Installing DC/DC Charger

Submitted: Friday, Nov 18, 2011 at 02:07

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Member - John (Vic)

I'm just about to install a Redarc BCDC1240 DC/DC charger to boost voltage to my two 120 amp AGM batteries.

The instructions say I need to put a 50A fuse on the input as well as the output positive line.
Meaning the charger is effectively straddled between the two fuses.

All this is fine, and I was looking to use a pair of ANL fuses obviously with the respective holders, can anyone suggest anything better than the ANL fuses or are these fine for this situation?
I want something that is surface mountable and easy seen if a fuse blows.
the only negative I can see is the ANL fuses themselves are a bit costly if you happen to blow a couple for some reason.

Suggestions appreciated.

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Reply By: Member - Toyocrusa (NSW) - Friday, Nov 18, 2011 at 06:49

Friday, Nov 18, 2011 at 06:49

Hi John. Might be worth asking Redarc if they have something suitable.
My van has a large fuse on the positive side of the battery that has a blade fuse in it. Haven't looked at it for a while but the amperage would have to be 50. Will take a photo over the weekend. Cheers,Bob

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Reply By: Member - John and Val - Friday, Nov 18, 2011 at 07:23

Friday, Nov 18, 2011 at 07:23

John,

I used a 50A circuit breaker from ABR Sidewinder with my 30A dc-dc charger.

Something worth noting - to deliver 40A, the charger draws a fair bit more than that from its supply. In normal operation it may well be pushing towards 50A - this can be hard on a 50A fuse, and especially on a 50A alternator. I fitted a 70A alternator to handle this.

Cheers

John

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Follow Up By: Member - John (Vic) - Friday, Nov 18, 2011 at 19:34

Friday, Nov 18, 2011 at 19:34

Hi John
The Troopy has a 110A alternator so thats not an issue.
I currently have two 25mm square welding cables as my battery leads from the start battery to the two AGM which are mounted in the rear of the Troopy so my supply lines are also more than adequate.

My issue has been the same as everyone else the Toyota alternator drops back and runs at around 13.4 to 13.7 volts so the AGM's are not getting enough to get them fully charged, hence the DC/DC charger to help.

Redarc say to fit 50 amp fuses for the 40 amp charger, I was going to use theANL Fuses (Scroll down the page to see) as they will make the joint interface between the 25mm square cable and the charger easier to deal with being different sizes.

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Reply By: Member - Alastair D (NSW) - Friday, Nov 18, 2011 at 07:57

Friday, Nov 18, 2011 at 07:57

John,
As suggested good to use circuit breakers then you don't need to carry spares. One thing is that it is best to NOT use the auto resetting type in your application. If they blow then there is a problem that needs to be fixed before resetting.

cheers

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Reply By: Member - Nolo (Brisbane) - Friday, Nov 18, 2011 at 08:19

Friday, Nov 18, 2011 at 08:19

I am also a fan of the ABR Circuit Breaker / Trip Switch as the charger device is easily isolated as a switch as well as offering fuse protection.

ABR switch

Greg N

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Follow Up By: Member - John (Vic) - Friday, Nov 18, 2011 at 19:36

Friday, Nov 18, 2011 at 19:36

Thanks Greg, I haven't discounted the use of circuit breakers as yet.
I did have a preference for being able to surface mount the fuses/breaker.
May keep looking to see what else is available.

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Reply By: olcoolone - Friday, Nov 18, 2011 at 08:48

Friday, Nov 18, 2011 at 08:48

When we do BCDC installations we use Maxi fuses rated at 50amps and solder the fuse holders into the input and output wires..... we also wire rap the connections before soldering and heat shrinking using dual wall adhesive heat shrink.

You can use circuit breakers if you want but you also have to find a spot to mount them whereby maxi fuses are in line...... we find over time the cheapy metal or plastic can type circuit breakers fail due to water and corrosion entering them or the spot weld holding the bimetal strip in place breaking.

If done right a fuse should not blow, we mostly find fuses blowing due to shonky workmanship or under rated fuses and fuse holders.

You have to also install a 70amp 5 pin change over relay and relay socket triggered by an ignition feed if you want to use solar inputs.....

We also recommend using minimum 8B&S cable for input, output and earth wires, 6mm for solar inputs and all the rest 3 or 4mm wire..... connect all earths to one location only (battery - or dedicated body earth point.

