Want to charge 48v batteries with 12v van alternator. I’ve read discussions on this issue. The general consensus is use a 48v alt or a Spencer charger. There is a Victron Orion TR Smart 12/48 isolated charger. I’ve read that the isolated charger can’t share a common chassis ground, yet 48v inverters and batteries in a vehicle must be grounded to the vehicle chassis. Why is it that the 48v inverter and batteries can share a common chassis ground with the 12v starter battery, but not the Victron 12/48 isolated charger?
I don’t know if I’ve come across an inverter that recommends grounding the inverter supply to the vehicle chassis. Positive and negative should run direct to the 48v battery bank.
The “chassis” of the inverter is recommended to be grounded to the vehicle chassis for safety in the case of the unit having a gfci to complete the circuit on the a/c side. The chassis of the inverter is typically isolated from the dc circuitry, so grounding the inverter chassis does not create a ground loop between your 12 and 48v systems
What model of inverter are you using? Unless its something that does have the dc ground bonded to chassis, if your ground is run direct from inverter to 48v battery you have an isolated system and can use the isolated charger
I edited my original post. It’s grounding the 48v batteries to the same chassis ground share with 12 volt starter battery. I should be more specific the 48v battery leads are directly connected to the invert and the negative led is connected to chassis ground as well. The inverter and batteries will share a common ground with 12 volt system.
Move your ground on the inverter, create the isolated circuits and use the isolated charger. Nothing on the 48v side needs to be grounded to the vehicle chassis. The “chassis” or case of the inverter should be grounded to the vehicle to allow the gfci to function (if equipped)
An isolated charger can’t (or at least shouldn’t) be used on a non isolated (common ground) because of the type of circuitry involved. The isolated charger uses a transformer to physically separate the 12 and 48v sides of the charger, connecting both sides of it with a common ground is probably a good way to let the magic smoke out of it
That make sense to keep the 48v system isolated the only place a ground fault would occur is between the 48v wires. I just trying to be as safe as I can. I’ve seen a lot of systems that ground 48v system to the chassis. I guess the issue is not a shared ground, until you mix 12v charging and converting That solves a few issues fro me.
If the 48v side is not grounded to chassis you eliminate the possibility of a ground fault to the vehicle chassis should a wire rub through or be damaged. Can’t complete a circuit that doesn’t exist!
But again in the case of inverter use, grounding the inverter chassis to the vehicle allows the gfci to do its job should you be touching part of the vehicle while sticking a fork in the socket lol
48v systems in vehicles is still a new area of discussion. Lots of confusion when the are 12v and 48v systems. Especially when you’re trying to convert and charge. Maintaining the 12v isolation helps with safety for 12v loads that have a much higher chance of ground faults. I thank you for your input.
Where have you read that the isolated version can not share a common ground, I and others here always consider that you can use an isolated version with a common ground. You may be better off trying to confirm this.
Ran into another conundrum. If I use an isolated 48v to 12v converter for 12v loads I can’t share a common ground with the start battery. That isn’t good. Ground faults are much more likely with the 12v loads. I guess there’s the option of an ac to dc converter that would share a common ground. Don’t want to use the start battery for dc loads being used when vehicle is not running.
Is that for step-up chargers or step-down converters? Could a 48/12 voltage converter share a ground with starter battery on the 12v low side?
As far as the DC to DC charger is concerned it does not matter if both batteries share a common ground. The reason people want isolated is if they have sensitive equipment on the output and a noisy voltage on the input so the output is cleaner.