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Installation of the coulometer LCD display

April 29, 2020 — BarryK

The previous post in the powerbox project:

The finishing touch is to install and calibrate the Amptron coulometer. As already discussed, the shunt is already mounted on the wiring-board. This is what I have:

If you search on eBay and elsewhere, for "battery coulometer", you will find this available from many vendors, and there are also setup videos on YouTube.

Installing the coulometer

There is a shielded cable to connect the shunt to the LCD display, and this is a problem, as it is very long. This is for the situation where you want the display somewhere else, maybe on the dashboard of the vehicle, or whatever.

I want to cut it right down, as the LCD display is close to the shunt. So, I cut the plugs off each end, and joined the cable. I am familiar with delicate electrical work, as I was an electronic engineer in my working days. I have a small soldering iron and fine solder for the purpose. The wires inside this cable are so tiny, this photo blows it up, but in actuality they are so tiny. The photo shows after I have stripped each wire and twisted them together:


...I then very carefully soldered each join, then put heatshrink tubing over each join, then bound it all together with electrical tape.

I know that such delicate work will be a challenge for many -- well, you could just go and buy a ready-made powerbox! But it is not insurmountable. The wires are so tiny, I stripped them with my thumbnail, pressing onto the table -- my cable stripper does not handle such tiny wire.

Calibrating the coulometer

I watched one of the YouTube videos on how to calibrate the coulometer, but it is misleading. They set "full" and "empty" corresponding to certain battery voltages, but this could be very inaccurate.

Here are the instructions:



What I did was first charge the battery to 100%, using the Amptron mains-input lithium 15A battery charger:

...this has eyelet lugs, that I replaced with a black Anderson plug -- very convenient, just plug it into the powerbox, and it will charge until 100%.

Following the above instructions, I then pressed the "up" key for three seconds to set the display at 100%.

Following the "User Settings", I then chose battery capacity as 50AH -- note, the buttons have to be very firmly pressed, and getting out of "engineering mode" proved to be difficult.

That's it, I did not set "FULL" and "ZERO" voltages, as that is not a reliable indicator of 100% and 0%.

Using the coulometer

I plugged my Powertech 150W inverter (purchased many years ago from Jaycar, and used on many camping trips) into a cigarette lighter socket, and plugged in a desktop lamp:


Fantastic, working! Here is the LCD display:


Very nice! That snapshot is after running the lamp for a short time, the capacity has dropped a bit below 50AH.

EDIT 2020-05-04:
After further reflection, I decided it is a good idea to minimize "error creep" of the State-Of-Charge, by setting a lowest voltage for 0%. See this later post:   

Tags: nomad

Wiring-board installed in powerbox

April 29, 2020 — BarryK

In the previous post, I wrote about some compromises when wiring-up the wiring-board:

Now for some photos showing the wiring-board installed. Firstly, here is the wiring-board all ready to be installed:


And here it is installed:


...quite crowded, but more so because of that extra terminal block. The previous post discussed how that could have been improved, with a distribution bus mounted on the wiring-board -- there is some space bottom-right of the board.

I also discussed in the previous post, the limited space to access the battery terminals. The unconnected eyelet lug in the above photo is waiting to be bolted to the battery positive terminal. I managed, just, and solutions to obtain better access are mentioned in the previous post.

EDIT 2020-05-02:
Both of these problems, battery terminal access and messy floating terminal block, have been fixed. See this later blog post: 

Tags: nomad

Reflections on construction of the wiring-board

April 29, 2020 — BarryK

Continuing the powerbox project, previous post:

The wiring-board has been completed and inserted into the powerbox. There are a couple of places where I improvised, due to not having the type of connectors desired...

