Simple electrical system for expedition vehicles

[whatcharterboat]

Regarding this post, I know there is a dedicated forum for power systems, but this is something that really only applies to larger “Expedition” style vehicles and I would particularly like to get some constructive criticism/feedback from this community as you are the guys that are living with independent power everyday and are best to comment on the feasibility of this system.

These clients, although not intending to RTW at this stage, have sold up and are planning to call this truck their home for many years to come. They have just returned from a successful Simpson Desert trial (claiming they did over a 1000k’s in low range) and are hoping to head off permanently in the near future (hoping for some “sand dune crossing” pics soon).

The Powermaker from www.watts2c.com.au was mentioned before and this was really the key component of the electrical system. It is not an AC generator as such, but puts out 2.5kw @ 24VDC to maintain charge in the battery bank and is used in conjunction with an inverter to make AC power. The software that controls it can be set to a wide range of parameters however this one was programmed not to start between 21.00hrs and 06.00 hrs; start up whenever a 40A draw was seen; start whenever a preset state of discharge is reached; run for at least 20 minutes after being started and start at least every 2 weeks to keep oil splashed around and exercise the engine regardless.

There is obviously a remote control panel with an LCD display that shows full battery monitoring, temperature and oil pressure and lets you know when a service is due. All the electronics were sealed to a military standard and plugged for ease of removal. The engine is a small air-cooled Yanmar (so worldwide dealer network) with a lot of custom features such as a very clever rubber mounting system, comparatively quiet, light & compact, extra oil capacity (up to 500 hr service intervals is an option), a sump drain pump, 0.6litres/hr of diesel sucked direct from the truck’s fuel tank and importantly an emergency pull start.

One of the main benefits was that we were able to get away with only one battery bank that supplies both the house and the truck (and start the Powermaker too). That’s right. No auxiliary battery bank. Weight is always an issue and batteries are heavy so we went for only 2x180Ah AGMs to give 180Ah @ 24VDC. Isuzu have a tiny standard battery bank compared to a Fuso and so this turned out much better for starting the truck as well. Maybe 2x260Ah may have been optimal but that would have only meant that the Powermaker would have to run for slightly less time. You can imagine how simplified the electrical system then became. The other plus we realized was that should the truck’s alternator fail the Powermaker would sense the load, kick in and take its place.

This truck runs a domestic split Air/Con of about 3kw of cooling capacity, a bread oven and a small Microwave oven all through a typical 3kw inverter. However all of the DC loads were as efficient as possible: such as all LED lighting and we built our own 200litre fridge/freezer (50mm foam) into the galley bench. The Powermaker has to run when the Air/Con is on regardless. BTW we looked at a super efficient Air/Con unit designed to run on DC solar power (used to cool satellite communication repeaters) but the cost was way out of the ballpark and we would almost have needed two of them.

The whole thing was supplemented with 272watts of solar so that under normal camping conditions (without Air/Con) the Powermaker would hardly need to come on at all. Don’t know if you guys are familiar with these panels. Actually they are called PVL’s (PhotoVoltaic Laminates) Have been fitting them for 6 years now. They are all we fit for a number of reasons. Ask me if you’re interested. Also there was a 24v/50A 3stage charger to handle “shore power” if in a moment of total insanity you were staying in a trailer park or somewhere where you just couldn’t run the diesel Powermaker.

I am fairly certain that there is going to be a 6.5kw @ 24VDC unit (with its own integral 6.5kw inverter; based on a 2 cylinder water-cooled Kubota diesel) soon too. If that is the case we may even be able to incorporate the hot water system into it somehow. We were also told to expect a slightly cheaper12VDC unit shortly. The guy behind the Powermaker still designs similar units for military and mining applications so I’m sure it will be as good as it sounds. Luckily they are only 10k down the road from us but he tells me that he’s looking at exporting very shortly (for those in the States/Canada).

The clients specified that the whole system had to be as simple to operate and as trouble free as possible so this is what we came up with for this sized vehicle (close to 6ton).
Thanks in advance for any constructive criticism or positive feedback especially on the idea of a single battery bank. Sorry it was so long but I hope you found it interesting and a different perspective to the commonly accepted type of electrical system for an Expedition vehicle.

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[whatcharterboat]

The powermaker

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[whatcharterboat]

The powermaker

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[whatcharterboat]

the powermaker

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[whatcharterboat]

the powermaker

.http://im1.shutterfly.com/media/47b...WrVmzZMge3nwI/cC/f=0/ps=50/r=0/rx=480/ry=320/

 

[whatcharterboat]

The power maker

Next time we will probably mount it underneath to free this bin space up.

