cable sizes for Aux battery in rear of vehicle

Submitted: Saturday, May 22, 2010 at 15:46
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I want to set up an auxillary battery in the rear of my vehicle (85a/h deep cycle). I have a 100amp Redarc isolator and 2 x 100amp circuit breakers. I want to be able to disconnect battery if need be via 50 amp anderson plugs so that I may use the battery in the odd night or two free campingin the caravan. Can I get away using 8B&S cable or do I need lto go to 6B&S. I noticed in a video for the thumper style battery installation that they only use twin core 6 mm to install the thumper into the back of a land cruiser. Also the lugs in the 50amp anderson plugs that I have will not accomodate the larger 6 B&S cable
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Reply By: Maîneÿ . . .- Saturday, May 22, 2010 at 16:42

Saturday, May 22, 2010 at 16:42
The defining number you have to work with is, what’s the largest cable that will fit into a 50 Amp Anderson plug, you could get the next size up and get thicker cable into it.

The strongest chain is only as strong as its weakest link
in terms of your system the cable size at the Anderson plug is the weakest link.

"50 Amp (grey) Anderson plug = recommended cable 6sq mm, rating 62 Amps"

Maîneÿ . . .
AnswerID: 417682

Reply By: ChipPunk - Saturday, May 22, 2010 at 16:51

Saturday, May 22, 2010 at 16:51
If you have 100A circuit breakers, you must have cable rated for 100A or higher.

AFAIRecall, 50A Anderson plugs are not rated to (continuously) break a 50A load - merely to carry 50A. I would not recommend breaking 10A with them.

There is nothing stopping you fitting smaller breakers or fuses and hence using a smaller cable etc.
AnswerID: 417685

Follow Up By: drivesafe - Saturday, May 22, 2010 at 18:01

Saturday, May 22, 2010 at 18:01
Unlike other types of plugs and sockets, 50 amp Anderson plugs are rated for 50 amp Make-N-Break situations.

This is the very reason Anderson plugs are perfect for dual battery systems.
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FollowupID: 687771

Follow Up By: oldtrack123 - Saturday, May 22, 2010 at 18:43

Saturday, May 22, 2010 at 18:43
Hi ChipPunk
But you can have any size fuse smaller than the cable rating
100ampcable with 50amp fuse is not a problem
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FollowupID: 687777

Follow Up By: Maîneÿ . . .- Saturday, May 22, 2010 at 18:46

Saturday, May 22, 2010 at 18:46
50 Amp (grey) Anderson plugs are rated at 62 Amps, according to their technical specifications

Maîneÿ . . .
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Follow Up By: ChipPunk - Saturday, May 22, 2010 at 19:09

Saturday, May 22, 2010 at 19:09
Thanks for the Anderson correction - it's been a while since I checked their specs.

oldtrack123 - that's what I said.... The point is, the cable "shall" not be less than its fuse.
In many situations I will argue for a cable that is many times its fuse rating - eg - to minimise voltage drops. So many think they must be matched. (And I'm not talking about AS300 etc - that has its reasons...)
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FollowupID: 687783

Follow Up By: ChipPunk - Saturday, May 29, 2010 at 03:46

Saturday, May 29, 2010 at 03:46
Regarding Anderson interruption ratings, a telco dude yesterday agreed that Anderson connections are NOT rated for make & break.

I have not checked the Anderson spec, but:

(1) I found the "recent" source of my info - namely the Altronics calatog (2010-2011).

(2) - I have SMH and KST "Anderson" connectors and both have "NOT FOR INTERRUPTING CURRENT" moulded into their bodies.

So check your plugs. DC arcs and their molten offspring are NOT fun!!


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FollowupID: 688730

Follow Up By: drivesafe - Saturday, May 29, 2010 at 09:13

Saturday, May 29, 2010 at 09:13
If you download the data sheet for the SB50 Anderson 50 amp plugs, the data specifically states

Life
a No Load (Contact/Disconnect Cycles) to 10,000
b Under Load (Hot Plug 250 cycles @ 120v) 50A
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FollowupID: 688740

Follow Up By: ChipPunk - Saturday, May 29, 2010 at 15:09

Saturday, May 29, 2010 at 15:09
In that case, BUYER BEWARE.

But both the SB50 & SBS50 drawings off the same site clearly show the same as below except it omits the English "Not for interrupting current" (only the French is impressed).

And the data sheet only states "...50 amp rating, 600 Volts continuous AC or DC operation".
It says nothing about being interrupting under load. (I will not try to explain the "Life" for 50A "Under Load (Hot Plug 250 cycles @ 120V)" specification you mention, but maybe lasting 40x less than no-load suggests something? And if you are aware of how a DC arc behaves, you might worry about that 251st interruption (statistically speaking).


