12 Volt Monitor, Anyone ever use this?

[Dreamscape]

Knowledge is (DC) Power!"  With a TriMetric 2020 battery system monitor, you can literally count the exact Amp Hours discharged from your battery bank.  This is the most accurate way to continuously monitor the state of discharge of any RV deep cycle battery.  Know exactly when to run the Genny and when to stop.  Works great with solar too.  Great for Boon Dockers!

Go to www.bestconverter.com
The website has lots of electrical stuff.

Has anyone ever used this, I thought it was pretty neat.

Happy Trails,

Paul

Dreamscape

[rv_safetyman]

Paul, I studied various meters with this kind of function.  Everything I read suggested that the TriMetric 2020 is a great system.  I just received mine and will be installing it before the next trip.

I ordered mine from altenergystore.com.  They seemed to have the best price.

Gumpy has one in his bus and he thinks it is great.

As most folks who have studied batteries know, there is no way to check state-of-charge except with a hydrometer, or with these kinds of monitors that measure the cumulative flow of current (in and out) as a function of time.

Voltage is only an indicator of state-of-charge *IF* the batteries have not had any charge or discharge over a fairly lengthy period (several hours as I recall).  Indeed, using just voltage as a measure is very misleading.

[Dreamscape]

rv safetyman,

I just checked the site you mentioned, lots of great stuff here also.

What tips do have for this type of installation and why.

I think that monitoring the battery conditions are very important.

Do you use this just for the house batts?

Paul

[Sean]

I have a similar product, the Xantrex Link-10 (since replaced by the newer "Xantrex Battery Monitor," but new Link-10s are still widely available).  Does the same thing, but is more widely discounted.

I wouldn't be without one or the other.

Be advised, for either of these to work right, you will need to know very precisely the capacity of your battery bank in amp-hours, and the Peukert Exponent for your particular batteries.

-Sean

[ChuckMC9]

The 2020 is on my list, and the price Jim found is a little better than others out there.

Just be sure to get the right shunt. I read the specs awhile back and noticed that the shunt the 2020 needs is different than some of the others. I can't remember what mv it is right now, but they'll tell ya. There's a good description of how it works on Bogart's site if I remember right.

I *still* want one with seperate displays though!!! Grrrr.

[Dreamscape]

Did you guys use a circuit breaker and the fuse they reccomend?
I read the description on the alternative energy site, real good information on how it works. Taken from Bogart.
What location did you, or are going to, mount the monitor?

Paul

[JackConrad]

Be advised, for either of these to work right, you will need to know very precisely the capacity of your battery bank in amp-hours, and the Peukert Exponent for your particular batteries.

Sean,
   I know the amp hour capacity of my 8  6 volt golf cart batteries, but what is this Peukert Exponent?

[Dreamscape]

Go here http://www.smartgauge.co.uk/peukert2.html

Hope this helps. I need to try and understand it also.

Paul

[Dreamscape]

After reading the description on Peukert Exponent I feel like I don't know much more than before  .

Guess that's why I am not an electrical or mathematical engineer  .

I guess it is all about sizing your banks to have enough power with a method of checking the discharged capacity on your batteries.

Just wish it was simple enough to understand for the everyday joe.

Paul

[Sean]

OK, don't get wrapped around the axle about the Peukert number.

Without going into the mathematical or electro-chemical details, the simplified explanation is that batteries are sensitive not only to the amount of energy withdrawn (in watt-hours), but also the rate at which that energy is withdrawn.  What Peukert showed was that if you draw, say, ten amps from a battery for two hours, you will "use up" more of the battery capacity than if you draw four amps from the same battery for five hours, even though both of these values figure out to 20 amp-hours (or 240 watt-hours, for a 12-volt battery).

Peukert came up with a mathematical formula to express the real amount of battery depletion, accounting for this rate-based difference.  That formula involves an exponent which is specific to each battery.

There are two ways to figure "Peukert's Exponent" for your particular batteries.  One is to consult the manufacturer, who ought to know.  It is a function of battery chemistry and plate construction, and it is one of the things manufacturers are trying to control when they design a battery.  Most, but not all, manufacturers will simply provide you with the number.

The other way to do it is to solve the mathematical equation, starting with either measurements of depletion, or with the manufacturer's capacity rating at various rates.  By this I mean that some manufacturers will publish that a battery is rated for 200 amp-hours at a 10-hour rate, and 220 amp-hours at a 20-hour rate (my batteries are rated this way).  The apparent difference in capacity is attributable to Peukert's effect.  (Incidentally, the industry norm for house battery capacity is to use the 20-hour rate, but, when comparing batteries, make sure you are looking at the same rate number for each brand, as some publish 10-hour rates, and some publish longer rates.)  There are various Peukert-Exponent calculators around the 'net -- you plug in some numbers, and a web page spits out the exponent.

These battery gauges need to have some idea of the Peukert exponent for your batteries, or else they will read "high" after a period of heavy use.

Hope this makes sense.

-Sean

[rv_safetyman]

Paul (and others), I will use the TriMetric to monitor the house batteries only.  That is the only real concern. 

Concerning the start batteries, recall that you can use voltage as a reasonable state-of-charge if the batteries have not be charged or discharged for a couple of hours.  That kind of defines our start batteries.  After we park, we are not using or charging the start batteries (maybe a little discharge for a clock or radio or something like that), so the voltage is a reasonable indicator of the state-of-charge.  The link below is a pretty good article about state-of-charge and how to measure it and include a table that give percent of charge vs "resting" voltage:

http://www.otherpower.com/otherpower_battery_metering.html

I have debated where to mount the unit.  I have a kind of neat power panel that has all kinds of gauges and switches located in the mid bulkhead in the kitchen area.  Problem is that I am out of space. 

I was going to put a house volt meter in the driver area.  Now that I have the TriMetric, I am going to mount it in the overhead just right of the driver.  That way I can see the gauge while driving (I hope) and it will be fairly easy to get to when we are parked.

Concerning the Peukert Exponent, I am using Exide Golf Cart batteries.  I contacted Exide and they are sending me the information for all of the GC batteries (they make at least three).  After I digest that information, I will try to post some additional information.

[pvcces]

So far as I could tell, the main differences between Trojan's T-105, T-125 and T-145 are the Peukert exponent and the price.

As you increase the size of your battery bank in any particular use, the effect of the Peukert exponent is diminished. This means that your batteries produce more amp hours before needing a recharge. This is why using a small battery bank causes so much dissatisfaction in use.

For what it's worth.

Tom Caffrey

[Sean]

Regarding mounting location, I have mine in my driver area.  That's because I want to be able to monitor how much current is going into the batteries from the engine alternator while under way, and to know before I stop for the night if I will need to run the generator, find external power, etc..

It's a pain in the butt, while parked, to go downstairs to the cockpit to read the gauge, but it would be even harder to go upstairs while driving!

-Sean