Battery Monitoring

[Davidceder]

Does anyone have a simple solution to monitoring battery voltage on an ongoing basis. maybe a simple meter directly from the battery terminals into the rig. I know I can go out with a meter but that is a PIA. Looking for some type of LCD display I can run into the rig. Something better than 4 idiot lights..

Thanks

[BigTJohn]

Don't have it on me but at West Marine I purchased a battery monitor and it shows how much volts/amps/% left, etc. it was on sale, small, about $100 new for $60. I'll try to remember to get info/pic soon.

[fonzie]

Here is a thread about battery meter...

http://www.forestriverforums.com/for...ter-59645.html

[camaraderie]

David...if you are looking to figure out how "much" battery you have left WHILE you are using your coach...then you need a monitor ...not a voltmeter which can ONLY tell you that either you are charging or dead. Any other readout is ficticious. ALWAYS.
What you really want to know is:
1. How many of my 214 amp hours in my battery bank are left.
2. At the rate I'm using amps...how long do I have before I need to recharge?
3. How many amp hours does my heater use? My coffeepot? How many AH's do I use when I think I'm not using any??!!
4. Are my batteries FULLY 100% recharged.

If you don't boondock...you don't need em... if you do...the the Trimetic or the Victron will save your batteries and pay for themselves.

[JCamper]

Along those lines does anyone know how many volts I should see coming into my batts while plugged into shore power? My meter shows 13.37 but that seems low.
I can no longer run my Maxx Air fan, 4 lights and a 600 watt inverter at the same time. I have 2 12v #24 batts and last trip the gens had to run an inordinate amount of time to recharge them. I suspect dying batteries but these are only 2 years old. (But are the dealer batts) any suggestions??

[bubbles]

I made and installed a small panel at the entrance control panel It's just a voltmeter but it will show if the battery is being charged and will show battery voltage which can be used to identify if charge is needed. I just paralled off the awning switch +12 volt power wire (it's fused directly off the battery) and used a momentary push button switch for the meter. I think it will come in handy someday troubleshooting the electrical system. Any way it can't hurt.

[fonzie]

Originally Posted by JCamper

Along those lines does anyone know how many volts I should see coming into my batts while plugged into shore power? My meter shows 13.37 but that seems low.
I can no longer run my Maxx Air fan, 4 lights and a 600 watt inverter at the same time. I have 2 12v #24 batts and last trip the gens had to run an inordinate amount of time to recharge them. I suspect dying batteries but these are only 2 years old. (But are the dealer batts) any suggestions??

Mine charges at 13.5 volts....

[Herk7769]

I use a Trimetric TM-2025RV battery monitoring system that displays voltage to the tenth of a volt and also displays Percent of Charge remaining as well as actual current in and out of the battery.

See my review here:

http://www.forestriverforums.com/for...itor-5436.html

Trimetric Battery Monitoring System

[camaraderie]

Originally Posted by JCamper

Along those lines does anyone know how many volts I should see coming into my batts while plugged into shore power? My meter shows 13.37 but that seems low.
I can no longer run my Maxx Air fan, 4 lights and a 600 watt inverter at the same time. I have 2 12v #24 batts and last trip the gens had to run an inordinate amount of time to recharge them. I suspect dying batteries but these are only 2 years old. (But are the dealer batts) any suggestions??

JCamp... you are seeing 13.3 as a Float voltage which means the batts have received 90+ to 100% of their charge. If you had just used them for a night...you should see a recharge Bulk voltage in the neighborhood of 14.5Volts for a few hours before it ramps down to float voltage.
You have a fan that takes maybe 4 amps at medium speed...a few bulbs and an inverter on standby which only uses a few amps...if your batts are going flat with that in short order they are really in bad shape.
Suggest you have murdered them by abuse since you don't appear to know much about them or have any way to monitor them.
Group 24 batts have about 75 amp hours each when new...a pair will have 150 amp hours OF WHICH YOU CAN USE 75 before recharging. If you don't know what you are using... and how much is left in your batts ... you end up killing them prematurely even if you're good about watering them.

