What dc to dc charger

[sharkcaver]

Morning all. I dont want to get into a debate on dc/dc chargers v's alternator charging here. What I wish to pick your brains on is what dc/dc charger to use and why?

I see there are 3 main contenders

Projecta DC20, 20A output, a pretty basic unit, provides basic isolation from igition circuit sensing, would be a pita for a trailer mount

Ctek D250S, 20A output, more smarts than above and mppt solar input. Provides voltage sensed isolation

Redarc bcdc40, 40A output, Specs similar to the ctek above but higher current otuput.


As I know little about the variances between them, I'd be interested on your thoughts or any others I should also be investigating.

Thanks and regards,

Shane.

[steveandviv]

Morning all. I dont want to get into a debate on dc/dc chargers v's alternator charging here. What I wish to pick your brains on is what dc/dc charger to use and why?

I see there are 3 main contenders

Projecta DC20, 20A output, a pretty basic unit, provides basic isolation from igition circuit sensing, would be a pita for a trailer mount

Ctek D250S, 20A output, more smarts than above and mppt solar input. Provides voltage sensed isolation

Redarc bcdc40, 40A output, Specs similar to the ctek above but higher current otuput.


As I know little about the variances between them, I'd be interested on your thoughts or any others I should also be investigating.

Thanks and regards,

Shane.

Hi Shane. The only thought I have is that 40amps can hurt some batteries and there have been a few comments around the traps on that but I have no way to verify.

[sharkcaver]

Hi Shane. The only thought I have is that 40amps can hurt some batteries and there have been a few comments around the traps on that but I have no way to verify.

I hear ya on that. I agree, the slower the charge the better for life. Still not sure I understand those comments though. As a multistage charger, it will output max amps in the boost stage, but only until predetermine voltage is reached, then current will taper off. I would have thought that unless soc was low, frequently, then this max amperage wouldn't occur often or for long.

That being said, the slower the charge, the better the chance of a longer life.

Just to add a bit more to my original post, I'm investigating running 2 agm's in the new camper. You know I'm not a convert of dc/dc over alternator charge for wet cells, but i think it may have some merrit on multiple agm's.

Anyway, there is a few out there running dc/dc, so I would love to hear your recomendations on what one and why.

Cheers,

Shane.

[marquis]

BCDC1220 if a single AGM
BCDC1240 if dual AGM in parallel or need solar input

These units are compact and can be easily mounted under the bonnet on a metal bracket (search posts here there are some photos of a BCDC1220)

Note the BCDC1240 can draw upto 55A, so make sure you use 16mm2 or larger cable (eg 6B&S, 4B&S, 2B&S, 16mm2, 20mm2, 25mm2) and a 120A anderson plug if to the camper. 50A anderson is underrated for this charger.


If you charge AGM's to fast - they will not charge properly.
You will find a typical 100-130Ah AGM will have a recommend maximum charge rate (eg C/5 or 20Ah for 100Ah - but this can change between manufacturers)

[Lurch]

Why dont you use a simple magneto type set up off the trailers wheels to act as a back up charger?

That said, I have found the Projecta stuff to be pretty bullet proof.

[pauld]

I use a Redarc 40A but it was an easy decision for me as I have 2 x 100AH in the back. If I had one battery I would have been asking more questions of Redarc before I went the 40A over the 20A. I have also had a good run with Redarc products over time and they have always been responsive to questions.

The Redarc does have a battery type input which I have set for AGM.
Even if you didn't need the extra capacity now things might change down the track.

There's not a huge price difference between them - Ebay $393 & $300. I asked Redarc some questions about mounting before I bought and they responded promptly and with good information. The others didn't respond. My questions were about mounting the unit under the rear floor where there was no ventilation, I was concerned that if it was working hard and generating heat on a hot day that with the heat unable to escape things may get too hot for it. They were comfortable to back the product in this situation, there only suggestion was to mount it to metal so I cut away the plastic tub to mount on the metal skin of the underfloor compartment.

The Projecta 20A unit is pretty cheap at around $200 but doesn't appear to have battery type selection..

The Ctek 20A unit is around $260, doesn't appear to have battery type selection but is IP65 (well sealed) rated so good for under bonnet applications. I just noticed on the Ctek website that they have an 80A unit!

[pauld]

Redarc & Ctek = solar input capability.
Projecta - doesn't appear to allow for this.

[pauld]

I hear ya on that. I agree, the slower the charge the better for life. Still not sure I understand those comments though. As a multistage charger, it will output max amps in the boost stage, but only until predetermine voltage is reached, then current will taper off. I would have thought that unless soc was low, frequently, then this max amperage wouldn't occur often or for long.

That being said, the slower the charge, the better the chance of a longer life.

Just to add a bit more to my original post, I'm investigating running 2 agm's in the new camper. You know I'm not a convert of dc/dc over alternator charge for wet cells, but i think it may have some merrit on multiple agm's.

Anyway, there is a few out there running dc/dc, so I would love to hear your recomendations on what one and why.

Cheers,

Shane.

Hi Shane,

As a multistage charger, it will output max amps in the boost stage
Correct.

Needs to be confirmed by an expert but I believe the bulk charging is not neccessarily a problem, I think it is more when it enters absorption / float stages if they continue to increase the voltage to get more current in faster then it can damage the battery / reduce it's life.
In manuals you can get for premium type batteries there detail a recovery charging method that is only supposed to be used occassionally if you have way over discharged the battery & it uses a constant current charge & to achieve this you use a bench power supply with current limiting. You set the voltage high (18 I think from memory) and then turn the current limiting up until you reach the current flow as specified. You sit it at that for x hours and the voltage will rise. This sort of charging regularly is a problem but can be used for recovery.

The Redarc user manual gives some information http://www.redarc.com.au/products/pr...y-charger-40a/

There's also the other factor of often (not always) if you over-rate a product it doesn't work as hard and may last longer.

[wrexy]

I have just bought a 20A MOTOMATE unit from Mallaluka on e-bay. Fairly basic, no mppt but is adjustable for output voltage & current with a bit of mucking around. Nominally set @ 14.2v or 13.8v when purchased. Was going to buy Ctek but for $60 will give this a go first.