What's that smell? When you smell bad eggs in the van ...

It is quite common to get a smell of bad eggs in the van. There are 4 possible reasons for this - 1 of them dangerous, but quite rare - your battery, 1 of them rare and expensive - your fridge, 1 of them highly unlikely - exhaust catalyzer ... and the remaining one is the most common - it's your grey water tank.

So the first thing to check is the dangerous one - on occasion an old or mistreated battery can start to cook and give off a smell of hydrogen sulphide - rotten eggs. This is quite a rare situation, especially with modern batteries, but you have to dismiss it first. The easiest way to check is to look for the obvious - the smell should be obviously coming from the battery. If this happens to you, I can't advise you as to the best course of action - it depends on the situation. Disconnecting the battery is the obvious thing to do, but only if you can do so safely. Calling for help is the most sensible thing to do.

Next is the fridge - if your fridge is very old and you know it's very rusty (round the back), then there is a possibility that it may finally have rusted through and leaked its chemicals. However this will be more of an amonia smell than rotten eggs. It is a very rare occurrence - usually the fridge stops working before it leaks, because it gets blocked inside with internal corrosion.

Next is an exhaust catalyzer - pre 95 classic Hymers (the subject of this blog and the FB group) don't have exhaust catalyzers, but I include this for any owners of later vans - it is pretty common knowledge that a worn exhaust cat can smell like rotten eggs. But if you have a pre 95 classic Hymer, it is very unlikely to be that.

So that brings us on to the commonest cause - the grey water tank. The grey water tank is the tank that catches all the water that goes down the plugholes from the sinks and shower. It may come as a surprise that it can occasionally stink so badly - far worse than what you see goes down the plughole, but there are good reasons for this.

The common reason is simply old age and a combination of other factors. Most grey tanks get emptied regularly, so they never actually get full. So what happens is that over the years, bits of food waste and other nasties that go down the plughole begin to accumulate by splashing on the walls of the tank, and also in the slime on the bottom of the tank. What happens is that you get a gradual build up over the years, and because the tank gets emptied so regularly, it never gets full enough to wash off the upper reaches.

Then what usually happens is that you get the first sunny day in spring, and up it comes through the plugholes. The smell can vary from an occasional whiff that makes you think that somebody has let go a cheeky fart, all the way up to a real pong in the van - it all depends on how bad it is.

The easiest way to check is to get your nose right down to the plugholes and hopefully you will get a confirmation whiff.

In any event, you should give your grey tank the once over every year anyway - especially if you full-time or use the van regularly.

There are several ways to solve the problem, including the famous "cola" method. As soon as anybody posts a question online about a smell, you will always get half a dozen people piping up saying to empty several litres of cheap cola down the sink and then go for a drive. It probably works, but I have never tried it myself. 

The reason I haven't tried it, is because it seems to be a temporary fix that doesn't get at the root cause of the problem. What the tank needs is the upper walls and ceiling getting washed, as this is where most of the smell should be coming from. The cola method may well do enough to dissolve away some of the smell, but there won't really be enough in there to effectively reach the upper bits of the tank. Whether cola will work in a three quarter full tank, I don't know ... I just prefer traditional household chemicals.

To do this the tank needs to be around 75% full, then add some chemical, and then go for a drive. If you are a regular van user you can even just build this into your regular routine - instead of emptying the grey tank automatically every time you have the opportunity - let it fill up, and throw a cup full of bleach down the plugholes, then drive for a day or so and then empty it the next pit stop. 

Other methods include using a cupful of blue toilet chemical, and I believe that Thetford even make a dedicated product.

Personally I use cheap supermarket bleach, or cheap pine smelling disinfectant, or a combination of the two.

All you have to do really is to ensure that you regularly drive with a half or three quarter full gray tank, so that the movement of the van sloshes the water up and over the side walls and roof.Quite often I will delay emptying the grey tank after we have both used the shower, to give it chance to slosh about in there.

The problem is particularly evident in the spring when the weather changes - your van may have been in winter storage, or you might just be setting off on holiday when it happens - if so, you hardly have to think about the other possible causes - it is always the grey tank.

