Smart charging alternators.

Looking at the data sheets these intelligent battery monitoring sensors all comprise of a small resistor (around 0.0001 ohms) in series with the chassis lead.
The volt drop is monitored with a ton of processing (some have an ARM Cortex processor...complete overkill IMHO) and the data is sent over LIN bus etc.
It's just another chance to make a killing when they pack up...they're well under a tenner to manufacture but £100 to replace.
A careful right foot will save 100 times more fuel....

I could well be wrong, but it looks like unplugging my vehicle's sensor causes the system to fall back onto a default safe operation of the alternator.
After all, if removal was too dodgy surely 'limp mode' at least would be instigated... Just get the idle stop inhibited information and of course no drop in alternator volts when climbing a hill on the throttle and no 15 + volts on over run - smart charging my arse ! Just runs your battery down over time.

I need to check the amps output - am guessing the alternator will cover the electrical load as per everyday alternators, no large amp output all time.

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Here we go. new battery fitted some weeks ago.
Same situation - smart sensor - supposedly helping to do the biz, not happy with this smart alternator stuff, so unplugged the cable to the negative post smart sensor.
Now I have 14.3 or so Volts all the time (measured via an accessory socket).
Question in mind was - Is the amp output from the alternator ok or silly large or small ?

Now I drive somewhere with the stable non varying Voltage output - after 25 miles with air con (climate control) on etc, now stationary, engine remains running all switchable loads turned off.
Engine at tickover 800 rpm. ambient temperature 31° C.
Amps measured at the negative (ground) lead +2.73 A. Switch to dipped heads +2.72 A. Switch to main beam +2.72 A. all at 14.4 Volts.
Engine off. Key off.
Amps at ground lead -1.5 A. Dipped heads -11.7 A. Main beams -19.73 A. Voltage dropped then stabilised at 12.37 V. under load.
All loads off and after several minutes 12.63V across battery terminals, Current -0.25 A (alarm etc - I guess)
The sign (+/-) was useful as I am using a digital meter with built in 'Amp Clamps', I needed to know if clamp is orientated correctly, the engine off with battery loads applied sorted that question giving a -ve answer, which makes sense.

The downside thus far ?
Switch ignition on, a warning appears at the I-Multi-Information (IMI) display an Orange Letter 'A' with a circular arrow around it. = 'Auto Idle Stop System error' - Hooray! Stop/Start is unavailable. This message can be cycled from the IMI screen. Engine starts as it should, just a small orange indicator is 'on' within the rev counter display - probably to indicate there is a situation at the IMI display, which actually also has a little 'flag' attached.
Everything else works ok

Following the same journey with the smarts connected, and no loads applied, engine and key off was leaving me with just 12.3 Volts across the battery.
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It appears to me that with the smart sensor lead attached and dipped headlights on, the system went to 14.4 Volts and remained there with no changes during overrun / braking, I assume the amperage output to battery/load was adequate, Idle stop (stop/start) was available all times and no problem with the old climate control either.
I think I will continue with the smart sensor unplugged - At least I'll not be generating a minimum of 11.7 Amps (dips on). Just to feel that the bloody thing is charging !
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Fuel consumption computer says 58.5 mpg, I know over many fuel brimmings and distances recorded the computer is optomistic by at least 8%
so I am really getting 54.1 mpg ( pre the battery shenanigans I was getting a regular 55 mpg.)

So there we go, Honda SR 1.6 i-dtec.

Hats off to 'Rob bob' or 'UKbob' - right on !!

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The current will be proportional to voltage so you wont "over amp" the battery.

The SMART alternator control estimates battery temp, but I think that is only because it tries to shove far too much in on overrun and this prevents it cooking the battery.

Keithmac said:

The current will be proportional to voltage so you wont "over amp" the battery.

The SMART alternator control estimates battery temp, but I think that is only because it tries to shove far too much in on overrun and this prevents it cooking the battery.

Click to expand...

