School me on DC/DC chargers and systems

[Cuppa]

without smart pass up to 300ah.
with smart pass 80 amps and 28-800ah.

from memory ctek is no good with smart alternators.
I'm fairly sure redark can handle smart alt as the low volt switch off compensate being something like 10v.

I know for fact ford ranger and ctex don't work together, the smart alternator function can be turned off to fix it but at $400 lol.
rangers smart alt saves all of 400mls of fuel over 100klm what a waste of time, fitting manual hubs to disengage front diff would easily save more than that.

Redarc have two different BCDC1240’s , the ‘standard’ BCDC1240 & the BCDC1240LV (Low voltage) for smart alternators.

[MudRunnerTD]

Correction I have 2 X D31a Optima yellow tops under the bonnet. Not sure that changes anything? Just a bit bigger.

[Cuppa]

Correction I have 2 X D31a Optima yellow tops under the bonnet. Not sure that changes anything? Just a bit bigger.

150Ah. If going with dc to dc to charge them then a 20 or 25 amp unit would still be ok, but could fit a 40 amp unit if you are likely to be heavily discharging them.

Mind you, I still haven’t heard why you think you need one at all for them. Maybe before deciding do the following: 1.Charge the Optimas at home with a mains smart charger until they are full (charger goes into float mode),
2. Go camping & just use things as you normally do. 3. Drive home & park car overnight having ensured that nothing is running off the optimas. 4. Next morning check the Optima voltages with a multimeter/volt meter across the terminals. If you have a voltage of 12.6v+ (if new I’d say 12.7v+, but at 5 years old it is likely that some capacity will have been lost) you wont need a dc to dc charger for them. 12.5v would be a line ball call, but could just be reduced battery capacity.

FWIW I previously had a set with two alternator charged D31 Yellowtop Optima’s as crank batteries (24v) paralleled to a pair of 90Ah aux batteries (Fullriver) via a two way VSR, & topped up with 2x60w solar panels & had no concerns with this despite slightly different recommended bulk charging voltages. From memory Optima say a slightly higher bulk charging voltage than ‘conventional’ AGM batteries can be used, but they give a range, suggesting that charging them at a conventional 14.4v/14.5v is fine. Just that they can be charged a bit quicker at up to 15v provided they are under a specified temperature. I suspect that this is a bit of marketing hype to try to differentiate their ‘spiral wound’ construction, & in reality their requirements are little different to any other AGM battery which could also be treated similarly if battery temperature was monitored.

Besides...... fitting a DC toDC charger won’t raise the bulk charging voltage unless you set it on the Calcium setting, which I wouldn’t advise as it would likely overcharge them (15.1v I think). What it does do is use it’s electronic ‘smarts’ to squeeze in a bit more once the battery is above 80% full, which in most circumstances the alternaor alone wont do.

The ‘raising the voltage’ function is different for circumstances like the camper battery. It can raise the a voltage which has been reduced by the longer wire run to the needed 14.4v/14.5v. Without this the voltage drop in the cabling can prevent the camper battery from being properly charged. It also does the over 80% ‘squeezing in’ function.

[Rock Trol]

I have to agree with Cuppa in asking the question, do you really need one. I had a Redarc bc:dc 1220 under the bonnet to charge a Deka AGM battery. I was hoping to extend the life of the battery as they are expensive ($400 at the time). My battery only lasted 3.5 years and had lost some capacity in the months before it dropped a cell (battery had expanded). I don't know how long it would have lasted without the charger but it was not cost effective for me to add the charger. I feel that I just spent money for no reason on this occasion.

If the car had a smart alternator then they would be useful or in a camper for voltage drop. Patrol alternators provide decent output and if you charge it regularly with a 240 volt charger when at home then it should keep the battery in good condition. Then again, you might have better luck than I did. If you already have 5 years out of your AGM's under the hood then you must be doing something right.

[FNQGU]

Agree with Cuppa and Rock Trol - your usage will determine the $$ you actually need to spend here. Marketing is a wonderful thing and convinces many of us to buy shit we really don't need.

I am happily using the old Redarc 15A BMS for my main Aux battery in my trucks canopy, but only using a solar reg to charge my 2nd Aux battery (under bonnet) when needed, and if not going for a drive every few days. This has saved me a stack of coin, and works perfectly for what I use it for. ie. I run a 2nd fridge off it that sits on the back seat on longer trips, plus the UHF and a small 350W inverter for camera and laptop charging.

Of note, if you are looking at dc-dc chargers - have a good hard look at another Aussie brand called Intervolt, who make a 25A jobbie that on paper appears to out-spec just about everything else out there at present and at comparable prices.

[MudRunnerTD]

So I've listened to you guys and abandoned the idea of a DC/DC in the car. Don't fix what ain't broke. Like that logic.

After a fair bit of consideration I found the CTEK unit on sale on eBay at a good price so will fit it into the camper supplying 2 new 105AH AGM batteries (found some for $150 each on eBay! Score)




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[Robo]

Agree with Cuppa and Rock Trol - your usage will determine the $$ you actually need to spend here. Marketing is a wonderful thing and convinces many of us to buy shit we really don't need.

I am happily using the old Redarc 15A BMS for my main Aux battery in my trucks canopy, but only using a solar reg to charge my 2nd Aux battery (under bonnet) when needed, and if not going for a drive every few days. This has saved me a stack of coin, and works perfectly for what I use it for. ie. I run a 2nd fridge off it that sits on the back seat on longer trips, plus the UHF and a small 350W inverter for camera and laptop charging.

