I have an interesting problem (all of my own making!)
To give a bit of background. In this weather my defender 110 CSW (19J engine) struggles to heat the cabin. When travelling down a motorway it just about keeps up, when down on the A and minor roads, you just get colder and colder! In a few months time I will also be having dogs sleeping in the back of the car through the night, so I wanted a way of keeping the car warm separate (or additional to) the engine.
Prior to the recent thread I had been exploring diesel heaters and they seemed an ideal solution. The problem was that at this time of year the 12v versions were going for quite a premium. So I bought a 24v version from eBay. (Just waiting for it to arrive).
This was bought deliberately (it was about =A3140 cheaper than the equivalent 12v version!) and I now need to see how to provide the 24v in the car for the diesel heater (in fact, providing it is easy, that's just a second battery, keeping that second battery charged is the more interesting problem!)
I think there are three options and there are pros and cons to all. I would appreciate your views on the various options and whether any of you have a similar problem and how you have solved it.
Firstly the battery drain is not huge. Start up is the worst at 11.25A (due to heating the glowplug I suspect), the ongoing power for the fan then drives the consumption which is quoted at 1.25A for boost and only
0=2E4A when running at low/medium power. This is of course at 24v.So options:
Option 1 -
Weekly charge of second battery. Probably the simplest option and just needs to be a good habit to get into. Remove the second battery once a week and charge it overnight. With the drains quoted above, even leaving the heater on all night shouldn't have a major drain on that battery. The downside is the hassle of removing the battery once a week. (This could be done through an isolation switch and an external socket and may be the way that I go)
Option 2 - Fit a 24v alternator (is one done for the 19J?) and charge both batteries at once. Slightly more complicated and there will be a need to uprate the charging light bulb to 24v. Also the batteries, even if across the 24v will never charge equally. Remainder of car stays at
12v. Are there any issues I've missed?Option 3 - Fit a clever change over circuit that allows the 12v alternator to alternately charge each battery. The lions share of the charge should go on the "car" battery with occasional time for the supplementary battery. For example I would expect that after initial starting there is a minimum of 20 mins charging the main battery and then say and uneven cycle of say 2 mins on the supplemantary batteyr and 6 minutes on the main battery.
Possible problems as it is far more complicated and the risk of stray (high current!) paths.
OK, I could have spent more and saved all this hassle, but what the heck, this is an interesting challenge.
So any thoughts, comments, insults :-)
Cheers
Peter
1990 110 CSW (Reggie the Veggie) 1959 Farina A40 1964 Rover P4 110 1974 Hillman Imp