Thursday, April 20, 2023

Battery Monitoring System

One of the first tasks I assigned myself on purchasing the yacht was to install a battery monitoring system. After some research I opted for the Victron BMV-712 Smart monitor. This model has Bluetooth built in which is a huge benefit considering that you can access the monitored data from the comfort of the mobile.

I have installed the 500amp shunt just next to the batteries, keeping the wires as short as possible. I have used 70mm wire (as what has been initially installed by the manufacturer).

The Smart monitor display has been installed on the chart table. I located an empty surface and installed some other stuff as well (as seen below). 
    - DC Battery monitoring system
    - AC Monitoring system
    - USB Ports
    - AC Power Ports

The datasheet for the Smart monitor can be downloaded from here

I'm also attaching a Current Cable Rating chart which I found online for reference.

Inverter Installation

There are a lot of inverters out there however hands down I bought the Outback Inverter (Marine - sealed, Export version 12v DC to 230v AC). I can vouch for these inverters! I already have an off-grid 24v inverter installed at home and it delivers what it promises. Weighting a whopping 30kg, one can easily acknowledge how robust these inverters are built.

I found this photo on the web. It can be clearly seen why the inverter is so heavy. Bottom right there seems to be a huge transformer.

Some Basic stats;
    Pure Sinewave
    DC 12v Input 
    AC 230v Output
    Continuous power 2000VA which can surge to 4600VA for 100ms.

The inverter has been connected using 70mm marine grade cable which is good enough to handle the DC current with minimal voltage drop. Please refer to the wire chart at the bottom of this post.
The inverter has been protected by a 120amp circuit breaker. I'm limiting the current which the inverter can draw to 120amp or 10amp AC on the high side which is more then enough for my needs. The inverter can also be switched off when not needed (to eliminate the standby current drain on the batteries). The battery switch has been overrated and in fact can handle 275amp. This will ensure a longer switch life since it will not be operating at to it's maximum ratings.

The Inverter switch (left) has been fitted next to another 3 main switches which I fitted myself. The middle switch is used to connected another set of deep cycle batteries situated at the stern of the boat. I covered these batteries in a separate post. The right switch is used to disconnect the solar panels.

The Inverter circuit breaker has been fitted under the main saloon seat just next to the inverter.

Below are the pictures showing the inverter installation and location. It has been fitted to the boat although considering it's weight it won't move easily.
The location is underneath the starboard saloon seats.


The load which I'll be powering with these inverter are;
  • 900W Toaster
  • 1200W Electric Kettle
  • 240v AC points
  • Small (10litre) air compressor
  • 240v Water pump (used to flush the black water tanks & Deck wash)
Obviously I won't be powering all these loads at once.

Below is a Cable Rating chart which I use to select my DC wire sizes.

Some related documents.

Water Expansion Tanks

Why install an expansion tank?

Well the answer depends if it's installed on either the cold or water circuit.

  • Cold circuit.

On the cold circuit, an expansion tank is not really indispensable however I installed it because it will reduce the number of times the water pressure pump switches on. The pump will not switch on every time the water tap is opened. Once it's on, it will fill up the expansion tank (depending on the size of the installed expansion tank) and any subsequent water usage is supplied from the tank until the pressure falls enough that the pump will need to switch on. 

The installation of this expansion tank is a huge benefit especially at night because the pump will not switch on as soon as the water tap is opened. The pump although enclosed is not very silent and at night it just wakes everyone up when it switches on!

  • Hot circuit
In this case, personally I think that an expansion tank is indispensable. The expansion tank is designed to handle the thermal expansion of water as it heats up in the water heater, preventing excessive water pressure. If water pressure gets to high it can damage valves in plumbing fixtures, joints in supply pipes and the water heater itself.

I installed both expansion tanks at the bow of the boat (the location of the tanks is irrelevant) specifically in the master forward cabin, next to the bow thruster.
As seen below, the small hot water expansion tank is connected through a red pipe, through a Tee in the how water circuit.  

The cold water expansion tank is also installed at the bow in the bow thruster compartment. 

The expansion tank is the left most white tank. it's connected using a blue pipe through a Tee in the cold water system. On the right you can notice the RO system.

