The CTEK charger worked a treat. Its been on all night and battery is fully charged. Time to plug the beer fridge back in Duncan
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If I'd known I was going to be so thirsty this morning I'd have drunk more beer last night.
FFRR Autobiography 4.4 SDV8 MY17
D4 HSE MY13 SOLD
FFRR 3.6 Vogue TDV8 SOLD
D4 HSE MY10 SOLD
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15th Jul 2008 9:57 am
DiscoDunc
Member Since: 08 May 2006
Location: Bristol
Posts: 16390
found this
http://cgi.ebay.co.uk/CAR-STEREO-AUDIO-12V...otohostingDuncan
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If I'd known I was going to be so thirsty this morning I'd have drunk more beer last night.
FFRR Autobiography 4.4 SDV8 MY17
D4 HSE MY13 SOLD
FFRR 3.6 Vogue TDV8 SOLD
D4 HSE MY10 SOLD
D4 SE TECH MY15 SOLD
D4 XS MY12 SOLD
D4 HSE MY10 SOLD
D3 HSE MY06 - Re-Cycled Worldwide
15th Jul 2008 10:08 am
TallPaul
Member Since: 03 Jan 2008
Location: Near Reading
Posts: 1214
DiscoDunc wrote:
what do these circuit breakers look like and where would i get one, or more...
Marine suppliers are the best source in the UK, or one of the more special auto-electric places.
It seems a bit odd that the National Lunar system came with two fuses, a 150 between the main battery and control unit/solenoid and a 50 between the control unit and the aux battery.
can i just replace these with two home made fuses made out of copper pipe , or will this damage the control unit/solenoid
Please don't do that
If you want some new fuses, or higher ratings, Maplin or Halfords carry "maxi-blade" fuses that should be available in high ratings, or alternately you can get an inline fuseholder for AGU fuses, you can usually get these for about £10 and weatherproof ones are not much more.
EDIT: Oops this thread had page two! I am not sure you really want a $7 circuit breaker in your beloved Disco, best get one you can trust!!! Disco3 is now gone but not forgotten. Waiting for Disco6 with full aluminium construction weight reduction and hybrid engine...
15th Jul 2008 11:19 am
10forcash
Member Since: 09 Jun 2005
Location: Ubique
Posts: 16534
Word of warning about circuit breakers.....
most operate 'thermally' i.e. the bi-metal heats up to 'trip' the breaker, if this is in a hot engine bay, then the tripping current will be much lower (ask Chris Tyler ) there are magnetic CB's around but these are much more expensive, alternatively, locate the CB's inside the vehicle where the thermal gain will be negligible
15th Jul 2008 12:49 pm
DiscoDunc
Member Since: 08 May 2006
Location: Bristol
Posts: 16390
whats wrong with the fuses that are supplied, Sorry, I dont fully understand why they should be changed Duncan
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If I'd known I was going to be so thirsty this morning I'd have drunk more beer last night.
FFRR Autobiography 4.4 SDV8 MY17
D4 HSE MY13 SOLD
FFRR 3.6 Vogue TDV8 SOLD
D4 HSE MY10 SOLD
D4 SE TECH MY15 SOLD
D4 XS MY12 SOLD
D4 HSE MY10 SOLD
D3 HSE MY06 - Re-Cycled Worldwide
15th Jul 2008 5:14 pm
robsmith
Member Since: 02 Sep 2007
Location: Staffordshire
Posts: 2392
Whne fuses go bang they stay "gone bang", a circuit breaker can be reset, either automatically or by some sort of manual intervention.
Where you've got a big in-rush like trying to charge a dead yellow top a fuse would need to be rated at something over the expected surge current, say 100-200A. With a circuit breaker you can get them with a reasonable time delay, so they will pass 50A for a very long time, 100A for a few seconds, and break the circuit "instantly" at say 200A. Obviously an auto-reset breaker will wait a short period of time (a few seconds or so) then close, and be capable of doing this over a few switching cycles over a few minutes which should be enough to get a heavily over discharge yellow top back to taking a normal charge (of say 50A).
There are several things to consider when looking for a breaker, most obvious are the nominal amps and volts, but you also need to consider the rating time/current curve which tells you how long it will pass a given over-current for, the rated temperature, and the temperature/time/current characteristic - very often this is expressed in the form "50A, 12V dc, 100% - 100ms, 35C", whcih translates as a 50Am, 12V normal "continuous" current, give it 100A and it will open in 100ms (which is a bit quick for a yellow top), and all this is measured at a temperaure of 35C. For a yellow top I'd be looking for 100% - 1000ms (1s) at least, and for underbonnet use I'd look for 45 or 50C, so the one on mys desk is of no use for this duty
Try looking on RS or CPC and see what they do.
