Dual battery setup for 2.8 1GD

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

You'll need to decide for yourself whether you believe that fancy colour graphic in the middle of that page, or the battery manufacturer's data quoted on the page after.

Hi dBC it is obvious, from your statements, that you have very little experience in this field.

The “FANCY” table, that you are trying to ridicule, is a simplified version of a table that has been provided in technical documents by battery manufacturers and other providers, for at least the last 30 to 40 years and is used to measure a battery’s SoC, while the battery is in use, LIKE WHEN IT’S IN A MOTOR VEHILCE.

The fact that you used the OPEN CIRCUIT voltage as a charge reference clearly demonstrates that you have no genuine experience in this field.

But whats worse is that while you were using to wrong voltage reference from Optima’s web site to back your claims, you at the same time, very conveniently neglected to mention that the same battery manufacturer specifically states that you can fully charge their batteries with a voltage of 13.65v.

OOPS, you couldn’t post that info up as it would completely destroy your claim that you needed a higher voltage than the alternator can produce, to fully charge a battery.

[dBC Member Find all posts View Profile Close dBC]

Geeze, steady petal... what's got up your nose? As I said above, I consider myself entirely neutral.... each have their benefits and disadvantages. I've always used VSRs when the alternator voltage permits.

The “FANCY” table, that you are trying to ridicule, is a simplified version of a table that has been provided in technical documents by battery manufacturers and other providers, for at least the last 30 to 40 years and is used to measure a battery’s SoC,

Technology moves on, so should you.

while the battery is in use, LIKE WHEN IT’S IN A MOTOR VEHILCE.
The fact that you used the OPEN CIRCUIT voltage as a charge reference clearly demonstrates that you have no genuine experience in this field.

Well, here's a simple test for someone with a 2.8L Prado, a VSR and an Optima battery:

. partially discharge your camping battery
. go for a nice long drive
. the instant you stop, rush to the engine compartment and isolate the camping battery
. leave it that way for at least 24 hours
. report the voltage at the battery terminals
. if it's reading 13.1V we know it's fully charged

This guy: http://www.pradopoint.com/showthread...l=1#post556058 claims that's what he sees when he tries that experiment with his DC/DC charger. If the VSR connected to a 2.8L Prado alternator can do the same then we're done here.

neglected to mention that the same battery manufacturer specifically states that you can fully charge their batteries with a voltage of 13.65v.

So where do you suggest a 2.8L driver gets 13.65V? I rarely see that voltage when the engine is running, and that's with dedicated wires running from the cranking battery to a voltmeter that draws about 7.5mA so there is pretty much zero voltage drop down that wire. And also confirmed with a precision recently calibrated voltmeter on the battery terminals. You can see here: http://www.pradopoint.com/showthread...l=1#post554331 that the 13.4V displayed in my icon to the left is at best 13.5V.

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

So what you are suggesting is that everybody should disconnect their batteries and leave them for 24 hours and then do an OPEN CIRCUIT voltage test.

I can see how helpful that sort of testing is while you are off on a trip.

As I posted, OPEN CIRCUIT voltage testing is useless in RV situations and the table I posted up is both relevant and still in use today.

And before you make comments like “Technology moves on, so should you” you might actually try learning about the technology you quite obviously haven’t got a clue about.

Instead of telling everybody they have to waste 24 hours just to get an idea of their battery’s SoC, they could simply use the table I posted up or the many hundreds of similar tables, and with just a small load of about 5% of the battery’s capacity, connected to the battery, and they could get a accurate indication of the battery’s SoC in a couple of minutes.

Furthermore, OPEN CIRCUIT voltage readings are only accurate if you know, in advance of taking the measurement, that the battery is OK.

Common occurrence when taking OPEN CIRCUIT voltage readings to get an indication that the battery is fully charged, yet it will go flat with in minutes of applying even a small load to the battery.

