Dual Batteries for dummies

[martynvella]

not spill as such i think just swell up and expand and may split but thats just what the batteryworld guy told me. iv'e had auto elecs tell me agm's are fine under the bonnet as long as there not near the exhaust. can you still crank off a flooded battery

Flooded gell agm or whatever, if you get a dual purpose it will crank as well.

You have been working on this set up since august, just buy a battery or your ute will be worn out before you ever finish it. If you go to 10 different battery shops they will all tell you to buy the battery that they make the most profit on, which isn't necessarily going to be the best battery for you, you have asked about every question there is to ask about batteries, you have a redard bcdc so that money will have been wasted if you go for a conventional battery but that's up to your budget. Use what you have learned and buy a battery.

Last bit of advise, don't buy the battery till you are going to use it the first time, if it sits in there for a year before you need it that will be a year less, maybe more, it will last when you are using it.

How long did it take you to decide what ute to buy??

[Richolux150]

VSR's alone wont charge your AGM.........most require 14.4V to charge em properly.........my Hilux alternator will only charge at a maximum of 13.6V.....so a unit like the Redarc bcdc.......or Ctek with a solar input is money well spent....given that Ctek 205s are only about $260 online.....

I notice that the Optima batteries FAQ page says charging requirements are 13.65 to 15 volts........my volt meter on the crank battery at a max says it is providing 13.6 v so a VSR will only provide 13.6.....that is below the minimum requirements specified by Optima, thats were I sourced my info.......

[TOYZX]

Give a break! He can take as bloody long as he likes and ask as many questions as he likes, that's the beauty of this site. Any wonder people leave the site when they get told like that!

[rds_929]

Give a break! He can take as bloody long as he likes and ask as many questions as he likes, that's the beauty of this site. Any wonder people leave the site when they get told like that!

yeah cheers toy some people are more helpful than others. there is plenty of useful knowledge on here and its great for people like me who are only new into the 4x4 scene. but some people have to much time on their hands and just type crap if it's not constructive why bother ??

[Moiv]

I was in a similar position to you last year before I did mine.

What Martyn is getting at is everyone has their beliefs on batteries (and charging systems), and the more people you ask for advise the more different answers you're going to get and you'll just end up going around in circles. In the end you just have to bite the bullet and buy something.

I think the answers to all your questions are already in this thread. If not, a bit (not much) of google research will fill in the missing pieces.

If you were putting it in the tub I'd say get the biggest AGM you can afford (within reason).
Under the bonnet most AGM's will have a void waranty (optima is ok though), they'll probably still be fine in a diesel hilux, just watch the weight. If you want cheaper then get a flooded, that will give you between 1-3 years to consider if you want AGM next time.

Most AGM's you can crank off, they will just have a weaker delivery of burst power.

Not sure what other questions you have?

[rds_929]

prob no more questions for the minute was just finding it so confusing every different person i asked gave me a different answer (red arc , batteryworld , auto elec , century) i think for my application a flooded will do well under the bonnet for running my accessories and maybe next time round i can give an agm a crack if need be cheers

[martynvella]

Apologies for any offence I may have created, I have been known to get a bit short before where I should have kept my mouth shut, but hey, bet it isn't the last time.

Batteries are a minefield, but as with anything if you are around before any variants come along and you study the variants as they come along so you understand what the differences are and what they actually do differently it all fits into place, but come along 35 years after the changes start it is very confusing and you are at the mercy of the sales people who are trained to maximize profits with whatever products they have on hand. If you understand a few basics you will easily be able to choose the right battery for your needs.

How many of us have been talking to a battery salesman and they throw in the term VRLA to confuse you and throw you off track, it means nothing for any practical reason, just a term they use because most people have no idea what it means and it makes the salesman seem to be in the know.

If anyone is interested I will do a thread on batteries as I understand them, but I can bet within a couple of weeks there will be people asking the same questions again.

[incman]

Outback Joe did a comprehensive job on this area. Here's a snippet

DC-DC Converter Myths

I’ve noticed a lot of misinformation about DC-DC converters so I’ve added this section to help clear the water. The most commonly reported myth is that your alternator cannot fully charge a battery. Often a figure of 80% is quoted as the maximum charge that an alternator can provide, but I’ve seen figures as wild as 60% being reported. I have found exactly zero substantiated references to support these claims. I have seen exactly zero adequate explanations to support these claims. It’s not true. I think it originated from DC-DC converter vendors and perpetuates with those who have one in their setup. In reality any voltage above the voltage dictated by the battery’s chemistry will charge the battery to 100%. You can verify this by looking at charge characteristic curves on battery datasheets – the capacity approaches 100% for any charge voltage. It is true that the final portion of charging will be slow from an alternator. An elevated voltage will charge the final few % faster and help reduce sulfation.

