PJ wiring

[phri]

I am still not sure what the best way is to solve the risk of the Powerjack blowing up when it switches to batteries.

Am I correct this risk is there if the unit is wired up as UPS: mains off, PJ switches on and rush-in current potentially courses damage?

I neeed the UPS funtion can I do this as followed?
Disconnect the  mains power -in permanent at the PJ unit, use a seperated charger for the batteries and use a relay which turns on the unit when the power turn off? (same relay bridges main when power is on via different contacts).

Or do I need delays which course a short blackout?

Please help as I am stuck on this one.

[Mary B]

Build an inrush protector using a relay that triggers after an RC timer is up to voltage. Current at first flows through a limiting resistor then the relay bypasses the resistor for full current flow.

This is for AC but it could be adapted to DC

[oztules]

A separate relay that ( DPDT ) senses the mains turning off can bring the power jack on line without problem or surge protection.... under any load I have tried. I have a transfer switch to go from mains to pj power, and as fast as I can switch it under any load conditions, it just runs with a slight flicker of the lights if I'm slow.
Probably even safer is to use two relays interconnected so one has to drop out for the other to turn on...should be fast enough still to cause no disruption to your gear.
It won't care if those loads are big induction loads or not, it won't care and will adjust it's voltage in a wave or two. No load you can dump on it instantly will remotely compare to the torroid surge start up current... thats the killer. The PJ can't change the freq to the tranny fast, or it is the same thing.

So if you charge independently, and the PJ is on, you can switch back and forth without a problem in my experience.

You will have the expense of keeping the relay alive while the mains are on is the only down side. Just make sure the relay is physically big enough for the contacts to break cleanly before make... and in my experience that should do it.

If you can integrate a small time differential them good, but as fast as I can pull the switch, there have been no problems in the last year or more....

My PJ runs all the time, so it is always available to switch to...... mostly it runs the place, but sometimes when I want to fiddle with the system, I switch it
 across... no issues.

If your running the pj in sleep mode, then there will be a delay anyway. It will start up under full load without fuss... I have hit it wih 8kw at a cold start, and it just does not care..... nor do the 002  boards I am playing with and the 8010's

.............oztules

[phri]

Thanks oxtules thats the solution I was hoping for.
At the moment the unit is wired up as a UPS with a large relay bypassing the PJ (sensing mains). I have done that to avoid constant load on the PJ relay, and because the PJ don't let power pass if it's off; thus endangering power supply to life supporting equipment (for fish) if things go wrong. This relay still has an set of unused NO contacts (30A) which I can use to power up the PJ. Is this all I need to do?

In addition,thus pj in sleepmode can be running in unmodified ups operation without problems? I am I right here Oztules?

I also wonder, will a high frequency / puls mode battery charger be more efficient then the build in pj charger? as charging through the pj charger seems to be inefficient.     

[oztules]

I can't say anything useful regards to PJ and the inbuilt ups in any mode.... I don't do it.
What can say is that the pj will stand all kinds of abuse if it is being switched in under loads ir anything else... it will likely stand a instantaneous short to mains too, as the transformers are unlikely to provide the current required to terrify the fets.

So set up your relays any way you please, but don't try to use the pj in it's native ups mode... it may work some of the time... but the back mmf will get it sooner or later (for me it is usually sooner).

Just use it as an inverter that will take terrible loads on cross over without a problem.

It is a good charger if you have good inductor, else you will loose 2-400 watts before you start.... but be very careful of it in charge mode too. turn off before mains removal.

In sleep mode it can still be directed to start from your change over relay, but there will be a small delay.. thats all. If you can handle restarts, then this would be the best route, as idle is economic, and your cross over timing is taken care of in a big way.

............oztules