Opinions about this battery monitor

[Dave78Chief]

I see no problem with using that on the Solar path. The reason to use a much larger shunt on the normal battery path is to account for using the isolator relay for engine start assistance (up to 400 amps on a gasser; 800-1200 amps on a diesel). You do not want the shunt to fail when your using AUX start. Like the relay itself, they have continious amp and instantanious amp ratings.

All of these type of meters (ones I listed and the one you listed) are a actually programable voltmeters. Resistor and pin selection on rear of meter determine scale and type of measurement. The ebay lister is simply preconfiguring the device for the type of application being advertized.

Be sure to specify you want the Power Supply 1 option.

Todays newer systems use hall effect current monitors (non-invasive). They are not inserted into the circuit like a shunt is. The aftermarket designers like this one simply have not developed those type of inexpensive setups for generic applications like this yet.

Dave

[Dunner]

The lister says that no notification is needed for option 1, standard power supply.

Would you know how to convert one from amp meter to volt amp meter?

I could alway use some jumper cables, if the shunt should fail.

[Dave78Chief]

First, a little lesson in what is going on.
An ampmeter is actually a millivoltmeter being used to measure the voltage drop across a milliohm resistance (called a shunt).


For the one you linked to, they are using 75milli-volt shunt which is being read by a milli-volt meter with a ± 100milli-volt range setting (200milli-volt total range). The scale on the meter itself is just adjusted to ± 50 amps. Same as selecting the milli-volt scale on a voltmeter. The resistance of the shunt would be .0015 ohms (1.5 milliohms).

Essentially, you put together a circuit that looks simular to the one on this page: Make your own multimeter : DC CIRCUITS except you use the one leg for the voltage scale (R multiplier) you want.

In the 60's, cars had dash amp meters that had the alternator/generator output routed through them. The shunt was built into the meter itself. Many a person has been stranded with a dead battery because the shunt in the meter failed. In the 70's, they migrated to the shunt style version where the shunt is actually nothing more than a a piece of wire tapped at 2 points. This appraoch was used up through the 90's until they started replacing the amp meter with a voltmeter. As one gets more familure with an RV system, they learn the relationships between current, voltage, amp-hours, and various other tidbits of battery system lingo. Voltage and current measurment is at the root of all of it. You can have a nice 14.1 VDC bulk charge level but the device may only be putting out milli-amps in current ergo it is not really doing anything.

Please note that the meter suggestions I made previously were intended to provide the least compilicated implementation method. Those with an electronics background can do more difficult things but I felt the KISS principle was the best approach for most people.

There are hundreds of digital panel meters available via ebay (http://www.ebay.com/sch/i.html?_trkp...&_sop=15&_sc=1)
all manner of sizes, colors, ranges and interfacing methods.

Dave

[Dave78Chief]

Dunner,
Looked around a little more on ebay and if you want to stay with 50 amps then:
20V/50ADC BLUE LED DIGITAL PANEL AMPS METER & VOLTMETER | eBay

50 amp Shunt (from same seller): 50A DC CURRENT SHUNT RESISTOR for DIGITAL & ANALOG GAUGE AMP METER AMMETER RV | eBay

The voltmeter listing says it is wired such that the same battery being measured can be used as the power source. I would confirm that with him though.

Dave

[Dunner]

I saw those also. Like I said, I already have the built-in chassis and house battery display in my MH, so I really only need the ampmeter.

A little background. While in the Army(66-69), I was at a 5th echelon depot and was also on the mobile calibration team. I repaired and calibrated electronic test equipment. After the Army, I did the same at Motorola.

I've built analog amp meters to test small batteries and also other electronic devices. I like to joke that I have forgotten more about electronics than most people will ever know.

I didn't mean convert the amp meter to a volt meter. I meant buy the amp meter and option it to be an amp and volt meter. I put a Bogart Trimetric system in the 5er I just sold. It had a 100 amp shunt and never gave me a problem. It was powered by the house batteries it monitored. Thanks for the link, I bookmarked it.

[Dave78Chief]

LOL - point well taken. I still perform a 40 hr technical job related to miltary electronics (Sonar systems). If my information only servered as a reminder of the how then it accomplished the intent. More to the point though, most of these meters are of a generic programmable design. They can reconfigured to measure anywhere from millivolts to 1000's of volts. Some even include the reconfiguration data sheets with them. There are hundreds of them on ebay because some people know that many have no clue about how to change them so they do the configuration and sell the end customized product.

