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Old 04-26-2017, 10:25 AM   #15
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Quote:
Originally Posted by nothermark View Post
... It's nice to have reserve but we get a long longer life out of lead acid staying above 50%........
Sure, and even longer if you stay above 49%, and more if above 48%. I understand your comment but 50% is not some magic number. Every user is different and saying this confuses people.

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Old 04-27-2017, 10:40 AM   #16
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The first problem is that there are battery chemistries that will fail if discharged to 0% SOC. Lithium polymer for one. They is why they generally have a built in controller that shuts them down at 10% or so. 50% on lead acid won't kill the battery but is not a bad myth as it is good practice. Running down to where the individual cells hit 0% thus dropping the total voltage will do significant damage as well as exceeding the capability of most people to recharge said batteries.
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Old 04-28-2017, 12:10 AM   #17
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Originally Posted by msturtz View Post
I have been working with and reading about batteries for a long time. I work in the research department of a heavy truck manufacturer. Strangely enough battery replacement is a major cost for our research fleet. That said, every major battery manufacturer publishes a chart or graph that describes the number of cycles you should receive for a particular model of battery based on the DOD (Depth of Discharge). Lead Acid batteries are not designed to be discharged to 100% DOD or 0% SOC (State of Charge). For example the batteries in my Palazzo are from Fullriver and the chart reads like this: if I only use the top 10% of the battery capacity or 90% SOC / 10% DOD I can get 5000 cycles out of the battery before it needs to be replaced. However, if I discharge the battery to 100% DOD / 0% SOC I only get about 600 discharge cycles before the battery will need to be replaced. For my rig I selected 80% SOC or 20% DOD as a set point for the AGS (Automatic Generator Start) system. This will give me approximately 2000 discharge cycles before the battery will need to be replaced. If you don't believe me here is the link to the charts Fullriver Battery DC224-6 Product Information Please keep in mind that Lithium based batteries are much more tolerant to deep discharges than lead acid. That said the material on the site suggests to use a 50% DOD measure for sizing their battery packs. That was the point of my question. Lithium battery systems usually use a battery management system to only allow you to discharge the battery to a preset point. However, that specific point may not be the best point for DOD for a long life of the battery. If I'm going to pay $1000 for a 100AH battery I don't want to destroy the battery or reduce it's life by not using it per the manufacturer's specifications.


I must correct you. The chart is based on the 20 hour rate not the 2 hour rate. In fact you should never discharge any battery to 100% DOD. The touted 50% figure is widely recommended by battery manufacturers as a compromise between battery cycle life and capacity. In fact the manufacturer also lists the other AH ratings due to the peukert effect. The peukert effect is the loss of AH the higher the amp draw. My Palazzo routinely draws well over 150 amps @12 VDC when we are using the microwave etc. for a short period of time. This means the higher AH values in the chart have value. Finally I use the AGS and BMK to recharge till after the end of bulk charge and shut down the generator. Every 3 days the ME-ARC50 is configured to recharge the batteries to 100% SOC.
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Old 04-29-2017, 11:59 AM   #18
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Fear Not - You Can Use 100% of Your Battery

Quote:
Originally Posted by msturtz View Post
I must correct you. The chart is based on the 20 hour rate not the 2 hour rate...
Really?
1. Go here: Fullriver Battery DC224-6 Product Information
2. Click on Graphs.
3. Scroll down to “Cycle Life Vs …” chart.
4. Look on the top right corner of the graph.

What does it say? It says “Based on BCI Testing @ 2 hour rate.” That means the chart is based on discharging the entire battery, 100% DoD, in just 2 hours.

Quote:
Originally Posted by msturtz View Post
...The touted 50% figure is widely recommended by battery manufacturers as a compromise between battery cycle life and capacity. ....
There is no doubt that manufactures have recommendations about battery use. So do I but that has not been the point of any of my posts.

