Dual Battery isolators

Submitted: Thursday, Nov 27, 2014 at 09:06
ThreadID: 110260 Views:5102 Replies:15 FollowUps:28
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Hi, I am looking for a good, but not too expensive batterly isolator for under bonnet set up. I don't know much about electrics and the more I read on different isolators the more confused I get. To me they all seem to do the same thing, but some have an override switch, others have a override in a yellow wire (have no idea what they are talking about) and some mentioned they are electronic while others say they are VSR. I thought they are all the same thing, but apparently they are not. My friend got this projecta 150 amp isolator. He paid $185 on ebay for it. There are so many brands on ebay, but are they basically the same thing or are there some that are actually better and why. Please help this very confused camping mum. Any personal experience and recommendations appreciated. We only go on two two week trips each year so I don't want an expensive over kill sitting in my car for the rest of the time.
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Reply By: Frank P (NSW) - Thursday, Nov 27, 2014 at 09:46

Thursday, Nov 27, 2014 at 09:46
Hi Lindie,

A good, smart isolator, which is in fact a "VSR", will cost you between $70 to $190. ABR-Sidewinder is a very reputable business member who advertises on this forum and sells these units. At the other end of the cost scale are items like these. The cheapest one in that list would most likely suit you. They all ($70 or $190) do the same thing.

A smart isolator, or VSR, senses your engine battery voltage and only when it's charged enough after starting does it switch on and direct 12 volt power to your "under bonnet setup".

A simpler solution is a so-called "dumb isolator". They are cheaper, around $20 to $40. They do exactly as the above, but instead of sensing battery voltage to decide when to direct power to other under-bonnet stuff, it does the diversion as soon as you turn the key. The NJ12 and SL-12-100 on this page are examples.

All these isolators can be purchased cheaper on eBay. Some are name brands and just a better deal. Others are rubbish copies. If I were you I'd buy a budget priced item from an Australian supplier so you have realistic after-sales service and recourse in the event of a problem.

It would help if you could tell us what you want your "under bonnet setup" to do. Will it be a dual battery system? Will the isolator be controlling a power outlet at the back of the car? What do you want your system to do?

Cheers


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Follow Up By: Frank P (NSW) - Thursday, Nov 27, 2014 at 09:54

Thursday, Nov 27, 2014 at 09:54
"Will the isolator be controlling a power outlet at the back of the car?"

By that I meant an Anderson outlet to a camper or caravan.
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Follow Up By: vk1dx - Thursday, Nov 27, 2014 at 14:46

Thursday, Nov 27, 2014 at 14:46
Hi Frank

No. The isolator only controls the power between the batteries.

The power for the rear socket should be run from one of the batteries through a fuse or similar over current safety device and then through a new switch and finally to the rear anderson socket. Our anderson socket is powered from the auxilary or as we call it the accessory battery as it powers all the 4WD accessories leaving the original vehicle wiring untouched.

May I suggest that you get an autoelectrician to supply and install both the isolator and the rear anderson socket and wiring. The wire should be a heavy gauge than normal power. I don't know the size myself. The autoelectrician will know the correct size wire. Just check that the wiring is properly shielded and protected as some autoelectricians are not familiar with need for added protection against rodents eating the insulation and from added stone or stick damages etc. It is handy having a shop do it to know that you are protected by their insurance against shoddy amateur work.

Personally we use the Redarc 200 amp isolator with a switch in the cabin to manually connect the extra batteries when extra battery power is needed for winching.
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Follow Up By: Frank P (NSW) - Thursday, Nov 27, 2014 at 15:09

Thursday, Nov 27, 2014 at 15:09
G'day vk1dx,

Yes, I'm aware of what an isolator does in a conventional setup. The opening post didn't describe exactly what Lindie wanted. Some people use an isolator to switch on and off a feed direct from the crank battery/alternator to an Anderson for a caravan or CT (without a second battery in the vehicle). That was the point of my question - to ascertain if that's what she wanted to do.

As for autoelectricians - I'm afraid I don't share your confidence. I have rectified too many installations with undersized cabling, reversed connections, small negative ("you only need a big positive, mate, it's the one that carries all the load") etc.

