AMB

You have put your finger on the flaw in the logic - you assume that the alternator can cope and that it provides 14v actually at the battery terminals at all times that the relay is closed. It doesn't - unless you have a remote sensing regulator on the alternator. It certainly doesn't in the time that you are waiting for the glow plugs etc or whilst the engine is idling. The relay closes the moment that switched 12v is available. If you were to draw out the equivalent circuit it would contain three voltage sources - the discharged battery, the main battery and the alternator. There are equivalent impedances associated with each of these. Charge impedances and discharge impedances are different and vary on state of charge and also charging time. The main battery will already be at or near the nominal alternator supply voltage. It will have a low discharge impedance and high charge impedance. The alternator cannot sink current, it can only supply, you effectively have two voltage sources close in value feeding the discharged battery. True, the charge/discharge current flow is not as simple as just considering the internal impedances. Depends on how deep you want to go. The impedances don't stay constant, neither does the battery capacity. You have to consider the state of the battery and whether it is in "interface charge" or later diffusion state. Because batteries are chemical devices with a physical size there are two stages to charging (and also discharging). The initial charge (like initial discharge) only affects the chemical reaction near the plates. With time the recharged acid diffuses deeper into the cell. It's not just theory. In my old job we had charging issues after a long day on site running off an auxiliary battery. Some tests back at the factory confirmed that charge sharing was occuring between batteries, charge rate was limited in practice (as per vulcan bomber comment) and an unexpectedly long running time was required to bring both batteries up to near full charge. The small diesel engine is newer still and pedal power is free. I'm happy to berth a dinghy under sail under all circumstances, but 38ft and several tons in close proximity to several hundred thousand pounds worth of other yachts tends to make you a bit cautious, especially in marinas where the wind can be variable and capricious. Whilst I prefer wind power, there are times when it's not available/sufficient and an engine will get you to berth before closing time.

Having apparently opened a can of worms and then spread them about liberally, I wasn't going to raise that issue directly, but you're right. You can't buck physics. It's horses for courses and you need to understand the advantages and disadvantages of each approach before selecting for your intended use.

At risk of tipping the can over and letting the worms breed .... one of the batteries will be discharging as the other charges, until they equalise. Recovery time is a different issue. Take a simple example. If you have two identical batteries, one fully charged and the second discharged, then connect them together. The fully charged will charge the other. Though the alternator will have some effect at this time, it will be smaller than battery to battery because of the different source impedances and longer cabling. If the batteries are of the same type and capacity they will try to equalise at an end point, approx 45-47% of maximum charge. If the batteries are in reasonable condition you will probably not have a noticeable issue. However, the peak currents involved will tend to pit relay contacts if too low a rating fitted. There may also be an effect on overall battery life. Assuming, battery capacity of 70Ah apiece, alternator rating of 70A and charging efficiency of 90%, it will take at least 1.25 hours of charging before the main battery is at full charge. In practice well over 1.25 hours because the alternator is only rated at 70A and is not capable of supplying this under all conditions, the calculation also neglects engine cranking current and other electrical demands on the system in the meantime. Consequently, the relay solution is generally better suited to expedition use than to everyday travel because of the increased amount of time that the alternator is available Re sailboat. The owner likes ice in his G&T, I prefer my beer a little cooler than it would be if just left in the cabin and both of us have bad memories of mains hook-ups in marinas! Have also had to sail into a berth a few times and it's not an experience I'd like to repeat on a regular basis, though I did learn a few words ....

Not my intention, or what I said. Apologies if you read more into it. Not having a go at you, just making the point that there was practical experience as well as theory in my response. It was part of my job. You can get away with a simple relay, but bear in mind the disadvantages and don't think that you are always going to have the benefit of a fully charged main battery, despite heavily using the auxiliary.

Mike, In my case theory is backed by practice, albeit mainly sailing and some work with trials vehicles and jury rigged systems - where the system is used in earnest. It's also a similar situation as jump starting a second car. Would you do that without your engine running first? The only points that I'm trying to make are that the simple relay system has disadvantages and consequently you cannot entirely rely on the method to safeguard engine starting from the main battery. There are also potential hidden issues such as reduced battery life. Obviously, medium use of the auxiliary battery (no deep discharge), reasonable time for both batteries to re-charge whilst the engine is running etc and you are unlikely to experience many problems in practice. The theory does assume good electrical installation - appropriate rating of cabling and relay, crimped connectors or crimped and soldered rather than just soldered etc. The poorer the installation, the less of a surge issue. I'd suggest that put a switch in the feed/return of the relay coil so that you can manually isolate the second battery. The gold plated solution is a second alternator with the ability to switch either battery as main or aux, next down is split diode (with auxiliary regulator and remote sense). When it comes to VSRs, you need to know what you are buying. Too easy to buy something with no practical advantages.

