I think I'll build this Battery Backup

[stugray]

I need to finally assemble a battery backup.

I have enough parts laying around & need to just finally do it.

I have a 100 Watt Inverter:

http://us.st12.yimg.com/us.st.yimg.com/I/navigatorenterprises_2028_41917919

I will buy a marine deepcycle battery & a maintenance charger.

I also have quite an assortment of relays, but the coils are all 28 Volt. So my design will require a 28V wall wart DC power supply.

If the relays were 12-14 Volt coils, I would have used the charger to hold them closed ;-)

Here's a diagram of what I want to do:

http://i366.photobucket.com/albums/oo101/stuartjgray/stus_batt_backup-1.jpg


So when the power is ON, the wall wart is putting out 28V and holding the relays in the NO position which connects the
battery to the charger & transfers both of the AC output lines wall AC lines.

When the power is OFF, the wall wart is not putting out 28V so the relays are in the NC position which puts the battery
on the inverter input & transfers both of the AC output lines to the inverter output.

Will it work?

Do I need a GFCI in the downstream AC plug, or do I risk it tripping everytime I transfer the power to/from the inverter?

Stu

[tarzan]

Are you sure it is ok for the battery to be hooked on charger 24/7? Most of big bateries require 10-24h to get fully charged and some tend to overheat and lose capacity if kept charged nonstop.

[customcolor]

wow that is simple when i look at it. but i think tarzan may be right about the battery. you may have to look into a battery manegment system too to save that deep cycle battery. one that will detect if the battery is low and charge it till its full power then shut off till its low again.

[stugray]

Sorry, my inverter is a 1000 Watt not a 100 Watt

Also - the "maintenance charger" is not the same as your everyday "car battery charger".

It will sense when the battery is fully charged & back off with the charge current to a "trickle charge".

Stu

[MJDiP]

Nice... a mini automatic transfer switch. I was thinking about how to make one of these as well. Good luck.

[MJDiP]

Oh, and I would really only be concerned about a GFCI tripping if it was upstream of the 120V relay, but you never know with those things.

[cyberwollf]

While thinking about making a DIY UPS. I read somewhere that while trickle charging, non sealed lead acid batteries Vent some bad vapors. Just a thought

[8BALL_99]

That should work. Mine is a little like that. Connections are a little different .I don't use a wallwort either. Mine just uses a Relay with a 110V coil. Works pretty much the same though. I wired the switch from my inverter to the relay also. So when the power cuts off it kicks the inverter on and switches the pump outlet to inverter power.. Power comes back on it switches back to grid power and the charger starts charging the battery again. I also have a switch on it for testing it. I did use a smart trickle charger, But now I have a couple of solar panels on the roof connected to a charger. I also use the battery in the ups to run my canopy lifts since they are 12v.
http://pic90.picturetrail.com/VOL2150/944495/5364694/269970959.jpg

[kcress]

Your plan looks good. I would power it all thru a GFI outlet. There is nothing inherent in the design to cause issues with that but you never know. It often comes down to the spike suppression front ends used in the various devices like your inverter and the wall warts. Just try it. I expect it to work.

Be nice to make the second outlet a GFI one too. Not sure what it will think about being fed by the inverter but otherwise you loose all your protection when running on inverter.

I would avoid a trickle charger like the plague. They are very bad for batteries cutting their life down by years. You want a multi-stage charger. (Note: Sometimes 'trickle charger is semantically misused.)

On the charger take a look at these. They are outstanding little chargers. I have shipped them with many products. Great bang for the buck. I use several on home projects.

As for battery gases. Overcharging or really high rate charging will give off a stoichiometric mixture of hydrogen and oxygen, the second most flammable gas mixture known. So do allow for ventilation and if you pick the right charger for the battery size you should not even have a problem. Keep in mind that flooded batteries can 'spritz' while charging, to a distance of about 6 inches in all directions.

8BALL's box and test buttons are nice touches.

[8BALL_99]

BTW I have a GFCI on the output of the UPS so it doesn't matter if the power is on or off the pumps are plugged into a GFCI. I've never had a issue with it tripping when the ups switches over.

[kcress]

Good to know. Thanks.

[tarzan]

So Stu, how is it going with the project?

Regards, T

[das75]

Heads up on the larger inverters is the DC input operating voltage. The 1000w unit I have shuts off when the battery discharges to ~11VDC (been a bit but believe was 11.2V)

Did the customer service thing and was told designed to be used when vehicle running.

As for you relays ensure you get 'break before make' type for when the utility comes back.

[khaosinc]

just an idea that might be easy and take even less juice...

places like harbor freight offer solar set ups to charge batteries and keep them charged. A simple relay can take care of the rest.

Second, if you are storing the batteries inside. Make SURE they are sealed. Regular batteries can leak hydrogen gas and it can build up, then blow up.

[Nammy]

bump

[oldsaltman]

Here is an old diagram of the one I did a few years ago. I added a very small battery charger 1-2 amp to the system.

http://reefcentral.com/gallery/data/500/115850Inverter.jpg

http://reefcentral.com/gallery/data/500/115850DSCN2948.JPG

It uses a relay to switch between 110v and 12v and I added two lights to tell me the status of the power.

[dgoth]

Interesting comment on the harmful battery vapors...

I heard about this also, and built a ventilation system into my battery backup system.

Since my battery backup system is in the stand right below the tank, right next to all my power and electronics, I can't imagine what would happen with even the smallest explosion!!

Anybody else heard about harmful or explosive vapors in a sealed lead-acid battery system?

[MperRluvR]

<a href=showthread.php?s=&postid=14002354#post14002354 target=_blank>Originally posted</a> by dgoth
Interesting comment on the harmful battery vapors...

I heard about this also, and built a ventilation system into my battery backup system.

Since my battery backup system is in the stand right below the tank, right next to all my power and electronics, I can't imagine what would happen with even the smallest explosion!!

Anybody else heard about harmful or explosive vapors in a sealed lead-acid battery system?

if your battery is sealed you'll be fine

[H20ENG]

Kcress, You forgot those links:)

Looks great Stu. Another point I would make is to make sure your relay can handle the amperage going through it (mainly the 12V side). Depending on what is connected to the inverter supplied outlet, the amperage could go way up at 12V, frying a little relay.

1000W inverter at 12v will fry most common relays at 83A! (I'm sure you wont be running anywhere near this, but just to illustrate my point).

Nice work guys:)

[Arghhh]

Sealed batteries won't really vent unless you abuse them with high voltage charging and high amperage. I would not put a wet cell battery in my house, especially next to relays and such that can spark unless they are ignition protected.

I use a little 2 amp vector charger/maintainer that shuts off when the battery gets full and turns on when it gets low.

Your setup looks pretty good, just like H20ENG said, make sure your relay can handle the amperage.