Fridge Extra Cooling

One way to increase a fridge efficiency i.e. consume less power while maintaining a low temperature is to keep the compressor and the condenser coils as cool as possible and this can be achieved by facilitating heat dissipation. 
As detailed below, the Condenser Coils need to dissipate heat efficiently to enable the refrigeration process to function efficiently.
This is normally achieved using natural air ventilation and one way of doing this is by leaving enough space for the compressor and condenser coils to breath and release heat naturally.
In fact, house appliances, the manufacturer recommends the clearance which should be kept between the appliance and the surroundings enclosure.

Having a look at the location of the fridge and subsequent compressor / condenser coils, there is not much space for natural air cooling simply because the assigned space has very little way of ventilating since the cabinet volume is very slow.

To overcome this, I installed a 12mm silent fan (as seen below). The fan will extract the heat from the compressor and condenser (installation unit) and push it out to the next cabinet on the right i.e. another small cabinet under the oven. 
The overall volume has now increased however this will not really help much since the extended cabinet is also sealed with little ventilation.

To fix this also, I drilled a 12mm hole on the upper section of the adjacent cabinet i.e. just underneath the oven.
Since warm air flows up, this will ensure that the heat will escape from this hole, thanks to the external fan which is pushing it out.

The system operation is very simple. I took the supply directly from the compressor connections, i.e. the external fan will switch off when the compressor is off. 
I also installed a 45 degrees thermal switch on the compressor and therefore the external fan will only come on once the compressor is busy working and has reached 45 degrees +
The extra fan does add more noise to the fridge operation however it will switch on only when the compressor is on and hot.

The connections have been installed in a waterproof box just next to the compressor.

A further improvement which I'll be making soon is to drill a hole at the bottom of the air compressor cabinet thus 'cooler' air will be sucked up from the bilges.

ps. Always make sure that the condenser coils are free any dust since this may/will act to to reduce heat dissipation, lowering the overall system efficiency.


Thursday, February 13, 2020

Grant on renewable batteries

The below is an extract from the Maltese 2019 budget speech (valid for 2020).

Basically for the year 2020, the government will start giving a grant (25% of the cost up to a maximum of  €1000) for anyone interested in buying batteries to store energy generated from the solar array. 
The intention behind this scheme is that the energy generated from the solar array will be stored in the batteries instead of being sold to our country energy provider (Enemalta) and then self-consumed at a later time by the client himself, thus eliminating Enemalta from the equation.

I really don't know if I should laugh or cry at such an initiative!

All this comedy started simply because Enemalta (after the initial contract expired) is paying a very low rate per KW for the energy sold. If I'm not mistaken this is a mediocre €0.07 per KW while the same energy is bought ranging from €0.12, €0.16 to €0.34 per KW depending on the consumption band. It seems that NOT all energy is equal for Enemalta and it's a good way for them to also make some profit on the energy generated by the households which is sold at a higher tariff.

This will eventually get even worse for more people who have installed solar panels simply because the initial contracts for selling RE units to Enemalta are expiring. During the contract, the selling rate was €0.21 or €0.25 for Gozo (energy generated from the solar panels and sold to Enemalta), the intention being to make it higher than it's bought from Enemalta making it more attractive for people to invest in solar power generation due to the higher selling rate per KW and thus a better return on investment.

However the intention of all this is now clear! Enemalta will encourage clients to install panels and make some money for the first years (actually the first years are used to pay back the initial investment), THEN, it will pay you back a miserable rate, enough so the company can make money. Here we're talking of a minimum of €0.05 per KW profit.

Putting in batteries in an already working battery-less grid-tie system is not straightforward! 
1) Most probably, the most expensive component in the RE system will need to be changed, i.e. the grid-tie inverter. Here we're talking of €2-3K. A hybrid inverter such as the SMA Sunny Island inverter will need to be purchased, one that charges batteries and sells the excess energy (once the batteries are full) to Enemalta.
2) The batteries are expensive! The most practical options are either Lead Acid (least expensive - short lifespan) or Lithium-Ion (much more expensive - longer lifespan). For a 6.5KW 48v lithium-ion battery will cost around €3.5K. The goverement will subsidy this amount and for an investment of €3.5K will reimburse €750 or 25% of the battery cost.
3) Changes to the system, i.e wiring and any miscellaneous hardware needed such as wiring and switching gear.

All these changes will easily amount to €6K and the government is giving a mere €1K maximum on just the batteries! 

In my opinion this does NOT make sense and I'm afraid this scheme has just been created to allow a number of local RE providers to make money, by contracting them to purchase the batteries, additional hardware and make the necessary changes to the already installed systems. 