It's interesting that you bring up Peukerts Law or various discharge rates. They all are based on 100% discharge of the battery and thus are proving my point.

It sounds like you want to cloud the issue and change the purpose of my post. It was not about performance or recommendations. I’m sure from your replies I won’t convince you. That’s OK but I do want to help others reading this to consider the source.

Quote:
Originally Posted by nothermark View Post
The first problem is that there are battery chemistries that will fail if discharged to 0% SOC. Lithium polymer for one. They is why they generally have a built in controller that shuts them down at 10% or so. 50% on lead acid won't kill the battery but is not a bad myth as it is good practice. ....
Hello northermark,

My comments were not about li-ion batteries but deep cycle lead acid batteries. However, as a battery system designer and retailer, we stock and sell 3 brands of Lithium batteries: Elite Power Solutions GBS, Relion and LiFeBlue. We use all 3 brands in RV’s. None of these batteries will fail if discharged fully.

Here's the Facts:
1. Each brand of li-ion battery can be discharged 100% without harm.
2. Each battery has a BMS system that allows 100% discharge, without harm.

Quote:
Originally Posted by nothermark View Post
... 50% on lead acid won't kill the battery but is not a bad myth as it is good practice...
The myth that I have been trying to dispel is that you can’t discharge more than 50%. You will use the battery up sooner or later. A person can and should discharge their battery as needed and not spend your days fretting about it. The real harm is done to batteries from improper charging. It’s the #1 reason we replace so many batteries. About 90% of what we see is damaged batteries from deficit charges.

So, here's the Facts:
1. 50% is no magic number any more then 40% or 60%. As for cycle life, you will get more cycles from shallow discharges than from deep discharges.
2. No damage will happen to any lead acid deep cycle battery by discharging it 100%, despite what one battery manufacturer has recently posted on their website. Shorter cycle life yes; damage no.

Quote:
Originally Posted by nothermark View Post
...Running down to where the individual cells hit 0% thus dropping the total voltage will do significant damage as well as exceeding the capability of most people to recharge said batteries….
The voltage of a 100% discharged battery under a C/20 load is 10.5 volts. Any battery charge source, converter, PV solar, inverter/charger, alternator, wind turbine or otherwise can recharge a 100% discharged battery.

My only purpose on this forum is to help people understand these issues better. Battery systems are my livelihood, every day. I do not speak from assumptions but from the skills of many years of study, use and hands on experience and over 3300 RV and off grid power systems designed and installed in the last 16 years. That’s all I’ll contribute at this time. No doubt more opinions will show up. So be it.

Larry
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I have a vast knowledge about PV solar, batteries and inverters. I'll try to provide the best answer if I know it and hopefully correct some "Campfire" talk. Full-time 1999-2004. Part time now. '92 Hawkins, 360AH Lithium Battery, 1480 Watts PV solar.
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Old 05-02-2017, 02:07 PM   #19
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Because of confusion that seems to exist on this topic, I would add that:

With Lifeline AGM's, 10.5v = 0% remaining charge (100% DOD) under any load from a 1hr rate to a 120hr rate.

It is important to note that the same battery that reads 10.5v under load, will rebound to an open circuit voltage of 11.2v to 11.6v after a 2-4 hours with no charging or discharging.

A true capacity test on any Concorde AGM is performed by running the battery down to 10.5v under a constant 25 amp load. (And then charging it back up at the maximum available current)

Respectfully,
Marc
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Old 05-02-2017, 09:29 PM   #20
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Quote:
Originally Posted by BatteryPro View Post
Really?
1. Go here: Fullriver Battery DC224-6 Product Information
2. Click on Graphs.
3. Scroll down to “Cycle Life Vs …” chart.
4. Look on the top right corner of the graph.

What does it say? It says “Based on BCI Testing @ 2 hour rate.” That means the chart is based on discharging the entire battery, 100% DoD, in just 2 hours.



There is no doubt that manufactures have recommendations about battery use. So do I but that has not been the point of any of my posts.

