When I replaced the PDU with my version I did not bother with a battery charger.  As we never had a hook up, there was no point But last week we spent a few days on a campsite – with a hook up!!! Maybe we are getting old.

We didn’t really need it, but I reckoned on a campsite nowadays you have to pay for a hook up whether you use it or not, and so it’s best to use the site’s electricity rather than my gas for heating.  We also found out, after nine years ownership, that the hook up also heats the water. This is good but there does not seem to be any control of the water temperature and its gets very hot.

The little solar panel kept the battery charged, but I thought it would be good to be able to charge the battery conveniently from the mains. We can charge it now, but it involves a cable running across the floor from a mains socket over the fridge on the left to the battery compartment on the right.

The old (horrible) PDU had a built in charger which gave 18A!  Why? That is a continuous 200W. which averages at 5KWh per day. That is more than our house!

But I pirated the mains connector from the old PDU and attached it to a 4 way mains socket.

Then I plugged the old PDU connector into the Van Harness giving me 240V available right beside the battery.  

Then, on site,  all I need to do is simply plug in my Ctek charger. and connect it across the battery.

It is capable of providing 5A or 120AH per day.  My weekly usage is only around 72AH.

So, now if we go on site and get a hookup we can leave the lights on all day (not sure why) and stay nice and warm and have hot water without it costing us anymore than the site fee. In reality it would be useful if we stayed on a site for a week without driving in winter.  We haven’t done that yet – in nine years.

In the last nine years we have never needed to charge the battery. The alternator and the small solar panel has taken care of it.  But we have only ever used a hook up twice, and that was this year (2022).

I guess if we are on a site and a hook up is included in the site fee we may as well use it, and save the gas. When bought in 13Kg canisters, the KWh works out the same as domestic electricity. On cool days  I guess we would use an average of 1Kw while we are up and about or 16KWh per day.  That would cost around £5 in gas so this is an indication of how much extra we should pay for a hook up (if we have a choice).

UPDATE
I managed to flatten my leisure battery!
Bummer.
I left the van parked up with everything switched off but I forgot to switch off the fridge and it was on battery power.
Now the fridge is switched off when the engine is not running BUT I left the fridge door slightly open and the fridge light was on.
It’s only 2 watts but that corresponds to 4 ampere hours (AH) per day. It was March so the wee solar panel contributed very little.  A month results in 112 AH – so flat battery.
I should have used the isolator switch.  Anyway I charged it up again with the CTEK charger and it’s working OK but capacity is almost certainly reduced – but to what?
After charging the wee solar panel has kept the voltage of both batteries around 12.8V

Back in 2014 when I first did my calculations I estimated that phones, tablets, and computers would take an average of 14AH a week while were out and about at festivals and on holidays.

Things have changed in five years.  The technology items have got more power hungry and we find that we use the van a lot to visit folk so we spend a lot of time sitting in it. So we use more power demanding technology more often – a classic double whammy.

Here is what he have been doing over the last (incredibly wet) week in the van. (most charged from Buck/Boost converters so capacities normalized to 12V)

That’s about 42AH per week!!   In 2014 I estimated 14.1AH!!!!  Add in the 13AH for the fridge re-igniter and 15AH for the lights and we are using around 72AH per week.

If you compare my various estimates you may see that they vary from page to page.  Not a lot. This is simply because as time goes on I can estimate better.

Now this has been an unusual week and the battery has survived because the week has been punctuated with some travelling and a couple of times I ran the engine  and the wee solar panel has helped a little.

But more power is needed for this damned technology.  I don’t need 72AH per week. The leisure battery can still supply a fair amount of power before it reaches 50% charge and the last weeks consumption is abnormally high, but a bit of a safety margin would be good.

So I replaced the 10W panel with a 40W panel (it still fits inside under the roof window) I can get 4 times what I calculated  last time -about 8AH per day, probably 12AH per day in the summer months.  That would cover everything we use.

In the winter I will get less from the solar panel, but 45 mins running the engine (stationary or travelling) would compensate for a days usage.

