Hilux battery system (CTEK Smart pass-D250S) Voltage drop/cable size

Submitted: Sunday, Jun 01, 2014 at 18:18
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Hi All

I posted a thread on the 19-5 re DC-DC charging and setting up a battery system in a mates Hilux. Just wanted to post an update of what we have planned and see if anyone can see any major issues.
As a coincidence the battery and the alternation died last week and both have been replaced. Auto electrician said voltage output was only 13.2v with new alternator and that this wouldn't fully charge the AGM's we are putting in the car. Interestingly when I put my multimeter on the battery terminals it showed 13.8v, thoughts anyone? I tested my Troopy and it registered 14.2v at battery so it seems like the Landcruiser alternator might charge at a higher rate.
Two 130A/h AGM's will be going in the far left rear of the tub, a tight fit, we have made up a tray and all seems good on that side of things. We will be using the CTEK D250S dual and Smart pass.
Just so I understand this right, this will raise the charging voltage from the alternator whilst it charges the batteries up to 80% give or take a bit, it will then switch over to the DC-DC function of the D250S duel for the final top up of batteries, it will then switch and bring the starting battery up. We will also be having two 50 Amp Anderson plugs under the rear tow bar. One will feed solar from a 80W panel via the CTEK whilst the other will go directly to the batteries for use with a CTEK 25A charger ran from either mains or generator as needed.
I think the above is correct but if anyone can see any issues or that I've misunderstood anything please feel free to comment.
My mate bought some cable from an auto supplier the other day but I am concerned it may not be large enough. It is 6AWG or 13.5mm2
Depending on which route the cable takes we will either be looking at a 5 or 7.5 metre run. Mate wants to bring cable into tub behind rear left tail light (7.5 m run), or we can shorten it by bringing up through tube floor but he doesn't really want to do this. It would be a 7m run to the smart pass then a .5 m to the batteries, then 6 metres back to fuse box under bonnet. As the draw from accessories wont be real high, say max of 10A I think the
13.5 mm2 back to the fuse box should be fine? They have then supplied him 8 B&S or 7.91mm2 to run from fuse box to his various sockets he plans to put in. The longest run (I hope) will be around 6 metres to the furthermost socket. Calculating the Vd from batteries to fuse box and then adding this to cable to sockets, I come up with around .15Vd, so should be fine.
I am concerned however that the draw from the two batteries when discharged will be quite high and that 13.5mm2 will be inadequate. Though this is of course the whole idea of what we are hoping to achieve, a high charge rate. Thoughts on this?
By my calculations if the batteries are drawing 80A (and providing the above system can provide this) to keep Vd to .193v (this is to the smart pass then + 50cm to batteries) I would be needing to use 0B&S or 49.2 mm2. This is also calculated at 25c and it is bound to be hotter than this. At 40c it would be .224v
Collyn Rivers states that .15-.2 Vd is acceptable. If I go to 1 B&S at 40c Vd would be .279v. B&S 00 or 64.9mm2 will see a Vd of .182 If I allow for the full 7.5 Metres from front battery to rear via the smart pass.
Or am I completely mistaken and the smart pass and charger are going to render my ramblings above irrelevant? If so please explain.


Thanks

Lyndon
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Reply By: Member - lyndon NT - Sunday, Jun 01, 2014 at 18:26

Sunday, Jun 01, 2014 at 18:26
I've just been pulled up on some spelling, that would be alternator and Tub floor :-)
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Reply By: Peter T9 - Sunday, Jun 01, 2014 at 18:32

Sunday, Jun 01, 2014 at 18:32
I dont think the CTEK will charge up your start battery however it will isolate it from your other batteries when the alternator is stopped.

DON'T mount the CTEK under the bonnet, put it in the cab or tub with the AGM's.

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Follow Up By: Member - lyndon NT - Sunday, Jun 01, 2014 at 21:33

Sunday, Jun 01, 2014 at 21:33
Yep, both charger and smart pass will be going in tub.