The "Andersons" as supplied by Altronics, Jaycar, a Perth-based eBay seller, and - from what I was told - ABR-Sidewinder - may not be genuine Andersons.

I found no genuine "Andersons" here.
They are SMH else KST. Both are UR stamped.

SMH has "SY50A-600V FOR DISCONNECT USE ONLY" & "NOT FOR INTERRUPTING CURRENT"

KST has "BMC2S MAX 50A 600V please refer instruction sheet foir disconnect use only" & "Not for interrupting current"


But let the use decide.
The spec sheet caries no specific warning. The warnings on the plugs are not obvious. So why not break their connection under load?
I strongly suggest - in fact insist - that you follow the instruction on the plugs.
And now that you know about it - you can't say you didn't understand French....
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FollowupID: 688773

Follow Up By: drivesafe - Saturday, May 29, 2010 at 16:37

Saturday, May 29, 2010 at 16:37
Hi Chip, I can’t comment on what is or is not on the plugs bought here, but I will comment on the source.

For the very reasons you have posted above, the lack of quality and the confusion over what they can and can’t be used for, I DO NOT buy Asian Anderson ( or imitation Asian Anderson ) plug.

I only source the genuine USA made Anderson plugs from the States.

The old saying, “You can’t substitute for quality”, stand fast here.

As to only getting 250 operations at 50 amp loads, do your math.

How many times would you plug or unplug your Anderson plugs while there was a full 50 amp load going through them.

A little reality check, because the motor would be idling, you would be lucky to have 20 amps going through them, and while this is way below their maximum Hot Make-N-Break current, it’s still way too high for trailer type plugs.
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Follow Up By: oldtrack123 - Saturday, May 29, 2010 at 21:21

Saturday, May 29, 2010 at 21:21
Hi
If we look @ the specific application
WE have a max current of 10amps, a basically non inductive load
Actually with engine off or @ idle I would expect less.
A voltage across the break, max of probably 2.4v
The power dissipation in the arc is 24watts

Wow stand back every thing will melt.!!!! crap!!!
Geez, the arc would hardly be noticeable.
The contact faces may suffer damage over time leading to high resistance contacts, but that would be the limit.
Again we are talking about a specific application, we are not trying to break a 50amps dc inductive load @ 110 v or even 12v
Peter
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Follow Up By: Maîneÿ . . .- Saturday, May 29, 2010 at 21:42

Saturday, May 29, 2010 at 21:42
oldtrack
Yes, the appliance will (should) be 'off' anyway when the Anderson plugs are disconnected, the Amps and Voltage numbers will then be low by comparison to most of the numbers mentioned above.

How many times will the Anderson plug be disconnected anyway?
I think it will not be enough to get to the limit of its life, even then you just replace the 2 x removable 'spade' type connection within the plug, not the entire plug.

Maîneÿ . . .
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Follow Up By: oldtrack123 - Sunday, May 30, 2010 at 10:24

Sunday, May 30, 2010 at 10:24
Hi Mainey

Gee , you & I agreeing, what is the world coming to

But yes sometimes people do go far beyond the intent of the OP
Then the applicable facts get lost in the general attempt to air knowledge
The OP then cannot see "the grass for the trees" so to speak.
Peter
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FollowupID: 688877

Follow Up By: Maîneÿ . . .- Sunday, May 30, 2010 at 14:04

Sunday, May 30, 2010 at 14:04
Peter,
Actually I agree with you, it's just that I believe to ascertain the Wattage or Voltage of a solar panel you have to use the actual Wattage or Voltage and Amperage *produced and measured* at that solar panel to work it out mathematically, you can't use the voltage of a . . . .
well I’m sure you know what I mean :-)

Maîneÿ . . .
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FollowupID: 688903

Follow Up By: ChipPunk - Sunday, May 30, 2010 at 19:12

Sunday, May 30, 2010 at 19:12
Drivesafe - please do not blame me if Anderson themselves say "Not for Interrupting Current".
Please look at the drawings for the SB & SBS 50s at andersonpower.com/products/multipole-sb.html.
I assume that is their American site for American produced items?
If not, please link me the their American drawings.
Or post a pic of your Andersons showing that the do NOT have that warning.