Step one is to fully charge the batteries then pull the plug. Get a cheap turkey baster hydrometer at AutoZone and take a reading of EACH cell in EACH battery. My guess is you'll fine dead ones or close to dead...but at least you'll have the turkey baster for the future.
Assuming dead batts...IF you have room...get a couple of golf cart batteries at Sams or Costco...that will take you up to 220 amp hours or so which will give you 110AH before you need to recharge.
If you can't fit the golf cart batts...then get TRUE deep cycle 12V batteries ..not dual use... and get them in the largest sizes you can squeeze in...group 27 or 31 will give you slightly more or less than 200 amp hours compared to the group 24's ... but there's nothing wrong with 24's except your need to recharge more often.
Good luck!

If you want to avoid this situation in another 2 years... get one of these...
BMV-600S series - Victron Energy
or these:
Battery-Monitor-System

They will pay for themselves easily in battery life.

[JCamper]

Anyone help explain to me the difference between 20 amp hour rate and the Amp Hour?

Looking at 2 deep cycle 12v batteries...

Battery 1
20 Amp Hour Rate 140Ah
Amp Hour 66Ah
Res Cap 140 Min

Battery 2
20 Amp Hour Rate 68Ah
No Amp Hour listed
Res Cap 135 Min

Whats the difference here?
Comparing the Optima YellowTop Deep Cycle (Battery 1) to the Sears Die Hard Platinum Deep Cycle (Battery2)

I'm not ready to go 6v yet so please don't go down that road. Any other 12v batteries out there that anyone can recommend?

Should mention I only have room for 2 group 24

[fonzie]

Originally Posted by JCamper

Anyone help explain to me the difference between 20 amp hour rate and the Amp Hour?

Looking at 2 deep cycle 12v batteries...

Battery 1
20 Amp Hour Rate 140Ah
Amp Hour 66Ah
Res Cap 140 Min

Battery 2
20 Amp Hour Rate 68Ah
No Amp Hour listed
Res Cap 135 Min

Whats the difference here?
Comparing the Optima YellowTop Deep Cycle (Battery 1) to the Sears Die Hard Platinum Deep Cycle (Battery2)

I'm not ready to go 6v yet so please don't go down that road. Any other 12v batteries out there that anyone can recommend?

Should mention I only have room for 2 group 24

This site should provide you with information you are looking for to make decision.

Frequently Asked Questions (FAQ) - DC Battery Specialists

[Witch Doctor]

Originally Posted by JCamper

Anyone help explain to me the difference between 20 amp hour rate and the Amp Hour?

Looking at 2 deep cycle 12v batteries...

Battery 1
20 Amp Hour Rate 140Ah
Amp Hour 66Ah
Res Cap 140 Min

Battery 2
20 Amp Hour Rate 68Ah
No Amp Hour listed
Res Cap 135 Min

Whats the difference here?
Comparing the Optima YellowTop Deep Cycle (Battery 1) to the Sears Die Hard Platinum Deep Cycle (Battery2)

I'm not ready to go 6v yet so please don't go down that road. Any other 12v batteries out there that anyone can recommend?

Should mention I only have room for 2 group 24

Costco has some good ones under there brand, The best is trojan deep cycle are very popular. I have 2 interstate deep cycle (so called) 27 group but I do not boondock, I'm past that stage. I just do not want to buy a generator or solar system. Just match them......

[Herk7769]

Originally Posted by JCamper

Anyone help explain to me the difference between 20 amp hour rate and the Amp Hour?

Looking at 2 deep cycle 12v batteries...

Battery 1
20 Amp Hour Rate 140Ah
Amp Hour 66Ah
Res Cap 140 Min

Battery 2
20 Amp Hour Rate 68Ah
No Amp Hour listed
Res Cap 135 Min

Whats the difference here?
Comparing the Optima YellowTop Deep Cycle (Battery 1) to the Sears Die Hard Platinum Deep Cycle (Battery2)

I'm not ready to go 6v yet so please don't go down that road. Any other 12v batteries out there that anyone can recommend?

Should mention I only have room for 2 group 24

Your yellow top rating are incorrect:

http://d26maze4pb6to3.cloudfront.net...pecs_Sheet.pdf

Yellow tops are not true deep cycle batteries; they are "Marine" type dual purpose batteries and the 20 amp hour (AH rating is defined as the number of hours the battery will last when NEW with a 20 amp continuous draw).

