DC-DC chargers Redarc or Ctek

[LiveFreeAndRoam Avid PP Poster! Find all posts View Profile Close LiveFreeAndRoam]

I am looking at the REDARC BCDC1240 for the new car, i currently have the BCDC1220 in the cabin on the current truck

Curiously, why are you going the BCDC1240 over the 1220?

LFaR.

[downunder Find all posts View Profile Close downunder]

I was thinking it would be able to recharge the battery faster as it charges 40Ah over 20Ah of the 1220, so when i am camping and only traveling a few hours a day it would be able to charge the battery up better and it also able to charge from solar cells so it can do both in one item.

[LeighW Avid PP Poster! Find all posts View Profile Close LeighW]

An AGM battery is a lead acid battery, it only differs in the way the electrolyte
is contained.

A flooded wet cell and an AGM battery will happily charge in parallel off
an Alternator as they virtually have the same charging requirement though
the flooded wet cell will charge slightly slower as it requires a slightly higher
charge voltage than the AGM.

I would recommend using a AGM battery that is designed for automotive use
such as the Optima types.

In the latest model vehicles the most likely battery to suffer will be the flooded cell
(cranking battery) due to the lower output voltage of the latest Alternators, therefore
if left standard it would be a good idea to charge the cranking battery occassionally with
a charger.

[LeighW Avid PP Poster! Find all posts View Profile Close LeighW]

I was thinking it would be able to recharge the battery faster as it charges 40Ah over 20Ah of the 1220, so when i am camping and only traveling a few hours a day it would be able to charge the battery up better and it also able to charge from solar cells so it can do both in one item.

Depends on the AH rating of the battery, if very large yes, if around the 50AH - 80AH range probably won't make much difference.

[downunder Find all posts View Profile Close downunder]

On my current Hilux i have a 100AH lifeline AGM battery. I was advised by the manufacture (Lifeline) that i should not parallel the two AGM + Flooded lead acid batteries up as the internal resistances are different and if i want it to work properly i should use a 3 stage charger, which i did.
My limited knowledge of electrics i used the analogy of having a low resistance and high resistance resister in parallel circuit then most power would go though the low resistance rather than equal. Please let me know if i have been advised incorrect. ?

[AJ120 Out of control poster! Find all posts View Profile Close AJ120]

I read most of these DC DC charging threads with great interest, for the life of me though have not been able to find a reason why I would spend the extra money on a DC DC charger!

As for differnet batteries needing different charges I can only speak from my own experience. My Cape York trip last year, 8 weeks, 1 fridge, 1 freezer, Wet call cranking battery, AGM auxillery, wet cell deep cycle battery in the Camper Trailer all run off the alternator with LieghW's booster no problems. The only exeption was the 4 days we spent in Cairns without driving much and we also restocked the Freezer for the next 4 weeks at this point so it was working overtime, I just hooked my old $20 4 amp battery charger up to the mains at the park and hey presto everything was good as gold.

40,000k with the booster in now and zero problems!

Cheers Andrew

[LeighW Avid PP Poster! Find all posts View Profile Close LeighW]

On my current Hilux i have a 100AH lifeline AGM battery. I was advised by the manufacture (Lifeline) that i should not parallel the two AGM + Flooded lead acid batteries up as the internal resistances are different and if i want it to work properly i should use a 3 stage charger, which i did.
My limited knowledge of electrics i used the analogy of having a low resistance and high resistance resister in parallel circuit then most power would go though the low resistance rather than equal. Please let me know if i have been advised incorrect. ?

Technically what they told you is correct, the AGM will have a lower internal resistance than the
flooded wet cell. To get this in perspective though we a talking milli ohms and in pratical applications this will have little affect.

When you apply a charging voltage to a battery the inrush current into the battery will vary according
to the batteries charge state, temperature, AH capacity etc. These factors and others determines the batteries internal resistance.

When a flooded wet cell and AGM of the same AH rating are charged in parallel both will accept a current as determined above, if all factors are equal the AGM will take a "little" more initially. If one or the other is more discharged then that battery will intially accept a greater current flow.

The inititial in rush current, assuming both batteries are highly discharged will in reality be limited by what ampage the alternator is able to supply, ie the large initial current draw will cause the alternators output voltage to drop and limit the current. After a period of time the current drawn by each battery will decrease and the alternator voltage will rise to its normal float voltage ie 14.4V volts and act as a constant voltage source. At this time the alternator is actually capable of supplying more current than required by either battery and each battery will take what it wants without affecting the other.

The same applies to 3, 4 five batteries etc. The only time dissimilar batteries are going to cause a
problem is if the alternator can't supply enough current to reach float level and if this is the case
you need a bigger alternator.

It is only in the first few minutes of charging that one battery will hog the charge and in pratice this will have little if any affect.

Hope this makes it a bit clearer.

