Battery Monitoring

[bob7794]

My TT didn't have a 12v outlet so I installed one to plug my CPAP machine into when we dry camp. I also this Equus Innova 3721 Battery Charging System Monitor - Walmart.com from Walmart to monitor the condition of my batteries.

[Herk7769]

So, a single 100 AH battery will only last 3 hours or so with a 20 amp draw. Makes a lot more sense now when folks talk about adding inverters and running all night on one battery.

A 400 watt inverter at full rated load needs 33.3 battery amps continuously. Not gonna make it through the night on one battery!

The good news (if there is any) is the capacity hit is less when the same demand is spread over additional batteries.

[camaraderie]

@Bob7794....
How many amps does your CPAP draw?...should say on the power supply label or in the specs in the instruction manual.
What size is your battery bank...or what size and how many batteries do your have?
The walmart voltmeter does NOT tell you about the condition of your batteries except when not in use after some hours of rest. The good portable CPAP 12V machines will still draw around 4 amps or about 40 amphours per night. This can vary wildly between machines however...so it is important to know YOUR draw and how long your batteries can support this draw before they need recharging. You sound like your batteries are fine supporting your use of the unit...but you may be inadvertently and significantly shortening the battery life you should get with proper charging/discharging.
A Victron or Trimetric true monitor would be a good addition ...but failing that...if you can tell me the amp draw and battery's...I can give you a pretty close estimate.

@Herk...exactly right!

[Herk7769]

Curious; so I just checked the specs on the DW's PD Dialysis Cycler and CPAP machine.

Cycler - 600 Watts Peak - 100 Watts Average (9 hours run time per night)

CPAP - VPAP II - 200 Watts w/o Humidifier (Have an "un-powered" humidifier Respironics REMstar Passover Humidifier for camping)

The cycler's fluid heater use can be "moderated" by setting up the machine while on generator so the fluid can be pre-warmed before switching to battery for the night. That way the cycler will be in the "100 watt" mode all night. (whoot)

With 150AH bank (2 - DC-24 DeKa Marine DP) and a 1000 Watt inverter, I might be OK with no heater use.

Looks like the Deka's will be moved to the basement to augment the sump pumps and a couple of true Deep Cycles are in my future.
Come ON, Christmas!

The math (Camaradie Please check the logic!) ...

25 amps required for 300 watts - shared between 2 75 AH batteries

12.5 amps per battery required for 9 hours = 112.5 amps per battery per night.

Capacity reduction 30% (from chart) so 52AH available per battery
So, (If I understand what Camaradie is saying correctly), the battery should deliver 52 amps over a period of 20 hours or 104 amps over a period of 10 hours (114.4 amps over 9 hours).

With my two batteries it looks like a close run thing.
3 batteries or just 2 bigger ones?

Decisions; Decisions...

[JCamper]

Sorry it took me a day to get all of your responses.

So I'm looking at this...
Sears.com

It's not labled as a group 24 but the size specs make it fit in my boxes.
My concern now is that this is not a deep cycle???

Would I be better off going with a Trojan
Trojan 24-AGM 12V 80Ah AGM Battery

Now for my confession... I bought the Die Hards yesterday but can return them!

The Trojan website offers a group 24 in a flooded
http://www.trojanbattery.com/product/scs150/
AGM
http://www.trojanbattery.com/product/24-agm/
Gel
http://www.trojanbattery.com/product/24-gel/

What is the consensus? I don't boondock much. 3 nights max, so I'm more concerned about the power versus the duration.

[Herk7769]

I would return them.
68AH fully charged is horrible for the listed weight.

[camaraderie]

Herk...I'm not familiar with all the equipment so you have to keep it simple for me!
Are you saying that all the equipment draws an average of 300 watts...and that it draws those watts for 9 hours...a total of 2700 watt hours??
Since Watts=V x amps.... 2700/12= 225 amp hours used per night... or 112.5 amp hours per battery per night...so it seems we agree on that.

