Cheap but good dual battery control?

[chimpboy]

I already have dual batteries on my Maverick, using a single VSR.

However I recently found a PRC4427 "voltage sensitive switch" from a landrover discovery in my big box of goodies. It apparently cuts in at 13V and cuts out again at 12.1V, so it would do a decent job as a dual battery controller.

It's not heavy duty at all (1A I think) so you'd need a solenoid of some kind to do the actual switching. Also piss easy to include a manual override on; a simple switch will do.

Anyway, just an idea for anyone who spots a rangie or a disco at a wrecker or whatever; it could cut the price of the dual battery setup a bit.

I guess it could also be used without a second battery eg to let spotlights run until the battery needs to be saved, then cut them off... something like that. Never come back to a flat battery again!

[acebryan]

gday all a good cheap dual battery setup is a $27 dollar solenoid from super cheap. It has 4 prongs on it, 2 big 2 small hook up power off your main battery onto one of the large terminals. Use a small one as your earth. (too be safe run same gauge cable for your earth as your power wire).

The other large terminal to the positive on the second battery, and the other small terminal to your engine on wire (one click after accs). Not accs, other wise when you turn your accs on you will link both batteries and drain them both. Earth out your 2nd battery close to were you place it. I have done this setup 5 times, 3 for myself in different 4x4s, 1 for a mate and 1 for my dad, each time it has cost between $60 and $70 for everything you need. (except the battery).

If hooked up correctly your second battery should be getting 13.4 to 13.7 volts every time you start your car. I had the first one checked with my local auto elecy and he said it is the same as he does but he charges $400 including the battery. It is easy as to install hope this can save everyone some cash cause it has saved me a shit load.

[-Scott-]

gday all a good cheap dual battery setup is a $27 dollar solenoid from super cheap it has 4 prongs on it 2 big 2 small hook up power off your main battery onto on one of the large terminals use a small one as your earth (too be safe run same gauge cable for earth as your power wire) the other large terminal to your second battery and the other small terminal to your engine on wire (one click after accs) not accs other wise when you turn your accs on you will link both batteries and drain them both. Earth out your 2nd battery close to were you place it i have done this setup 5 times 3 for myself in different 4x4s 1 for a mate and 1 for my dad each time it has cost between $60 and $70 for everything you need (except the battery) if hooked up correctly your second battery should be getting 13.4 to 13.7 volts every time you start your car i had the first one checked with my local auto elecy and he said it is the same as he does but he charges $400 with the battery it is easy as to install hope this can save everyone some cash cause it has saved me a shit load.

Mate, welcome to OL, always good to have enthusiastic new members with advice to share.

But PLEASE put a little time into punctuation. You've got some good information in your post, but it's too farkin' hard to read!

Cheers,

Scott

[sierrafreak]

Whats the go with needing puctuation i had no problem reading it maybe cause im not that educated and dont use it myself i find it easy to read do you actualy say full stop or comma when your talking???

No ones ever said anything to me about using "Proper Grammer"when typing something on any forum!!

Just my 2c

[-Scott-]

Whats the go with needing puctuation i had no problem reading it maybe cause im not that educated and dont use it myself i find it easy to read do you actualy say full stop or comma when your talking???

When you're talking you use pauses and inflection - punctuation is the written version.

I read a lot (not just on Outers ) and I find decent punctuation makes a huge difference to readability.

YMMV.

No ones ever said anything to me about using "Proper Grammer"when typing something on any forum!!

Just my 2c

Grammar and punctuation are different things.

[drivesafe]

Hi acebryan and sierrafreak, Scott’s not have a go at you, he was just requesting a clarification of the post.

I’m interested in anything related to this subject but I have also had the same problem as Scott in that I have found the post hard to cypher.

Cheers

[festy]

Oatley electronics sell a kit for around $20 that comes with an 80 amp latching relay. The cut in and out voltages are adjustable, plus it has some handy de-bounce circuitry. By swapping 2 resistors it also makes a great low voltage cutout for fridges etc.
You need to know your way around a soldering iron to build it though, it's a fairly simple kit but you do have to build it yourself.

[smileysmoke]

Oatley electronics sell a kit for around $20 that comes with an 80 amp latching relay. The cut in and out voltages are adjustable, plus it has some handy de-bounce circuitry. By swapping 2 resistors it also makes a great low voltage cutout for fridges etc.
You need to know your way around a soldering iron to build it though, it's a fairly simple kit but you do have to build it yourself.

sounds good mate. do you have a linknto the kit.. would the amperage be enough for a basic dual bat kit?