Yes, Lindie will have use one but I think she should take cable sizes from here and tell the sparkie to use that size.

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Follow Up By: Frank P (NSW) - Thursday, Nov 27, 2014 at 15:25

Thursday, Nov 27, 2014 at 15:25
vk1dx,

"Some people use an isolator to switch on and off a feed direct from the crank battery/alternator to an Anderson"

If you look at Lindie's Reply #10 you can see that's exactly what she wants to do, except the Anderson will be inside the vehicle, not on the towbar.

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Frank
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Follow Up By: vk1dx - Thursday, Nov 27, 2014 at 15:33

Thursday, Nov 27, 2014 at 15:33
Hi Frank I thought that you were asking the question. Ooops

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Follow Up By: get outmore - Sunday, Nov 30, 2014 at 14:02

Sunday, Nov 30, 2014 at 14:02
frank a smart isoltor does not and cannot gauge battery charge in the main battery before switching charge to the aux.
reason being all it will be receiving is the alternator charge volts same as what happens when you put a multi metre on the terminals of a battery with the engine going.
all it does is sense the battery is receiving charge before swithing to charge the aux
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Follow Up By: Frank P (NSW) - Sunday, Nov 30, 2014 at 14:10

Sunday, Nov 30, 2014 at 14:10
G'day get outmore,

Yes, you're right and to my embarassment, I knew that. Very sloppy wording on my part. Too keen to embellish to try to get a point across, I guess.

If you read my blog, please be kind :-)

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Reply By: Allan B (Member, SunCoast) - Thursday, Nov 27, 2014 at 09:53

Thursday, Nov 27, 2014 at 09:53
Hi Lindie,

Electrics can be confusing and there are a lot of options available, some excellent, some not so good.

I would suggest this one from ABR Sidewinder @ $79.95 to be simple and good value. ABR are Business Members on this site with good products and Derek is always ready to assist. They also can supply all the cabling and lugs that you will need. (07) 3890 5899

The override function you refer to is to enable the solenoid to be manually closed in order to have the auxiliary battery assist in cranking. It does not need to be utilised but if it is then the cabling must be heavy enough to carry the starter current.
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Follow Up By: Allan B (Member, SunCoast) - Thursday, Nov 27, 2014 at 10:02

Thursday, Nov 27, 2014 at 10:02
Perhaps I could add that my blog here on wiring diagrams for auxiliary battery systems may assist you. They do refer to Redarc isolators but other brands can be substituted.
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Reply By: Athol W1 - Thursday, Nov 27, 2014 at 09:59

Thursday, Nov 27, 2014 at 09:59
Lindie G
It would help if you could tell us what type (make and model) of vehicle you have, and also what you expect from your dual battery set up.

Basically there are 3 types or methods of isolating your dual battery, firstly by an ignition or accessories operated relay (the cheapest option but not necessarily the best, but work well with Isuzu vehicles), then a Voltage Sensitive Relay (a far better option and works well with most vehicles), and thirdly the DC to DC charging system (Ctec D250 or similar, and can be the better option with some of the later model vehicles where they have a reduced charging voltage as part of their 'fuel saving' technologies, but have a limited charging rate)

For my vehicle I have the Redarc VSR fitted with heavy duty cables (of starter cable size) and I have an over-ride switch so that I can use the auxiliary battery for emergency 'jump starting' without the need to resort to the use of jumper leads, simply flick a switch and start the engine then remember to flick the switch back off.

Hope this helps.
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Follow Up By: Allan B (Member, SunCoast) - Thursday, Nov 27, 2014 at 10:06

Thursday, Nov 27, 2014 at 10:06
Athol, a pushbutton rather than a switch can be a better option for an override so that it cannot be inadvertently left on. Just hold it in during the override starting.
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Follow Up By: Athol W1 - Thursday, Nov 27, 2014 at 10:25

Thursday, Nov 27, 2014 at 10:25
Allan B
Whilst I agree with your comments I deliberately place the switch under bonnet so as no to be too convenient when the issue is a failed starting battery. It does require the act of leaving the driver's seat and opening the bonnet to activate the system, and this inconvenience is enough to prompt the follow up action of battery checking and replacement as necessary.