A non standard approach

The usual method of using a panel is to attach it to the roof then use a charge controller to regulate the charge. Reading on the forums, the biggest hassle seems to be with charge controllers and the fitting of the panels.  So I decided to fit a 40W panel INSIDE the van under the roof window and not use a controller.

After a few days of glorious sunshine without a controller , the batteries were up to 15.6V.  This is too high, so obviously a controller was needed, so I made one.
Here it is:-

The sun shines and the battery voltage rises to 13.8V,  then the relay operates which switches the solar panel OUT.

The battery voltage will fall, very slowly, due to the current taken by the relay.
The voltage gradually drops to around 13.1V and the relay drops out (minimizing drain on the battery) and the solar panel switches IN.  The load on the battery at this point is around 5mA down through the Zener diode.The LED is simply to tell if it is working or not.
The voltage will always fall to 13.1 (or below at night time) as the o/c voltage of a flooded lead acid battery is around 12.7V.
When the panel switches in again, the leisure battery voltage can only rise as fast as the vehicle battery. So the lowest voltage battery will charge first then they will charge together until the voltage reaches 13.8V.  This is where we came in.
During the winter, there is little charge from the solar panel, but by simply removing the fuse, the controller is disabled, and all of the current from the solar panel will feed into the batteries utilising those days when we do get a bit of sunlight. The voltage now may get above 13.8V

The wiring needed a slight mod to incorporate the controller,

The panel supplies BOTH the leisure battery and the vehicle battery. They are separated by a couple of diodes so they can both be charged by the solar panel but cannot discharge into each other. This means that the lowest voltage is charged first then they charge together until the leisure battery reaches 14V.  So the panel is looking after them both. The added bonus is that the small steady drain to the remote locking mechanism is compensated for.

I think the Nuevo habitation electrics are now finished.

We have had it now for 5 years and covered 80,000 miles, spending hundreds of nights in the van.  We have used a hook up once the only time we were on a campsite.  The rest of the time has been wild camping or a folk festivals with few amenities.

Update.  A few days ago the company I bought the van from phoned to ask if I’d like to trade it in.  I considered the offer for a millisecond before saying NO.  I have not seen ANY van which is more suited to our lifestyle.

Update 9/8/2020
Thanks to Covid 19 the van has not been used since late last year. The solar panel and controller have kept both batteries at 13.2V without attention.

Update 13/04/2022
We only had one trip in the van last year, but now we are getting it ready for this year.  When I pushed the button to check the battery voltage I blew a fuse!  It turns out this is a fault in the digital panel meter.  I disconnected it. But thanks to the label on the fuse box telling me the fuse number and the position, it was fixed in couple of minutes.

A new panel meter ordered from ebay and fitted.  (The rather nice looking box is actually an old harmonica case.)

I found that the meter reads about 0.2V low at around 13V so ,as shown, the real voltage is 13.3V

The system has performed flawlessly and both batteries are still at around 13.2V.  But the leisure battery (Varta LDF90 which has been flattened once – see above)  and starter battery (019 Enduroline ) are  four years old now. We are heading off for a longish trip soon, so we will see how they are doing.

Update 31/08/2023
Just back from Towersey Festival.  Four days without the engine running and batteries still around 12.9V first thing in the morning.  The solar panel gives about 1.5A when the sun is shining and about 0.5A when the sky is overcast.
But I had managed to flatten the vehicle battery before we set out! The day before the trip we went to the van to load up luggage and we noticed the radio was on.  No sound, as it was set to bluetooth but not connected to anything.  The engine would not start!  But I have jumper cables, and I connected the leisure battery across the vehicle battery and that was enough to get her going.  I let the engine run for 45 minutes or so as we packed the van.  The next day and every time since the engine has started without difficulty.
But I did notice last winter that it was labouring.  The battery was fitted in February 2018 so it’s five years old now. Time for a replacement soon.  I’ll probably go for the same one I use as a leisure battery – a Yuasa L36-EFBfrom Tayna.

This is an experiment – I’ve tried a brand new highly esteemed 110AH battery from Banner. Now I’m running with a five year old 44AH starter battery from Alphaline!
We shall see what we shall see.