Dave

[Dunner]

My guess is that most of the sellers have no idea of what an electron is.

Thanks for the refresher course.

[camper8251]

As others have said, the charge wizard is for monitoring the status of your charger / Inverter. It also allows you to change modes manually. I bought one, but then I am a techno geek and like to know what it is doing. Plus I like the fact of being able to put it in boost mode manually to top off my battery bank.

[Dunner]

Will the Charge Wizard also work on a 55A Parallax 7455 Converter/Charger?

[Dave78Chief]

Sorry no. The Progressive Dynamics Charge Wizard was only made to work with the PD9100 series converter. The PD9100 out of the box is only a 13.6VDC coverter/power supply. The Charge Wizard option was an enhancement that converted it to a 3 stage charger (early days of 3-stage evolution before it became the defacto standard). The PD9200 series is 3-stage out of the box and does not "require" a seperate device for 3-stage operation. The PD9200 series "pendent" that goes with it is nothing more than a state monitor that also allows you to manual change charging state (Bulk, Absorbtion, or float).

The 7455 Magnetek 7455 Ferro-Resonate Converter was was made many moons ago (mostly 70's era). I have assembled information about it and the technology here: Daves Place - RV Electrical Systems

Sorry but you would have to upgrade to a more modern converter/charger to obtain 3-stage charging capability

Dave

[Dunner]

Dave,

I have a BatteryMinder Model 12248, 2-4-8 charger/maintainer that I leave on during the off season. Between trips, I leave the fridge on with shore power and the BM on the 4 amp desulfating mode. Will it cook the batteries by leaving them on shore power for 2-4 weeks at a time?

[Dave78Chief]

The BatteryMinder alone would not harm the batteries though if they are flooded wet cells you should check the water level monthly. I have never used one of these so I can only speak to what I see in the manual.

I leave the fridge on with shore power ...

RV Propane type fridge that uses 12VDC or household AC style fridge?

First, the 7455 running will affect the BatteryMinder. BatteryMinder sees the 7455 13.8VDC voltage rather than the actual battery voltage. That would be 13.6VDC for the 7455T. A Ferro-resonate converter/charger does not use a transfer relay and is always connected to the battery so it can charge it. Same type connection used modern day converters. http://www.parallaxpower.com/775_900/Ferro_FAQ.pdf

If the fridge is an AC home style, then disconnect (turn AC breaker OFF?) the 7455 and just let the BatteryMinder hum away happily.

RV Fridge Propane/AC - Not sure what you are doing here.
Running in Propane mode? Just unplug 7455 as the BatteryMinder should be able keep up with the Fridge 12VDC needs.
Running in AC mode: Still should be able to shutdown 7455 as fridge uses AC for heating element and DC for control like in Propane. Again BatteryMinder should be able keep up with the Fridge 12VDC needs.

I didn't dig through all of the BatteryMinder information but I did see where for batteries of 30AH or greater use the 8A mode. If using it to keep up with the Fridge 12VDC then you would want that mode.

One last note, I assume the BatteryMinder will automatically revert to either Bulk or Absorbtion mode if battery SOC is reduced to loads (i.e. Fridge) connnected to the battery.

Make sense?

BTW - If you ever replace the 7455 with modern 3-stage charger like the PD9260, then you would no longer need the BatteryMinder as all that functionality is built in. You only have to be careful about Converter/charger selction if you are using AGM or Gel Cell batteries becasue of the charging voltages.

Dave

[Dunner]

Thanks for digging into all this good info, Dave.

Dometic Propane/AC RV style fridge. I see what you are saying. Unplug the 7455 and power the fridge with shore power and use the BM on 8A to replace what the control board drains from the batteries. I was using the 4A setting so as not to over-charge the flooded cells.

I just bought the BM a couple months ago, so I'm in no hurry to replace the converter.

[wa8yxm]

While I did not follow the link to the recommended controller/display, nor have I researched that model.. I will say this:

The proper controller will make a big difference in how quickly your batteries charge under SOLAR. and how long they last before you need to buy new batteries.

Again.. I know nothing about the recommended controller.