Now the Dekas have a 75 amp hour rating at 20 hours and so are capable of delivering 3.75 amps for that long.
Delivering 112.5 amps over 9 hours requires a current of 12.5 amps ...and with losses to inverter and capacity from new...lets just call it 4 times the rated 20 hour current.
This is ANALOGOUS to the battery chart for the Group 31 100 amp battery rated for 5 amps and asked to deliver 4x that...at 20 amps. So the LOSS of capacity is about 38% (so we depart a bit there)...and 62% of the original 75 amp hours is about 47 amp hours of total amps delivered by each battery when asked to deliver a continuous 14amp current.
So...each battery will die... after 47/14 hours...or 3 hours and 20 minutes.
Since each battery is only being asked to shoulder 1/2 the actual 300 watt load, both batteries will die 3.3 hours into the night.
Note that word DIE.
Let's also remember that we can't run down the batteries to 0% but must stop to recharge at 50% ...so we're really talking about 1.7 hours till the batteries need to be recharged.
So...I don't think we agree on the math beyond the point where we agree that your batteires need to supply 112.5 amps per night each. If I understand your situation correctly then the Group 24's are WOEFULLY inadequate since they will only supply about 20% of your demand before needing to be recharged...40% or so if you want to kill them.

DOES THIS MAKE SENSE TO YOU OR AM I MISUNDERSTANDING SOMETHING??

Now, since we DO agree on the nature of the total nightly demand...let's start to put together an adequate battery bank.
If you have a 225 amp hours need nightly...that means you must at least have DOUBLE that amount IN your battery capacity since you can only discharge 50% before needing to recharge.
So 450 amp hours is dead minimum... that would be a minimum of 4 Golf Carts or a couple of 8D's ...or 5 group 27's , or 6 of your present group 24's to run your equipment.
Since the 450 amphour bank is capable of supplying 22.5 amps continuously...well in excess of the 14 amps or so that you will be using....we have no concerns for Mr. Peukert and his curve but note that at a 14 amp rate...you've got a bit of a cushion OVER 450amphours which will be useful as your batteries age.

FINALLY... all of this is based on you needing a continuous 300watts to run your equipment for 9 hours each night. To me...THIS 300 watts seems quite high but without knowledge of the equipment, all I can say is double check how you arrived at this before making any battery decisions.

[Herk7769]

I followed you right to -> I can't do it.

In fact, since I am seriously weight restricted, 6 batteries (300 pounds or so) is completely out of the question. Bummer. (But you saved me a small fortune).

[JCamper]

Originally Posted by Herk7769

I would return them.
68AH fully charged is horrible for the listed weight.

Hey Herk researching these out comparing the Die Hard Platinum to the Trojan AGM
Die Hard 53lbs 68 Amp Hours @ 20
Trojan 54 lbs 76 Amp Hours @20
The big difference for me is the CCA where the Die Hard pulls away at 860 the Trojan is 500. I'm NOT using the batts to start anything but I do want to reiterate that I'm needing more power at a shorter interval. At night I run a 600w inverter 2 TV's and some lights for a couple of hours before bed. (like 2-3 hours)
I run my gens enought during the day to recharge the batts, so my hitch in all this is that a Trojan while it would certainly last longer than the Die Hard, wouldn't power the stuff I want to run. Am I understanding it all wrong?
Thanks in advance for your help on this!

[camaraderie]

Originally Posted by JCamper

Sorry it took me a day to get all of your responses.

So I'm looking at this...
Sears.com

It's not labled as a group 24 but the size specs make it fit in my boxes.
My concern now is that this is not a deep cycle???

Would I be better off going with a Trojan
Trojan 24-AGM 12V 80Ah AGM Battery

Now for my confession... I bought the Die Hards yesterday but can return them!

The Trojan website offers a group 24 in a flooded
SCS150 | Trojan Battery Company
AGM
24-AGM | Trojan Battery Company
Gel
24-GEL | Trojan Battery Company

What is the consensus? I don't boondock much. 3 nights max, so I'm more concerned about the power versus the duration.

JCamper... as I thought...you did not have a Group24.
WHY are you selecting AGM's... what is your reasoning? I can't fathom why you would need them.
Get the Trojan wet cells...and get as many as you can fit. Get as big as you can fit.
Your last comment... "I don't boondock much. 3 nights max" frankly threw me for a loop. With TWO group 24 batteries ...you have 75 amp hours available before you need to recharge. Do you have any idea how many amphours you use when you boondock? Start there... and I think you'll discover you need a lot more than 75 for 3 days. That means more batteries or a generator running a lot.

