Caravan Battery Level

Bush camper,

Do you run a booster diode, it would improve your charge rate but that is a lot of battery capacity you have connected.

Leigh

No, where would this be fitted?
When camping I use a 120watt solar panel for the battery in back of cruiser and the van has a 135 watt solar panel.

What is the make and model of your car?

200 series landcruiser, GXL, built late 2102, Diesel V8

The 200 series is fitted with a low output alternator, charge voltages of 13.5V or lower are common with this model, fitting a booster diode will restore your vehicles charging voltages to close to those of a standard alternator improve your battery charging considerably.

Cheers
Leigh

If there are two 100 amp hour batteries and they are half discharged.....it will require a 20 amp charge rate of at least 6 hours to achieve a full charge.

Problem is the charge rate decreases as the level of charge in the battery increases.....so even with an initial charge rate of 40amps...it may still take 8 to 10 hours..or more to achieve a full charge.
Because toward the end of the charge cycle tha charge current may be as low as 5 amps.

One of the consistently re-occuring reasons for batteries failing to charge is insufficient time allowed.

AND...no gismo, Dc to Dc charger or snake oil will change that situation much.

cheers

No one suggests you can get a full charge in 3 or 4 hours with standard batteries – that’s being silly Bantam.
Many AGM's such as Lifeline and Optima can get up to 95% state of charge in 2 hours - I could go into the technical details but it would be a waste of time.

There are plenty of people that think they can charge a large battery in a couple of hours driving.....plenty of those people have batteries dying prematurely.

NOT many AGM...a certain few can be rapidly charged.

Certain AGMs have a very limited maximum initial charge rate...a particular popular Fullriver 100AH is limited to arround 20 amps maximum initial charge rate.

Yes I am aware of the claims that certain batteries claim to be able to charge very quickly.....AH yes...but then there is the detail..always the detail.

Have you ever charged an optima or a lifeline, from an unmodified car alternator, in a trailer,from a low state of charge to a proven 95% charge in two hours.
If so..how did you measure it.


the fact remains that for most people charging a pair of 100Ah batteries, from a low state of charge, in a trailer, from the standard or even voltage bumpeded alternator will take in the reigon of 6 to 10 highway driving hours.....if all is going their way.

cheers

You don’t need to fully charge a good deep cycle battery each time – a full charge every 8 or 10 times is OK.
That’s according to the manufactures specs for my AGM – I stick to manufacturer’s specs rather than e-opinons of unknown credibility.

Its an unavoidable reality that if you fail to put in more charge than you take out, day after day, the battery will soon not last the night in the short term and in the long term will fail...regardless of battery type or capacity.

The single biggest reason for battery disapointment, is failing to provide sufficient charge time.

cheers

Bantam
To avoid repeating myself, see my comments further down the post.

That’s the way to go.
A DC/DC charger in the caravan, compensating for the volt drop between the vehicles, is the only way to get a decent charge into the van’s battery.

Here we go again.....DC to DC chargers are NOT the only solution.

Correctly sized wiring and the proper charge voltage will do the job..and in some situations better.

cheers

It’s impossible not to have voltdrop between the vehicles alternator and van battery - no matter how large the wiring.
My alternator will put out about 13.6 volts and I set the DC/DC charger output to about 14.5 volts.
This is a much better charging effect on my batteries using 14.5 volts as opposed to something less than 13.6V
In most cases the DC/DC charger is the most practical solution.

It is impossble to have current flowing in any wire and not have voltage drop.

That does not make it an unavoidable problem for charging batteries.

Heavy enough wiring...and it does not need to be rediculously heavy will overcome any problems with voltage drop.



YOUR problem is that your alternator has a poor voltage output to start with.....all you are doing, is using your DC to DC charger to increase the voltage.

Installing a 14.2 volt alternator or fitting a diode fuse along with adequate wiring would in many cases result in more rapid charge than your DC to DC charger.

Don't claim that a DC to Dc charger is the only way to go because it just is not true.

cheers

Mine is not an uncommon voltage – it’s in a 2008 Toyota.
Vehicle manufactures have it at that voltage level for reasons I won’t go into.
It silly to say change your alternator to a higher voltage, when you can do a better job with a DC/DC charger and also keep the voltage for the battery under the bonnet at the correct level.

The lower voltages Toyota now run have nothing to do with maintaining the correct voltage levels for the battery, they have lowered the voltage levels to meet overseas emission requirements and to improve fuel economy figures. This has resulted in a significant increase in warranty claims for cranking batteries due to the poor charging voltage.

Toyota have slightly increased the charging voltage in the latest Prado's for instance to try and overcome the high rate of battery failures.

The dealers have are also suggesting occasional charging with a battery charger too.

Increasing the voltage back to normals levels by use of a booster diode is both beneficial for both the cranking and auxiliary batteries.

