Unimog Camper under construction


Lain, I had to look back a little in your thread. So if I understand correctly your truck is 12 Volt. What alternators are on the truck. The F on the alternator for field does not have to mean that it actually senses the battery voltage thru it. It could be that it just provides the power to the regulator in case the alternator does not have field diodes. So an actual alternator number is required to look that all up.
Internal regulator are a little hard to modify since they are an integrated chip like many Bosch style or potted with sand and glue?..

I would think that you can program your victron BMV 712 to turn on the relay when a certain temperature is detected and with that relay switch of the F connection on you alternator. The temp sensor should be on the alternator.

Another solution would be a hall effect current sensor on your alternator output so that you can monitor the produced current .. fleabay..
WCS1800 Hall Current Sensor 70A Short Circuit Overcurrent Aegis Module

so if you go over the 70 Amp you turn off the voltage regulator... This is a rather crude solution that turns the alternator off at a certain current set point ( 70A). Then on again. you would need a relay that would wear out quickly because of the fast on off switching but would prove the concept. The voltage regulation part is taken care of by the VR. At least it can provide a good indication what current your alternator is delivering to the battery.

If you are up to experimenting.. read .. risk taking... then you could have the above over current device switch off the field directly by interupting the wire to the field brush after the voltage regulator. instead of a relay use a semiconductor to increase the switch frequency.

Maybe the most elegant method, within the cheap solution group, would be to program the BMV for the voltage you want the batteries to be and turn the output relay off when your are going over that setpoint.. eliminate the alternator VR and replace with a current regulator.
So now you alternator has become a current source and the BMV is the voltage regulator.

regarding one or two alternators .... you have to estimate your Ah usage versus engine run time to determin what current you need at a minimum to keep you batteries full.

Sorry this got somewhat lengthy and I do not know your electronic background.. so proceed at your own risk.


I have just done 45minutes of testing, easiest just to list all the tests and what the result was. I had an Auber temperature sensor on the OEM Bosch 90A alternator and used a IR heat gun on the 120A alternator measuring on the coil itself. (the brown/black bit on the picture)


I also had a clamp on meter on the 120A alternator output. The battery monitor measures the the combined input into both sets of batteries, so the output of the 90A alternator would be the difference between the total measured on the BMV712 and the clamp on meter less the normal current ( 10A) to run the truck. Inside the shed, the ambient temperature was 23C and got up to 25C after running the truck. I have been discharging the batteries for the past week, guessing they would be down to about 60-70%. They were were all down to 13.2V

1. Idle test - I started the truck and just let it idle - about 700rpm. alternators charging batteries independently
2. Truck at 1200rpm - charging batteries independently - minimal extra load
3. Truck at 1200rpm - charging both batteries in parallel - minimal extra load
4. Truck at 1800rpm - charging both batteries in parallel
5. Truck at 1800rpm - charging batteries independently - maximum load ( all spot/headlights, ,main engine fan, ac etc.)
6. Truck at 1800rpm - charging both batteries in parallel - maximum load ( all spot/headlights, ,main engine fan, ac etc.)
7. Truck at 2000rpm - charging both batteries in parallel - maximum load ( all spot/headlights, ,main engine fan, ac etc.}

On the first test, at idle the voltage jumped to 13.7V and current up to 20A. The 90A rose from 20C and stabilised at 40C after about five minutes. The 120A alternator got to a stable temp of 65C. The 120A alternator was putting out 20A, so that means only 10A was going into the main batteries, so the 90A was only putting 10A into the starter battery. This was the test the the video showed would blow up the alternator, and nothing of the sort happened. Temperatures on the alternator did not rise at all. If I lowered the idle down to less than 700rpm, the current going into both batteries dropped down to zero.

Second and third tests, the total input into the batteries was 90A and it did not make any difference being in parallel or independent. The real change was was in the output of the 120A alternator. When run in parallel with the 90A, it was putting out 60A, so that means the 90A alternator was putting out 40A. The temperatures on the 120A alternator stayed at 65C. When run independently, the 120 alternator output rose to 85A, so than means the 90A was only putting out 15A into the starting battery, which has rose to 13.85V whilst the main batteries remained at 13.7V. The temperature on the 120A alternator rose over about a minute to 95C and stabilised.