Of note, if you are looking at dc-dc chargers - have a good hard look at another Aussie brand called Intervolt, who make a 25A jobbie that on paper appears to out-spec just about everything else out there at present and at comparable prices.

http://www.intervolt.com/product/in-...horizontalTab3

Very nice specs indeedy.
Specifications
Input Voltage –
• Main: 9 – 17 VDC,
• Solar Input: 27 VOC max. (open circuit – no load)

Solar Power – 250 Watts nominal (300 Watts peak)
Continuous Rating – 25 Amps @ 50°C
Current Draw –
• Charging Device: Including LED indicator <10mA
• Remote Display: With backlight off: 10mA max,
• With backlight on: 30mA max

Boost Voltage –
• Standard Lead Acid: 14.4 VDC Nominal
• Absorbed Glass Mat: 14.6 VDC Nominal
• Gelified Electrolyte: 14.2 VDC Nominal
• Lead Calcium: 14.8 VDC Nominal

Float Voltage – 13.2 VDC Nominal
Electrical Protection –
• Thermal overload shutdown – auto reset
• Electrical overload shutdown – auto reset
• Under voltage disconnect – auto re-connect
• Over voltage disconnect – auto re-connect
• Reverse polarity protection of main terminals

Environmental Protection –
• Charging Device: IP67 (internal components only)
• Remote Display: IP40 (not dust or water resistant)
Operating Temperature – -20°C to +85°C
Operating Humidity – Up to 98%
Charging Device Materials –
• Heatsink: E-Coated ADC-3 die cast aluminium
• Blue Plastics: Temperature resistant PC/ABS alloy
• Black Plastics: 15% glass reinforced PBT
• Transparent Plastics: Temperature resistant PMMA

Remote Display Materials –
• Dark Grey Plastics: Temperature resistant PC/ABS alloy
• Transparent Plastics: Temperature resistant PMMA

Terminal Material – Tin plated brass
Terminal Fasteners – 304 stainless steel
Conformity – AS/NZS CISPR 11:2004 for EMC
Dimensions –
• Charging Device: 112 x 112 x 75mm (including terminal cover)
• Remote Display: 60 x 36 x 59mm (including mounting bracket)

Weight –
• Charging Device: 690 grams
• Remote Display: 55 grams

[MudRunnerTD]

Of note, if you are looking at dc-dc chargers - have a good hard look at another Aussie brand called Intervolt, who make a 25A jobbie that on paper appears to out-spec just about everything else out there at present and at comparable prices.

I did have a look at these too. I got the CTek for $265 delivered and couldn't go passed it to be honest.

But just having another look on eBay and this is a Bloody Good deal! If id seen this i may have gone this way as i need a couple of batteries anyway.

http://www.ebay.com.au/itm/FREE-BATT...4AAOSwcUBYG8re

[Cuppa]

http://www.intervolt.com/product/in-...horizontalTab3

Very nice specs indeedy.

Whilst I have no quibble about build quality (Intervolt are good) I am disappointed by these specs, or more precisely by one specification & the total absence of another. Intervolt have done the same as Redarc did with my BCDC1240.

Float voltage of 13.2v is lower than all the AGM battery manufacturers recommend & is set at this level because they have, like Rearc failed to incorporate battery temperature compensation (7 monitoring). For those who aren't familiar, battery temp compensation means that the regulator will adjust the charging voltage according to battery temperature, usually by around 0.3v for every 5 degrees above or below 20 deg.C. It is my view that temperature compensation is the feature which most helps to extend battery life.
When VRLA batteries get too hot they can suffer from a phenomena called thermal runaway where they just keep getting hotter & hotter resulting in a bulging & destroyed battery (& fire risk). Often dc to dc chargers are used with batteries housed in the hot under bonnet situation & it is my view that the low float voltage is used as a cheap way of protecting from thermal runaway, instead of monitoring battery temp & adjusting charging to suit. Most battery manufacturers specify a float voltage of 13.6v to 13.8v.

Just out of interest what is the float voltage of the Ctek Darren, & does it have Temperature compensation? If not it is on par with Redarc & Intervolt products. If it does then I would suggest it is first preference.

[MudRunnerTD]

Whilst I have no quibble about build quality (Intervolt are good) I am disappointed by these specs, or more precisely by one specification & the total absence of another. Intervolt have done the same as Redarc did with my BCDC1240.

Float voltage of 13.2v is lower than all the AGM battery manufacturers recommend & is set at this level because they have, like Rearc failed to incorporate battery temperature compensation (7 monitoring). For those who aren't familiar, battery temp compensation means that the regulator will adjust the charging voltage according to battery temperature, usually by around 0.3v for every 5 degrees above or below 20 deg.C. It is my view that temperature compensation is the feature which most helps to extend battery life.
When VRLA batteries get too hot they can suffer from a phenomena called thermal runaway where they just keep getting hotter & hotter resulting in a bulging & destroyed battery (& fire risk). Often dc to dc chargers are used with batteries housed in the hot under bonnet situation & it is my view that the low float voltage is used as a cheap way of protecting from thermal runaway, instead of monitoring battery temp & adjusting charging to suit. Most battery manufacturers specify a float voltage of 13.6v to 13.8v.

Just out of interest what is the float voltage of the Ctek Darren, & does it have Temperature compensation? If not it is on par with Redarc & Intervolt products. If it does then I would suggest it is first preference.

Just opened the box and had a read through the owners manual. its thick but is 8 languages.....

It has a Float Function but doesn't declare the voltage. It has a 1.8m long Temperature Sensor that i connect to the side of the battery and has Temp Compensation but doesn't declare at what temp.