I would have thought that with a name like HKB Electronics you would appreciate the fact that the voltage level for charging a battery varies with temperature.
I have seen studies by Exide that show under bonnet temperatures for sedans around 70 degrees.
I have measured my V8 diesel around 80 degrees – the battery electrolyte reaches the mid 60’s.
Bantam’s suggested 14.2 volts for under bonnet batteries will shorten their life – it’s well published engineering data. Toyota's voltage for my vehicle of 13.9 volt for a cold motor and 13.6 volt when hot, is correct and I wouldn’t be changing it to a higher voltage on an a layman’s recommendation.

You don’t happen to sell these diodes do you? – maybe you could flog a few to Bantam.

Again Dennis brings up esoteric half truths.

Any temperature over 25C will reduce lead acid battery life..regardless of charge voltage.

On the one hand you sprout the rapid charge capacity of some AGM ( to achieve those very fast charge rates quite high voltages are required) on the other hand you espouse lower charging voltages.

On the one hand you claim that you cant fully charge a battery on the lower voltages and that a dc to dc charger is required and on the other hand you claim that underbonnet temperatures require lower voltages

Ya cant have it both ways.

When we mostly ran screw top batteries almost without exception the charging voltage of a car alternaotor was 13.8 volts.....this was chosen because it is the best compromise between expedient charging and fluid loss....it remains the prefeered float charge voltage for almost all lead acid family batteries.

When we started to see vehicles come from the factory with sealed maintenence free batteries the alternator voltages stepped up .6 volts of a volt to in most cases 14.2 volts.
This is because the calcium in the plates, altered electrtolite chemistry and gas recombination is sealed batteries allows ( some argue requires) the additional voltage.

WHY would pretty well all manufacturers increase the alternator voltage from 13.8 to 14.2 volts when fitting sealed batteries if it was not a good idea.

People have been geting reasonable life (3 to 5 years) out of batteries under bonnet for decades with those set charge voltages.

While there may be an in theory case that higher charge voltages with high underbonnet temps may reduce battery life....in reality the case is not proven reasonable.
High under bonnet temperatures will reduce the life of the battery regardless of the .6 volt difference.

There IS however a case and it is well known that some of the very recent, tree hugging, low alternator voltage cars are expereincing a chronic failure to sufficiently charge the factory fitted cranking battery and reduced battery life because of it.

While battery manufacturers have been publishing temperature compensated charge curves and battery life V temperature data for decades.
In general it is not common to vary charge voltage unless the charge process is being pushed near limits.

In most vehicles the alterenators and batteries are sized such that the alternator is incapable of pushing the battery near limits in normal use.

There is also the argument that even normal non ecu controlled alternators are at least to some degree temperature compensated.

as I have posted before..don't bother about the esoteric and the obscure...get back to the simple basis.

sure higher temperatures may reduce battery life...but chronic under charge will do as much if not more damage....and that is a certanty.

cheers

Dennis I suggest that you actual do some research before commenting, alternators are temperature compensated, the booster diode simply restores the charge voltages to same levels that have been used to charge lead acid batteries since cars were first fitted with batteries ie 14.4V@22C or there abouts. Why this voltage because that is what was determined to be the best voltage to charge a lead acid battery some 100 years ago and it hasn't changed since!

Your DCDC charger will change at around 14.4V CTEK and 14.5V Redarc under the same conditions ie they simulate what the alternator does and that is what it was designed to be a pseudo alternator.

HKB
My vehicle has a temperature compensated alternator – starts at 13.9v and after it heats up, drops back to 13.6V. Toyota engineers do that to prolong the life of the battery in a very hot environment.
My DC/DC charger charges a battery in a cool environment. Totally different voltages required.
But I understand the need to flog your voltage booster, and this will make these observations irksome.

Bantam
A lot of under bonnet batteries live their life undercharged.
In my case the 4WD is not used more than once a week when I’m in town.
I need to trickle charge it when it’s sitting idle to gain maximum life from my batteries.
When camping, the AGM in the caravan is only fully charged once a week - it’s not practical to get a 100% each day - the other 6 days possibly gets to around 80%.
According to my manufacturers specs this is a good charging regime.
I can’t go into the rest of your comments - they shoot off in all directions.
I would take for ages and would be a waste of time.

Dennis your just plain wrong, as I already wrote Toyota dropped the voltages to meet pollution requirements at the cost of battery life, if you don't wish to believe me I suggest you talk to a Toyota service technician.

There are many other makes out there still running standard charging voltages as they have been able to meet the pollution requirements without altering charging levels.

Your vehicle has a high compensation type alternator, initially it will start charging at a reasonable voltage to put some charge in the battery but as soon as the temperature under bonnet nears the temperature at which vehicle emissions are tested, it will reduce the charging voltage way below what is required to maintain the correct temperature compensation.

