battery discharge and inside trailer monitors

[parfsten]

Hi there,
I think this must be a dumb question...I am feeling really dumb on this one

I believe a battery (2 6 volt batteries) should not be discharged below 11.5, right?
How do the charge level register on the "4 lights" monitor above sink and the solar charging gauge under the dinette table register the charge level?

Is it an absolute or relative measure? Does 1 light mean 1/3 total of battery left or 1/3 from 11.5 to 12.7? Does this question even make sense

And the solar charging gauge under the dinette... as the % of charge drops is it the percentage of charge from 11.5 to 12.7 or the absolute battery charge left...

Ouch - I have a headache... Time for a walk on the beach.

Thanks for clearing this up for me!

[tdf-texas]

The charge lights on the KIB panel that come with the Escape are pretty much useless for determining the battery charge level. The solar charging gauge is about the same thing. They questionably measure the battery voltage - which unless the battery has been at rest for a couple of hours - ie not charging or discharging, doesn't indicate battery charge condition.

Those of us that want to monitor the battery charge accurately have installed a battery monitor that uses a current shunt to measure the power going into and out of the battery.

I use a Victron 700: https://www.amazon.com/Victron-BMV-7...34671256&psc=1

Others have used the Trimetric: https://www.amazon.com/TriMetric-TM-.../dp/B06XRJNY76

Both are good monitors that will accurately tell you how much charge your battery has.

[Vermilye]

As Tom (tdf-texas) said, both the % read out and particularly the LEDs on Escape's status panel are pretty near useless. I've had the GoPower solar controller readout telling me I was at 100% when the batteries were down by 24 amp hours. If you do lots of dry camping, I suggest getting a real battery monitor that uses a shunt to measure actual amperage in & out of the batteries.

The Victron that Tom mentioned is a good choice since it provides bluetooth connections to a phone; I have the Trimetric. In both cases, the % readout on the battery monitor is far more accurate, and either can keep an account on amp hours in & out of the batteries.

One last comment - 11.5 volts is really too low for continual practice. That is less than 20% capacity remaining in the batteries, and going that low repeatedly will result on a much shorter battery life. Not going below 12V, which is about 1/2 the battery capacity is the recommended low battery voltage point.

The problem is getting an accurate voltage measurement requires no load on the batteries, and no charging source. You also have to burn off the surface charge. While it can be done, it is easier to use a battery monitor. Even then, while the % reading will be more accurate, the voltage measurement won't be most of the time because the solar controller, or converter if plugged in, will be showing charging voltage, not battery voltage.

[Hilola]

Lots of good info here and a handy, printable voltage chart towards the middle of this page:

The 12volt Side of Life (Part 1)

[John in Santa Cruz]

Those Victrons are nice, albeit pricy but they do require some significant wiring, putting the amp shunt in series with the battery and so forth.

the poor mans version is this:
https://www.amazon.com/gp/product/B000EVWDU0/

just plug it into a cigar lighter... now, you do need to understand the voltages under different conditions... if there's a heavy load on the batttery, it reads low, if its being charged it reads high, so shut everything off for a half hour or so before you read the charge state for most accuracy... for standard wet cells, at normal room temp,

12.7V - 100% charged
12.4V - 75% charged
12.2V - 50% charged - this is my normal lower limit.
12.0V - 25% charge - this is my try-to-never-ever-go-below limit
11.8V - flat, don't go here!


when your charger is running, the voltage will be 1.0 to 1.5 v higher than the battery charge state, until the battery is fully charged and your charger reverts to maintenance mode, then it will be around 13.2-13.4V.

[alanmalk]

Originally Posted by John in Santa Cruz

...
12.7V - 100% charged
12.4V - 75% charged
12.2V - 50% charged - this is my normal lower limit.
12.0V - 25% charge - this is my try-to-never-ever-go-below limit
11.8V - flat, don't go here!
...

One more data point - that I just found about today after buying a new car battery.

10.0V - your warranty is void.

--
Alan

[fudge_brownie]

The poor mans version that Jon mentions is not bad. I have had one and am now using a Trimetric. They are night and day for installation and configuration.

