I have satellite Internet + VoIP and my remote place is run from a 12V solar system which is not complete yet as I am awaiting testing equipment to figure out exactly what is consuming what.

However, and it came as a bit of a shock, it is already obvious that the biggest consumer of electricity is the phone. When the phone is turned off, the consumption is slow but when it is on it is fast and almost visible on the panel meters.

This part of the system is made of a:
Ipstar dish
Ipstar transmitter/receiver (tx/rx) + power supply
Linksys Cisco voice gateway/router + power supply
pc + inverter or laptop + power supply

I found to economize on the power and reduce the number of plugging/unplugging I need to use 2 Ethernet cables (red and blue) and bypass the Cisco gateway/router, to do that I need to:
1) unplug the power supply of the Cisco
2) unplug the outlet of the tx/rx (blue cable)
3) unplug the Ethernet output of the Cisco (red cable -to pc) and plug it into the outlet of the tx/rx

to reverse the procedure:
1) unplug the cable (red cable) from the outlet of tx/rx and plug it into the Ethernet output of the Cisco
2) plug the input Internet cable (blue cable) of the Cisco into the outlet of the tx/rx
3) plug in the power supply of the Cisco

Is there a better way?

Before the installation of the system and without much thougth, I was assuming that the satellite would make contact with it when there is a call and current would only be used by the phone when the phone is in use, I realize now that was stupid thinking and that the phone (Cisco) is probing the satellite all the time, is my current thinking correct?

Thank you for your help.

If the computer is running a significant part of the time anyway, install 2 netcards in it and setup it as the router, instead of the router

Weight the power supplies you have. One that is heavy and does not have much output power for its size is a transformer, and is inefficient. Replace it with a switching power supply of the same rating

In the computer, use a higher efficiency power supply with PFC (preferred Active PFC). It may reduce the current from the battery a lot

If the negative side of the supply is connected to earth in your routers / dishes etc, you might want to run them directly on the battery instead of battery-->inverter-->power supply--> device. Make sure to what side of the supply the earth is connected (to avoid a short thru the earth wire or thru signal wires) and whether the device can stand up to 14.4 V instead of 12. Install a fuse of appropriate rating on the + side of the supply

Make an adapter with manual switch. In 1 position of the switch 2 cables are connected to 2 ports of router. In the second position they are connected to each other in crossover. You may use a relay but it'll use up power too so manual switch is better. You need a 8PDT (for 100mbit/s) or 16PDT (for >100mbit/s) switch here. Its ok to use 4 normal DPDT switches etc instead of the rare 8P / 16P switches (you'll have a network collision when they are not all in the same position, but no damage to equipment)

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If you have a multimeter that can measure 10A DC you can use it to evaluate stuff up to about 120 W (incl. inverter) or 90-100 W (excl.). Sometimes more - my cheap multimeter can actually measure up to 20 A on the 10 A mode (just quickly cause it heats up) which means up to 240 W (incl. inverter) or 180-200 W (excl.)

Set it to 10A DC. Disconnect one of the battery terminals and connect the multimeter in series with this wire. Power only the load you want to measure from the inverter

NOTE : if the multimeter reads higher current than its rating, or warms up, disconnect it quickly to prevent damage

The current you measured is directly the depletion rate of the battery

Now connect the battery back as normal. Set the multimeter to V DC and connect its wires to + and - of the battery. Power up the equipment you want to measure

Multiply the current you measured before with the voltage you measured now to get power

Note : the measurements include the consumption of the inverter (which also varies with load), so if you measure 2 devices separately and then together it often won't add up exactly, this is normal

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Hi,

I would look at the total DC requirements for the equipment in question. Why have the equipment dependent power supply if you have DC rails to provide source. Check the equipment source needs for each piece of hardware system.

Be careful about your grounding. If not done correct then 'smoke' or just plain hazardous to everyone/everything.

You should have a solar controller for the batteries that handles distribution & controls the batteries. If not then get one, be sure to look at the distribution control & source rails for the controller. Max loads that can be handled by the controller. Hanging independent power supplies or even inverters, you will be wasting a lot of power. If you just size the controller & the DC needs for each piece of equipment then things can be handled safely for each rail. Note the polarity for each piece for the DC input.

Commercial grade equipment & consumer grade are different animals. Most rack systems have power buss rails/controllers. With consumer grade equipment you will be providing the rails.

Why do conversion when not necessarily the proper way, especially at the cost of power? Yes, it's the easy way but now you are experiencing reasons for not doing it.

@Latios: Why not just use a shunt along with the ammeter? I would be careful about the technique you have outlined. Keep ground loops out! Protect & isolate the whole system. We are talking about a closed system here, so you can provide protection for the supply system overall. Isolate & provide a good protection scheme for the source(solar), controller & battery circuitry along with the equipment DC needs.