Well we saw! The wee 44AH battery may have been OK, but it was a worry. Due to unforeseen circumstances we had to take a two week trip. This was mostly parked up with no hookup and not a lot of engine running time to keep the battery topped up.
Now, the battery never failed, and it never even gave the impression that it was about to. But we had to stay in the vehicle most of the time, and had to keep charging a laptop, a tablet and two phones. The fridge was on all of the time and there would have been very little from the solar panel

We have never been particularly careful when using power, but because we were aware of the limitations of the battery we found ourselves switching off lights at every opportunity.

So we gave in and bought another leisure battery. This time it was a Varta LFD90 from Battery Megastore.

We were actually living in the van at the time and had little time to research batteries but I found this site which did sway me.

We got around four years from the previous Banner battery which works out at about £30 per year.  That is not bad really for the amount of work it has to do.

An occasional motorhome user using hookups or with a roof full of solar panels may not have noticed it was down to 25% of its original capacity (although he may struggle if he were where I am as I write this – in a municipal car park and the roof covered in snow)

We find we are using the lights after around 4pm and almost continuous until around midnight (with a 1-2 hour break for a meal) so that is about 6.5 hours. We also are charging up two phones, and ipad and a laptop every day. And of course the fridge re-igniter is on.

So even with the bigger Varta Battery we’d take 13% of the capacity per day.  Four days would be about 50% of the battery’s capacity.

But with a bit of forethought we can minimise that. We can’t do much about the fridge and lights and we can’t do much about the actual usage of the technology.
But we can use the engine and alternator to ease the load. The alternator will charge at about 10Amps in addition to charging up the laptop and phones etc at the same time. So we can recover ALL of the light and fridge load in under 30min with the engine running.

We can also use the time with the engine running to charge up the phones and laptop, at least 50%.

Our little solar panel will contribute a bit – maybe 1-2AH.

That takes the load charge from the battery down to only about 4%. This should be no problem for the battery.

This is an unusual situation for us – but in our little van we are warm and cosy and comfortable despite the outside temperature being below zero.

In the summer, with less time in the vehicle and less time on phones and laptops, and more from the panel we will not need the to use the engine for at least a week.

ROLL ON SUMMER

Addenda
The little Alphaline battery was put into a Vauxhall Agila whose own battery was struggling.  The simple battery preservation technique I described in Part 4 saved the price of a new battery.

A few changes to take advantage of the wee solar panel are called for.

But I think I can do better.  I am changing the unit to allow the panel to charge both the vehicle battery AND the leisure battery.  They are both new batteries and are both flooded lead acid.

The leisure battery, when the van is parked, supplies zero current.  The vehicle battery supplies the circuitry for the remote locking receiver, the burglar alarm, and the radio memory.  It’s not much, around 50mA.  That is about 1.2AH per day.  The panel should easily provide that even in winter.

When the power is split using diodes, it’s the lowest voltage battery which will take the current until it’s voltage appoaches the same as the other one.

It’s April as I write this and according to Meteoblue I should get about 950Wh from the panel.  Sounds impressive!!

But that is at 20V, and I don’t have a converter so that is 47.5Ah – or about 1.6Ah per day.  (If I put in a converter with 90% efficiency I could get that up to 1.9Ah but the added complexity is not worth it in my opinion)

The starter battery seems to be supplying a steady continuous 75mA which I suspect is mostly to the remote door locking system.  That is 1.8Ah per day. The leisure battery supplies nothing. Gosh that’s close. If I add in the combined self discharge currents (say 10mA total) that takes the discharge to over 2AH per day.

I am now not surprised when folk say their battery flattens in a month!

A few days after fitting the new arrangement, 10am, Weather a lttle cloudy.
The leisure battery is sitting at 12.9V taking and supplying zero current.  It is fully charged.

The starter battery is at 12.7V and taking 0.3A from the solar panel.  This will be partially replacing the power from the steady drain from last night. (radio, remote doorlocking etc). As the voltage increases to 12.9V the current will split and both batteries will be getting topped up.

Will this conversion to a solar make me change to a roof covered in panels? Absolutely Not. I stand by all of my original comments in Power use management.

Now, next post in another four years maybe?

I had established that the original system using relays to switch everything was inefficient and my original lashed up modification drastically reduced the load on the battery.