I have also fitted this system to my sons vehicle, and several others.

Regards
Athol
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Follow Up By: Allan B (Member, SunCoast) - Thursday, Nov 27, 2014 at 10:37

Thursday, Nov 27, 2014 at 10:37
Yeah Athol, I guess you are unlikely to drive off with the bonnet raised! lol

Funny part is that I originally did not install an override function believing that jumper leads from the aux battery would be sufficient.
The first time I needed them I found I could not open the rooftop box whilst under the carport to access the jumpers!
Needless to say, an override was promptly added.
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Reply By: Kumunara (NT) - Thursday, Nov 27, 2014 at 10:04

Thursday, Nov 27, 2014 at 10:04
Lindie

Have a look at the following url
http://www.redarc.com.au/products/category/4wd-sbi-series-dual-battery-isolator/



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Follow Up By: Kumunara (NT) - Thursday, Nov 27, 2014 at 10:25

Thursday, Nov 27, 2014 at 10:25
Lindie

Also look at:
http://www.redarc.com.au/products/category/4wd-dc-battery-chargers/

They are more expensive than the isolators but worth the extra expense.



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Reply By: Allan B (Member, SunCoast) - Thursday, Nov 27, 2014 at 10:27

Thursday, Nov 27, 2014 at 10:27
The term 'VSR' or 'Voltage Sensitive Relay' seems to be increasingly used in this application. It is the wrong terminology and may confuse people into using the wrong product. (Example)

Generally, VSR's are relays with typically 10 Amp contacts and unsuitable for charging auxiliary batteries. They are intended for controlling auxiliary loads to prevent over-discharging the battery.

The better term here is Voltage Sensing Battery Isolators or solenoids.
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Reply By: Lindie G - Thursday, Nov 27, 2014 at 10:57

Thursday, Nov 27, 2014 at 10:57
Wow, thanks for all this super fast replies. I have a 2001 3litre diesel prado (manual) and it will be mainly just to run my 55litre evakool fridgefreezer in the back. Perhaps I could occasionally charge the battery (100amp agm) in my arkpak too? I have a 160watt solar panel that just can't keep up with fridge demand in hot weather. So some people said the dual battery in the car charges quicker if I do a daily trip of a couple of hours. Not sure if this is true? My friend thinks you need half an hour drive daily with his projecta (not tested yet) and other people say it takes 6-8 hours.

So the arkpak will be for our lighting and phones and dual car thingy for fridge.
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Follow Up By: Frank P (NSW) - Thursday, Nov 27, 2014 at 11:36

Thursday, Nov 27, 2014 at 11:36
OK, we have a good starting point.

Firstly, the driving time required to charge a battery depends on what the charging system delivers to the battery and the type and size of the battery and how much it has been discharged. Charging systems vary enormously, from straight alternator feeds (with varying voltages) to DC-DC chargers with varying currents.

An engine battery in good condition will fully re-charge only a few minutes after start-up. A discharged second (camping) battery on the same system may need some hours.

Your 2001 Prado probably has none of the low voltage problems encountered in later models. (subject to verification - anyone?)

If I am correct about your Prado, then if I were you I would install a voltage sensing isolator such as one of those $70-ish ones I linked to in my earlier reply.

I'd run cables from that to a suitable outlet near where you carry your Arkpak so you can plug your Arkpak in to charge it. Anderson plugs are commonly used for this type of thing.

Cable should be at least 8 B&S. As you are charging the Arkpak direct from the alternator voltage drop is an issue, which is addressed by using the largest practically sized cable. I would go for 6 B&S (smaller numbers are bigger cable).

Then make up some kind of lead in minimum 8 B&S cable to go from the Anderson you've just installed to the Arkpak.

This rig will allow the Arkpak to be charged while you drive. If the solar won't keep up you can run your car for a while to top up the Arkpak. Not ideal, but you can do it.

If this turns out not to work properly (ie, not getting enough charge to the Arkpak from the alternator) you could consider, at more $$$, a DC-DC charger. Plug it into the Anderson you've just installed, attach it to the Arkpak and away you go.

