Rear 12v Power options

Submitted: Sunday, Jan 24, 2010 at 03:41
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Howdy all, im after some info from the 12v gurus.

What i want to do is put a couple of plugs in the tray for running various items. I will be putting in an Anderson plug, merit and normal cig plug. The load will never exceed 12 amps(approx), even if using all plugs at same time. Anderson will be for fridge, and others for lights/chargers etc.

I will be supplying power direct from battery, fused and then through a circuit breaker, to a buss bar and then feeding each plug independantly through there own fuse.


I would like to have switchs on the plugs, the merit and cig plug anyway, as some of my lights dont have switchs and i dont wanna have to unplug them all the time. What i need to know is, could i use the normal 20A waterproof toggle switchs to switch each plug(on/off), or would i need something else. Would like to have a relay set up that i could control from inside the cab ultimately to turn power on/off in back, but i would also like individual control over the plugs too.




Also being powered direct from the battery and not through accesories, would there be any chance of surges or spikes upsetting the vehicles computer/electrics, or even voiding warranty?

I might even put an inline battery discharge protector in as i dont have dual batteries just yet.

Any help or criticism is greatly appreciated. Not the sharpest tool in the shed when it comes to electrics. Just need a point in the right direction.

Thanks
The Boss
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Reply By: drivesafe - Sunday, Jan 24, 2010 at 05:31

Sunday, Jan 24, 2010 at 05:31
Hi Boss, your 20 amp switches will be more than adequate for what you are intending.

As to to spikes and surges, this is a real con job in an automotive situations.

Every vehicle get spikes all the time your motor is running and you never hear of anyone’s ECU/computers being destroyed.

A lot of salesmen try to make out that you need spike and surge protection as means of making their products sound like they are something special or that the salesman knows something about and area they quiet obviously know absolutely nothing about.

Every single electronic device in your vehicle is manufactured with built-in spike protection already so don’t concern yourself about something that is no more than a sales gimmick.

As to surge protection, if you were talking about 240 VAC applications then yes you need surge protection but again in automotive DC applications, the only time you could have a surge problem is if your alternator started turning out 18 or 20 volts instead of 12v or a battery charger connected to your battery did the same, and in either case, your can’t protect against such surges, so again, don’t worry about it, it’s just a sales gimmick.
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Reply By: Member - John and Val - Sunday, Jan 24, 2010 at 07:41

Sunday, Jan 24, 2010 at 07:41
Your proposal sounds good. Just a couple of comments -

Most importantly, the wire from the front to the back should be good solid copper, better still, run two wires with one of them dedicated to the fridge. (Voltage losses in the cable are unavoidable but should be minimised for the sake of the fridge. By giving it a dedicated cable, other loads won't interfere with it.) Also to avoid loss of voltage, ensure you have a good earth connection to the vehicle at the back.

There should be a fuse or circuit breaker (don't need both) close to the battery to feed the cable/s running to the back. I wouldn't be too fussed about individual fuses for the back outlets - it's a minor convenience not to have everything close down if there is a disaster on one outlet, but in my opinion the extra complexity isn't justified. KISS - keep it simple. The more bits there are to shake apart on corrugations the less reliable is your system.

20A toggle switches sound good, though again, do you really need them? I wouldn't switch the fridge line. In our rig I've used cigarette lighter outlets for all lighting and general use - pull the plug out a few millimetres and it's switched off, push it in and it's on. For any fixed lights I'd use switches, otherwise less things to go wrong if you avoid them.

You might get some ideas from our blog Electricity for Camping.

Surge protection - surges shouldn't be a concern. kiss!!

In-line discharge protection - This amounts to switching everything (including the fridge) off unless the engine is running. Essential if you are running a second battery, but do you want the fridge turned off? I'd suggest that a second battery might be pretty high on the priority list, but until then simply be mindful of the fact that you are using your starting battery and won't travel far if you use too much!!

HTH


John
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Follow Up By: drivesafe - Sunday, Jan 24, 2010 at 08:17

Sunday, Jan 24, 2010 at 08:17
Hi John, mate I think you need to read through your post you have the link to.

You will find only a very small percentage of AGM batteries can be charged with 15 volts and the vast majority MUST NOT be charged with anything higher than 14.4v

On the other hand, flooded wet cell batteries can be charged with 14.7v and get short periods of boost voltages of up to 15+ volts, as done by many battery chargers, to equalise the cells in a flooded wet cell battery.
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Follow Up By: Member - John and Val - Sunday, Jan 24, 2010 at 08:56

Sunday, Jan 24, 2010 at 08:56
Thanks Drivesafe - You're quite right. The blog has suffered a bit from too many minor edits. The higher voltages required for calcium doped batteries got tangled up with a discussion of AGMs. I've amended the text.

Thank you for your input. I'd appreciate any other comments you'd care to make - MM me if you see anything else that's a bit off!!


Cheers

John
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Follow Up By: The Boss - Sunday, Jan 24, 2010 at 16:37

Sunday, Jan 24, 2010 at 16:37
Excellent, thanks for that John. Will take all that in, especially the KISS principal.

Thanks again
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Follow Up By: drivesafe - Monday, Jan 25, 2010 at 08:46

Monday, Jan 25, 2010 at 08:46
Hi John, the only reason I commented was that, going on the rest of your blog, it seemed like an honest mistake.

It’s a good read and it’s nice to see someone who is genuinely writing for the benefit of other RVers and not purely for the benefit of their own pocket.
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Reply By: ABR - SIDEWINDER - Sunday, Jan 24, 2010 at 10:19

Sunday, Jan 24, 2010 at 10:19
Hi TB

Spike protection is used where there are large collapsing magnetic fields like water pumps, large solenoids and most DC motors. It is best to read our newsletter on this to understand it better. Spike-Protection

If your installation is going to be exposed to the weather I would recommend using a component box and sockets with caps / covers.

