Dual Batteries in Parallel

[gemoc1]

Gday, the maverick i just bought has a dual battery setup with two batteries in parallel.
Hence, when its running both batteries are charging and both batteries voltage is used entirely when starting the car.
What would be the best way of rigging up my own switch (at a small budget), so i can select which battery i want being used and when??
ie: one battery for accessories and one for just starting and lights etc.

Cheers

[Drewboyaus]

In my opinion, you'd be better off with a smart solenoid similar to the SBI12 that Redarc make.

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[Cuppa]

Gday, the maverick i just bought has a dual battery setup with two batteries in parallel.
Hence, when its running both batteries are charging and both batteries voltage is used entirely when starting the car.
What would be the best way of rigging up my own switch (at a small budget), so i can select which battery i want being used and when??
ie: one battery for accessories and one for just starting and lights etc.

Cheers

As Drewboy says, a smart solenoid ((Voltage Sensitive Relay-VSR) is the way to go. It allows the 2nd battery to be charged but prevents the starter battery being discharged. Unfortunately you just missed someone selling one here - I think it went (used) for $40 or $50. There are other ways, but this is the best fit & forget budget option.

http://www.ebay.com.au/itm/REDARC-SBI12-DUAL-BATTERY-BATTERIES-12V-12-VOLT-CHARGER-SOLINOID-ISOLATOR-DM-/300823256749?pt=AU_Car_Parts_Accessories&hash=item460a769ead

You can get one a bit cheaper on from other sellers on Ebay, but if you buy from a non authorised Redarc reseller you will have no warranty. This seller is an authorised reseller.

[gemoc1]

gee thanks mate, that redarc isolator looks pretty sweet, would that allow me to manually select what battery i want to use?? Say for example i wanted the spotties on when the car is off and i only want the auxiliary battery performing this task

[Drewboyaus]

gee thanks mate, that redarc isolator looks pretty sweet, would that allow me to manually select what battery i want to use?? Say for example i wanted the spotties on when the car is off and i only want the auxiliary battery performing this task

No mate, you wire the accessories you want to the aux battery (fridge, lights, radio, etc.) and use what you want, when you want. The VSR acts to protect the main battery from complete discharge.
It makes sure the main battery is charged first too before allowing the second battery to charge.
The Redarc model also allows you to connect the two batteries to jumpstart the car in the case you manage to flatten your main cranking battery.

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[macca]

A bit off and on topic at the same time!

With a DCDC1240 can you run 2 auxiliary batteries in parallel permanently?

TheY will need to be identical and the same age I'm guessing. And all connections good with all cables the same length in the perfect world?

Cuppa, You have 3 set up like that? or are they separate?

[Crate]

If you want the really really simple solution, I have my batteries connected with 50mm^2 cable and one of these on the positive line:

http://www.ebay.com.au/itm/Battery-Isolator-Key-Switch-/221368987585?_trksid=p2054897.l4275

Means I can manually switch between having both connected together in parallel or two separate batteries.

[4bye4]

If you connect two batteries without a VSR of some type, and one battery develops a fault, it may suck the good battery dry and also can damage your alternator and charge system. Best to fit a VSR.

[Cuppa]

A bit off and on topic at the same time!

With a DCDC1240 can you run 2 auxiliary batteries in parallel permanently?

TheY will need to be identical and the same age I'm guessing. And all connections good with all cables the same length in the perfect world?

Cuppa, You have 3 set up like that? or are they separate?

Yes you can Macca. Once the aux batteries are connected together in parallel the BCDC (or any charger) simply sees them as a single battery.
Paralleling any batteries it is best that they be the same & of the same age ............. however I had a pair of wet starter batteries paralleled to a pair of similar, (but not identical) sized AGM batteries via a Redarc VSR (24v system) for about 5 years. The wet starters were not new when I first did this the AGM’s were. Those AGMs are now paralleled with Optima Yellowtop AGM starters & are over 8 years old & still going strong...... which just goes to prove that less than ideal can work ok in the real world. The only issue I found with having wet & AGM paralleled together was that the self discharge rate of the wets was far greater than the AGM’s , & that they would drag the AGM voltage down with them. This wasn’t a problem as the VSR ‘protected’ the AGMs to a sufficient extent, but this would not be the case in what you are talking about.