Here's a list of items and their amp draw. Add a ZERO to any AC appliance amps listed...(12 amps AC = 120amps DC )
Checkoff the items you use...then multiply each item by the number of hours or parts of hours you use them daily. Add it all up to get an anticipated amp hour use per day...and DOUBLE that to figure our the amp hour size of the battery bank you need so you don't destroy your batteries.
RV Converters and Amp Draw - RV Information (RV Maintenance)

[JCamper]

Camaraderie,

When I boondock I run my gens enough during the day to charge the batts back up. But your right AGM's may not be the best bet.

I'm not at my trailer right now, so off the cuff my one TV 50w runs on the 600w inverter, the other 19" is a 12 volt 80w. 4 incandescent lights. I'm only guessing but I'd say at one time I use 300w? Sound right?

[Herk7769]

Originally Posted by JCamper

Hey Herk researching these out comparing the Die Hard Platinum to the Trojan AGM
Die Hard 53lbs 68 Amp Hours @ 20
Trojan 54 lbs 76 Amp Hours @20
The big difference for me is the CCA where the Die Hard pulls away at 860 the Trojan is 500. I'm NOT using the batts to start anything but I do want to reiterate that I'm needing more power at a shorter interval. At night I run a 600w inverter 2 TV's and some lights for a couple of hours before bed. (like 2-3 hours)
I run my gens enought during the day to recharge the batts, so my hitch in all this is that a Trojan while it would certainly last longer than the Die Hard, wouldn't power the stuff I want to run. Am I understanding it all wrong?
Thanks in advance for your help on this!

You are trying to compare apples and oranges. The AGMs have less AH than a comparably sized flooded cell battery and far more expensive.

CCA has no meaning AT ALL when talking about storage capacity unless you are planning on discharging that battery in 30 seconds (what CCA means).

What does CCA mean?

Cold Cranking Amps is a rating used in the battery industry to define a battery's ability to start an engine in cold temperatures. The rating is the number of amps a new, fully charged battery can deliver at 0° Farenheit for 30 seconds, while maintaining a voltage of at least 7.2 volts, for a 12 volt battery. The higher the CCA rating, the greater the starting power of the battery.

AH rating per pound of battery at the lowest cost should be your measure.

Frequently Asked Questions

You say you run the generator to recharge the batteries. Just so you know, you can easily remove more amperage from your battery in far less time than a generator powering your converter can replace by running the generator for DAYS. Your converter is designed to step down the charging rate as the battery is recharged to avoid harming it. It can take over 52 hours to recharge a depleted battery using the converter.

The switch from Bulk to Absorbtion occurs at 50% of battery capacity and the switch from Absorption to Float occurs at 80% of capacity.

[JCamper]

Not trying to cause "ripples" in the water, but here is an article on AGM versus flooded.

Absorbent Glass Mat (AGM) Battery Information - Battery University

I have seen other articles stating the same thing, that an AGM is the best (albeit costly) way to go over a flooded.

In looking at the Trojans I can't fit anything other than their group 24 Gel based on the listed measurments.

I'm not sure what to do now... hang on to my Die Hards?

[camaraderie]

Originally Posted by JCamper

Camaraderie,

When I boondock I run my gens enough during the day to charge the batts back up. But your right AGM's may not be the best bet.

I'm not at my trailer right now, so off the cuff my one TV 50w runs on the 600w inverter, the other 19" is a 12 volt 80w. 4 incandescent lights. I'm only guessing but I'd say at one time I use 300w? Sound right?

I really don't have any idea. Nor do I think you have any idea of whether your batteries are fully charged or not and no idea whether you are murdering them or not by taking them below 50%.
You can either add up the DC loads by figuring them out while you are on the coach....i.e. how BIG is each incandescent... how much DRAW does your inverter use at idle with nothing else on....how much draw does your car radio memory and your propane monitor draw. etc. etc.

The easy alternative...is to buy a very useful AC/DC clamp multimeter for around 50 bucks and clamp your battery wire as you turn things on and off.

Then you'll know what AMPS you use.... and whether you need to add more batteries or more generator time. Is your generator hooked up to a separate battery charger? How many amps is the battery charger you are using??

