smart alternator override

[Poita]

I dunno mate but the way my chargers work 240 volt or DCtoDC is they supply amps which push up the battery voltage, by reducing amps they stop batteries overcharging & drop the amperage right of to the float voltage value of the storage battery being charged.

A 120 amp alternator certainly isn't producing 120 amps when your battery is full & 14.2 volts to my knowledge.
I'm probably wrong but if the alternator was runnig "full blast" i'm sure your battery would be A molten mess, if your alternator wasnt fried first?

Dumb alternators draw engine power & fuel but, smart alternators when not charging use less juice also I think?

Kinda on the right track but not quite...
First thing is that you can force current into a load, the load draws current based on its resistance and the supply volts. A=V/R

Batteries are a resistive load to the alternator in very simple terms . Think of them as the emptier they are, the lower the resistance. Using ohms law (A=V/R) and assuming the volts is a constant from the alternator, the battery will try to draw as much current as it can from wherever it can, be that an alernator or another battery that has a higher state of charge that's connected to it. As it charges, it's internal resistance goes up and it draws less current until it is full.

Overcharging is a result of too higher voltage (faulty alternator regulator generally) nothing to do with current.

The issue is that the battery can potentially draw to much current if its resistance is too low. So a lot of charges start off by limiting the amount of current it can draw (to say 20A) initially by keeping the voltage low (constant current stage), and then revert to a higher voltage (constant voltage stage) at the end to finalise the charging cycle.

[pharb]

[QUOTE=Mike DiD;620231]

Mike , Do you mean that the negative from the Aux battery has to be connected below the currrent sensor ?

NO! The Aux Battery is connected in the Alternator/SEnsor circuit EXACTLY the same way as the starter battery.

Connect the Positive of the Aux Battery to the Positive post of the Starter Battery.
Connect the Negative of the Aux Battery to the Negative post of the Starter Battery.

If any of the loads connected to the Aux Battery are also grounded to the Body (e.g. Lights which only have a single positive wire and get the negative return via the light body), you will be BYPASSING the current sensor.

Are you sure?

On my NX the sensor is mounted on the earth lead between the starter battery negative battery post and the body, so if I was connect a load (such as the auxilary battery, or winch for example) to the starter battery directly via the negative and positive posts the sensor won't see the current flow to/from the auxilary electrical load.

[Jasonmc73]

Kinda on the right track but not quite...
First thing is that you can force current into a load, the load draws current based on its resistance and the supply volts. A=V/R

Batteries are a resistive load to the alternator in very simple terms . Think of them as the emptier they are, the lower the resistance. Using ohms law (A=V/R) and assuming the volts is a constant from the alternator, the battery will try to draw as much current as it can from wherever it can, be that an alernator or another battery that has a higher state of charge that's connected to it. As it charges, it's internal resistance goes up and it draws less current until it is full.

Overcharging is a result of too higher voltage (faulty alternator regulator generally) nothing to do with current.

The issue is that the battery can potentially draw to much current if its resistance is too low. So a lot of charges start off by limiting the amount of current it can draw (to say 20A) initially by keeping the voltage low (constant current stage), and then revert to a higher voltage (constant voltage stage) at the end to finalise the charging cycle.

I appreciate the eductaion albeit A little over my head .
Does that mean A charger can send say 50amp or whatever as long as voltage remains below batteries threshold? Lets say 14.2 volts?
Or is that too simplistic & regulated Volts is what matters to the life of the battery? Is ther any relationship between the amperage & the Volts showing say on the battery?

[Mike DiD]

[QUOTE=pharb;620296]

Are you sure?

On my NX the sensor is mounted on the earth lead between the starter battery negative battery post and the body, so if I was connect a load (such as the auxilary battery, or winch for example) to the starter battery directly via the negative and positive posts the sensor won't see the current flow to/from the auxilary electrical load.

YES, it's mounted on the Earth Lead of the battery so t measures the current flowing through the battery, and ignores any current drawn by any loads in the car.

So explain how you think the current can flow through the Aux Battery or Aux Loads WITHOUT flowing through the sensor.

[Poita]

[QUOTE=Mike DiD;620337]

YES, it's mounted on the Earth Lead of the battery so t measures the current flowing through the battery, and ignores any current drawn by any loads in the car.

So explain how you think the current can flow through the Aux Battery or Aux Loads WITHOUT flowing through the sensor.

The sensor measures the current flowing from the body, through the sensor, to the main battery.
Any load connected directly to the main batteries negative terminal will not be measured as it is not flowing through the sensor.