Do not shoot the messenger.
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Reply By: drivesafe - Saturday, May 22, 2010 at 17:57

Saturday, May 22, 2010 at 17:57
Hi Rayza, the standard 50 amp Anderson plug terminals will easily accept 16mm2 and 6B&S ( 13.5mm2 ) is a sloppy fit, so you might have the wrong terminals.

To safely accommodate 100 amp circuit breakers in a dual battery set up, you need to use nothing less that 3B&S ( 25mm2 ) cable, otherwise thinner cable can melt in an overload situation, something that is more common than a dead short, in dual battery systems.

50 amp circuit breakers with 6B&S cable will give all the protection you need and the current carrying capacity with out too much voltage drop.

If you use 8B&S ( 7.9mm2 ) cable, the largest safe sized circuit breaker you can use that will give you overload protection is 30 amps, and you will have a fair bit of voltage drop in that thinner cable, so your batteries will take much longer to charge.
AnswerID: 417690

Reply By: Rayza1952 - Saturday, May 22, 2010 at 18:07

Saturday, May 22, 2010 at 18:07
thanks gents guess I go 6 B&S and get some smaller fuses
AnswerID: 417695

Follow Up By: drivesafe - Saturday, May 22, 2010 at 19:33

Saturday, May 22, 2010 at 19:33
Hi again Rayza, I would suggest you go for 50 amp auto resetting circuit breakers or you will be replacing fuses every so often.

A single battery is unlikely to pull a very high current load even when very low, but if you decide to add a battery to your caravan, you could get a situation where you pull some pretty high currents if both batteries are low.

This all depends on how big your alternator is.
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FollowupID: 687790

Follow Up By: ChipPunk - Sunday, May 23, 2010 at 19:16

Sunday, May 23, 2010 at 19:16
I agree with auto-resetting CBs!
Lots of reasons why currents will be exceeded despite there being "no fault".

I hate finding out that I missed 6 hours of charging or 6 hours of fridge contents thawing out because some stupid fuse blew for some short-term inrush current.

I went from 30A fuses to 50A auto-resetting CBs. No problems since! (The cable is rated higher than 50A...)
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FollowupID: 687913

Reply By: AlbyNSW - Saturday, May 22, 2010 at 20:18

Saturday, May 22, 2010 at 20:18
I have a similar setup to what you are proposing. I initially had it wired up in I think 8B&S and found that I was getting too much voltage drop.

I have since rewired with 2 B&S You have to cut a couple of wire stands off to get into the anderson plug but that is no problem.
I have 60 amp resettable breakers
AnswerID: 417720

Follow Up By: Maîneÿ . . .- Saturday, May 22, 2010 at 20:53

Saturday, May 22, 2010 at 20:53
2B&S cable is 32 mm2, how many starands did you cut off to get it into a grey 50 Amp Anderson plug?

Maîneÿ . . .
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FollowupID: 687810

Follow Up By: AlbyNSW - Monday, May 24, 2010 at 08:45

Monday, May 24, 2010 at 08:45
Probably half a dozen to fit into the terminal lug before soldering.... it is a tight fit, I also had to scim a little of the insulation off to fit into the plastic anderson housing but it all fits fine.
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FollowupID: 687960

Follow Up By: Member - Andrew (QLD) - Monday, May 24, 2010 at 10:35

Monday, May 24, 2010 at 10:35
From a reliable source:

2 B&S ..is cross section 32.5 mm squared and 399 strands
6 B&S ..is cross section 15mm squared and 168 strands

Anderson SB50 accepts #6 wire if selecting the correct terminal, otherwise sounds like a SB175. I suspect a couple more strands may have been cut off if not LOL

Andrew
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FollowupID: 687969

Follow Up By: AlbyNSW - Monday, May 24, 2010 at 12:23

Monday, May 24, 2010 at 12:23
Not up to speed on anderson plug model numbers but they are definately the common standard size ones rated at 50 odd amps.
You may be right that I trimmed more strands than previously noted, I can't recall exactly as it was a while ago, I just remember working around the cable with a stanley knife reducing the diametre until it fitted in. I did not think that was a problem as the aim of the game as I understand it is to keep a large cross section in the long cable runs to combat voltage drop. I would of settled for 3 or 4 B&S cable but was able to source tinned 2 B&S cable from a boating supply at a better price.
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Follow Up By: Spade Newsom - Monday, May 24, 2010 at 18:07

Monday, May 24, 2010 at 18:07
Aren't there #8 lugs that can fit in the 50 amp andersons, or did I read that wrong - never used them as 6 B & S fits into #6.
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Follow Up By: Member - Andrew (QLD) - Monday, May 24, 2010 at 18:34

Monday, May 24, 2010 at 18:34
There are #6, #8 and #10 anderson contacts for the SB50. Datasheets available here: Anderson connectors

BTW #8 is smaller wire sizing than #6 ;)

Andrew
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FollowupID: 688024

Reply By: paulnsw - Sunday, May 23, 2010 at 08:38

Sunday, May 23, 2010 at 08:38
Do the job properly and use 8B&S in the vehicle and Ctek D250S DC to DC charger with correct type of deep cycle battery. Ctek D250S had battery isolator built in. Can also be used for solar regulator if you add solar panel.
If going to use your caravan a lot use 6B&S and put the Ctek D250S and battery in caravan.