(btw this is quite a small breaker by the my standards, more used to 1000A continuous, 100000A clearance (means it will safely break 10,000A without destroying itself), 1000V - when one of those goes you get a REAL arc - one you cna read a book in a blacked out room by if things go wrong.......Rob Smith
Silver rools OK
15th Jul 2008 6:05 pm
drivesafe
Member Since: 23 Feb 2006
Location: Gold Coast, Australia
Posts: 867
robsmith wrote:
Whne fuses go bang they stay "gone bang", a circuit breaker can be reset, either automatically or by some sort of manual intervention.
Where you've got a big in-rush like trying to charge a dead yellow top a fuse would need to be rated at something over the expected surge current, say 100-200A. With a circuit breaker you can get them with a reasonable time delay, so they will pass 50A for a very long time, 100A for a few seconds, and break the circuit "instantly" at say 200A. Obviously an auto-reset breaker will wait a short period of time (a few seconds or so) then close, and be capable of doing this over a few switching cycles over a few minutes which should be enough to get a heavily over discharge yellow top back to taking a normal charge (of say 50A).
Well put Rob.
Hi again Duncan, be careful of the type of circuit breaker ( CB ) you get, it MUST BE an automotive type CB, there are many different types of CBs and most do not suit dual battery usage.
Those large black ones shown above are not designed for variable current use but are intended to protect things like sound systems, where there is a known maximum tolerate current and these types of CBs will trip within second of the current draw exceeding 10% more than their marked rate.
In other words, if it is a 100 amp CB, it will trip in a second or so at 110 amps and this makes them useless as you will have to install something like a 200 amp CB to allow for the inrush current of a fairly flat Optima battery and worse still is the start up current that some motors ( like fridge motors ) require.
At 200 amps, they will give you next to no protection at all.
An AUTOMOTIVE specific CB is designed to tolerate their marked current rate for a minimum of 8 hour and about 145% of their marked rate for 1 hour, which means a 50 amp circuit breaker will tolerate 75 amps for nearly an hour before tripping and much, MUCH higher currents for a few seconds.
This may sound strange but it’s almost the identical operation of a fuse and is similar to your domestic circuit breakers and fuses and they are all designed like this for the same reason, things like motors can have a near dead short occur at start up and AUTOMOTIVE specific CBs will tolerate this huge current surge for a split second without tripping and thus allowing the motor to start.
One more point, AUTOMOTIVE specific CB do not have a temperature rating because they are designed to operate at their marked current at engine bay temperatures.
The other important reason for using CBs over fuses in high current circuits is that, in a dead short event, a circuit breaker will go open circuit ( trip ) much quicker than a fuse of the same current rate can.
Last but not least and this is the most important factor to consider when designing an electrical circuit is that you have to cater for not just a the possibility of a dead short occurring but you must protect the circuit for an overload and this is something most people never factor in when designing their dual battery set up.
Unlike cable selection where bigger is better, with circuit breaker ( or fuse ) selection, the exact opposite is the case. The smaller the CB can be and still allow what ever device is connected to the circuit to operate correctly, the safer the whole circuit will be.
For example, if you use 6B&S cable ( 13mm2 ) in a dual battery set up, 6B&S cable has a 100% cycle current rating of about 105 amps. A 100% cycle rate is the continuos safe load rate of the cable.
If you use 6B&S cable then your protection should be no more than half the current rate of the cable or the current can actually exceed the safe current rate of the cable and not cause the protection to go open circuit but to fit the correct size protecting may mean the protection device goes open circuit every so often, which is particularly the case with dual battery set ups and Duncan, as you have found, your 50 amp fuse periodically blows, whereas if you fit an automatically resetting AUTOMOTIVE type circuit breaker, it won’t matter if it trips every now and again, your system will still work as intended and everything will be properly protected.
Sorry for the long winded reply but as you can see, there is a lot more to designing an automotive electrical circuit and with dual battery set ups, because of the much higher currents being handled, it’s even more important that you get it right.2008 TDV8 RR Lux + 2009 D4 2.7
15th Jul 2008 9:47 pm
DiscoDunc
Member Since: 08 May 2006
Location: Bristol
Posts: 16390
thanks guys,
i think i understand
but it still begs the question, why do national lunar provide fuses as oart of the charge kit, not CBs
costs i guess Duncan
-----------------------------------------------------
If I'd known I was going to be so thirsty this morning I'd have drunk more beer last night.
