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john61ct · 11-04-2018, 07:33

By converter you mean in the USian RV industry sense, AKA battery charger?

eBay is a great place to scan for visual matches of what you want, red vs blue LEDs, matching your hole size etc.

And so much cheaper than "marine" sources you can buy spares for when they break.

Or use it just to define exactly what you want then contact Defender etc see if they can supply.

Just know you're getting an ammeter and volts display only, not what we DC geeks would call a proper Battery Monitor.

john61ct · 11-04-2018, 07:34

IMO your overall DC electric system design could be improved, and that single batt either eliminated or dedicated to cranking only.

john61ct · 11-04-2018, 07:38

Quote:

Originally Posted by Pelagic

charged by the 24/12v convertor from house, or when the Gen is running from its alternator.

Aha, sorry converter in the proper sense.

I retract my most recent comment, but only because I now understand your system's overall design less.

(Roseanne Roseannadanna*voice) Never mind!

**Dockhead** · 11-04-2018, 07:52

Quote:

Originally Posted by Pelagic

Hi Dockhead, to clarify it is not the SOC of my 24v start I want to monitor but the 12v Instruments/Generator Start Battery.
This single AGM battery sits in the pilot house under the port console in an electrical locker and is only charged by the 24/12v convertor from house, or when the Gen is running from its alternator.

Attachment 167903

When I bought the boat, each voltage had a really nice old German smart meter 12 & 24v but their LED readouts faded.
Attachment 167904

Now with my Electrical upgrades to Victron Systems and Solar, and removal of antiquated gauges like shaft generator a new console still has a blank space for the 12v Monitoring.
Attachment 167906 Attachment 167907 Attachment 167908

Monitoring this single 12v "Radio Battery" is important as it has a fuzzy charging source.

So I am still looking for a smart gauge solution that fits the new console.
Buying a 2nd Victron monitor seems excessive, so looking for other thoughts

OK, I got it now.

The separate radio battery is good practice -- that's required by GMDSS. I was seriously tempted to do it myself when I redid my electronics but finally decided I had enough complication without it. In my case it would have had the additional benefit of eliminating several droppers, since a lot of my electronics need 12v and my system is 24v.

I think a $10 volt/amp meter would be fine for this -- you're not drawing down the battery like a house bank, you're just trying to be sure that the charger is keeping up, right? If the system volts are ok, then everything else is ok, provided you disconnect the charger from time to time and check the battery capacity.

A SmartGauge or Victron would be fine as well, but definitely overkill.

Here's what I have:

The small one on the bottom is DC volts and amps (amps not hooked up because the alternator is out for repair). You can get bigger ones, and in different sizes.

If you've got power going in equal to what is going out, then the battery won't be in use -- it's state of charge should stay at 100%. You can verify this with voltage -- if the system voltage stays at the B2B charger set point after a long time, then the batt is 100% and not doing anything.

The important thing in this kind of installation is to do regular capacity tests -- this setup is more like a UPS than it is like a house battery bank.

You don't need to do the full-on pull down to 0 test -- just put a known load on it and let it run down to some set voltage, then let the battery rest, and then test open circuit voltage so you can see where that got you. If you design this to take the batt down to 50% or so, then you will have a good useful capacity test. Do it every month or two and you will be fine.

I like your setup. I think the separate radio battery is a very good thing.

john61ct · 11-04-2018, 07:54

But it's also cranking over a big engine?

**Dockhead** · 11-04-2018, 07:57

Quote:

Originally Posted by john61ct

But it's also cranking over a big engine?

Is it?

I must have missed that. Didn't he call it the "radio battery"?

If that's true, then indeed, I would separate engine start from electronics for sure. Easy enough to do, and will allow him to use a pure starting battery for the motor.

Pelagic · 11-04-2018, 09:20

Quote:

Originally Posted by Dockhead

Is it?

I must have missed that. Didn't he call it the "radio battery"?

If that's true, then indeed, I would separate engine start from electronics for sure. Easy enough to do, and will allow him to use a pure starting battery for the motor.

Yes it is both. A dedicated 230Ah AGM dual purpose battery for a few small 12v electronic loads and a cranker for the Gen.
http://www.trojanbattery.com/product/8d-agm/
It bothered me at first, that the radio side was not independent.
I wondered why they didn't just put a 24v starter on the Northern Lights Generator and pull from the much closer Start Batteries for the main engine.

But in practice, this 8d battery spins the generator like nothing and has no effect on the 12v electronics, when cranking.