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Reply By: The Bantam - Thursday, Nov 27, 2014 at 11:00

Thursday, Nov 27, 2014 at 11:00
YES there are alot of these devices about and they are all trying for some sort of "point of difference"....hence the gratuitous verbege in the sales material.

Lots of people refeer to them as "smart"...mostly they are nothing of the sort, simply switching at preset thresholds.

They don't need to be particularly complicated the task is quite simple.

They are commonly refeered to as Voltage Sensitive Realys....which is pretty discriptive.

without getting into a whole pile of contentious discussion there are 3 main differences.

Current capacity.....there are some on the market with quite low current capacity....as low as 10 or 20 amps......for most dual battery systems you should be looking at at least 100amps.....higher current capacity is always a safer choice.

The voltage thresholds.....most of the mainline VSRs have similar voltage thresholds...though there is some variation, a few are adjustable..and there are some with weird ideas of where the thresholds should be.

Jump start or over ride facility.....some do some don't......the whole point is to stop the start battery getting discharged in the first place ...so the need for a jump start facility is arguable.

If you are charging a caravan battery.....the jump start facility is pointless.


For most people any of the reputable brands will be just fine.

Don't get caught up in all the hype..especially about being microprocessor controlled or being some sort of high technology....they are somple straight forward devices.

Those who have built using some sort of microprocessor will have done so purely for design convieninece, the same function could be achieved with purely analogue electronics.

Redarc would probably be the most popular...purely because of consistent advertising and mass in the market.
The projector ones seem to be fine
There are many good units out there and only a few lemons.

The sidewinder unit is as far as I can see is plain straight forward item, my only beef is the metal casing..thouh some see it as a positive.

Personally I run a BEP marine 100 amp VSR bypassed by a mechanical battery switch for the purpose of winching or may be jump starting.

cheers
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Follow Up By: get outmore - Sunday, Nov 30, 2014 at 14:09

Sunday, Nov 30, 2014 at 14:09
lol voltage sensing relay.
yes definitely a better description of what they do
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Reply By: MEMBER - Darian, SA - Thursday, Nov 27, 2014 at 12:03

Thursday, Nov 27, 2014 at 12:03
Can recommend Surepower as a reliable brand - a very compact unit - I think mine is the 1314 model - its been under the bonnet for many years and I've never had an issue of any sort with it.
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Reply By: HKB Electronics - Thursday, Nov 27, 2014 at 13:24

Thursday, Nov 27, 2014 at 13:24
Also consider the range of Traxide units available at Traxide RV, they may be a bit more expensive but are also designed and manufactured in Australia and have some unique features.

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Reply By: Lindie G - Thursday, Nov 27, 2014 at 14:47

Thursday, Nov 27, 2014 at 14:47
Thanks Frank P and Bantam. Very glad to know that I can just hook my arkpak up via its anderson plug and don't need yet another battery. Also very glad to know that a "microprocessor" isn't that important afterall. Extremely glad to know now that smaller numbers mean bigger cable/wire!! Now just to decide which isolator. Any idea where the fuses should go.?..hubby will have to do the installing.
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Follow Up By: Frank P (NSW) - Thursday, Nov 27, 2014 at 16:17

Thursday, Nov 27, 2014 at 16:17
Lindie,

Here's a sketch of what I think you're asking about.

I'm guessing the cable from the Anderson to the Arkpak is pretty short, so 8 B&S should do for that.

Does the Arkpak have a fuse for its Anderson? If not you should add another fuse to the diagram as close as possible to the Arkpack - in it, or in the 8 B&S cable or as close as possible to the new Anderson in the car, in that order of preference.

The 6 B&S from the Anderson to earth could be 8 if it's short, but I'd prefer 6.

B&S is cable gauge. It is the same as AWG or just "gauge".

If you go with my suggestions for cable size, make sure you ask for 6 and 8 B&S or AWG or gauge and NOT, repeat NOT 6 and 8 millimeter or square millimeter cable, which are other terms often used. Make sure whoever it is you talk to understands your instruction.

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Follow Up By: Allan B (Member, SunCoast) - Thursday, Nov 27, 2014 at 17:20

Thursday, Nov 27, 2014 at 17:20
Lindie,

If you look here you will see the required cable sizes, exactly where to locate the fuses as well as complete wiring diagrams and other information which will assist Hubby.