You can't put MORE than 30 amps an hour INTO the batteries on recharge in bulk mode (assuming 2x group24) and it will take you at least 4 hours of run time to put back 75 amp hours once the charger ramps down to absorb and float mode.

[camaraderie]

Originally Posted by JCamper

Not trying to cause "ripples" in the water, but here is an article on AGM versus flooded.

Absorbent Glass Mat (AGM) Battery Information - Battery University

I have seen other articles stating the same thing, that an AGM is the best (albeit costly) way to go over a flooded.

In looking at the Trojans I can't fit anything other than their group 24 Gel based on the listed measurments.

I'm not sure what to do now... hang on to my Die Hards?

NO...that is simply a DEAD WRONG analysis of the article. Let's look at the + and minus' of AGM based on the article:

Spill-proof through acid encapsulation in matting technology
High specific power, low internal resistance, responsive to load
Up to 5 times faster charge than with flooded technology
Better cycle life than with flooded systems
Water retention (oxygen and hydrogen combine to produce water)
Vibration resistance due to sandwich construction
Stands up well to cold temperature

Limitations

Higher manufacturing cost than flooded (but cheaper than gel)
Sensitive to overcharging (gel has tighter tolerances than AGM)
Capacity has gradual decline (gel has a performance dome)
Low specific energy
Must be stored in charged condition (less critical than flooded)
Not environmentally friendly (has less electrolyte, lead that flooded)

Now lets add negatives....2-3 times the price. Doesn't like HEAT. DOESN'T Like to be continuously left on float. MUST be charged to 100% each time or capacity will be lost. FEWER life cycles than the comparable quality wet cell (Trojan will tell you this on their site and they make and sell both!)

Then lets' review the advantages of AGM as it applies to you.
NO WATERING is a nice benefit.
Spill Proof is of no concern in an upright coach.
Low internal resistance...good for charging IF you have a HUGE charger.
High Current power....good IF you have BIG instantaneous amp loads...you don't.
Better life cycle...an outright falsehood not supported by any battery mfr. ...try to find THAT claim on any battery mfr. site compared to their wet cells. Trojan says the opposite.
Cold temperature performance is better. Do you plan to use the coach in below zero F conditions?
Good vibration resistance...true compared to normal batts...but NOT compared to quality deep cycles like Trojan wet cells.

Don't get me wrong. I lived full time off the grid for 6 years and had an 1100 amp hour AGM bank...because I needed it for instant current drains, had a huge charger (130amps) had an 8kw generator to power the charger and batteries in an inaccessible area for watering with no ventilation.
They were the answer for me.
If you want to buy them...help yourself...they will certainly work. I think you will kill them in short order (2 years or less) given your prior posts and inability to monitor usage, charging, state of charge etc.

[Herk7769]

There is clearly enough information here for you to make an informed decision; or you can just do what you want.

[Cypressloser]

Originally Posted by camaraderie

NO...that is simply a DEAD WRONG analysis of the article. Let's look at the + and minus' of AGM based on the article:

Spill-proof through acid encapsulation in matting technology
High specific power, low internal resistance, responsive to load
Up to 5 times faster charge than with flooded technology
Better cycle life than with flooded systems
Water retention (oxygen and hydrogen combine to produce water)
Vibration resistance due to sandwich construction
Stands up well to cold temperature

Limitations

Higher manufacturing cost than flooded (but cheaper than gel)
Sensitive to overcharging (gel has tighter tolerances than AGM)
Capacity has gradual decline (gel has a performance dome)
Low specific energy
Must be stored in charged condition (less critical than flooded)
Not environmentally friendly (has less electrolyte, lead that flooded)

Now lets add negatives....2-3 times the price. Doesn't like HEAT. DOESN'T Like to be continuously left on float. MUST be charged to 100% each time or capacity will be lost. FEWER life cycles than the comparable quality wet cell (Trojan will tell you this on their site and they make and sell both!)

