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Small Cabin Forum / Off-Grid Living / My power system design: looking for feedback
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basrijn
Member
# Posted: 28 Oct 2013 20:12
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Hello,

I've been looking at a design for the electrical system in our cabin. Things I considered:
- Low noise since I want to use HF radio
- Must be able to add solar later (does not influence anything really it seems

Below images shows what I have come up with:


This is without solar. For now the Honda EU2000 plugs in to the bottom right corner. Wire is #12 armoured from outside plug to metal box with two outlet. One outlet has the battery charger plugged in.

From the outlet box another #12 armoured cable goes to the AC in (hardwired) on the Cotek St2000. The Cotek inverters are known as low noise (ARRL labs tested them). The Cotek has a built in transfers with (< 50ms transfer) and breaker.

Q1: Bring the 110V in without any breakers? Issue or not. Because the generator is capable of putting out infinite amounts of power (and has a 20A breaker) + the inverter and charger both have their own fuses/breakers I thought that would be low risk?

From the Cotek inverter another armoured cable runs into a normal load center with the circuits terminating there.

To me this is rather elegant Most of the time I run of batteries (our loads are very small at the moment). When the batteries drop below 80% I start the generator. That will start charging the batteries + the inverter goes in pass thru so I could use some larger loads (ie vacuum etc).

When solar comes I add some DC breakers and a charge controller. FlexMax extreme possibly, very low noise (and very expensive), but will allow re-use when we move to large solar setup)

Thoughts, suggestions, warnings?

Bas

Dillio187
Member
# Posted: 28 Oct 2013 20:36
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I think you need more battery, that 2000w inverter could flatten those batteries pretty fast, plus it has a fair amount of standby power use too I bet.

Regarding breakers or not...it doesn't really matter, you're not going to trip one of them before the breaker trips on the inverter anyways. I installed them in my cabin just for ease of troubleshooting certain circuits. I grounded my system as well, but not all inverters can be grounded or they let out the magic smoke.

basrijn
Member
# Posted: 28 Oct 2013 20:49
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Dillio187: The batteries are there to give is some peace and quiet at night With satellite internet and light on, we only pull around 60W. Inverter pulls 2.6A or 0.6A in stand by.

Whole system will be off if we are not there (making sure batts are at 100% before we leave).

Reason for the 2k inverter is so we can run the occasional big load if we want

Dillio187
Member
# Posted: 28 Oct 2013 21:01
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makes sense, and sounds like you understand the limitations (running the genny for the big loads)

MtnDon
Member
# Posted: 28 Oct 2013 21:31
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I'm not familiar with the Cotek brand. Is the charger a 4 stage... capable of equalizing? Potential issue with the charger being powered by the Honda... Could the DC voltage output of the charger go higher than the DC voltage maximum input of the inverter? This is one reason I prefer a combination Inverter/charger over separate items. I fried an inverter once years ago because of this.

If the future might involve a Flexmax CC (excellent) using an Outback FX or VFX would allow use of their mate and tying everything together for control and data purposes; battery temperature monitoring. The remote batt temp sensor can be valuable for getting best battery life.


This may be simply a personal quirk of mine, but the duplex receptacle pictured above the generator input bothers me. It looks like an ordinary receptacle but it is not meant to be. It is a "special" system connection. I just do not like things like that, things that can be easily misinterpreted by someone else. You know what it is, but others may not. You may not always be the person there doing the operating. Just a thought.



Also be careful with the service panel connections. The usual and code thing to do is to have a bond between neutral and ground in the AC service panel. But there should only be one bond in a system. Again, I do not know the Cotek inverter... is it bonded internally or not? Ditto what about the Honda when it is running; bonded internally or not? I forget.

Dillio187
Member
# Posted: 28 Oct 2013 22:00
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Don, I think Cotek inverters are made by Samlex.

basrijn
Member
# Posted: 28 Oct 2013 22:39
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@MtnDon: As Dillio187 mentioned in his response. Samlex sells part of their line in North America. Cotek is actually the OEM, not Samlex.

It is a smart charger: http://www.cotek.com.tw/product/71.html But I don't think it does an equalize, but with my 2 batts in series, that won't be needed correct?