Whereas, when using my table, if the battery is stuffed, the voltage reading will be falling as you are taking the measurement, so again, no need to waste 24 hours when you are getting an almost instantaneous indication that the battery is stuffed.

Again, before you comment about some else’s knowledge , might pay you to get yourself up to date!

[dBC Member Find all posts View Profile Close dBC]

So what you are suggesting is that everybody should disconnect their batteries and leave them for 24 hours and then do an OPEN CIRCUIT voltage test.

Not at all, I'm suggesting someone do that experiment just once, with a new battery. Then we'll know for sure whether a 2.8L Prado can fully charge such a battery. Oh, and you forgot to answer this part:

So where do you suggest a 2.8L driver gets 13.65V?

[120D4D Avid PP Poster! Find all posts View Profile Close 120D4D]

Well, here's a simple test for someone with a 2.8L Prado, a VSR and an Optima battery:

. partially discharge your camping battery
. go for a nice long drive
. the instant you stop, rush to the engine compartment and isolate the camping battery
. leave it that way for at least 24 hours
. report the voltage at the battery terminals
. if it's reading 13.1V we know it's fully charged

This guy: http://www.pradopoint.com/showthread...l=1#post556058 claims that's what he sees when he tries that experiment with his DC/DC charger. If the VSR connected to a 2.8L Prado alternator can do the same then we're done here.

C'mon guys, make love not war!

An interesting idea DBC but perhaps open to too many variables?

As you've dropped me in this I guess I would fit the bill, having a 2.8L and an Optima aux battery and a DC/DC device - I dont have an isolator or couple metres of 6B&S on lugs but I'd be happy to run your test if anyone cares to lend the VSR and cable.

I guess I already know the result and must admit I dont want to go for a multi-hour drive to run the test!

Suggest with a simple isolator we would find the Optima pulls lots of Amps and takes on the bulk of charge very quickly then slows off thereafter. Nothing that hasnt already been pointed out by drivesafe and LeighW in the past...

That said I would be geniunely interested in the result - if the test can be arrange in such a way that I can run it around town on short-ish trips as this is my daily drive.
Suggest this would favour the isolator option somewhat though.

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

I didn’t forget, as I already have people testing my gear in new Toyotas, and they are seeing different voltage readings to yours.

Once again, the table I posted up is generic, in that all 12v lead acid batteries behave the in a similar manor once a load of the size I suggested, is connected to the battery being tested.

The same is NOT the case when carrying out a OPEN CIRCUIT voltage test on a 12v lead acid battery.

You have to have a copy of that battery’s specific OPEN CIRCUIT chart or you will get incorrect info, and the differences are quite large.

For instance, most AGM have a fully charge OPEN CIRCUIT voltage of 12.8 to 12.9v, while Optima Yellowtops have a fully charged OPEN CIRCUIT voltage reading of 13.1v, and many wet cell batteries will have readings between 12.7 to 12.75v.

So which OPEN CIRCUIT voltage chart do you recommend people use?

Once again, in RV situations, using OPEN CIRCUIT readings are a waste of time.

[dBC Member Find all posts View Profile Close dBC]

I didn’t forget, as I already have people testing my gear in new Toyotas, and they are seeing different voltage readings to yours.

What is your gear, and what voltages are they seeing? Mine starts high-ish (13.6V) and after about 20 mins or so drops down to about 13.3V.

So which OPEN CIRCUIT voltage chart do you recommend people use?

The one for their battery, from the manufacturer. But remember, I'm only talking about using it for a one-shot experiment by some willing volunteer with a recent install. Then we'll know for sure if the alternator voltage is adequate for getting that battery type to 100% charge.

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

C'mon guys, make love not war!

An interesting idea DBC but perhaps open to too many variables?

As you've dropped me in this I guess I would fit the bill, having a 2.8L and an Optima aux battery and a DC/DC device - I dont have an isolator or couple metres of 6B&S on lugs but I'd be happy to run your test if anyone cares to lend the VSR and cable.

