Dual Battery Options and Fitting

[drivesafe]

I’m sorry Transporter but you just don’t understand how either device really works.


If your theory was correct then things like alternator to battery chargers, which are high current DC/DC devices, that are specifically designed to allow an alternator to run at full capacity for long periods of time, but if your theory was correct, they would destroy alternators.


These devices are selected so that the DC/DC unit is larger than the alternator. For example, with your 220 amp alternator, you would need to fit a 300 amp alternator to battery unit.


This would allow your 220 amp alternator to run continuously at it’s maximum current output.


And these devices have a heat sensor for the alternator and have been around for years and none of them cook alternators, even though they are continuously running the alternator at full output currents.


So if someone has a genuine need for high current charging, then there are REAL DC/DC devices that will meet their needs.


For the average RVer, there is actually no need for a DC/DC device in the vast majority of dual battery setups. Your alternator will do a better job of charging any batteries you need to charge.

[Transporter]

I don’t know what are you trying to push here or if you’re selling or advertise your product. Maybe you should introduce yourself. I have repaired enough alternators in my life to know how they work, what they’re made of and how they fail.

...and from my experience with aftermarket products, if anyone who needs DCDC charger should stick with well proven product like REDARC BCDC charger with well established back up, after all they’ve done enough research work. For the cheaper options the Projecta has also BCDC charger that works.

[Bryn23]

this thread has progressed.

I did mean the extra load on the alternator stresses it over time, there is a reason that most of all the vans (VW,FIAT, MB) i've looked at have a upgraded alternator option if running heaver loads

a few even made the upgraded alternator part of their house battery system when you upgraded to aux battery system.

There are websites out there that talk about limited lifespan of alternators with accelerated bush wear and failure, alternators aren't designed to run at full load 24/7, they have a duty cycle like every other accessories.

They will protect themselves to some extent, but these things are built to a price.

I looked at DC-DC, due to the fact, i also wanted control of the amps put into the battery, a lot of batteries recommend max 20% charge of the battery capacity.

I appreciate that you system charges faster, but i'll prefer to keep my battery within the recommended voltage that the battery asks for and also amps for a longer battery life.

You may have a product that works, but by claiming that most the common knowledge on DC-DC are myth is a big reach.

Ctek, Redarc, Sterling, Votronic and a lot of the bigger brands around the globe can't all be wrong

I can't claim that i know all, and i don't, you may have a degree in electrical engineering for all i know.


All the best

[drivesafe]

I don’t know what are you trying to push here or if you’re selling or advertise your product.

Transporter, the brand I was talking about is the Sterling Power products. Sterling are the worlds leader in DC/DC products and have a huge range of them.

And Sterling are rated as the worlds leader in this field by just about every major magazine in this field, in Europe and North America. The other brands simply play catchup.

I do NOT sell them so I can post up unbiased details about any DC/DC device.

As for knowledge about alternators. I have been working in this industry for nearly 40 years, designing and manufacturing electrical and electronic products, used in this field and for a number of years I was also a partner in an auto electrical service.

So I have gained some relevant knowledge about alternators over the years.

[drivesafe]

There are websites out there that talk about limited lifespan of alternators with accelerated bush wear and failure, alternators aren't designed to run at full load 24/7, they have a duty cycle like every other accessories.

There are also vehicles that have problems where they burnout alternators even though they have no additional loads being placed on the alternator.


Both Land Rover and Toyota have a problem with a number of their V8 engine’s alternators having short lifespans. Their burnouts are caused because the alternators were placed in an area that gets poor airflow and even with no additional loads, the alternators still burnout.


The problem is so commonplace with the Toyotas that there is a repair kit available for rebuilding the alternator when it burns out. But this has nothing to do with running an alternator at full output capacity and it's lifespan.

I looked at DC-DC, due to the fact, i also wanted control of the amps put into the battery, a lot of batteries recommend max 20% charge of the battery capacity.

Old STANDBY type AGMs had a 20% limiting charge rate but most STANDBY type AGMs today have at least a 35% charge limit. But this is more to do with selecting the correct battery for the job intended. Automotive grade AGMs do not suffer from this problem, and is the type you should be using where they are being located close to the alternator ( close by cable length ).