On average, under cycling conditions, an alternator will provide a greater state of charge. After an overnight discharge, an alternator will charge faster than a DC-DC converter during the bulk charge stage. This accounts for most of the battery’s capacity. For a typical AGM battery size of 100Ah , the alternator may charge at say 40A whereas the DC-DC converter will be limited to its rating, typically 20A, or even less at elevated temperatures. With loads like fridges connected, the DC-DC converter will charge the battery even slower as many amps are diverted to the loads, whereas the alternator has excess capacity to supply the loads as well as continue to charge the battery at 40A. So in a typical scenario, driving from camp site A to camp site B, or driving from camp site to fishing spot, or running your motor specifically to top up the batteries, the alternator will be charging over twice as fast as a DC-DC converter – over 20A more current. Unless driving for a very long time, the battery will never be fully charged in this scenario. It is only once the battery is almost fully charged that a DC-DC converter will charge faster than the alternator. On average though, for a typical cycle of the battery, you’ll have more capacity charging from the alternator.

I’ve seen other myths reported about DC-DC converters. For example that they are better for your loads, or provide “better isolation”, or that they help your starter battery charge to a higher capacity or improve longevity in your starter battery. These are all untrue. Disadvantages of DC-DC converter are numerous as illustrated above.

Some claim that if cost is not an issue, a DC-DC converter is universally the best solution for a dual battery design. Even with infinite budget, I do not believe this to be the case, although DC-DC converters do have advantages that should be considered. Any design is a compromise.

If your auxiliary battery is able to accept a high charge rate from the alternator and will see regular charging from adequate solar and / or an intelligent mains charger then I prefer the advantages of a dual VSR setup.

Remember, a DC-DC converter is the most expensive solution to join your batteries together. Therefore it is the preferred solution for anyone selling this stuff. Keep this in mind when assessing marketing information.
http://outbackjoe.com/macho-divertissem ... inverters/

[rds_929]

no worries all good mate a thread on batteries would be ace there are so many options and variants out there even a basic guide will help the people with not much knowledge like me

[Rockracing]

Have you guys used or tested these ones out???
Cheaper than other brands and not much more than solenoid

http://m.supercheapauto.com.au/Product/ ... SPO3426474

[Richolux150]

Have you guys used or tested these ones out???
Cheaper than other brands and not much more than solenoid

http://m.supercheapauto.com.au/Product/ ... SPO3426474

http://www.batteriesdirect.com.au/shop/ ... WvAod34YPG

Good examples of a bad argument

[Moiv]

One thing I'll say on the DC-DC charger issue. I've contacted a couple of auto electricians and a battery manufacturer themself and they have all said my hilux putting out 13.6 - 14.0v will charge an agm battery however they DO recommend a maintenance charge with a proper battery charger once a month.
To me that says the alternator cannot on its own keep the battery maintained. So spending the extra money to avoid having to do that maintenance charge (cos I'm forgetful) is worth it

[Moiv]

Also for the best of both worlds, I'm installing a narva dual battery selector switch. So if I'm going for a quick run up the beach after having accessories on all night I can link the batteries to maximise on the larger bulk charge available from the alternator (bypassing the DC-DC charger).

[scratcher]

Outback Joe did a comprehensive job on this area. Here's a snippet

DC-DC Converter Myths

I’ve noticed a lot of misinformation about DC-DC converters.......

Welcome to the internet, full of opinions and not a lot of facts Seriously though, I disagree with outbackjoe on this one (though I must admit his website is very informative generally). It's the age old difference of voltage vs charge, whereby full voltage doesn't equal full charge. Think of every f%$*ked battery you've every had, you can get it to full voltage but it doesn't have the capacity to start the car. Battery death comes from depleting it too many times (not as applicable to deep cycle but still applicable), sulphation is probably the ultimate cause, whereby you can't actually get the chemical reaction a battery relies on. The better charges do the high voltage pulse to get rid of the sulphation, it's not a myth, it's a fact. You can supposedly rebirth a battery by dumping the acid out and using bicarb to clean the sulphation and then epsom salts to replace the acid followed by a long trickle charge (which supposedly then makes a normal battery a deep cycle), but I've never tried it.