Another tip is this - if you want to get some water into your grey tank for cleaning purposes, and don't fancy running the water pump for ages and ages, then I have found that if you have the standard old Hymer waste outlet - the one with the round wheel valve, then you can usually stuff the end of a hosepipe up it and shoot water into your grey tank that way - give it a try - but don't overdo it and keep an eye out inside the van - if you fill up the tank right to the top by doing this, it can come out of the plugholes inside.

Another tip for full timers is as I mentioned above, if you get in the habit of a small quantity of bleach every week or so, you will minimise the chance of ever getting the smell ever again.

Yet another tip is to get up close and personal with your grey waste. Give it a smell when you empty it - you can usually get a bit of advance warning if you have a slowly growing problem inside the tank and you will generally detect it this way long before it gets bad enough to come up through the plugholes.

Don't taste it though!

Inverters in the motorhome ... for beginners!

An inverter is a box of tricks that takes 12V DC from your battery and converts it to 220V AC as you find at home. You can then plug in a 220v item - like you do at home. An inverter is specified as having an input voltage and an output voltage. A typical inverter takes 12V DC in, and outputs 220V AC, and the power of the inverter is specified in watts.

So in very simple terms, you connect your inverter to the 12V supply of your van, plug your device (ie laptop charger) into the socket on the inverter and away you go.

Unfortunately it is not quite as simple as that and you want to avoid many of the problems that can arise if you don't understand the basic principles of power. Many inverters are supplied with wiring to connect to your 12V supply. Usually this will be a twin core wire, coloured red and black. One end is connected to the inverter, and the other end will either be bare, or with spade connectors, or with a cigar plug. In a motorhome, you should never plug an inverter into a cigar socket, unless the only thing you are going to plug in, is a phone or tablet charger. NOT a laptop or TV. If you want to use an inverter for these higher power items, then you must connect the inverter directly to the battery with proper connections.

A good inverter will be supplied with a suitable cable, and a fuse may be in the cable, or installed in the inverter itself. You should attach these cables directly to the battery terminals, using spade or ring connectors - if you don't know how to do this properly, then get help. If the supplied cable isn't long enough, then it is OK to extend the cable using a wire of equal or thicker dimensions. If the ideal cable length for your particular installation is longer than about 2m, then you should use an even thicker cable, because longer cables at 12V DC can suffer from voltage drop. This is the reason that most inverter cables are quite short, and also the reason that most van inverters are located quite close to the battery.

Every van is different, but in a simple installation, you should install the inverter in a convenient place, close enough to the battery, and where you can also get at it to plug in your 220v stuff. If you can't find a convenient place, then you can install the inverter out of the way, and plug an extension lead into it. Remember that you need to be able to get at the inverter to switch it off when not in use - most inverters consume power when doing nothing. If you are wondering if you can have an inverter feeding all the same sockets that are in your van already, that are live when you are hooked up, then yes you can, but that needs a more complex installation using an autoswitching inverter, which is too complicated for this simple guide - contact me if you want to discuss this. You should also be aware that most inverters have fans - which can be quite noisy, so bear this in mind when you locate it.

So now you have a basic simple working inverter setup - there are a few more points about inverters that i would like to touch on.

One of the hardest things to understand about inverters is that you can't just plug anything into them. In a house, you never think about it, whether it's a phone charger, a laptop, a TV, a hairdryer, a microwave or a fan heater - you just plug them in and off they go no problem. This is because in a house, you are being fed by the national grid. which for all intents and purposes is unlimited and lasts forever. There is a maximum though - most plugs are rated at 13amps, which in watts is equivalent to 3000w, or 3kw. This is a lot of power - enough for a 3 bar electric fire on full.

But in a motorhome, the power is not unlimited, it is supplied by your 12v leisure battery, and compared with the national grid, this battery is tiny. So unless you understand the sums, it is very easy to innocently overload a leisure battery, by asking it to deliver too many watts - far more than it was designed for.

This is the point at which most people switch off because they don't like sums and calculations, especially where electricity is concerned. So I have found that it easier to break it down into simple rules. In a basic motorhome installation, with 1 or 2 normal leisure batteries, and normal wiring, then you should never try to power anything through an inverter that generates heat - this means heaters, kettles, toasters, coffee machines, microwaves, hairdryers, cookers, ovens, slow cookers - this list is not exhaustive, but you get the drift.