I guess I already know the result and must admit I dont want to go for a multi-hour drive to run the test!

Suggest with a simple isolator we would find the Optima pulls lots of Amps and takes on the bulk of charge very quickly then slows off thereafter. Nothing that hasnt already been pointed out by drivesafe and LeighW in the past...

That said I would be geniunely interested in the result - if the test can be arrange in such a way that I can run it around town on short-ish trips as this is my daily drive.
Suggest this would favour the isolator option somewhat though.

Hi Michael, I might just take you up on that offer, but in the meantime, try measuring your CRANKING battery voltage in the morning, before you start your motor.

NOTE, the table I posted up is idea for this sort of testing, as the cranking battery in almost every modern vehicle will have a constant load on it, all be it a VERY small load, but it makes the voltages compered to the table, pretty accurate.

[LeadWings Member Find all posts View Profile Close LeadWings]

New 2.8L Diesel and Lithium Trailer Battery

I have a confession, I have a lithium battery in my camper trailer. I have also just bought a new 2.8L Diesel Prado, and ran a charging test on the weekend and thought I would post some info on how it went.


I am hoping this does not turn this thread into a "Lithium vs Lead Acid" war, similar as tends to happen with alternator charging vs DC-DC convertor posts. So here goes.


Lithium batteries have very different charging requirements and methods than lead acids. For a 4 cell/12 V setup, the optimum charging setup is throw heaps of amps at the battery as long as it does not go over the voltage set point, say 3.55V per cell or 14.2V for a 4 cell pack is about optimum, then hold 14.2 volts and taper the current till the battery is full. So when I got the Prado, and put a battery meter in the dash, I noted that it tends to hold 13.8V. That is about 3.45 V per cell - which is around 95% full. So I figured this could be good - if the Prado can quickly charge the battery to 13.8V, then I won't need a DC-DC or similar.



Some background on my setup - 2.8L Diesel Prado, with VSR and 6 AWG/B&S twin wire to an Anderson on the tow hitch. Camper trailer has smaller wire (too hard to change) I am guessing 8 or 10 AWG 3m back to the battery. Battery is a 100 A Hr 4 cell LiFePO4 Winston lithium pack made up from some cells from an electric car that got tired. Currently don't have a second battery fitted to the Prado.


Camper trailer (Trak Shak) has 2 fridges, both 35L Waecos and some LED strip lights.



So I was going away for a 3 day weekend, and I thought a perfect trip to do some measuring. Measuring was done with a PowerLog 6S connected directly to the battery in the camper trailer set to log every 30 seconds.




I connected the battery around 9am Sat morning to run the fridges and get them cold. We set off around 12ish, and the drive was around 1 1/2 hours. We then set up and ran the fridges for rest of Sat, Sunday, and Monday. Packed up and connected the trailer to the Prado again around 10am Monday and drove it about 50m, it then sat for around 2 hours before the 1 1/2 hour drive home. Then turned the fridges off etc and disconnected the battery. Was a fairly cool weekend, say 15C in day and 5C at night, so fridges were not working too hard.


Attached are a voltage plot, a AHr plot and a current plot. I also watched the volt meter on the dash when driving, and it did go down occasionally to say 13.4V but generally stayed around 13.8V.


Firstly the voltage plot - you can see the voltage is hovering around 13.2V before I connected the Prado to leave. Don't know why this was so low, as the battery was charged a few days before. You can then see that the voltage goes up to around 13.4V while being towed. Then while the trailer is sitting there for the weekend the voltage drops from around 13.25V to 13.1V (bumps are due to voltage sag as the fridges cycling on and off. Then the jumps up to 13.3V as the trailer is towed home.




Amp-Hr plot - Fridges use around 5 AHr getting cold, recover around 3 AHr while towing to site, then use around 40 AHr over the weekend, then recover around 3 - 4 AHr on the drive home.