 

[Nuclear Redneck]

Very ineresting system and an excellent writeup. Thanks for posting it.

As I understand it there are three different ways of generating electricity:

1) Truck's alternator
2) Powermaker
3) Solar panels

Seems to me that you have plenty of redundancy. A few points to ponder:

1) How is the system setup to operate if one component (i.e. generator) fails?
2) How are the loads set up? Is there a set way that loads are stripped in case of reduced capacity.
3) If there is greater than a 40 Amp draw between the hours of 2100 and 0600 will the generator kick on?
4) Other than the Air Con, what is the expected amperage/hour while in camp?
5) How long do you expect to operate without the generator running?


Cheers,

 

[Carlyle]

Great write up on the power system. How would you compare that system to the Outback converter/inverter that could much of the same things?

More info on the solar system please!

 

[dhackney]

John,

Thanks for posting this.

I hope to find the time to write up an "Electrical Systems for Expedition Vehicles" document at some point. There is a lot more work there than the propane/LP/LPG/GLP system, so I've been consciously putting it off. Plus, all of my reference books are back in the storage locker in the U.S. Perhaps when we're back there for the holidays I'll give it some energy, no pun intended.

For those interested in designing the electrical system for an overland expedition vehicle, do a search for marine electrical system design and maintenance books. If you have a local West Marine or marine books store you can peruse the titles yourself. My favorite marine bookstore is Seabreeze in San Diego http://www.seabreezenauticalbooks.com/ You can ignore most of the electrolysis material in these titles, but otherwise will be able to directly apply everything in the sample designs.

Once you have a design, have it reviewed by a qualified marine electrical system consultant. I used Brett Dingerson from Marine Electric. http://www.marineelectric.us

I wish the 24VDC genset John illustrates would have been available when we were designing and building. A comparable system is available in the U.S. from here http://www.watermakerstore.com/Generators/Generators2.html These are targeted towards the marine market but are available for land vehicle installations. You can use a Xantrex genset controller to duplicate the functions outlined in John's sample system related to hours of operation, load sense start, etc.

I agree completely with John's total 24VDC approach. It was my goal to have a 12/24VDC boat and also to have a 12VDC expedition vehicle. Unfortunately, my search for appropriate 12VDC air con did not yield any results that I could utilize in my time frame.

Thus, we ended up with a 120VAC air con and a 120VAC 30 amp genset. As a marine electrical system designer I consulted with on the project pointed out, charging a 12/24VDC battery with 120VAC power is very inefficient.

So, from the overall design standpoint, I encourage anyone considering designing an electrical system to stay with 12/24VDC if at all possible. The only things that can push you into 120/220VAC is a very large air con requirement or any other large current, typically inductive, load.

Electricity works on a law of watts divided by volts equals amps. High amp loads require thick, heavy wire. Thus, if you design around 24VDC and 220VAC all of your wiring can be of a smaller gauge, thus lighter. This is the reason that high amp devices on boats, such as winches, use 24VDC motors rather than 12VDC. Their wiring can be smaller for those devices, thus saving weight.

Also, in terms of wire sizing, use a computer utility such as Wiresizer http://www.midcoast.com/~aft/index2.html You will note in using the program that for 12/24VDC circuits voltage drops significantly with circuit length. If you use a simple rule of "lighting requires 18 gauge" you will design a poorly performing and potentially dangerous electrical system. Calculate the gauge required and use that gauge or larger.

Note that resistive loads such as electric tea kettles/coffee pots, toasters, etc. do not care about frequency, or, to a certain extent, voltage. This means you potentially have a lot more flexibility powering resistive loads. Also note that resistive loads are typically the highest amperage draw devices in your system aside from air con. If you can use a higher voltage resistive device your wire size and resulting weight will be much lower. To get an idea of the impact on weight calculate the required wire size for a 20 amp load at 220VAC and at 12VDC.

Devices such as computers, camera battery chargers, etc. typically have a 12/24VDC power supply option. It is much more efficient to run those devices from native 12/24VDC power rather than at 120/220VAC from the inverter, which suffers effeciency losses converting 12/24VDC to 120/220VAC.

