Dc to DC Charger

bazzle22 · Veteran Member

Dc to DC Charger

Happywanderer · The Master

You are right there Barry. The alternator won't fully charge the house battery, I travelled about 400 ks after my battery had gone down four bars on my gauge, the battery didn't charge at all.
I plugged into son in laws shed and put my C Tek charger on the battery, was fully charged over night.
Unfortunately if you are out bush camping you won't have power to plug into, but maybe could do it through a generator.
You won't need the C Tek charger if you have the solar panel as the connections go straight to the battery and charge that way.
That is my next job, to get a solar panel fitted for exactly that.
Hope I have explained that adequately.

bazzle22 · Veteran Member

Hi Guru,

Thank you for your response. I must have got my wires crossed. I thought the "DC to DC...." title meant that it would mount between the alternator and my batteries, and ensure a full charge would occur (somehow) as I drove along. Then I would atleast start with a fully charged battery when I setup for camping. ??

Thanks, Barry

Happywanderer · The Master

Yes they are connected to charge from the alternator but as my son in law explained the alternator charges the drive battery first and also my house battery being a 120 AGM Deep Cycle , he said it would never charge which I proved before taking up his original offer to use his power and my c tel charger to finally get it charged after a week of long trips trying to charge with the alternator.
By the way, its Happy Wanderer or HW for short. Guru is my status.

PeterD · Guru

With 2 batteries in your tug I would suggest something bigger than the D250S. There is a good range on this page.

UPO · Veteran Member

Evening Barry - yes the Ctek dc-dc ( D250s ) fits between the vehicle power supply from alternator & the van battery - I was advised that the Ctek should be close to the van battery AND connected with good sized ( read here BIG biggrin ) cable - will also connect solar up to the 20AMP Ctek limit - has the "smart" solar controller built in - MPPT I think it is called.

Very limited experience but certainly the van battery came up well from the vehicle charging while driving - over 13V from memory -

another plus is that the Ctek will not allow current to flow from van battery back to the tow vehicle.

Bought mine from Peter in Townsville recently for $255 - do a google search - he will come up very near the top & was the best price when I bought AND prompt in e-mailing answers to what are probably very basic questions. Just a happy customer.

Happy Charging

UPO - Richard

wasn_me · Guru

You won't fully charge an AGM house battery from the vehicle alternator if not using a smart DC-DC charger, eg 250s dual.

If the only method of charging is directly from the alternator you might as well fit a wet cell deep cycle battery, (lower cost) as you won't get the advantages of the AGM.

As Peter D suggests with 2 house batteries a larger DC-DC charger would be better.

You can connect your solar to the 250s dual. This then acts as the regulator, so make sure the solar doesn't already have a regulator.

A battery can not charge in a short time. The higher the battery voltage gets the more it limits the input charge. Probably something like 4-8 hrs charge is required, depending on the state of discharge.

Cheers Pete

-- Edited by wasn_me on Thursday 8th of August 2013 03:14:34 PM

justcruisin01 · Guru

bazzle22 wrote:
HI,
I have 2 Exide Extreme (dual purpose) batteries in my Pajero, and use an umbilical cord to feed the Van when free-camping. I find that the charge rate of these 2 batteries is often not what I would like them to be, and I need to go for a drive each day to top up. I have no other way to charge.
I have heard that the alternator will not fully charge a battery, and having 2 is perhaps even worse. I have heard people talking about a Ctek DC to DC charger, and would like to know if this makes a worthwhile difference. I also understand that the charger can work in conjunction with solar panels. I am looking at getting a 120W portable set, and hope to maintain the battery charge at a better level while camping.
Can members please advise how all of this works, and how it can be set up by a handyman.
Thanks, Barry

-- Edited by bazzle22 on Wednesday 7th of August 2013 09:09:35 PM

Barry; mate you are on the right track with what you are saying.

I fitted a Redarc 20amp DC_DC , & yes they are fitted between the start battery & your aux batt, & do a very good job.

I, like you doubbled up on the aux batteries, (2) , while the DC_DC still worked well I needed a full day drive to bring them back up to full.

