Thread: DC-DC charger- which one?

Thanks Peter, a most informative post. Having done this twice (2010 D4 and later in a 2015 D4) has allowed you to iron out the bugs very nicely.

Yes, my 40A DC-DC charger is way to big for my batteries. However my son has a 20A LV version in his Prado (and a larger aux battery set up) and he has expressed an interest to do a swap.

Jacques

Originally Posted by drivesafe

Hi Wheelan here is the thing, with your system and your 100Ah battery, you had 80Ah available if you discharged your 100Ah down to it's safe limit of 20% SoC.

If you had one of my isolators, you would have had 125Ah available.

But even if you still only used the same 80Ah, then the two batteries in my system, your auxiliary and your cranking battery, will only be discharged down to about 60% SoC and this means your batteries would be fully charged in a shorter drive time than your single 100Ah battery could be with or with out your DC/DC device.

The recharge time in a D4 is even quicker with one of my isolators fitted.

Then add the fact that with short driving trips around town and my system will actually keep your cranking battery in a higher state of charge, something no other system can do.

My thing is I am a bit old school and want to keep my starter battery for starting, and possibly winching if required the next day. I also feel my second battery has never been in better shape when properly charged from a proper 5 stage charger. Both systems have their merits, I actually dont need any more battery power than what I have already, 2 spares in the CT as well as the one in the car keeps everything going for a long time.

Originally Posted by drivesafe

The Optima D34 Yellowtop battery is a genuine AUTOMOTIVE GRADE AGM, specifically designed to tolerate the harsh conditions found in a engine bay.

These batteries also have NO CHARGE CURRENT LIMIT, and can and will take everything the alternator can produce.

Out of interest I have pasted the below info from Optima on the D34

"Model: D34
These batteries are designed for starting and deep cycling applications and for use in vehicles with large accessory loads.

Recommended Charging Information
Alternator: 13.65 to 15.0 volts
Battery Charger: 13.8 to 15.0 volts; 10 amps maximum; 6-12 hours approximate
Float Charge: 13.2 to 13.8 volts; 1 amp maximum (indefinite time at lower voltages)
Rapid Recharge (Constant voltage charger): Maximum voltage 15.6 volts. No current limit as long as battery temperature remains below 125?F (51.7?C). Charge until current drops below 1 amp.
Cyclic or Series String :14.7 volts. No current limit as long as battery temperature remains below 125?F (51.7?C). When current falls below 1 amp, finish with 2 amp constant current for 1 hour.
All limits must be strictly adhered to."

Food for thought....

Yes rapid recharge and cyclic recharge as stated is no current limit in the doc you posted note the limit put on chargers though

Originally Posted by RoverLander

BENEFITS:
Independent and 100% charging of all the batteries.

Well I would like to know how you know your battery is at a 100% charged state. Short of removing the battery and taking it to a laboratory for testing, there is NO WAY the determine if a battery is at a 100% state of charge while the battery is in a vehicle.

So that one is an advertising myth.

The industry standard is that any battery that is over 95% is fully charged.

Originally Posted by RoverLander

Correct charging foreach battery chemistry.

Yep this is a big problem when using a DC/DC device to charge batteries. You MUST have the same type of batteries if using one of these new DC/DC device to charge them.

Another one of these advertising myths.

If you let the alternator do what it has been doing for many decades, it will easily and CORRECTLY charge any mix of battery types and sizes with out any problems at all.

Originally Posted by RoverLander

Not effected by differences in battery temperatures.

Neither is charging by an alternator.

So once again another advertising myth

Originally Posted by RoverLander

You can charge from a solar panel.

NOT AT THE SAME TIME.

So I am not sure how you think this is a benefit???????

Whereas, if you are towing a caravan with solar on the roof, you only need a solar reg in the caravan ( which you will need anyway ) and you can be charging ALL BATTERIES from the alternator and solar at the same time.

So in a nut shell, charging from an alternator is far more beneficial and a hell of a lot cheaper to setup AND OPERATE

Originally Posted by Wheelan

My thing is I am a bit old school and want to keep my starter battery for starting, and possibly winching if required the next day. I also feel my second battery has never been in better shape when properly charged from a proper 5 stage charger. Both systems have their merits, I actually dont need any more battery power than what I have already, 2 spares in the CT as well as the one in the car keeps everything going for a long time.

Hi Wheelan and as the operating system of my isolators has been around for more than 25 years now, I reckon that makes it OLD SCHOOL technology but my old school technology is still proving to be FAR SUPERIOR at charging batteries than any of these NEW wonder devices.

