Dual Battery Systems

[Tyce]

This week we’ll be talking with Alan Johnson from Piranha Offroad Products about dual battery systems. If you remember the Victoria High Country DVD, we had a look at Alan’s highly modified 'Cruiser, which sported an awesome triple battery setup.

Alan’s been involved in this area of the industry for more than 20 years, and is more than happy to answer a few of your questions about how dual battery systems operate, where they’re needed and how they can help you out of a tight spot if your crank battery dies on you. He'll also cover the different aspects and reliability of various setups.

Dual battery setups are essential if you’re keen to get out of the city for a few days or more, and they’re one of the most common 4WD modifications.

[Tyce]

Wow, we've had a great response to the dual battery topic. We'll be sending these questions off to Alan, and you should hear back from him shortly.

In the meantime, keep the questions coming!

[Tyce]

Question:

Steve 80

I bought a Piranha 180 recently and the charge light is on even with the key off. Can anything be done to rectify this? Why would it be on? Doesn't that mean the batteries are linked with the key off also? Also does that system allow for jumping if the main is flat without disconnecting the second battery? Cheers Steve

Answer:

1. The gold glow indicates unit is in sleep mode; The green led light indicates charging is from alternator; The yellow led light indicates charging is from solar panel.

2. If the dull gold glow offends, please return the unit to us a less sensitive led can be installed. This can be done at no charge. The power used in sleep mode is insignificant.

3. No charging is occurring key is OFF.

4. There is no jump start mode in a DBE180s. It is designed to allow power to flow in only one direction Alt – Main – Aux, never from Aux to main. If this did occur, a faulty start battery would be masked by the aux assisting, you would never know. The chances of you getting stuck with a flat pair of batteries are increased, it is sort of useless, and the whole idea is to ensure you can start the truck.

5. To parallel both batteries use:
1. A Jumper leads
2. A winch assist kit

[Tyce]

Question:

Mauchit

Hi, I'm thinking about fitting a dual battery set-up to our Challenger, my main questions would be:-
(1) When are dual battery set-ups required?
(2) What size of second battery is best?
(3) What is the best way of monitoring the batteries?

Cheers
Mike

Answer:

To be able to run a Fridge, camp lighting, etc a dual battery installation is best, as this enables you to install a deep cycle auxiliary battery which is designed to be cycled 100’s of times in the life of the battery, as different from a cranking battery without affecting or compromising the cars starting battery.

The tray will take a 10inch Orbital for an NON ABS vehicle. The largest amp / hour rated battery that will fit in an auxiliary tray is best, also preferable a Gel or maintenance free battery with a fast recharge rate.

A Piranha Battery Monitor either a DBM3 (analogue) or a DBM3D (digital) display only required, however, if an Engel Fridge is been used, a DBM4 Monitor / Protector has additional features such as 10.5 volt fridge cut out and spike protection.

[Tyce]

Question:

Mattyc

Alan, can you tell me why constant duty solenoids are so bad when I have two batteries of the same type, or even different types in my Fourby?

My Surf has factory twin batteries, apparently wired in a funny type of parallel, where they draw off each other but only one battery cranks the engine over. My neighbour, an auto elec for nearly 20 years, has recommended that I go with a constant duty solenoid with the drivers side battery the main, and the passengers side the Aux. But... it feels like when I go to a 4WD store, regardless who it is, I get a brow beating from the rep trying to push me into a "Smart system".

Yet, when I go to an Auto elec I get told that a constant duty solenoid will do the job with ease and not break when i most need it. About the only time that the auto elec's that I've seen recommend a smart jobbie is when you have batteries in a trailer, so you don't try and crank from those ones.

So, my real question I suppose is this. Why is a Smart System better than a solenoid?

Answer:

1. Constant duty solenoid are not bad, if they are used for the right application which is to parallel charge identical batteries. It is the same in principal as simply connecting them together to increase the CCA / amp hour
eg: 2 x N70Z @ 620cca = 1240 CCA 2 x ED5 @ 75 ah = 150 AH
A solenoid is like a jumper lead between 2 identical batteries.