Then lets' review the advantages of AGM as it applies to you.
NO WATERING is a nice benefit.
Spill Proof is of no concern in an upright coach.
Low internal resistance...good for charging IF you have a HUGE charger.
High Current power....good IF you have BIG instantaneous amp loads...you don't.
Better life cycle...an outright falsehood not supported by any battery mfr. ...try to find THAT claim on any battery mfr. site compared to their wet cells. Trojan says the opposite.
Cold temperature performance is better. Do you plan to use the coach in below zero F conditions?
Good vibration resistance...true compared to normal batts...but NOT compared to quality deep cycles like Trojan wet cells.

Don't get me wrong. I lived full time off the grid for 6 years and had an 1100 amp hour AGM bank...because I needed it for instant current drains, had a huge charger (130amps) had an 8kw generator to power the charger and batteries in an inaccessible area for watering with no ventilation.
They were the answer for me.
If you want to buy them...help yourself...they will certainly work. I think you will kill them in short order (2 years or less) given your prior posts and inability to monitor usage, charging, state of charge etc.

I apologize if it's inappropriate for me to 'hijack' your conversion but since we are avid boondockers it really caught my interest.
Wouldn't 6 Volt GC batteries offer better 'bang (AMP/h) for the weight'.
Other benefits of AGM batteries are, and that is why I really prefer them is they don't need to be vented, can be mounted in any position and don't corrode around the pols.

[Herk7769]

Originally Posted by Cypressloser

I apologize if it's inappropriate for me to 'hijack' your conversion but since we are avid boondockers it really caught my interest.
Wouldn't 6 Volt GC batteries offer better 'bang (AMP/h) for the weight'.
Other benefits of AGM batteries are, and that is why I really prefer them is they don't need to be vented, can be mounted in any position and don't corrode around the pols.

Not to answer for Cam, but I feel the advantage of being able to stay out when a plate shorts out in one of the batteries makes the 6 volt option a non-starter for me. Since you still need 2 batteries to make 12 volts (and the AH does not double), 2 12 volt batteries makes more sense to me.

I like AGMs too, but you really have to "not care about the cost" to go there since you can buy a lot more AH for the money with flooded cell. I also leave my batteries on the converter 24/7 so the AGM limitation of "not likeing" float is also a concern.

[Cypressloser]

Originally Posted by Herk7769

Not to answer for Cam, but I feel the advantage of being able to stay out when a plate shorts out in one of the batteries makes the 6 volt option a non-starter for me. Since you still need 2 batteries to make 12 volts (and the AH does not double), 2 12 volt batteries makes more sense to me.

I like AGMs too, but you really have to "not care about the cost" to go there since you can buy a lot more AH for the money with flooded cell. I also leave my batteries on the converter 24/7 so the AGM limitation of "not likeing" float is also a concern.

You are 100% correct, double the current or double the AH not both. I feel so embarrassed now, I used to have equipment with 12V batteries in series, parallel or single how could I not see this.

I still prefer the cleanliness in the battery bay .

[camaraderie]

Originally Posted by Cypressloser

I apologize if it's inappropriate for me to 'hijack' your conversion but since we are avid boondockers it really caught my interest.
Wouldn't 6 Volt GC batteries offer better 'bang (AMP/h) for the weight'.
Other benefits of AGM batteries are, and that is why I really prefer them is they don't need to be vented, can be mounted in any position and don't corrode around the pols.

For any 4 bank or more, then 6V makes excellent sense to me but for just 2 I prefer 12V for the reasons Herk said. ALSO..the REASON 6V makes sense is because you can get them cheap at sams and costco... and there's no place to get a TRUE deep cycle 12V Grp.31 that is competitive. 2 group 31's are every bit as good as golf carts...but the bank for the buck piece is missing!
I think that for people like you who boondock a lot...and have a big battery bank and battery monitor and understand the things that will ruin an AGM vs. a wet cell...AGM's can be an excellent choice.
We plan to do a lot of boondocking too but I'm not gonna mess with my bank right away as I want to understand our usage and space for both batts & cable runs. I may end up with AGM's again too but I'm probably just gonna install a Victron at first to preserve what the coach comes with and figure out my real usage & needs when I'm on "the hook" before deciding.
It's not clear to me if you have AGM 6V now or not... FWIW...I had the EastPenn/Deka's (8D's) and they served me very well at a price that was well below the Trojans and Lifelines...with virtually identical specs. They also make a 6V AGM.