What you can use is as follows - phone chargers, tablet chargers, anything USB, radios, CD players, small TVs - up to about 23" and laptops. Basically anything low power. Special cases - that are possible but need careful consideration are - e-bike chargers and curling tongs - these are medium power items that are on the borderline, so you need to understand how to use them in more detail.

Now here is the technical reason, for those interested. As the volts go down, the amps go up, but the watts remain constant. Lots of amps need thicker copper wire. To calculate the amps you need at 12v, you simply divide the watts (of the appliance(s)) by 12.

So - at 12v - which is the voltage of your van battery, to supply 100w of power, you need 8 amps at 12v - you divide the watts by the voltage. The wiring of your van, and the capacity of your battery to deliver amps is basically around 20 amps - any more than that and things start to get hot and stressed. As a rule of thumb, a normal motorhome battery and wiring system is capable of delivering about 10 amps of 12v - in classic Hymer vans, the fuses are 16a. The battery is capable of a bit more, but you shouldn't ask for it!

At the other end of the scale if you look at an average coffee machine, the label will say maybe 1200w - that is an easy calculation - 1200 divided by 12v = 100amps. So if you bought and connected a 1500w inverter to your battery, and switched on the machine, it would ask for 100amps. Normal leisure batteries are simply not capable of delivering that amount of power, and the result would be a ruined battery. But in your house - it's no problem - why? because the voltage is 220v, not 12v - so 1200 divided by 220 = 5.5a, which is under half of the maximum of 13a available from a house plug, so no problem, and it only needs a thin wire So that is why the simple rule states that you should only try and power low power items from a basic inverter installation in a van with a normal battery setup. A normal van setup isn't capable of delivering much more than around 15amps at 12v. Now of course you can have whatever you like - if you want a coffee machine and a toaster, powered by your battery, then you can - but it will cost - you have to install big batteries, thick cabling and proper metering and monitoring - this can easily run into thousands of pounds.

But if all you want is to charge your devices and maybe a TV and laptop, then you can, with a simple inverter setup that can easily cost around £100 all in.

But remember - there is no free power in a van - whatever charge you take out of your battery, whether it's your lights, fans, TVs, gadgets, through your inverter or not - that charge has to be replaced somehow - either by the engine while driving, solar, or on hookup. So although this article is specifically about inverters, remember that all aspects of a mobile 12v system have to be taken as a functioning whole.

So what inverter should you buy?

Pure sine or modified sine or quasi sine? These are terms that you will see in inverter ads. My simple advice, is don't bother about it - it's a technical discussion and there is lots of rubbish talked. Basically you can use any inverter that is sold either in shops or online. Most inverters nowadays are pure sine, and that's all you need to know.

The next discussion point is what inverter to buy. Ebay and Amazon are chock full of a bewildering array of inverters of all shapes and sizes and at prices from £25 upwards. Again, lots of folk have opinions and love to make statements on Facebook on what is best. A favourite opinion is that cheap "chinese" inverters are "crap", and you get what you pay for. My answer to this is that while there is always a possibility that any electronic product can break, it is bad business to sell a faulty or unreliable product - Ebay and Amazon function on the principle of feedback, and nobody survives very long if half the stuff they sell comes back for refund. The reality is that chinese stuff isn't all that bad, and all you have to do is look at a range of prices, check that the supplier has decent feedback, and choose the middle way - not the cheapest, not the most expensive.

However it is worth bearing in mind that there are a couple of manufacturers who are famous for the quality of their products and the most famous of these is Victron. Victron are a Dutch company who have a vast array of quality products, and are generally regarded as the best available. There is another company called Sterling, who are UK based and have a similar reputation, although as with most things, opinions always differ. Victron make a wide range of inverters, and their small inverters are priced similarly to the bigger models of other manufacturers. When asked, my standard answer is usually, I would rather have a small Victron than a big chinese one. There is also another brand called Epever, who are famous for their solar controllers, and they also make good inverters at decent money.

A common mistake that many people make when choosing an inverter is over specifying. You will see ads that offer 1000 watt inverters, or more, and it is easy to think that more is better. However this isn't the case. You should size an inverter for the purpose you need it for, and big is most definitely not better.

