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Base of lithium powerbox

April 12, 2020 — BarryK

I have constructed the base, or floor, of what is intended to become a lithium battery power box. See previous post in this new project:

The foundation is a good place to start, as you would build a house. Having the floor, how the rest will fit in can start to be seen. Here is the floor, with battery:


...that empty space on the side of the battery is where the electrical wiring will go, with a side-opening to enable easy access. Also in that gap, at the front there will be the front-panel sockets and coulometer LCD display.

There is about 20mm gap at the back-side of the battery, where there will be some cabling. The externally-mounted circuit-breakers will be directly behind the battery.

The DC-DC charger sits on top of the box, and grab-handles will also be screwed onto the top of the box.

Here is the detail of the floor of the box:


The floor is a piece of 9mm thick plywood, 235mm along the front, 225mm deep. I painted it, hence the off-white colour. I used marine ply, but anything will do, even a chopping board from Kmart or BigW.

Though, the chopping board would need to be 9mm thick or more. The screws are 6G 9mm dome-head metal/wood type, from Bunnings -- I couldn't find any shorter screws, hence the thickness requirement of the plywood. Well, actually, 8mm plywood/chopping-board would do, as the aluminium angle is 1.4mm thick.

The aluminium is unequal-angle, 12x20mm, 1.4mm thick. I cut each piece 3mm longer than the board, 45 degree cuts using a mitre-board and hacksaw. Three holes in each for the screws. I pre-drilled holes in the plywood, so as not to stress the plywood when screwing the screws in -- as they are close to the edge of the plywood.

I bought 20x12x1.4mm angle, 3m length:

Also, for later in the project, 3m of 10x10x1.5mm channel:

Only simple hand tools have been used, which I anticipate will be the case for the entire powerbox. 

Tags: nomad

Powerbox fuse redesign

April 11, 2020 — BarryK

Previous post for new camping powerbox:

A couple of days ago, created a preliminary circuit diagram, with quasi-physical layout:

After more study of other circuits, I have redesigned with two more fuses:


Previously, if the bottom-right circuit breaker was switched to open-circuit, while still charging from the car's alternator, it may have an odd effect on the +bus. Now, that circuit-breaker disconnects from the +bus, and another fuse has been added to the "DC out" (black Anderson plug).

It may be overkill, but I also added one to the grey plug, going out to the solar panel.

I also made a note for the red Anderson plug. Modern cars have "smart" alternators, where there is a shunt between the battery negative terminal and chassis-earth, just like I have done with the lithium battery in above diagram.

For the electronic control system of the car to recognise the existence of the DC-DC charger, the negative lead from the red plug must go to chassis-earth, preferably close to the car battery.

EDIT 2020-05-03:
A "protected +bus" has been added -- the "+bus" is connected directly to the lithium battery, whereas the "protected +bus" is on the other side of a 30A circuit breaker. Also, binding posts have been added. Both of these changes are discussed in a later blog post:

Consequently, the circuit diagram has been updated:


This was created by Dia (a Linux GUI application, available in EasyOS, Quirky, Puppy Linux, and most other Linux distributions). Here is the Dia file:

Here is the file exported to SVG: 

Tags: nomad

Cable sizes for battery camping system

April 11, 2020 — BarryK

This is a continuation of the new project, a portable lithium-battery power system for camping, see the first post here:

It doesn't have to be a lithium battery -- my project can easily be used with a deep-cycle AGM/GEL battery. The Amptron DC-DC charger that I am using can handle all types of batteries.

In previous camping trips, I used somewhat undersized electrical cables. I used a "6mm" automotive twin-core cable, 15m long, from solar panel to the MPPT battery regulator. From the battery to my tent I used a Narva "heavy duty" 5m cigarette-lighter extension cable (purchased from Autobarn).

Thinking about the cable run from solar panel to MPPT regulator. You need to be careful what the vendor is selling you when they claim "6mm". 6mm automotive cable is slightly less diameter than 10AWG. AWG is the same as B&S -- these are American wire standards, widely used internationally, including Australia.

