OxfordMorgan Posted February 13, 2012 Share Posted February 13, 2012 Hi all, There have been various threads about the Eberspacher systems, but I wanted to hear from any people who have the combitronic system, and what their experiences are using it on 12V. I always knew it was a Hungry old Hector when it came to battery consumption, but having only really used it during Spring/Summer/Autumn, we have always been fine with a 100Ah battery and a large Solar panel whilst wild camping as we didn't really use heating, just hot water. Last time we were away I was doing some experiments to see how long we could last purely on battery, so set the Eberspacher thermostat to 16degrees during day and 11degrees overnight and was quite surprised to see it got through a 135Ah battery in about 24hours, and that was with very limited other electrical draw (No TV, Radio, Satellite etc.) The battery voltage had dropped to 11.9V but the system still wouldn't fire up - I thought they would still function at as little as 10.5V? It then consumed my second 100Ah battery in about 20hours.... When we first got the van, we had some problems with the water heater, and the dealer changed the electric wire to a greater thickness, so I dont think I am suffering from voltage drop (But I will check when I can work out where to stick the Multimeter at the heater end..there are quite a few wires..) So, is 24hrs a reasonable time to expect to run purely on 12V, or may something be wrong? Thanks Morgan Link to comment Share on other sites More sharing options...
DJP Posted February 13, 2012 Share Posted February 13, 2012 If you look here for specs http://www.eberspacher.com/downloads/technical-documents/combitronic_22297.pdf You will see that it draws between 2 amps and 7 amps depending on the fan setting. Taking your 100amp hour battery which has around 40 amps of usable power then 20 hours at the minimum of 2 amp is all you are going to get. We had a Truma blown air system and carried 4 x 110amp batteries due to the drain by the blower. Link to comment Share on other sites More sharing options...
Rayjsj Posted February 13, 2012 Share Posted February 13, 2012 Morgan, I have an Auitocruise Starlet II, which is just a 'Marquis' Starburst, with an Eberspacher Combitronic System, from my experience (limited, away from EHU). It shouldn't consume as much as that. I have managed 3 days, with a 'Standard' 110 amp battery, no solar panel. Although we did 'drive' the vehicle on the second day. I know that Richard (aka Tracker) also has a Starlet II and regularly uses his 'Stand alone', so his opinion would be more useful. We usually have an EHU if we are staying for more than 3 days. I will have to get my DVM 'hooked up' to the DC power consumption when the Heater/hot water is working and report back. Ray Link to comment Share on other sites More sharing options...
OxfordMorgan Posted February 13, 2012 Author Share Posted February 13, 2012 Thanks DJP, although pardoning my ignorance, why would I only get 40 amps of usable power? Link to comment Share on other sites More sharing options...
Guest Tracker Posted February 13, 2012 Share Posted February 13, 2012 A lot depends on how good your battery is and also how good the charging regime is at getting it fully recharged. When we only had one battery we used to leave home with the leisure battery having been overnight charged on the mains charger and then topped up by the alternator. We then just about got two days and nights out of a single 110 ah battery in winter before it died but that does of course include all the other things that one uses like lights, water pump (I'm thinking showers rather than kettle filling!) and TV as being the main ones. I added an alleged good second 110 ah battery but it only gave us an extra day and night but since taking an expensive plunge and buying two new Varta 110 ah batteries and a 60 watt solar panel we have yet to run out of power - it is not a fair comparison - but it has worked for us as we have yet to stay anywhere long enough to flatten the batteries - mind you we never stop anywhere for more than two or three days anyway but the voltage never drops below 12.4 ish. I would certainly consider having two leisure batteries as a must for any van with an Eberspacher as not only are they power hungry when running they take a huge kick of 12v power to ignite the boiler every time it fires up again after being off by thermostat. Link to comment Share on other sites More sharing options...
