hi all ,ive got this fitted to the pajero, and after checking the alternator volts , the alternator puts out 14.38v but when i check the battery in the back of the pajero i get a reading of only 12.7. finding the strange i decided to ring redarc and they told me that this system will only go as far as 12.7 volts. they also told me that seeing i have an agm 103 amp battery that it is no good for what i need and told me to buy this charger,bcdc1220. this will put in 20 amp and allow 14 volts to go to the rear battery
my point is if the system that ive got will only go to 12.7 why sell it, as i need as much power going to the rear battery as posible. if the alternator puts out 14v at the starter battery you would want it to the rear also
for thoughs who are thinking of buying one, i would not recomend it, as told to me by redarc them selves
what do you all think
regards possum, yvonne

Hi there, After looking at there site it apears to be just a solenoid that is turned on or off at preset voltages. with the engine running & solenoid activated check the voltage on either side of the solenoid terminals, they should be close to the altenator voltage. then check the voltage at the battery in the back, if the voltage is to low at that batery then i would suspect that the wiring is too small,. thats my thaughts. Daryl (The altenator should be capable of puting in far more than there  DC/DC 20A charger)

-- Edited by DeBe on Wednesday 15th of December 2010 10:52:46 PM

hi daryl, yeah i checked that first ,thats why i rang them. they recon that they will not allow 14 volts to enter the battery. so looks like im back to square one, again regards peter

If I'm reading this correctly that seems really strange as no battery will fully charge at 12.7 volts. I can't help but feel there's possibly some misunderstanding or mis-communication with Redarc.  As I'm not privvy to your discussions with them obviously this speculation.

Have you measured the output of the solenoid at the solenoid's output terminal in order to establish the voltage drop in the line to the battery. You'll need to measure the aux battery voltage at the battery terminals at the same time. This may give you a better picture of what's going on.

I also have a Pajero Diesel (NP) with the aux battery mounted in the engine compartment near the main battery.  (Unfortunately this limits the aux battery size to 50 ah but that's not relevant this issue.)  I found that it is necessary to use 8mm cable and to keep the length of wiring as short as possible between the main, the isolator, and the aux in order to optimise the charging of the aux.

The isolator (solenoid) is a Rotronics solid state unit. The (forward) voltage drop internal to the this isolator is insignificant.

With this configuration the charging current is around 27 amps when the aux is about 50% discharged.

In a previous vehicle I had the aux battery mounted in the rear and found it almost impossible to get a full charge into the aux battery without "topping up" with a mains charger when able to do so.

This leads me to believe that a DC-DC charger is the optimum solution to rear mounted aux batteries.

Check out http://www.bainbridgetechnologies.com/vmchk/chargers/ctek-d250s-dc-dc-20a-battery-charger

and http://www.batteriesdirect.com.au/shop/product/10524/d250s.html

(Disclaimer: (CYA) I have not used this charger or dealt with Batteries Direct)

Further to my post above I should have re-read your post a little more thoroughly.... There is a voltage drop of 1.7 volts (14.4 - 12.7) in the cable run from the Redarc to the rear battery. The Redarc would appear to be operating properly and the voltage drop would be due to the cable. I would consider a minimum size cable to be at least 8 gauge or 8 mm2.... note this is 8 square millimetres cross sectional area. Automotive cable sizes are very confusing and often much lighter than the nominal size would imply. Note that the wiring is the limitation on the charging current and not the output capacity of the alternator. It's also my view that it's unlikely you would ever get an average charging rate of 20 amps (averaged over the charging cycle) to a rear mounted aux battery without some means of recovering this voltage loss such as DC-DC charger. If installing such a charger I would think that your existing wiring would be satisfactory. I do qualify the above statement by saying that a battery with a lower charging voltage such as a gel battery may have a better charging rate. I haven't tried this option so there may be other techies on the forum who can add to this.