I appreciate that you system charges faster, but i'll prefer to keep my battery within the recommended voltage that the battery asks for and also amps for a longer battery life.

I have not mentioned my products and have no intentions of doing so, but if you know my products, then you will also know my products replace the equivalent amount of used battery capacity quicker than any DC/DC device can and but are far gentler on the battery than any DC/DC device.

You may have a product that works, but by claiming that most the common knowledge on DC-DC are myth is a big reach.

My argument is not based on how DC/DC devices actually work, my argument is about the MYTHICAL ADVERTISING they use to promote and sell DC/DC devices.

[Transporter]

I have been working in this industry for nearly 40 years, designing and manufacturing electrical and electronic products, used in this field and for a number of years I was also a partner in an auto electrical service.

So I have gained some relevant knowledge about alternators over the years.

Me too.

[jonathan_k]

Hi folks and before you go fitting any form of DC/DC device, you should do a lot more research into what is available.

Even with EURO6 alternator operations, with STOP/START, you can get MUCH better auxiliary battery charging results by NOT using a DC/DC device.

I am not a sponsor on this site so I will not spam it, but do your research and you will find, if you do a fair bit of city driving, you can actually improve fuel consumption if you fit the correct type of isolator.

Whereas, fitting a DC/DC device may not only increase your fuel consumption, but it WILL take up to 4x as long to recharge a low auxiliary battery compared to what your alternator can do when connected directly ( via and isolator ) to your auxiliary battery.

Perhaps we can rescue this thread!

drivesafe, you're obviously passionate about this topic. Can you give a relative and constructive recommendation for a common dual battery setup for a Transporter owner? You can see that we're regularly mounting batteries under the front seats (less than 3m cable run). Single battery 90-135AH. The T6 owners have stop/start but most of us don't. If you're not comfortable mentioning your product, just say "Product X"?

Edit: Also please mention your battery recommendation!

It's hard to be deeply knowledgeable about more than a few subjects, so most of us do our best by processing the best information we can find.

[drivesafe]

Hi Jonathan, I am only too happy to try and be of some assistance for those wanting to set up a dual battery system, but as I have posted, I am not a sponsor on this thread, so I have no intentions of spamming the site.


I will start by following up on your request for battery recommendations.


First off, as may have already become obvious from my earlier posts, you can’t really just pick any battery and job done.


To set up properly, where you get the best from a dual battery system, the battery type needs to be selected to best suit your needs/requirements.


For example, the first question is, how often do you drive your T5/T6.


Is it your everyday vehicle, if so, then any battery type will be fine.


But here, some types of batteries will offer benefits that others don’t. Benefits like speed of recharging. This can be very important if you only do a lot of short drives.


Is your vehicle only used on weekends, and if so how long would you drive it for, when you do drive it.


Is your vehicle parked up for weeks at a time, and if so how long would you drive it for, when you do drive it.


In all of the above use types, when you do go on a trip, how much reliance do you put on your batteries.


Do you simple move from powered site to powered site and only use your battery to maintain a fridge while you do your tourist bit, between powered sites.


Or do you sit in one place, off the grid, for days or weeks at a time.


All these questions should to be considered before any suggestions of what might be the best battery for a given use.


If anyone wants to post up their uses, based on above, or any other types of use, please do so and I will try to help to sort out which battery might be the best for your particular use.

[Markee]

Drivesafe. I'm after an auxiliary battery that will be used in a car that is driven everyday as a work vehicle, then on the weekends and holidays it is used for camping trip on sites without power available for days at a time.
I would like it to power a fridge, some basic LED lighting and down the track an inverter to charge my work tool batteries and small batteries, like phones, while on camping holidays.
It must be able to receive charge multiple ways. ie. alternator, solar, 240v.
It also must fit on/in the factory battery tray under a T5.2 front passenger bench seat.
I will be using a Ctek D250S charger.

What battery would you recommend?

[John Deere]

With the info from Bryn I think the $450 VW option is pretty decent.