Dc to DC charger

Submitted: Monday, May 19, 2014 at 19:26
ThreadID: 107850 Views:2206 Replies:8 FollowUps:11
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Hi All

I'm about to help a Mate put a duel battery system in his Hilux, T/D 06 model. He has bought a Ctek 25A DC to DC charger and was planing on charging his two 130A/HR AGM auxiliary batteries from it.
I have tonged the alternator and it puts out 35A at idle and around 60A at revs you would probably cruise at (I couldn't actually see the Tacho at 60A but it didn't seem unreasonable revs).
Seems like he will be loosing at lot of input to his batteries using this system.
He does have a 80w solar panel, however this could be run without a reg as it won't keep up with the load. Or as he already owns it, he could use it for this should he upgrade his solar to a larger unit in future.
Thoughts?

Thanks

Lyndon
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Reply By: HKB Electronics - Monday, May 19, 2014 at 19:44

Monday, May 19, 2014 at 19:44
I don't actually see what your getting at, the charger will pull around 35A from the Hilux,
it would take around 5 hours for it to recharge the batteries if they were discharged to 70%
SOC.

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Leigh

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Follow Up By: HKB Electronics - Monday, May 19, 2014 at 19:45

Monday, May 19, 2014 at 19:45
Sorry make that 30A

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Follow Up By: Member - lyndon NT - Monday, May 19, 2014 at 19:55

Monday, May 19, 2014 at 19:55
sorry, I didn't make myself clear. My understanding was that the charger would put out a maximum 25A?
Lets say he goes for a drive for 1.5 hours. Will the alternator put in more charge without the charger in the middle or...............?
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Follow Up By: HKB Electronics - Monday, May 19, 2014 at 20:21

Monday, May 19, 2014 at 20:21
If the batteries are going in car, a simple VSR setup with suitable cabling and a booster diode if required would charge them much quicker.

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Follow Up By: Patrol22 - Tuesday, May 20, 2014 at 07:54

Tuesday, May 20, 2014 at 07:54
But it may not fully charge them at all. My Nissan charging system cuts back to a around 13.8 volts once the ECU tells it the main battery is topped up. My auxiliary batteries live in the storage unit in the tub of the ute and this output is not good enough to bring these batteries (2 x 110ah Supercharge AllRounders) back to full charge. I have a Projecta DC20 between the Redarc isolator and the aux batteries an this keeps the charge voltage at a constant 14.4 volts until both aux batteries are fully charged.
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Follow Up By: HKB Electronics - Tuesday, May 20, 2014 at 09:21

Tuesday, May 20, 2014 at 09:21
Patrol22,

I did write "and a booster diode if required"

Why do you have a Redarc isolator if you have a DCDC charger?

The Nissan (I'm assuming a GU model) uses a temperature compensated alternator, it is not ECU controlled nor does it monitor the state of charge of the battery, I'm assuming they haven't changed anything in the 2014 model.

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Follow Up By: Patrol22 - Tuesday, May 20, 2014 at 14:16

Tuesday, May 20, 2014 at 14:16
I had the Redarc isolator fitted to the vehicle and just left it in place when I installed the DCDC charger. The vehicle is a Euro 5 build D40 - I don't know how the alternator works really except that I do know the voltage drops off way before the aux batteries are charged.

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Reply By: olcoolone - Monday, May 19, 2014 at 19:47

Monday, May 19, 2014 at 19:47
Yes a 25amp 12volt charger is a bit on the small side for what your charging.

Thats all I can say.
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Reply By: Ross M - Monday, May 19, 2014 at 19:53

Monday, May 19, 2014 at 19:53
Lyndon
Best make that a, dual, battery system, no good having them fighting each other.

A 25 amp DC/DC will take a long time the charge the two 130ah batts if they are half discharged.

It won't mak eany difference if the alt develops 40, 60 or 80 amps because if the alt is at or more than the DC/DC unit then it can't make charging any quicker.

Depending on where the batteries are located, it might be better to have just a simple VSR to gain maximum input to the batteries for most of the charge and then perhaps use the DC unit to ensure a full top up if that doesn't happen with just the alt doing the job.

I wouldn't run a solar into a battery without a regulator UNLESS I there all the time monitoring the battery with a meter. No set and forget there.
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Follow Up By: Member - lyndon NT - Monday, May 19, 2014 at 20:09

Monday, May 19, 2014 at 20:09
Hi Ross

Yes, no fighting! :-) A lack of education and green cans are a bad mix!
I will be putting in a VSR.
"It won't make any difference if the alt develops 40, 60 or 80 amps because if the alt is at or more than the DC/DC unit then it can't make charging any quicker."
This is what I was thinking.
As for the solar reg, two fridges, 80W panel. No chance of overcharge there.

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Lyndon
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Follow Up By: Ross M - Monday, May 19, 2014 at 20:52

Monday, May 19, 2014 at 20:52
Lyndon
A mate of mine says you always have to have your "greens"

I see your point about the load on the batteries with two fridges.
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Reply By: Member - John and Val - Monday, May 19, 2014 at 20:29

Monday, May 19, 2014 at 20:29
Lyndon,

First - what current the alternator puts out is determined mainly by the load, not by the alternator or rpm.
Secondly - a tong meter is not a good way to measure dc current. I don't think your numbers are meaningful. If they are then your mate has some very big problems!

