charging rate

[LeighW Avid PP Poster! Find all posts View Profile Close LeighW]

Re: charging rate

Hi drivesafe,

Again do agree with you, I though as many others have found that whilst touring ie
spending a couple of nights here and there then moving on for the day spend the night
another day here, two nights there, the charge rate just isn't acceptable. It just far to
long to charge the batteries now. Pre D4D this wasn't an issue touring.

Most have now found that you need to use solar panels to ensure the batteries are
kept charged, if the weather turns bad the batteries the flatten fridge turns off
goodbye meat etc.

The theory may be great, but in reality it just isn't working if it was we wouldn't
be having this debate!

Cheers
LeighW

[LeighW Avid PP Poster! Find all posts View Profile Close LeighW]

Re: charging rate

I should have added also that the voltages above are with all accessories
off.

This seldom the case whilst touring, you could have aircon on, computers,
sat navs, multiple radios, be doing reapted stop starts, idling waiting for
others etc.

Cheers
LeighW

[drivesafe Senior Member Find all posts View Profile Close drivesafe]

Re: charging rate

This seldom the case whilst touring, you could have aircon on, computers,
sat navs, multiple radios, be doing reapted stop starts, idling waiting for
others etc.

And hence the reason behind fitting larger and larger alternators, and not just to 4X4s.

It’s not to give more power while driving along, the maximum power most vehicles require to meet the needs of the standard electrics is no more than 40 to 50 amps, maximum.

The problem is that while a 55 amp alternator can easily meet the electrical needs of the average vehicle while the vehicle is cruising along, as soon as the motors revs drop, so does the amp output of the alternator.

Two solutions are used to get around the problem of city driving’s low revs. The first is to modify the alternators pulley ratio and the second is fitting alternators with much higher total capacities.

End result is a much higher current output at idle.

I’ve measured 47 amps being pulled from a Discovery 3s alternator at idle and I suspect Toyota vehicles with the larger alternators would be capable of similar current supplies.

The designed output unfortunately is not meant to supply any more than the vehicles standard requirements. Add a battery or two and your back to insufficient current supply in city traffic conditions.

This is still not all that much of a problem because most of the time for us, the batteries are either in a fully charged state as we head off through the traffic for the start of our weekend away or that long trip, or we are on our way back home before we hit the traffic.

In most cases, while away, we will be travelling at speeds that will allow the alternator to turn out all the power we need.

[LeighW Avid PP Poster! Find all posts View Profile Close LeighW]

Re: charging rate

Hi drivesafe,

In the D4D very little extra load is required to drop the voltage, ie turn on the aircon,
with the condensor fan off the compressor off and the evap fan on it is enough to drop
the battery voltage by around .2V The evaporator would only be drawing around 3A
if that.

I not a hundred percent sure as Toyota changed the capacity of the Alternator
but it is probably 90A - 100A.

The regulation is a bit odd acutally, it only takes a small accessory load to impact the output
but once it drops it then becomes fairly stable. Wih regards RPM car idles about 600 from
memory lifting it to 1500 (highway speeds) brings alt to max no problems, higher than that
it drops a tad due to higher ripple frequency I assume

Alternator output is not an issue as once you lift the voltage a little all is well.

Again theory is great but in the case of the D4D you do have to raise the voltage or
get a generator, solar panel, good battery charger etc to fully charge the battery

Cheers
LeighW

[drivesafe Senior Member Find all posts View Profile Close drivesafe]

Re: charging rate

Hi Leigh, again, while higher voltage is advantageous, even 13.0 volts will fully charge a battery.

There is no reason, other than time, why these alternators can not fully charge batteries.

240 vac battery charges use a little as 0.2v above the batteries SoC to charge them and contrary to the misunderstanding that a battery charger charges a battery at what ever voltage the charger is set at, IE, 14.1v, 14.4v or 14.7v, a battery charger is only capable of reaching these voltage levels once the battery is near fully charged and the same goes for a solar panel, via a regulator.

For those who maybe curious, the next time you have a low battery and intend to charge it with a battery charger measure the voltage at the battery terminals once the charger has been operating for 5 to 10 minutes, you’ll be surprised at how low the voltage actually is, but it will be charging.

Whereas with an alternator running at 13.2v and a battery that is at 12.0v SoC. The 1.2v difference is way higher than most battery chargers of even the largest size could hope for.

Again, time is the only requirement to an alternator being able to fully charge a battery(s)

[winniliss Avid PP Poster! Find all posts View Profile Close winniliss]

Re: charging rate

Hi,

To answer your question, yes I have a diode in my car, the voltage is around 14.5V cold alternator
and drops to about 14.1 V when the engine bay gets hot.