Test 4 showed no real change other than the total output going to 120A, and in parallel mode, the 120A alternator temperature dropped down to 85C and stabilsed.

Turning on all the electrical load - this is about 120A in total, and with both alternators in parallel, the current going into the batteries dropped down to 50A. The output on the 120A alternator rose to 100A, and the temperature rose up to 110C and stabilised. The battery voltage dropped down to 13.6V. The 90A alternator went up to 55C. This temp measurement was on the casing, so I checked the difference between the casing and the coil on the 120A alternator, than the casing was at 75C. So I am guessing this meant the coils on the the 90A would be around 100C. So that means the total output of both alternators was 170A, of which the 90A alternator started to take up the load of charging the batteries. I kept this test running for ten minutes, and it stayed constant.

Running the two alternators independently with maximum load, saw the output of 120A alternator go up to 110A, the temperature on the coil increased to 115C quickly then stabilise. The total input into the batteries dropped down to 20A. Voltage on the main battery was 13.6V, and increased to 13.8V on the starter battery. So, I think that means the main batteries were discharging by 10A, and the starter battery was getting charge of around 30A. I carried on this test for 10 minutes as well. Switching off the main engine fan (25A) load saw the BMV current change by the same amount.

I increased the revs to 2000rpm, and it made no difference to anything to any of the above, so I think that the alternators are running at their maximum capacity.

So, my conclusions are the if I run both alternator in parallel, then I will have no problems at all, and during the day, I will be charging the main batteries and starter at a rate of around 120A ( about 30A each) and around 13.8V. I will need to do a long run to see what will happen when the batteries get full, but I am thinking that since the alternators only put out 14.2V, I doubt that will happen. The solar system is set to no more than 14.5V, so even with that, I will never trigger the built in BMS shutdown of 15V on any of the batteries, but it also mean that I will not be charging the batteries to this full capacity, which might not be a bad thing.

So now I have to decide whether I really need to get a bigger alternator, of just used the built in feature of the Blue Sea Systems ML-ACR so that it will automatically run the two systems in parallel after about 3-5 minutes after starting and always run both alternators in parallel. I can get a 270A alternator from Mechman for around $800, so will probably get it.


One thing I might invest in is something like this to protect the alternators. https://sterling-power.com/products/alternator-open-circuit-protection-device and maybe I should look at getting a smaller pulley for the 120A to increase it efficiency at lower rpm, but to be honest, I hardly ever leave the truck idling, and even in off road conditions, we seldom trundle along at less then 1500rpm. The big LED spotlights on the roof draw 10A each, but we only used all of them when on dark dirt roads, I normally just have one pair on as that is more than adequate. The inner pair of spotlights are set to light up the sides of the road more than in front anyway,

The next test will need to be done on the road, and when there is a high ambient temperature over 40C to see if everything does work reliably. I think I will move the temperature sensor to the 120A alternator and epoxy it directly to the brown bit on the 120A alternator coil, as that is what seems to get the hottest. I could wire in the Auber gauge on the dash so that it would automatically make run both alternators in parallel if it got hot.

All in all, I don't seem to be having any problems at all with this new setup, time will tell I guess.
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I'm wondering how the Kalori Silencio 2 are doing ? Do you feel the need of 2 of them ?
I've spec 2 of them in my 19 foot box (2 inch FRP insulated) and wondering if it's overkill. Looking to switch to a Kalori Siliencio I or another radiator with 24V fan. The end goal is to control the fan with PWM so I might replace the fans on the kalori unit.


I'm wondering how the Kalori Silencio 2 are doing ? Do you feel the need of 2 of them ?
I've spec 2 of them in my 19 foot box (2 inch FRP insulated) and wondering if it's overkill. Looking to switch to a Kalori Siliencio I or another radiator with 24V fan. The end goal is to control the fan with PWM so I might replace the fans on the kalori unit.
For where we live, having two of the Kalori S2s is overkill, we can heat up the camper in a few minutes with the fans on high. We have stacked another layer of fans ( three only as I used the fourth for our fridge vent :) ) on the back of the original Kalori fans, almost silent computer fans that give just a gentle breeze compared to the massive amount of air the Kalori fans can move. We are drawing in outside air for the Kalori fans, so that does make a difference rather than recirculating the air, and we also tend to have the roof hatches in their semi-closed position which allows of airflow which I think is a necessity. We have never had any condensation problems.