Yellow tops are rated at 75 AH (about par with dual purpose batteries - 60-80 AH).

In fact your Sears battery rating is also not correct:

http://www.sears.com/diehard-marine-...3&blockType=G3

The sears Marine battery is rated at 80AH. This is about how the matter stacks up. AGM type batteries of the same class have less AH than their flooded cousins, but there are advantages that "make up" for the lost capacity (like being maintenance free).

FYI - The Platinum series are starting batteries. That is why the 34M you were looking at is twice as big and yet has only 68AH of storage capacity.

http://www.sears.com/diehard-platinu...7&blockType=G7

[camaraderie]

Originally Posted by JCamper

Anyone help explain to me the difference between 20 amp hour rate and the Amp Hour?

Looking at 2 deep cycle 12v batteries...

Battery 1
20 Amp Hour Rate 140Ah
Amp Hour 66Ah
Res Cap 140 Min

Battery 2
20 Amp Hour Rate 68Ah
No Amp Hour listed
Res Cap 135 Min

Whats the difference here?
Comparing the Optima YellowTop Deep Cycle (Battery 1) to the Sears Die Hard Platinum Deep Cycle (Battery2)

I'm not ready to go 6v yet so please don't go down that road. Any other 12v batteries out there that anyone can recommend?

Should mention I only have room for 2 group 24

OK...first...the 20 amp hour rating is what designates a DEEP CYCLE battery. It tells your how many amps of current the battery can support for 20 hours. So a 20 hours rating of 100 amp hours equals 5 amps of current continuous for 20 hours OK?? So MORE amp hours at the 20 hour specification is GOOD GOOD !! If a battery says DEEP CYCLE but does not provide a 20 amp hour rating...you can be sure it is a DUAL PURPOSE BATTERY. STAY AWAY.

NEXT...you need to provide links for the batteries you are looking at. I find NO Group 24 yellow top battery, AND all the yellow top batteries are DUAL PURPOSE. I don't know where those specs come from but they sure as hell ain't yellow top specs for a group 24 DEEP CYCLE. I WOULD believe 65-70 hours at the 20 hour spec from an Optima group 24

Next is the Die Hard Platinum which is a completely different type of battery built by Odyssey for Sears...it is an AGM design but also a TPPL (Thin Plate Pure Lead) which can perform both as an exceptional deep cycle battery AND as a starting battery. Since Sears carries it for cars, they don't really focus on deep cycle use. Unfortunately, I can find NO Sears die hard platinum in size Group 24. Your specs look like those for their group 34. Link to a 24 if you have one but since Odyssey doesn't make one...I'm thinking Sears doesn't have one.

Now...as to recommendations...It looks like you've settled on AGM Group 24 as your choice. Here's the Trojan 24AGM spec sheet:
http://www.trojanbattery.com/pdf/dat...ata_Sheets.pdf
76 amp hours and superior construction to the average.

Also East Penn makes some fine AGM's http://www.dekabatteries.com/assets/...rdeepcycle.pdf
Their brand is DEKA but it may also be found under other store brand names. 79 amp hours. Tri-State Battery Warehouse : 8A24M Deka Intimidator High Performance AGM Battery [8A24M] - $165.00

Either one would be good choices...and they also sell TRUE deep cycle wet cells in group 24 size if you decide to save some bucks.

Hope this helps!

[camaraderie]

Originally Posted by Herk7769

and the 20 amp hour (AH rating is defined as the number of hours the battery will last when NEW with a 20 amp continuous draw).

Herk...think you misquoted the 20 amp rating vs. the 20amphour rating.
The latter is what we are concerned with in COMPARING deep cycles.
It represents the STEADY CURRENT AMPS that can be used before a battery is fully depleted at 20 hours of use.
So a group 24 ...78 amp hour battery can supply 78/20 or a little less than 4 amps of current steadily for 20 hours.
A 255 amp hour battery (8D!) can supply 255/20 or 12.5 amps steadily for 20 hours. You can run 3 times the stuff for 20 hours.