Assuming I had a starting problem with the Generator , the battery is continually being recharged by the 24v house bank, so the "Radio" side is not compromised.

So I have just kept it as original, with just an improvement on battery technology.
The simple dual volt/amp gauge is what I need to find for the console.

wsmurdoch · 11-04-2018, 13:26

Quote:

Originally Posted by john61ct

eBay is a great place to scan for visual matches of what you want, red vs blue LEDs, matching your hole size etc.

And so much cheaper than "marine" sources you can buy spares for when they break.

Or use it just to define exactly what you want then contact Defender etc see if they can supply.

Just know you're getting an ammeter and volts display only, not what we DC geeks would call a proper Battery Monitor.

After being mentioned in an older thread, I have bought three of these amp/volt/watt/amp-hour meters. While others have had problems with them; I have not. They are what they are - coulomb counters. Be aware that there are several different kinds varying in their specifications. If you buy one, read and choose carefully to get the one you need.

https://www.ebay.com/itm/New-DC-Prog...item2a6a5788b4

**Dockhead** · 11-04-2018, 13:38

Quote:

Originally Posted by wsmurdoch

After being mentioned in an older thread, I have bought three of these amp/volt/watt/amp-hour meters. While others have had problems with them; I have not. They are what they are - coulomb counters. Be aware that there are several different kinds varying in their specifications. If you buy one, read and choose carefully to get the one you need.

https://www.ebay.com/itm/New-DC-Prog...item2a6a5788b4

A very nice looking device. What is funny is that the display is much better designed than the Victron version of this I used to have, which costs about 8x as much

Nothing wrong with this kind of device so long as you don't use it like a gas gauge -- take the SOC output with a grain, nay a box of salt, but work the volts and amps, which are so nicely displayed here.

Pelagic · 11-04-2018, 14:28

My problem with ordering these Amp/volt displays sight unseen is that I have no idea how robust the connections are..especially for Amps!

This review shows the difference in quality

https://youtu.be/T4b1pg3nc50

wsmurdoch · 11-04-2018, 14:56

Quote:

Originally Posted by Pelagic

My problem with ordering these Amp/volt displays sight unseen is that I have no idea how robust the connections are..especially for Amps!

On the external shunt model, the shunt is a bit light to my eye, but that may be okay if you already have a shunt in your system. The internal shunt model that I have is fine for 30A max for my smaller sailboat. The third one I have is installed in a homemade automatic shutoff, fixed load, battery capacity tester.

$40 is not a lot to put at risk....

Oceanride007 · 11-04-2018, 16:22

If you do buy those clever devices on Ebay or whatever, in my experience, they do not count in both directions, the wires are often without terminals connectors and I found too much hassle (used aligator jumpers instead, very dodgy, occasional smoke, get one with proper connectors) also remember that by the time you buy enough equipment to count consumption and makeup, it can be a false economy (more money can be spent than what could be saved), they are fragile, also even with accurate information on my consumption I ordered panels one size too small, not allowing for increased consumption and I was in a perpetually sunny area.

At the moment I'm logging SG level of my FLA batterys, and getting a handle on the mystery and surprisingly long effect of "surface charge", its effect seems to be minimal early morning, great time to check VOC (Open Circuit Voltage after a quiescent time, say 10 minutes and before Solar kicks in) VOC will advise you if your BM is telling fibs.

After a rather dull period of two weeks my SG was telling me I'm down to 50% SOC, my 712 BMV was rather too optimistic, it is rather a challenge to fit accurate info into the BMV, thats the present challenge.

PS. When I say effect of Surface charge, I'm talking about the difference in VOC and the voltage that would be expected by a given battery's Specific Gravity (SG).

john61ct · 11-04-2018, 17:13

Quote:

Originally Posted by wsmurdoch

On the external shunt model, the shunt is a bit light to my eye, but that may be okay if you already have a shunt in your system. The internal shunt model that I have is fine for 30A max for my smaller sailboat. The third one I have is installed in a homemade automatic shutoff, fixed load, battery capacity tester.

$40 is not a lot to put at risk....

Shunts are best bought together with the display, unless you know what you're doing.

Some meters can calibrate for different mV types.

Big a55 capacity shunts are less accurate.

Mount well and cover protected.

john61ct · 11-04-2018, 17:16

Specific gravity needs isolated rest period just like voltage.

Neither indicates SoC accurately without long-term calibration and familiarity.

I think OP is especially motivated to identify units that fit nicely into the existing console, rather than these purely functional distinctions.