2020-12-15 11.23.24.jpg

I worked out a long time ago that we needed about 5kW to heat the camper to 20C with an outside temp of -30C ( if we insulated the front windscreen and windows), and one Kalori S2 doesn quite cut it . We have the 9.3kW Webasto version, so plenty to spare which goes into the engine block as well, we also heat the hot water system, and the rear compartment with the watertanks in it. I was also considering having a loop in the battery compartment as well, to keep the LiFePo4 batteries warm if we ever get to a really cold place, but a heat pad seemed easier.

I also have a fan providing positive pressure into the two rear storage pods at the back of the truck, which will keep the batteries there warm as as well.

2020-12-15 11.24.02.jpg

I used the space around the water heater tank to store spare hoses, fanbelts, brakes lines and turbo oil lines and anything long and skinny.
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Whilst I am here, might as well update some other things I've done to the truck.

First off - here is the 250A Mechman alternator ( I have a 12V truck so everything is easy). I need to get a smaller pulley made for it, as at idle ( 700-rpm) it does not charge much, but over 1500rpm, it puts out the around +200A, so it will work for now. At +200A, it does not run hotter than the old one did (80-90C), and Mechman say they one I have is good for more than +120C. The pulley that came with it doesn't have the same spacing as the a/c compressor next to it. Like the old one, I run a dual belt pulley, and doesn't squeal at all. I tried it with the Mechman pulley that came with it, and the belt got pretty hot, and you can see the wear. Switching to this pulley and all is good.

2020-11-17 08.40.22.jpg

The new alternator is a basically a bolt in replacement for the generic Bosch 120A one, but getting the right regulator proved to be difficult. I told Mechman to make sure the voltage did not get over 14.5V, so to protect the LiPoFe4 batteries. When I tested it, it ran at 14.9V - too high as it is pretty close to the 15.0V when the BMS will cut out the batteries.

I got them to send me a 14.5V regulator, which turned out to be a dud, so I bought one locally, a 14.5V one from a Honda. That one was cheap, only $40, so I bought a spare for just in case.

2020-11-17 08.39.57.jpg

The other thing I fitted is some new Ironman Foam shocks, they are significantly bigger than the Koni shocks, and quite a lot sitffer. They have transformed the truck, no long does it wobble like an old Range Rover. The truck still leans going around roundabout, but it does so slowly.

2020-11-17 08.39.19.jpg

The shocks are phyically much bigger, so much so that they don't fit with the plastic covers on the front of the U1250 - but they do on a U1300. Ironman supplied some rubber boots for to replace the cover, bit of mission to get them on but they fit OK.

2020-11-17 08.38.43.jpg
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Hello Ian, congrats for your nuclear plant... You can sale the extra energy, jeje, nice shocks, I think the koni you use were the std no? The hellget ones work I bit better on the MOG, but in any case is good to know about other brands and options, I will follow your comments about your new ones, I think even this year will be not possible to visit Phillip Island by the situation...


Correct, the Konis were the standard ones for a U1250. I saw the Hellgeth ones, they have the same problem on a U1250 - need to take of the upper shield and replace it with a rubber boot. The Ironman ones are even bigger than the Hellgeth Konis. The best thing was the cost of all four as about half the cost of a pair of Konis over here.

Might be a while before Australia lets people in given the current state of the Covid in the rest of the world.


Be aware that some alternators will adjust the voltage upward when temps go down..
To faster recharge when cold but also lead acid batteries voltage is temperature dependent.

Iain, what are the extended and compressed dimensions of the Ironman shocks, eye-to-eye? Do they take a 20mm bolt? My stock shocks are roughly 444mm-719mm.


Iain, what are the extended and compressed dimensions of the Ironman shocks, eye-to-eye? Do they take a 20mm bolt? My stock shocks are roughly 444mm-719mm.
HI Charlie, these might be a bit better for your truck, the bigger ones - 755mm extended length


I got the ones for the U1300 - 710mm extended length.

