Battery Backup Ran Out

I have a Greenfield ASV-100 (basically an Elk WSV2) controlled through my Elk. The valve gets power through an auxiliary power supply and it works great.

I recently evacuated for hurricane Matthew and left my alarm in vacation mode which shut the water off.

When I returned both the battery for my auxiliary power supply and my Elk were dead as the power was still out. But water was not impacted...except it was still turned off and I didn't deal like climbing under the house to move the valve. My wife was not thrilled about not having water.

Any suggestions? It would be great if the batteries quit with 10% left in then and I could fire the system up on demand to open the valve. I was thinking how boats often have two batteries. They are both charged but when the motor is turned off one battery is used for running the radio, etc. and the other is left unused just to start the motor in case you drain the first one.

Maybe a second battery in parallel with a diode and a switch? Or modifying the low battery shutoff to bypass it momentarily to turn the valve?or just ignore it? This really should only happen every 5-10 years and I can power my panel from my inventor in the car and rewire things like I did this time instead of going under the house.

Is a small generator out of the question? It would be handy to have around.
 
Mike.

I suppose a generator is a possibility. The auxiliary power supply is hard wired to AC and not plugged into an outlet.

I suppose I could add an outlet next to my aux power supply and use a cord. That would be easier than backfeeding my panel. But if I had a generator my fridge and tankless hot water heater could benefit from some juice.

So the small generator seems like the cheap part compared to backfeeding my panel safely and correctly.

What about a configuration where the WSV [power supply] is shut off in the event of an extended power outage (e.g. more than 20 minutes, or whatever you think is sufficient for standard outages). That way, the battery would be preserved until you manually re-enable (e.g. F-key override).

drvnbysound said:

What about a configuration where the WSV [power supply] is shut off in the event of an extended power outage (e.g. more than 20 minutes, or whatever you think is sufficient for standard outages). That way, the battery would be preserved until you manually re-enable (e.g. F-key override).

Click to expand...

 
The auxiliary power supply powers my cellular transmitter, WSV, strobe, etc.  So even if I cut the power to the WSV I can't guarantee there will be power left in the battery when I return.

You could connect two batteries in parallel to the charging circuit. If you use a diode to isolate the second battery so that it won't discharge, that will lower the voltage at the battery and prevent it from reaching full charge.  
 
Instead, connect the second battery through a relay whose coil is powered only when AC power is present.  When the AC goes out, it will disconnect the second battery and you can then switch it over manually if/when you need it.
 
When charging two batteries in parallel, it is best to use two batteries of the same type/capacity and age.  Preferably from the same manufacturing lot. Don't add a brand new battery in parallel with an old battery, as they won't charge evenly.
 
Another solution would be to connect the second battery to a good quality standalone charger.  When you need it, just swap batteries.
 
Or use one of those 12V car jump starter units that has a 12V utility outlet jack  Cost would be higher, but it would also be useful for jump starts if you ever need it.

If you have enough current, and the valve is home run, then you should be able to goose it open and then remove the power from the unit with the trigger active and it should stay.

Why not just keep a spare 12v fully charged battery available - similar to spare battery for cellphone. When you return back home, you would swap out the dead Elk battery with spare. The battery should have enough juice to control the valve.

Perhaps:
 
http://www.elkproducts.com/product-catalog/elk-965-low-battery-cutoff-and-master-power-switch

I like the jump-start pack with integrated inverter... that seems like a great option.  Even if you just connect the 12V jump start leads to the battery it'd recharge it too so the elk would be back in business for another day or so.  You do have to short a terminal to force the elk to power back on when there's no AC present; that could probably be hooked into a push-button.
 
I've also toyed with the idea in my next house of making the security system's power 100% grid independent by having a solar panel dedicated to the battery pack that runs the security so that it could have unlimited run-time.  Of course storms reduce sunlight, but don't totally eliminate it.  If using a separate charge controller instead of the M1's, you can go with a much larger battery pack to get 3-5 days of standby.

Thanks for all the ideas.
 
I like the jump starter idea.  My car battery is starting to get a bit older so it could definitely be multipurpose and pay for itself if I need to jump myself.  I could easily power my panel off that.
 
The auxiliary power supply is hard wired to 120V.  Therefore, I would probably add a switch or relay to accept my alternative energy source.  
 
I really like the solar idea.  In theory get unlimited runtime while also cutting down my electricity bill the tiniest amount.  And just something else to play with.  Anyone done this and have suggestions?

johngalt said:

I like the jump starter idea.  My car battery is starting to get a bit older so it could definitely be multipurpose and pay for itself if I need to jump myself.  I could easily power my panel off that.

Click to expand...

 
 
One thing to be careful of with the jump starter idea. You really don't want to use an automotive jump starter to re-charge the alarm system's 12V battery.
 
The jump starters are usually designed to deliver very high current in a short time.  That's ok for a car battery, but it is likely to damage a smaller battery like you have in an alarm system.  The alarm system battery needs to have the charging current limited to something around C/10 (e.g. 0.7 Amps for a 7 AmpHour battery).
 
The ideal device for running the alarm system temporarily would be a jump starter that also has a 12V utility output that can provide continuous power to the alarm system, in place of the regular battery.
 
Some examples:
 
https://www.amazon.com/dp/B01DABB9SM
 
https://www.amazon.com/dp/B017LIE842
 
https://www.amazon.com/dp/B01CA4GH5U