[chimpboy]

80A is heaps unless you're running something pulling a shiatload of current such as a winch.

[festy]

http://secure.oatleyelectronics.com//pr ... cts_id=270

[sierrafreak]

i still dont think punctuation is an issue its a loud of garbage.
But like i said for an un-educted fark like myself it must have been to easy to read his post just the way i write them.
Another thing is no body has said nothing to me and i dont use PROPER (not sure of spelling) punctuation and have never had a problem!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!11

[chimpboy]

I don't think this debate is worth having, but personally I found Acebryan's post readable both ways, but probably a bit easier to follow with the paragraphs spaced out.

On the specific question of "cheap but good dual battery control", I have no problem with the manual type of system described by Acebryan if that is what people want, but I personally much prefer an automatic system that always protects the cranking battery.

Interestingly if you added the solenoid Acebryan is talking about to a used voltage-sensitive relay from a Rangie or Disco like the one I am talking about, you would have a completely viable dual battery controller much the same as a piranha or whatever, for a shiatload less $$, probably under $35 not counting cable - as long as the Supercheap solenoid doesn't pull more than 1A. Even if it does you just need to add a 30A horn relay for six bucks as well and you're set.

I reckon the pick-a-part type wreckers wouldn't even know what the voltage sensitive relay is, so it wouldn't cost much.

I would probably give this a go if I didn't already have a Matson dual battery system installed.

[festy]

With the cutout voltage of 12.1v, it's going to allow your primary battery to discharge a fair bit before isolating it - down to about 40% of it's capacity.
The Matson (and most others) isolate at 12.6-12.7v, being the float voltage of a fully charged battery.
The Oatley kit is adjustable for the isolate voltage.
There's nothing wrong with setting your isolate voltage lower than 12.6v to get a bit of extra reserve power for fridges etc, but I think 12.1 is a bit low.
If you set it for about 12.45v, that will leave your cranking battery with at least 75% charge for starting your engine.

[drivesafe]

With the cutout voltage of 12.1v, it's going to allow your primary battery to discharge a fair bit before isolating it - down to about 40% of it's capacity.

Actually, there is no problem with taking the cranking battery down to 12.1 volts.

We have been supplying DBS controllers that take the cranking battery down to 12 volts, which just under 50% SoC, for over 18 years and, with the exception of the cranking battery being faulty in the first place, there is still heap of power in reserve to be able to start the most stubborn diesel motor on the coldest morning.

12.1 is fine.

Cheers.

[dmcruising]

i'm looking at doing acebryans system and was also told that if needed i could use the 2nd battery to start the car by a switch. How would i set this up and what i needed. i already have the solenoid, battery and cable (just trying to find a surf airbox to do the 2nd battery in the engine bay ln106 hilux).
thanks in advance for any help.
dave

[acebryan]

Hello dmcruising a friend has put a switch on this set up which uses the normal solenoid you have. It opens the other battery and you can start your car. But not sure how he did it, My advice would be chuck it all in than ask an auto elecy to hook that bit up it shoudn't cost stuff all, let us know how you get on.

[sierrajim]

My advice would be chuck it all in than ask an auto elecy to hook that bit up it shoudn't cost stuff all, let us know how you get on.

Why not advise him to ask those on here that may know how to do such a thing?

(I'm electrically retarded, so don't ask me)

[acebryan]

Sorry i have tried to post to things on this forum and got shoot down twice so whatever i will just keep my ideas to my self...

P.S i forgot to mention that you did so whats it F**KEN matter. Thats the point of this sort of sight to add info others may have forgotten.

[chimpboy]

i'm looking at doing acebryans system and was also told that if needed i could use the 2nd battery to start the car by a switch. How would i set this up and what i needed. i already have the solenoid, battery and cable (just trying to find a surf airbox to do the 2nd battery in the engine bay ln106 hilux).

I haven't used the basic solenoid setup myself, because I don't think it does what a dual battery setup needs to do - ie automatically charging the primary battery fully before charging the secondary battery. There are some situations where you can end up with two flat batteries, which I think defeats the purpose of having dual batteries. I would describe it as a step up from just joining the two batteries together permanently, but not a true dual battery system. I am not shooting anyone down though, I think the basic set-up has some value as a cheap option.

But anyway, if you did want to do what you've described, it's pretty simple. The wire that Acebryan says you should hook up to "ACC" power can also be connected by a switch to battery power. Then when you flick this switch, you trip the solenoid and your two batteries are connected no matter what.