They both take the 20mm bolt.


Be aware that some alternators will adjust the voltage upward when temps go down..
To faster recharge when cold but also lead acid batteries voltage is temperature dependent.

Thanks Johan, I doubt the simple regulator I have will be that sophisticated, just a standard old fashion 14.5V regulator. I could have chosen a 14.2V or a 14.4V as well. Pretty common style regulator, found on Toyotas, Hondas etc.



There was another thread about tyre inflation systems and I thought I should share my system that I built then took off and why.

I had four coil connector hoses like these.

Coil hose.jpg

The connector to the tyres was a screw on fitting. I tested it all out a few times and to be honest, found the difficult part was screwing the connector onto the valve, especially when the wheels are muddy or I've been on the beach.

I have the a manifold to connect both tyres on the axle together, and Jamec Pem automatic tyre inflator (https://www.jamecpem.com/collections/tyre-inflators/products/auto1000-digital-auto-inflator), which connected to the trucks air system. All I had to do was turn on the isolation valve, power up the inflator and it do the rest.


The biggest problem is the Schrader valve on the tyre, they limit the airflow a lot. They also tend to be fairly soft brass, so it is easy to damage the threads on it. It was a hassle to fit the coils back into the tubes, and in the end I decided to take it off and just put some air connectors on each side of the truck, so I can connect the tyre inflator onto each side. That way I can keep the automatic inflator stored away inside the truck along with the coil air hoses. I also found the clip on connector for the inflator much easier to use than the screw on connectors, but occasionally they would need to be refitted as they would sometimes leak. The air connectors need some protection from dirt under the truck, so I use some rubber feet for chair legs.

Air connector with rubber dust cover.jpg

Each fitting has a valve so I can make sure there are no leaks.

Air Connector .jpg

This is the weak point in the system, the fittings are quite finicky to fit, and would sometimes leak a bit of fiddling to get it too seal.

valve connector.jpg

For lowering the pressure, I decided to go back to more manual systems, I already have two sets of these Staun Automatic Tyre Deflators, https://stauntyredeflators.com.au/ I have set each pair for 15 PSI, 20PSI, 25PSI and 30PSI. That way I can just put them onto the tyres and get back in the truck and wait till they stop deflating. They are pretty easy to use, just set and forget.

Whilst they are pretty slow at dropping the pressure in the big 365/80R20s tyes, all four are getting done at the same time and they automatically stop when they are at the right pressure. We run the rear tyres about 5PSI higher than the front tyres. They are not 100% accurate, so 15PSI might give about 0.5PSI different, usually on the high side I've found but not worth worrying about.

These are the front tyres at 15PSI, for the soft sand on our favourite beach.


This is 20PSI, for the more serious off-road or hard sand


This is 25 PSI - when the corrugations get bad


I also have an ARB tyre deflator https://www.sevenslot.com.au/product/arb-tyre-deflator/ if I want to be more accurate, this is really quick to deflate the truck tyres, as you screw the inside of the valve out. It works great but is a bit more effort to use as you have to keep checking the gauge.

So this is what we carry around now.

Air system.jpg

We have spent a fair bit of time driving on soft sand beaches, and found that it is best to go with lower tyre pressure, it puts less strain on the truck than trying to keep the pressure high so you don't have to pump them back up later.



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Holy crap Iain!! I just came across this thread. That is one hell of a rig you fabricated. I did not have to go through all 50 pages to see this is a serious vehicle that gets used for its intended purpose. If not well beyond it!!

I think it's important to note that most everyone here in the United States has no clue as to the capability of a rig like yours. Almost all monster builds that are similar to yours here in the US do not see much more than a smooth 2 track or local coffee shop.

Thank you for sharing and giving me some good ideas for my daily driver "baby build" (1/2 ton truck/motorcycle camp hauler).


Thanks, it took a long time to build it, and we make sure we use it for what it was intended. We prefer going to places where there are no people, main reason for building the truck. Our travels were limited last year, so hoping to get away more this year. This is our map of where we have been with our truck and our Land Rover.

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