Brian Kirby Posted February 13, 2012 Share Posted February 13, 2012 OxfordMorgan - 2012-02-13 6:50 PM Thanks DJP, although pardoning my ignorance, why would I only get 40 amps of usable power? Because, as a general rule, it is recommended you do not discharge a battery below 60%, and I think the maths has gone a little haywire! :-) If a 100Ah battery, in good condition, you should expect no more than 60Ah from it. As it ages, the capacity available reduces, so you may only get 40Ah later in its life, but I think this was simply a case of inverted logic. However, in order to preserve the battery in good condition for as long as possible, it would be wise not to take it below 50% capacity on a regular basis, and it should ideally be fully re-charged more or less as soon as it reaches these levels. Driving for a bit, so it gets topped up but not fully re-charged, is almost as bad as leaving it discharged. Link to comment Share on other sites More sharing options...
OxfordMorgan Posted February 13, 2012 Author Share Posted February 13, 2012 Thanks Tracker, One of the things I was considering was another 135Ah to compliment my first, and a Sterling Battery to battery charger so I can run the engine for an hour or two if we are wild camping and try and charge them that way. Have you played with these Sterling units before? Link to comment Share on other sites More sharing options...
OxfordMorgan Posted February 13, 2012 Author Share Posted February 13, 2012 Thanks Brian. I was using it with a relatively new 135Ah battery which was at 13.8V when I plugged it in; which is why I was expecting a bit more than 24hrs. i was doing a worst case experiment, but I was surprised that the unti wasn't firing up after reaching 11.9V Link to comment Share on other sites More sharing options...
Derek Uzzell Posted February 14, 2012 Share Posted February 14, 2012 OxfordMorgan - 2012-02-13 7:38 PM Thanks Brian. I was using it with a relatively new 135Ah battery which was at 13.8V when I plugged it in; which is why I was expecting a bit more than 24hrs. i was doing a worst case experiment, but I was surprised that the unti wasn't firing up after reaching 11.9V Voltmeter readings for a good condition 12V battery (taken at the battery terminals and with the battery 'at rest') will vary from 12.7V-or-over (fully charged) down to 12.2V (25% charge state). A 12V-or-under reading indicates a fully discharged battery. So, if your 11.9V reading was genuine, it's hardly surprising your heater would not fire up. As you say, you really need to check the voltage reading at the heater end as, despite thick cabling, voltage drop can be significant if the battery is a long way from the heater. Link to comment Share on other sites More sharing options...
Brambles Posted February 14, 2012 Share Posted February 14, 2012 When the heater tries to start up it needs about 100 watts of power for just over a minute ( Tracker can correct me if longer). This will pull a battery with only 11.9 volts state of charge way down below 10.5v which is the cutoff voltage for the heater which is 10.5 volts with a 20 second delay ( its all in the manual). Taking your battery voltage down below 12.2 volts is NOT a good idea as will wreck it very quickly and reduce its life/capacity, so worst case experimenting comes at a price of reduced battery life. Link to comment Share on other sites More sharing options...
Guest Tracker Posted February 14, 2012 Share Posted February 14, 2012 Brambles - 2012-02-14 10:15 AM When the heater tries to start up it needs about 100 watts of power for just over a minute ( Tracker can correct me if longer). This will pull a battery with only 11.9 volts state of charge way down below 10.5v which is the cutoff voltage for the heater which is 10.5 volts with a 20 second delay ( its all in the manual). Taking your battery voltage down below 12.2 volts is NOT a good idea as will wreck it very quickly and reduce its life/capacity, so worst case experimenting comes at a price of reduced battery life. 100 watts (over 8 amps) is what the book says Jon, but according to a service engineer I spoke to they often take a lot more than that on the initial few seconds hit - up to 16 amps for 5 / 10 seconds he reckoned and then 7 / 9 amps for a minute or so before settling down to 1 to 3 amps continuous as long as the fan is running. No small wonder they knock seven bells out of a battery and if the battery is already low or tired it does not take many hits like that to defeat it. That is purely a non technical theory I hasten to add! Link to comment Share on other sites More sharing options...