hi jim thanks for all the input. i took it to the 12v shop today and it looks like they have used auto wire instead of the right stuff, installed is4mm wire. the 12v shop said i have to replace the wiring with 8mm and that should fix it i will let you all no when its done. the 8mm wire is $8.00 per metre and i have to get 7m of itagain thats regards peter

in the mail today 10m 8B&S twin sheathed cable $6 metre and Ctek D250S dual for $339 and red Anderson plugs $5. Reason red Anderson plugs is they cannot be plugged into grey ones and dont want the fridge plugged into wrong Anderson plug. The son will install at the weekend. Went for Ctek D250S dual as you can connect solar panel and use as solar reggie. Going to pick up new 120 battery tomorrow. Reading Ctek manual make sure is done exactly as manual. Son is inclinded to rush. Thankfully got good advice and helps having scientific background.
Jacko is excited to go vanning again.

I'm not the only "techie" type on the is forum to have made this comment,  but many auto electricians are not very savvy when it comes to the all the issues around installing auxiliary batteries in RVs.  If the 12v shop you are dealing with installed the 4mm cable in the first place I would be very wary of dealing with them in future as they most likely fall into this catagory.

Anyone considering this type of work or RV (I use term "RV" in its broadest sense) electrical work in general needs to "sus" out the sparky's experience in this area.

Make sure that the so-called "8mm" is genuine 8B&S (or AWG) gauge cable. It should have a cross sectional area of approx 8mm2 that is 8 square millimetres (not the same thing as 8mm)  Ask to sight the label on the cable drum if necessary to establish this.   4mm cable would be too light even if installing the DC-DC charger.

I recently purchased a small spool of "4mm" cable and the label quoted a cross-sectional area of 1.85 mm2.  So much for auto cable sizes!

By the way the correlation between 8mm2 and 8 gauge is purely coincidental. At no other cable size does this correlation exist.  Obviously the larger the cross-sectional area, the larger the cable (self evident!), but a higher number gauge signifies lighter not heavier cable.

I have not used a Ctek D250s but I do have other Ctek chargers and find them to be a good quality product.  Others on this forum also speak well of Redarc products and I have reason to doubt them.

Jim

-- Edited by jimricho on Friday 17th of December 2010 07:10:28 AM

Jacko wrote:

---

in the mail today 10m 8B&S twin sheathed cable $6 metre and Ctek D250S dual for $339 and red Anderson plugs $5. Reason red Anderson plugs is they cannot be plugged into grey ones and dont want the fridge plugged into wrong Anderson plug. The son will install at the weekend. Went for Ctek D250S dual as you can connect solar panel and use as solar reggie. Going to pick up new 120 battery tomorrow. Reading Ctek manual make sure is done exactly as manual. Son is inclinded to rush. Thankfully got good advice and helps having scientific background.
Jacko is excited to go vanning again.

---

Do you have the web link to the supplier of that cable?

 

hi jim yeah, i no what your saying .the 12v shop was really a solar and battery place that no what they are talking about. i didnt get it fitted there. it was done at the auto sparkies, who say its std practise to use the wire they used i also would like the link to the cable regards peter

Hi peter, Good to see you're well on the way to getting the issue solved. You may well find you don't need the DC-DC charger, time will tell. I have a Ctek 7 amp charger "semi-permanently" installed in my car wired into the 12v outlet for the car fridge (Bushman). When I have "ground" power available I hook this up to the power and this serves the dual purpose of "topping up" the aux battery and powering the fridge. I have had this set-up for a number of years and find it works well. Jim

hi jim, how do you find the 7 amp charger. what size battery are you using, i can run my fridge for 4 days on the battery before i have to charge it but at that stage the fridge turns of. question is, do you think my alternator will keep the charge in my 103 agm battery while driving sorry about all the questions regards peter

