115v to 12v Relay In A Box?

S

Skyking

New Member
All,
 
This is my first post here and I am optimistic somebody may be able to help me with a commercial off the shelf solution (COTSS).  I was drawn here by a Google search result of "12V / 15A 120v relay, Anyone know where to get one?".  That thread was on this forum, but since it was posted in 2009 I figured I needed to start up a new one.
 
My application is a rural location with a marine deep cycle battery, charged with a solar panel and charge controller, used to operate a gate.  AC has recently become available and so I would like to have the system continue to be operated by the battery, but have the battery charged by an AC powered battery maintainer.  The relay would be for in the event the AC drops off line.  In that event I would like to connect the solar charger.
 
Anybody have a suggestion?
 
Much thanks,
 
Phillip Beall
 
Need some clarification:
 
The gate is operated by a DC motor that is getting power from the battery directly.  You have a solar panel and charge the battery via a charge controller.
 
You have AC available and would like to get rid of the solar? 
 
I don't see where you have the AC power the gate directly.
 
I think the best scenario is to just have the AC trickle charge the battery and just leave the battery operate the gate as you have.  If the AC goes out, the battery is no longer 'charging' but can still operate the gate.
 
OR, do you want the solar to provide the charge to the battery in case the AC is out for long periods and use a relay to alternate between charging with a trickle charge from the AC OR charge from the solar panel/charge controller when the AC fails?
 
You want to use the 120V AC Battery Maintainer to keep the battery charged and want the relay to switch to the solar charger if the AC to the battery maintainer is lost?
 
I'd have to think you'd be better served with a combiner or other circuit that toggled use of the solar and AC battery maintainer.  With all of the solar options out there isn't there something that already does this?
 
BLH said:
You want to use the 120V AC Battery Maintainer to keep the battery charged and want the relay to switch to the solar charger if the AC to the battery maintainer is lost?
Click to expand...
BLH,
 
You nailed it.  And BraveSirRobin, your last sentence nailed it.  I have contacted many solar providers and surprisingly to me none had a clue.  I even contacted a couple of companies that specialize in marine relays thinking this would have application at the dock - Plugged in to AC but if it drops off line the solar charger takes over.  Neither of them had anything suitable.  So, if anybody has a suggestion for a COTSS to my issue, as correctly described by BLH and BraveSirRobin's last sentence, I would greatly appreciate it.
 
Thanks,
 
Phillip
 
Ok, so if I understand correctly, you want a relay with an AC coil that can switch the battery from the normal DC charging source to the solar DC source.
 
You should be able to find a Functional Devices RIB relay that does what you need.
 
HERE is a way to do this (as RAL mentioned above).  A RIB 120 VAC coil relay toggles a set of contacts between NC (Normally Closed) and NO (Normally Open) to the C (Common) connection, which is connected to the battery.
 
When AC is present the relay toggles so a path is made between the NO and C contacts, thus charging the battery via the trickle charger.  When AC is lost, the relay reverts back to its default position by creating a path between the NC and C contacts, thus charging the battery via the solar/charge controller setup.
 
I DID NOT show fusing and other wiring details (conduits, junction boxes, etc...).  This is just a simple wiring diagram showing concept.
 
I do have to ask though the hassle factor worth in doing this.  Will the AC supply be that unreliable?  I mean, if you think about it, you are depending on 'just' the battery for the entire night (dark) periods with the setup you have now.
 
How often do you use the gate?  How much current does it draw?  How large of a battery do you have (in Amp-Hours)?
 
Given these factors you could calculate how many gate operations it would take to draw the battery down to half of its capability.
 
Again, this is very feasible to do but you may want to consider the above information before implementing.
 
Guys,
 
Thanks for the input.  I don't want anybody overthinking this.  The location is isolated and rural.  The power is dependable, but it is at the end of the utility line.  When the power does go out it is the last place restored.  Power has gone out for a week at a time on more than one occasion.  There is a good deal invested in the current configuration and with AC now available I would like to change to an AC powered battery maintainer as the primary charger for the battery.  With the current solar and solar charge controller already there it seems a waste to just put them on the shelf if all I have to do is buy a $30-50 relay, hence my question.  And I am sure I could figure out how to build one, but if there is something already out there that would do the job at a reasonable price, my preference would be to buy one off the shelf.  I have plenty to do to keep me busy, so if I can find a COTSS solution that is my prefereence.  I will go look at the Functional Devices website, but if this line of discussion causes anybody to have a great idea on a COTSS for me, one you can point me straight to, I would welcome it.
 
Thanks,
 
Phillip
 
All,
 
In follow up, the stuff on the Functional Devices site looks close to what I need, but they are all SPST.  I think I need a relay that is SPDT.  Am I right or wrong?
 
Thanks,
 
Phillip
 
Skyking said:
In follow up, the stuff on the Functional Devices site looks close to what I need, but they are all SPST.  I think I need a relay that is SPDT.  Am I right or wrong?
Click to expand...
 
There are SPST, SPDT and DPST RIB relay models.  Check out the RIB2421C.
 
BraveSirRobbin,
 
My sincere apology.  I had not until you reminded me to.  Yes, that is precisely what I need.  Much thanks for taking the time to draw that out and again, my apology for not having gone to look at it right away.  I have a note into Functional Devices asking them about a couple of their offerings.  The one I find there that is closest to what you drew out has an LED on it.  I do not want the LED so I will be curious to see what they reply with.  Much thanks to all of you and I will follow up once I get follow up from them.
 
Take care,
 
Phillip
 
I'd think you could just parallel the AC and solar chargers.  If the AC is not available, only the solar will run.  The marine guys do a lot of this, and a good marine battery charge would have no trouble with this.
 
Not having done this myself though, I did a quick search.  Here's someone who wanted to do exactly what you asked and the following discussion.
 
http://forums.sailboatowners.com/index.php?threads/using-solar-charge-controller-with-ac-battery-charger.151632/
 
If the chargers have adjustable charge voltages, making the solar unit a tenth or so lower than the solar unit will make the AC unit take most of the load, although since you have solar available, I'm not sure that's really a benefit.
 
Yes, good suggestion by Cobra above.  I know in marine applications there are switches that can diode sum between two batteries.  Possibly just sum both outputs (charge controller and trickle charger) to the battery.  I'll try to look more into this also.
 
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