Vout MAX for charger is 14.8V
Vin MAX for inverter is 15.3V

Inverter also has protection for: input polarity reverse, under voltage, over voltage, output short circuit, overload and temperature

The charger has a temp sensor to adjust charging for batt temps.

Flexmax extreme can only be programmed with the Mate3 since it's fully sealed and has no user input at all. I also like the Mate3 option for it's data logging options. It would give me some really good data on solar input.

The receptable would behave as a fairly normal one. It's either powered (if generator runs) or it's dead (if not running). I was thinking of spray painting the cover orange (I'm Dutch after all) and labeling it as "Generator powered"

The special requirement is that the battery charger should NEVER be plugged into another outlet since that would nicely draw down the batteries

Any suggestions on how it could be done differently?

I've read up on the bonding requirements. I have to check the Cotek to see how it's wired internally. It's designed for cars/boats, so probably a floating ground. Same for the generator.

TX!!
Bas

MtnDon
Member
# Posted: 28 Oct 2013 22:56
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Quoting: basrijn
don't think it does an equalize, but with my 2 batts in series, that won't be needed correct?


The number of batteries doesn't determine whether or not you need to equalize, although the more batteries in parallel the more likely it is necessary. The need to equalize is solely dependent on the sp gr of the cells; when one or more is off by more than 0.015 when fully charged then it is needed. Although I know that there are many other factors that affect battery life. In an ideal world I would want equalizing ability; but things are not always ideal. And the less we equalize the easier it is on the plates; meaning I do not subscribe to the idea of every month. Just when the sp gr indicates.

~~~~

If the system is to be left unattended for several months at a time a small PV panel that can perform a float anytime there is sunshine can help preserve batteries. We leave our system run itself for months at a time when we are away. Peace of mind.

basrijn
Member
# Posted: 28 Oct 2013 23:01
Reply 


@MtnDon: My HAM 25A PSU can go up to the 15.5V volts that Trojan suggests as equalizing voltage. So I can run an equalize "offline" when needed.

Bas

MtnDon
Member
# Posted: 28 Oct 2013 23:34
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Dillio187
Member
# Posted: 29 Oct 2013 10:26
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ah OK I had it backwards, Cotek makes Samlex. Thanks for the reminder, time to equalize the 24V bank at home and the 12V bank at the cabin!

missouriboy
Member
# Posted: 29 Oct 2013 21:19
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I wish I understood Greek!

basrijn
Member
# Posted: 28 Dec 2013 23:20
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Hi,

Finished most of the install and working pretty well. Other then that the generator to battery transfer is a bit long, causing computer / satellite modem to reboot it works very, very well.

Picture of the install:


Inverter falls asleep at night (if you don't forget to unplug laptops and cellphones

It was kindy funny to see how the inverter sends power pulses to see if there is any loads connected. The LED christmas tree lights pulled a load lower then the threshold, so they were blinking nicely

The battery is temporary and will be upgraded to two Trojans once funds allow.

Solar hopefully to follow this summer.

Bas

old243
Member
# Posted: 29 Dec 2013 10:20
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Bas, if you don't mind me asking . What would the ballpark costs be of the different components, that you used. Old243

basrijn
Member
# Posted: 29 Dec 2013 21:58
Reply 


@old243: Not at all.

Prices below are what I paid at RP Electronics in Vancouver, BC. Prices online and/or in the US will probably be a bit better. I was happy to pay a little extra for the service and convenience I get from buying from a local store

Cotek ST1000-112 (CAD 599)
Cotek CR-6 remote control (CAD 67)
Cotek temp sensor for battery charger (CAD 18)
Cotek CX1225 (CAD 237)

They also have a 1500W inverter (CAD 728) and a 2000W (CAD 937)

The CX smart chargers are also available in other AMP ratings:

CX1215 $208
CX1225 $237
CX1235 $285
CX1250 $407

Hope this helps

Bas

vacabin
Member
# Posted: 16 Jan 2014 08:03
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basrijn when the generator is running does it deliver power thru the inverter to the load center as well as to the battery charger.

basrijn
Member
# Posted: 16 Jan 2014 09:54
Reply 


@vacabin

That is correct, there is a 30A build-in transfer switch. It's one of the main reasons I picked this setup. They also sell a smaller inverter, but it's only a 10A transfer switch.

Bas

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