Hi Peter, I'm only using a 50 amp hour battery as it's mounted in the engine compartment and there is insufficient space for anything larger. As a fellow Pajero owner you'd not doubt be familiar with this. The 7 amp job is quite adequate for my requirements however at a rough guess I would say it would take about 16 to 18 hours to recharge your battery from a "near flat" condition (a bit longer if you're using this to power the fridge as well). Keep in mind that you are most likely only using the charger to supplement the charging from the alternator so this may be satisfactory. The alternator is more than capable of powering the fridge and recharging the battery when on the move however I think it is unlikely you would get a full 100% recharge from the alternator alone due to the voltage drop in the cable (there will still be some voltage drop in the 8 gauge cable). This is the value of "topping up" the charge from time to time. The DC-DC charger overcomes this limitation but as it involves significant expenditure I'd be inclined to leave this option until you see a pressing need for it. You will finance quite a few Happy Hours with the saving. By the way what sort of battery are you using is it a gel or agm. Jim PS: feel free to ask questions, that's what this forum's all about.

By the way, one "gizmo" I do recommend is a "low voltage cut-out" to protect the battery from being totally discharged and consequently reducing the life of the battery.

more details at http://www.bainbridgetechnologies.com/battery-protectors/baintech-low-voltage-cut-out-40amp

hi jim thanks for all that. i was looking on the net at this charger. what do you thing jarcar mb3612 6 amp or 12 amp charges to 14.4v floats at 13.8 $109.00. regards peter

Hi Peter,

Firstly, my only knowledge of this charger is from having looked it up on the Jaycar website just now. (Yes, I admit to being in "CYA" mode here!)

If you intend using it from time to time just to "top-up" I feel it should be ok. Assuming that your Pajero is your "day to day" vehicle (mine is) you probably would only bother to "top up" the night before you're going to be camping "off power" for a few days, as the day to day running should keep the battery sufficiently charged for normal use. The charge status indicators are probably (although not sure) pre-set for a normal "wet" battery and may (perhaps) be a little misleading with other types of batteries, especially if powering the fridge at the same time, I don't see this as a major issue.

Being "hooked up" to the mains overnight in order to power the fridge as well, while camping on a powered site, should be quite ok with this charger.

If however you're looking for something that you can "set and forget" that you can use in a situation such as a caravan or RV that you can leave hooked up to the charger indefinitely and/or gives you the flexibility to fully charge a range of different types of batteries under different conditions I would be inclined to go for something with a few more "smarts".

Whilst I feel I can confidently recommend the Ctek product there are now many similar units on the market that are probably just as good and maybe a little less expensive.

In summary: I think ok for this type of application but would not recommend for use in a caravan or RV.

Jim

-- Edited by jimricho on Sunday 19th of December 2010 08:18:34 AM

hi jim thanks for the input on that, much app. i am still looking at the ctec one but im a little confused on it as i will explain the solar shop has one there which is fully auto which puts out 50amps into the battery i have a sonic agm battery but when i rang them they were saying that im not supose to put in any more than 10% charge of the battery which means if the battery is 100 amps im supose to use a charger at 10 amps only so how do other people go with putting higher amps into a battery like 30,40,50 amps i told the solar shop what battery i have and they are trying to sell me the 50amp one saying that the battery will be fine having that much charge being put into it i dont under stand, one says one thing and the other says something else regards peter

Hi Peter I use one of those Jaycar chargers, But it is on a flooded Lead acid battery, It definitly charges to 14.4V then drops back to 13.8V  if the fridge starts up the charger puts in more amps to compesate then drops back when the fridge switches off. The LED charge indicators are typical & dont tell mutch at all.

hi daryl, hows things going. here its been raining for days so far we have had 7 inches of rain and its now being a pain in the you no what im trying to get things done on the van and to put a box on the van but cant weld in the rain do you think that charger will be ok, plus the price is right regards peter

one more thing daryl, i have to change the wire for my daul battery system because they used the wrong wire, too thin. do you no where i can buy 9mrt of 8b&s cable from because up here they want $8.00 pm regards peter

Try Jacar - they will mail order by the metre. For more wire see this link.

hi peterd, can you tell me what size wire is 8b&s, is that the same as 8 gage regards peter