FFRR Autobiography 4.4 SDV8 MY17
D4 HSE MY13 SOLD
FFRR 3.6 Vogue TDV8 SOLD
D4 HSE MY10 SOLD
D4 SE TECH MY15 SOLD
D4 XS MY12 SOLD
D4 HSE MY10 SOLD
D3 HSE MY06 - Re-Cycled Worldwide
15th Jul 2008 9:53 pm
10forcash
Member Since: 09 Jun 2005
Location: Ubique
Posts: 16534
'cos CB's are suceptible to heat!!
BTW, fuses also have a time/current curve, not just CB's, MCB's or MCCB's. As far as 12/24VDC systems are concerned, the rupture current and flashover voltage are irrelevant although DC flashover is lower than AC, if you want to use CB's in the engine bay, either use magnetic ones or contactors with current sensing coils
15th Jul 2008 9:58 pm
RichieP
Member Since: 19 Sep 2006
Location: Reading
Posts: 380
OK Now I don't want to hijack duncs thread.... BUT..... the Disco3 battery/alternator/Charging system is capable of providing more than xxx amps..... so in a split charge system surely everything connected to the batteries should be able to sustain a 'sustained' current of 100amps plus? or have i not understand and had too many coca cola lights.... i.e. what happens if a D3 jumps a D3 with an aux battery?Richard......
2006 HSE Lugano Teal - with screens a DVD....PS2.... Freeview, and MANTEC plate!
2007 XS Commercial Java Black - with leather, Aux Battery and MANTEC plate
15th Jul 2008 10:03 pm
10forcash
Member Since: 09 Jun 2005
Location: Ubique
Posts: 16534
When you jump start another vehicle, the current is going to the main battery but mostly on-demand to the starter motor, the aux battery is irrelevant. I agree that the fuse limitaton is pretty stupid but bear in mind that the NL system is designed for Defeners etc. which have an alternator output of 55-80A so 150A peak output is always going to be an issue for these systems. That said, it's unlikely that the maximum output will be seen for long enough to blow the fuses in most situations. 50A fuses will tolerate 80A for about 6 or 7 minutes before blowing, obviously 150A (assuming the full alternator output were going to the aux. battery) will be tolerated for a much shorter time, possibly 40-60 seconds, in real-life situations, the most i've seen going to a completely discharged Optima on a D3 is 112A and this was only for about 20 seconds before it dropped steadily to about 68A over a minute or so
15th Jul 2008 10:14 pm
drivesafe
Member Since: 23 Feb 2006
Location: Gold Coast, Australia
Posts: 867
10forcash, Automotive circuit breakers are NOT susceptible to heat and are specifically designed to be used in the engine bays, also if you care to read my post, I specifically stated that the slew rate of automotive fuses and circuit breakers are similar, so why imply something different was posted?
RichieP wrote:
OK Now I don't want to hijack duncs thread.... BUT..... the Disco3 battery/alternator/Charging system is capable of providing more than xxx amps..... so in a split charge system surely everything connected to the batteries should be able to sustain a 'sustained' current of 100amps plus? or have i not understand and had too many coca cola lights.... i.e. what happens if a D3 jumps a D3 with an aux battery?
Hi Richard, the current rating of any circuit is based on it’s use.
In the case of jump starting, the currents required will be very high BUT are only needed for a few second, so a properly designed dual battery set up designed to handle 50 amps continuously, should easily and SAFELY handle 200 amps for a few seconds while jump starting.
It can get confusing when looking at current handling requirements of different circuits but some cable manufacturers supply full specs for their cable and when full specs are available you will find that cable actually has different current ratings for different uses.
For example, the 6B&S size cable I used above is rated at 103 amps when used in a 100% cycle rate, this means when it is used in a situation where it is carrying current continuously, like in a dual battery set up it is designed to safely handle 103 amps all the time, but the same sized cable is rated at 230 amps when used in a 20% cycle rated situation, like as starter motor cable where it is only handling this sort of current in short bursts.2008 TDV8 RR Lux + 2009 D4 2.7
15th Jul 2008 10:32 pm
10forcash
Member Since: 09 Jun 2005
Location: Ubique
Posts: 16534
Oh FFS you starting anothe ing match
Last word on the subject - ANY THERMAL circuit breaker will be downrated if it is used in an ambient temperature GREATER than its calibration rated temperature
Example time/current curve
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Ive been looking on 
, or will this damage the control unit/solenoid
ing match 