2. The Toyota Surf starts both batteries in parallel, the wire only goes from one battery to the starter, but they are in parallel. If you choose to separate the 2 staring batteries, a solenoid would be required to join them back together during cranking and charging. This is useless as you can’t use the batteries to run lights or fridges, as the combined power is needed for engine starting duties. We would recommend using a N70Z; Optima; Exide Orbital, which offers a much increased CCA for starting. A dissimilar aux. battery could be installed for camping duties. A deep cycle battery needs longer to achieve full charge as the plates are thinker and there is less surface area, there are less of them.

Cranking Battery
More Plates 16/17
Thinner
Charge Time Decreases
Discharge Time Increase
Higher CCA
Lower AMP / Hour
Fast

Deep Cycle
Less Plates
Thinker
Charge Time Increases
Discharge Time Decreases
Lower CCA
Higher AMP / Hour
Slow

When you go to a 4WD specialist, the staff are trying to advise you correctly that a solenoid will probably not perform to your aux battery expectations.

A Smart System charges first the main battery, then the aux in a prioritized manner, offering the unit to charge dissimilar batteries. Where as a Piranha battery management system ie: DBE150S or DBE180S would be ideal for looking after the 2 new dissimilar batteries.

[Tyce]

Question:

ROGQ

Hi...
Am just curious to Alan's setup on the high country dvd. I'm guessing he is running a piranha dbe180 system. Does this system simply parallel the two aux batteries or does it in some way isolate them from each other if one drops below a certain voltage?

Cheers Rohan

Answer:

In the High country DVD, Alan is running a DBE 180s+ System. The DBE180s will charge your batteries separately, if the main volts drop they will isolate. If above 13.4, the main battery charges first, then the Aux in prioritized manner. This system does not parallel two aux batteries.

[Tyce]

Question:

doodz666

Ive just bought an '05 Navara STR petrol with a dual battery set-up and Piranha isolator. I've had no experience with dual batteries before and was wondering if the aux battery can be used to crank if the main has gone flat for some reason.

There doesn't appear to be a manual reversal switch or similar on the isolator, so is it as simple as hooking up jumper leads between the two batteries?

Answer:

Yes, jumper leads or a winch assist kit will do the job; in the unusual situation should the main battery ever fail.

The main purpose of a dual battery system is for the batteries to be separated to do different jobs. The main start battery starts the car, runs the winch. The aux runs fridges, lights, CB, UHF, HF, Phone, Inverters, air compressors, reversing lights, shower pumps, computers, DVD, and any other camping related power requirements.

[Tyce]

Question:

zappulmo

Hello,

I am looking into a dual battery system for my 100 series cruiser personally, as well as for some work cars.

From looking at what has been offered, the Piranha system is one of the few basic units which states that it offers priority charging of either the auxiliary or start battery as required.

In reviewing the circuit diagram of the system on the Piranha website, I do not see how this works. The circuit diagram shows that the alternator is hooked directly to the start battery (the same as for normal solenoid units) and the Piranha unit is hooked between the start and auxiliary battery so that once the start battery is up to full charge, it allows current to flow to the auxiliary battery.

I have only a basic understanding of 12V car systems, but I would have thought that because the alternator is hooked directly to the start battery, once the alternator senses that the start battery is fully charged, it will only provide sufficient current to maintain the required start battery voltage.
As a result, I really would appreciate an explanation of the theory behind how the Piranha system allocates priority charging and how it is different to other systems on the market.

Any advice would be appreciated

Answer:

Yes, the Piranha DBE150 / DBE180S both offer prioritised charging first the main – starting battery then the aux. To explain, in terms of water the alternator is a pump, the start battery is (battery) tank and the aux battery is another tank.

We full the main tank to 99.9 full just before the float valve stops the flow we open a valve to the aux tank the water (power) takes the line of least resistance, hence filling the aux. As the aux fills the float cycle (voltage neg) slows the charge to both.