I don't like switches exposed to UV as they don't last long and will fail. If possible fit switches to your lights rather.

Cable should be at least 6mm2 for what you need but if possible go up one size to 8 B&S or 10mm2.

You will need to fuse each socket at its rated load.



Regards

Derek from ABR
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Follow Up By: drivesafe - Sunday, Jan 24, 2010 at 11:15

Sunday, Jan 24, 2010 at 11:15
As posted earlier, there is absolutely no reason to add a spike suppression devices to ANY AUTOMOTIVE set up.

It’s nothing more than a con job used by unscrupulous salespeople to get extra sales out of unsuspecting customers.

Furthermore that “article “ is nothing more than a fabrication.

If we were to believe such mythical problems actually existed, then tell Derek, why is there not lines of vehicles at every auto electricians and service centre, getting their ECUs replaced.

Heaps of people fit driving lights, compressors and many other after market devices, which are operated by relays and most of these relays have no suppression and no one has any problems what so ever and many people use nothing more than a solenoid as a form of dual battery system and these rarely have any form suppression fitted to them and they have been around for decades and again, no ones having any of these mythical problems you allege to happen.
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Follow Up By: The Boss - Sunday, Jan 24, 2010 at 16:41

Sunday, Jan 24, 2010 at 16:41
Derek, just the man the doctor ordered. I got this idea after seeing that box on your website. Will be putting in an order within next couple of days.

One thing though, is it fine to just have constant power running to the plugs all the time? No chance of losing charge or anything?

Thanks again.

Cheers
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Follow Up By: ABR - SIDEWINDER - Sunday, Jan 24, 2010 at 17:15

Sunday, Jan 24, 2010 at 17:15
Hi TB

The plugs can be live all the time, you will not loose power if nothing is connected just make sure they are correctly fused. I would recommend 10A fuses for the smaller plugs and fuse the main cable at the battery. (40A Maxi fuse will be OK)

Similar to the picture below but the Anderson plug will be also on the cable that is why we up the 20A breaker to a 40A Maxi Fuse. Fit the 10A fuses inside the component box. The reason for the maxi fuse is just in case you decide to plug a compressor or small inverter on this line then it will not trip the 20A breaker.

Ideally to do the job correctly use our TW100 10mm2 twin core solar cable.



If you email me the cable length I will make you a list.
Regards

Derek from ABR

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Follow Up By: The Boss - Monday, Jan 25, 2010 at 01:33

Monday, Jan 25, 2010 at 01:33
Awesome Derek. Thanks alot, got a few other little bits to do on another vehicle so will sort out what i need and let you know.

Once again, absolutely top service from ABR Sidewinder.

Thanks again

Boss
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Follow Up By: Member - Mike DID - Monday, Jan 25, 2010 at 08:47

Monday, Jan 25, 2010 at 08:47
"Spike protection is used where there are large collapsing magnetic fields like water pumps, large solenoids and most DC motors. "

- the biggest solenoid and the biggest DC Motor in any car is the starter motor.

- if the electrics in your car survive the huge surge EVERY time that you switch the starter motor off, then it's a clear indication there's no reason to add any more surge protection.
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Follow Up By: drivesafe - Monday, Jan 25, 2010 at 12:33

Monday, Jan 25, 2010 at 12:33
Right on the money Mike, and you have to be somewhat suspicious of any product where the selling info is based on this sort misleading and scare mongering sales hype, and you then have to consider how much of the rest of the sales hype is true.

Don’t get me wrong, there are a large number of businesses using these sorts of misleading tactics as a means of trying to make their products look better than they really are.

If a product is genuinely good, it will sell itself based on it’s own genuine merits.
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Reply By: Member - bungarra (WA) - Sunday, Jan 24, 2010 at 10:39

Sunday, Jan 24, 2010 at 10:39
I wont add to all the other posts as they all make sense.....one thing I would draw your attention to is the amount of current that Low Voltage Battery protectors / cut outs can draw

These can vary from anywhere between 0.13a/h up to double that...depending upon their design...as some have the relay built in and others have an output to a seperate relay...some can be put in sleep mode and some cant.

Be aware of this as even the lowest draw (such as relay) of say 0.13 ah is equal to 22 ah over a week of stand by if the vehicle is not in use.........a lot of battery reserve sucked out and wasted...........by the second week you could have a battery below the recomended SOD

if the vehicle / battery is not in regular use / or charge i would fit a LVC device that had the ability to go to "sleep mode" and one that had the outlet to power an external relay and fit an isolation switch between it and the external relay that actualy allowed the power through to the accessories to be cut off when not in use.........at least this way the actual LVC that is only monitoring voltage is drawing negiligible power when not needed...(such as parked up for a week etc)...and the relay drawing nothing

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Follow Up By: Member - bungarra (WA) - Sunday, Jan 24, 2010 at 11:12

Sunday, Jan 24, 2010 at 11:12
opps SOD should read SOC
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Follow Up By: The Boss - Sunday, Jan 24, 2010 at 16:35

Sunday, Jan 24, 2010 at 16:35
Thanks Bungarra, i wont worry about the battery protector now anyway. Focus more on getting the dual battery happening i think.

Cheers
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Reply By: Maîneÿ . . .- Monday, Jan 25, 2010 at 10:34

Monday, Jan 25, 2010 at 10:34
You will definitely *NEED* an in-line battery discharge protector, because as you say, you "don't have a dual battery system"

Run the fridge on an independent wiring system.

Maîneÿ . . .
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