To accurately measure all loads in a dual battery system, the aux battery negative terminal must be connected directly to the main batteries negative terminal and all load negative leads connected to the vehicles body.

[Poita]

I appreciate the eductaion albeit A little over my head .
Does that mean A charger can send say 50amp or whatever as long as voltage remains below batteries threshold? Lets say 14.2 volts?
Or is that too simplistic & regulated Volts is what matters to the life of the battery? Is ther any relationship between the amperage & the Volts showing say on the battery?

Any good charger will have a current limit, typically around 20A which is what most battery manufactures recommend to not damage the battery.
Regulated volts is important to a batteries lifespan, as is the number of charge / discharge cycles.

[Jasonmc73]

Any good charger will have a current limit, typically around 20A which is what most battery manufactures recommend to not damage the battery.
Regulated volts is important to a batteries lifespan, as is the number of charge / discharge cycles.

Yes I Have 240Volt fed CTek 15amp charger around home & Redarc 1240D DC-DC charger feeding 2 x 120amp AGM's in trailer.

I was more trying to understand if the current dropped off in relation to how much energy was stored in the batteries & if the regulated voltage had any relationship to the amps?

I always thought current dropped as volts increased during the charging process & when desired Voltage was reached amps dropped off?

Sounds like I've been wrong all these years . Not that is matters so much, as you say use correct amount of amperage input in relationship to size of storage battery & let charger do the rest!

[drgtr]

Well thanks to you intelligent blokes

Now I know when hooking up my dual battery

Negative of auxillary battery to negative of main battery


and all auxilary or any new equipment. Earth to body and not either of the negative terminals!

[Shauns]

Hi.
I have posted before, no one has been able to give a suitable response.
does anyone know a way to to trick the alternator / ecu to increase output / voltage.
is there a wire to cut and a resistor or diode that can be installed like Toyota.

Thanks

shaun

[Two Emms]

WhenI installed my ultragauge, one of the things I watched was voltage. It varied from 12.4 to 14.3. This is the smart alternator working exactly as Mitsubishi intended.

I have now enabled a work around which sees voltage never below 13.8 and 90% of the time is at 14.2 or 14.3. Been using this method for months and the results are consistent. To my (simple) mind this will keep my battery nicely charged.

The method I use has been mentioned a lot on the forum. Just leave the cabin fan turned on all the time. Easy. The aircon doesn't need to be turned on and the fan can be on low, so it's barely noticeable. So no cutting wires or modification to factory systems.

Try this. It's quick, easy, free and reversible.

[Neville Sneath]

Hi
When charging batteries paralleled they have to be the same type. Starter, Deep cycle, AGM, and lithium all have different internal resistance and require different charging voltage. Buy using DC to DC chargers the auxiliary batteries are charged at the correct voltage.
the input to the Dc to Dc can be between 9V to 15V and give out say 14.6V this is handy if the auxiliary is in the back of the vehicle or in a van where you will get a voltage drop. I know Redac and Ctek are expensive there are some cheap Dc to Dc chargers about, I have a Redac powering the aux under the bonnet, plus caravan battery, the redarc has been in my14 NW 6yrs 160,000ks, with the van in tow for 75,000Ks, it was powering 2 ACDelco for 4yrs and now 2 SSB Ultra High Performance AGM’s (which can be fitted in Engine bay). These last 2 batteries cost me $576 ea , at a local shop they were $758 ea.
Hence My $1500 worth of Batteries are been looked after by a DC to DC charger.

[Dicko1]

Hi.
I have posted before, no one has been able to give a suitable response.
does anyone know a way to to trick the alternator / ecu to increase output / voltage.
is there a wire to cut and a resistor or diode that can be installed like Toyota.

Thanks

shaun

Just do as 2 emms suggested. Simple and you wont notice it. Living in FNQ my fan is on nearly 100% of the time. However I still have a dcdc installed for my lithium aux battery.

[nj swb]

Hi
When charging batteries paralleled they have to be the same type. Starter, Deep cycle, AGM, and lithium all have different internal resistance and require different charging voltage. Buy using DC to DC chargers the auxiliary batteries are charged at the correct voltage.

Sorry, but this is one of these internet myths that just refuses to go away.

Yes, Lithium is different, and can't be charged in a simple parallel install with a lead acid battery. All these "drop in replacement' lithium systems have a built-in battery management system to take alternator voltage and treat the lithium cells properly. Yes, I know there are people who have strung together lithium cells without a battery management system, and had no problems. Others have done this, and started fires. But I digress...