Spray all connections including the relay with a quality silicon electrical spray grease... this also includes the heat shrinked joints after shrinking.

We also try and mount the BCDC in front of the radiator for maximum airflow to help with heat dissipation.

Hopefully this may help you.

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Follow Up By: Mick O - Friday, Nov 18, 2011 at 10:18

Friday, Nov 18, 2011 at 10:18

I'll vouch for Richards installation methods and recommendations. 30,000 HARD kilometres on my set-up now and worked faultlessly. Very nice set-up.

Mick

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Follow Up By: Member - John (Vic) - Friday, Nov 18, 2011 at 19:43

Friday, Nov 18, 2011 at 19:43

Thanks Richard, good info appreciate your reply.
I was going to mount the charger in the rear near to where the AGM's are mounted.

My biggest issue as I mentioned above in my reply to John is that i have used 25mm square welding cable from the front isolator to the two batteries in the rear and thought the ANL fuses may be a easier and cleaner set up the use as the joiner between the charger leads and the heavier cable.
I really don't want to pull that cable out to go down to a 6 or 8B&S cable.

Will fit the relay a bit later when I move to solar panels.

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Follow Up By: olcoolone - Saturday, Nov 19, 2011 at 09:53

Saturday, Nov 19, 2011 at 09:53

Yes your cable size is OK and there is no need to replace it.

On larger installs we use MEGA fuses and fuse holders.

What battery isolator do you use?

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Reply By: Member - Captain (WA) - Friday, Nov 18, 2011 at 10:44

Friday, Nov 18, 2011 at 10:44

I have the BCDC 1240 and have found the 50A fuse too small for the power in side. Its a long cable run from the vehicle battery to the van and at peak output mine draws some 55A. Also, as the engine bay gets quite warm, it results in the breaker tripping a bit earlier than the the rated 50A, hence two reasons for the change to a larger breaker.

The 1240 is a great bit of kit, the MPPT solar controller also works well on my 160W panels, very happy with the Redarc. And make sure you use decent size cables.

Cheers

Captain

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Follow Up By: Member - John (Vic) - Friday, Nov 18, 2011 at 19:48

Friday, Nov 18, 2011 at 19:48

Good info Skipper.
Was was mounting the charger in the rear close to the batteries so it should negate any heat issues.

Cables are not an issue as I mention above.

So what size breaker are you running on the power in side of the charger and what model breakers are you using?

Going to be over your neck of the woods over the December - January period.
Give us a wave if you happen to see me around :))

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Follow Up By: Member - Captain (WA) - Friday, Nov 18, 2011 at 22:05

Friday, Nov 18, 2011 at 22:05

Hi John,

Will look out for you and give a wave :)

The idea of mounting the Redarc close to the batteries being charged is to minimise voltage loss from the cables. If you install the Redarc in the engine bay and then run cables to the van, you will lose too much voltage and waste the higher voltage the Redarc produces. By installing as close to the batteries being charged as possible (mine is less than 1m), you will have minimal voltage drop and charge the batteries properly.

Initially, I installed a 50A breaker in the engine bay and another 50A after the Redarc, but before the batteries. The one in the engine bay kept tripping so I installed my spare, thinking the original was faulty. It too kept tripping so when I worked out the current required it was 55A (approx 40A @ 14V required 55A @ 10.5V) - the breakers were doing the job!

So, I added the spare 50A breaker in parrallel (gives 100A) and this has worked fine ever since :) I used the plastic cased grey ones, about the size of half a matchbox or thereabouts. Not the highest quaity in the world hence why I carried a spare. But having said that, I have never had an issue with them after using this type of breaker for many, many years.

Cheers

Captain

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Follow Up By: olcoolone - Saturday, Nov 19, 2011 at 10:18

Saturday, Nov 19, 2011 at 10:18

Captian is you wiring capable of handling 100 amps?

If your seeing 10.5 volts on the input side there is something wrong big time with your wiring.

As I said below there is no substitute for bad workmanship and no matter what you do there is no excuse for lack of capacity.

Bit like building a two story house on a single story foundation..... no matter what you do it will come back and bite you!

This is why you need a bigger fuse then we do...... fix the supply problem first.