If both batteries are the same size, with much the same charging requirements, & one were, say a year old & the other new it wouldn’t concern me. Different brands is also not really an issue as long as the charging requirements are close. But if one is 4 years old & the other new, I’d get a second new one, take the 4 year old one out, charge it now & again, & keep it for jump starting at home, or some other purpose. (I got years more out of a knackered wet deep cycle using it to power an electric fence :) )

[Cuppa]

If you want the really really simple solution, I have my batteries connected with 50mm^2 cable and one of these on the positive line:

http://www.ebay.com.au/itm/Battery-Isolator-Key-Switch-/221368987585?_trksid=p2054897.l4275 (http://rover.ebay.com/rover/1/705-53470-19255-0/1?campid=5336709507&toolid=10001&mpre=http%3A%2F%2Frover.ebay.com%2Frover%2F1%2F705-53470-19255-0%2F1%3Fcampid%3D5336709507%26amp%3Btoolid%3D10001 %26amp%3Bmpre%3Dhttp%253A%252F%252Frover.ebay.com% 252Frover%252F1%252F705-53470-19255-0%252F1%253Fcampid%253D5336709507%2526amp%253Btool id%253D10001%2526amp%253Bmpre%253Dhttp%25253A%2525 2F%25252Fwww.ebay.com.au%25252Fitm%25252FBattery-Isolator-Key-Switch-%25252F221368987585%25253F_trksid%25253Dp2054897.l 4275)

Means I can manually switch between having both connected together in parallel or two separate batteries.


If Yendor is reading this he might comment.
For my part I think there may be dangers with this setup. Ok when switching whilst engine not running, but I’d wonder if it could cause damage to the alternator if switched whilst the engine is running. And you’d only need to forget once. I can’t quite recall the details, but know that in my system I can bypass the the BCDC1240 charger & connect my aux battery bank direct to the starter battery if I choose. This essentially replicates what you are doing...... BUT ..... I was advised to fit a ‘Break before make’ switch to achieve this - it is a 3 position marine type switch. (ON/OFF/ON) This is to avoid damage to the alternator I believe.

[bigkevlittletruck]

As already the best way is to use a vsr and hook your acc to the second battery
. Its the simplest and cost affective an alternater that's allowed to run open circuit can triple its rated voltage in just few seconds .not good for your electrical system

[threedogs]

I have a few brand new finned alloy boxes with 3 terminals on them, I used one years and years ago on my ute to run a second battery.
Only just sitting here any idea what they are worth? $50, they are new,
Ill grab a pic

[Cuppa]

I have a few brand new finned alloy boxes with 3 terminals on them, I used one years and years ago on my ute to run a second battery.
Only just sitting here any idea what they are worth? $50, they are new,
Ill grab a pic

I just did a quick bit of ‘research’ on those isolators TD. Powertech is Jaycar’s brand, some of which is very good. They no longer sell them, & I reckon the best you can do with them is to bin them.

Have a read of this ExplorOz forum thread. (Peter D & Drivesafe are blokes who know their stuff ). http://www.exploroz.com/Forum/Topic/42594/Jaycar_Dual_battery_isolator.aspx

It was a good thought to help someone to save a few bucks, but they are completely different products to the likes of the Redarc isolators, & basically almost useless. Even if given away they would be a disappointment.

[macca]

Thanks Cuppa, I had a feeling that is how yours works. I'm after a bit more capacity for the accessories without complicating things any more than they are.
Even thinking of removing the 2nd battery from under the bonnet as it is only a backup now if the cranker fails and winching when they are joined, heavy thing to carry when a tow start works well! Don't use the winch much and it runs fine off the cranker anyway.
Food for thought.

[Crate]

Not that I am the best with electricity, but not sure how adding another battery in can stuff a alternator? Certainly haven't had any problems with my holden 5l alternator, perhaps the new smart ones are a bit more sensitive..

[Drewboyaus]

Not that I am the best with electricity, but not sure how adding another battery in can stuff a alternator? Certainly haven't had any problems with my holden 5l alternator, perhaps the new smart ones are a bit more sensitive..