Will this be enough to start your car through? Maybe; normally a two-battery setup uses reasonably heavy, but not incredibly heavy, cable between the two batteries. It's not normally going to be cable that's as heavy as your starter motor cable. It's also a lot longer than your starter motor cable. But it would probably work for an emergency and I would install a switch like that if I were using that system. If your dual-battery cable is as good as a jumper lead then it should do it.

Two things though.

Firstly, if I ever needed to start from my aux battery, I would just use a set of jumper leads across the two batteries, not the dual battery connection. For me this keeps things a bit simpler, and it's crazy not to carry jumper leads in any car imho anyway.

Secondly, I would not install a simple on-off switch for the emergency start situation. I would install a two-position switch as follows:

Terminal 1: Accessories power
Terminal 2: -> to the solenoid
Terminal 3: "always on" battery power

This means that you can switch between the batteries being connected all the time, or only when you have the key turned to Accessories or Ign. This way you won't be sending power back to your accessories from the aux battery when you desperately need all the power to start the car.

Or you could have a three-position switch that gives you a manual "off" position for the solenoid.

Normally you will leave it in the "accessories" position if you want it to work that way. But you can use the "on" position for starting, and the "off" position if your aux battery is very flat, and you don't think you'll be driving for long enough to charge both batteries.

Cheers,

Jason

[drivesafe]

Sorry i have tried to post to things on this forum and got shoot down twice so whatever i will just keep my ideas to my self...

P.S i forgot to mention that you did so whats it F**KEN matter. Thats the point of this sort of sight to add info others may have forgotten.

Hi acebryan, I don’t know why you have your nappy in a knot, anybody can post their ideas here and anybody else can add to that idea or post differing ideas, as long as it’s to the benefit of all the readers I fail to see how this is a problem, furthermore this whole thread has been very gentlemanly and I certainly didn’t see you get shot down, so again, I can’t see what your problem is.

Cheers

[drivesafe]

Hi chimpboy, actually it is only a very few of the top end dual battery systems that fully charge the main battery before charging the auxiliary battery.

Most systems simply monitor the voltage at the main battery and when the voltage rises, indicating the motor is running and there is sufficient power to charge the main battery, the device then cuts in and parallels the batteries to charge the auxiliary battery.

As to why you would need to fully charge the main battery before starting to charge the auxiliary battery is beyond me.

With the exception of vehicles with VERY small alternators the average 4x4 will easily charge two batteries at the same time and most 4x4s will handle the charging of three batteries simultaneously.

Your correct about how these basic solenoid set ups can result in problems if not wired a specific way and the main one is that the cranking battery dies but because the auxiliary battery is now actually the one starting the vehicle, it can be months before you know the main battery is stuffed and the revelation usually comes about because the auxiliary battery spits the dummy as well.

Cheers

[sierrajim]

Sorry i have tried to post to things on this forum and got shoot down twice so whatever i will just keep my ideas to my self...

P.S i forgot to mention that you did so whats it F**KEN matter. Thats the point of this sort of sight to add info others may have forgotten.

Mate,

I think you might be taking things the wrong way, I'm simply stating that instead of telling him to pay someone to do the job he can get some ideas and advice here and do it himself. This Sir is the reason we call these sections "Tech Sections"

[chimpboy]

Hi chimpboy, actually it is only a very few of the top end dual battery systems that fully charge the main battery before charging the auxiliary battery.

Most systems simply monitor the voltage at the main battery and when the voltage rises, indicating the motor is running and there is sufficient power to charge the main battery, the device then cuts in and parallels the batteries to charge the auxiliary battery.

As to why you would need to fully charge the main battery before starting to charge the auxiliary battery is beyond me.

Sorry, I accept that. I should not have said "fully charge", what I really meant was that a typical automatic dual battery system keeps plenty of charge in the main battery before charging the second, and if the second does draw too much power down, then the system disconnects the batteries again until the main battery is well charged again.

With a simple solenoid connected to accessories, your second battery (if flat) could excessively drain your main battery and there's nothing that will automatically stop this.

[drivesafe]

Sorry, I accept that. I should not have said "fully charge", what I really meant was that a typical automatic dual battery system keeps plenty of charge in the main battery before charging the second, and if the second does draw too much power down, then the system disconnects the batteries again until the main battery is well charged again.

Hi again chimpboy, the only time this would happen is if the vehicle is idling or travelling very slowly, say if being used for shooting, other wise the alternator would easily charge both batteries at once.

With a simple solenoid connected to accessories, your second battery (if flat) could excessively drain your main battery and there's nothing that will automatically stop this.

Not quite sure what you mean.

Cheers.