Direct cable systems and gadget boxes of tricks for direct cable systems are all crap sold by snake oil salesman. Impossible to charge auxiliary battery to full capacity. Have no vested interest like some trolling to sell junk boxes for direct cable systems.
AnswerID: 417753

Follow Up By: drivesafe - Sunday, May 23, 2010 at 11:02

Sunday, May 23, 2010 at 11:02
Hi paul and you need to do a bit of research because although Ctek claim this device can be used as a DC - DC step up charger, the problem with this device is that it has a low voltage cut of 12.8v, which is way to high and makes it useless unless it in mounted next to the cranking battery and mounting it in a caravan to be used as a DC - DC step up is a total waste of time and money.

If some has already run 6B&S cable through to their caravan, they already have a better charging set up than your device could do.

Furthermore, because you need to mount this device next to the cranking battery, you still end up with a voltage drop at the house battery and add to the fact that having this device in-line with a limited current out put, will mean you will have an even greater voltage drop at the house battery.

Now to make matters even worse, the instant you add a second house battery while using this or and other DC - DC step up, if your house batteries are low, you will actually have to drive for many, MANY more hours to charge your house batteries than you would with nothing more than 6B&S cable.

paul, I think your the one that has been had by the snake oil pedlars.
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FollowupID: 687855

Follow Up By: paulnsw - Sunday, May 23, 2010 at 14:14

Sunday, May 23, 2010 at 14:14
The snake oil salesman at work again. Nothing worse than people that push a barrow full of bad knowledge and misinformation to try and feather their own nest. About as low as anybody can go. Even worse when the snake oil posted is blatantly wrong information in an attempt to further their own bank account. Disgusting practice.

Operating voltage of the Ctek D250S is 7V to 22V
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FollowupID: 687873

Follow Up By: drivesafe - Sunday, May 23, 2010 at 14:36

Sunday, May 23, 2010 at 14:36
Hi again paul and not sure of your problem but you seem to be very happy to deceive people.

The standard Ctek D250S has an operating voltage range of 12.8v to 22v.

On REQUEST, you can get a D250S with modified operating voltages of 7v to 22v.

BUT

To have this modified version you have to sacrifice a number of the automated features only available in the standard version and again, this makes to this device anything but desirable for charging caravan house batteries.

For those interested, you can down load the flyer for this device from the link below.

http://www.ctek.com/PDF/D250S_Flyer_UK_low.pdf
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FollowupID: 687877

Follow Up By: paulnsw - Sunday, May 23, 2010 at 17:39

Sunday, May 23, 2010 at 17:39
Drivesafe please stop telling blatant lies to attempt to back up your snake oil sales manure. You will stoop as low as you can to attempt to flog your snake oil devices which are useless. YOU ARE TALKING RUBBISH.

The brochure says nothing like you are trying to say. I have fitted the Ctek D250S in many applications and used as a solar regulator.
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FollowupID: 687901

Follow Up By: Maîneÿ . . .- Sunday, May 23, 2010 at 19:30

Sunday, May 23, 2010 at 19:30
Paul
Why not post a LINK to the manufacturers technical information on their web site ?

Will save all the childish name calling and abusive tone of some of your posts

Maîneÿ . . .
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Follow Up By: oldtrack123 - Saturday, May 29, 2010 at 21:36

Saturday, May 29, 2010 at 21:36
Hi Paul
Perhaps you should go back & read the OP

He is not talking about charging in his van He wants to charge in rear of his tug.

Absolutly no reason to even consider the sort of expense you are talking about.

The direct connection will be totally adequate if used with heavy cables as recommended

Peter
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Follow Up By: ChipPunk - Sunday, May 30, 2010 at 19:47

Sunday, May 30, 2010 at 19:47
I agree.

dc-dc charger people seem to assume that only 13.8V is available from an alternator.
Even if it was, this can easily be increased for typical 2 & 3 wire alternators (SIL types - not modern DP types).