DC-DC common earth

Top-right of the wiring-board, there are two porcelain terminal blocks, These will take the wires from the DC-DC charger. The DC-DC charger has three earth wires (black wires), a "DC input" (red wire), a "DC output" (blue wire) and "Solar input" (brown wire) wires. The three earth wires (let's call them "cables" from now on) are electrically connected together inside the DC-DC charger, so theoretically we only need one of them. However, for the lowest possible resistance path, I have joined them via the top terminal block, hence to the "-bus", like this:


...originally, I was going to daisy-chain the left-side terminals, however, the holes aren't big enough. So, improvised with eyelet lugs bolted together. What would have been ideal is this (instead of the porcelain block):

...however, that ships from the USA, currently not practical to buy. This also looks good, though not sure where it ships from (and ideally I want one that can be affixed to the board, which this doesn't have):

Incidentally, that 8-way busbar that I have used, two of them, is available in 6-way. Again, I don't know about delivery: 

Cable splitter

The second improvisation is splitting a cable. The "DC output" goes via the porcelain terminal block, to one of the 30A circuit breakers, hence to the "+bus" busbar. However, I wanted to branch "DC output" to the +ve binding post -- a convenient place to pickup the +ve voltage with protection of a circuit breaker.

I cut off two segments of a 60A terminal block, and wired like this:

img2 can see "DC-DC output" label, which comes from the "DC output" of the DC-DC charger. The other side goes to a 30A circuit breaker, hence to the "+bus". My klutz was to insert two cables into the left-side of the terminal, bringing out another cable to go to the +ve binding post.

A 3-way distribution bar mounted on the wiring board would have been far neater.

See bottom-right corner of the photo, "Red Anderson" label. This is from the other 30A circuit breaker, the other side of which is wired to "DC input" of the DC-DC charger. As all the cables from the DC-DC charger and 30A circuit breakers are just bare ends, I need an Anderson lug -- the other terminal on the terminal block joins a short length of cable with an Anderson lug on the other end.

This also could have been simplified. The terminal block join could have been eliminated by soldering an Anderson lug directly onto the cable from the 30A circuit breaker -- just might need a bigger hole in the back panel for the cable to feed through to the circuit breaker.

That extra terminal block does look a bit untidy, and clutters things somewhat, but it does the job.

Notice that there is masking tape with labels on all the cables. This is important to do, as it helps to avoid a wiring mistake. In the final assembly, there are cables all over the place, and the labels help greatly.

EDIT 2020-05-02:
The messy floating terminal block has been fixed, see this later blog post: 

Tags: nomad

Battery insertion and more bits and pieces

April 29, 2020 — BarryK

The previous post was "bits and pieces" information about construction of the lithium powerbox project:

This post is notes about battery insertion, and various notes about connectors. In a previous post, I had discussed concerns about the current capability of some blade fuse holders, and I also mentioned that spade terminals might not be suitable above 10 amperes -- today's post has more on this.

Today I inserted the Amptron 50AH lithium battery into the powerbox. The front and back panels have to be taken off, for insertion of the bracing bar that will hold the battery down:


Construction of the bracing bar is described in an earlier post. You can see it in the above photo, with a bolt that will be adjusted to provide tension. The bracing bar is 10x10mm aluminium channel, and the bolt is M4 16mm hex head, purchased from Bunnings:

I used two nuts on each bolt, to lock the nuts.

The battery is held firmly, but just in case, to stop horizontal creep, I put two pieces of old foam at each end, and on the side of battery facing the the front panel, put two pieces of 12x20 angle:


As the frame is made with aluminium, I placed electrical tape over the battery terminals before inserting the battery. Advice to everyone: do not skip this step!
Also, I wrapped electrical tape around the spanner, for doing-up the terminal bolts. Again, important precaution.

Which reminds me: in a previous post, I suggested that an extra 5mm height for the box would be an improvement. Yes, I have slim fingers, but it was difficult to get into the narrow gap between top of battery and top-inside of the box. Someone with chunky fingers would find it impossible. Make that an extra 10mm.

Oh, and about the spanner, do not use an adjustable spanner. A proper flat 13mm (for the Amptron battery) spanner is required. There is just enough space to slip a spanner over the hex head of the terminals, and very little swing to tighten it.