I found a nice table of wire sizes, from here:


The table doesn't have it, but the wire diameter of "6mm" auto cable is 2.42mm. Those diameters are actual copper wire diameter, not including the insulation.

The big question is, how much power was I losing in that fairly thin cable? There is a formula:

Length (m) x Current (A) x 0.017
Voltage drop

Area (mm2)

...that constant 0.017 is for copper wire.

My 15m cable is 30m round-trip. My "250W" panel was at best only giving about 10A. Plug the values into the formula:

Voltage drop = (30 x 10 x 0.017) / 4.59
= 1.11V

Let's say that the panel is putting out a voltage of 16V, so the power output of the panel is:

Panel power out = 16 x 10
= 160W

And the loss in the cable:

Power loss = 10 x 1.11
= 11.1W

...that is a power loss of 7%

Do I want to throw away that much power? No...

Firstly, I decided on a shorter cable. I used 15m before, as there was one site where I had to place the panel a long way from my car and tent. However, can make-do with just 10m.

I purchased 10 metres of 6AWG from Big Al's on eBay. I like Big Al's, delivery has always been remarkably fast. Though, my purchases were pre-Covid-19, so I don't know about the current situation.

This is the cable I bought:


That is heavy cable! Expensive, but much cheaper than buying it locally. Plugging it into the formula:

Voltage drop = (20 x 10 x 0.017) / 13.30
= 0.255V

So the power loss is 2.55W, which is 1.6% ...ah, much better!

Then there is the 5m cable running from the battery (in the car) into my tent, to run light, computer, fan ...and maybe even a TV. I have a fridge, but that stays in the car.

I have not done quantitative measurements yet, but did have a problem on the last camping trip. I took two laptops, my old power-hungry one, and a modern baby one. I powered them (one at a time) through a 150W inverter, and it would cutout when tried to run the old laptop -- this was because the voltage into the inverter dropped to 11.5V, which causes the inverter to turn off.

On that occasion, I was also running an LED lamp, and was charging my phone. Sometimes plugged a USB 1TB HDD into the laptop.

So the plan is to upgrade to 8AWG cable, and probably keep the length of 5m, or maybe a tad longer, say 6m. Will need to do some calculation of power load and voltage drop first. 

Tags: nomad

Portable lithium power for camping

April 08, 2020 — BarryK

Unable to go camping, but putting home-isolation to good use -- starting a new project, a portable lithium battery box for camping.

My solar water distiller project isn't finished -- I had hoped that it would be, however, the last prototype did not perform as well as I expected. Sometime, I intend to modify the last prototype, to see if the efficiency can be improved. for now though, starting a brand new project...

I own a Dometic 45AH battery box, with deep-cycle AGM battery. This is lead-acid technology, and has various limitations:

EDIT 2020-05-09: Added item-7 to comparison list 

  1. Should only be discharged to 50%, any more will dramatically shorten the life of the battery.
  2. The battery must not be left in a partially-discharged state, it must be charged promptly.
  3. The number of discharge-recharge cycles is about 600-1000 (when discharged to 50%).
  4. Self-discharge about 2%/month at 20degC, 4%/month at 40degC.
  5. Lead-acid batteries are very heavy -- a 12V, 100AH AGM battery weighs about 29kg.
  6. Voltage drops considerably at lower state-of-charge.
  7. Discharge/recharge cycle 70-85% efficient (15-30% lost as heat). 

...they are just the ones that I can think if right now!

If the battery can only be discharged to 50%, that means my 45AH battery is effectively only 22.5AH. As I go camping infrequently, I need to be mindful of the self-discharge, and attach a battery charger every now and again.

Comparing the above items with a LiFePO4 lithium battery:

  1. Should be discharged no lower than 20%, otherwise life will be shortened.
  2. OK to leave indefinitely in a partially-charged state.
  3. The number of discharge-recharge cycles is about 2500 (when discharged to 20% capacity, 80% DoD), and about 5000 cycles when discharged to 50% capacity.
  4. Self-discharge is about 1-5%/month (I don't have any accurate figures for this).
  5. A 12V 100AH battery weighs about 11.5kg.
  6. Voltage stays fairly constant right down to nearly 0% capacity.
  7. Discharge/recharge cycle 90-92% efficient. 