However you also need to understand what the numbers actually mean. The words to look for are "peak" "power" and "constant". The Chinese are very fond of big numbers - so they will put numbers like "1500w" and "1000w" and even more, but when you read the small print, it will say "peak power". This means that the inverter is only capable of supplying that power for a few seconds. This isn't as dishonest as it sounds, because many appliances, especially those with electric motors, do indeed need a lot of power for just a few seconds when you switch them on, so it's not all rubbish - it's just that they tend to overemphasise the "peak" and under emphasise the "constant". Constant is what you want - around 500w constant is what you want for a normal low power installation as detailed above. Quality manufacturers like Victron, on the other hand, always quote "constant". So a 300w inverter from Victron will have a peak value of over three times that - they just don't shout about it!

Then there is the matter of efficiency. Most inverters nowadays are over 90% efficient so effcieincy losses are not as important as they used to be. Big Chinese inverters are less efficient than small quality ones, and even though we have already discussed that efficiency isn't everything, there is another aspect to efficiency that is quite important in a van, especially if you are a "normal" owner with a single leisure battery. This is about "no load" or "standby" power. This is the amount of battery power an inverter uses while switched on, but doing nothing. A big 1000w inverter can use 1 amp of your battery every hour it is switched on. This may not seem like a lot, but that 24 amps if left on all day and night. So a good rule to obey when using an inverter is - switch it off when not in use. I have seen many a flat battery because of this - people think that if nothing is plugged into an inverter, then it is using no power. This isn't true.

So generally speaking, if the main purpose of owning an inverter is to power your 130W laptop, then a 200w or 300w inverter is more than enough, and smaller high quality inverters use less power on standby than bigger cheaper ones. Victron inverters take this one step further by having "auto sensing" - they take hardly any power at all until they sense the need. This is a useful feature to have if you forget to switch it off as it won't drain your battery. Other manufacturers also offer auto sensing.

At the time of writing in 2020 I have started to notice a new type of chinese inverter on the market that not only supplies around 400w reasonably efficiently, it also has built in USB sockets to charge phones and tablets, and it also has a digital display so you can keep an eye on your battery voltage - and all for £40. It is hard to argue with these for the money.

If you need more information or have questions, then ask on the Classic Hymers Technical facebook group. https://www.facebook.com/groups/297054424534823/

A typical Chinese 400w inverter showing plug sockets, 4 usb sockets and voltage displays. All for under £40

How an inverter should be wired to a battery - there will of course be other wires on your battery, but this is the basic idea - no cigar plugs or crocodile clips please!

An Epever 500w inverter - also has a USB socket.

Another no name Chinese inverter - this one is rated 150w, which is at least honest! It also looks well built.

Ring - another good middle of the road make

These are posh Victron inverters - the new ones have Bluetooth so you can see all the numbers on your phone in an app. Well worth the extra money.

Battery management for Classic Campervans........................... No excuse not to!

Battery management is about knowing how much capacity your battery has left in real time - similar to how a fuel gauge works on a fuel tank. It is very useful and informative to know just how much charge is flowing into and out of your battery, and how much power is left in the battery. 

To do this you need a gadget that measures all the current going into and out of a battery and uses these measurements to calculate the state of charge of the battery. Such a gadget is called a battery management system. Another name is a battery monitor.

Typical battery monitor

A battery manager consists of 2 main components - the sensor, and the display. The sensor measures the current and the display gives you the information.

Technical alert! Don't worry if you don't understand this paragraph! The sensor device that enables these measurements and calculations to be made is called a shunt. In simple terms, a shunt is a lump of copper through which all current in and out of the battery must pass. The shunt is actually a carefully designed piece of copper that has a precise resistance which can be measured as a tiny voltage - and these tiny voltage are directly proportional to the current. By sampling these voltages many times a second, a simple computer on a chip can calculate and store these values, and if it already knows the capacity of the battery, then it can calculate how much power is left in the battery. Not only that, it can calculate how much longer the battery will last under the current load, and in a charge situation, how much longer the battery will take to get fully charged for a given amount of charge.

For the non technical, all you need to know is that a shunt measures the power in and out of your battery.

In terms of our beloved Classic Hymers, they actually do include a shunt, which is buried inside the back of the fuse box, but this was long before cheap chip computers were available, so all that was possible back then is to use the shunt to drive a meter - the famous "Strom" meter on the panel, Strom being german for power. If the battery is receiving charge, the the meter would deflect into the green, if the battery is giving power, then it goes the other way into the red. The Strom meter is also calibrated in amps - plus or minus 25 or 30, but because of the technology of the time and the tolerances of the shunt, this is only a rough indication.