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Reply By: HKB Electronics - Sunday, Jun 01, 2014 at 19:33

Sunday, Jun 01, 2014 at 19:33
The smart pass won't charge your starter battery, the smart pass is a two part system, part 1 is a simple VSR, it connects the alternator straight through to the auxiliary battery to charge. When the charge rate drops below 20A the VSR part turns off and the DCDC charger will kick in. The DCDC will boost then gradually increase its output voltage up to a maximum of 14.4V@24C this will occur at around the 80% SOC point, from then on it will hold that voltage and the current will gradually reduce till the battery is fully charged.

If you fitted one of my booster diodes to your Lux the alternators output voltage would increase to around 14.4V@22C, you then certainly wouldn't need the smart pass for in car charging a simple VSR would do as good job. For a camper you may get some advantage still using the smart pass but it would depend on how deeply you discharge your batteries. If you only go down to 80% SOC at most then the DCDC part would be of benefit but you wouldn't need the VSR part ie just use a 250. If you deeply discharge your batteries then the VSR part only would give you very good performance with not much loss of performance.

These types of devices only really come into their own when a suitable charge voltage is not obtainable.

Gets back to how much you want to spend and how you use your setup.

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Follow Up By: gbc - Sunday, Jun 01, 2014 at 20:51

Sunday, Jun 01, 2014 at 20:51
Just to be clear, in his original post he stated he was also installing a solar panel, and yes, in that case the ctek will charge back to the start battery as well if the spare charge is available.
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Follow Up By: HKB Electronics - Sunday, Jun 01, 2014 at 21:15

Sunday, Jun 01, 2014 at 21:15
Happy to stand corrected but for this to happen:

The solar is connected to the input of the 250, the 250 output to the aux, the only way it can get back to the cranking battery is via the VSR part which is not active when the DCDC charger is, if it was you would have the output of the DCDC charger connected to its own input via the VSR part as they are both wired in parallel?

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Follow Up By: Member - lyndon NT - Sunday, Jun 01, 2014 at 21:37

Sunday, Jun 01, 2014 at 21:37
I think gbc is referring to when car is switched off and solar is being supplied?

What sized cable would you be running in my case Leigh?
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Follow Up By: HKB Electronics - Sunday, Jun 01, 2014 at 22:30

Sunday, Jun 01, 2014 at 22:30
I'm fairly sure the same applies with or without motor running, just wouldn't make sense, the whole arrangement is to charge the aux as quickly as possible hence the VSR part, then the charger. If running of solar why would would you send the charge back to the starting battery and slow the aux charging?

There maybe a manual over ride to allow cranking battery charging as well as the aux but if there is I haven't seen it?

Cable, if you want to get the best out of the VSR part then the heaviest you if is cost effective, I wouldn't use any smaller than 13.2mm2, myself 20mm2 bigger the better but cost goes up.

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Follow Up By: gbc - Monday, Jun 02, 2014 at 08:45

Monday, Jun 02, 2014 at 08:45
Yes, if the second (house) battery reaches full charge, the 250 will then start working on the start battery using the available solar power. The term VSR isn't quite correct either - there aren't any relays - apparently?
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Follow Up By: HKB Electronics - Monday, Jun 02, 2014 at 12:48

Monday, Jun 02, 2014 at 12:48
Thanks gbc,

I stand corrected:) that is a good feature, I'm surprised they don't make a mention of it on the cover page.

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Reply By: Robin Miller - Sunday, Jun 01, 2014 at 20:10

Sunday, Jun 01, 2014 at 20:10
Well you have asked a few questions there Lyndon and I'm not sure I can see the whole picture.

Funnally (who has the right spelling) enough only 2 hours ago I got a call from a stranded vehicle
which had winched its twin aux batteries flat and the car won't go.
The batteries get manually switched into the main and when they thru the switch the surge of current
took out the big main fuse (120amp) with such force that all its left was two melted prongs.
Really not in the mood to do a cold rescue this evening so I told them to wrap some speaker cable around the posts
and haven't heard anything yet.
Next time they might listen and not use 32mm oversized cable.



On your issue, it comes down to a few things that need to be done properly
the first being to know more about auto elec's volts measurement.
13.2 volts charging doesn't sound right unless its all hot and alternator
temp sensor is in shutdown or batt is flat or some other big load is on.
(Also volts is revs dependant - has it stabilized)

One thing I suggest to everyone who has no permanent voltmeter installed is to get those little
Ebay / Jaycar cigarette lighter plug in digital voltmeters and leave it in all the time and get to know
how your car behaves. (Mine $3.98 Ebay)
Mine always starts off cold at just over 14 volts cruising dropping to 13.2 only when all hot.