Several years ago I bought a 110AH AGM deep cycle battery, but at over 30kg I could not lift it. Well, I could, at great risk of putting my back out. Sometime after that I bought the Dometic 45AH box --mostly because I could lift it!

So, finally have decided to go over to a lithium system for camping. I purchased an Amptron 12V 50AH battery -- oh joy, it weigh only 7kg! The company claims that even if discharged 100% (DoD), that is, down to 0% capacity, it will still give 2000 cycles -- hmmm. If I discharge it by 80% DoD (down to 20% capacity), that gives me 40AH, almost twice that of my Dometic battery box.

Here is the company web page for this battery:

...and immediately you will see a problem: the price. yes, AU$545, plus postage. For 100AH, you would be looking at around AU$800 - 900. You can find cheaper on eBay, but beware, they are cheap for a reason.

Anyway, I have been squirrelling-away parts required for this project over the past several months. Have recently ordered a couple of final parts off eBay -- coming from the other side of Australia, so may take awhile. Just about have everything ready to go, sitting here in my loungeroom, and can now eye-ball it all and visualize how it will fit together.

What I am proposing is a portable box, that will sit in the front of my vehicle, where the passenger's legs would normally go -- I am hoping that there will be enough space for the occasional passenger to place their legs beside/behind/in-front of it -- whatever.

But it could go anywhere, for example behind the front seats -- you would just need to run longer cables from the car's battery.

To get the ball rolling for this project, I need a circuit diagram, but I want one that also indicates the physical layout. I constructed the diagram in Dia, an app in EasyOS and EasyPup. This is the result, exported to PNG:


Here is the Dia file:


Here is the file exported to SVG:


EDIT 2020-04-12:
The circuit diagram has been improved, see later post: 

...more fuses, to make it safer.

A note about Dia: I found it to be adequate. I couldn't see how to create arbitrary snap-to nodes. There doesn't seem to be any object rotation. These are features that were in diagramming apps that I used 20 years ago in Windows. Anyway, managed to construct a reasonable-looking diagram.

The left side of the diagram is the "front", which would be the side facing the door, so that the readouts can be seen. The right side is the "back", furthest away from the door.

In a vehicle, you would bring a single-core cable from the ignition key. This will have 12V on it when the ignition is turned on, and tells the DC-DC charger that charging will be coming from the car's alternator.

A twin-core cable will come from the car's battery, to a red Anderson plug. Both of these can be easily unplugged if it is desired to remove the battery box from the car.

The circuit breakers are there just-in-case. but probably useful to turn off if not going camping for awhile -- the DC-DC charger does draw a small current in standby mode.

The Amptron coulometer LCD display also draws a small standby current, however I have wired that directly to the battery terminals, as it needs to be calibrated for the battery, and calibration might be lost if power is disconnected.

The black Anderson plug on the "front" is DC output, for whatever purpose required. It can also be used for charging the battery -- I have an Amptron mains-powered 15A LiFePO4 battery charger, which can plug into the black Anderson plug -- handy to recharge the battery if it is not being used for camping, maybe removed from the car. 

That's enough for this blog post. I plan to provide more details as the project progresses, such as where to buy the various components, design of the box, putting it together, and anything else required. 

Tags: nomad

Distiller basin-type proto-3 test result underwhelming

March 04, 2020 — BarryK

This has taken me by surprise. I have posted reports on what was intended to become DIY plans for a solar water distiller. Last post here:

...there have been many prototypes, and the latest is "basin-type prototype-3". Yesterday was a sunny sky, just a few wisps of cloud, predicted maximum temperature of 32 degC, so I decided to test the distiller.


I put in 1.5 litres, then used wood shims under the feet to level the basin -- very easy to do, just make sure the water is spread across the entire surface. Then added another 2.5 litres.

