Metering/ monitoring

Shadowcatcher

This comes into the how much is enough, more than you really need category. I have a Morningstar SunSaver MPPT controller with the PM-1 meter and shortly a Morningstar SurSine inverter. I have the adapter so that I can hook the controller to the lap top and a digital meter inside the tear to check battery voltage and a fuse buddy that I can substitute for an ATC fuse in line from/to the converters and loads that will read amps or volts (plugs into the VOM).
Other than being a bit more than obsessive will it be of much value to plunk down a couple of hundred dollars for a Trimetric meter in addition to this whole mess?

BB.

Re: Metering/ monitoring

From my point of view--The end result of the entire system should be monitored/operated for the health of the battery bank. A battery monitor with the shunt in the (typically) negative battery lead is the only device that logs what goes into and out of the battery bank.

Measuring Specific Gravity is pretty accurate--but not something you want others to do daily. And cannot be done with sealed batteries (such as AGM). Measuring resting voltage is OK--But most people need to know the state of charge when the bank is under load/charging--when state of charge is not very accurate.

Battery Monitors are also handy for the non-technical (spouse, kids, guests) as the monitor will display the (estimated) battery state of charge from 0-100%. If nothing else, tell them to call you if they see the state of charge fall below 50%.

My analogy is driving a car without a gas gauge. You know the mileage since the last fill up and how many gallons the tank holds. People do that all the time (my fiancée, now wife, came with a Rabbit that had a failed fuel sensor). The battery monitor is the equivalent of a fuel flow/totalizer in the line to the fuel tank. Logs the fuel out and fuel back into the tank. Uses the >14.5 volts for 2 hours (or whatever) to reset back to 100% to allow for errors that creep in.

They are not perfect... However, it can let you know pretty quickly when something goes south (loads left on drawing bank down, somebody using more power than planned, failed parallel string/wiring not accepting current, when to start the genset, etc.) all by looking single handy gauge.

If you run the bank by yourself and like to monitor it closely by watching your Charger's readings, and watch the bank voltage, take/log specific gravity readings every few days, etc... You certainly can and be very successful.

If you are into gadgets--A good Battery Monitor is a pretty nice tool to have.

-Bill

Shadowcatcher

Re: Metering/ monitoring

The system is in a Grasshopper design teardrop trailer 6X10' with a 180W solar panel (takes up half the roof) and a flexible 140W additional panel that can be staked out in the sun with its own controller. The trailer has all LED lights a stereo with Sirius receiver 19" flat screen TV/DVD and satellite receiver both drawing 45W. I will be buying a Morningstar SurSine shortly to power the TV and Sat. The only additional power draws are the water pump and spark ignition for the water heater, two computer case fans and the Eberspacher diesel heater ~1.5A.
The battery is a Lifeline 150AH AGM. The wife can understand, do not let it get below 12.3 V (more than 50% SOC).

BB.

Re: Metering/ monitoring

12.3 volts is even open to confusion... Loads/Charging affect battery voltage, as does bank temperature. In theory, you need to "rest" the battery bank for 3 hours or more before the voltage will "accurately" reflect the state of charge.

Under load (at least for flooded cell batteries), dropping to near 11.5 volts is not the end of the world (don't know for sure about AGMs--perhaps a higher voltage is warranted).

In any case, if you monitor your bank and come up with a don't go under 12.x volts when the TV is turned on--That will probably work OK for you.

Regarding your loads--Do you have an AC/DC AH/WattHour set of daily loads penciled out? If this was 45 watts * 2 (45 watts for TV and 45 watts for Sat Link, etc. plus the rest of the loads)--That is a fair amount of power for this sized system.

You may collect around 30 to 60 AH (360-720 WH) of usable power per day/season/etc. under good conditions (nobody gets a good harvest under cloudy winter skies).

Knowledge about the power into/out of your battery bank is critical for being able to plan/manage your loads (as always, along with conservation of power).

If this is a weekend/few months a year worth of use trailer--I would be tempted to let the battery go well below 50% stage of charge (as long as it is "quickly" recharged the next day or two). Yes, you may only get 500 "deep cycles" out of the battery bank--But if that is 50 cycles per year (i.e., camping every weekend a year), that is still 10 years worth of cycling--And the battery will probably "age out" much faster than that (3-7 years???). Just don't take the battery below ~11.5 volts (or below 20% stage of charge)--That can reverse a "weak" cell and kill it immediately (and trashing the entire battery).

Being able to monitor the current*time directly into/out of the battery bank will give you a much better handle on your loads and planning.

Anyway, my recommendations. I don't get a chance to camp with a trailer/batteries/etc... So, take them with a grain of salt.

-Bill

Shadowcatcher

Re: Metering/ monitoring

I do not have any experience with the system yet as it is just completed (if these things are ever completed). I do appreciate the paradigm shift, battery life balance.

icarus

Re: Metering/ monitoring

As usual, Bill has it absolutely dialed. I would simply get the Trimetric, and learn to use it.

Tony

Shadowcatcher

Re: Metering/ monitoring

Ok ok I will get something. One of the problems I am bumping up against is some place to put which ever. I am just plain running out of room to put it in the galley area where all of the electrical stuff ends up and mostly starts. If the meter is inside it means you have to crawl inside. One alternative to the Trimetric is a Victron BMV-600S, the big advantage is it is only 2.44" in diameter.

westbranch

Re: Metering/ monitoring

If you just want some simplified info there is the Midnite BCM http://www.midnitesolar.com/productPhoto.php?product_ID=254&productCatName=Accessories&productCat_ID=5
or the 'Watts Up' http://www.rc-electronics-usa.com/electrical-test-equipment.html or the 'Doc Wattson'

ps the BCM is good for the wife and others who just want to look and see

Shadowcatcher

Re: Metering/ monitoring

I installed the Victron battery monitor and did the smoke test today, fortunately none escaped so I do not have to stuff any of it back in. I have to say I really like the way it works and the simplicity of set up. Basically all I had to do was input the battery amp hour and it was up and running. I particularly like the % DOD.
Also smoke tested the just installed Morningstar SureSine. I ended up using a 30A DPDT switch for shore power or inverter.