dual batt. questions

[lufc]

hi all
i have a question regarding dual batterys, i have searched and read lots of other posts but have found no answers
do i need to by a 12v to 12v charger like the ctek D250s which retails for about $300 or do i just by an isolater like this one
http://www.ebay.com.au/itm/DUAL-BATTERY ... %26ps%3D54

i am confused as to what is required, i have been told by freinds that you have to have the 12v to 12v charger, but yesturday i went into battery world and the chap there told me all i need is an isolater.
cash flow is an issue atm so i only want to spend the bare minimum.
i will be using a 100amp battery and mounting it behind the rear seat.

[viking shippy]

With out the 12to12 charger you will never get a full charge into a deep cycle battery..as the alternator doesn't have the power to charge both..the ctech senses what's required and charges accordingly, also has terminals for a solar panel..and will keep your starting battery charged from the panel also. An isolator carnt do that..go for the ctech..I had an isolator and changed to the ctech cause of flat battery's and warm drinks...it's worth the investment..

[biggibbo]

An isolater is all you require. A DC to DC charger does the same job, just a little better in looking after your battery long term.

Essentially they both provide voltage to your second battery, the DC to DC provides specific voltage, the isolater shares the voltage from the alternator.

[lufc]

thanks for the replys.
the guy at batt. world said that a dual battery will never be fully charged unless doing really long trips, he sells the ctek d250s but didnt even recomend that ,he recomended a $170 isolater.
i have bought from this guy before he seams to know what he is talking about but i wanted to hear from guys who have actually done it

[big_bob_thefirst]

If money is an issue, the isolator is the way to go. It would b the "minimum" requirement for a dual bat system. U can just run a wire between the 2 batteries but u run a pretty big risk of not having enough juice to start the truck.

The downside of the just an isolator is that you'll just charge the deep cycle battery to around 80%. The dc to dc chargers claim to charge up to 100%. They also manage the battery charging cycle, which is better for the battery.

[lufc]

If money is an issue, the isolator is the way to go. It would b the "minimum" requirement for a dual bat system. U can just run a wire between the 2 batteries but u run a pretty big risk of not having enough juice to start the truck.

The downside of the just an isolator is that you'll just charge the deep cycle battery to around 80%. The dc to dc chargers claim to charge up to 100%. They also manage the battery charging cycle, which is better for the battery.

the isolaters that i have been looking at make sure the crank battery is charged first, they dont charge the dual battery until the crank battery has reached 13.4 volts

[odie602r]

Val from fridge and Solar (fridge-and-solar.net) advocates that if your cable between start and 2nd battery is 6B&S or larger then it will carry enough current to completely charge the second battery. Thus, an isolator is sufficient.

There certainly seems to be lots of mythology about deep cycle battery charging, wet/dry/agm etc. I've found his information on the website to be useful in de-bunking some of these myths (unless his perspective is part of the mythical world too.....!)

[lufc]

thanks guys
i dont mind spending $300 on a charger if thats what is required but if its not needed i would rather have that money in my pocket.
its a tough one i guess, all those people with chargers are going to say "buy a charger" and all those with just an isolater are going to say "all you need is an isolater"

[hvac guy]

I used to have an isolator
Then I went to the ctek
Batteries hold charge longer fridge runs better

Due to the higher battery voltage from being fully charged

With and isolator when it comes on the start battery charges
the second battery with hi inrush currents before the alternator
Charges both batteries up together.
Which is no good with and agm as it needs a different charge rate.
agm batteries do not like high inrush currents and low charging voltages

In my setup I have my ctek charging 2 100amp hour batteries.
if U live local to green bank I'll show U why U need a ctek

For example when testing I had a fully charged start battery

And half flat second batteries voltage to my ctek was 13.8v (I had lights on etc)
Current was 20amps, voltage out of the ctek was 14.4v at 13amps
A agm battery needs to be charged at 14.4v to charge to 100%

My start battery was charging with 3amp

[viking shippy]

If your battery is in the engine bay and it's just another cranking battery wich will be smaller than the starting battery cause of space.. fit larger cables and the isolator...if your thinking of solar and fitting 200ah/100ah gell battery's in the tub (like mine) or any battery for that mater in the tub you will need the ctech.

[lufc]

ok ,so if i buy the ctek charger do i still need an isolater or does the ctek d250s do it all

[viking shippy]

Ctech does il all
Have a look under ctech on this site

[daryn]

With the ML you could get away with just an isolator, with my pajero the alternator actually senses what voltage is needed to send to the main battery to keep it charged, as such I basically had no choice but to get the ctek d250s.

If the MN, being the newer model, is the same as the Paj that will need to be considered, but I dont recall anyone determining if it is or not. I do pretty much expect that this seems to be the way that vehicles are going as Mitsubishi have it happening already.

Figure this one out: With my previous redarc and 85amp Deka agm battery vs my now ctek and Optima yellow top 55amp battery, the ctek optima combo gives me longer running times.