spospe Posted February 14, 2012 Share Posted February 14, 2012 OxfordMorgan - 2012-02-13 7:32 PM Thanks Tracker, One of the things I was considering was another 135Ah to compliment my first, and a Sterling Battery to battery charger so I can run the engine for an hour or two if we are wild camping and try and charge them that way. There may be a bit of misunderstanding here. The Stirling Battery to Battery unit is to allow excess capacity form the leisure battery to top-up the starter battery, not the other way round. Running the engine will charge both the starter and the leisure batteries wheather you have a Stirling unit or not. Link to comment Share on other sites More sharing options...
Brambles Posted February 14, 2012 Share Posted February 14, 2012 I suspect Morgan meant alternator to battery charger. May not realise that is what he meant but am sure it is. Tracker, probably correct, most heater element will draw a lot more current when cold ( just like a light bulb) until the filiment is warmed up, so would not surpise me at all if the current is a lot higher initially. I did make a long detailed post about alternator to battery charging units but not sure how accurate it was so have deleted. Maybe try and come back to it later when I have checked the Sterling specs. Link to comment Share on other sites More sharing options...
Guest 1footinthegrave Posted February 14, 2012 Share Posted February 14, 2012 Perhaps the issue here is that these units were I believe originally designed with commercial vehicles in mind that took power and a charge directly from the alternator from the vehicles battery,and in a commercial situation had plenty of battery power capacity, perhaps that's why we always found when we had one on another van the batteries simply could not cope unless on a mains hook up every other day. We have also come to learn that simply driving say 50 -100 miles does not allow our leisure batteries to always be fully charged after using our Truma blow heating for any length of time either, what a bloody pain all this is, a convector gas heater with a blow facility if needed is by far the best option, and yet is so rarely fitted, another case of ill thought out design for real world usage methinks. >:-( Link to comment Share on other sites More sharing options...
Guest Tracker Posted February 14, 2012 Share Posted February 14, 2012 1footinthegrave - 2012-02-14 5:07 PM We have also come to learn that simply driving say 50 -100 miles does not allow our leisure batteries to always be fully charged after using our Truma blow heating for any length of time either, what a bloody pain all this is, a convector gas heater with a blow facility if needed is by far the best option, and yet is so rarely fitted, another case of ill thought out design for real world usage methinks. >:-( The alternator is only allowed by the electronics and by the narrow cable used to charge the leisure batteries at a maximum of about (10 amps for one hour = 10 ah) and on that very rough rule of thumb basis a 110 ah battery that is halfway towards flat will need a good 5 hour run to refill it. It's technically not quite as simple as that as Brambles will no doubt tell me shortly - but in non techy terms that about sums it up as I understand it! Link to comment Share on other sites More sharing options...
Guest 1footinthegrave Posted February 14, 2012 Share Posted February 14, 2012 I wonder in that case if it would be possible to connect some heavy duty cables to the engine battery with an isolator switch to prevent starter motor usage directly to the leasure batteries to fool the alternator to giving a full charge to the leisure batteries, and forget a split charge relay as this seems to be the limiting factor in the amount of charge while driving ,or is there something I'm missing ? Link to comment Share on other sites More sharing options...
Guest Tracker Posted February 14, 2012 Share Posted February 14, 2012 1footinthegrave - 2012-02-14 5:40 PM I wonder in that case if it would be possible to connect some heavy duty cables to the engine battery with an isolator switch to prevent starter motor usage directly to the leisure batteries to fool the alternator to giving a full charge to the leisure batteries, and forget a split charge relay as this seems to be the limiting factor in the amount of charge while driving ,or is there something I'm missing ? The short answer is yes! It should be fairly easy to run heavier cables alongside the originals and either double them up or substitute the connections all the way from split charge relay to leisure battery via wherever it goes along the way - and that might be a problem if it goes via the control box or display panel. That's about the extent of my knowledge but I remember that Clive (the other one not CliveH) has done this with success in the past and no doubt the experts will soon be along to elucidate on the implications for modern systems! Link to comment Share on other sites More sharing options...