When 14.4V is available from the alternator, it is relatively simple to fully charge remote batteries.
If their load is too high or cabling too thin so that a voltage drop is inevitable, then run the load from the front and charge the rear battery through separate cables. If the alternator is 14.4V, the rear/remote battery will reach 14.4V (less whatever voltage drop it's "float current" of (probably) 1-2 Amps causes.

That is the SIMPLE method - somewhat cheaper than $200 or more.

Even if you increase the alternator voltage to above 14.4V so that the rear battery/load gets 14.4V and drop the front voltage to 14.4V, dropping a voltage is far cheaper than increasing it (similar PWM methods, but merely "chopping" current like a dimmer switch - not "transforming up" via inductors etc.


The of course there is always a second alternator that monitors the rear battery.... No 20A or other current limit. Alternator redundancy if the main alternator fails. No problem is the main alternator is too small to provide the power required. Cheaper than $200 or more... - definitely if it's an alternator for $45 from a wreckers, or $15 on special....
Okay - maybe extra engine brackets or belt(s) etc, but better efficiency than a dc-dc converter or charger. Then isn't another alternator cheaper than a dc-dc beast?

So many ways.....

Oops sorry - did I just destroy another market?
$5 battery isolation switches are bad enough...
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Follow Up By: oldtrack123 - Sunday, May 30, 2010 at 20:13

Sunday, May 30, 2010 at 20:13
Hi ChipPunk

This is getting out of hand 1st Mainey & now you agreeing with me.
Your above post sums it up nicely
Peter
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FollowupID: 688967

Follow Up By: ChipPunk - Sunday, May 30, 2010 at 21:04

Sunday, May 30, 2010 at 21:04
Geez man, give me a chance to change my reply.
Agreement is one thing - impossibility another....!

Nah - the "other" is messy and confused. Too much for me to read over for now - I merely recall key statements that I commented on.

But this one IMO is simple.

Interestingly a related question sprung up on another forum asking how frequently these systems (dc-dc) are used for THIS sort of purpose.
The OP knows their use & application, but finds this type of scenario puzzling - they find it is usually the available power that is the problem (eg, solar or alternator output) - NOT the voltage.
But he well knows the Australian situation versus (say) stateside. Over there people just do not fit "capacitors" or "bigger batteries" to power big audio and other systems - they see to know to start with distribution & alternators (eg, "the Big 3" being "grounding" and alt-battery).

And he is well used to people trying to push bullsh & hype. A few ACCC suits here and there. Wiping out a few wealthy incomes. (It is his $5 "battery isolator system" I use. And he can't figure out why anyone here would have set battery isolation voltages to less than (say) 13.5V let alone 12.7 or 12.5V!! And as to whoever was arguing with me that their ~$100 80A isolator "provided more AH" than my simple isolator.... straight to jail! (That's gaol for us!).)

But for me to pay $200 or $400 for something that only "charges" to 20A when my alternator & $10 isolator charges at 40A, and does not have the same conversion losses? (Do you like losing 10%-20% of power for a conversion?)


I'm keen to clean up a few products and solutions, and enlighten people if I can.
Then I'd like to clean up other discussions and misunderstandings. (So much time to spare, yet none left over!!)


And don't let the occasional agreement get you down. (LOL)
I actually prefer disagreements anyhow because that's where I learn something new or different; have something corrected or qualified; or manage to teach a few....
But that is VERY different to flaming etc. (OldSpark is none too subtle about that either....)
But we both understand mis-communication, and (our own!) bad expression, or not being "obviously" discussing a particular aspect only.
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FollowupID: 688983

Follow Up By: oldtrack123 - Sunday, May 30, 2010 at 21:27

Sunday, May 30, 2010 at 21:27
Hi ChipPunk
If you thought you & I were having a battle just wait & see what your comment :
"Interestingly a related question sprung up on another forum asking how frequently these systems (dc-dc) are used for THIS sort of purpose.
The OP knows their use & application---------------------------etc"
will bring forth
WAiT for it,
,.or maybe post a link

I could try & find links on two other forums where the pros & cons ,Me included, got quite heated.
Drive safe will know the ones I mean lol

Peter
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FollowupID: 688991

Follow Up By: ChipPunk - Sunday, May 30, 2010 at 22:27

Sunday, May 30, 2010 at 22:27
A link will be forthcoming assuming it's worthwhile.

At the moment the only response is probably similar to ours - ie, WTF? The inefficiency. And....


Let's just say I'm changing tact. I'll supply the rope, or shovel.
Catching and filling in is easier than prevention.
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FollowupID: 689007

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