got a 404 error, just FYI]

[AMRC]

Hi
Im trying design a Boost from 10 volts do 300v, then with Openinverter as buck charger to transfer energy
Some done work https://github.com/AmandioCordeiro/FREE-DC-DC-12-48-311

Regards
Amândio Miguel