Devices such as microwaves, televisions, DVD players, networking components, data storage arrays, etc. require a pure sine wave for their AC power. If you have any of these components in your system you must purchase a pure sine wave inverter. They are worth the price. Keep in mind that you may want or need to add one of these devices later. If you have a square wave or modified sine wave inverter you will not be able to do so.

One thing to watch for when you select your inverter/charger is acceptable frequency range from shore power (local grid 120/220VAC). An inverter/charger that can accept both 120/220 volts and 50 or 60 Hz will give you true worldwide flexibility. If your inverter/charger is limited to 60 Hz you will not be able to use local power in much of the world even if you use a transformer to drop it down from 220VAC to 120VAC. >> A transformer does not affect the frequency (Hertz / Hz) of the AC, only the voltage <<.

In our experience living in an expedition vehicle for a year it is essential to have at least two ways to accomplish all major tasks, including:

• Heating the camper
• Common cooking tasks, e.g. tea/coffee water
• Running the refrigerator, e.g. LPG, 12/24VDC, 120/220VAC
• General cooking, e.g. cooktop/range using gas, microwave using electricity
• Charging the batteries

There absolutely will be system failures, both short term and longer term. It is critical to have redundancy. Consequently, in John's sample system, I would add another way to charge the batteries such as a dedicated alternator on the motor.

I would also add a multi range (120/240V 50/60Hz) battery charger for use when local grid AC is available. You will spend time in urban areas and campgrounds. Your neighbors DO NOT want to hear your genset running, even a small and quiet one such as in John's example.

For those building in the U.S. it is essential to add a 220V 50/60Hz battery charger to your system. Once you leave the U.S., almost the entire rest of the world is 220V/50Hz. You must have a way to charge your batteries other than running the genset or the chassis motor and it is unlikely that you will be able to depend on solar panels due to variable sunlight.

Also, because of my belt and suspenders nature, I would definitely have two separate battery banks: engine start bank and house bank. IMO it is worth the weight, especially if you mount the house bank in between the frame rails to keep the weight low and centered. I cannot imagine doing an ocean passage in a boat without two banks and I would not want to be out here without the ability to switch over to the second bank to start the motor if required.

In addition, engine start batteries are designed to deliver high amperage loads for short durations of time. House bank, deep cycle, batteries are designed to deliver low amperage loads for long durations of time. I am not convinced you can do both jobs effectively, especially starting a motor in very low temperatures, with one type of battery in one bank. If you use high cranking amp rated batteries then their cycle characteristics will be miserable. If you use deep cycle batteries then their cold cranking amp ratings will be dismal. Note that all batteries in a bank must be of the same type and should be of the same capacity. Due to this factor alone I would definately insist on two battery banks using appropriately designed batteries suited for their intended purpose for an expedition vehicle.

Battery house bank capacity is calculated by:
1. average daily use
2. subtract system inefficiency loss, e.g. batteries don't fully recharge, voltage/amperage loss in distribution, inverter loss, etc.
3. multiply by at least 2.0

The reason you multiply your net expected daily amp hours by at least 2.0 is that in actual use you can only draw down deep cycle batteries to 50% of capacity before recharging on a regular basis. If you draw them down to a lower level than that you will dramatically shorten their lifespan.

A Microsoft Excel spreadsheet I used to estimate our amp hour needs while designing our system is here: http://www.hackneys.com/mitsu/files/amphours.xls

We have over 800 amp hours of house bank capacity and it is the minimum for us. Admittedly, we use a lot of electrons, probably more than most overlanders other than those in the giant uber Austrian rigs. If you are accustomed to a lifestyle heavy in electronics, Internet access, digital photography, digital video, etc. no amount of LED lighting will save you from yourself. You will need a lot of amp hour capacity.

In terms of materials and components there is no substitute for marine quality components. They downside is they will be dreadfully expensive. The rule of thumb is a Coke is $1, a marine Coke is $5 and an aviation Coke is $25. The upside is they will be made to function in the most corrosive and challenging electrical environment in the world: a bath of salt water.

