Thread: Discovery 2 Dual Battery

Originally Posted by Tins

You can make statistics say anything you want. ICE cars of course have fuel that burns. That's what combustion means, after all. EVs are not supposed to burn, but they do, and you can't put the bloody fires out.

MotorTrend has skin in the game. You may want to broaden your reading.

I'd suggest that ICE vehicles are not meant to burn either.

Data is data. No matter what the source.
There was a Tesla Semi fire a few weeks ago. made the news. First one. How many diesel semis catch fire each day in the US?

Originally Posted by Bohica

I'd suggest that ICE vehicles are not meant to burn either.

Data is data. No matter what the source.
There was a Tesla Semi fire a few weeks ago. made the news. First one. How many diesel semis catch fire each day in the US?

Data can be manipulated, Julian. That's obvious, happens every day. That's the purpose of the MSM, of which MotorTrend is a part. What is the ratio between diesel and electric prime movers? What caused the fire? Do diesel PMs catch fire when simply parked? Do they catch fire if the operator is stupid enough to refuel them? When they burn, can the fire service extinguish them? Does the fire service then have to monitor them, and follow them to their grave, do they need to be isolated from everything else for months afterwards? No. Do they have to have special sections set aside for parking, or on ferries? No. Can you say the same about EVs? No.

Have a look at who owns MotorTrend. Check out just where their income is sourced. Nothing to see here?

Originally Posted by drivesafe

Hi mate and this is a touchy subject for anyone who thinks DC/DC devices are the end all.

First off, and I will use a D4 as the example, DC/DC devices are only about 80% efficient and thats as long as the auxiliary battery is not too low and the alternator voltage is high enough.

Whereas, my Traxide isolators are at least 99% efficient regardless of alternator voltage.

The current charge limit of a DC/DC device means it can take as much as 6x as long to replace the same amount of used energy that a Traxide system will replace in a much shorter time.

And this something moist people are unaware of, modern DC/DC devices are, for safety reasons, INPUT current limited. This means as the voltage from the alternator drops, a DC/DC device needs to draw more current from the alternator to maintain the OUTPUT charging current.

But again, as stated, for safety reasons, this INPUT current is now limited and as the alternator voltage drops, the OUTPUT charge current reduces, regardless of whether the auxiliary battery is in a low state of charge or not

So while the DC/DC device may be rated as a 40 amp charger, it is not uncommon for them to be charging at less that 20 amps when used in a vehicle with a SMART alternator, like D4s.


Lot more to it but this is a start.

Yeah that makes sense, thanks mate. I guess I have learnt all my dual battery knowledge from mainstream sources so they're always going to spruke large brands and dc-dc products etc. - I've probably never had an issue with my dc-dc / aux battery charging since I mostly have had solar input backing it up

Originally Posted by reid25

Yeah that makes sense, thanks mate. I guess I have learnt all my dual battery knowledge from mainstream sources so they're always going to spruke large brands and dc-dc products etc. - I've probably never had an issue with my dc-dc / aux battery charging since I mostly have had solar input backing it up

Con't get me wrong, I have never claimed DC/DC setups can't charge batteries, they are just not the only or best way to do it.

Most people get what they pay for when installing a DC/DC setup, but they can usually get a better setup for less money.

Thought this might be of interest. I don't know one way or the other, but I would like to hear Tim's opinion.

<br>

Hi Jay Tee, and I will use how my isolators work to demonstrate how you can get around the charging problem he has.

First and foremost, from the data he supplied in his video, my guess is that his auxiliary battery is badly sulphated.

My reason for this is that the battery went down to as low as 11.80v in a short period of time, when under load. The current load of two fridges would not have been that large. This indicates that the battery was down to around 30 to 40% State of Charge of its “AVAILABLE” capacity.

Then when he went for a drive, the 25 amp DC/DC charger only charged in the Bulk/Absorption cycle for about an hour and then went into Float mode.

This means that it only supplied about 20 amperes of capacity, at best, in that short time before the DC/DC deice determined that the battery was near fully charged.

The auxiliary battery looks like an 80Ah to 100Ah capacity.

I’ll use the 80Ah capacity to demonstrate the problem.

Again based on the data supplied, the battery is so severely sulphated that it has about only 20 to 30% of its original capacity available for use.

He needs to Desulphate the battery before he does anything else, otherwise, it early demise is imminent.

The other solenoid type isolator will not solve his problem but it allow the auxiliary battery to get a bit more of a charge.

This is on a Toyota, which does NOT have a SMART alternator, but if this was in a vehicle with a SMART alternator, the problem would be worse and the solenoid type isolator would not help.

With my Traxide isolators, while you will still get Sulphation happening if you don’t maintain your batteries properly, it does take much linger to occur.

There are a number of reasons for this, but basically you get better performance with a Traxide isolator because it shares the load of two batteries, which means the two batteries will never be as low as a single battery setup, and this means you will recharge the two batteries in a shorter drive time, and because the two batteries are always in a higher state of charge, Shulphation takes much longer to buildup..

Unlike DC/DC devices ad their limited charge current, the Traxide isolators all everything an alternator can turn out too again, recharge the two batteries in a shorter time.

Also note, the guy is using a Deep Cycle battery as the auxiliary battery, but I ALWAYS recommend you use a CRANKING type battery as the auxiliary battery because they are specifically designed to take high currents ( fast charge ) while charging. Because of the design, Deep Cycle batteries actually take much longer to fully charge.

Ahhh, thats the advantage of a Traxide unit over a traditional voltage sensitive relay that isolates when the alternator stops charging.

Originally Posted by drivesafe

Also note, the guy is using a Deep Cycle battery as the auxiliary battery, but I ALWAYS recommend you use a CRANKING type battery as the auxiliary battery because they are specifically designed to take high currents ( fast charge ) while charging. Because of the design, Deep Cycle batteries actually take much longer to fully charge.

Hi Tim,

If you discharge a battery to a low state of charge regularly, what is the difference in life between a deep cycle and cranking battery?

As always, thanks for your input to AULRO.

Tony