Cable 13.5mm is better , but 8mm is ok if its really 10amps load as resistance of wire is approx 0.002 per meter
or volts drop 0.02 for 10 amps (1/50th of volt/m).

A total volts drop of 0.5v is acceptable at you maximum real load and this would be 15m of total cable + fuses.

But some important points
1/ ensure the cable is copper - not plated.
2/ Be sure max load really is only 10amps.
3/ The voltage drop needs to be measured right.
As it happens I just fitted a bigger inverter in back of my car to run bigger
heat lamp which takes over 25amp (well its getting cold, winter started today)

At battery I had 12.2 volt and at other end I had 11.1 volt which at first seems a lot
for 5 meter of 8mm cable (no return cable required as Nissan uses body earth at this point).
So I then measured the real volts drop in the cable positive lead only and as expected the real drop was about 0.3v.
The rest comes from internal resistance of 12v battery and fuse.

Unfortunately, for me the inverter protests a little so I will be upping my cable size,
but on the +ve side Ebat was flogging 20mm sq cable at $1 a meter which sounds like a dream until I read that postage was $2 a meter , still $3 a meter is dirt cheap.

P.S. Check your and your Auto elecs meters for accuracy - if can't then get both to measure something at same time and at least know they read the same.
My doctor hates me because because he once told me my weight hadn't changed in years and I told him his scales were out , cutting this short he had never had them calibrated and a cross reference with mine showed a 4kg error - he still dam well gave me a bill.



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Follow Up By: Member - lyndon NT - Sunday, Jun 01, 2014 at 21:31

Sunday, Jun 01, 2014 at 21:31
Hi Robin

Thanks for the reply. Just to clarify, are you saying I will have to add all 3 lengths of cable Vd together? I wasn't sure if this was so, thought I would calculate Vd from alternator to batteries as separate and then add the Vd from batteries to fuse box and fuse box to socket outlet together? I know if it was AC I would add all together but not sure how it works having the battery in the middle?

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Follow Up By: Robin Miller - Monday, Jun 02, 2014 at 10:07

Monday, Jun 02, 2014 at 10:07
I am still not totally clear Lyndon so I hesitate to answer but am happy to work thru any defined senario.

As far as charging goes all thats important is the total volts drop from any source (alternator solar or charger to the actual battery terminals ), when things are normal I.E. not when battery is flat .

As far as discharging into a load is concerned its voltage drop from closest battery source to the actual device which should be below 0.5 V when system really is drawing its max load.

What is wrong to do is to measure a voltage at load with device off then switch it on and measure voltage at load again and subtract to get the difference.

If you have just 1 meter and wish to do a quick measurement you first switch on the device(s) , measure volts at device terminals then go to battery nearest device and measure volts at actual battery terminals with device(s) still on.

Most important is to do above with engine off but its good to do this with all senarios e.g. alternator charging as well as engine off , but not with multiple active volts sources.

By this I mean that a charging solar panel connected closer to your load may raise the volts reading and give you a false impression.








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Reply By: Member - lyndon NT - Monday, Jun 02, 2014 at 07:47

Monday, Jun 02, 2014 at 07:47
OOp's, one more thing. Is it unreasonable to think the Hiliux alternator can deliver 80 A to these batteries when they are heavily discharged?
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Reply By: Member - John and Val - Monday, Jun 02, 2014 at 14:13

Monday, Jun 02, 2014 at 14:13
Lyndon,

Thank you for your member message.

There are quite a few loose ends that I don’t understand. Like why your mate would want so much battery capacity in the back of his rig….. or is he pulling a caravan or camper and if so why aren’t his batteries in that trailer…. Why the urge for such high current charging ....