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Follow Up By: Frank P (NSW) - Thursday, Nov 27, 2014 at 17:54

Thursday, Nov 27, 2014 at 17:54
G'day Allan,

Diagram 3 looks to be the appropriate one. However there appears to be a discrepancy between the labels on the diagram and the text below.

On the diagram the cable size between the crank battery and the remote caravan/CT battery is shown as 4 B&S. In the text below it says 2 B&S, so I'm wondering which is right.

Putting that aside for a minute, as I understand her proposal Lindie's battery will be in her Arkpak in the back of the Prado, a much shorter cable run than to a battery in a caravan or CT. Getting 4 or 2 gauge cable neatly through the car and behind the trim will be a challenge, I suspect. Also, I doubt she'll want the physical size of a large Anderson hanging about there or fastened to the trim. I suppose it could be on a flying lead and tucked away in the jack compartment or similar when not in use.

I understand about cabling back to the battery negative - have done that myself on my rig. Be that as it may, if Hubby uses a chassis return which will just about halve the cable run, do you think that with the battery much closer to the front of the car than would be the case in your diagram 3, they could use 6 B&S for the supply PROVIDED they get a really good, clean connection to a chassis earth near the proposed Anderson?

Cheers

Frank
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Follow Up By: Hoyks - Thursday, Nov 27, 2014 at 18:06

Thursday, Nov 27, 2014 at 18:06
Hi Lindie G, I have basically what Frank P has put here. I too have an Ark pack, but it spends most of it's time in the shed and only goes for occasional trips in the back of the ute when I plug it into the Anderson plug and charge it off the vehicle.

I modified the Ark pack so it has an Anderson plug riveted to the side of the case and hooked up to the internal battery. I then have a 2 foot cable with an Anderson plug on each end to connect it to the vehicle. I did this so the battery box doesn't have cables running off it and is easy to remove/install.

For the controller, I had a Piranha controller in the past and this was a good one, lots of nice lights, it kept the battery charge and I had no issues with it for years and sold it with my old wagon.

Right now I have a cheapie from Supercheap (under $100, even cheaper if you catch them on special) and almost everything you need is in the kit. It is all electronic and sealed, so there are no moving parts like a traditional voltage sensitive relay (VSR) and was very easy to install. It is simply run the cables, install the box, earth the small wire and hook up the cables. I had it in my old ute for 3 years and now it is in my new ute. Budget some extra for fuses and heat shrink. Split tube sleeving and zip ties are a good addition to make it all look neat and stop the cables from chaffing.

**As stated above, because you will have 2 batteries, a heavy duty fuse at each end is a must**
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Follow Up By: Athol W1 - Thursday, Nov 27, 2014 at 18:29

Thursday, Nov 27, 2014 at 18:29
Frank P
If you are using the chassis as a return to battery then you must ensure that there is a good heavy return from the chassis to the battery ( I have seen these to be nothing more than 4mm auto cable), and also I have seen inadequate earth cable from battery to engine. Also be very aware as to the location of any earth attachment to the engine, as it is possible to create stray electrical currents in the engine coolant which can and will destroy alloy cylinder heads and radiators.

Inadequate earth between battery and chassis can result in the return path being via universal joints and/or handbrake cables, neither of which like to carry any electrical current.

Regards
Athol
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Follow Up By: Allan B (Member, SunCoast) - Thursday, Nov 27, 2014 at 19:00

Thursday, Nov 27, 2014 at 19:00
Hi Frank,

Thanks for picking up that error in my blog diagram 3. I have now edited it to be 2 B&S. I am rather conservative on cable sizes as I deplore cable voltage losses so if pressed for cash or space, it would be OK to go smaller by one or two gauge sizes.