It's interesting that you bring up Peukerts Law or various discharge rates. They all are based on 100% discharge of the battery and thus are proving my point.

It sounds like you want to cloud the issue and change the purpose of my post. It was not about performance or recommendations. I’m sure from your replies I won’t convince you. That’s OK but I do want to help others reading this to consider the source.



Hello northermark,

My comments were not about li-ion batteries but deep cycle lead acid batteries. However, as a battery system designer and retailer, we stock and sell 3 brands of Lithium batteries: Elite Power Solutions GBS, Relion and LiFeBlue. We use all 3 brands in RV’s. None of these batteries will fail if discharged fully.

Here's the Facts:
1. Each brand of li-ion battery can be discharged 100% without harm.
2. Each battery has a BMS system that allows 100% discharge, without harm.



The myth that I have been trying to dispel is that you can’t discharge more than 50%. You will use the battery up sooner or later. A person can and should discharge their battery as needed and not spend your days fretting about it. The real harm is done to batteries from improper charging. It’s the #1 reason we replace so many batteries. About 90% of what we see is damaged batteries from deficit charges.

So, here's the Facts:
1. 50% is no magic number any more then 40% or 60%. As for cycle life, you will get more cycles from shallow discharges than from deep discharges.
2. No damage will happen to any lead acid deep cycle battery by discharging it 100%, despite what one battery manufacturer has recently posted on their website. Shorter cycle life yes; damage no.



The voltage of a 100% discharged battery under a C/20 load is 10.5 volts. Any battery charge source, converter, PV solar, inverter/charger, alternator, wind turbine or otherwise can recharge a 100% discharged battery.

My only purpose on this forum is to help people understand these issues better. Battery systems are my livelihood, every day. I do not speak from assumptions but from the skills of many years of study, use and hands on experience and over 3300 RV and off grid power systems designed and installed in the last 16 years. That’s all I’ll contribute at this time. No doubt more opinions will show up. So be it.

Larry
Thank you for your post. However, you seem to be conflating the test method they used with the cycle life of the battery. If you look closely at the chart you will see that they did NOT discharge the battery to 100% DOD in every case. Some test batteries they discharged repeatedly to 10% DOD, 20% DOD, and so on up to 100% DOD. The discharge method they used to determine cycle time has nothing to do with the validity of the DOD cycle life of a battery. That was the entire point of the chart to educate customers into how to use their batteries for long life. It was also the point of my post.

If you chose to discharge a battery to 100% DOD every time you will significantly shorten its life. I.e. the number of "cycles" you will get out of the battery. There are many misconceptions about batteries. A single short period of 100% DOD may, but will usually not, destroy a lead acid battery. However if a battery is left dead for a period of time such as for a few days it will most likely destroy the battery. I agree that improperly charging a battery will destroy a battery as well. Don't get me started on single stage converters sold with most RVs particularly towable Class C units. A method for ruining good batteries.

With LiFePO4 batteries that have BMS systems those systems prevent 100% discharge of the cells and cut off at an amount determined by the battery manufacturer. This is the method Nissan used in the Leaf. Their Lithium battery pack is actually larger than their rating to prevent users from completely discharging it.

Recently, I worked on a project where we were building systems using Lithium batteries and we had no BMS system to manage the charge / discharge cycles, we had to hand code all the charge and discharge algorithms ourselves. I also worked on a project where we had industrial lead acid batteries for RF equipment where we had to size the battery pack and power supply system to supply the equipment. Sure, the industrial systems are "over engineered" to maximize lifetime of service but they work every time you need them. Another example is the industrial battery pack we have for our headquarters office. We have AGM industrial batteries in series to produce 400 VDC that is in parallel to the rectified 480 VAC 3 phase which supplies the two 750KW UPS systems providing power to our office. The battery packs we use last for 10 - 20 years! Why? Because we size them so we maximize life. The commercial trucks we build have the same battery sizing guidelines, we have hotel loads on our trucks as well however our battery systems are sized to maximize life of the battery packs. Our customers would not tolerate replacing batteries as often as RVers do. Our battery packs are 4 times larger for lower loads than comparable RV battery packs.