At the risk of being overly-verbose in this post, another thought has occurred to me. I did also mention in an earlier post that a wood frame might be better than using aluminium. It certainly would be safer when inserting the battery and accessing the terminals (note, I have not connected the aluminium frame to either +ve or -ve, which does make it safer). With a wood frame, the top plate of the box could be screwed from the top, such that the top plate could be lifted off, thus giving easy access for both inserting the battery and doing-up the terminals -- worth considering!

I do have thoughts how to design the wood frame, and if anyone wants to go that way, contact me. Or, if you create a design, let me know and I can post it.

Now for some connector details...


The bolts on the battery terminals do not screw all the way down, and require washers. I have used two washers plus the cable eyelet-lug. The binding posts also require an extra washer on each. The washer that I have used for both situations is this:

Also used these in a couple of places, 3/16 inch and M5: 

Eyelet lugs

Eyelet lugs are required for battery terminals, binding posts, coulometer shunt, and the 30A circuit breakers. I purchased these two sizes from Jaycar:

Spade terminals

I have posted earlier about current capability concerns. As I am soldering all connections, not crimping, I purchased these female spade connectors:

However, they have very thin metal, and I could feel they had less grip compared with others that I already have. Those others are going to be much more suitable for currents up to 15A, but unfortunately are only available as crimp-type:

...the plastic covering is very tough, can't even get it off with a hacksaw, so used my soldering iron to cut down its length. I then had naked connectors, to which the cable can be soldered. Note, these connectors will take up to 6mm auto cable.

Rubber feet

The wiring-board is not going to be bolted to the box, instead will rely on everything around it to keep it in place. There are screws sticking out the back of it, and as the back side will be against the battery, I screwed rubber feet onto the back side of the board. These ones:

Final product notes

Tomorrow the plan is to do some finishing touches to the assembly, and powerbox will be ready to go. It is anticipated that the next blog post will be about the final assembly.

An interesting point about practical usage: the completed powerbox weighs just on 11kg, which is OK for me, but I wouldn't want to lug anything heavier. The battery is 50AH, effectively equivalent to an 80AH AGM battery, which is also OK for me -- but what if one day in the future, I want to run more things off the battery, or find myself in situations where there are many days without sunlight, and want more battery storage?

No problem, just attach another battery. What I would need is another 50AH lithium battery, in a box, with fuse and short cable with a black Anderson plug. Plug it into the black Anderson plug on my powerbox, and hey presto, power storage is doubled (make sure both are full-charged beforehand!). Having two separate boxes is also easier to lift.

My Amptron mains-input lithium battery charger will also have a black Anderson plug, and can be used to charge either battery.   

Tags: nomad

Cable and soldering guidelines

April 27, 2020 — BarryK

Continuing the lithium powerbox project, this is the previous post:

Today's post has some bits and pieces of information about electrical circuit construction techniques. Those who are skilled with soldering, etc., will be OK to construct a powerbox like mine. Others, however, might need some hints.

Cable sizes

I have used various sizes of cable in the powerbox, as you can see in photos posted in earlier blog posts:

...the thinner cable is "6mm auto cable", purchased from Big Als via eBay. This has copper area of 4.59mm2. The thicker cable is two types, purchased from Altronics. I do have some 8AWG from Big Als, however that is twin core, besides, I want to use that for extension leads. So I popped into Altronics and bought one metre of each of their "61A" and "90A" power cables, red and black. Here are links to the red cable:

The differences between these is very interesting. The 61A cable has thinner strands, which makes the cable more flexible. Here they are compared with 6mm-auto and AWG sizes:

Cable type
Copper area

6mm auto
10 AWG
W4100 61A
W4216A 90A

Much more expensive buying locally, but ordering over the Internet is currently very slow, as vendors such as Big Als are based in the Eastern States. I have used both of those cables from Altronics, using up what has been purchased.