You cannot escape battery charge equalisation with a simple relay system. Simple physics. Battery at full charge and 20C = 13.6v. More than 20% discharged and 20C <, = 12.0v. Connect the two in parallel and the voltage across them must be the same. The only way that can happen is if the higher voltage battery discharges into the lower (aux) battery. The alternator charging current will split between the two batteries with the majority of current assisting to charge the discharged battery Internal resistance of lead acid goes up with discharge by 40-50% and also changes with temperature and age/condition. At low/medium currents, internal impedance fully charged is roughly 10 mOhm, so connect the two in parallel with a voltage differential of 1.6v and 25 mOhm = 64A peak, less if batteries not in top condition. Allow perhaps 10mOhm for the relay and you still have 46A Nominal alternator output of say 70A means that it should cope with normal demands, but not a lot in hand and you won't start to charge the main battery until the voltage across the two equalises.

Sorry to disagree SORNagain. Although you may not have experienced a problem in practice, the higher charge battery will always be depleted when connected across to a discharged battery and the alternator will always disproportionately charge the discharged battery until the charges equalise. Whether you see discharge from the main battery or not will depend on where you wire your ammeters relative to the relay and the state of the batteries.

May be the regulator or the field winding connection on the alternator

The basic split charge system using a relay operates as you suggest - when the engine is on it energises the relay, closing the connection between auxiliary and main battery. When the engine stops, the relay is unergised and disconnects the two - allowing you to use the auxilairy battery without risking flattenning the main (starting) battery. As Mike says, disadvantage is that, when you try and start the engine with auxiliary discharged, the main battery will face a heavy surge as it tries to charge up the auxiliary - effectively trying to share the charge between the two batteries. A battery isolator between relay and batteries is a good idea if this is going to be a problem. Or put a switch in the earth return of the relay coil to isolate the second battery if necessary. In my opinion voltage sensing relays don't offer much advantage and can be unreliable. Determining when a battery is charged using voltage alone (when being charged by the engine/alternator combination) can be tricky. It will be temperature dependent, battery condition dependent and load dependent. I've yet to see a VSR system which will cope efficiently with all of these. Diode split systems provide isolation between the batteries, but have an associated voltage drop which ideally requires an auxiliary alternator voltage regulator to compensate. Consideration also needs to be given to switch-over between battery functions unless you fancy swapping batteries over in the cold and wet when your main fails. The most reliable system that I've experienced was in a yacht - two batteries with manual switching to allow parallel or single operation and switch battery function.

I think that most people would agree, it's just that there's a lot more that you need to know about a modified vehicle (and its previous owners) than about a standard vehicle. Anyone who doesn't take a vehicle for a test drive before buying deserves everything that they get.

I agree, it's like any car new or old, get someone who knows about them to crawl all over them, ask the owner when the axle oil change is next due? when is the timing belt due? Find a well mod'ed 110 and there's a fair chance it will also have been well maintained and worth buying, but probably outside your price range. I'm a comparatively new owner and still have a lot to learn, but have seen an awful lot of bad workmanship on pimped as opposed to working off-roaders whilst looking for my 110. It's tempting to go for the chequer plate, big alloys, raised suspension etc, but it doesn't beat an engine and drive train that have been lovingly maintained sitting on a galvanised or waxoyled chassis. You want to know how bad you can get? Have just seen a disco with a "slight suspension raise" and large tyres. Nominal 2" raise, but brake pipes stretched as a result and will probably fail fairly soon. Just when you think that something is idiot proof someone invents a better idiot!

The main arguments against buying a 1st vehicle with mods are insurance and not knowing how well implemented the mods are. On the positive side, no one ever gets their money back on mods when they sell the vehicle, so you'll get the mods cheap. Like everything else, it's a balancing act. Unless you know the history or can see the quality of work on other vehicles, I'd say go for a solid, well maintained 110 and add your personality later.

Have just read the fitting instructions (www.RayneAutomotive.co.uk). Can't see any reason why it should not be suitable for any 300Tdi with H4 bulbs fitted. The loom takes power off directly off the alternator and does not fuse until after the live lead has been trailed over the engine compartment. Good place to take a live feed because it will be the highest voltage point in the entire truck. However, would recommend an additional fuse as close as possible to the alternator, plenty of wire support etc and sealing relays before fitting. I'd also recommend carrying a spare set of headlamp bulbs - I seem to remember reading somewhere that the life of ordinary tungsten bulbs has a 7th power relationship with working voltage. So a 10% increase in working voltage would halve life. Tungsten halogen not as bad in that respect and, unlike plain tungsten, reduces life if run below rated voltage because temperature does not necessarily get high enough.