Yes, this, I always thought - but I get 14.4 'ish Volts unvarying, all the time. When I did your 'trick' with lights on but with smart sensor connected, I also had constant 14.4 Volts, I am not towing so cannot really justify lights on all time.
I was concerned about Amps, don't have means to check whilst driving, that's why I did the check under bonnet after 25 mile run engine at tick over, mentioned ambient temperature to show the electrics would have been working - we ran climate control set to 20°C,
I guess I would be reading the net Amps at the ground (Neg) wire... So was getting 2 or 3 +ve Amps with varying loads applied, motor running.
After engine off, I read the actual load Amp draw as -ve with the Amp clamp.

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I remember many years ago looking at split charging, in my case it was a 16 ton truck with 10 ton trailer both made into mobile libraries, we tried relays and blocking diodes, but when we connected an ammeter yes on start up 20 amp or more to trailer battery, however within minutes it dropped to 1 amp or less, it simply never worked as trailer not towed for long enough.

To back energy into a lead acid battery fast either pulse or stage charging is required. I tried to resist charging the car with smart charging, however I had to use a small mains smart charger in the end, the battery was clearly going too low.

However I think I have around 10 lead acid batteries and 2 smart chargers, so they are in near constant use, one or other battery always needs charging, and the main problem is how to know when fully charged. On a small (under 12 Ah) battery the charger will in fullness of time turn off, but nothing on charger to say turned off, only the energy meter tells me when complete, with larger batteries it never seems to turn off, 0.1 amp is not very much, but not off, and 60 Ah and over the batteries seem to sit at 12.9 volt, I am sure really it every so often jumps to 14.4 and then drops again, but I don't see that.

So I monitor power into charger, but although volts shown, I have to do down to basement flat to read that, so the question is at what point to swap battery charger to next battery.

However returning to cars smart charging, again down to time, if car is used for 50 miles a week so 1.5 hours charging likely no problem, where the problem arises is when used for 5 miles a week. And although allowed 5 miles local travel, we don't go out every day, and it is shared between three cars, so hard to even get 5 miles a week. So from cold start it has to replenish that in around 10 minutes, that simply will not happen.

ericmark said:

So from cold start it has to replenish that in around 10 minutes, that simply will not happen.

Click to expand...

It should replenish what the starting took out of it in (less than) 10 minutes.

Whether it will replenish the accumulated drain of the unused days is another matter.

To maintain the stop/start function with a battery less than a year old I have needed to use a 230 volt charger twice during the lock down, I will admit I have also charged the other two cars, an only Honda Jazz and a Kia Sorento but these are old cars the Jazz still with original battery where the Jaguar XE has a battery around a year old, and a battery costing over £200 as it is absorbed glass mat or valve regulated lead acid.

As to drain on battery while idle I have never measured, but even a battery not fitted to a car looses energy over time, however when I collected the old Jaguar XE battery which we now use for the caravan from my old house and put on charge the charger turned down to 0.1 amp charge rated within 12 hours, and from 3.8 amp to 3 amp within ½ hour, and 3 amp to 0.8 amp in around 4 hours, so it seems over 9 months it was left standing it had lost around 15 Ah, remember this battery was before being used with caravan had failed to start car so was replaced, I had expected this old VRLA to be useless after being left for so long without charge, but no, it had held the charge well.

Clearly this is why cars with stop/start use AGM batteries, they are very good, however fact that low battery warning light lit, shows that the car was unable to replenish what had been taken out of it, unlike the Jazz which has only had short trips, we had 60 mile round trip for hospital visit, and 40 mile round trip for shopping, we could not get a click and collect in Wales, to had to travel to England, same with hospital.

I have not monitored the cars charging but I have monitored the 230 volt smart charger, and it seems very fast the charge rate drops, it has a max of 3.8 amp which is a very low charge rate really, but rare does it hold this rate for more than ½ hour, OK the battery just removed from caravan was 3 hours at 3.8 amp, but it was less than 3.8 volt and showed Err when connected to charger, so had to leave over night in parallel with a 7 Ah to get enough in it for the charge to start charging it. I expect it to take around 3 days to recharge, the charger could put more into the battery, but battery will not accept it.