[chimpboy]

Sorry, I accept that. I should not have said "fully charge", what I really meant was that a typical automatic dual battery system keeps plenty of charge in the main battery before charging the second, and if the second does draw too much power down, then the system disconnects the batteries again until the main battery is well charged again.

Hi again chimpboy, the only time this would happen is if the vehicle is idling or travelling very slowly, say if being used for shooting, other wise the alternator would easily charge both batteries at once.

With a simple solenoid connected to accessories, your second battery (if flat) could excessively drain your main battery and there's nothing that will automatically stop this.

Not quite sure what you mean.

I'll defer to your experience on this stuff

[its aford not a nissan]

its always a good idea to top up your batteries with a decent battery charger as the alternator works on volts and stops charging when it reaches its predetermined voltage limit set by the regulator
although the battery may read 14 volts(or whatever) it is not fully charged and our alts are not designed to fully charge a battery


just thought i would throw that in there

[-Scott-]

its always a good idea to top up your batteries with a decent battery charger as the alternator works on volts and stops charging when it reaches its predetermined voltage limit set by the regulator
although the battery may read 14 volts(or whatever) it is not fully charged and our alts are not designed to fully charge a battery


just thought i would throw that in there

No.

Where does this myth come from?

Under some circumstances, some users may find that their alternator never fully recharges their batteries - because they drain the batteries too far, and don't allow the alternator sufficient time to FULLY recharge. Don't take this situation out of context.

For most people, with most vehicles, the alternator WILL fully charge the battery - if given enough time. My Pajero, with factory stock charging system, will fully charge BOTH of my batteries - no problem.

[its aford not a nissan]

its always a good idea to top up your batteries with a decent battery charger as the alternator works on volts and stops charging when it reaches its predetermined voltage limit set by the regulator
although the battery may read 14 volts(or whatever) it is not fully charged and our alts are not designed to fully charge a battery


just thought i would throw that in there

No.

Where does this myth come from?

Under some circumstances, some users may find that their alternator never fully recharges their batteries - because they drain the batteries too far, and don't allow the alternator sufficient time to FULLY recharge. Don't take this situation out of context.

For most people, with most vehicles, the alternator WILL fully charge the battery - if given enough time. My Pajero, with factory stock charging system, will fully charge BOTH of my batteries - no problem.

i would recommend taking your car to an auto elecky and have him test your batteries for state of charge they may seem fully charged but infact they would only be around 75 to 80 percent charged even after a really long drive
if you think about it the alt only puts out power till the voltage reaches the set value /voltage determined by the regulator
a decent battery charger will keep on charging even though the battery has reached 14 volts were an alt will stop charging at this point

[-Scott-]

i would recommend taking your car to an auto elecky and have him test your batteries for state of charge they may seem fully charged but infact they would only be around 75 to 80 percent charged even after a really long drive
if you think about it the alt only puts out power till the voltage reaches the set value /voltage determined by the regulator
a decent battery charger will keep on charging even though the battery has reached 14 volts were an alt will stop charging at this point

No thanks. I'll stick with my electronics degree and years of experience recharging batteries for medical equipment. I think I know how to charge lead acid batteries, and I know when my batteries are charged.

In addition, I can recognise myths on the internet, and I've even followed a few of them back to a common source - which isn't wrong, just mis-interpreted. I can also recognise somebody who DOESN'T know how to charge lead acid batteries, and I get sick of people who DON'T know what they're talking about continuing to perpetuate incorrect advice.

[drivesafe]

No.

Where does this myth come from?

Under some circumstances, some users may find that their alternator never fully recharges their batteries - because they drain the batteries too far, and don't allow the alternator sufficient time to FULLY recharge. Don't take this situation out of context.

For most people, with most vehicles, the alternator WILL fully charge the battery - if given enough time. My Pajero, with factory stock charging system, will fully charge BOTH of my batteries - no problem.

Your a brave person Scott, when I saw the post I had to bite my tongue and ignore it as inevitably it would start the same old argument.

Hi aford, Scott is absolutely correct, this is a MYTH and a myth that has some truth to it but that part of the myth relates to vehicles that are used as shopping trolleys not vehicles that get a few hours constant driving.

Like Scott, I have 20 years experience in the field of designing and manufacturing dual battery controllers and spent a fair amount of time developing these systems around how lead acid batteries and alternators ACTUALLY work not around how many people THINK they work.

There is no reason why a vehicle, with a properly maintained electrical system, can not get ALL the vehicle’s batteries charged to at least 95% SoC using nothing more than it’s alternator.

Cheers.