If the batteries are mounted in a trailer/caravan then the 25A dc-dc charger may be very useful to overcome voltage losses in wiring. Best to minimise such losses by using heavy wiring, but even then a dc-dc charger can be a valuable addition. A bigger one would have been better for 260 Ah of batteries, but 25A will help. Certainly I wouldn't go bigger without checking that the alternator is rated to deliver continuous high current - most are not. That dc-dc charger will draw at least 30A and depending on wiring, maybe 35A from the alternator.

If the batteries are in the vehicle then heavy cable (and a controller IS essential) might be sufficient without the dc-dc charger.

Solar
An 80W solar panel may be some help - depends on the load on his batteries, not on the batteries themselves.

The 80W panel " this could be run without a reg as it won't keep up with the load." NO! There should always be a regulator to manage the panel/s and ensure they don't damage the batteries.

Should he go for more panels? Depends on his actual load (Not the battery capacity, but the actual load on the batteries, fridge, lighting etc.) Probably would benefit from more panels, but depends on the load and on how much of that will be met by the alternator, or by charging from the mains. Which then leads to how much travelling he does each day, does he overnight in caravan parks, does he stop for many days without travelling - hence how reliant is he on solar.

Lots of variables, all requiring some realistic numbers before we can help.

Sorry if that sounds negative, but there's a fair bit to it, and it all starts with an accurate idea of energy requirements and generating options. The expertise and experience is here on this site and we can help...........but not unless we understand the problem!

Cheers

John



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Follow Up By: Member - lyndon NT - Monday, May 19, 2014 at 21:06

Monday, May 19, 2014 at 21:06
Thanks John
I will wait to the green can wear of before commenting to much further :-)
Still can't see the need for a reg with large load and minimal input but happy to be corrected.
They tend to free camp but will be carrying a 1Kva generator.
Surely the current the batteries will draw will be dependent on their state of discharge?
Cable will be heavy enough to negate Vd.

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Lyndon
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Reply By: Member - Phil G (SA) - Monday, May 19, 2014 at 21:51

Monday, May 19, 2014 at 21:51
Gday Lyndon,

The Ctek D250S is only 20 amps, not 25 amps unless there is a new model I don't know about. In any case it will severely restrict the current - won't be able to keep up with 260Ah of auxillary battery, especially with 2 fridges cycling at the same time.

Also the Hilux alternator is 80 amps. So not as good as the 110-150 amp alternators founds in the bigger Landcruisers. But it will do a fair job.

Like you, I use the tongs to measure current to see what's going on. I loaded up a HZJ80 Landcruiser 80A alternator a few years back and measured 80 amps coming out of it. But to hit it with that load continuously might overload the alternator.

Cheers
Phil
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Reply By: Peter T9 - Tuesday, May 20, 2014 at 11:41

Tuesday, May 20, 2014 at 11:41
If your friend is hell bent on using the Ctek he is going to need to use the Ctek smart pass in conjunction. This will provide a higher charge rate during initial charging before switching over to the smart charger for the final stage.

The only problem is cost as the smart pass is about the same price as the D250S.

I run two different battery systems off my vehicle one is controlled by the D250S charging a 105ah AGM which runs a engel fridge only.

The second is controlled by a Narva VSR (about $34) also charging a 105ah battery for a Waeco compressor fridge.

In hindsight I probably could have got away with using the Narva VSR for everything as it is rated at 140 amps however I do like having two separate systems for reliability.
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Follow Up By: gbc - Tuesday, May 20, 2014 at 15:48

Tuesday, May 20, 2014 at 15:48
^^^^ This. A 250 and a smart pass with the panel wired directly into the 250 is a true set and forget system that will make the most out of all situations.
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Reply By: ABR - SIDEWINDER - Tuesday, May 20, 2014 at 12:02

Tuesday, May 20, 2014 at 12:02
Hi Lyndon

Personally I would try get a refund or sell the Ctek. Fit a ABD-Booster-Diode and an isolator at $100 and will do a far better job than the Ctek.

Regards

Derek from ABR
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Reply By: Iza B - Wednesday, May 21, 2014 at 06:14

Wednesday, May 21, 2014 at 06:14
Alternator output alone may deliver a higher amp rate charge current to a deeply discharged battery bank, compared to a DC to DC device. Once the battery develops a surface charge, the charge rate to the battery may fall to not much at all. Probably the fastest way to charge a deeply discharged battery bank is to apply raw alternator output to the bank until the charge current drops below the output capable by the DC to DC charger, then switch to charging by the DC to DC charger. The DC to DC charger develops a high enough voltage to continue to apply the rated current to the battery bank, no matter the voltage level of the alternator. One hands-off way to do this is to use the Smartpass and the D250S.

Iza
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Follow Up By: Member - lyndon NT - Sunday, Jun 01, 2014 at 13:35

Sunday, Jun 01, 2014 at 13:35
I am about to post an update and would be interested to hear your thoughts.

Cheers

Lyndon
Now is the only time you own
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Place faith not in tomorrow
For the clock may then be still

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