As for using a 5 stage charger goes, well thats a pretty simple way to charge lead acid batteries when you could be using something like a charger with an INFINITE number of charge stages, you know like how an alternator charges.

The problem with battery chargers, DC/DC devices and Solar regulators is that they are trying to copy what an alternator does, and does naturally, but battery chargers, DC/DC devices and Solar regulators are constant CURRENT charging devices and this is a major limitation for these devises.

Whereas, an alternator is a constant VOLTAGE type charger and constant voltage type charging is FAR SUPERIOR when it comes to charging lead acid batteries.

For example, when was the last time you heard of an alternator cooking a battery. It does not happen. But it is a common occurrence with both battery chargers and DC/DC devices.

Battery chargers and DC/DC devices just can not compete with how well an alternator works at charging batteries.

Now to your winching operation. It is known in the industry that there is a huge advantage to connecting two batteries together while winching.

Using one of my USI-160 isolators, you not only get the advantage of shearing the load while operating accessories but you get the huge advantage of linking batteries together while winching.

A win-win setup.

Originally Posted by SilvaD4

Out of interest I have pasted the below info from Optima on the D34

"Model: D34
These batteries are designed for starting and deep cycling applications and for use in vehicles with large accessory loads.

Recommended Charging Information
Alternator: 13.65 to 15.0 volts
Battery Charger: 13.8 to 15.0 volts; 10 amps maximum; 6-12 hours approximate
Float Charge: 13.2 to 13.8 volts; 1 amp maximum (indefinite time at lower voltages)
Rapid Recharge (Constant voltage charger): Maximum voltage 15.6 volts. No current limit as long as battery temperature remains below 125?F (51.7?C). Charge until current drops below 1 amp.
Cyclic or Series String :14.7 volts. No current limit as long as battery temperature remains below 125?F (51.7?C). When current falls below 1 amp, finish with 2 amp constant current for 1 hour.
All limits must be strictly adhered to."

Food for thought....

Here is some more food for thought, when using an alternator to charge Optima batteries, you will NOT exceed ANY of the limitation set for these batteries.

So mate, sorry but I don't get your reasoning for making that statement?

For example, two and a half years ago, my wife's Toyota Seca's battery died so I put an Optima D34 Yellowtop in to replace it till I got around to replacing the battery.

About 2 months back I finally had to charge the battery because the Optima died.

It was 7.5 years old when I put it in the Toyota, making it 10 years old when it died.

It had been in my D3, then my D4, then my Range Rover, then is sate in the work shop for nearly a year and in the ten years I had that battery it was only ever charge by a battery charger on about three occasions.

So charging straight off the alternator really shortens the life of these batteries NOT.

Originally Posted by RoverLander

If you are installing your battery in the cargo area the please ensure it is a fully sealed battery (to avoid potentially dangerous gases in the car interior).

A couple of other points, there is no such thing as a fully sealed lead acid battery and if you check, most lead acid batteries are now marked as "SPILL PROOF", not "SEALED" and as a DC/DC device can cook a battery, while an alternator will not.

So you are far safer charging a lead acid battery, mounted in the cab of a vehicle with an alternator, not a DC/DC device!!!

Originally Posted by RoverLander

MY15: I have one 100AH AGM battery in the rear cargo area (as described above). This is secured to a shelf and cargo barrier system. The DC/DCcharger is mounted on top of the battery box. This way there is minimal distance between the charger and the battery. The DC/DC charger is in a cool area of thecar so will charge at full rate.

For less money, you could have fitted one of my Triple Battery systems, which simply mounts two Optima D34 batteries in the engine bay.

This would give you more available space in the cargo area.

It would also give you more usable capacity. 80Ah with your system and around 125Ah with my system.

It would save fuel.

But the biggest advantage is that with your setup and a low battery, it will take 5 hours of driving time to fully recharge your battery, mine will fully recharge the two Optimas in less than 90 minutes.


Now if you only need that 80Ah that you have, you could still have fitted one of my standard dual battery systems, with a single D34 Optima battery.

You would then have had around 90Ah available instead of your 80Ah.

The setup would have been heaps cheaper than the one you have.

You would still fully charge the optima in under 90 minutes.

My setup is lighter and therefore you save even more fuel.

Both my standard and triple battery systems look after the cranking battery as well as the auxiliary batteries, your is only looking after your auxiliary battery.


I'm sorry mate but I just can't see how you, and the others, think that you have better systems when they all have so many inherent drawback.

Your logic just does not make sense