Master
I think I have previously asked this but I now have more data. Do other Td5 owners notice that the voltage output from their alternator changes as the under bonnet temperature increases?
If so, this may be helpful.
I have just returned from 4 weeks traveling in central Qld, including a couple of weeks of bush and other camping. I found I had trouble keeping my second battery (105Ahr) charged when I remained camped for more than a couple of days. What happens is that when the engine is cold, the alternator output varies between 14.6V and 14.7V (I have tested repeatedly with a digital meter). However, when we've been running for an hour or so at high speed (100kph say) and everything under the bonnet temperature is really hot, the alternator output drops to 14.13 or so.
This is a problem because I can't get the second battery back up to full charge. I have a solar panel too, but one tends to camp where there's full or partial shade which limits the effectiveness of the panel.
I noticed this some time ago with my first alternator which was replaced with an OEM unit a few months ago. Same behaviour.
I have decided to get a CTek DC to DC charger which is supposed to charge the battery more efficiently and maintain it better when fully charged.
Is there something other than the alternator itself which controls the output voltage? I know that happens in some of today's "smart" vehicles but not in my 2004 Disco as far as I am aware.
I have just today installed a CTek Duel in my caravan to charge 2 x 100Ahr AGMs from the D2a. I'm aware the alternator will struggle to 100% charge the batteries but I also have a 130w solar panel which will remain the main charging source. Be aware the CTek Duel has a temp. "probe" to attach to the second battery so it can adjust output. I assumed the D2a alternator is not a self adjusting output "smart alternator" but also could not find a definite answer.
YarnMaster
you are right, the D2 charging system is not a "smart" one, it has just that rudimentary regulator... this voltage drop happens on mine too but i put it on the copper wire's resistance/temperature coefficient which means +0.393% per 1 degree C... there can be made exact calcutations too as long as somebody takes the time to measure the lenght of the cables... IMO as long as the resistance grows there will be a certain voltage drop on the wiring too, and as the temperature in the engine bay goes from ambient up to 60 - 80*C (i didnt measure it) this might be the explanation
Discovery Td5 (2000), manual, tuned
Fossicker
Hi the Ctek dc dc charger has a maximum working temp of 50degs, most engine bay temps are well over this limit. May have to move it into the cabin.
The d2 td5 alternator is duty cycle controled by thd ECU. Not quite on the same level as smart alternators but almost.
ChatterBox
Mine kicks off at 14.5v then drops to about 13.6 after only 20 minutes or so.
Happy Days.
TopicToaster
The ability to charge to capacity is dependent on a few factors, not least of all your battery types. Avoid the DC-DC chargers. I can't go into the details but they are not all they are claimed to be. Tim (Drivesafe) on here has all the info, for disclosure he sells his own charging systems, designs them and has all the info. Before taking any plunge he at Home Page | TRAXIDE - RV | Traxide - RV.
As for the variable output of the alternator. Of course it falls, as charge level goes up (surface charge at least) it "sees" a higher charge level (but the battery is still not to full amp capacity). Output drops but continues to trickle the battery up to a ful state of charge.
Where are you measuring the voltage? At the battery or back of the alternator? As stated, there will be voltage drop, but someone actually went to the trouble of measuring and calculating it while trouble shooting something once and the drop is so negligible that it's hardly part of the issue. There's more systems awake draining voltage while shutdown that the drop across the wiring. Added to that, remember when running the alternator is not just charging, it's compensating for all operating elec systems, A/c, radio, SLS, all the ECU's, fuel pump, etc etc so output while directed to the battery does not all end up there.
Drifting a bit off topic but being a novice in this area I did a lot of research. The basic info out there was that charging the 2nd or more batteries thru' an isolator system alone (such as traxide) can't charge the aux battery to 100%, at best maybe 75-80%. The Ctek dc-dc charger claims to boost the alternator battery current so that its possible to charge 100% as well as acting as an isolator. I'm hoping its true because I've just put one in It is also claimed it works with the new "smart" alternators.
TopicToaster
And thats the start of the falsehoods, this "boost" HAS to be powered from somewhere. Figures, graphs and claims all show this "boost" but not how it's obtained or where the extra power is sourced from.claims to boost
As I said, Tim can break it sown and explain dumb enough for me to understand in one or two sentences.
The MOD Father
If my alternator puts out 130Amps,,Originally Posted by discolaw
how much more than that do you need to charge 2 batteries?
"How long since you've visited The Good Oil?"
'93 V8 Rossi
'97 to '07. sold.
'01 V8 D2
'06 to 10. written off.
'03 4.6 V8 HSE D2a with Tornado ECM
'10 to '21
'16.5 RRS SDV8
'21 to Infinity and Beyond!
1988 Isuzu Bus. V10 15L NA Diesel
Home is where you park it..
[IMG][/IMG]
And there, unfortunately lies the biggest false hood perpetuated on the net and by those who wish to sell expensive and unneeded devices to punters.
Ask yourself:
- How big is the aux battery
- How far do you discharge it
- How long do you drive (realistically) per day
A relatively simple relationship then takes place.
If you are driving long enough to push the needed power into the aux battery it will full charge - using the alternator "unbridled" (lets assume 130amp alternator) this will be at the max rate the battery / alternator combo can work at.
Using a Dc-Dc system you are restricted to (lets assume this is the output) - 20amps per hour.
Lets make an assumption that the battery you have can accept 40amp current
the alternator throws 40amp in
the Dc-Dc unit throws 20amp in
now we will suggest the 100a/h battery is 50% SOC
not allowing for external factors... we need to put 50a/h back
Alternator does it in around 75 minutes of driving
Dc-Dc unit does it in 150 minutes of driving
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