All this hassle and system changes just because Enemalta is paying its clients a lower rate per KW then it's bought. 
Would it have made more sense if the government ensured that both the buying and selling rates are the same? Is this such a difficult concept to grab? It seems YES, when the main objective of all this is for Enemalta to make more profit.

Wednesday, February 12, 2020

EV Licence

I have to mention this since instead of progression we're experiencing regression at Transport Malta!

The government 2-3 years ago waived the €10 licence fee for electric cars and in fact it's now free which is a good thing.
However I would have preferred to still be paying the €10 licence fee simply because now the licence can't be settled online.
It seems that instead of putting more services online, Transport Malta have opted for us, electric car owners to pay them a yearly visit at their office just to settle the license fee.

Why can't it be done online anymore? Why do I have to go personally to their office? Is it worth to save €10, you need to go personally to their office? Is this the way forward?

Thursday, July 18, 2019

Solar Inverter Diversion

Lately I have upgraded by 12v battery system by adding an extra 150W solar panel to the existing setup, totaling my 12v system to 320W (STC). I just have a small limited number of circuits/load on this system and was wasting a lot of power through the Xantrex charge controller configured as a diversion load. On a sunny day, the charge controller was diverting power to a power resistor before noon, wasting power as heat for the whole afternoon.
To make better use of this power, I installed a 12v 1000W grid-tie inverter. The idea is to divert the excess power to this inverter once the batteries are full and use only the charge controller as a fail backup if there is no grid power.

Circuit Diagram
The circuit is fairly simple and I tried to keep it that way! I always follow the KISS principle (Keep it Simple Stupid).

The circuit below is used to switch on/connect the inverter to the panels/batteries once a threshold voltage is reached and then disconnect the inverter after a pre-determined amount of time. I did NOT use a low voltage disconnect and opted for a timely disconnect simply because this will cause the inverter to connect/disconnect too frequently.

Basically, a reference voltage is compared to the 12v battery voltage using a comparator. This will bias a transistor, switching on a relay, connecting the inverter to the grid.

Supply for the circuit is taken from a 24v supply rail (another set of batteries & panels in my case) and this is stepped down to 15v using the 7815 linear voltage regulator. This 15v will power the whole circuit. Capacitor C2 is used as a charge reservoir to maintain a steady 24v supply to the 7815 voltage regulator. Diode D7 (Green) signals that there is a supply voltage on the circuit board.
I have used another voltage regulator 7810 to get a 10v supply. This voltage is divided by resistors R1 & R4 which will give me a 5v signal voltage. This voltage is made steady thanks to another reservoir capacitor C3. Capacitor C6 is used as a charge reservoir to maintain a steady 24v supply to the 7810 voltage regulator
The 12 volt detection is carried through Diode D4, split by potentiometer R2 and smoothed by capacitor C4. Any quick variations in the 12v system are simply filtered out through R2 and C4, thus providing a pretty steady signal to the opamp. This will eliminate any 'quick' variations to the supply rail such as switching on heavy loads or panels cloud effect or even the switching on itself of the grid- tie inverter.
The opamp is an LM324, and I'm using just one opamp out of the four available. The opamp is configured as a differential comparator.

The opamp feeds the base of a bipolar transistor Q1 - TIP122 which in turns powers the relay. Diode D2 protects the transistor from any back emf generated by the relay coil.

Diodes D3 and D8 safeguard the circuit from accidental reverse polarity.

The non-inverting input of the opamp is held at about 5v thanks to the R1/R4 voltage divider. The inverting input is connected to the 12v signal detection. As the battery voltage rises, it slowly starts charging capacitor C4, a 10000uF capacitor. Once the inverting input exceeds the non-inverting input, the opamp output switches on. Orange LED D6 is on. Capacitor C5 starts charging through diode D5 and this will provide a base current to transistor Q1, switching on the relay and connecting the grid-inverter to the grid.

Once the inverter is on, the batteries will start draining heavily and thus the signal voltage will lower down, The non-inverting input will become more then the inverting input and therefore the opamp output switches to low. This will not happen suddenly thanks to the R2/C4 configuration, thus providing some hysteresis. Also, once the opamp output switches to low, transistor Q1 will remain on for some time thanks to the  D5/C5/R5 configuration, providing approximately 5mins of ON time.

The above is a photo of the finished circuit.