Here are the measurements during the day:

Full sun at 8.15am
5mm water in bottle





Stopped at 6.00pm

Total collected distilled water: 1.23 litres

That is not as much as expected. See here for comparison:

And for the record, some further analysis that lead to design of the latest prototype:

The current design, with 20 degrees glass slope, has very large side-walls, and the temperatures measured on the back outside are rather high. I might construct insulation on the side walls and test again. Note, those top and back temperature measurements were taken with the IR meter held about 2 inches away from the surface, about 3/4 the way up the glass and the back side. 

Tags: nomad

Toughening up a 4wd for driving on corrugated roads

February 28, 2020 — BarryK

Outback dirt roads in Australia are famous for their bone-shaking corrugations. I posted about this awhile back:


I will be upgrading to a 4wd soon, with the intention of being able to handle these roads, and also to drive on soft sand tracks. So, I read with interest any experiences and information about toughening-up the vehicle appropriately.

A few days ago, I came across a Facebook post by Benno. Benno took off into the Red Centre of Australia in his new Jimny 4wd, driving 10,000km, 2,000km of those on corrugated roads.

Now that is fascinating. I have done a couple hundred km, and it felt like my car was shaking to bits. Okay, it was only a road car, Holden Barina, with suspension only designed for smooth roads.

This is Benno's Facebook post:

This is a photo Benno posted. The trailer is custom, with tyre-width to match the car, and the original tyres off the Jimny:


Quoting Benno:

The trailer had my bed in it plus battery and charging for the solar panel. Chairs and table and my chemical toilet plus 2 more jerry cans. The trailers tare is about 140kg. I estimate that I pushed it to the 350kg limit with a tow-ball loading of about 40kg. I fitted the tyres I took of the Jimny onto the trailer. The suspension on the Jimny gave up the ghost after 2000km of corrugated road, but I got into Coober Pedy. Found out that TG just released the 40mm lift kit which I had sent the closest installer which was in Alice Springs. Also did my 10k service in Alice Springs. The people in Alice Springs sure know what they do. I can only recommend it. My Jimny is automatic, and if you set it on cruise control, it just goes. Towing the trailer was no issue I would even say that the trailer stabilises the car on corrugated roads. There is always a surprise around the corner, but the Jimny has mastered them all in its stride. From bulldust holes that could have swallowed a truck to cattle grids that had a 10cm step up invisible potholes (more like open-cut mines) to rocks on the road, you would never believe they fit under your car. And whenever you were flying over the corrugation and court yourself thinking, "This is actually not too bad" then this was precisely the point to get ready for the next surprise. But all in all, I would do it again in a heartbeat. 

I posted a reply:

When you say that the suspension "gave up the ghost", what actually happened to it? 
Benno replied:
When you travel over corrugated roads for extended periods, the oil in the shocks heats up, and cavitation can cause the oil to foam, in which case the oil in the shock absorber loses its viscosity and simply stops doing its job. Because of the weight in the back and the tow-ball loading, the shocks collapsed, and I was riding the rubber bumpers. This occurred going around a corner and just given me one more of my unforgettable memories. The back dropped by about 10cm, enough for my trailer chain to hit the road. Suzuki Australia offered to replace the shock, but I decided to upgrade. The original shocks are not built for this kind of work, so if you choose to drive on corrugated roads you probably can do it with very little weight in the back, then I think you will be ok. If you intend to do some overlanding, you have to do some modifications. 1st Tyres, 2nd Bullbar, 3rd Spotlights and shocks. And if you want to put your Jerry cans somewhere, you need a roof rack. After all that you learn to travel light. You know the weight of everything you put into your car. Then comes the point when you simply give up because of all the necessities the better half requires and get a trailer, which I find is the way to go. If you get a trailer, make sure it fits the profile of the Jimny as wind resistance is the most significant factor when travelling. So keep your speed to 100 or less and watch what you put on the roof rack. 
Fascinating! I am beginning to understand why so many serious 4wd'ers do a lift, of at least 40mm. Superior shock absorbers, with longer travel are put in, and most people also go for fatter tyres.

I also recently posted about live-axle and IFS (Independent Front Suspension) in 4wd's:

The "old school" front live-axle is superior if you want to do a lift. The problem with IFS, as I understand it, is that a lift will increase the angle of the CV joints, greatly increasing their wear rate.

