Dual Battery isolators

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

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.

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.

Lindie

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



Tjilpi

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.

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.

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

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.

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.

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.

This is all you will need - Hella Master Power Switch
Part# 0-SWHELLA1

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.

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.

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!!

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.