But nowadays you can do so much better!

So how do you fit a battery management system (BM) to a Classic? It is a lot easier than you would think.

As already mentioned a BM consists of 2 main components - the shunt, and the display. The shunt goes on or near the battery, and the display goes wherever is convenient.

Although the original Hymer shunt is fitted in the positive side of the battery system, and buried inside the fusebox, the modern convention is to fit a shunt on the negative side of the battery, and the easiest way to do that is to simply fit it directly to the negative post of the battery. You just take all the connections that were on the neg of the battery, attach them to one end of the shunt, and then attach the other end of the shunt to the battery neg. It's that easy. Some shunt designs are now so clever that they attach directly, and can be fitted in a couple of minutes. This means that it is easy to fit a shunt to a Classic Hymer.

The other component is a display, and this is also much easier to install than in the past because it doesn't need any additional wiring between it and the sensor because it communicates to the sensor wirelessly - via radio. All it needs is a 12v supply from the nearest convenient point. 

The display contains a small computer chip which does all the calculations - all you have to do is to program it with the total capacity of your battery in amp hours (ah). It needs a few charge cycles to settle down and make its calculations, then after that it is quite accurate.

Here are 2 typical displays (there are many others) - you get an accurate display of system voltage in this case 12.29v. Below that is the number of amps - in this case the battery is discharging 2amps. If it was being charged, the number would be preceded by a + sign. To the left there is a simple battery meter which is showing less than half full - the exact figure is shown below 33%. There are other numbers that represent amp hours and watt hours, as well as a clock and battery temperature gauge.

Recent developments have seen a whole new raft of products come on to the market. One of these is Bluetooth. You can now use your phone or tablet to display the information, and the data is sent from a shunt that has Bluetooth - also known, strangely enough, as a Bluetooth shunt! These are very popular, but you should think about it carefully before you buy one. The main thing is that in order to see the state of the battery, you have to get out your phone or tablet and launch the app - not always convenient. So you might prefer to have a permanent display, so all you have to do is glance at it, in which case you get a BM that has a dedicated display. However some folk are having the best of both worlds by dedicating an old phone, or cheap tablet, to be a permanent van display. This can also be used for many other things - limited only by your imagination.

Once installed and working, you then have access to a whole new world of information about your battery system. There is quite a lot of information on the display, but the three most important values are voltage, amps and a percentage bar graph that tells you the state of your battery - similar to a fuel gauge. 

Here are some examples.

Every time you switch something on in the van, the display changes and tells you exactly how much power that item is using. You can then, if necessary, modify your behaviour to suit how much power you have left. For example, if you switch on your TV or computer, you will be able to see just how many hours of use you will be able to get from the power available. 

If you have solar panels then you can tell how much solar power is going into your battery, less any power that you are using. At a glance you can tell how long it will take for the battery to reach 100%. This is particularly useful when there is not much sunshine about. Many solar controllers have power displays already, but they only tell you how much power your panels are generating - they don't tell you the overall state of charge of your battery - ie how full it is.

While driving, the display will tell you how much charge is going into the battery from the van engine. You can then work out how much driving you need to do before your battery is fully charged.

When on hookup, you can tell how much power your mains charger is delivering.

Power management in a van is important, especially if you spend a lot of time in the van, and more especially if you use quite a lot of power - using a laptop or watching TV are usually the main consumers of battery power. It is very useful to be able to tell at a glance how much power you have left, and also what you need to do in order to get power back into the battery - either from solar, engine or hookup. It is particularly useful with solar, because after a few weeks or months of use, you will get a feeling for just how much power you can expect from solar in any given weather situation. Solar gives you much less power in winter and it is very useful to know exactly how much you can expect from solar, and modify your plans accordingly.

Another great advantage of a battery monitor is that it enables you to avoid abusing your battery, which can shorten its life. Most people know that a lead acid battery should not be discharged below 12v, which is roughly half of its rated capacity. This means in theory that a 100ah battery should give you 50ah of usable power before it drops below 12v. In practice this is almost impossible know without a battery monitor. With an accurate battery monitor you can see the voltage and capacity of your battery on the display, and you can tell exactly how much power you have left. This enables you to make decisions about reducing your power usage to get the best out of what you have left, and ultimately, to switch everything off and go to bed. 