If you wish to go down this path a plug and play unit is available on EBAY for $35.

Cheers

LeighW

When to Jaycar today and got a 6amp 1000v diode and some crimp pins (same pins as what's on the end of the fuse. Soldered them together in line with the 7.5amp fuse (just in case the diode shorts instead of blowing) and used 5 minute araldite to keep it all together.

[LeighW Avid PP Poster! Find all posts View Profile Close LeighW]

Re: charging rate

Hi drivesafe,

Yes the battery will eventually fully charge as you write as long as the charge
voltage is above the terminal voltage and the current flow is geater than the losses
to over come self discharge.

The sticking point in these discussion is when the many members post "don't
have enough volts to fully charge" they are actualling saying I want the battery to
charge faster! 10 minutes woud be great, 2 hours grumble, 4-5 hours dam it's
taking a long time!

I'll settle for 4 - 5 hours, and unfortunately the D4D in standard kit is not achieving this :!:

A nice weekend to all,

Cheers
LeighW

[LeighW Avid PP Poster! Find all posts View Profile Close LeighW]

Re: charging rate

Hi,

To answer your question, yes I have a diode in my car, the voltage is around 14.5V cold alternator
and drops to about 14.1 V when the engine bay gets hot.

If you wish to go down this path a plug and play unit is available on EBAY for $35.

Cheers

LeighW

When to Jaycar today and got a 6amp 1000v diode and some crimp pins (same pins as what's on the end of the fuse. Soldered them together in line with the 7.5amp fuse (just in case the diode shorts instead of blowing) and used 5 minute araldite to keep it all together.

A word of warning,

You have now removed the protection the fuse offered. A short circuit in the sense wiring will result in the diode
over heating and possibly going short circuit. As I have written before, the leads of a 3A diode are capable
of carrying far more than 3 amps. If a short circuit should happen you now stand a considerable risk of damaging
the wiring, the Alternator or causing a fire in the worst case scenerio. That's why Toyota had a fuse there to start with!
I strongly suggest you incorporate some form of fusing arrangement.

By the way a 3A 1000V diode will give you a voltage increase but it is probably the worst choice you could have made
if your trying to get the best possible voltage rise. I suggest you pick a few more devices from a different family types
and refering to their data sheets, pick the one with the highest forward voltage drop for the quiescent current
conditions in the sense lead.

Cheers
LeighW

[winniliss Avid PP Poster! Find all posts View Profile Close winniliss]

Re: charging rate

Hi,

To answer your question, yes I have a diode in my car, the voltage is around 14.5V cold alternator
and drops to about 14.1 V when the engine bay gets hot.

If you wish to go down this path a plug and play unit is available on EBAY for $35.

Cheers

LeighW

When to Jaycar today and got a 6amp 1000v diode and some crimp pins (same pins as what's on the end of the fuse. Soldered them together in line with the 7.5amp fuse (just in case the diode shorts instead of blowing) and used 5 minute araldite to keep it all together.

A word of warning,

You have now removed the protection the fuse offered. A short circuit in the sense wiring will result in the diode
over heating and possibly going short circuit. As I have written before, the leads of a 3A diode are capable
of carrying far more than 3 amps. If a short circuit should happen you now stand a considerable risk of damaging
the wiring, the Alternator or causing a fire in the worst case scenerio. That's why Toyota had a fuse there to start with!
I strongly suggest you incorporate some form of fusing arrangement.

Cheers
LeighW

The diode is in-line (series) with the fuse so I still have the protection as stated before "Soldered them together in line with the 7.5amp fuse (just in case the diode shorts instead of blowing " unless I'm missing someting here... Here are some photos, total cost was about $5 time, about an 1hr (most of the time was exposing the top of the pins for the fuse). Tools req - soldering iron (small tip), sharp knife and a flat file. For info the crimp pins had red insulation around them that I cut off.

[LeighW Avid PP Poster! Find all posts View Profile Close LeighW]

Re: charging rate

Sorry Winniliss,

Doing two things at once here,

My appologies.

Cheers
LeighW

[winniliss Avid PP Poster! Find all posts View Profile Close winniliss]

Re: charging rate

Sorry Winniliss,

Doing two things at once here,

My appologies.

Cheers
LeighW

No worries, just making sure I haven't lost my marbles

[Big Fella Senior Member Find all posts View Profile Close Big Fella]

Re: charging rate

Hi Leigh, again, while higher voltage is advantageous, even 13.0 volts will fully charge a battery.

There is no reason, other than time, why these alternators can not fully charge batteries.

.............