Major electrical system components that should be marine grade:

• Wire / cable (this will be unbelievably expensive, be sitting down when pricing)
• Breaker / control panels
• Instruments / meters
• Switches
• Crimp connectors (use adhesive lined shrink crimps)
• Inverter
• Isolation transformers
• Battery bank switches
• House bank alternators
• Solar panels and controllers
• Batteries (AGM)

An important safety factor for those building in North America is wire colors. The standard for 120VAC wiring is green = ground, black = hot, white = neutral. The typical standard for 220VAC is green = ground, black = hot, red = hot, white = neutral. The automotive standard for 12VDC is black = ground and red, or just about any other color = hot. Expedition vehicles combine 120/220VAC and 12VDC circuits in the same vehicle, often in the same wire chase/run. If you normally work on 12VDC systems and see a black wire you will assume it is a 12VDC ground. It can very easily be a 120VAC hot and kill you. For this reason, the North American marine industry standardized on yellow as 12VDC ground. When you buy your wiring, select yellow for all 12VDC ground circuits. In addition, clearly color code all 120VAC circuits with a unique color of electrical tape that is not used for any other purpose. Wrap 8 to 12" sections of the circuit with the colored electrical tape. Wrapping the circuits with labels clearly identifying the high voltage is a very good idea. Do not assume that you will remember or that anyone else working on the vehicle will know what the voltage of different circuits is. Don't take shortcuts and don't fail to clearly label and color code all high voltage circuits.

Can you tell which circuits might kill you in this wire chase?

In summary:

• Modern overlanders are heavy users of electricity. They typically require large electrical system capacities. They also expect things to work at the flip of a switch, so reliability is important.
• Redundancy is an absolute requirement in the reality of overlanding. There will be short and longer term system failures and downtimes.
• There is no substitute for quality components and careful assembly.
• The most efficient electrical system design is one that uses 12/24VDC for all components except the inverter/charger and specific 120/220VAC devices. This implies the use of a 12/24VDC genset, which will be much more efficient than a 120/220VAC genset and associated charger.
• Design and build for varying electrical standards and environments. You will not always be in a place where your solar panels provide energy. You will not always be in a place with 220V/50Hz local grid power. You will not always be in a place where you can run a genset or chassis motor to charge batteries.
• Design and build for reliability. Use stranded wire. Use quality marine grade components. Assemble with care and professionalism. Use anti-corrosion grease, liquid or spray on all connectors in all locations. Pay special attention to ground connections. Include service loops in all connections. Securely mount, tie off and isolate all wire runs.
• Design and build for ease of maintenance and troubleshooting. Document everything, especially the things you are convinced you will never forget. Use labels and fine point permanent markers to label every wire of every circuit. Mount all components on studs for ease of removal. Label all circuit breakers and fuses. Ensure you have spare fuses for all circuits and all devices, e.g. low amperage glass tube fuses for devices. Bring simple circuit testers (12/24VDC and 120/220VAC) and a full range volt/ohm meter that includes a continuity tester. Bring hard copies or PDF files of all component documentation. Take photos of all component data plates. Maintain a copy of all componenet manufacturer contact information. Keep your records and documentation in a central, organized place. Carry spares of key component typical replacement parts, circuit boards, etc. Bring spares of all connectors used in your system and a small amount of wire, especially unusual sizes.
• Design and build for safety. Purchase and install covers for all buss bars, fuse blocks, etc. Install fuses or circuit breakers in all circuits, especially high amperage DC. Use shrink wrap around all connectors. Double bond system grounds. Design and build a method for establishing an earth ground when connected to local power as you will almost never find a grounded local grid. Clearly label high voltage wiring by wrapping with colored electrical tape, e.g. orange for 120/220VAC. Clearly label all outlets with relevent voltage. This especially important for American builders who travel overseas. Clearly label and color code local grid outlets and distribution circuits.

Doug

 

[haven]

"Battery house bank capacity is calculated by:
1. average daily use
2. subtract system efficiency loss
3. multiply by at least 2.0"

I find a factor many people overlook is that the life of your battery is related to the typical depth of discharge in a daily cycle. A battery might last 1000 cycles if you discharge to 50% capacity, but only 300 cycles if you discharge down to 25% capacity. In other words, if you have a small battery capacity, you'll wear out your battery faster. And you may have trouble finding a replacement AGM sealed battery in a little town in Bolivia/Botswana/Burma.

Chip Haven

 

[1leglance]

wow
I have nothing to add but thanks for this high quality info..
wow

 

[whatcharterboat]

Wow. Thanks for the response.

So many questions. I hope I don't say the wrong thing. I got Don to check over this thread to make sure everything I wrote on the Powermaker was accurate before posting. We did this one over 6 months ago and it was written was from memory. If there is anything I can't answer specifically about the Powermaker I'll have to ask and get back. We aren't associated with them in anyway but I think it's a great thing and am happy to give it a plug. Also I see I made a mistake in the post and that is: the 3 stage charger we used, was a 25A not a 50A. Sorry.