Hi Guys, If I may jump back in here.....AWG and B&S are one one and the same thing. 8 AWG (B&S) has a cross sectional area of 8.4 mm2. B&S is (I think) just an old designation (it's listed in my 40 year old "Reference Data for Radio Engineers" as B&S) A 50 amp charger would be complete overkill for a 100ah battery. The "kill" part of the word overkill may be significant in a literal sense too! I can't see that a 12 amp charging rate would be any problem unless it is an unusual battery, you would need to have someone drill down through the battery data sheet to get any better info but my view would be if 10 amp ok then 12 amp ok too. I find a 10 amp limit on the charging rate for an AGM battery somewhat puzzling but I'm not familiar with this particular battery. Just to bring Daryl and PeterD up to date, keep in mind (which you probably are) that we're talking about a charger for occasional use to supplement the normal charging from the car's alternator. Also to (possibly) "double up" as a power supply (with the battery in circuit) for the fridge when on "ground" power. This is a configuration that I have been using successfully for several years with my "Bushman" and the 7amp Ctek. Just plug in when arrived at a powered site, no other cords or switches to change over, remember to unplug before driving off..... (ummmm...Is my my face red! LOL! mmmm ..must do that memory course sometime!)

PeterD wrote:

---

Try Jacar - they will mail order by the metre. For more wire see this link.

---

Peter have you actually checked out that cable.  I used some a few years back on an old camper trailer and I felt that the insulation was a bit soft and not very robust for automotive use.  I'd be interested in your thoughts on this.

Jim

 

hi jim, i had heavy cable in my other pajero, it was the size of a smoke, dont no what size it was. i looked at the link you put up, thats why i was asking. when i saw the solar shop and they said my cable was too thin they told me to use 8 b&s, but i dont no what that it. i need to run 8mtr of it from front to rear . at the moment i have too much volt drop should i use differant wire maybe, what would you suggest regards peter

As mentioned earlier in the thread, yes, you will need 8 gauge cable  (don't worry about "B&S" or "AWG" these are one and the same thing and are just descriptors of the standards used to determine the gauge)   If you just specify 8 gauge this will cover it.

The cable in your previous Pajero looks like it probably was something in the order of this size.

Also mentioned earlier, the 4 mm cable installed is inadequate and is the cause of your charging problems.

In addition to the Jaycar link above you may be able to source the cable from a local marine supplier as Bias Boating list "8 B&S" cable in their catalogue. They stock this for use with electric outboard motors so your local marine wallah may keep it for the same reason.  If in doubt ask to see the cable drum they cut it from and look for reference to "8 gauge" or "8AWG" or "8B&S" or "8mm2"  (note the little "2" after the mm, this means millimeters squared)

Edit: (addendum) This is relevant to my previous post on the 10 amp charger....

I suspect that you may have misinterpreted what you were told about charging at 10% of the amp-hour capacity ie 10 amps for a 100 amp-hour battery and that this is only a suggested size.

I have seen this suggested as a practical guide to the minimum size charger for the battery, not a technical maximum or minimum limitation.  It does make sense as a guide.

I see no problem with the 12 amp charger.



-- Edited by jimricho on Monday 20th of December 2010 10:14:07 AM

Hi peter just checked to see what the Jaycar charger does on a sealed battery in real life & it starts charging till 14.4v then drops back to 13.8V & this test was done set on 12Amp setting & on a 7Ah sealed battery so i cant see it hurting a larger battery. also hooked up the Waeco & the charger went upto 6A, then when the fridge turned off it droped back & sat on 13.8V.  Daryl (also the fan in it is load & heat sensitive, when float charging the fan switches off)

-- Edited by DeBe on Monday 20th of December 2010 10:26:06 AM

ok, thanks daryl,so what your saying is, that charger would be fine. did you do the test with the one you have. also with my battery it would be best to set it on 12amps rather the 6amps then regards peter

Yes peter went out & did a practical test early thismorning. I was using it on the 12A setting when i charge larger batterys.  Daryl

-- Edited by DeBe on Monday 20th of December 2010 03:28:03 PM

ok daryl, thanks for that and the info also taking the time to do the test as well, again thank you regards peter