It never ceases to amaze me the difference between industrial systems that absolutely must work all the time and RV systems where people tolerate poor quality and ruined vacations because of pushing equipment right at the edge.

I suspect the differences in opinion we are having is related to our different backgrounds: You are from the RV / home market and my background is from the industrial & commercial market where poor quality and short life is not tolerated. I don't want to spend $2,000 - $5,000 on a completely new battery pack because I deliberately shortened the life of the battery pack. I certainly don't claim to know everything and have a lot more to learn. That said I don't want a ruined vacation because the battery pack quit as soon as we left. My point is pass along my experience and knowledge so people can make informed choices.
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Old 05-03-2017, 06:10 AM   #21
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FWIW I see your point. The battery won't die at 49%. Thinking it will points to the basic problem of customers who half understand the issue then start telling every one their misinformed opinion as fact.

My point is that no matter what battery one buys one has to either depend on the salesman or learn enough to know what the tradeoffs are for the specific chemistry in use and then have some say in the matter or expect problems. That comes down to having a salesman that wants to sell what the customer wants not what the salesman might want. I might want a 10 year life, he might want 10 battery sales in 10 years. As a customer I am stuck with having to figure out what he is selling me and tweak my demands or expectations accordingly.
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Old 05-03-2017, 04:13 PM   #22
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Real-life Palazzo battery stats

This has nothing to do with "proper" max battery draw, but I think it is still on topic for the original poster's question.

I attached some stats on some real-life usage of our lithium battery on a 33.3 palazzo. The graphs show 2 days plugged in, and 3 days completely off the grid. The on-grid charger was not used at any point. You will notice that we have a lot (900W) of solar charging things up during the day, but you can see the fridge and microwave/coffee/entertainment usage after sundown. Hope this helps.
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Old 05-04-2017, 05:57 AM   #23
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venturer, thank you for posting that. I am always interested in seeing real world application data!

I may have missed the info, but how long have you been running those batteries?

Marc
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Old 05-08-2017, 02:31 PM   #24
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venturer, thank you for posting that. I am always interested in seeing real world application data!

I may have missed the info, but how long have you been running those batteries?

Marc
This system has been running for just at one year.
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Old 05-09-2017, 06:15 PM   #25
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FYI: Lithium batteries cannot be used if you have the new Firefly multiplex control system that is showing up on more and more coaches. AGM's are the only alternative to the stock batteries with coach.

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Old 05-10-2017, 10:10 AM   #26
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FYI: Lithium batteries cannot be used if you have the new Firefly multiplex control system ....

Don
Hello Don,

Please tell us why you say that. We have designed several high power PV solar systems and Li-ion battery upgrades for Dutchstar and other high end coaches using Firefly controllers.

Larry
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Old 05-10-2017, 12:22 PM   #27
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Thanks everyone for posting your opinions. I'm totally confused but thanks for giving me something to think about. I'm a part timer, and have a 4 bank of one year old interstate batteries, and 2-200w solar panels, yet I can't make it through the night if I run the refrigerator and DISH TV....I even hit power save on the microwave. So I don't run TV. AGS set at 11.9 and set at 70% bulk to float charge rate. And to think, I was happy with myself when I showed anther Palazzo owner how to adjust his Magnum Panel from 15, 30 or 50 amp shore power.

What is the best resource for understanding electrical (amp and volts)? Thought about installing a BMK Battery Management Kit, but was told it's not necessary. I'd like to like off the grid every once and awhile for a few days.

If your thinking this guy is not the sharpest knife in the draw.......your right.
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Old 05-10-2017, 02:11 PM   #28
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battery problems

I would make sure the Trombetta is working properly.
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