Low voltage disconnect

[eamarquardt]

Although the solid state relays seem to intended for AC current AC (at a single instant in time) is actually DC so I don't see why an AC relay (with the proper control voltage) wouldn't switch DC. Especially if the relay were "oversized". However, there are different things going on when switching AC and DC. Perhaps someone might know for sure if it would work.

AC and DC are very different beasts. First off if the solid state relay is zero voltage cross style, it will only turn on and off when the voltage is at zero. DC power won't ever have that happen unless the battery is dead. Random turn on and off AC solid state relays may or may not work to control DC loads. Note, the relay will likely be rated for both AC and DC if it can handle both.

Yup they are and that's why I qualified my answer. I seem to learn something every day!!!

Hey Gus,

You probably noticed that there's a Sunsaver 10 with LV disconnect sitting right next to the Intellitec module. So why didn't I use that to control the relay? The intellitec relay is mechanically held and draws zero current except when it being switched on or off. That means you need a 12V pulse to turn it on and a 12V pulse to turn it off, which the Battery Guard monitor module supplies. The Sunsaver only has 12V continuously on or off so it can't control the relay. The Battery Guard monitoring module only draws a couple of milliamps of current, which is why I went with this system as it has the lowest continuous current draw that I could find.

Bruce

Makes sense to me. Learned TWO things today.

Bruce, my recent trip to Denver/Golden was 50% fun and 50% painful ordeal. Next time!

Cheers,

Gus

[eamarquardt]

My curiosity got the better of me so I searched on EBay for DC solid state relay and found this:

http://www.ebay.com/itm/Solid-State-Rel ... 27ce1b90f9

The upside is that it is cheaper and allows your solar controller to control it. The downside is that it will use up to about 1/2 amp/hour a day to run it and it is only 25 amps versus 30amps for the disconnect Bruce used.

Here is one that would handle 60 amps. The same pros and cons.

http://www.ebay.com/itm/Solid-State-Rel ... 5adfb18e6c

Lots of different ways to "skin the cat". Having the disconnect voltage adjustable is kinda cool.

Ebay, your source for just about everything.

Cheers,

Gus

[eamarquardt]

Re the special connector on the Intellitec disconnect control module.

My curiosity continued to get the better of me and I found this kit that seems to include the wiring harness required (but the picture isn't clear on this). It's only about two times the EBay price of the controller and latching relay!

http://www.ltdrvparts.com/INTELLITEC-BA ... 317000.htm

Note that it has: Disconnect Bypass - A terminal on the Controller provides constant battery power to the radio or phone memory, or as a solar panel connection.

Rather than soldering to the pins of the controller one might be able to used standard Molex pins, insulate them with heat shrink, and fabricate a small bracket with a cable clamp to keep them from coming loose.

A while back I bought a cool Delphi connector kit made by these guys: Delphikits Co. Phone 541-330-8800. Perhaps they might have the connector for the control module.

Also one might try these guys: http://terminalsupplyco.com/Store/

Finally, one might contact Intellitec: 131 EISENHOWER LANE NORTH, LOMBARD, ILLINOIS 60148 630-268-0010 / 1-800-251-2408

Just my OC brain working overtime.

Cheers,

Gus

[Dale M.]

ON the stereo thing.... Just wire the "keep in memory" wire to the battery side of disconnect.... The current/voltage requirement is so small it probably would not run battery down in a year of not being charged...

Dale

[bdosborn]

ON the stereo thing.... Just wire the "keep in memory" wire to the battery side of disconnect.... The current/voltage requirement is so small it probably would not run battery down in a year of not being charged...

Dale

The Battery Guard has a 5 amp, always hot terminal for just that purpose. Unfortunately, I built a cabinet around the stereo so it would be a PITA to route a wire back where it needs to go. Maybe someday when I've got nothing to do I'll tackle that job.

Bruce

[bdosborn]

The downside is that it will use up to about 1/2 amp/hour a day to run it and it is only 25 amps versus 30amps for the disconnect Bruce used.

The Battery Guard relay I used is 100A and they have an optional 200A. I could have run my inverter through the relay but it would have meant reworking some big (expensive) cables. I opted to run everything but the inverter through the relay since it has it's own integral LV disconnect. I pull over 30 amps occasionally due to the Espar diesel furnace, it will pull 22 amps for about a minute when it's starting up. I pull 10 amps with the TV, fan and refrigerator running so even a 30 amp relay was sketchy for me.

Bruce

[eamarquardt]

Given that I have a Morningstar MPPT controller with low voltage disconnect (limited to ten amps as I remember) I just ordered a couple of these to up the capacity:

http://www.ebay.com/itm/390300012140?ss ... 1439.l2649

The specs call for 5-25 ma control current draw. When they arrive I'll measure the current and see what they actually draw at 12 volts. Even worst case 1/2 amp/hour/day isn't gonna break the bank (of battery(ies))

I don't think I'll ever draw more than twenty amps and that would be for only short periods (pump running) but the control current for the 25 amp relay and 60 amp relay are nearly the same so why not use the 60 amp and have a cushion. Overkill in moderation. No 200 amp latching relay required, ha.

Bruce, if you provice me me the pin spacing and the pin dimensions (would require a small caliper to measure), I may have connectors "in stock" that will fit your controller.

Fun kicking stuff around.

Cheers,

Gus

[bdosborn]

Gus,

That looks like an easy approach to providing a LV disconnect, it makes me wish I'd looked at it closer before I pulled the trigger on the Battery Guard. The current draw is about the same as the Morningstar MPPT controller so yeah, it wouldn't be a meaningful load for the battery.

I've got a caliper around here somewhere, I'll see if I can measure the pins.

Bruce

[eamarquardt]

I got a couple of these in the mail a couple of days ago. Very fast delivery from China. I don't see how they do it.

http://www.ebay.com/itm/390300012140?ss ... 1439.l2649

They draw 18ma at 12 volts (nominal).

I was able to switch off a 3/4 hp 90 volt motor (although I only had it connected to 12 volts) just fine.

Cheers,

Gus

[bdosborn]

I pulled the trigger on one too, just to mess around with it...

Bruce

[eamarquardt]

I pulled the trigger on one too, just to mess around with it...

Bruce

Just messing about with stuff is good. I bought 5 of these, delivered, for less than $13.

http://www.ebay.com/itm/Mini-red-LED-Di ... 5655748400

I can't drive to Electronic City (the last local electronics store that I'm aware of) in the San Fernando Valley for that much.

I just finished milling out a housing so I can mount one on my motorcycle. I don't see how the average homeowner gets by w/o a milling machine. The bike keeps draining the battery so I want to see if the bike is still charging after running for a while. Also as the bike has no key/ignition switch (kill switch only) and I often forget to turn off the battery when I stop so the voltage display will remind me that the battery is still turned on.



Cheers,

Gus