And rule of thumb calculate the fuse to be 25% bigger then the supply current.... not 100% as in you case.... this is asking for trouble.

Circuit breakers allow 15-20%

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Follow Up By: Member - Captain (WA) - Saturday, Nov 19, 2011 at 12:50

Saturday, Nov 19, 2011 at 12:50

Olcoolone, I suppose your ignorance of my installation is only matched by your impliction of poor workmanship!

I use 63mm2 double insulated wiring on my vehicle because not only does it power my van, it also powers two engels (1 runing as a freezer so mostly on), water pump, air compressor and inverter. From the distribution block in my rear drawer system, one cable feeds my van while other cables feed the above items (all individually fused appropriately).

While I ordered my van to have 20mm2 wiring, due to an unfortunate mixup it only came with ~9mm2 wiring so has a higher voltage drop than desired. However, it is still capable of handling 100A so all good there.

As for installation quality, all terminations are properly crimped (I have my own hydraulic lug crimper + ratchet crimpers + MC4 crimpers for solar work), silicone sprayed, heat shrunk and placed in convoluted tubing and cable tied as approriate. All lugs have boot covers, as do all circuit breakers. As part of my profession, I have inspected internationally industrial electrical cabinet wiring for process equipment, so am more familiar than most on what must be done and what is nice to be done.

Perhaps its better to get the full picture before you make dispariging comments about installation quaility?

Cheers

Captain

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Follow Up By: olcoolone - Saturday, Nov 19, 2011 at 15:18

Saturday, Nov 19, 2011 at 15:18

I based my assumption on the fact you have used circuit protection way over what is needed..... why would you use 100amps of protection when all you need is 55 amps as stated by your self.

Someones mistake on your caravan is no excuse for you not correcting it...... seeing your an expert with all the you bute gear to be able to do it yourself!

Why haven't you corrected their so called mistake?

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Follow Up By: Member - Captain (WA) - Saturday, Nov 19, 2011 at 17:06

Saturday, Nov 19, 2011 at 17:06

Olcoolone, it may help to read my post properly before replying with another self rightheous post of why my installation doesn't meet your "standards". Not only have you not seen my installation, nor have you seen my van, but somehow from my simple post that has a lack of engineering detail you now "know" what the "mistake" is on my van and are critical that I haven't corrected it yet, as I have all the "you bute gear".

You have no idea what has been done with my van, nor why there were changes or if they have been corrected. But you somehow know what needs to be done???

No wonder people run a mile from electrical threads when self appointed experts pounce on a simple post commet and turn it into something bigger than Ben Hur and nothing to do with the original post.

Sorry John for this thread getting so off track, its an unfortunate but regular occurence on any electrical thread on virtually any forum, its not just ExplorOz that has these self appointed, vested interest, electrical posters.

Cheers

Captain

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Reply By: Sand Man (SA) - Friday, Nov 18, 2011 at 19:40

Friday, Nov 18, 2011 at 19:40

Reading the replies above, I am rather supprised that the Redarc BCDC1240 is installed at the beginning of the circuit run rather than the end.

I would have thought the whole idea is to have the DC/DC charger as close as possible to the remote battery end to overcome voltage drop issues, etc.

This is the way I have installed my CTEK D250s Dual DC/DC Charger.
Dual input for alternator and/or solar panel inputs and the charger is mounted at the service (auxiliary) battery end.

Bill

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Follow Up By: Member - John (Vic) - Friday, Nov 18, 2011 at 19:50

Friday, Nov 18, 2011 at 19:50

Yeah Bill agree, I'm mounting it in the rear close to the batteries.
I have very heavy supply cables already in place so voltage drop is minimized and current draw is not impeded to any degree.

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Follow Up By: Sand Man (SA) - Friday, Nov 18, 2011 at 21:57

Friday, Nov 18, 2011 at 21:57

G'day John,

Mine is quite an interesting setup.
I have a Sidewinder Flyer in the rear of my dual cab which acts as my auxiliary to run the Engel portable fridge when travelling.
Since purchasing my new camper I have introduced another two batteries and a Waeco Upright fridge to support.
I can connect an extension cable from the output port on the Flyer and connect this up via anderson connectors to the input cable on the camper. This worked OK but I was unsure how much charge was going into the two 80Ah batteries in the camper, thus I introduced the CTEK D250S charger. This accepts whatever it is receiving from the alternator, then boosts the voltage level if required, so the batteries are getting an optimal charge rate.
I also have heavy cable from the primary battery to the Flyer, then from the Flyer to the D250S in the camper.

