c-tek 250s dual 12v to 12v charger

Hi everybody
I am considering installing one of these as my dual battery system instead of the traditional battery to battery with an isolator.

Wondering if anybody has tried these units or heard any comments good or bad.

Regards
Adrian

i was going to use the same but i decided on a simple redarc setup
dc/dc is probably the best way to go but the outlay is a lot more
how often are you planning on using fridge ect ?

I'm of the belief that these type of setups are more suitable where there is a great distance between batteries (eg: batteries in C/T or Vans). This is where the advantage is ... when u have batteries under the bonnet I don't see the benefit or the cost justification.... just use one of the common battery isolators and use similar batteries

Was thinking about the DC-DC charger way but now going down the Inverter> smart charger>aux battery route. Kind of handy having 230 VAC there to if you need it.

sparra04 said:

i was going to use the same but i decided on a simple redarc setup
dc/dc is probably the best way to go but the outlay is a lot more
how often are you planning on using fridge ect ?

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Probably use the fridge about 4-5 times a year for 2 weeks at atime

Robmacca I also have a van which has a 105amp deep cycle which needs charging. I have been told that the alternator will not fully charge aux batteries to full, is this correct.

Tappet That system sounds ok, having access to 240 would be advantage, but will that system charge the batteries quickly.

I also have a 240watt solar panel which I use to top up the batteries.

Thanks for your help so far

mate with a 240 watt solar panel you should be ok
old tony is the guru on 12 volt charging ect
he will be able to give you great advise
send him a pm
or wait for him to reply here as he is in tazzie atm

skipjack said:

Robmacca I also have a van which has a 105amp deep cycle which needs charging. I have been told that the alternator will not fully charge aux batteries to full, is this correct.

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That's correct... A Car Alternator will never 100% charge up your batteries under the bonnet... I believe the best is around 80>90% I think....

Apparently with the DC-DC Charger there is a +/- imput voltage tolerance and u still get a constant output charging voltage. This would work ideally where there is a fair distance between the Car's Alternator and the battery in the C/T or Van.... Due to the distance involved, there will always be a voltage drop due to the length of cable involved. This is where the DC-DC charger would be good to install in your Van or CT at or near the battery that req's charging. As long as u run heavy enough cable that can handle the expected current flow u should be in a position where u will hopefully have a fully charged Aux battery

The volts may drop to 12.5v or below (Cable size depending) by the time it gets to the Van and obviously this voltage level is too low to charge the battery, but with these units it won't or shouldn't matter as u will still get the req'd charging output voltage. It should give u a +/- voltage imput voltage on the unit..... I would like one of these on my Van but didn't find out until it was too late & I had spent my $$ on my current system. If my current system fails me, then I'll save/spend the money and install one in the Van....

only thing i don't like is its kind of a bulky unit.

Welcome to the forum, Skipjack.

The DC-DC charger is fine, as long as you supply it with good enough cabling and you put fuses where they're needed (close to the battery).

I personally use an inverter to provide 240V and then use a normal smart charger to provide power to the battery. This has a few advantages over a DC-DC or isolator system:

1) I have 240V available. That means I can charge other shit like my cordless drill.

2) I have 240V available. My Engel fridge automatically switches over to 240V when it is available, which removes the load from the battery and lets the charger manage the battery much more accurately (and that equals better battery management = longer life).

3) I can replace bits that break almost anywhere. Jaycar (or agents) and even Ray's Outdoors sell Powertech inverters. Good kit, electrically isolated, worth the coin. C-Tek make the best chargers but also draw serious coin for it. I have a Projecta 1.6A charger that I picked up in Bunnings of all places - I'm trying it out to see how it goes. I think it's underpowered - even a modest 50Ah wet-cell battery can be charged at 5A. Gels need a little more care (strictly speaking they should be binned, they're crap) but anything that can deliver 5A or better is good.

On charging rates - unless you are using an AGM (Absorbed Glass Matt, designed for military use and bloody near indestructible) you really need to keep the charging rate at a tenth of the battery's capacity or less, so a 100Ah battery can be charged at 10A max. If you charge it too fast you boil the electrolyte away and that's not only explosive, it can shorten the battery life. It also surface-charges the plates, which will make the battery look charged, but it will actually have only a partial charge.

And yes, having lots of fun in Tasmania - just did the Wilderness Railway. Awesome stuff!

Ok firstly Thanks for all the replies.
Old.Tony Am I right in assuming that you only run the inverter system while driving, and that you plug the engel and the smart charger into the inverter, so that when the engine is off the engel reverts to running from the aux battery?

If going down this road, what size inverter and c-tek charger do you suggest?

You are correct that the inverter only runs while driving - the power to the rear is controlled by an ignition-on switched relay (via a 30A thermal breaker).

