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

I've just been pulled up on some spelling, that would be alternator and Tub floor :-)

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.

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.

Cheers
Leigh

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.

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?

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