Note;; I am running a large frreezer so power consumpion is a lot more than just as a fridge.

Hence, on a shorter day drive the batteries were not full.

I had aquired a second Redarc 20amp DC-DC , so I fitted them in parallel, now works perfect.

Note;; in doing this I had to fit a small master switch between the two batteries so as to be able to seperate them when travelling to allow each charger to read correct voltages, worked perfect.

Now, dont know about other brands but the redarc now do a 40amp DC-DC with solar as well, this will be the go for you.

I have just removed this system from my old tug & instaled it to a new tug , all is working well.

I also weny to the effort of installing a volt & amp meter to each unit so I know exactly what is going on. I can see the switch point between bulk & abs charge as I drive, the volt mtrs are also usfull when parked to observe the battery levels.

As for alternator charging while you travell in a direct connection, this will never happen with one batt, let alone two.

Cheers mate;

JC.

Happywanderer · The Master

Thanks for clarifying that JC. Has also helped me see what is wrong with my system which I haven't finished working on yet.

The dog lady · Guru

I didn't understand all this stuff either, and left it to my son to work out with his regular battery supplier. He normally outfits boats but I figured he'd know what to do for the camper van too. He's setting me up with a large gel battery which they told me will need to be charged for about 3hours (with the 40A redarc running off the genny ) every 3 days based on what I use. This will be a lot better than running the Genny for hours every day to keep the fridge cold, and apparently I can add a solar panel to charge it when I'm ready.

Now I understand why they told me I can't charge it while driving. always more to learn smile .

justcruisin01 · Guru

You should have a DC-DC fitted so you have a fully charged battery when you arrive at destination.

PeterD · Guru

There are a few things to remember when using a DC-DC charger, or for that matter any charger, when you want your batteries charged quickly. Firstly you should select a charger that is capable of supplying an output of C/4 or as close to as possible. The smaller the charger the longer the time required to charge your battery. You also want it too big or your alternator wil not be able to supply the necessary input current.

Secondly you should use a fairly large cable to the charger. The more voltage drop you have in the cable the greater the current that be required to drive the charger to its full output. If the voltage drop is to large then the alternator may not be able to supply the extra current.

The Ctek D250S is fine for batteries in the 80 - 100 Ah. They are starting to get a little marginal for 110 -120 Ah batteries. For anything larger then you should be looking for something larger.

PeterD · Guru

JC, your last post sounded like you thought I was having a go at you. I was not having a go at you, I was just stating general principles for all to take note of. Your total of 40 A charge capacity is probably as much as your alternator will accommodate. Your set-up sounds appears to generally follow my guidelines.

-- Edited by PeterD on Tuesday 20th of August 2013 12:02:31 AM

justcruisin01 · Guru

The 20amp Redarc's into 100amp batteries with the correct wiring & location are working extremely well.

two x redarc 20amp into two x100amp batteries, isolator switch for when travelling to allow individual charging & batteries reconnected when stopped.

JC.

justcruisin01 · Guru

PeterD wrote:
JC, your last post sounded like you thought I was having a go at you. I was not having a go at you, I was just stating general principles for all to take note of. Your total of 40 A charge capacity is probably as much as your alternator will accommodate. Your set-up sounds appears to generally follow my guidelines.

-- Edited by PeterD on Tuesday 20th of August 2013 12:02:31 AM

Not at all Peter, I understood your info & agree with your statment.

I was only sharing what I had setup & that this system works well.When I first fitted a DC unit with one battery it was great,(I dont think they had the fourty amper then) I added a second battery & yes found that it was a good days drive to recharge the two batt.

In the meantime I had aquired a second Redarc 20amp from the company at no charge so I duplicated the system & had a winner.I now believe I have a better system than having the fourty amper unit, if one fails I still a funtional system & same with being able to seperate the two batteries.

My Tojo has a 80amp alt, the new tug has a 110amp alt.

Cheers mate;

JC.