To shot your claims down your argument in flames, and as I have already mentioned Toyota in their latest models have raised the charging voltages somewhat in an attempt to lower battery warranty claims, so much for the lower voltages being good for the battery!

I suggest you do some reading on reducing charging voltages as a way of meeting vehicle anti pollution standards. This information has been around for many years.

Dennis, buy the way a further naoil in the coffin for your argument, if you do some research you will also find most of the petrol models Toyota make if not all, still retain the stand temperature compensation type alternator and higher charge voltages, why because they were able to meet the anti pollution standards without reducing the charge voltages, it is only the diesel models that need the reduced voltages.

My vehicle runs at 80 degrees C under the bonnet
Battery manufacturers specify much reduced charging voltages for that temperature.
This data is readily available online from battery manufacturers and suppliers.

Some battery manufacturers specify a maximum opperating temperature of 50C for certain batteries.

That puts them out of spec sitting under a shady tree in some locations in summer.

Various batteries tolerate temperature exreems better than others.
The temperature corrected charging voltages along with the need to correct will vary from battery to battery.

Most of the big cranking battery manufacturers publish very little in the way of detailed information on their batteries.

Hell none of the volume battery manufacturers will even give you an amp hour rating on a cranking battery.

There is also an argument that all under bonnet batteries in warm climates have a reduced life from ideal.....but the actual life achieved is considered acceptable.


The fact of the matter is that there are tens of thousands of vehicles out there running 14.2ish volts charging their under bonnet batteries ( HKB and Banmtam incluided) and there is not a string of what is considered premature failures.

But there is a strong documented base of information that shows there ARE many premature battery failures due to this limp wristed charging voltage in certain vehicles.

Cheers

The booster diode does not alter the alternators in built temperature compensation, it simply restores the base voltage to those similar to a standard alternator, ie those used in the petrol versions, by the way the petrol engine models will run hotter under bonnet temperatures than your diesel yet they still run standard alternators!

There are many thousands of boosters in use by happy users with no adverse affects being reported, the following was posted today on another forum, i believe it says it all:

"I did the Ctek d250s in the 120 series. I had it connected to a redarc relay to ensure the aux battery only charged after the main.. I was never really that happy with this set up. The aux battery never really got completely charged, particularly when camping at say Fraser or Rover Park where the aux battery ran down overnight and you then did short runs during the day. My theory was that the Ctek goes through multiple stages of charge before you get to the bulk stage every time you restart the vehicle. You need a good couple of hours of continuous running to get anywhere near full charge ( depending on state of discharge). I had endless fridge troubles with the battery running below safe voltage. In the end the Ctek somehow managed to boil the aux battery , about three months before I sold it. Made a mess of the inner guard that I had resprayed.

The 150 has the simple redarc relay and the voltage boosting diode. This works a treat. You can't beat good volts and solid amps."

Bantam
I wouldn’t touch a battery that’s limited to 50 degrees.
If you buy equipment which doesn’t include specifications – that is your choice.
This is where we differ – I have no problem obtaining specs for the batteries I use.
I don’t go for the Micky Mouse stuff.
I think we are both wasting our time on this subject, it’s gone right off thread, and you and I are on different planets.

Ya got that right.
I don't know what plannet you are on But I am on planet Earth with my feet firmly on the ground.

Its one thing to get the specs its another to know what they mean.

cheers

Yes indeed if the 3 way fridge is running on the same cable as the battery..particularly if the cable is inadequate or marginally adequate.

The current drawn by the fridge will cause voltage drop and may result in a total failure of the battery to charge.

Either you will have to use considerably heaver wire to accomodate the additional current or wire the two seperately.

Three way fridges are notorious for beeing inefficient on 12 volts..because pretty well without exception they are inadequately wired.

Actually...worst case....with the three way fridge going....low alternator output...and poor wiring your battery could be going backwards.

cheers

Thank you to all responses. My response to some points raised include:
I tow with a 2012 Prado which has one of the "smart" alternators.
I fully charge 2x100amp van batteries on 240V prior to leaving on trips.
I am currently testing the van to assess the battery draw for each individual appliance i.e. LED lights (very small), fridge on gas with small 12v thermal fan operating (used about 1/4 to 1/2 battery power over 24 hr period). The other power consumers to test include the water pump (5.2 amps) and the electric breakaway unit.

I am also considering options when travelling including second battery in the Prado to power Engel from 12v plug not the inverter plug will probably go with Redarc system.
Also looking at options for more charge to the van batteries from Prado. I have checked with multi-meter which shows that the majority of the power when travelling is going to the fridge on 12 v. Will need to consider capacity draw on the alternator to power all these things.

Regards

smithie12,

Fitting a booster diode such as mine unit or one of the others available will greatly improve your alternators charging ability, I would suggest you visit Pradopoint as this subject has been addressed in great lengths there.

Cheers
Leigh