Then there is the question of legality, and possibly voiding the vehicle warranty. To find out about legaility in Australia, this is a great page:

...that page is written for WA, where I live. Basically, the vehicle height must be increased no more than 50mm (2 inches). Ah, that explains something -- many new Jimny owners are going for an ARB or Tough Dog (TG) 40mm lift kit, with a tyre size of 215/75R15, up from the stock 195/80R15.

The "195" and "215" figures are the tyre width, going to some online tables, I see that the tyre height is increased from 693mm (27.28 inches) to 704mm (27.7 inches), a difference of 11mm.

That tyre size jump will increase the vehicle height by half of that, in other words, 5.5mm.

So, the ARB or TG 40mm lift, with those 215/75R15 tyres, will increase the vehicle height by 45.5mm, which is legal. Very interesting! 

Rereading Benno's posts, it seems to me that what actually failed was the coils. The sudden drop of 4 inches would happen if the coil springs broke. The Jimny has coil springs front and rear. Certainly if the shock absorbers were no longer doing their job, or less so, that would have put enormous stresses onto the coil springs. The effect of the trailer would be to tend to keep the vehicle body steady, further stressing the coils. So one thing lead to another.

Which does make me think, a Jimny without a trailer and not to much weight in the rear, would probably be OK. Well, Benno did say that.  

Tags: nomad

Finishing touches to solar water distiller

February 26, 2020 — BarryK

Today finished off construction of the latest solar water distiller, intended to be put together as DIY plans. The previous post is here:

I am using a piece of 3mm window glass, not low-iron, just ordinary window glass, as used in my tilted-wick prototype:

...that glass is 572x672mm.

The wood frame of the latest distiller is sized such that the glass only overlaps about 10mm onto the frame, the wood being 19mm thick. I purchased silicone foam strip for the glass to sit on:


...I ordered 3 metres of 5x10mm (second from left in above photo), at AU$7.22.

Note that some vendors on eBay have solid silicon strip, but I thought perhaps that would be too firm.

I ran a bead of white silicone sealant around the wood frame, for the strip to sit on, and placed a MDF sheet on top to hold the strip flat while the sealant set. Later, ran another bead around the inside, where the silicone strip meets the wood, so that no water can seep underneath the strip.

Then there is the question of some kind of brackets to hold the glass in placed, firmly pressed against the foam strip. There are various ways that the brackets can be designed, what I did was buy 1 metre of this, at AU$7.40:


...I marked out 25mm lengths, and holes suitable for inserting 6G wood screws, then used a hacksaw to cut off the bottom flange, then each 25mm length. Tidied up with a file.

I bought a packet of wood dowels, 38mm long, 10mm diameter, 50 pack. Prestige brand at Bunnings. Oh, I see, don't seem to be stocked anymore, but these slightly smaller one should be OK, at AU$2.80:

Um, the "Tools" section of Bunnings does have these, more expensive brand:

I cut some of the dowels in half, length-wise, and this is what the final bracket looks like:


...notice that the screw is at a slight angle, not 90 degrees to the wood surface.

And after installing all of the brackets:


Almost finished! Now for the water inlet and outlet...

For the water inlet, I purchased a funnel from Supercheapauto. This is designed for automative use, and has a removable filter, and an adaptor for plastic pipe, at AU$9.99: came with a short length of pipe, however, I attached my silicone tube. The adaptor looked like suited for 9mm plastic pipe, so what I did was glue a 13mm trickle end-plug onto the adaptor.

I have posted about doing this kind of operation before. It requires special plastic-bonding glue. I use Selleys All Plastic Fix, at AU$8.35:

And the end-plug is a Holman's brand:

So that you can see how it is done, see this link:

And here it is all in place:


For the water outlet, I just used a cheap 13mm inline tap from Bunnings, at AU$3.97:


Shopping list, prices in AU Dollars:

Glass, 3mm, 572x672mm

Silicone foam strip, 5x10mm, 3m
Aluminium sail-track extrusion, 1m
Wood dowels, 8x32mm, 50 pk
Plastic funnel, with pipe adaptor
Plastic bonding glue
End plug, 13mm (Holman)
Inline tap, 13mm, plastic

Now I need to wait for a nice sunny day... 