-- Edited by justcruisin01 on Tuesday 20th of August 2013 07:36:20 PM

RobC · Member

Hi guys when you finish can you tell me how to test a dc dc i have a project and it went down to 11v cloudy but only running fridge took for run and no help so i hard wired the solar up and its now 11.3 but raining!! But did go up i dont know how to test to see if stuffed im realy stint and would hate to chuck . 115 battery 250 solar 4cyl car smart battery thanks

Jaahn · Guru

Hi smile

There is a collection of information and disinformation here in this thread. How will someone new sort out which is which ????????????

Firstly RobC, time to buy a multimeter and learn how to use it or get someone who does to check it out.

Of course the tug alternator will fully charge batteries, how the hell do you think the normal fitted battery lasts ?? hmm But in recent years the use of 'smart' alternators which drop the voltage after some short time has made it difficult to charge a 'house' battery properly. If you have an old style alternator you can just charge a second battery easily, I do that and have for years in my last two MHs.

So to charge a second battery from a 'smart' alternator they developed DC to DC chargers which accept the lower voltage at the alternator and 'boost' it to a suitable voltage and manage it to fully charge the second batteries. confuse However they are limited in the amps they put in so the 20 A ones may not be enough if you have two batteries and use them a lot. EG two 100AHr batteries run down to 50% will need 100AHrs to recharge, @20A that will be 5 Hrs to nominally recharge them. So you will need to run the tug for at least 5 Hrs still and actually a bit longer for fully topping up. 40A will need half as long.

In my opinion the statement about AGM batteries not being as good as normal LA batteries is not right. They charge perfectly from the old alternators and work well and I would recommend them for house batteries with any charging system.

So adding solar is the answer IMHO. I have that and it works well too without running the motor. Works from sunup to sundown. Sorry if it rains sometimes, then run the motor or go to a caravan park biggrin

Cheers Jaahn

PS any charging system but particularly solar will be compromised by wiring which is too small. It is a usual common problem. Spend $20 more and double the size of the wires and relax in the knowledge it will work well.

-- Edited by Jaahn on Thursday 14th of June 2018 09:44:26 AM

-- Edited by Jaahn on Thursday 14th of June 2018 11:02:34 AM

T1 Terry · Guru

RobC wrote:
Hi guys when you finish can you tell me how to test a dc dc i have a project and it went down to 11v cloudy but only running fridge took for run and no help so i hard wired the solar up and its now 11.3 but raining!! But did go up i dont know how to test to see if stuffed im realy stint and would hate to chuck . 115 battery 250 solar 4cyl car smart battery thanks

Hi Rob, difficult when you tag a new question on to an old thread because some think it is still part of the same ongoing discussion. I've learnt to look at the posted dates after going head long into something that was done and dusted many yrs ago :lol:

As far as the problem you have at the moment. What type of DC to DC charger? Not sure if you are saying you have a project or you have a Projecta DC to DC charger. The most common problem is undersized wiring from the tow vehicle battery through to the DC to DC charger, the next is bad connections at the Anderson plug. First thing is to check the input voltage at the DC to DC charger when it is off and again when turned on. The DC to DC is unlikely to work well if the input voltage drops much below 10v and if it is around 11v you really still need to find out why by checking both the things I mentioned above.

If the input voltage is the same as the tow vehicles battery voltage or close to it, the DC to DC is most likely not working, check the output voltage at DC to DC and see if the voltage is the same, higher or lower both with the DC to turned on and with it turned off. No rise in output voltage when turned on confirms the DC to DC is not working.

If you have confirmed the DC to DC charger is not working, check there is a voltage signal at the ignition sense wire, if it doesn't see this it will not turn on as a DC to DC charger. If there is an ignition sense voltage the next thing is fuses. There are fuses inside the DC to DC charger, these would be the next things to check. If they are ok, the input voltage is better than 11v, there is an ignition signal at the sense wire and the output voltage doesn't improve when the DC to DC charger is turned on it would be safe to say the DC to DC has died.