Starter, deep cycle and AGM are all lead acid batteries, and can be charged simply in parallel. Redarc's different charging profiles, which use different voltages, used to be for different constructions . Now, their instructions list the different charging voltages, and tell the owner to consult the battery manufacturer's documentation - because it isn't as simple as different constructions. The table also distinguishes between under-bonnet and elsewhere, as ambient temperature also enters the equation.

Essentially, higher voltages lead to higher charging currents, which will generate more heat - it is the maximum charging current that is the problem, not the charging voltage, and putting the wrong battery on the wrong DC-DC charger will still be bad - many sub 100Ah AGMs shouldn't be charged above 25A, so putting them on a 40A DC-DC would still be bad, regardless of the charging profile selected.

Yes, different constructions can have different internal resistances, but it isn't as simple as starter vs deep cycle vs AGM (and SLA/VRLA should be in the list too). Some AGMs can have very low resistances and handle high charging currents with no problems, others will not. Likewise, some wet cell deep cycles can be charged precisely the same as a traditional starter - and others should be charged at a lower rate.

Yes, a properly selected DC-DC makes it much easier to look after an auxiliary battery - I have one myself - but with proper knowledge and appropriate battery selection, it's perfectly acceptable to mix & match wet cell, gel cells, AGMs, SLAs, VRLAs - they don't "have to be the same type." You can even hook up a calcium battery in parallel with a standard lead acid, if the system is designed to charge traditional lead acid chemistry. If the system is designed to charge a calcium, it is likely to over-heat a traditional lead acid.

[Dicko1]

When you charge 2 dissimilar batteries in parallel, the charger shuts off as soon as the capacity of the smallest battery is reached. So if you have a 75 amp hr and a 100 amp hr battery in parallel, both batteries will get no more than 75 amp hr. That's why they tell you to use the same brand, size, and age batteries.

The other issue is the lower internal impedance of the AGM battery. It will always charge first.

As long as the batteries are isolated you should be fine. Without an isolator, you will be losing capacity. As as the batteries age and lose capacity, you will only be able to charge to the level of the weakest battery.


The above info is wrong. I lifted this from another forum site and it just shows that there is a lot of mis information out there. It really pays to do your home work as even a professional can make errors...let alone us amateurs!!!

[nj swb]

When you charge 2 dissimilar batteries in parallel, the charger shuts off as soon as the capacity of the smallest battery is reached. So if you have a 75 amp hr and a 100 amp hr battery in parallel, both batteries will get no more than 75 amp hr. That's why they tell you to use the same brand, size, and age batteries.

Sorry Dicko, but this is simply wrong. I believe you're thinking of charging lead acid batteries in series, not parallel. I expect the systems you maintained during your career were banks of batteries in series, to create higher voltages - probably 48V battery banks, floating at about 55V, possibly boosting higher. If this thread was talking series charging, I would agree. For parallel charging this is simply wrong.

Lead acid batteries are incredibly simple to charge - they take the charge current that they want, based on available voltage, state of charge, and temperature. When charged in parallel, with a constant voltage float charger with the correct voltage, each battery will take care of itself - as the state of charge increases the battery draws less current. The battery is controlling this behaviour, not the charger. But this isn't the fastest way to charge them.

If you want to add a multi-stage charger into the equation, which changes its output voltage based on charging current, then things change, but not as you have stated.

A multi-stage charger uses a higher voltage in its bulk charging phase, while the battery is in a lower state of charge, which results in a higher charge current and faster charge. As the state of charge rises, the charger senses the change in terminal voltage, and will then hold the voltage at a set level for the "absorption" phase. During this phase, the charger monitors the current, which will ramp down as the battery continues to increase its state of charge. During this phase, it is not the charger that is reducing the current, but the battery controlling how much current it will take - based on applied voltage, and battery temperature. Once current drops below whatever point set by the charger designer, the battery voltage will drop to its float charging voltage, and the battery will continue to draw whatever current it wants.

With two batteries in parallel at different states of charge, different things will happen.

In the bulk charging phase, the battery with the higher state of charge will reach the "switching threshold" sooner, causing the charger to detect this threshold voltage, and switch to absorption mode.

In absorption mode, the battery with the higher state of charge will continue to charge quickly, but the charger is now monitoring current draw. The battery with the lower state of charge will continue to draw current as it continues to charge, but the battery that started with a higher charge will begin to overcharge - overheat, off gas, suffer.

Only once the battery with the lower charge drops its charge current below whatever threshold will the charger change to its float mode, and slowly bring the battery to 100% - but by then, the other battery has been overcharged.