Chassis ground for equipment should not be a problem nor setting up equipment grounds properly.

Most battery rack assemblies are at ground potential for the system then protection circuitry for the equipment and personnel.

Your reasons for the above?

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For 120 V AC systems the Kill-a-Watt meter is popular; there are similar devices for ~230 V AC systems but I have found them of dubious accuracy below say 10 W; an ammeter as suggested would be more accurate but can be life-truncating.

Some inverters are picky about whether the AC neutral is earthed; this can cause hard-to-analyse problems if it is not as required.

If you live in a lightning prone area a strike on your solar system can be very expensive. Earthing is the answer but best practice is hotly debated.

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Hi,

Most 'Kill-a-Watt EZ meters range to 550W. Local power companies have been providing these kits to the public via schools & libraries. Useful for measuring small loads. Just Google 'Watt Solutions'.

Proper ammeter setups can do the the same in a knowledgeable users hands without potential damage to the system or Instrumentation. Loss & corrections for most watt meters are calibrated thus adjust active during measurements. If your bench happens to have a good watt meter then your ahead of the game. I prefer analog systems while measuring active loads.

Good lightening protection is doable both active & passive. Costs are the controlling factor. Look at 'Fundamentals of Lightning Protection - National Lightning Safety ..' a simple but fair presentation. For PV: 9.18 Lightning and surge protection for PV systems and solar power ...

You need to be sure that the potential is low for the PV system. Isolation can be done but then you need to protect everyone along with associative equipment.

I designed a PV powered Weather station system for a Local wildlife preserve, the PV mast was at ground with the panels isolated properly for equipment protection. Setting there for over 20 years just collecting & sending data. Hits?? Nothing apparent but have not been involved for a long time. This thing is sticking out on a hill that happens to be at a elevation that should get hits. Data Instrumentation Tower is 60 ft and just begging for a strike. I drove by a few years ago and everything is still functional. Batteries have been replaced.

Most people just do not bond the system very well and fail to strap things properly.

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Are there any solar / battery / PV experts / experienced folks here ?

I am planning on a DIY system myself, would be nice to know ya



Important stuff. There are 2 approaches, choose carefully :

The negative side of the DC is connected to earth. This requires that any equipment connected to it is either negative=earth too or the DC is isolated from earth. Prevents floating "unknown voltage to ground" condition in the DC system

The DC is floating. This requires that in all equipment (except 1 piece) the DC is isolated from earth. Reduces the chance for a short on the DC (you need 2 pieces that earth different sides of the supply to get a short, but if you get one it can be way more destructive). Has the added uncertainity whether you allready have that one connection to earth somewhere, ready to short as soon as another one appears

Didnt try myself, but i think splitting the system to segments with RCD's (GFCI's) between them (to cut any loops going thru the earth) makes sense in the 2nd approach

RCD's on the output of the inverters are good but dont make sense if the inverter output is isolated (in this case - again segments of minimal size and individual RCDs)



I dont know the value of the shunt inside my A meter

It worked for me to measure the current in a UPS battery when loaded with a computer

With a UPS it is a concern as the batery is connected to the output AC and not isolated, which means its at high voltage above earth (unless the entire computer is isolated from earth then it floats) - being carefull not to touch anything when its powered up. I dont expect this to be the case with a solar inverter



When need 3+ devices, power on the router and connect ethernet cables to it

When need 2 devices, power off the router and connect cables directly to each other in crossover



The panels are likely the most / one of the most expensive component here. I'd consider shielding them (with a lightning rod) above the panels in addition to everything else

And if there is a lightning discarge going through the batteries i guess its gonna be spectacular (with a lot of acid and acid vapor) so keep the batteries in a fireproof place and not inside the home

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Hi,

Actually the router/switches will auto sense. That's why I asked about your technique. If concerned then use solid state isolation switches, not mechanical.

Any mast mount for the PV system, be it on a roof flat or even a pole mast the potential would be above the PV to ground. PV isolation and the use of a passive crystal system or even thyristor protection would be the way to protect. Arrester units are available for different levels of protection for the PV inverters or controllers.

As to the shunt for any meter, calculate the required circuit with the internal resistance/current load of the meter then use that to create a shunt desired to measure the required range. The shunt calculated would be the multiplier/divider depending on design for the flow for the meter setting(s).

That's the design for a PV DC controller to control batteries along with sourcing the equipment. Do not confuse arresters and controllers. Look at the referenced links, you will find some useful information for methodologies.

I get paid for the information of this sort for designs. But you can get most of information from public domain via a good search.