Last but not least the current plot. Fridges suck around 2A when on, so you can see the 2A spikes for one fridge, then 4 A if they are both on simultaneously. You can clearly see the negative current when the battery is being charged by the Prado on the way there and the way home - around 2 to 3A, and impacted as the fridges cycle on and off. Odd spikes to 5A, but they look short.




It looks like as it is set up I would only get 2-3 AHr per hour of driving, which is no where near enough for sustainable use on an extended trip of driving every day for say 3-4 hours - we would be using 20-30 AHr per day, and getting at best 8-12 AHr back. So would need mains/solar supplement.


So my conclusion? I would like it if the system voltage could be adjusted up, to say 14.2V but it looks like the simple diode type fix isn't available for this model (yet - here's hoping).


So I think I will bite the bullet and install 6 AWG/B&S wiring in the trailer if I can, measure again and will probably have to get a DC-DC converter.

[dBC Member Find all posts View Profile Close dBC]

What a nifty little logger. I want one!

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

Hi Leadwings, I have been working with lithium batteries for about 5 years now and there are so many recommendations on how they should be charged and maintained.

Unlike lead acid batteries, where you should give them a good charge to get them to a fully charge state before you put them in storage, many of the lithium battery manufacturers recommend that their batteries are not charge to 100% if they are to be stored for any length of time.

You would need to contact your battery’s manufacturer, not the supplier, but the manufacturer, to get exact details relating to your specific brand and type.

Anyway, while in use, you can cycle them from 20% to either 95% or 100% depending on your charging setup.

If you are getting 13.8v at the battery, when it is near fully charged, then your battery should be in the 95% to 100% range, and you can drive all day long and not harm your battery while the voltage is at 13.8v but no higher.

Storage, and again, you need the specific specs for your battery, but 13.8v charging voltage before storing should be ideal.

Now to the catch with lithiums, which you are probably aware of. The terminal voltage is no indication of the capacity, and as you posted, you had a terminal voltage of 13.2v after charging. I think you will find that the battery was still fully charged.

If you want to find out how well charged your battery is, after a trip, you can only get this sort of info with a lithium battery if you install a full battery monitoring system, and that can get expensive!

Or for your own piece of mind, you can carryout a constant current load test.

You simply get something like a 21w 12v globe and apply it to the battery and see how long the battery powers the globe.

NOTE, this is something you should only do if your battery has it’s own BMS. Otherwise you are going to have to setup a means of disconnecting the battery when it’s voltage drops to 12.0v, which only occurs at the end of the discharge cycle. Other wise, you can damage a lithium battery with a single over discharge cycle.

[dBC Member Find all posts View Profile Close dBC]

Drivesafe, what charging voltages are your 2.8L Toyota customers seeing?

[LeadWings Member Find all posts View Profile Close LeadWings]

What a nifty little logger. I want one!

Must say I've been impressed with its functionality, and the insights it can give. Was about $65 delivered from the US, came in 2 weeks. http://www.progressiverc.com/powerlog-6s.html

[LeadWings Member Find all posts View Profile Close LeadWings]

Hiya Drivesafe, I'm pretty up with Lithium stuff too - the battery has a BMS and low voltage cut-out. And I have a different meter I use to measure AHr in and out when in use.

But to me the take out for this thread is that for my setup the Prado only delivered 2-3 Amps into a near fully charged battery, and then on the way home with a battery that was at least 40% discharged (ie had taken 40 A Hr out of a 100 A Hr battery) it still only delivered 2-3 Amps. So it will not do for my requirements (and for most other peoples if they are set up the same - the reason for posting the data).

So my first step will be check for voltage drops in the chain from the Prado battery to the trailer battery and eliminate if possible. But I expect that may only get me up to say 8A or 10A at best - which will not be enough. So then it may be a DC to DC.

[Guest Close Guest]

Is the low state of charge (2-3Ahr/hr) due to lithium batteries maintaining a near constant voltage while it is being discharged?