Again, time is the only requirement to an alternator being able to fully charge a battery(s)

Well I have been reading this thread with interest and all of the others as well and all I can say (that's me and I have no real expertise in this arena) but after losing a brand new 2nd battery in my Prado after 1 year of use I am seeking a fix to this issue.

Basically from what I read it all revolves around what drivedrive keeps trying to say "it just needs time to charge". Sorry but I know that we do not have this elusive time thingy available for us. We tend to keep the fridge on in the car for 90% of the time, why........because we could, and there are always trips to the shops to be done as well. The car is only driven for about 40minutes each day and 50% is in stop start traffic on a good day. So voltage is not getting up there for starters. Yes, yes, yes, the cable being used is more than adequate for the job of charging the 2nd battery, as is the rest of the cabling in the car too distributing the power! We don't turn the fridge off because when we did it got a bit pongy on the nose (yes we clean it) and there is always that pesky water residue in there as well helping the smell along.

So I can't see the point of changing my cables for a heavier guage when they are already adequate for the task. I don't want to change the altenator. We don't seem to be able to change the factory setting of the voltage. So what do I do?????

Well it seems that I have a few options:
1. Get one of the those diode gizmo's.
2. Get a DC-DC charger/booster
3. Use my solar panel when the car comes home in the afternoon and hope like hell we don't drive off in the morning with it still connected.
4. Get a job further from home to get some more time into charging the batteries.

I will be watching with interest the outcomes of the diode as this seems like a good inexpensive fix. DC-DC looks good as well but $$$$$. But if it means my battery will last for more than 1 year then I'll buy one and have it installed

[LeighW Avid PP Poster! Find all posts View Profile Close LeighW]

Re: charging rate

Hi Big Fella,

Ignore my previous post if you read it, I'm awake now,

Hi Big Fella,

Your asking a bit there, without actual figures can only guess:

Using the fridge as a freezer we'll say it uses 1.2A which is conserative figure. You drive for about 40minutes
each day so the fridge runs of batteries for say 23 hours.

Total amps used 23 X 1.2A = 27.6A, you therefore need to put around 32A back in 40 minutes.

A DC-DC charger is not going to do that as the best you'll get from say a Ranox is around 25A

You could try a diode, it may be able in this case to put more back in, maybe drivesafe
has some tabled data with lets say an Alternator outputing around 14V and with 50A capacity
to spare?

Bottom line is will most likely take more time in either case.

Cheers
LeighW

[drivesafe Senior Member Find all posts View Profile Close drivesafe]

Re: charging rate

Hi Big Fella, Leigh pretty well covered it and in your situation, you will never fully charge your batteries using any of the suggestion you listed and that also goes with decent cabling.

I know you probably won’t like this BUT for the short times you drive, the lower your batteries are, the greater the amount of used capacity your alternator and decent sized cabling can replace as compered to anything else.

A 100 Ah flooded wet cell battery with an SoC of 30% will pull close to 30+ amps from an alternator with an operating voltage of just 13.2v and if you add the fact that the first 15 minutes will be at a much higher voltage, then you will be able to replace that much more of the used capacity, using nothing more than your alternator.

Remember, this all depends on the size of your cable and the length of the cable run between your batteries.

[drivesafe Senior Member Find all posts View Profile Close drivesafe]

Re: charging rate

Now there is one other option not covered and that to use two batteries, and the simplest way to do this is to fit one of my isolators.

Unlike any other dual battery isolator where they separate the cranking battery from the auxiliary battery when the motor is stopped, or soon there after, my isolators keep all the batteries connected and allows the surplus power of your cranking battery to be used to assist the auxiliary battery.

Big fella, in your specific case it could be a huge benefit to how you replace your used stored battery capacity.

Using Leigh’s figures to demonstrate, with your existing set up, you will pull say 28 amperes from a single battery set up but using one of my controllers, while you will still need 28 amperes to meet your need, you will only be taking 14 from each battery.

So now, instead of having a single battery that needs 28 amperes of power to be replace during your 40 minute drive, your auxiliary battery will only be down about half as much as it would normally need to be and even though your cranking battery also needs 14 amperes replaced as well, the fact that your alternator can easily charge both batteries at the same time, you will now only need to drive about 2/3 the amount of time to fully charge both batteries.

In your case as you will not be driving long enough to fully charge the batteries, you will still replace a bit under twice as much of the used capacity BUT because your auxiliary battery was not as low as it would normally be in a single battery set up, you will actually end up with an auxiliary battery that is probably around 85 to 90% charged, in just your 40 minute daily drive.

Note, your cranking battery will be in about the same state.