I'll start with Chip and work back. Every thing you said is of course 100% accurate (what else would you expect) and coming up with a figure and doubling it is always a safe bet. I like your thinking.

The answer is that the Powermaker was told to start at a preset depth of discharge(DOD) of only about 40% (60% charged) so that the battery life is maximised. Different battery types can have different starting parameters. Don did the programming and I am guessing that was the setting. This is one of the best features of the unit. You can toss up between fuel costs and battery costs over the life of vehicle and decide the optimum. You can literally dial in the life of the batteries.

 

[whatcharterboat]

Doug

Doug. Pure gold. In 30 years of working with marine, aviation and RV electrics and studying renewable energy technology at college, that is some of the best advice on this subject that I've read. Well beyond the feedback I was expecting.

There absolutely will be system failures, both short term and longer term. It is critical to have redundancy. Consequently, in John's sample system, I would add another way to charge the batteries such as a dedicated alternator on the motor.

For a RTW vehicle I would have to agree. I suppose we are blessed here with an ideal country for solar and I sometimes take that for granted. For outback remote area power systems (RAPS) we use a very loose formula of 1 out of 10 days will be windy and 9 will be sunny. We have been in negotiations with a client who wants one of those big MAN dream machines and I have already suggested a fuelcell as a supplement to a similar system as this.

The fuel cell we can access is very compact (about the size of a small briefcase) and will supply up to 130amp/hours a day. The only downside is that it runs on methanol and I'm sure that's not easy to come accross RTW so you would have to carry a quantity of it with you. They recomend using theirs which comes in sealed containers so there is no decanting required. I know it's very toxic. Still if it it only going to be an emergency supplement I think it will be a good option. BTW these guys are trying to develop a diesel fuel cell but I don't know that they are having any success. Wouldn't that be good.

This is by far, the most "zombie-proof" unit I've found but of course if the unit did fail you would have to reduce your loads. Certainly no Air/con or large AC loads but the solar or the engine when travelling should be able to cope. I did also mention that the unit has an emergency pull start so that if the electronics did fail it could still be started manually.

It is the single battery bank I'm "out to lunch" on and why I was seeking feedback. Maybe the bank could have been split in half so that in the event of a battery failure you could drop half the bank out. The down side there is that more batteries to give the same capacity is less efficient.

Just so we are on the same page about 24V or 12V for those who did not know: the Fuso 12V and the Isuzu is 24V. I have a friend who teaches Auto Electrics (Doug, one of the guys on Tere in the pics). He tells me that some of the European truck builders have been loking at 48v systems in an attempt to reduce wire sizes and improve efficiencies. Haven't seen any evidence filter down yet though.

 

[ntsqd]

48 volt systems and possibly more are right around the corner. It's coming, and not just in medium and HD truck platforms, but also in car platforms. The move to take ALL of the parasitic losses (like A/C comp., H2O pump, etc.) off the prime mover is driving this. Why they aren't telling us to design ECT's for this voltage is a mystery to me.

 

[whatcharterboat]

Nuclear Redneck

I don't want to even ask where that name came from.

1) How is the system setup to operate if one component (i.e. generator) fails?
2) How are the loads set up? Is there a set way that loads are stripped in case of reduced capacity.

Maybe this has already been answered.

3) If there is greater than a 40 Amp draw between the hours of 2100 and 0600 will the generator kick on?

Not 100% sure. The only loads like that at the moment in this system are the AC loads which you have to conscientiously turn on so I suppose you would just override the timer at the control panel. No big deal. One button push.

4) Other than the Air Con, what is the expected amperage/hour while in camp?
5) How long do you expect to operate without the generator running?

I'm sure you will apreciate how many variables are in these questions. My brain is already starting to overload and smoke up. At this lattitude (expedition vehicles don't stay in one place but do they),you can safely expect about an average 5.5 Peak Sun Hours(PSH) a day so I quess the solar will put in close to 1500 watt/hrs/day (making 1200 available to take out) and maybe the daily DC loads are 3/4 of that (if you were being frugal). The System in good weather here could run indefinitely with out the generator kicking. The biggest DC load here is the fridge we built which runs a Danfoss compressor. So working on a cycle of 10 hrs/day (depending on the ambient temp) @ 2.4A @ 24Volts = 576watt/hrs/day.

Too many variables but hope this answers it. Good talking to ya.