Assuming the loads being fed by the batteries are in the back of the Highlux, why are you running leads back to fuses under the bonnet? If I was setting this up I’d simply use two 30A fuses, one for each of the two batteries, installed very close to its battery. The other side of the fuses would be connected together to be the feed point to/from the charger and loads. In this way the whole system is protected from the batteries and either or both batteries can be easily connected/disconnected as required by just pulling a fuse. Certainly I would NOT run an unfused wire from those batteries to the front of the vehicle. The whole point of fuses is to protect your system (and the vehicle!) from the energy stored in the batteries should something go seriously wrong. There is no need for any other fuses, unless you find them a convenient way of disconnecting parts of your rig.

Don’t understand either why you would use a Smartpass. I’ve tried to dig the brochure and installation instructions out of their very thick covering of bull….. Both make so many unbelievable claims that it’s impossible to decide how the Smartpass might function. My best guess is that it is a solid state equivalent of VSR, but with both voltage and current sensing, and can be used to bypass the dc-dc charger while the house batteries are accepting from the alternator more current than the maximum that the dc-dc charger can deliver. Once the current drops into the charger's range it seems the Smartpass removes the bypass and allows the charger to get on with the job. Maybe. There are too many implausible claims to be at all sure what the thing actually does. If it was my job I would use a conventional VSR to feed the D250S, or possibly go to a bigger charger such as the one from ABR Sidewinder.

Something worth being aware of is that the current flowing to the batteries from the alternator is NOT increased by the Smartpass. In a direct connection, the current would be determined by the alternator voltage, losses in wiring, and battery’s own capacity to accept charge. The Smartpass does NOT increase this current. The spec sheet says it can deliver up to 80 amps (or 100 amps if you read far enough), but does not say that it WILL do it! The constraints imposed by the alternator, wiring and battery still remain limiting factors that can't be changed by the Smartpass. The advantage of a dc-dc charger such as the D250S lies in it overcoming those constraints to some extent. In my experience it is very seldom that my 30A dc-dc charger actually delivers its full 30A for more than a minute or so – my 200 Ah of batteries very quickly decide what they’ll accept, and they, not the charger, determine the charge rate.

Re your question about whether the Hilux alternator can deliver 80A – Almost certainly not, but most certainly not for any useful length of time. A quick look under the bonnet could answer your question – any alternator expecting to deliver 80 amps will be fitted with a dual gang pulley and drive belts. (Why would you want to charge at 80A? The batteries won’t thank you! – I think perhaps you’ve been led astray by the Ctek documentation. )

I’d endorse the above comments from HDK and Robin.

Cheers

John

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Follow Up By: olcoolone - Monday, Jun 02, 2014 at 18:31

Monday, Jun 02, 2014 at 18:31
The Hilux has a poly ribbed belt that can transfer more horsepower then 2 A section belts (more surface area).

The Hilux will deliver 80 amps but as you have said for how long..... people have this misconception (including some experts on this forum) an alternator fitted to most passenger based vehicles can deliver the rated current until the cows come home, if they had good cooling and access to cool air then yes but like most things under bonnets; not every thing lives in an ideal world.

Have a look at a 100 amp alternator on a truck compared to a 100 amp alternator on a car..... there is a very good reason why truck ones are a lot bigger and it' not to fill the engine bay..... I think it has something to do with heat dispensation.
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Follow Up By: Member - John and Val - Monday, Jun 02, 2014 at 19:01

Monday, Jun 02, 2014 at 19:01
Thanks Olcoolone - good point about the drive belt. Fact remains though, it's a big ask for any small alternator to deliver its rated output for an extended period of time.

Cheers

John
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Follow Up By: gbc - Tuesday, Jun 03, 2014 at 06:00

Tuesday, Jun 03, 2014 at 06:00
In layman terms the smartpass can connect various sources of input power at the same time - alternator, panels, wind generator all at once to flow the maximum amps into a battery bank that the batteries will accept.
The smart pass will remove the load from the batteries whilst charging so the batteries are being charged in a no load state all the time which speeds up the whole process. The smart pass also acts as a vsr (but only if you wish) and will disconnect non essential load from the battery bank once it drops below 11.8v.
If you leave solar panels connected or a battery charger on the bank, the smart pass will reconnect the start battery and condition it with the available spare power.
Hope this helps. On most forums I read it isn't the owners of ctec products who don't like them, you never hear from us because we are happy campers ;)
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