Wednesday, July 17, 2019

Product Review - 1000W Grid Tie Inverter

I bought this inverter from ebay from a Chinese supplier for just 120€ including shipping to Malta. Quite cheap considering the output of this inverter.

The inverter is rated at 1000W at 230v output. 
From the outside, the inverter is well built. The input terminals are fused, sturdy and thick enough to handle 10mm cables. The fan comes on occasionally just when the inverter body becomes warm, thus giving plenty of time for the inverter to start the cooling process.  


The big question is how will it perform?

Well, I have been using it for 1 month and the maximum current which is has drawn from the solar panels/batteries is 20amp, therefore outputting about 250W into the grid. The inverter just gets slightly warm. 

Once I'll have more input power, I'll be able to fully judge the inverter performance. Right now the inverter is operating in a 'relaxed' mode.

Thursday, May 16, 2019

12v / 24v Battery Charger

This is a simple circuit of a 12v/24v battery charger. I had originally a 12v battery charger however the transformer burnt. Instead of throwing everything away, I salvaged the charger box and built a new charger, capable of charging also a 24v battery.

I used two identical transformers, 240v Primary (although in actual fact they are a number of tappings on the primary to better control the output voltage). These came from old cheap UPS systems. I used a tapping of one of the transformers (T2) to control the HIGH/LOW voltage.

The charger has got an output voltage selector switch (SW2) together with a HIGH/LOW selector switch (SW1). The relay is used to add the 2nd Transformer output  (T1) in series with the 1st Transformer (T2). Both bridge rectifiers are the block type, 25amp current output. Resistors R1 and R2 have been included across the transformers output to dump any stray voltage. I could measure 50v on the digital multi-meter when in actual fact the output would have been 30v!

Internal close up of the charger wiring.

Transformers used. As mentioned these came from 'old' UPSs

I added a heat-sink at the back of the charger to better help in dissipating the heat generated by the rectifiers

Close up picture showing the rectifiers...

I also changed the charger cables to a pair of sturdy 10mm cables together with larger crocodile clips 

The original charger box... 

Friday, January 18, 2019

Outback 24V 3Kw Inverter VFX3024e

I finally purchased and installed a proper off-grid inverter capable of handling my ever increasing home energy needs.
I settled for the Outback 3KW Inverter (VFX3024e), the European version outputting 220v at 50Hz.

The inverter has been installed and performing flawlessly for a number of months now. I have never exceeded it's rated output, in fact I doubt I ever exceeded 1KW of load.
The cooling fan output varies with the load demand and the current temperature of the inverter internals and therefore operation is quite. One thing I have to point out however, which is the humming coming out from the device. I installed the inverter in the garage and therefore noise is not an issue however the humming can be annoying if the inverter is installed close to the living area.

Friday, August 25, 2017

24v System Upgrade

Part of my home system overhaul, I also upgraded the 24v panel. 10 years ago when I first built the control panel, my system requirements were much less. 

The photo below is displaying my old control panel. I have 4 amp meters together with their respective fuse holders and switches.
The fuse holders were rated for 5 amp and the switches for 10 amp DC, however during the years, I had issues with both since I had to replace multiple switches and fuse holders because they melted

The photo below is displaying the new control panel. I removed the switches because in 10 years I don't think that I ever needed to switch off a PV string. Also, I removed the panel mount fuse holders, and instead I opted for a heavier duty rail mount fuse holders which have been installed inside the control box. I also replaced all analogue amp meters and analogue voltmeters with digital meters. The only amp meter which is still analogue is the wind turbine amp meter.
I now have 5 amp meters or PV string. Three of the string will feed directly the batteries while the other two strings will export to the grid.
In the middle I installed two power meters. These can measure current (A), voltage (V), power (W) and energy (KWH). One of the power meters is connected on the battery side, i.e. measuring what is going in/out of the batteries while the second power meter is connected on the load side, i.e. measuring what is being consumed (including the inverter load)

Inside the control box, Notice the fuses (left top corner) and their respective 50 amp shunts. The power meters come also with their 100 amp shunts (right bottom corner).

With regards to voltmeter I found this cool device which displays both voltage and percentage charge.

The below are the 50 amp amp digital meters. 
(NOTE - These amp meters require an isolated supply from the current which they are measuring).  

I opted for these 32 amp DC Bussmann fuse holders which I soured from RS Components.

The Power meters which I soured from ebay is displayed below. It's quite cheap when one considers all it's functions.