Once you get used to the information at your disposal you can then plan your activity accordingly. If you need to work on your computer for a few hours, or watch a movie tonight, you can tell at a glance whether you have enough power to do so. If it has been a cloudy weekend, wildcamping, and you want to stay put, then you will know how much battery you have left, and ration out the power - ie read a book instead of watch TV.

It may sound a bit daft, but 12v battery systems are not simple mechanical devices that are either on or off, with a fixed capacity. They have character! Battery systems perform differently according to conditions - how much charge, how fast, the temperature ... and they also change as they age. Only with a battery monitor can you get intimate with your battery!

So who would benefit most from a battery monitor? The simple answer is - anybody to who battery power is or has been an issue. If you have ever run out of power unexpectedly or wondered how much power you have left, then you will benefit. The only people who don't need a battery monitor are those who always have enough power for their activities, and never run out. Many people don't run TVs or laptops and only need power for lighting and reading. If you always use EHU then you don't - if you always wildcamp - you do!

Other options - more technical stuff that you can skip!

There is another way of measuring current that doesn't use a copper shunt. This involves using a sensor known as a "Hall effect" sensor, named after the man who discovered it. This works by sensing the magnetic field generated by DC current flowing in a wire. It is the same effect as used in those test multimeters you can buy known as "DC Clamp meters". A hall effect sensor works by having the negative cable passing through it.

These have only become available recently - mostly from China. I have used one, and found it to be very good, but slightly more temperamental than a copper shunt. They also have to be located carefully, as they are easily damaged by knocks etc - we want things to last for years not months.

Another recent development is that fixed displays can now be fed from the shunt by radio - which means no wiring. This makes installation easier. You may ask what is the difference between this and a Bluetooth shunt? Good question - the answer is not much - one used a dedicated display but with no wires - the other is a phone app.

A typical Hall sensor - the negative wire goes through the hole

So what should you buy?

Here is a list of the battery management systems that I know about

Victron - Victron now do a SmartShunt - a snazzy bluetooth shunt that drives their phone app - it is reasonably priced. 

Victron SmartShunt and the App

If you want a dedicated display, then Victron do several - they are called the BMV battery monitors, and there are several in the range.

Victron BMV - you get the full kit with Victron

NASA - NASA is a manufacturer of yacht instruments - not space rockets - and they have produced a very reliable and quality shunt/display BM for years - I have used one myself for 5 years and it is still going strong. They produce the BM1 and the BM1 Compact - the compact has a smaller display.

Nasa BM1, BM1 Compact, and the NASA shunt

NASA have also just brought out a Bluetooth shunt and app.

The new NASA Bluetooth unit

BMPRO - BMPRO are an Australian outfit that produce quality gear - and their latest product is called the Batterycheck. This is a very simple design that blots directly to the battery, and displays on a phone app. They also have some other really fab products, and I believe they are just starting to get UK distribution.

Lovely product ... just bolt one side to the battery, and everything else to the other side! Google "BMPRO" for their other stuff.

China - China has a bewildering array of products available. The reason for this is that BMs are not just for motorhomes. They are used in electric bikes and electric vehicles and in off grid power setups - the principles are all the same - counting amps and calculating capacities. These are available on Ebay, Amazon and Ali Express. I can't possibly review them all. Some use shunts, some use Hall effect sensors. Most cost between $20 and $50 - that's US dollars. Anything cheaper will be no good. The problem is the specifications - the english is always bad. You want something that has a shunt, is for measuring DC and looks like these pictures here. If in doubt get in touch with me. Not all these products are crap - if money is tight, then no reason why not. At these prices you can just play! Most are unbranded, but Juntek seems to have a decent reputation.

Here is a selection of Chinese products - these are the main ones - my personal favourite, which I have used, is the bottom one, often labelled Juntek - available in several versions - including copper shunt, Hall effect sensor, hard wired, non wired (radio).

Finally - a note about Lithium. Lithium batteries are not like normal lead acid batteries. A lithium battery ALWAYS has an electronic battery management system, also called a BM or a BMS. Do not get these confused with what I am talking about here. This article is about BM systems for lead acid batteries.

If you want more information on this subject message me, or contact me on "Classic Hymers Technical" Facebook group.