Tags: nomad

Insulation under floor of water distiller

February 22, 2020 — BarryK

The saga continues. Here is the previous post in the gradual accumulation of what is intended to be DIY plans for a solar water distiller:

Now for the insulation under the floor of the basin. I was going to use fibreglass batts, after misadventure with using expanding foam with the previous prototype: that case, I had spread baking paper, which turned out to be a very bad idea. If I spray the foam directly onto the (slightly damp) plywood, it will stick and (hopefully) not lift off. So, decided to give expanding foam another go...

Before we get to putting in the insulation, there is the matter the inlet and drainage plumbing. Contrary to what you might expect, I put the inlet as a hole in the floor of the basin, not on the side wall. I also cut a hole for drainage. These two holes are at opposite sides of the basin, with the intention that water can be poured into the inlet and flow out the drainage hole, for periodic flushing of the basin.

Both holes were cut with a 16mm spade drill bit. Silicone tube is then inserted into the hole and sealed with black silicone sealant. I want the tube to bend 90 degrees, so I bought two Norma brand 13mm elbows:

...these are for automotive use, and the plastic will work up to 120 degC. Cost a bit more than trickle irrigation elbows from Bunnings though, AU$4.97 each.

These are attached to a short length of silicone tube, and I did use a cheap Bunnings trickle-irrigation plastic pipe clamp:


...the silicone tube could probably have been bent 90 degrees without needing an elbow, without kinking, and maybe with some channel to prevent it from flattening. Anyway, I went for the Norma elbow.

Next, it was glued into the basin floor, here is the underneath view:


...there are some pieces of wood placed to hold it in place while the sealant sets.

Here is the underneath view when both inlet and drainage pipes are fitted:


...notice the two blocks of wood in the top-middle. They are just some scrap pieces, placed there to give the bottom plywood something to screw onto.

The bottom plywood is two pieces. I won't give measurements, as it is easy enough if you build this, to measure and cut the plywood. It is the same 6mm marine ply that I used for the floor of the basin, cut from the same original 810x1220mm sheet purchased at Bunnings. Here is what the two sheets look like when fitted:


...16mm holes were cut for the tubes to stick through, and filed to allow the tubes to come through at an angle.

About those little holes in the above photo. 12mm holes. I had the idea of screwing on the bottom plywood sheets, then use those holes to inject the expanding foam.

Ha ha, that stuff has a mind of its own! Yes, I did try that idea, injected the foam, but it built up enormous pressure, and the plywood bowed out. I needed to have screwed it down more firmly in the middle. I had reasoned that the excess would come out of those holes, but that didn't happen ...perhaps the holes should have been bigger.

Aborted that. Took the plywood sheets off, bought another can of expanding foam and, the next day, after a spray of water, spread the foam all over the surface, as best I could anyway. This snapshot is just after spraying, it did expand some more afterward:


...baking paper was wrapped around the silicone tubes, with sticky tape, not that I really expected the foam to stick to the silicone tube, just being paranoid.

Waited another day, then used a large wood saw for most of the cutting, then a hacksaw blade to finish off, got it reasonably flat:


So, what's next? Obviously, any water placed into the basin is just going to run straight out of the pipes in the floor. However, the drainage pipe will have a tap attached and the inlet pipe will bend up and be attached to a funnel.

This means that there will be water in those pipes, and you might think that will mean heat loss. However, water is quite a good insulator, and mostly any heat loss would be due to convection, hot water rising and thus the water circulating -- which won't happen in this case, as the hot water is at the top.

Actually, this is an experiment. I will measure the water temperature where the pipe comes out the bottom of the distiller, very interested to find out just how much it will heat up. 

Shopping list (prices in AU Dollars):

Norma elbow 13mm x2
2x $4.97
6G 16mm wood screws, 40pk
Expanding foam, 750ml (Bostik)

* I used two 500ml cans, however, that was due to a misadventure. A single can should be OK, and probably it will have to be more than 500ml. 

Tags: nomad