Bill

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Follow Up By: olcoolone - Saturday, Nov 19, 2011 at 10:08

Saturday, Nov 19, 2011 at 10:08

If your using a larger cable then what is needed then voltage drop would be minimal.

There is no excuse for not designing and using the correct gear and no matter what you do nothing will overcome a shortfall or shonky workmanship.

The main idea of any DC-DC charger is not to overcome a wiring problem but to charge the aux battery correctly and more efficiently than a standard automotive alternator can.

If the wire to the aux battery has a unacceptable voltage drop this will also affect the DC-DC charger input by supplying a lower voltage and an increased current demand.

The lower the voltage the higher the current demand is and if a wire can not supply this current then the hotter it gets.... the hotter it gets the higher the resistance is....... higher resistance = lower voltage.... lower voltage = more current.... more current = more heat...... and it just keeps getting hotter until something gives.

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Follow Up By: oldtrack123 - Saturday, Nov 19, 2011 at 10:41

Saturday, Nov 19, 2011 at 10:41

Hi Sandman
RE ;" would have thought the whole idea is to have the DC/DC charger as close as possible to the remote battery end to overcome voltage drop issues, etc. "

Yes you ARE correct
A dc to DC charger functions is to boost the charge voltage from the alternator
But if part of it is lost due to voltage drop in the feed line from charger to battery you have lost SOME of the gain

Yes LARGE cables can /does minimize voltage drop BUT it cannot ever be completely removed.

The BEST place for ANY DC to DC chargere IS AS CLOSE TO THE BATTERY BEING CHARGED AS POSSIBLE.
The charger also then senses a more accurrate SOC reading from the remote battery

The longer the distance the more important this all become

Peter

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Follow Up By: olcoolone - Saturday, Nov 19, 2011 at 11:51

Saturday, Nov 19, 2011 at 11:51

Peter your talking a voltage drop of maybe 0.1v - 0.2v if using good size cable and if installed correctly.

Your splitting hairs Peter.

Many DIYers carry out installs far from being professional and to a standard.

The difference between sensing is much the same.... 0.1v to 0.2v.

It must be wonderful to live in a perfect ideal world that some spend their life in.

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Follow Up By: olcoolone - Saturday, Nov 19, 2011 at 11:57

Saturday, Nov 19, 2011 at 11:57

Bill this original post was for a aux battery mounted in a vehicle and this is what my reply was based on, the ideal solution is to have two DC-DC chargers..... one for the vehicle and one for the camper..... vehicle one mounted in the vehicle and the camper one mounted in the camper.... cable lengths are short and will have minimal impact on performance.

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Follow Up By: oldtrack123 - Saturday, Nov 19, 2011 at 14:57

Saturday, Nov 19, 2011 at 14:57

Hi olcoolone
With the Aux in the vehicle the voltage drop may be minimal

But to a battery in a van the run length is considerably longer & includes connectors .
Why not put the DC to DC charger where it is most effective no matter what the cable size
I do agree many ,including auto electricians, do not understand the effects of voltage drop due to undersized wiring on extra low voltage equipment .

One needs to consider that that longer feed cable from the charger to the van battery may be supplying other loads [fridge etc]which will further give an incorrect reading of SOC
Not the correct way to wire But is the way it is often done
THAT little point seems to be missed by many

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Reply By: Member - John (Vic) - Friday, Nov 18, 2011 at 19:51

Friday, Nov 18, 2011 at 19:51

Excellent info guys, all very helpful.
Thank you all any further comments etc appreciated.

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Reply By: Member - Murray R (VIC) - Friday, Nov 18, 2011 at 22:59

Friday, Nov 18, 2011 at 22:59

John
As you have the welding cable running to the batteries, you could use a insulted battery stud to step down in cable size by using the appropriate cable lug per cable. I also agree with Richard and would use Narva Mazi fuse holder and 60 amp fuse at both batteries. The maxi fuse and cable is about 300mm long so should be able to mount the stud at batteries. I think narva also make the insulated battery stud which you could buy at Bursons.
Just another suggestion
Murray