T1 Terry

Delta18 · Guru

T1 Terry wrote:
RobC wrote:
Hi guys when you finish can you tell me how to test a dc dc i have a project and it went down to 11v cloudy but only running fridge took for run and no help so i hard wired the solar up and its now 11.3 but raining!! But did go up i dont know how to test to see if stuffed im realy stint and would hate to chuck . 115 battery 250 solar 4cyl car smart battery thanks
Hi Rob, difficult when you tag a new question on to an old thread because some think it is still part of the same ongoing discussion. I've learnt to look at the posted dates after going head long into something that was done and dusted many yrs ago :lol:

T1 Terry

Hi Terry, rather than start a new DC-DC Charger thread I'll add to this one albeit a few months later lol.

You well know the 40a dc-dc I have. What would the current draw on this unit be?

As you may recall I have a 100a Thermal Circuit Breaker under the bonnet of my car which occasionally cuts out, as you said, probably due to UnderBonnet heat.

Should I replace this CB with a heavier unit? ie: 150a or such? I am trying to avoid going to a simple Fuse type CB or moving the existing one.

Where it is situated there should be sufficient airflow to prevent ambient heat causing it to 'throw out' unless it's current draw is close to tripping it anyway.

Cheers Neil

T1 Terry · Guru

Hi Neil & Lynne, hope all is going well over that side of the island with all the rain. You have a 40 amp DC to DC and a battery system that could potentially 14.4v in an extremely rare event. 14.4v x 40 amps = 576w. Add 10% for losses through the DC to DC charger cause nothing is 100% efficient and that brings it up to 633w. For convenience let's round that up to 650w. Now the DC to DC will output that 40 amps with an input voltage down as far as 10vdc, 650 divided by 10 = 65 amps. The 6 B&S cable will handle 100 amps continuous so the cable is fine with that load so aim the protection at what the cable needs to protect it against catching fire, 100 amps, so go for that.
You can persevere with DC circuit breakers if you want to, it's your time and money, but a 100 amp midi or mega fuse and holder would be a one time fit and forget and would only fail if it had to protect the cable. Good quality fuses don't suffer from vibration, heat stress, dust inclusion or arcing across the contacts increasing the resistance and heat generated until they either de-rate to the point of continually tripping or weld themselves closed and don't trip when needed.
It's not like you need the ability to turn the circuit off at regular intervals and that is the only advantage a circuit breaker has over a fuse.
Let's face it, if the circuit breaker nuisance trips it has proved it isn't up to the task, so the ability to press button reset is a moot point, if it tripped doing the same job as a fuse would have done then the ability to press button reset it is of no value is it, there is dead short some where in the cabling that needs to be fixed.

T1 Terry

Delta18 · Guru

T1 Terry wrote:
Hi Neil & Lynne, hope all is going well over that side of the island with all the rain. You have a 40 amp DC to DC and a battery system that could potentially 14.4v in an extremely rare event. 14.4v x 40 amps = 576w. Add 10% for losses through the DC to DC charger cause nothing is 100% efficient and that brings it up to 633w. For convenience let's round that up to 650w. Now the DC to DC will output that 40 amps with an input voltage down as far as 10vdc, 650 divided by 10 = 65 amps. The 6 B&S cable will handle 100 amps continuous so the cable is fine with that load so aim the protection at what the cable needs to protect it against catching fire, 100 amps, so go for that.
You can persevere with DC circuit breakers if you want to, it's your time and money, but a 100 amp midi or mega fuse and holder would be a one time fit and forget and would only fail if it had to protect the cable. Good quality fuses don't suffer from vibration, heat stress, dust inclusion or arcing across the contacts increasing the resistance and heat generated until they either de-rate to the point of continually tripping or weld themselves closed and don't trip when needed.
It's not like you need the ability to turn the circuit off at regular intervals and that is the only advantage a circuit breaker has over a fuse.
Let's face it, if the circuit breaker nuisance trips it has proved it isn't up to the task, so the ability to press button reset is a moot point, if it tripped doing the same job as a fuse would have done then the ability to press button reset it is of no value is it, there is dead short some where in the cabling that needs to be fixed.

T1 Terry

Thanks for that, convinced I am. Off shopping again.

All good over here, pity I sold my boat, could have been useful for going out to check on the van some days ha ha.

We are back over your way again late this & early next year. Will call in if suitable.

Cheers Neil