Help me assess the value of lithium

[avanti]

So, I was browsing the esteemed Battery University site and I came across the following in the AGM section:

AGM offers a depth-of-discharge of 80 percent; the flooded, on the other hand, is specified at 50 percent DoD to attain the same cycle life.

https://batteryuniversity.com/learn/..._glass_mat_agm

This is the clearest statement I have seen that the infamous "50% discharge" doesn't apply to AGM.

[coss370]

Did you not read the comment? They got roasted to $hit.

I don't know who is right or who is wrong, but look at the data provided by battery makers.

https://relionbattery.com/products/r4000/rev-8d-330

https://www.victronenergy.com/upload...tteries-EN.pdf

https://www.odysseybatteries.com/docs/us-ody-tm.pdf

[booster]

Originally Posted by coss370

Did you not read the comment? They got roasted to $hit.

I don't know who is right or who is wrong, but look at the data provided by battery makers.

https://relionbattery.com/products/r4000/rev-8d-330

https://www.victronenergy.com/upload...tteries-EN.pdf

https://www.odysseybatteries.com/docs/us-ody-tm.pdf

Nothing of interest in the links that we haven't seen. I assume you are referring to the DOD vs number of life cycles charts. If you get time, I would suggest you read the discussions on that very topic on this forum, where the calculations of lifespan are done by how much energy in and out is done over the life of the batteries, not how many times they are recharged. The 50% rule of 1/2 the life is actually closer to a 15% loss of total energy by going to 80% down when you need to, and DOD averages so a 20% discharge would balance an 80% to be the same as two 50% ones. For that 15% loss of life, you get 60% more usable power than at 50% and can save buying and dragging around batteries you don't really need.


The calculations and conclusions above are based on those same style of charts as you list, so the very same data source, just used for a more an actual use and cost balance reality in real world use.



Sure they got roasted, as we have here for questioning the gospel of the 50% rule, but the data doesn't lie or believe urban legends, and it says the 50% rule is severely over estimating the shortened life of going to 80% vs 50% DOD.

[GeorgeRa]

Originally Posted by coss370

Did you not read the comment? They got roasted to $hit.

I don't know who is right or who is wrong, but look at the data provided by battery makers.

https://relionbattery.com/products/r4000/rev-8d-330

https://www.victronenergy.com/upload...tteries-EN.pdf

https://www.odysseybatteries.com/docs/us-ody-tm.pdf

He got roasted by internetS wisdom, right - https://www.researchgate.net/profile...orz_Pilatowicz

[avanti]

Originally Posted by coss370

Did you not read the comment? They got roasted to $hit.

I don't know who is right or who is wrong, but look at the data provided by battery makers.

https://relionbattery.com/products/r4000/rev-8d-330

https://www.victronenergy.com/upload...tteries-EN.pdf

https://www.odysseybatteries.com/docs/us-ody-tm.pdf

Just a note:
The first link (Relionbattery) does not appear to reference an AGM battery. It is VRLA, but not all VRLA batteries are AGM.

[coss370]

I am not on the side of 50 or 20 percent and I think battery capability is more of a black art as they can vary quite a bit. What I do know is that batteries don't like to be deep cycled and you shorten their lifespan the more you draw on them. If you don't care about it, have at it. I will use my battery till it is dead before I turn off the heat. At the same time, I am not going to put pointless loads on it when I don't need to.

Originally Posted by booster

Nothing of interest in the links that we haven't seen. I assume you are referring to the DOD vs number of life cycles charts. If you get time, I would suggest you read the discussions on that very topic on this forum, where the calculations of lifespan are done by how much energy in and out is done over the life of the batteries, not how many times they are recharged. The 50% rule of 1/2 the life is actually closer to a 15% loss of total energy by going to 80% down when you need to, and DOD averages so a 20% discharge would balance an 80% to be the same as two 50% ones. For that 15% loss of life, you get 60% more usable power than at 50% and can save buying and dragging around batteries you don't really need.


The calculations and conclusions above are based on those same style of charts as you list, so the very same data source, just used for a more an actual use and cost balance reality in real world use.



Sure they got roasted, as we have here for questioning the gospel of the 50% rule, but the data doesn't lie or believe urban legends, and it says the 50% rule is severely over estimating the shortened life of going to 80% vs 50% DOD.

[booster]

Originally Posted by coss370

I am not on the side of 50 or 20 percent and I think battery capability is more of a black art as they can vary quite a bit. What I do know is that batteries don't like to be deep cycled and you shorten their lifespan the more you draw on them. If you don't care about it, have at it. I will use my battery till it is dead before I turn off the heat. At the same time, I am not going to put pointless loads on it when I don't need to.

Personally, I wouldn't call it black art, but I would certainly say there have been many years of incorrect and misleading information about batteries spread by many of the battery manufacturers and sellers. They are the prime pushers of the 50% rule for lead acid over the years as it lets them sell more batteries, and the new wave of misinformation about lead acid is coming from many of the lithium battery producers and sellers, while at the same time making some questionable claims about their own products. I think it is very difficult for the mainstream customer to wade through what is true and what is sales hype.