Any charger that you choose should be geared for your battery. There's no point buying a 25A charger if you have a 50Ah battery, your battery will last a couple of weeks - a month or two if you're lucky. Just pick a charger that charges no faster than C/10 - C being the capacity of the battery in Ah (sometimes shown as "RC" on the battery). The only exception is if you get an AGM battery. AGMs can be charged at phenomenally high rates - even C/3 is possible (with some, like the spiral wound models) without killing the battery, although to be safe you might want to limit it to C/5 - so if you have a 100Ah battery, don't go past a 20A charger.

For a 20A charger, you need to supply MORE than 20A because the charger uses some power as well. Let's say you get a 150Ah AGM and decide that 25A is enough charge rate for you. Allow 30A through the inverter, which means 30*13 (say) = 390W. A 400W inverter will JUST do that - I'd suggest looking at a 600W inverter so that it's not running at full-pelt its entire life.

Then I'd put a 40A thermal breaker, with a 60A relay, and 8 sq mm cabling - 10sqmm would be even better for that much current.

Everything, really, is tied down to the battery you choose and the method of charging.

While everyone is at it I am currently researching the ol dual batt setup and going down the line as arty's setup in the tub. Looking at the ctek 250 dc to dc charger. After doing the search thing I cant seem to find (not saying its not there anywhere) what size cable to run from the main batt to the charger? I want to do this right the first time

cheers
Matt

Hi there, first timer here. Been following forum for awhile now, very handy site.

Navara's 2011 onwards have an ECU controlled alternater, this requires the DC to DC charge to be able to charge a dual battery properly and to its fullest. From what i have read and understood.

Therefor you can get away with smaller cable say like 8AWG from main battery to Charger. The charger then steps the voltage up to allow for full charge, this is where the cable needs to be correct and the right voltage drop.

I am currently putting together a dual battery system, but going to use the Projecta DC20,

Cheers mate, not being to electrically minded I ebayed 8awg and it all seemed to be stereo/amp cable is thaty right? I was thinking the 8B&S cable whatever that means.

http://www.ctekbatterychargers.com.au/uploads/3/6/2/9/3629451/d250s_dual_manual.pdf

Have at look at this mate, page 12 is minimumn cable sizes, this is in mm squared tho, but easy to work out.

AWG is american wire and gauge and B&S is Brown and sharp which the same as AWG.

http://www.engineeringtoolbox.com/wire-gauges-d_419.html

Use this to check sizes, so a 4mm squared cable would be 10AWG there abouts.
I went 8awg so i dont have to worry about voltage drop, bigger size always better.

The cable you need is battery cable, its a multi stranded cable, like 70plus strands, dont know the exact number but its very high. Just type battery cable into ebay and it comes up.

miner-matt said:

Cheers mate, not being to electrically minded I ebayed 8awg and it all seemed to be stereo/amp cable is thaty right? I was thinking the 8B&S cable whatever that means.

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If your only going to be running a Ctek D250S only, you could get by with 6mm cable.
Check out autoelecua on eBay for cable, fittings and D250S. They provide an extra 2 years warrenty on D250S.
http://www.ebay.com.au/itm/6MM-TWIN...=AU_Car_Parts_Accessories&hash=item4605af0d47

If you planning on putting a caravan or trailer on later I would put 6B&S cable in now so you could loop off via an Anderson plug to the van later. Would need another D250S in van or relocate from Nav.

Yeah that autoelecua is a pretty good site, i brought heaps of them, def worth a look.

While I once thought 6mm cable used to be good enough, I no longer believe so. I replaced the 6mm cable running to my fridge with 4ga (about 21mm2) and over 6m I'm getting about 0.3V of drop - and ANY drop = lost power.

I'd recommend going as heavy as you can - and fusing it just as it reaches a battery.

Old.Tony said:

While I once thought 6mm cable used to be good enough, I no longer believe so. I replaced the 6mm cable running to my fridge with 4ga (about 21mm2) and over 6m I'm getting about 0.3V of drop - and ANY drop = lost power.

I'd recommend going as heavy as you can - and fusing it just as it reaches a battery.

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Ok... Running from the main battery to a battery in the tray approx 4m, so thinking the 8 or the 6awg. Now wiring... would this be ok.. Main Batt--Fuse(50amp?)<-------------POS-------------->Fuse>--<DC to DC>-----AUX Batt. Now do i need to run a NEG cable from the main batt or can I pick up closer to the battery say the chassis before the run up to the headboard. Also should there be another fuse between the charger and battery?

cheers
Matt

There's actually no need for a fuse near the DC/DC charger, which will not send power back up the line and should have a fuse on it for its output. If they're mounted in proximity to the battery you might consider not fusing near the battery but if something goes wrong, it's the battery in the back that will have the juice to cause problems not the DC/DC charger so you'd move the fuse (40A ought to be enough) to the line between the battery and the DC/DC charger.

Do you run a separate negative wire? Good question, some say no, some say yes. If you don't, then every joint between the DC/DC charger and the battery up front becomes a possible failure point. It becomes a matter of risk - do you take the risk, or go to the expense of removing the risk?