Rear Power Socket Panel Voltmeter

**p38arover** · 17th January 2016, 02:39 PM

The meter in the P38A monitors the second battery which is mounted in the spare wheel well directly below the meter.

C00P · 17th January 2016, 06:10 PM

These are the devices I had in mind for accurate battery state measurement:
Balmar Smartgauge Battery Monitor
Expensive at $295.

However, this website also has a comparison of Amp-hour counters with this type of battery state meter, and dismisses Amp-hour counters as being of no use to monitor battery state. Points out that they have their uses, but that monitoring battery state isn't one of them. See here:
SmartGauge Electronics - SmartGauge compared to Amp Hours Counters

So, the question is: Does $295 make sense when I want to monitor a bank consisting of two 120Ah batteries costing about $300 each.If the monitor helps me to extend the life of the batteries by a year or two, then it would be worthwhile, and I only have to buy it once.
Cheers

Coop

**Oztourer** · 17th January 2016, 08:54 PM

So, the question is: Does $295 make sense when I want to monitor a bank consisting of two 120Ah batteries costing about $300 each.If the monitor helps me to extend the life of the batteries by a year or two, then it would be worthwhile, and I only have to buy it once.
Cheers

Coop

I think that battery longevity is maximised by proper charging. A good quality charger would be more beneficial than an expensive monitor which is the route I opted for. I was just interested to know the state of discharge of my aux batt from time to time as I'm running a 12v fridge for the first time in anger and don't want my beers to get warm

.

DiscoMick · 17th January 2016, 09:01 PM

Really can't see why you would spend $295 on a battery monitor when you can buy them for $30 or so.

Sent from my GT-P5210 using AULRO mobile app

**Toxic_Avenger** · 17th January 2016, 09:20 PM

I've got my eyes on some state of charge monitor. Good units are not cheap, but then again, you always get what you pay for when you buy measurement instruments (Learnt that the hard way when I bought some plastic vernier calipers from super cheap

)

One one extreme there is the simple volt meter, be it the multimeter in the tool box, or something more permanent as was pictured below.
Then there is the hall effect and shunt jobs which measure instantaneous draw and some units can even use information you enter regarding your battery bank to determine remaining Amp Hour rating, or a 'time to empty' value.
Some might argue that measuring what's left is pointless, but then again, having a vehicle that is flat on all batteries, and unable to be restarted to re-charge said batteries is also pointless.

I've used blue sea systems stuff extensively in my build, and it's good quality gear, and has a wide range of products to suit.
They have a new for 2016 product which is a small cigarette socket voltmeter which is pretty trick. Would be an easy install into any off-the-shelf socket panel you can get...

C00P · 17th January 2016, 10:48 PM

[QUOTE=DiscoMick;2480104]Really can't see why you would spend $295 on a battery monitor when you can buy them for $30 or so.

Because the ones you can buy for $30 or so provide approximate measurements that can readily become more erroneous and can apparently be out by as much as 30% (or more). So instead of discharging your battery pack to (say) 70% you could drop it to about 50% and thereby shorten it's life.
But I agree, if you are only considering a single auxilliary battery in your 4WD then the expensive unit would be overkill, and not be cost-effective. In my case I am looking at a battery bank in a large caravan where the cost of replacing the batteries is quite high, and the more expensive unit might be worth it. But I'm still researching as these are pretty new devices which apparently only came onto the market in 2014.
Cheers

Coop

**Eevo** · 18th January 2016, 01:59 AM

If you can afford $300 on a battery monitor.... You might as well just buy another battery...

**Toxic_Avenger** · 18th January 2016, 05:55 AM

That's one way to look at it eevo, but on the other hand, the high end stuff is not commonplace on a 2-battery system, but more likely to be on a bank of batteries containing 8 or 10, where the cost of replacement is high. Large motor homes, big boats etc. Cheap insurance in those instances.

**justinc** · 18th January 2016, 06:55 AM

Untitled Document

They have a few options aswell however website is undergoing work so can't see the product pic.

There is also stuff like this;

POWER PANEL SOCKET SUITS NISSAN GU PATROL ENGEL WAECO MERIT HELLA CIGA OUTLET - Baintech

Also;

http://www.batteriesdirect.com.au/sh...FQsjvQodJcwH7g

Also I think Tim at Traxide was working on something similar a while back? Tim?

JC

**LRD414** · 9th August 2016, 04:23 PM

This is what I have done in the D4, some of which would be applicable to other models.

A simple voltmeter with a switch to allow selection between cranking battery or aux battery or turned off.

Here's a wiring schematic. I spliced into the aux battery feed "upstream" of the ABG-25.
This will allow me to read the aux battery voltage even when it is lower than 11.6V and the ABG-25 has activated (cut-out).
And also to monitor as voltage comes back up because the ABG-25 cuts back in at 12.5V

One major consideration was being able to read the voltage without waking up all the vehicle systems, which happens on door opening.
This location was simple to wire and install but is also easy to read from the outside.
The little push-out trim panel seemed an obvious location when I had these things in mind.

I got into the habit of checking voltage first thing every morning before opening car on our recent long trip but around the city I just leave it off.

I know voltage alone is not SoC but it's a good guide for a lightly loaded battery using Tim's chart:

Cheers,
Scott

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