One consideration for the cigarette model, mine was an Equus brand but identical, is the need to have a 12 volt socket in a convienent location that makes it easy to see the readings.

[Vermilye]

For those that are willing to do a custom case or install, this eBay battery monitor might do the trick. One advantage is it uses a Hall Effect sensor rather than a shunt. Easier to install. If you have an inverter, the 100 amp upper limit might be a problem.

[parfsten]

Thanks everyone! This has really cleared the issue up for me.

[steve dunham]

If you go to LHC ( Little House Customs ) you can purchase a self adhesive label that lists battery voltage / % charged . I have one on the battery door of my Casita for easy reference when checking my battery with a DC voltmeter . Cost is about a $1
They also make a sticker for the fresh water tank that converts tank level to gallons

[Mike Lewis]

I have the Tri-Metric monitor but would like to have Bluetooth capability. Do you think the shunt that I have installed now would work with another brand? Or is there a newer model Tri-Metric that has Bluetooth that would work with the shunt that I have? I think that I saw one mentioned once.

[tdf-texas]

Originally Posted by Mike Lewis

I have the Tri-Metric monitor but would like to have Bluetooth capability. Do you think the shunt that I have installed now would work with another brand?

Not likely but replacing the shunt with another is a simple job. The Victron BMV712 has bluetooth built in and comes with a shunt.

Originally Posted by Mike Lewis

Or is there a newer model Tri-Metric that has Bluetooth that would work with the shunt that I have?

No. Bluetooth was one of the reasons I chose the Victron over the Trimetric. The other was the peukert calc.

[padlin]

Originally Posted by Mike Lewis

Do you think the shunt that I have installed now would work with another brand? Or is there a newer model Tri-Metric that has Bluetooth that would work with the shunt that I have? I think that I saw one mentioned once.

A shunt is a shunt, Victron however has a small board on theirs that allows the RJ connector from the monitor to attach directly to it as opposed to the 4 wire on the Trimetric. You'd have to cut off the connector and strip back the wires and directly connect them. May have to change the scale on the monitor depending on the shunt you have now, I'm guessing that you can do such.

From what I read, the BMV-712 ships with their 50/500 shunt standard so it's a moot point, might as well replace the one you have with the Victrons.

As mentioned, Bogart does not have a bluetooth option but you could call Ralph and ask about it (tech support).

[John in Santa Cruz]

Originally Posted by padlin

A shunt is a shunt, Victron however ....

well, shunts can be different resistances, resulting in different readout scales with a given meter. for instance, if a shunt is 0.01 ohms, then 100 amps would read as 1 volt differential.

[padlin]

I see no reference to the ohm value of a shunt for either Victron or Bogart (Trimetrics), just the 50mV/500A type of designation. According to AMsolar, the Victron ships with the 50/500, for our battery banks, one would use the same value for the Trimetric, which they also sell, again, no ohm spec.

[John in Santa Cruz]

well, if its 50mV at 500 A, then its 0.05V / 500A == 0.0001 ohms

[tdf-texas]

Sorry guys! The point I was trying to make was it seems that each monitor manufacturer spec their own shunt - some may be interchangeable but not worth the effort if they include a shunt with the monitor such as Victron.

If Mike wants a monitor that has bluetooth, then Victron is the likely choice. Since Victron comes with it's own shunt, there's no need to cut, splice, etc. and maybe not have the accuracy that the supplied shunt provides.

Plus, Mike could sell his Trimetric with shunt complete to someone and recoup some cash.

[rubicon327]

Originally Posted by fudge_brownie

The poor mans version that Jon mentions is not bad. I have had one and am now using a Trimetric. They are night and day for installation and configuration.

One consideration for the cigarette model, mine was an Equus brand but identical, is the need to have a 12 volt socket in a convienent location that makes it easy to see the readings.

This is probably a middle ground between the expensive, complex units and the 12V outlet plug-in type. Works well for us. It has a built in shunt.

http://www.escapeforum.org/forums/f3...tml#post165556