[downunder Find all posts View Profile Close downunder]

Thanks LeighW for your input, the inrush of technical information flooding my brain, i think i need another beer. !!!
I cannot understand why the battery manufacturers would harp on isolating them when it is not really required in practice, i could understand Redarc or C-Tek as their is a vested interest to see more products.
if i still wanted to go down the charger way with the solar charger, could you still use the voltage booster diode ? and would it be beneficial for the main battery ? But i am now sitting on the fence which way to go whether to spend the money or no ?

[LeighW Avid PP Poster! Find all posts View Profile Close LeighW]

downunder I'll PM you

[LiveFreeAndRoam Avid PP Poster! Find all posts View Profile Close LiveFreeAndRoam]

Hi Downunder,

I was thinking it would be able to recharge the battery faster as it charges 40Ah over 20Ah of the 1220, so when i am camping and only traveling a few hours a day it would be able to charge the battery up better and it also able to charge from solar cells so it can do both in one item.

Yes, that is generally the case. I'd suggest checking with the battery manufacturers before you buy the 1240, to see what their maximum charging current is. When I was looking at this about 18 months back, I don't think there were many (any?) car batteries that were spec'd for a 40A charge. I'll be eager to know if you find batteries for this.

My understanding of the BCDC 1240 was that it was better suited to charging batteries in parallel, e.g. two or more batteries in a caravan. I'm sure Redarc will be able to clarify and I've found them to be very responsive if you shoot them an email.

Cheers,
LFaR.

[downunder Find all posts View Profile Close downunder]

Well the spec from their web site, i get the impression it can handle up to 250amps unless I am missing something.Please find charging specs below.

GPL-27T Charging Instructions and Voltages:
Bulk Charge Voltages: 14.20 - 14.60
Absorbtion Charge Voltages: 14.20 - 14.60volts
Float Charge Voltages: 13.10 - 13.40
The GPL-27T is designed for charging amperages up to 250 amps or 250% of the rated Amp Hour Capacity due to low battery internal resistance.

[LiveFreeAndRoam Avid PP Poster! Find all posts View Profile Close LiveFreeAndRoam]

I don't think you're missing anything. That looks like an awesome battery. The BCDC1240 looks to be a good match with the GPL-27T.

Cheers,
LFaR.

[LiveFreeAndRoam Avid PP Poster! Find all posts View Profile Close LiveFreeAndRoam]

Hi Andrew,

I read most of these DC DC charging threads with great interest, for the life of me though have not been able to find a reason why I would spend the extra money on a DC DC charger!

In a nutshell, "What a modern DC-DC charger does for you":

1. Regulates output charging voltage for a wide-range of input voltages
2. Sets charging voltage to recommended value for a battery type
3. Acts as an isolator (only charges your aux after main reaches full charge)
4. Substantially reduces the time to recharge your battery
5. Multi-stage charging cycle for best care (and life) of your battery
6. Some models provide for multiple voltage inputs (e.g. solar-cell, wind-turbine, or alternator)

Whether a consumer buys into the science and reasons for it, is a choice.

BTW, in your example of "not much driving", a DC-DC charger would have given you the best chance of keeping your fridge running. Naturally, your $20 battery charger is only useful when you have access to mains power. Often times, I don't have that 'misery' .

Cheers,
LFaR.

[LeighW Avid PP Poster! Find all posts View Profile Close LeighW]

Hi Andrew,

BTW, in your example of "not much driving", a DC-DC charger would have given you the best chance of keeping your fridge running. Naturally, your $20 battery charger is only useful when you have access to mains power. Often times, I don't have that 'misery' .

Cheers,
LFaR.

Definetly have to disagree with this statement, for instance if AJ120 was only doing 20 minutes driving a day
his setup would put 2 to 3 times the charge in his battery than a 20AH DC DC charger could.

[AJ120 Out of control poster! Find all posts View Profile Close AJ120]

Hi Andrew,

In a nutshell, "What a modern DC-DC charger does for you":

1. Regulates output charging voltage for a wide-range of input voltages
2. Sets charging voltage to recommended value for a battery type
3. Acts as an isolator (only charges your aux after main reaches full charge)
4. Substantially reduces the time to recharge your battery
5. Multi-stage charging cycle for best care (and life) of your battery
6. Some models provide for multiple voltage inputs (e.g. solar-cell, wind-turbine, or alternator)

Whether a consumer buys into the science and reasons for it, is a choice.

I think its safe to say that I haven't bought the "science"

BTW, in your example of "not much driving", a DC-DC charger would have given you the best chance of keeping your fridge running. Naturally, your $20 battery charger is only useful when you have access to mains power. Often times, I don't have that 'misery' .

Cheers,
LFaR.

In this situation with the Freezer running flat out I would have drained the battery sufficently that for the short time the motor was running the alternator would have been running flat out, you can't makemore power than the alternator can produce no matter how many fancy gizmo's you hook up.

Looks like we will have to agree to disagree on this one Matt.

Cheers Andrew