[Overlander23]

Couple questions about the "accessories" side of the HV equation.

Pack is 205v nominal. I've got a Soliton-1, so precharge to the controller, etc is taken care of internally.

What about other stuff, namely the DC->DC converter and ceramic heaters? My thought is to leave the controller side of the circuit alone and parallel off the accessories, switched by a spare EV200 contactor I've got.

Do I still need a precharge circuit in this instance? The DC->DC converter will be switched to the pack by the contactor, and the ceramic heater elements. For instance, what happens if the heaters are left on (inadvertantly or otherwise) when the vehicle is switched off and on?

 

[major]

Do I still need a precharge circuit in this instance?

I'd say no.

 

[Overlander23]

Thanks, major!

 

[Mike_Nickerson]

I found out the hard way that you certainly don't want a precharge resistor or similar circuit used with a DC-DC converter.

I noticed that I was getting a very small "tick" sound from the DC converter every 8-10 seconds. The pre-charge resistor from the main contactor was trying to keep the controller input at pack voltage. I had my DC converter wired to the same node. As soon as it reached 100V, the converter clicked on, drained the charge away and turned off.

I'm now using a second contactor to switch HV accessories and this one doesn't have a precharge resistor. This will have the DC-DC and the heater completely off when the ignition switch is off.

The heater shouldn't have any inrush current problems, but I have heard the DC-DC converter could. Because of that, I'm putting in an inrush current limiter. This is basically a power thermistor with an inverse thermal coefficient. (They have high resistance when cold, and low resistance when hot.) I'm putting one of these in series with the input for the DC converter, but not for the heater.

I'm just working on these wiring changes so can't report how well it works yet. I have heard that the thermistors can get very hot.

 

[SimonRafferty]

My DCDC converter is switched by the main vehicle contactor. It is designed to be plugged in to 240v mains without any pre-charge, so I figured it would be OK in the vehicle without pre-charge.

My heater is switched by a second vacuum contactor in series with the main vehicle contactor - and seems to work pretty well.

Si

 

[Overlander23]

I ended up switching my secondary HV accessories with an EV200. The DC-DC converter is an Iota 220v version which looks to have thermistors on the input. I'll most likely switch it out for a more weatherproof and rugged Chennic 500W converter, though.

 

[Guest]

Wire the heater so it will turn off when you shut down the vehicle. Be sure it's off by making sure a second switch is activated that will prevent power going to the heater. Redundancy is the key to safe operation. Micro switches can come in handy too. I have loads of them. Used to prevent power to the contactor coil used in the HV line you have for the heater. So when plugged in the micro switch is activated and prevents power if the other fails to turn off power. If the contactor you have fails on then you need your system to cut that power. Again micro switches come in handy.