I don't think disabling the Smart charging would make an ounce of difference, turn off the mains charger than turn it on again and it returns to Max output, so average charge stays the same, and I think one would find the cars built in charger is the same, and I know the Jaguar XE inhibits the stop/start and heated seats if it detects the battery is low, so the problem is not really the Smart charging it is as name implies quite Smart and it turns off the stop/start etc when battery is low. The problem is using the car so little on average. We have around a 500 mile range, and not filled up since March, we have averaged around 15 miles a week, it is simply not enough time with engine running.

How do you measure a loss of 15Ah in an unused battery?

I suppose it must be possible otherwise how would they know what it was to start with.

I don't reckon my car's 'smart charging' system works the same as my CTek smart charger.
The Ctek Volts applied get lower as the charge state increases.
My car in the smart charging mode, only ups the Volts applied when on the over run not seen more than 15.5 V. Can only guess a big dollop of Amps goes with. With headlights on dip or main - I get constant 14.4 Volts no varying, over run or what ever. Essentially the same Voltage as with the battery smart sensor unplugged.
Have an iron partially in the fire with regard to a non-invasive Amp meter, effectively a remote clamp meter device.
This would satisfy my interest in the Amp situation during a journey.
Currently we can do a few journeys per week and be relatively assured of a fully charged battery minus Auto idle/stop and the varying 'smart charge' rate... That's a huge loss - NOT.
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EFLImpudence said:

How do you measure a loss of 15Ah in an unused battery?

I suppose it must be possible otherwise how would they know what it was to start with.

Click to expand...

Our Kuga monitors the battery when the car has gone to sleep (overnight), it uses this to gauge battery condition and State Of Charge.

It also has the battery age in the BMS to estimate condition (that's why the BMS should be reset when a new battery is fitted).

empip said:

Yes, this, I always thought - but I get 14.4 'ish Volts unvarying, all the time. When I did your 'trick' with lights on but with smart sensor connected, I also had constant 14.4 Volts, I am not towing so cannot really justify lights on all time.
I was concerned about Amps, don't have means to check whilst driving, that's why I did the check under bonnet after 25 mile run engine at tick over, mentioned ambient temperature to show the electrics would have been working - we ran climate control set to 20°C,
I guess I would be reading the net Amps at the ground (Neg) wire... So was getting 2 or 3 +ve Amps with varying loads applied, motor running.
After engine off, I read the actual load Amp draw as -ve with the Amp clamp.

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Click to expand...

All the motorcycles I work on run 14v to 14.5v battery voltage (use 3 phase alternator and Regulator/Rectifier).

Your battery could only be drawing 1 amp to maintain 14.4v, the alternator will also be supplying all the electronic gubbins in the car. Only an Amp Clamp on the battery wire (near the alternator) will show you what it's actually supplying current wise).

I would be happy at a constant 14.4v and wouldn't worry about it personally.

I can barely get at the positive lead to battery otherwise I would be on it, since when did they use tape on the cables ?
I am pretty certain of a good charge now, given the +ve 2-3 Amp readings at tickover under different loads at the ground cable.
The -ve readings KOEO (key off engine off) after allowing system to settle somewhat.
And the final 12.6 Volt reading across the battery (possibly the testing above, koeo applying various loads, burnt off most of the surface charge).

Yes I am happy, pretty much sure that the battery is getting kept to the mark without the alternator smart charging, saving me 1 or 2 mpg and having idle stop available which I prefer not to use.

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In the following vid' (mildly interesting) I find the first mention of 'amp clamping' negative and positive battery cables - engine running - and the differing readings which pretty much match my own un-knowledgeable reasoning - ie. negative lead +ve reading is net amps (for charging battery) after other loads are satisfied, be nice to know if this is provably a fallacy or not.
Honda is pretty stingy with cabling to battery, ground lead is just about ok - positive tight on battery and taped very securely hence my fixation with the ground cable.
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I thought it was very interesting.

Not quite sure what you are asking, though.

It is, in effect, just measuring the current through various wires
Whilst there might be 50A in the alternator main lead, there will only be the current drawn by each accessory on the individual accessory wires.