Lindie has not been very specific in her battery arrangements but I believe that she is describing a cranking battery, an auxiliary battery located probably in the engine bay, and an Arkpak in the vehicle rear.
If so, then my diagram 2 would be appropriate but with the addition of the Anderson plug in the rear of the vehicle to connect the Arkpak.
Diagram 3 is for an auxiliary battery in a trailer so cable sizes are larger because of the longer route. Even if Lindie is using only a cranking battery plus the Arkpak in the rear, Diagram 2 would still be applicable with the addition of an Anderson plug to connect to the Arkpak.
For a cable run from the engine bay to the rear of the vehicle I would recommend no less than 6 B&S as it has to supply the fridge as well as charge the Arkpak. A voltage drop of as small as 0.5v in this cable would seriously limit charging of the auxiliary battery.

Your proposal of a flying Anderson lead for the Arkpak is a good idea.

I would never recommend using chassis or body return for any auxiliary circuits, particularly those carrying charging currents. The steel resistance and more particularly, the joints and connections in this path add losses and reduce reliability. Vehicle manufacturers use chassis return to save costs but it is not best practice. Incidentally, I never return the negatives to the battery terminal, always to the point where the battery connects to the bodywork, leaving just the single original cable on the battery terminal.

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Allan

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Follow Up By: Frank P (NSW) - Thursday, Nov 27, 2014 at 19:09

Thursday, Nov 27, 2014 at 19:09
Hi Athol, thanks for your follow-up.

Yes, I am aware of those considerations and that is exactly the reason I have cabled my negatives back to the battery.

However most professionally installed systems use a chassis earth. Not saying that because professionals do it that way, that's the way it should be done. Just an observation. And because it is widely accepted, and if done properly, it seemed a reasonable suggestion for a budget installation in an older vehicle, as the OP has asked for.

Interestingly, I have been made aware that some late model vehicle breeds prohibit negatives being run to the battery. Instead they MUST go to chassis. Something to do with ECU controlled alternators, current sensing and load management.

Lindie and Hubby, pay attention to the points Athol made about good clean adequately sized earthing between battery and chassis and the negative path between engine and battery. Those are definitely part of the equation.

Cheers
FrankP

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Reply By: Rod W - Thursday, Nov 27, 2014 at 15:11

Thursday, Nov 27, 2014 at 15:11
This is all you will need - Hella Master Power Switch
Part# 0-SWHELLA1
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Reply By: Gronk - Thursday, Nov 27, 2014 at 16:00

Thursday, Nov 27, 2014 at 16:00
Had one of these in the 4wd when I bought it.....GSL isolator 100A....made in Australia, can be bought for as little as $65.

No complaints about it's performance.
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Reply By: Tony F8 - Thursday, Nov 27, 2014 at 19:48

Thursday, Nov 27, 2014 at 19:48
Allan B is a guru when it comes to electronics, and knows what he is talking about, we don't always see eye to eye, but with electrics I would take his advice, cheers Allan.
Tony F8.
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Follow Up By: Allan B (Member, SunCoast) - Thursday, Nov 27, 2014 at 20:34

Thursday, Nov 27, 2014 at 20:34
Cheers Tony.
Cheers
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Reply By: Lindie G - Friday, Nov 28, 2014 at 07:51

Friday, Nov 28, 2014 at 07:51
Thanks for the very useful advice. I have bought the abr sidwinder kit from the recommended person. Will definately stand with phone with all this info and diagrams next to husband when he will install it next weekend. Will definately have the anderson plug going into the arkpak. Wont have another battery under bonnet.
Very excited!!
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Follow Up By: Allan B (Member, SunCoast) - Friday, Nov 28, 2014 at 08:34

Friday, Nov 28, 2014 at 08:34
You were right about the batteries Frank. My Diagram 2 still would be appropriate but with the addition of your Anderson plug at the Arkpak.
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Reply By: brendan l4 - Friday, Nov 28, 2014 at 19:42

Friday, Nov 28, 2014 at 19:42
You cant go past the c-tek dual250s. For 300 odd bucks its an isolater, a charger and a solar mppt controller. I wouldn't waste your money on anything else.
You need a dc-dc charger to fully charge a deep cycle battery. The alternator will not charge your battery to 100%, because it needs a multi stage charge. Eg bulk, absorption and float stages etc.
Therefore if its not getting a full charge it will lead to premature battery failure=more money.
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Follow Up By: The Bantam - Sunday, Nov 30, 2014 at 19:11

Sunday, Nov 30, 2014 at 19:11
OH here we go again.
You DO NOT need a DC to DC charger to fully charge a battery.