[odie602r]

I used to have an isolator
Then I went to the ctek
Batteries hold charge longer fridge runs better

Due to the higher battery voltage from being fully charged

With and isolator when it comes on the start battery charges
the second battery with hi inrush currents before the alternator
Charges both batteries up together.
Which is no good with and agm as it needs a different charge rate.
agm batteries do not like high inrush currents and low charging voltages

In my setup I have my ctek charging 2 100amp hour batteries.
if U live local to green bank I'll show U why U need a ctek

For example when testing I had a fully charged start battery

And half flat second batteries voltage to my ctek was 13.8v (I had lights on etc)
Current was 20amps, voltage out of the ctek was 14.4v at 13amps
A agm battery needs to be charged at 14.4v to charge to 100%

My start battery was charging with 3amp

Here's a quote from http://www.fridge-and-solar.net/agm.htm that is a different perspective:

"because of their very low internal resistance these batteries will fully charge at a lower voltage, and accept a much larger charge current, so when charging from a standard car/truck alternator these batteries will all but fully charge, and fast too, in about 2.5 to 3 hours!"

I'm only posting this as sharing information I've discovered - not saying that this is 100% correct or the best/only solution. Hvac guy's situation may be different as he is charging two 100AH batteries - you'll only be charging one.

Your original post mentioned only wanting to spend the minimum - hence an isolator will do the job. Sure, the CTek will do the same job then some, it's just more expensive and not necessarily required.

By way of a personal example - I currently have a SLA 120AH battery removably mounted in the tub, with a Red Arc isolator, and connected using inadequate 6mm twin core cable. On a recent camping trip, due to a cable not being plugged in correctly, I inadvertently ran this battery completely flat (whoops). On the 2.5 hour trip home, this completely flat battery all but fully charged (I know this because when i got home I placed it on my 10A 240v smart charger, and it only remained on 'charge' for less than 30 mins before switching to 'float' mode, meaning it only topped up approx 5A more than the charge it got on the trip home).

I can only see this improving when I upgrade in the next few weeks to an AGM behind the rear seat as you are, but using 6B&S cable instead. For me, I already had the isolator from a previous vehicle. BTW, I used to have a camper trailer with 2 x 120AH AGM batteries in it, and the isolator and alternator used to almost completely top them up on a 2-3 hour trip too (from no less than 50% discharge).

Decisions, decisions ...

[Cowboy Dave]

I've had an isolator in mine but found I get longer life out of the AGM second battery with the ctek.

I have my old isolator at home somewhere if you want it. You can have it for postage or swing by and collect it if you're near Sydney. It's not doing anything in my box of spares.

I have the ctek 250s dual now as I bought a solar panel. In an accidental purchase from ebay I initially bought the 250s that is not dual - ie it doesn't have the extra ability to take a solar panel but will still do what you're trying to do. So maybe you could save some money buying that lower specced model - I haven't compared the prices lately. Alternatively perhaps we could come to an arrangement for my old one which is presently doing nothing at all, sitting somewhere in my garage in its box.

[lufc]

thanks for all the info (i love this site)
i think i will go with the ctek it sounds like the better option , i dont mind spending the $300 as long as it is what i need
cheers guys

[lufc]

I've had an isolator in mine but found I get longer life out of the AGM second battery with the ctek.

I have my old isolator at home somewhere if you want it. You can have it for postage or swing by and collect it if you're near Sydney. It's not doing anything in my box of spares.

I have the ctek 250s dual now as I bought a solar panel. In an accidental purchase from ebay I initially bought the 250s that is not dual - ie it doesn't have the extra ability to take a solar panel but will still do what you're trying to do. So maybe you could save some money buying that lower specced model - I haven't compared the prices lately. Alternatively perhaps we could come to an arrangement for my old one which is presently doing nothing at all, sitting somewhere in my garage in its box.

thanks for the offer dave

[Cowboy Dave]

One of these days I'll have to sit down and put up for sale listings for all the crap I have accumulated - I could use the room in my garage.

[dan_4818]

I'm about to do my dual battery soon. Goin to just use a voltage sensitive relay from abr sidewinder. That will do the trick for me

[Kingbrown]

CTEK 260S Dual is selling on eBay for $259 (incl freight) at the moment.

Past murmurings of a Group Buy were at a higher that that, so sounds like a good deal to me.

[salt36]

Well I have both a redarc and a ctek 250s dual.

I used to use the redarc to charge second battery in my tub, it worked fine.
I now use the ctek and it works fine, I now have a solar panel which (mentioned above) charges both my start and second battery.

It is worth noting that I used to drive long distances with the redarc and ctek, 2hrs twice weekly plus 20-30mins twice each day, so I guess either option had plenty of time to charge.

I now use my redarc to supply power to my inverter and know that it will shut off before my start battery goes flat

[veight]

anyone got pictures of there ctek mounted ?

[veight]

I have a ABR Dual Battery isolator system installed. ( Installed in a rush last easter)
Never had a flat batt yet, but will change over to a ctek when i get a solar panel so far so good.
When i travel its long distance normally so this could be the reason i haven't got a flat batt yet.

2 weeks ago I was mucking around with a volt meter with the car running & no load on the car measured 14.18volts at the starter batt & 14.11 volts at the battery in the tray.

[Tony81]

anyone got pictures of there ctek mounted ?

viewtopic.php?f=51&t=10992

viewtopic.php?f=51&t=7379&hilit=Snoozy&start=75

Here is two examples of the ctek mounted in my vehicle and snoozy's as well...

Edited for the correct link

Snoozy's install is about half way down the page.

[veight]

Thanks for the info.
Might be up grading quicker then originally planned, both links are the same. I will go search for the other.