[Herk7769]

You are much more knowledgeable about this than me.

The way I understood it is that AH are a product of the amps demanded and the hours it can deliver at that amperage.

So the 20 AH rate is the number of hours it can deliver a continuous 20 amps.

20 amps times 5 hours = 100 AH. OR 5 amps for 20 hours = 100 AH.

Is this "potatoes/potatoes" or am I missing something?

I believed the "generally accepted" (by battery manufacturers) amperage to rate capacity is the 20 amp demand. RC in minutes is rated at 25 amp demand for starting batteries.

What am I doing wrong?

[Herk7769]

Originally Posted by camaraderie

Herk...think you misquoted the 20 amp rating vs. the 20amphour rating.
The latter is what we are concerned with in COMPARING deep cycles.
It represents the STEADY CURRENT AMPS that can be used before a battery is fully depleted at 20 hours of use.
So a group 24 ...78 amp hour battery can supply 78/20 or a little less than 4 amps of current steadily for 20 hours.
A 255 amp hour battery (8D!) can supply 255/20 or 12.5 amps steadily for 20 hours. You can run 3 times the stuff for 20 hours.

I am having difficulty squaring this with the graph in my post that came from a textbook on solar/wind energy battery systems.

[Herk7769]

OK, I think you are right and I was incorrect. (or we were saying the same thing differently).

The graph shows a 20 HOUR rated 100 AH battery. It is 100% of rating at 5 amps. The capacity to deliver plummets as amperage required increases above 5 amps.

It make more sense to me know, thank you.

So using the graph, a single 100 AH battery delivering 20 amps has an effective capacity of 62 AH (from the graph); so will that 20 amp load continuous would kill the battery in 3.1 hours (62/20) or in 62% of 20 hours (12.4 hours)?

[camaraderie]

LOL...actually I was getting set to PASTE that graph in to help explain it!! It quite nicely reinforces what I said. So lets review what I said the 20 hour measurement actually measures: The maximum total amount of STEADY current that the battery can produce for 20 hours before going flat. Notice NO mention of 20 amps of current.

OK now lets look at your graph which is a 20 hour rated group 31 battery rated at 100 amp hours.


Now look at the left side where it says AH capacity and see what VERTICAL line is crossed ... read down that line and find the continuous amp draw required to get 100 amp hours in 20 hours. It is 5.
So 5 amps current run for 20 hours gives us a capacity of 100amp hours at the 20 hour rating.
Now just for fun...lets look across at the result from drawing 20 amps...and you can see you would get just 63 amphours total capacity before the battery was flat. So you can also figure out that 20 amps of current only allowed the battery to LAST a little over 3 hours at 20 amps per hour.

The 20 amp hour rating method is of little value in and of itself since we don't run steady state loads in real life. But it does give a meaningful comparison about the current loads a battery will support for 20 hours before going flat. You cannot compare ANY other amp load rating with the 20 hour rating as you can see from your battery curve...batt's can last longer with lower loads..and a lot shorter with higher loads.

Whenever you see a battery amp hour rating at the 20 hour spec...simply divide by 20 to see the maximum continuous amps you can run for 20 hours staight when new.

BTW...your pdf attachment verifies this with their analysis of a 70 amp hour battery...quoting:

"For example, an average automotive battery might have a capacity of about 70 amp-hours, specified at a current of 3.5 amps. This means that the amount of time this battery could continuously supply a current of 3.5 amps to a load would be 20 hours (70 amp-hours / 3.5 amps)."
So 20 hours = 70 AMP HOURS/3.5 amps.
Transposing we get 20 hours x 3.5 amps = 70 amp hours.

Notice no mention of 20 amps in the purple either.

Hope that makes it more clear...

EDIT...was typing this as you wrote you last reply...you figured it out without me but maybe this post will help others.

[camaraderie]

BTW...the difference in real life in amp hours delivered in total is based on the various current draws you use at different times in your coach and where they fall on that curve. Dr. Peukert figured that out and Peukerts LAW is built into both the Trimetric and Victron battery monitors we've been talking about recently...so they actually compensate for actual use patterns to tell you what % you have left AND how long the batts will last at CURRENT current use! Pretty cool that they do that!