OxfordMorgan Posted February 14, 2012 Author Share Posted February 14, 2012 spospe - 2012-02-14 3:44 PM OxfordMorgan - 2012-02-13 7:32 PM Thanks Tracker, One of the things I was considering was another 135Ah to compliment my first, and a Sterling Battery to battery charger so I can run the engine for an hour or two if we are wild camping and try and charge them that way. There may be a bit of misunderstanding here. The Stirling Battery to Battery unit is to allow excess capacity form the leisure battery to top-up the starter battery, not the other way round. Running the engine will charge both the starter and the leisure batteries wheather you have a Stirling unit or not. Ah yes.. My mistake.. I was looking for something to put charge back into my leisure batteries as quickly as possible to maximise the time we could wildcamp. Does anyone have any experience of these types of charger? Link to comment Share on other sites More sharing options...
OxfordMorgan Posted February 14, 2012 Author Share Posted February 14, 2012 Brambles - 2012-02-14 4:20 PM I suspect Morgan meant alternator to battery charger. May not realise that is what he meant but am sure it is. Tracker, probably correct, most heater element will draw a lot more current when cold ( just like a light bulb) until the filiment is warmed up, so would not surpise me at all if the current is a lot higher initially. I did make a long detailed post about alternator to battery charging units but not sure how accurate it was so have deleted. Maybe try and come back to it later when I have checked the Sterling specs. Brambles, I for one, would be very interested in your detailed post about these A-B chargers. Morgan Link to comment Share on other sites More sharing options...
Brambles Posted February 14, 2012 Share Posted February 14, 2012 It is basically just down to the nature of modern calcium batteries and 14.4 volt output of the alternator. So is as you say Tracker. You can use heavier cables which will help a but but will not double the charge rate. The battery self limits the charge current for a given voltage. You can cleverly up the charge voltage but it has side effects like ..erm...damaging the battery if not done carefully, and also to much charge rate will heat the battery up. There are things you can do like use AGM batteries, which charge at a much higher rate and some flooded which have an exotic blend of lead alloys such a silver and Tin added and charge a lot faster. (This is what you have tracker in your Vartas - a chemistry which charges a bit faster for a given voltage). Clive's approach was also to use true traction batteries, these are a diofferent beast altogether , and can charge at a much much hiogher rate, then heavier cables etc will make a much bigger difference. The thing is, its not actually desirable to charge a battery too fast as it will reduce its life dramatically. As has been said these Eberspächer heaters where initialy designed for commercial lorries or certainly what they were used for and they of course have massive batteries. The company I worked for were the initial sole distributors for these in the UK for Lorry Cabs and got to know them quite well. I was always very critical and bemused as to why they used so much power, but seems it is needed to get them fired up as the cold diesel coming in and getting vapourised requires a lot of heat and energy. Also the noisy solenoid pump was a joke. One of our sales engineers came up with a really good method to quieten the pump down but was never adopted and so was left to just using compliant hoses and rubber mounts. click......click......click. In a lorry with the pump mounted rear of cab on chassis it did not matter. So back to charging batteries, yes heavier cables to the slave relays and the batteries will make some difference but not nearly as much as one would hope unless you have expensive AGM or Gel batteries. It is still worth doing though for the extra few amps charge you might achieve. Link to comment Share on other sites More sharing options...
JamesFrance Posted February 14, 2012 Share Posted February 14, 2012 You can certainly speed up the charging process and achieve a much greater level of charge with a smart regulator. Something to read here: http://www.adverc.co.uk/batterymanagement/adverc-battery-management-faq There are also cheaper products offered by Sterling: http://www.sterling-power.com/products-altreg.htm Link to comment Share on other sites More sharing options...