The mod was implemented using terminal strip fixed to the struts under the seat (where the leisure battery and PDU are located) and scotchlok connectors to tap into the wiring. The schottky diodes were mounted on the terminal strip.

The mod worked very well with no problems for four years but the wiring was not a pretty sight. So a replacement PDU (Power Distribution Unit) was needed.

I needed to be able to unplug the existing PDU and plug in my replacement so the first challenge was to source connectors that would mate with the van wiring. A web search (looking for matching pictures) established that they were BCA harness connectors and were available on line from caravan accessory shop uk. Then it was a matter of using the schematic in the handbook and a meter to find the connectors I needed.

As I have mentioned, the original system is horrendously complicated. The control panel is microprocessor controlled and gives an indication of fresh water level (very unreliable) waste water level (never worked for me at all) blown fuses (may have worked – I never blew any) as well as battery condition (useless). This means there are lots of wires in the harness that I simply don’t need.

The New System

I modified the leisure battery charging circuit so that the alternator will take the leisure battery to 14.4V (as it did before). I also fitted a solar panel! (after all my talk). It’s only 10W and its fitted inside the skylight. Now it gives out 10W at 18V so that’s around a half amp.

The way that solar panels work means that, unless I use a boost converter, I get about a half amp at any voltage (bright sun overhead of course)

SO here is the charging cycle:-

Start the engine – battery begins charging from the alternator at about 10A.
As the voltage rises to 14.4V the alternators current reduces. It’s possible to get a reasonable idea of the state of the battery from the charging voltage. Basically there is a finite resistance between the alternator output and the leisure battery. So as the leisure battery volatge approaches 14.4 volts it shows that the battery is taking less current and it is becoming charged.

Then we stop. If we are not on site (and therefore the fridge reigniter is not taking current) AND the battery is almost fully charged from the alternator, the solar panel will eventually take the battery up to a re-conditioning voltage. The solar panel can only supply about a half amp max when the sun is shining so this will only happen occassionally – which is good.
This can only happen because after my mods to the system, there is NO drain on the leisure battery.

If we are on site we start using power. We should uses about 4AH per night

Then we switch off the power and go to sleep. The sun rises long before we do and the solar panel starts to supplement the battery. It’s a bit weather dependent. On a bright summer day it may manage to put back in maybe half of what has come out the night before. But mostly it will be compensating for the fridge re-igniter On an overcast winters day it won’t do much.

But this works fine for our life style. In winter we don’t stay in one place for long and the alternator will do most of the work. In the summer we do hang around places, so there is not so much alternator charging and we don’t use much electric so the wee solar panel should keep the discharge level very low. We should only be using a total of around 2Ah per day or about 5% of the battery capacity.

The leisure battery

This is an experiment – I’ve tried a brand new highly esteemed 110AH battery from Banner. Now I’m running with a five year old 44AH starter battery from Alphaline!
We shall see what we shall see.

I decided to estimate the capacity of the battery. I charged it up using a CTEK charger on the reconditioning mode.
Then I connected a 55W bulb across it for 4Hrs. So I took 4 x 55/12 AH or 18AH from the battery. I then left it overnight and measured the open circuit voltage next day. It was 12.3V which indicates about 50% charge.
So the 110AH battery was down to around 36AH.
Now I must admit I was a bit surprised and a bit disappointed. The 110AH Banner battery had never had more than about 20-25AH from it so discharge would been closer to its 75% than 50% of its original rating. But it had been used for four years, so has seen quite a number of shallow cycles.

 Out of interest I did the same with the original 70AH battery mentioned in Part 1 and the 44AH one mentioned in Part 4.

The 70AH one measured about 40AH but the 44AH also measured about 40AH! Interesting – more later.

A rethink of the charging arrangement was called for.

The CTEK battery charger has a well developed charging cycle. The first phase is a constant current charge at 5A to push the voltage up to 14.4V. This is called in Battery terms, the “BULK CHARGE PHASE” Then it sits at 14.4V as the current gradually reduces. This is the ABSORBTION PHASE PHASE. Now this is not some magic in the charger – if you try to put 14.4V across a battery that is not fully charged the initial current will mainly be limited by the resistance of the connectors and cables. Then it gradually reduces until it is taking quite a low current.
In the Van, the alternator takes care of this stage.