As I said before, use care with design and implementation for grounding, bonding and general power rail designs. Be very careful! DC can kill you easier than AC when conditions are right. Remember that ventricular fibrillation takes about 10 mill-amps typical @ low voltages and once clamped your likely hood of death is certain. Of course this depends on the skin resistance of the person along with environmental conditions. Remember to use the 'one hand rule' whenever working or measuring.

Enough said!

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Electrical systems protection is a complex subject because the aim is to protect so many different things from so many different faults with constraints. That is why there are different systems in different countries, especially around neutral earthing.

The things to protect are people, fixed wiring and appliances.

The faults include shorts (all live/neutral/earth pairs although earth-to-neutral is not normally dangerous), disconnects (of live, neutral and earth paths, including more than one simultaneously), under-voltage and over-voltage of short and long duration -- and all combined!

Cost and convenience are the main constraints.

Over-current and "lost current" detection causing tripping is the main protection mechanism and works well for shorts, especially if finance is available for multiple distribution circuits, each with its own RCCD (domestically, whole house RCCDs provide protection but do not meet the convenience constraint). Under very high fault currents such as lightning strikes, RCCD may not open because the current welds their contacts before they can do so or they nay open but not far enough to extinguish the current which continues to arc across the open contacts.

"Floating" domestic wiring may result in neutral more than 100 V from earth (ground) with live cycling 60 or 120 V further. This sounds horrendous but is considered OK because the energy required to bring the wiring "back to earth" (!) is small so not dangerous. Hmm ... ?

Some opinion favours connecting neutral to earth via a resistor. The advantage of this scheme is that live to neutral short currents are limited (thus protecting the wiring) which are still high enough to operate the over-current protection. Other opinion favours connecting neutral to earth, arguing that this protects people better by ensuring that the (possibly exposed) neutral conductor voltage does not rise so far. In all cases the current capacity of the earthing system (and the possibility of it being disconnected) has to be considered.

So complex!

Solar system batteries are capable of producing enormous short currents which can too easily happen during maintenance when disconnected battery leads can come into accidental contact with something connected to the other battery bank terminal. For this reason an in-line fuse in one of the battery bank leads, close to the battery terminal is a wise precaution, as is an insulating cover over all terminals.

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Resistor like that + live to earth short = resistor on fire

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Hi,

@catkin

Here in the U.S.A we have codes to prevent the type of wiring condition you describe using a resistor in-line for neutral. NECA, NEMA & IEEE would not recommend this type of action. There are several protection schemes that could be used to protect equipment, people and systems in whole.

No way would I use a technique for neutral and system ground let alone earth ground. Most large installations will have several batteries in the system. I've worked with racks with over 50 per rack. System lockouts allow one to work on the system but you still need to be fully aware of the potential hazards.

In a system we have chassis ground, frame/system ground then earth. Isolation whenever performing maintenance is very important.

Design of the system as a whole is very important as to how you support protection for extraneous conditions; lighting, cell failure and circuit failures. Heck you even need to look at ambient static as a potential fault for control circuitry.

OP is looking at a light load system so the design for control and protection can be simplified. The power rails can easily be isolated therefore that will prevent potential problems for the user. It seems the PV, controller, battery and possibly inverters will be for the SAT, network peripherals & computer systems w/display.

KISS is important but you had better be sure things are right or you could be 6' under.

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I'd use power strips maybe. Also you laptop may run on the 12 - 15 VDC your system has. I have used all sorts of stuff on a automotive system. In fact that would be the best solution to get rid of the wall warts. The inverter has to go too.


Be careful to use correct polarity, I did burn up a laptop in about 3 seconds.

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It is the British system, enshrined in the Institute of Electrical Engineers' Wiring Regulations which all installers are required to follow. The neutral earthing resistors are part of the generating and distribution companies' equipment, not domestic. The ones on power stations are BIG. They seldom catch fire.

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Hi,

Whole different design criteria for power plants or trunk distribution. Not a proper technique for consumer(domestic) or even commercial power distribution in the states. Sub-station distribution is another picture.

Plus, we are talking about a DC system for PV control & distribution..

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I would not run a laptop (normally rated 18-19 V) on 12-15 V. There are switchmode voltage regulators inside (like theone that makes 5V). Undervolt them --> they'll try to keep the same output voltage --> same output current --> same power --> more input current --> overheat and die

So i guess not practical (or dangerous) for a small inverter system

I still dont see why a resistor is better than a dead short

We are talking about 2 systems here, and isolation between each vs earth and one vs other :

ELV DC panel + battery + inverter input + stuff running directly on battery

LV AC inverter output



OT : @OP and other solar system builders out there : Any good place online to shop for panels or cells ? (want max W / min $ & good lifetime in brutal sunlight, dont mind assembling panel myself)

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