Rayjsj Posted February 14, 2012 Share Posted February 14, 2012 Just to add the the 'Main' use of Eberspacher Heaters/water heaters apart from road vehicles is in Boats, I didn't know that they had vast battery charging capacity or huge batteries. ;-) Ray Link to comment Share on other sites More sharing options...
Guest 1footinthegrave Posted February 14, 2012 Share Posted February 14, 2012 Rayjsj - 2012-02-14 9:28 PM Just to add the the 'Main' use of Eberspacher Heaters/water heaters apart from road vehicles is in Boats, I didn't know that they had vast battery charging capacity or huge batteries. ;-) Ray Boat folk have similar issues a quick google search below. My first boat, "Grey Goose" was originally fitted with gas heaters. They produced gallons of condensation and were quickly replaced by a 3.5kw Webasto. Like many of the posters here I was worried about battery consumption. The problem was solved by installing a magic black box for controlling the alternator's charging ability. I think it was called a TWC. I already had two heavy duty domestic batteries. These I kept but added a smaller (and much cheaper) car battery used solely foe engine starting. The TWC fed the charge to this battery first before topping up the heavy duty batteries. ;-) Link to comment Share on other sites More sharing options...
Derek Uzzell Posted February 15, 2012 Share Posted February 15, 2012 OxfordMorgan - 2012-02-14 7:35 PM spospe - 2012-02-14 3:44 PM OxfordMorgan - 2012-02-13 7:32 PM Thanks Tracker, One of the things I was considering was another 135Ah to compliment my first, and a Sterling Battery to battery charger so I can run the engine for an hour or two if we are wild camping and try and charge them that way. There may be a bit of misunderstanding here. The Stirling Battery to Battery unit is to allow excess capacity form the leisure battery to top-up the starter battery, not the other way round. Running the engine will charge both the starter and the leisure batteries wheather you have a Stirling unit or not. Ah yes.. My mistake.. I was looking for something to put charge back into my leisure batteries as quickly as possible to maximise the time we could wildcamp. Does anyone have any experience of these types of charger? Sterling Power's Battery-to-Battery charger is designed to do exactly what you want. http://www.sterling-power.com/products-battbatt-info.htm There are caveats relating to this type of charger (like a need to employ suitably heavy cabling and having good condition batteries). This is explained in more detail in RoadPro's product catalogue that you might find useful. A few reviews of the B2B charger can be found here https://www.roadpro.co.uk/retail/product_reviews.aspx and there are earlier forum comments here http://www.outandaboutlive.co.uk/forums/forums/thread-view.asp?tid=15889&posts=10 I've no hands-on B2B experience myself, though I did once meet an Auto-Trail owner with the system who was very positive about its ability to fast-charge his vehicle's leisure batteries following extended off-campsite stays. There are products that will 'balance' the relative charges of starter and leisure batteries - "Battery Master" is probably the most well known - but these do a different job to the Sterling B2B charger. http://www.vanbitz.com/product/Battery_Master_BMaster Link to comment Share on other sites More sharing options...
JamesFrance Posted February 15, 2012 Share Posted February 15, 2012 I had a 70 ft narrowboat built 12 years ago which we lived on for 4 years. We had a 100AH starting battery and a 400AH bank of 4 domestic batteries. I had an Adverc controlling twin alternators which could charge at 100 amps when the engine was running, so 2 hrs was enough to replace most of the half discharge which we could measure using a Mastervolt meter which could count the amps in and out. This meter also helped to operate a Mastervolt Combi unit which was a 50 amp charger when on mains hookup or a 1500 watt invertor when disconnected. The central heating used a Mikuni boiler similar to an Eberspacher wet version. The fridge ran on 240 volts from the invertor. From fully charged we could last for 3 days before the batteries dropped to 50%. Link to comment Share on other sites More sharing options...
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