Then the CTEK increases the voltage to 15.8V to “normalise” the cells. I.E make sure they are all fully charged and one cell is not stopping the others getting fully charged. In my charging system I “could” do this with a boost converter boosting the alternator voltage. Not sure I want to take it to 15.8 V as it will happen every time I do a long run. Maybe 15V may be OK.

The it puts the battery on a float voltage of 13.6V where it takes very little current. The only way I can do that is with a solar panel  The current required is so small that a small solar panel could manage even if it were very cloudy. I would need to ensure that when left for days or week , the battery was not discharging overnight. I.E. NO steady drains. But when on site the fridge re-igniter rears it’s head.

On site, the biggest daily drain is, believe it or not, the fridge re-igniter which takes only 80mA! But its on 24 hrs so its almost 2AH per day. The LED lights by comparison are around 1.5AH per day.

I am currently using a 44AH battery and under average use I will use about 4AH per day – lest say 10% of available capacity.
There is a very fast charger built into the van, it is the combination of the engine and alternator. But I really have no idea how long it will take to charge a 90% charged battery back up to 100%. Neither can I find any authoritative posts on the web. It’s another data gathering exercise.

But first it was time to carry out a long (four year) overdue job of tidying up the electrics.

The saga continues

SO after all of the calculations and planning, there we were ready to set of for our first festival at Moffat.

We had been been happy with our new battery but while I was arranging the van I noticed liquid in the battery box. Yep, it was battery acid. So I removed the battery and used kitchen roll to soak up over half a pint of acid. Fortunately the battery box is water proof. One cell in the battery was only about 1/3 full. I decided against using it.

But we had a festival to go to! The old 70Ah battery was 550 miles away. But I had bought a tiny Alphaline 44AH battery for my old caravan two years ago. When I laid up the caravan I brought the battery into the house, connected it to a 12V power supply (probably originally off an external disc drive) via a digital timer that switched it on for 1 hour each night. How would a two year old unattended 44Ah battery cope?

It was all we had. I installed it and set off on the Thursday afternoon. We parked in a space in the main street and used the battery as usual, although we did tend not to leave lights on unnecessarily . Not dark you understand, but just taking a little care.
I used the switch I had installed to switch off the control unit so that when we retired, current drain was limited to the fridge re-igniter only.
I had foolishly left my tablet (Nexus 7) switched on with the sat nav running, so we arrived with a flat tablet battery. I put it on charge from the habitation battery and left it till it got to about 50%
On Friday morning the voltage was 12.66V. More than I had expected. We continued, keeping an eye on the power and on Saturday morning the voltage was 12.57V, on Sunday 12.48V.
It was a great festival and we decided to stay on Sunday night. On Monday morning I measured 12.38V. I reckon that’s about 65% charged. So we used around 15Ah over Thursday night, Friday, Saturday and Sunday. We had the heater on most of the time we were in the van,

The engine was not started at all during the time and the battery had no charging from Thursday afternoon until we set of home on Monday, but the little 44Ah battery kept us going.

I’ve contacted the company that I got the Banner Battery from and I expect it to be replaced. Its 120Ah and a true deep cycle battery so I can expect 84Ah from it if pushed (as long as it doesn’t leak that is). I don’t think a week or two at a festival will be much of a problem.

Here is the estimate of the power we used.

I must admit I was pleased (OK, amazed) to see how close the power calculations tied in with the actual experience.

The trip home on Monday was about 90 minutes. I checked the battery on Tuesday morning – 12,9V – so it got fully charged on the way home.

So, what have we learned?

1. The power saving techniques work – there is no way that the tiny battery would have lasted us all of the weekend with the PDU system and the control panel

2. Using a simple digital mains timer and a 12V charger (not a battery charger) will keep a battery in good condition unattended.

3. We used about 15AH over 4 days taking care. With the proper 120AH battery we will have over 80AH to spare – we COULD manage three weeks without a EHU or a charge. But we’d rather not take so much care, act normally, and two weeks are fine.

Fast forward – Four years on