Thread: Beware Charging Dual Battery in D4.

No one's trying to "shut you up" - at least I hope not!!

However, you're skirting my point - yes it is often hard, time-consuming and even impractical to reference every point made in a discussion. Especially on points that reflect a "basic truth", as you point out. But stating something like "most manufacturers recommend" or "you can purchase item X for $Y" are statements that CAN and if asked, SHOULD be supported.

I see you've gone some way to acknowledge that in your last post to Drivesafe, so perhaps we can now move on?

Cheers,

Gordon

Originally Posted by gghaggis

(however, I'd agree that perhaps Drivesafe could tone down his language a little? Please??).

Hi Gordon and you're right, but I just get fed up with people who go out of the way to post up bogus info, and for the life of me I can’t understand their reasoning.

Hi again Peter, I use a number of different batteries for experimenting and testing. Like a couple of Federal 6v 220 Ah batteries, a couple of Exide N200, Optimas, Amp-Tech and so on.

I also use the same battery as yours, the MRV48 ( 60Ah ) and an MRV70 ( 105Ah ) allrounder and find these batteries perform perfectly in both testing situations and in use in a D3, I have yet to carry out extensive testing in a 3Lt D4.

You on the other hand are already set up to do some experimenting both with the DC-DC device and without the device. Are you interested in trying some different set ups to see which achieves what, based on your Allrounders?

Originally Posted by gghaggis

No one's trying to "shut you up" - at least I hope not!!

However, you're skirting my point - yes it is often hard, time-consuming and even impractical to reference every point made in a discussion. Especially on points that reflect a "basic truth", as you point out. But stating something like "most manufacturers recommend" or "you can purchase item X for $Y" are statements that CAN and if asked, SHOULD be supported.

I see you've gone some way to acknowledge that in your last post to Drivesafe, so perhaps we can now move on?

Cheers,

Gordon

While I disagree with you about no one trying to shut me up, I will take it as read.

I don't think I was skirting your point - for the sake of peace I didn't point out that in my previous post on the subject, I provided (amongst other things) a graph from Fullriver batteries that proved precisely my point that you can't satisfactorily charge batteries form a low voltage. This proof was completely ignored and I was still accused of talking crap.


It gives me little incentive to go to a lot of effort to provide proof.

But I take your advice, and I will move on.

Originally Posted by Wilbur

I don't think I was skirting your point - for the sake of peace I didn't point out that in my previous post on the subject, I provided (amongst other things) a graph from Fullriver batteries that proved precisely my point that you can't satisfactorily charge batteries form a low voltage. This proof was completely ignored and I was still accused of talking crap.

Wilbur, your will say anything that pops into your head.

That graph was was NOT ignored, it was discredited, and not by me but by someone who actually uses Fullriver batteries.

Try reading all the replies again!

Drivesafe
I can understand you getting frustrated and your frustration is not just with Wilbur but with a general idea that many think is true; that one needs a complicated system for the D3/4.

We know your system works well and there have been no issues with it. I have one but do not have a large power useage.

However there are other systems which others have fitted with no issues.

I bought yours due to it having few reported issues and any there were you sorted by informing on the correct wiring.

But I would add there are many who have discovered problems with systems by businesses that are used to fitting them on old Tojos etc.

You both have a point that the D3/4 works differently.

Maybe a good question would be: "Is there any reason why this (insert details here) set up would not work?"

Hi CaverD3 and I agree with you, but what is needed is some HONEST independent testing and comparing.

No one is prepared to do that.

A number of 4x4 mag articles have appeared over the last couple of years but they have been so advertiser oriented that they where a total waste of time and one was so obviously weighted in favour of the big advertises that many who read the article not only commented on how unfairly biased it was but they gave the magazine credibility a big thumbs down.

As for these DC-DC devices and your comments, I have NEVER stated that these devices are not capable of fully charging batteries.

The problem arises when you read the misleading advertising used to promote these devices.

For example, one brand has a graph that shows their device can fully charge two 100Ah batteries from 75% SoC in ( from memory ) 150 minutes while, according to their graph, an alternator will take 180 minutes.

Now the info is probably correct, but where the deception comes into it is the fact that the graph started with batteries at 75% SoC.

First off, why would anyone have two 100Ah batteries if they never intend to discharge them below 75%. It would be far cheaper and more realistic to use just one battery and discharge it down to 50% SoC.

But these little anomalies don’t fit into the advertising hype.

If the graph had started with the batteries at just 5% lower, at 70%, it would show a break even situation. Not good for sales.

If the graph started with batteries at 50%, a far more realistic house battery use level, it would show the alternator fully charging the two batteries in more than an hour quicker than their DC-DC device could do. Definitely not likely to improve sales of their device.

Note, the alternator set up would be using a conventional battery isolator, if you work the same graph using one of my SC80 isolators, you would probably get at least a 2 hour advantage over their Dc-DC device.

CaverD3, this is what I mean by the need for honest independent testing.

It's called marketing Drivesafe.

This is why forums are useful in that you can at least get an unbiased feel for what works and what doesn't.

The bigger adverisers get better treatment in the mags look at what Overlander did to my suspension system.

Originally Posted by drivesafe

You on the other hand are already set up to do some experimenting both with the DC-DC device and without the device. Are you interested in trying some different set ups to see which achieves what, based on your Allrounders?

Hi Drivesafe,

I've had enough experimenting in getting to the answer I have. I'm not willing to risk doing more to my car. I suspect though that experimenting would show:

• SC80 charges faster than a 25AMP DC/DC converter (assuming low Soc)
• DC/DC converter takes a CA/CA Battery to a fuller charge (as it can get upto 15.2V)
• DC/DC converter is less disruptive because it does exactly the same thing regardless of the state of the second set of batteries. I dont know if disruptive causes issues... enough working SC80s around seem to suggest not.
• It is essential that either approach connects negatives to vehicle Earth (not negative battery post) so that the D4 electronics can detect the current draw. I believe that when I had it connected to the negative battery post it resulted in the vehicle running on approx 12.6v (and not charging my second batteries).

So thanks for the offer Drivesafe but I'm going to enjoy my time going bush instead

Peter

** all claims above are the sole opinion of the writter and are not supported by any scientific or independent testing. Any claims for damages may be directed to our lawyers.... that should about cover me I hope