Relay/contactor question from a newbie

[JeepHammer]

Can a 240vAC(13A UK plug supply) circuit be switched using a continuous duty NO contactor with a 12vdc 0.8A 'control circuit' and rated at say 400A on the load side.
If not, why not exactly? If it is simply a switch and the DC control side is a seperate circuit from the AC load side, why do i keep hearing that it is a problem? Surely a switch rated to handle 400A dc would easily handle 13A ac for example. What is it about AC that would be an issue for the contact?

240vac coil, 40 Amps..., Use two if you want to double amperage.
https://www.automationdirect.com/ad...n-style,_40a_(ad-pr40_series)/ad-pr40-2c-240a

Relays draw about 3 amps, but if nighttime power is free...
relay fails on grid power
I would use a timer to run house and charge batteries at nigh,
Disconnect from grid in daytime and use battery power in the day.

Timer before Disconnect/Transfer switch.
Timer turns grid power on to the inverter so batteries can charge at nigh,
A second to transfer transfer the house (Load) between batteries and grid day/night.
230 volt timers are all over the surplus sites for cheap.

 

[astronom]

I don't like the power needed to drive the charge relay and the discharge relay all the time the system is on.... If you can figure out how to use the charge and discharge relay outputs to tell the Inverter-charger what to do, it might be better but that is highly dependent on the inverter-charger selected. I have the start of an idea on how to use latching relays to do this with a much lower power draw, but I need to think it through before I post it. If I can figure it out, this may be the BMS I use on an upcoming project.

I found out latching relays with driver circuit (or just driver circuit) that do just that in this post https://diysolarforum.com/threads/chargery-bms-now-with-low-temp-cutoff.3153/post-30137 if you're interested. I guess I'll go with that for my setup, at least for the discharge relay (for charge I will directly connect the signal to my inverter/charger)

 

[Solarfun4jim]

I just skimmed through the manual for the Chargery BST8 the OP is using. Nice BMS!!!

I like the relay-delay board accessory. That will do the trick for pre-charging the inverter prior to connecting the inverter to the battery. The precharge push-button or rotary switch discussed in the some other threads aren't needed. (The translated manual kept using discharge where is should say pre-charge so it took me a while to understand it)

I don't like the power needed to drive the charge relay and the discharge relay all the time the system is on.... If you can figure out how to use the charge and discharge relay outputs to tell the Inverter-charger what to do, it might be better but that is highly dependent on the inverter-charger selected. I have the start of an idea on how to use latching relays to do this with a much lower power draw, but I need to think it through before I post it. If I can figure it out, this may be the BMS I use on an upcoming project.

I may be missing something but I still don't see a need for a relay between the solar panels and the inverter/charger or between the AC-in and the inverter-charger.

Yeah, filterguy, i'm more coming round to your thinking on the subject....think i went down a rabbithole in my reading and created a problem that didnt exist. The only inrush current that does harm, is the battery connect inrush. Thanks for your input.