The worst thing you can do to a battery is not charge it, but it all depends on the battery, lead acid prefer full charge, nimh prefer no charge and lithium batteries 70%.

Sulphation decreases capacity and an alternator can not reduce sulphation so while outbackjoe is correct that an alternator will fully charge the battery in terms of voltage, but not capacity.

[martynvella]

Lots of differing opinions.

The trouble with sites like Joes is that they try to cover everything, and they do not understand everything so they research it and form their own opinions with no practical experience what so ever and quite often don't get it right in their own heads before they try to preach it to others. That would be like me writing articles an diesel fuel injection after I read a few articles and filled my diesel tank a few times. It takes 4 years to learn a trade and a lifetime to get good at it, not a few hours reading shit on the net.

I was once looking for ideas to improve the operation of a gas fridge in a caravan and found a site of a guy that now does regular columns in 4wd and caravan mags. Thought it was a wealth of info till I read what he put in his brief description of how a cars alternator works..... not even close to right, so how could I still have faith in what he was writing about fridges? This guy still make a living writing stuff that is almost right.

Let go of the idea of turning a starting battery into a deep cycle by adding a few chemicals, the differences are physical as well as chemical.

Sulphation will kill a battery, it is a salt (sulphate) that starts to form as soon as the electrolyte is added to a battery normal use causes this to break up and fall to the bottom of the battery into troughs put there to catch this and other chemicals that come away from the plates. If a battery is left unused for an extended period this sulphate gets too thick and strong to break up and remains on the plates and insulated them.

Yes products have been sold over the years that will dissolve this but it also interferes with the chemistry of the battery so they are never as good, possibly making them present as a deep cycle because they take longer to charge and can not deliver the high current they once could.

A well maintained conventional battery will eventually die from one of 2 things, the first is metal fatigue where one of the spot welds joining the cells breaks and it is game over all of a sudden, car went from starting normally to nothing at all, the last bump you hit did it. If your lucky this wont cause the battery to explode when you hit the key. Doesn't happen much any more cause the manufacturers had to improve the joins because people were getting injured and suing them.

The other thing is the chemicals that are pressed into the plate grids fall off in normal operation and fill the troughs in the bottom of the battery and either short the bottom of the plates together and render the cell useless, or there just isn't enough material left on the plates to do the job. This is normal aging of a battery and many outside factors influence this such as temperature and vibration.

So called reco batteries these days are batteries that have shorted cells that have been shaken up, emptied and refilled with new electrolyte, what a bargain scoring one of these little gems, 20% of the original plate material if your lucky. Batteries used to be reconditioned by melting the pitch off the top of the hard rubber battery ( which I can bet 90% of you have never seen) and replacing the cell by soldering in a complete new cell. This can not be done with a polly case.

[incman]

But I like the way Joe sums it up, he says every setup has compromises, which is the reality of any setup.

Different strokes for different folks

[Richolux150]

Ahha all I know is 13,6 v at the crank equals 14.4 v at the 2nd run through the DCDC.......Woha white mans magic

[Locknut]

G'day guys a bit of a side subject...

I just installed the InterVolt DCC charger and am very happy with it. Some of the features are:
- 25 amp charging @ 50 degrees (Ctek stops working at 50 degrees, this only reduces amps at 50 up to 85 degrees)
- solar capable
- temporarily submersible (good for the victorian blokes)
- in cab battery monitoring (I have had issues in the past where the unit wasn't working and we were counting on the battery being charged after the six hour drive)
- no ignition lead required
- $545
- ip67, not 65

I'm not saying this is better value for money than the other brands, I'm just saying it's another option other than the two bigger brands and I'm very happy with it. I didn't find a lot of info on the net about this unit so thought I'd offer a bit.

Cheers

[martynvella]

shame it is dearer than redarc.

[martynvella]

it has some interesting refinements and sounds good, but all sales pitches sound good, keep us informed how it performs.

There will always be companies that add bells and whistles to existing products, some people like it and some prefer the out of sight out of mind principle. I rely on the fridge monitor to tell me the voltage of the second battery and the fridge conditions.