You DO NOT need a multi stage charger to fully charge a battery.

You need TIME and the sufficient voltage to fully charge a battery, and in some situations a DC to DC charger will take more time than a straight forward voltage sensitive relay.

With fixed mains powered charger having a fixed open circuit terminal voltage of 13.8 volts.....the battery will move thru bulk, absorbtion and float charging phases...with no smarts and no changes in terminal voltage apart from that braught on by the current limiting in the charger......batteries just work that way.

I have yet to find one single manufacturer of batteries that says their 12 volt lead acid battery will not fully charge from a 13.8 volt fixed voltage charger.

A good multistage charger MAY stick charge to a battery faster and more efficiently that a similar sized fixed charger.

BUT

A multi stage charger IS NOT required to fully charge ANY lead acid family battery.

cheers



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Follow Up By: Rimsky C - Tuesday, Dec 02, 2014 at 02:15

Tuesday, Dec 02, 2014 at 02:15
Whether a DC DC Charger is better depends on the chemistry of the battery. If it is a calcium battery then yes, a DC DC charger is better since it will charge it completely full instead of 70 to 80 percent full using a normal alternator.

This also depends on the voltage drop in the wire, and how good the installation is. In my opinion, a good installation is more important that how expensive or how good the device is.
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Follow Up By: The Bantam - Tuesday, Dec 02, 2014 at 11:03

Tuesday, Dec 02, 2014 at 11:03
Show me one single battery spec sheet that says that a lead acid family battery will not fully charge from 13.8 volts given appropriate time.

As far as this whole calcium thing.....pretty well all but the lowest grade batteries these days will have some calcium in their plates and appart from a few specific exceptions all sealed batteries have calcuim in their plates.

Failures to charge batteries generally come in to three groups.
Insufficient time
insufficinet voltage
inadequate wire

While in some situations a DC to DC charger may be advantageous.....I do not believe there is a single case where a failure to fully charge a battery is due to any other cause than the 3 listed above.

Mostly modern sealed batteries of all types will happily charge long term from voltages in the 14.2 to 14.5 volt range......of course this will accelerate the charge rate, particularly in the latter part of the charge cycle......but you do not need a dc to dc charger to achieve this.

There are no simple rules to apply that will determine that a DC to DC charger will be of advantage...there are many factors of the installation that come into play.

OH and there most certainly is not any specific figure, of what state of charge can be achieved without a DC to DC charger....This 70 to 80% figure or whatever someone quotes at the time, has just been pulled out of the air.

cheers
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Follow Up By: Allan B (Member, SunCoast) - Tuesday, Dec 02, 2014 at 11:51

Tuesday, Dec 02, 2014 at 11:51
I have to agree with Bantam on his comments.

In particular on the calcium subject.
Some time ago calcium was added to the plates to increase strength and durability. As with anything new, the Advertising Dept promoted calcium as a great new development in their particular batteries with overstated claims that spawned many myths. Any expressions of revised battery management were probably calculated to reinforce the concept that calcium was something exceptional.

The simple truth is that whilst calcium addition is a minor improvement, it does not change the battery chemistry nor does it require any change in battery maintenance or charging management.

As Bantam has said, these days virtually all lead acid batteries contain calcium.
Cheers
Allan

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Follow Up By: The Bantam - Tuesday, Dec 02, 2014 at 12:52

Tuesday, Dec 02, 2014 at 12:52
Yeh from my reading there IS a little more to calcium in lead acid batteries than strength and durability.

My understanding is that calcuim in the plates particularly in hand with changes in electrolite formulation improves nearly every property of a lead acid battery...and these changes do influence charging voltages ( a little).


But lets not let the good facts about battery chemistry get confuesd with the hype, puffery, miss-information and outright lies that come from those selling very expensive batteries and charging equipment.

If you want to read about multi-stage charging FACTS, go to the web sites of the major battery manufacturers (those who own factories).

There are some very good and very thorough discussions on the matter.......and there is not a single jot of this technology that is particularly new....even the term AGM is quite new in comparison to the technology it discribes.

cheers
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