The battery people are certainly not the only ones doing this, as the the charger manufacturers and sellers do the same stuff, mostly exaggerating and misrepresenting how well their equipment charges and takes care of batteries. IMO, the charger weaknesses and bad information are probably doing more damage, limiting more capacity use, and shortening battery life more than the use patterns are. Nearly no battery charging equipment gets batteries to 100% full on a full charge, without overcharging, from everything I have seen and tested, but nearly every charger is claimed to give full batteries on every charge cycle. It has now gotten to the point that poor charging is so common, even the monitor folks are starting to show batteries as full, when the aren't, because they apparently get too many complaints if they are set correctly and never show a full battery. Basically, being at 80-90% is the "new" full because it is pretty much what the chargers are going to give you.



I do totally agree that if you do understand that how you use your batteries will shorten life, or limit usable capacity, and are willing to accept that, have at it. In many cases, it is either the only choice or the only financially practical choice.

[Bud]

"They are the prime pushers of the 50% rule for lead acid over the years as it lets them sell more batteries"

booster, be nice. Ok, you are nice maybe squared.

Sweet Spot? A 20% rule would sell more batteries vs 50%! But would also result in more warranty stuff. Maybe the 50% rule made some sense for many decades. Even now, how many folks are 'boosters' with monitors? or just not boosters but average with monitors? or ignorant about using battery voltage meters?.................

Folks that buy very expensive agm batteries (Lifeline) are more battery knowledgeable than folks that buy flooded batteries, Generally. Not sure that the 50% rule should not be out there in a sense. Yet, if someone hears 20%, they can choose to learn.

I think that this forum is terrific with a bunch of boosters as it results in more freedom to choose based on evidence, credible evidence, proven facts. Thanks booster.

Bud



Heck if I know.

[booster]

Originally Posted by Bud

"They are the prime pushers of the 50% rule for lead acid over the years as it lets them sell more batteries"

booster, be nice. Ok, you are nice maybe squared.

Sweet Spot? A 20% rule would sell more batteries vs 50%! But would also result in more warranty stuff. Maybe the 50% rule made some sense for many decades. Even now, how many folks are 'boosters' with monitors? or just not boosters but average with monitors? or ignorant about using battery voltage meters?.................

Folks that buy very expensive agm batteries (Lifeline) are more battery knowledgeable than folks that buy flooded batteries, Generally. Not sure that the 50% rule should not be out there in a sense. Yet, if someone hears 20%, they can choose to learn.

I think that this forum is terrific with a bunch of boosters as it results in more freedom to choose based on evidence, credible evidence, proven facts. Thanks booster.

Bud

Heck if I know.

There seem to be getting to be a lot more monitors out there from what we see around here an other places online, but that says very little about the general public, I think, where there probably not very monitors compared to RVs.


I do think the usefulness of the monitors has gone down in one way and stayed the same in another. I had always thought that monitors would teach folks how to take better care of the batteries, but in many cases even if they learn they aren't charging well there aren't any good ways to anything about it as the charger manufacturers haven't stepped up to provide better chargers.


Especially with monitor manufacturers and installers (who have done it for a longer time), the monitors have morphed into meters that tell you about how much of the amount of charge you got is left to use. In reality it has almost nothing to do with how full your battery really got. The big problem is that few users know that is what is going on because nobody tells them. It isn't inherently wrong to operate that way if there is not an option for better charging in your life, but if you really want know how much power you have to set the monitor for a lower full battery capacity than the rated which you will never get to get anywhere near accurate information, I think. If you are winding up charged to 80% most of the time, the battery capacity would need to be set at .8 the rated capacity.


Does this complicate the 50% rule, you bet, as if you start at 80% and do 50% by amp-hour counting from .8C the battery is actually at 40% full. Does that matter? Not to me, but some might be concerned.


Bottom line to those who need/want to know pretty accurately how much power they have left would be to just do a capacity test from a typical full charge that your equipment will give and use that for setting the monitor battery capacity, or your calculations as to how long you can run stuff.

[Davydd]

Do any manufacturer's that supply AGM batteries in their Class B's have an automatic shutdown at 20% to prevent their batteries from completely discharging? My two Class B's with lead-acid batteries just worthless in my mined had idiot lights and no shutdown capability and it was very easy to fully discharge batteries. Most lead-acid battery banks have less than 200ah and it would be quite easy to discharge that last 20% if you are not attentive. Just leaving a refrigerator on DC and stopping for lunch could do it. Perhaps that is the reason for the 50% discharge urban legend.

[booster]

Originally Posted by Davydd

Do any manufacturer's that supply AGM batteries in their Class B's have an automatic shutdown at 20% to prevent their batteries from completely discharging? My two Class B's with lead-acid batteries just worthless in my mined had idiot lights and no shutdown capability and it was very easy to fully discharge batteries. Most lead-acid battery banks have less than 200ah and it would be quite easy to discharge that last 20% if you are not attentive. Just leaving a refrigerator on DC and stopping for lunch could do it. Perhaps that is the reason for the 50% discharge urban legend.