If we were to parallel the 2 batteries together the fuller main tank could empty into the aux, then both would full together in parallel.

How we are different 11 reasons are:

1. One way flow
2. Current Limiting
3. Easy to install
4. Less joints
5. Can be fitted to any vehicle
6. Battery choice
7. No Interference
8. Spike & Sure protection
9. 100 , 150 , 180 amp capacity
10. Plug in – Monitor plug in / Solar Plug in
11. Warranty – 2 yrs for DBE100s, 3 yrs for DBE150s, 5 yrs for DBE180s

[Tyce]

Question:

ryanhanslo

Hi there. I'm the owner of a 2000 Patrol GU1. I have a dual battery system installed and was wondering if you could tell me what would be involved in installing a 3rd. I really have no preference as to where it lives, just as long as it works.
Thanks.
Ryan

Answer:

In a 2000 GU patrol the aux battery lives half way along the guard on the passenger’s side. This tray takes a 12 inch aux battery. On some patrols there is room for a third battery passenger’s side back corner and some have no room in the engine bay for this third battery.

If you have no room a third battery could live in your trailer or van if you have one. Or perhaps a third battery in the back of the car, however to do this both aux batteries need to be the same, thus your aux battery in the back has to be fully sealed – see Exide Orbital / Optima. Your car aux battery will also have to be the same although they are brilliant batteries spiral would AGM adsorbed glass matt.

[Tyce]

Question:

Gilbo

I am looking to buy a dual Battery management system for by late 2007 model D4D Toyota Prado. However I have seen several posts on the internet that indicate me that the charging voltage for some new vehicles has dropped considerably.

A couple of tests on my vehicle after a bit of running showed a voltage of 13.6 volts. Others I have heard from are getting less than 13.4volts after the engines are run for quite a long time. My investigations seem to indicate that most battery systems change to charge the auxiliary battery at around this level. I am nervous that the auxiliary battery will not charge correctly. Especially when I may only stop for a short period then the relay may not even trip to the auxiliary battery at all.

I have noticed that Redarc have changed their product to trip at lower voltages as a direct result in these changes in charging systems (discussed on their July 2006 newsletter from the company)

Are my concerns unfounded or are there adjustments that can be made to the Piranha products to cover these situations? Everything else I read and hear about the Piranha system makes me think this is the system for me – apart from this voltage cut over situations.

I also talked to a guy the other day (who confused me with science) about the use of ‘Boost Converter’ to increase the amount that a battery can be charged to from a standard car alternator. I didn’t really understand. Are there possibilities using this equipment?

What do I have to do to a standard alternator to get it to charge a battery to close to 100% capacity? I am concerned that I need to run the vehicle for a reasonably long time if I discharged a battery to say 60% (after being in the same camp for a day). How do I get the largest amount of charge into the battery (without doing the battery any harm)?

Thanks for your help

Regards,
Simon

Answer:

Since approximately 1990 the standard accepted industry charge rate has been 14.2 volts

We have spoken to our representative from VACC, they recommended 13.2 -14 volts is a normal rate. We have also spoken to the Marketing Director Australian Pacific of Exide Technologies, he recommends 14.2 volts is a normal rate. We have been trying to contact Toyota Australia and have left messages, but we have not received a response to this date.

A boost converter should not be required unless the battery you choose as your aux has a specific change requirement, ie calcium or spiral AGM that simply go to sleep unless charged at 14.2 volts minimum. Most wet cell batteries will charge at lower voltage, eventually. However, the question is why 13.4 is this in fact correct or is it just your car. Is this a problem specific to one car or is it a Prado problem or is in fact a Toyota standard specification for this vehicle.

If in fact the charge rate is as you indicated is correct, I can not at this point determine, if you have a problem. We will keep you posted.

[Tyce]

That just about wraps it up for questions on Dual Battery Systems, but you can visit the link below to discuss the topic further.

http://www.4wdaction.com.au/forum/showthread.php?p=693757