Soldering technique varies, according to individual style. I prefer the old-school copper tips on soldering irons -- modern irons do have copper tips, but they are coated with something -- that I file off to expose the copper -- as I find that solder sticks better to the copper surface. The copper corrodes, which is why it has the coating, but I use a file to keep the copper tip clean and flat. I also prefer a chisel-tip.

This is the iron that I am using for this project:

...60 watts is more than enough for soldering 8 AWG cable. I use a wet cloth to wipe the tip of the iron, but it would be nice to have this one, with stand and sponge:

I do not own a crimping tool, so all joins are soldered. Eyelet lugs and Anderson plug lugs are connected to cables by the flood-fill method. See demo here:

...difference for me though, is I apply solder to the expose cable ends, before inserting. This ensures that solder has flowed through all the fine wires in the cable, avoiding what is called a "dry join".

The video shows a flame being used to heat the Anderson lug. As I use a soldering iron, just a dab of solder on the flat surface of the chisel-tip, held against the side, will heat the wall and the solder can be inserted -- as the video says, take care not to overfill, otherwise it will overflow and run down the outside of the lug, perhaps rendering the lug unusable.

I also solder the ends of the cable that is inserted into screw terminals. This strengthens the cable, as the twisting action of the screw can break the fine wires, plus some wires thrust to the side of the screw are not tightly bonded electrically to the terminal.

Regarding solder, for this fairly heavy work, I prefer 1.6mm thick solder, available from Altronics:

...Jaycar, only has 1mm solder. Bunnings, on the other hand, only stock much thicker solder, used for plumbing.

Cable splicing

The iTECHBCDC25 DC-DC charger came with Anderson plugs, that I cut off. It also came with three more Anderson plugs with short lengths of cable. I need to extend the length of the cables coming out of the DC-DC charger, so I used the short lengths that were attached to the other three Anderson plugs. The cable is 10 AWG.

The most common way that two cables are joined together, what we call "spliced", is a special metal sleeve, which is then crimped. I have neither the sleeves nor a crimper. Instead, I used this simple method -- just push the two ends into each other.

Doing this, the strands become intertwined, and it will grip together. Note, I haven't tried this with the ultra-fine copper strands in the Altronics "61A" cable -- perhaps it might not work. This slightly out-of-focus photo shows the two cable ends pushed together:


It is then easy to solder, and forms a very strong bond. Heatshrink tubing needs to be slid over the join. many years ago, I bought a pack of mixed sizes, and the largest, 6.4mm, fits over 8 AWG cable. Ah yes, it is still available:

So, there are six Anderson plugs that I have removed the lugs from. I have plenty other Anderson plugs, but if I wanted to re-use these, it is possible to buy the lugs, in packs of 20, from eBay.   

Tags: nomad

Camping now allowed in WA

April 26, 2020 — BarryK

In Western Australia we had zero new cases of Covid-19 for three days, then yesterday there was one, a lady who arrived back from one of the cruise ships. As long as she hasn't started a new outbreak, things are looking very good, attributed to the very sensible restrictions imposed by the WA State government.

Consequently, the Premier today announced some easing of restrictions ...including allowing camping!!!

The eased restrictions are announced here:


non-contact recreational activities such as private picnics in the park, fishing, boating, hiking and camping − all in compliance with travel restrictions and the 10-person rule

WA is broken into regions, and we are still only allowed to drive within the region in which we live. There are DPAW campsites within the Perth/Peel Region -- but perhaps lots of people will be taking the opportunity to go to those campsites.

The main point is though, in theory I can now go camping. Just need to find a nice bushland or coastal spot within my region, that will not have many others also camping there.

Got to finish the powerbox first! 

Tags: nomad

Holders for blade fuses in powerbox

April 26, 2020 — BarryK

I posted yesterday about the start of wiring the powerbox, and a problem with using blade fuses at 20-30 amperes:

Originally, I had purchased this blade fuse holder 4-way box:

However, after watching the Redarc video (see above link), I became concerned. The Narva packaging has "Maximum 30A per circuit", and if you believe that, then you could put a total of 120A through it, 30A per fuse.