I think it's more the open circuit that might be created if switching between batteries on the fly and the potential for increased voltage through said circuit....

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[Crate]

Can never be a open circuit, alternator is directly connected to the primary battery, switch is on the positive cable between the secondary battery and the primary, so you are just adding the secondary battery to the primary. If the batteries happen to have significantly different voltages there will be a change in load on the alternator, but probably no different to turning a winch on and off and loading and unloading the system.

[Cuppa]

I think it's more the open circuit that might be created if switching between batteries on the fly and the potential for increased voltage through said circuit....

Sent from my iPhone using Forum Runner


That’s my understanding too. No probs if switching when motor not running.

See the first paragraph in this link http://constructionmanuals.tpub.com/14273/css/14273_51.htm

The ON/OFF/ON description of my switch I gave earlier was a bit misleading. It is an ON/OFF/ON switch, but also has a feature called ‘Alternator Field Disconnect’ which protects the diodes in the alternator in the event of the switch being switched to off position whilst the engine is running.

https://www.bluesea.com/products/11001/e-Series_Selector_3_Position_Battery_Switch_with_AFD


Edit. Just read your 8.30pm post Crate. My apology, you are correct. I had thought you were switching between batteries, as opposed to switching to add a second to the first. An important distinction.

[Crate]

Ok now I understand where you are coming from cuppa, yes certainly that would be very bad for the alternator! It all makes sense now :-)

[MudRunnerTD]

As Drewboy says, a smart solenoid ((Voltage Sensitive Relay-VSR) is the way to go. It allows the 2nd battery to be charged but prevents the starter battery being discharged. Unfortunately you just missed someone selling one here - I think it went (used) for $40 or $50. There are other ways, but this is the best fit & forget budget option.

http://www.ebay.com.au/itm/REDARC-SBI12-DUAL-BATTERY-BATTERIES-12V-12-VOLT-CHARGER-SOLINOID-ISOLATOR-DM-/300823256749?pt=AU_Car_Parts_Accessories&hash=item460a769ead

You can get one a bit cheaper on from other sellers on Ebay, but if you buy from a non authorised Redarc reseller you will have no warranty. This seller is an authorised reseller.

I have one of these on the GQ that I will be stripping off the car this weekend. I have removed my dual battery system completely and going to a single battery because I am adding a 24v system to the car for winching.

I would be happy to post it to the OP for $50.

[Cuppa]

There ya go gemoc1........ the power of the forum community. :)

[gemoc1]

Yeah i like the idea of the isolator doing everything automatically, but still would be sweet to have a manual override incase i need it

[the evil twin]

Yeah i like the idea of the isolator doing everything automatically, but still would be sweet to have a manual override incase i need it

Almost al of the VSR style Isolators come wired for a manual override.

This can be a switch on the dash (say $10) if you prefer or simply connecting two wires bayonet plug style under the bonnet (say 50 cents) when required and disconnecting when finished.

[Cuppa]

Almost al of the VSR style Isolators come wired for a manual override.



And MudRunner’s one will do exactly that. :)

[gemoc1]

Yeah my boat is fitted with dual batteries and the (ON/BOTH/ON) style switch and this is kind of what i was thinking to do with the patrol, but then again the idea of an isolator doing it for me is very intriguing

[gemoc1]

Yep, i think the evil twin has got me set on a VSR style isolator haha! Great help thanks heaps guys

[moza]

if you use a victron or baintech vsr they have a overide switch function so if you do flatten your crank battery flick the switch it will link both and you can start

[Bruce McGregor]

The solution to this query is a Cole Hershey marine battery switch.
It has four positions.
Position 1 = battery 1
Position 2 = battery 2
Position 3 = battery 1 & battery 2
Position 4 = both batteries disconnected

[the evil twin]

The solution to this query is a Cole Hershey marine battery switch.
It has four positions.
Position 1 = battery 1
Position 2 = battery 2
Position 3 = battery 1 & battery 2
Position 4 = both batteries disconnected

Uuummm... no it isn't.

The OP wants one battery for SLI and not auxiliary loads and one battery for auxilliary loads and not SLI.
A Cole Hersey will not do that.
With a Cole Hersey, one battery does everything, the other battery does everything or both batteries do everything