None of the manufactures that I know of use a low voltage cutoff as standard equipment, and I don't think any supply monitors either. They really want the users to have blind trust and not ask questions, it appears.


Yep, you certainly can kill the batteries, especially with an absorption frig on DC. I am certain it happens quite a bit.


I think some monitors have low voltage warnings and the Victron has contacts in it that could trigger a shutdown with a disconnect.

[RT-NY]

This has been an interesting and informative thread. A few posters mentioned adding a second alternator for charging. I had not heard of this before. If I am understanding correctly, you would then run the engine to charge the battery: does that require more fuel than a generator would consume? Could idling for a few hours to charge the battery harm the engine, especially on an older class B like on an older Dodge Roadtrek? Can you even add a second alternator to an older RV like that?

[avanti]

Originally Posted by booster

None of the manufactures that I know of use a low voltage cutoff as standard equipment

High-end inverter/chargers all have such a feature. I don't know if any of the mass-market upfitters use them, though.

[booster]

Originally Posted by avanti

High-end inverter/chargers all have such a feature. I don't know if any of the mass-market upfitters use them, though.

Our Magnum will shut down the inverter on low voltage that is settable, but I don't think it has the capability to shut down battery use. Does the Outback have outputs to control a shut off? Maybe a Magnum higher than ours might, but I don't recall a setting in the ARC-50 remote for it, and AFAIK they all use that one. I am sure a centrally integrated Victron setup could do it.

[avanti]

Originally Posted by booster

Our Magnum will shut down the inverter on low voltage that is settable, but I don't think it has the capability to shut down battery use. Does the Outback have outputs to control a shut off? Maybe a Magnum higher than ours might, but I don't recall a setting in the ARC-50 remote for it, and AFAIK they all use that one. I am sure a centrally integrated Victron setup could do it.

Hmm. I guess you are right. I was only thinking of the inverter. The DC loads don't even go through most inverter/chargers. You would need an output to control the main cutoff relay. Do any of the fancy BlueSea ACRs do this?

[booster]

Originally Posted by avanti

The DC loads don't even go through most inverter/chargers. You would need an output to control the main cutoff relay. Do any of the fancy BlueSea ACRs do this?

That is a very good and interesting question. If they did, it could be very useful for a lot of people.

[Davydd]

Originally Posted by RT-NY

This has been an interesting and informative thread. A few posters mentioned adding a second alternator for charging. I had not heard of this before. If I am understanding correctly, you would then run the engine to charge the battery: does that require more fuel than a generator would consume? Could idling for a few hours to charge the battery harm the engine, especially on an older class B like on an older Dodge Roadtrek? Can you even add a second alternator to an older RV like that?

A second under hood alternator is standard on Advanced RV's (ARV) since about 2013. They only produced one Class B with an Onan generator, their first circa 2012. Soon after a major upfitter, Roadtrek, adopted the technology and many others now have followed suit and there are several solutions available now for DIY. It is easy to do with a Sprinter as they had high idle options and brackets for it. You charge by driving and I can input a steady 280 amps per hour at 50 mph and a maximum of 330 initially to a lithium ion battery bank. An Onan or shore power charges at the rate of 120 amps? So, you don't have to drive very much to recharge. My high idle charges about the rate of 220 amps. Roadtrek, dwelt on the idleling aspect and people got the idea it was necessary to idle. I seldom did other than demonstrate my autostart feature to people which I don't remember ever invoking other than some "butt" start incidences.

Mercedes Benz warrants the operation for 100,000 miles and 5 years on their emissions which is the concern. They don't like it and discourage it for the idle feature but they sell it. Their first caveat is not to idle more than 2 hours without driving after for 40 minutes. I don't think they envisioned RV use. Emergency vehicle ambulance use and similar would not idle over 2 hours without driving.

[GeorgeRa]

A low voltage protection could be added to a battery disconnect relay most of us have like Intellitec or Bluesea. Managing a temporary voltage drop could be a problem but likely solvable.

https://www.amazon.com/Digital-Batte.../dp/B07929Y5SZ
https://www.amazon.com/Disconnect-Ch...G86SV1EZ9&th=1

[booster]

Blue Sea makes a low voltage disconnect, it appears. M-LVD


Only 65 amps, but if your inverter takes care of itself with it's internal cutoff, this would be enough to handle most users coach loads.


https://www.amazon.com/Blue-Sea-Syst.../dp/B00GZOP53M

[avanti]

Transits can be ordered with dual alternators from the factory. With this option, you can take off more than 200A directly from the chassis electrical system without modifications.

As DavyDD says, you need to be careful idling with a diesel, but it can be done within limits. Idling gasoline engines is not problematic. I also find that I do enough driving each day that idling is almost never necessary.

The above is part of the reason why my next rig will likely be a petrol Transit.