I did a bit more reading on the topic, and it looks like the 6.3mm spade terminals, as used in the above Narva fuse box, are only designed to handle 10-15A. A 6-way blade fuse box sold by Jaycar, which, apart from having 6 slots looks identical in its internal construction to the Narva box, states "15A/circuit max" and "45A/block max":

Jaycar have these female spade terminals, rated at 10A maximum:

Comparing different blade fuse holders and spade terminals, some are thicker metal, and appear to be designed to handle higher current.

Looking at what blade fuse holders are on offer, some indeed are thicker metal and grip the fuse more firmly. I bought two of these inline blade fuse holders:

...these have superb grip on the fuse, and actually require some force to fully insert the fuse. Good, but I want to mount these on my "wiring-board". That board is 150mm horizontal by 170mm vertical, 6mm thick marine ply, and I posted a photo of the start of wiring it in the previous blog post. Here is a photo with two of the inline blade fuse holders mounted on the board:


...overkill using that heavy-duty fuse holder for the 1A fuse. To mount these fuses on the board, I used Selleys "All Plastic Fix" glue and a small piece of plastic cut off a chopping board.

I have used that Selleys glue on previous projects. It consists of a primer-stick and an adhesive tube, and will glue all types of plastic, giving a very strong bond. The primer-stick lasts a lot longer than the adhesive, and I was reading somewhere, someone just used superglue and it worked the same as the All Plastic Fix adhesive tube.

The 1A fuse goes to the coulometer, via the shunt. The 15A fuse will go to the cigarette-lighter sockets. I still have to put in fuse holders for the DC-output black Anderson plug, and for the solar input grey Anderson plug -- these will be 30A and 25A fuses. 

EDIT 2020-04-26:
Fuse holders for the 30A and 25A blade fuses have been added to the board:


I wanted screw terminals, so chose these:

These blade fuses need even more force to insert than the other ones, so it is a very good connection between fuse and holder, so I am confident these will handle 30 amperes. The screw terminal holes look like they will take up to 9 AWG -- I have just noticed that the table here has the wrong area for 9 AWG cable -- it should be 6.6mm2.

Same construction, the two fuse holders have been glued together for mounting on the board. Given the force to insert and remove fuses, I put an extra piece of chopping-board plastic to more securely bond the two holders together.

The two red cables going out to the left, have Anderson plug lugs on the ends, for insertion into the black and grey Anderson plugs.  

Tags: nomad

Wiring of powerbox underway

April 25, 2020 — BarryK

I have started the internal wiring of the lithium powerbox, and this post is a progress report. Here is the previous post for this project:

It is progressing slowly, but surely. I had to pause for awhile to think about some construction details. Anyway, here is a photo showing the wiring so far:


...notice that the box is now painted black! I used a cheap "flat black" enamel paint spray can.

A change from the previous photo (see above link) is that I removed the Anderson plugs from the DC-DC charger and cut a round hole for the cables to go into the box. Next to the round hole is "half" of an Anderson plug -- this is for the wiring to the vehicle ignition key.

The wiring-board is propped alongside the box, for the photo. Top-left of the wiring-board is the shunt for the coulometer, the two black and red cables sticking out the top will go to the battery.

The "+bus" and "-bus" busbars were purchased from Jaycar:

The terminal blocks at top-right are for wiring to the DC-DC charger. I purchased porcelain blocks:

...however, afterward I noticed these, which would probably do the job:

The blank space on the wiring-board is where the fuse holders will mount. This is where I had some problems, as the blade fuse holders in local shops, of the surface-mount terminal-block type, seemed too "light" to handle 20-30 amperes. The engine-bay is a more extreme environment, but this Redarc video does show the potential for catastrophic failure when using blade fuses:

Snapshot from the video, of a melted inline blade fuse holder and fuse:


I intend to post soon about what fuse holders I chose, and what got rejected. 

Tags: nomad