I have original seals on my '98 110. They have seen better days and having read about variable quality of replacement parts I bought some late model take-offs from a breaker on Ebay. Bad move because condition was not as advertised and I returned them, but that's another story. Bottom line, both my '98 originals and the late model take-offs had reinforcing inserts at the bodywork bend point.

Yes, if you have enough metal. Then Big-sert or Time-sert bushes can work well. I've had no practical experience of Big-sert. Time-serts have a "top hat" section with rim that requires countersink to sit flush. Also a self locking mechanism which activates on first use. Does mean that you need a long enough bolt to activate the lock and, ideally, a little clearance beyond the insert to fully expand the self-locking.

No - one insert inside another. We used Twinserts (http://www.helicoil.com.sg/HeliCoil-Oversize-Twinserts.shtml) but you can also get oversize helicoils (larger gauge wire) that require a larger hole for the same thread size as standard. In both cases, much larger contact area than for standard helicoil, therefore much stronger.

I'd agree with the above. Suggest 1) check charging voltage on fast idle - should be around 14.5v depending on temperature 2) switch on a good load (headlights, wipers etc) and check charging voltage. Will drop, perhaps to 13.5 due to wiring losses. 3) fully charge the batteries then leave them disconnected (24-36 hours) to see whether they hold charge 4) Take an old fuse (or blow a new one!) and make up a test ammeter lead to plug into the fuse box to see where the current is going (engine on and off) Earths are always suspect. Doesn't take much to drop a volt or so.

We use helicoil inserts as standard on aircraft equipment. Usually much stronger than the base material. Only practical issues experienced where when a supplier tried to fit inserts into too large a hole or did not screw in far enough (leaving a protruding tang of helicoil above the surface). On investigation, the oversize hole was found to have been caused by drilling at too high a rate causing judder. In both cases the coil pulled out under load. Don't try and drill out in one pass. If you do, it can easily end up oversize with a weaker end result. Rather than scrap some very expensive machined castings we also investigated using double inserts. They worked a treat, massively strong. Now standard repair/refurb practice.

Having flushed the system, blown out the heater matrix, lubricated and adjusted the cables etc my 300Tdi heater appears to be working well. Certainly, got too hot last week with outside temp of 3C. I noticed that Haynes reckon the 300 thermostat should be 88C whilst the 200 is 80C - would make a big difference to cab temperature.

If the same as my '98 110 CSW, standard alloys require a 27mm socket to remove the nuts. Pillar jack and wheel brace stowed in a black bag under the second row seats. Wheel chock and security nut remover under passenger seat.

My first reaction would also have been bad earth. Now that you have a voltmeter you can check whether the problem is in the earth or feed side. Make up a long lead so that you can measure everything from the battery negative terminal. What are the voltages at each side of the bulb? Any significant voltage at the earth side indicates an earth problem as minimum. Look for connector corrosion.

As a student I saw first hand what happens when a lead acid battery shorts out. A friend was given an old Austin (Westminster?) with a failing battery. No real problem because it also had a starting handle. However, got to the point where the battery needed to be on constant charge. When his next grant came through he purchased the largest battery that would fit. Unfortunately it didn't quite! He had underestimated the clearance needed. As he tightened the clamps and slammed the bonnet down, the bonnet shorted out the battery. Immediately followed by a loud bang and, soon after, a smell of burning as the paint burnt off the bonnet and the metal surrounding the contact point deformed. A passerby called the fire brigade who pumped foam into the engine compartment. After hosing the foam out, we took turns lying under the car, with half a hacksaw blade sawing through the remnants of the battery terminal in order to be able to lift the bonnet. A very long job. It turns out that we were also very fortunate not to have had an explosion from the original battery

I can appreciate your dilemma Swarfega is the best option.

As I said - a distress purchase. Previous car died, new baby, no money and a neighbour who worked in insurance and knew of an HP reclaim going for virtually nothing. Thought that I knew a fair bit about cars before I bought it, but knew a lot more afterwards.

I got into the habit of keeping records with my second car - a Morris Marina. A distress purchase in almost every sense of the word. As with every Leyland at the time you needed engine number, chassis number, colour, day of week that it was built, name of foreman's wife etc before you could get the wrong part out of stores. Once I discovered the correct part number through a process of trial and error, I'd make a note and keep it in the car along with every other scrap of information that might help. Didn't often help, but it made me feel better. I later expanded the note taking to include fuel etc. and enter the data onto a spreadsheet every couple of months or so. Was well worth it when it came to selling. Have just bought a 110 with a pile of documentation and intend to put that onto spreadsheet - just so I understand what has been done.