The Solar Power 'Salvos Project'.

This project will soon provide free electricity to a very poor & disadvantaged family.
Hopefully, this project will be repeated for many more 'Salvo Supported' families.

Thanks to the hundreds of readers who have supported this 'Power to the Disadvantaged' project. And the many who have contributed financially! (Specially the four pensioners who each purchased a $240 battery!)

With just one solar panel (250w) and one caravan battery, the unit below can keep a Freezer (60 watts) running 24/7 in the event of a power failure. For Fridge, Freezer & lights (140w), the same unit needs four PV panels (1kW) and four 100ah batteries. (eg. N70T)

Small home - Solar power supply

This project can 'solar power' the vital appliances in a small house! It is not cheap - but neither is the price of future electricity! Or the cost of replacing the contents of your fridge and freezer (which you WILL loose at the next power failure). As a former research tech with the Nat. Power Grid, I know the neglected state of the grid and that there absolutely will be an increase in blackout frequency.

Feedback welcome.. (via the 'Contact Us' page.)

Note 1:
The 'start up current of a freezer or fridge can be 8 times the running current - so you need a 1000w inverter to safely start the average (100watt) fridge/freezer.
Microwave ovens require double their quoted power - so the 1200w 'Inverter2' of this project can only run a 600w oven. (700w for maybe 10 minutes) (that's 120 amp from the battery.)

Note 2: You need short fat cables (3 or 4 mm dia) for the 'battery to inverter' connections.. This requires a good 'Gas Powered' soldering iron. And, without an expensive 'Crimping tool', the large 'Lugs' will require some thought. see note 'c5'.

Note 3: The two units (batteries and inverters) should be in separate containers and situated outdoors.. Clip lid storage containers are ok.
The caravan style batteries ('Deep Cycle' - NOT car batteries) can produce corrosive gas and should be in a separate container to the pictured Inverter unit.

Note 4: If you use the standard 'PWM' controllers, a "100watt" PV (solar) panel will only give 70 watt. (6 amp at 12v) (The full 100w requires the more expensive 'MPPT' controllers)(17v x 6 amp)
(MPPT = Max.Power.Point.Tracking - 'PWM' = Pulse.Width.Modulation)

Note 5: When buying a Freezer, go for a 'High Efficiency' rated one. They have 3" (75mm) thick walls and can survive the whole night without power. They also need less running power (eg. 80watt for 20 min in an hour)

Note 6: Even a 'dinner plate' size shadow on a solar panel will stop all power from that panel! (that's the main reason this project stays with 12v - all panels are wired in 'parallel' so one shadow will only takeout one panel.) (a 12v system needs thicker cables from panels to controllers - eg 2.2mm dia)

Note 7: If you don't get many hours of full sunshine - you can get 30% more 'panel power' by just changing to the more expensive 'MPPT' controllers. They might cost an extra $50 each, but that's cheaper than an extra panel. Also, if you are using more than 3 panels, you should use 'MPPT' controllers.

Note 8: Use "Pure Sine Wave" type Inverters.. Very few appliances function well on the cheaper "Modified Sine wave" Inverters.

Note 9: Battery Type?
a. Normal car batteries do not suit solar projects.. Their ability to stand daily deep discharge is severely compromised in order to cheaply deliver a high Starting Current.
b. 'Lithium Ion' is currently 'best' but very expensive and they are soon to be superseded by Graphene Batteries. The mining of Lithium (rare earths) also causes enormous damage to the environment.
c. Lead acid "Deep Cycle" batteries (eg. Caravan Batteries) are also soon to be superseded but currently are the best value for money. They can stand up to 20 years of being taken down to half charge every day. The four batteries in this project were $240 each. (N70T 100ah).
Note: Even if you only want to power a freezer while the sun is out - you still need at least a cheap car battery to keep the power stable. And, the freezer needs 75 amp for a second to start-up (10 times what a panel can provide.)

Note 10: Roof Mounted panels or Ground mounted?
Roof mounting has two disadvantages: a. The panels are hard to clean and 'dirty' can cause a 10% loss.. b. The roof is a very hot place, and the low air gap under the panels will keep them too hot to touch. A hot panel can give 20% less power and has a shorter life. So, a dirty + hot panel can be 30% down on power.
Ground based, on an angled (and possibly rotatable) frame can be easily cleaned; will be cooler (free air underneath); and can be better angled to face the suns track.. So, ground based can require 40% less panels.

Note 11: "Equalizing Mode".. Many first time purchasers of 'Charge Controllers' notice their expensive 12v battery being overcharged - they post the on-line question..

Why is my Charge Controller overcharging the Battery - up to 16volts?

Most 'Charge Controllers' initially (and at regular intervals - eg monthly) run 'Equalizing Mode' for a few hours.. This involves taking a 12v battery up to about 15v to remove sulfate crystals and prevent the acid settling into density layers. This initial 'overcharge mode' prompts many purchasers to believe their controller is faulty.

Note 12: "Common Positive" vs "Common Negative" (Positive Ground vs Negative Ground)
To save money (and confuse the builder) many controllers are designed as "Common Positive".
This means that all 3 'Positive' terminals (Panel/Batry/Load) on the controller are internally shorted together!! (bang!) and all the 'controlling' is done via the negative terminals.
This is OK if you are aware and you don't plan to "earth" your negative rails. The original circuit we published will NOT suit "Common Positive". (The modified circuit has a 'Pink' text note.)

Can you add something to this article??
New points/corrections are most welcome.. (via the 'Contact Us' page.)

Construction Notes:

c1. Duplication is the key insurance.. While you are without grid power, if some component of your 'solar unit' fails, you won't have time to buy replacement parts before you loose the contents of your freezer. A dual (duplicated) solar system will allow you to function on half power. You may loose your TV and Microwave - but not your fridge and freezer.
A small disadvantage of "dual" is that the 240v outputs of the two 1200 watt Inverters can't be joined to run a 2400 watt device. So, you should think like a caravan owner and buy a few 'Low Consumption' style appliances. Eg. Toaster, Jug, Microwave..
You need TWO 240v leads into the house.. Because fridges and freezers both need 1000watt to start, and, after a short blackout, they will both try to start at the same time, therefore they need to be on different inverters (the two 240v leads)


c3. The  'Anderson Connectors' (to the batteries)..
We used 50 amp 'Anderson Plugs' wired in parallel to allow a 100 amp draw.
That is only 1.2 kw - but enough for a cottage or during a Grid failure.

Battery Leads

The above 3 plugs connect to the 3 sockets shown in the main image as "to the Battery".


c5. For long life, the 'Lugs' on the 'battery to inverter' cables (and the Anderson plugs) need to be soldered.. Without an expensive 'Crimping tool', these large 'Lugs' will be hard to attach.. The options are.. Totally fill the lug-cups with solder: Modify an old pair of 'vice grips': I used a small block of very hard wood with a half circle groove - then I hammer/indented the lug with a hand shaped bolt.


Basic Circuit Diag.


Circuit Diag.

Setup for soldering big Lugs on fat Cable..
(The Lug shown below is from a 50amp 'Anderson plug'.)


Use a Gas powered mini-torch and Soldering iron. (both at the same time on 7mm battery cable!)

Solder Jig

Use cheap pliers as the jaws will get heat affected.
Don't use paper, cloth, wood to hold the hot lugs (the lug will be tarnished by toxic gases)