My Lithium Upgrade

[dmb496]

However...if viewed from the outside, looking in

[MsNomer]

My 1957 house doesn’t have an external outlet, but I can snake the cord under the garage door across the sinking spot in the driveway. I’ve got an electric heater running through a thermostatically controlled outlet. This will work fine until another limb hits the power line and cuts power again. And Davyyd, even your high-dollar storage would be vulnerable to power outage.

Speaking of which, you mention remote start during storage. I assume you would clear out the accumulated CO somehow before you entered?

[avanti]

Originally Posted by MsNomer

you mention remote start during storage. I assume you would clear out the accumulated CO somehow before you entered?

Actually, that was me, and I was talking about outdoor parking.

This is actually the scenario that pushed me over to considering lithium to being practical for my purposes. I would never consider unattended remote start as SOP. But, as an absolute last resort if the batteries are getting dangerously cold for storage, and my SOC is getting too low to warm the batteries, and I am far, far away, it seems like a viable option.

Such conditions will surely be very rare, but the possibility has to be accounted for. And saying "just get shore power" is not helpful advice given my circumstances.

[Davydd]

Originally Posted by MsNomer

My 1957 house doesn’t have an external outlet, but I can snake the cord under the garage door across the sinking spot in the driveway. I’ve got an electric heater running through a thermostatically controlled outlet. This will work fine until another limb hits the power line and cuts power again. And Davyyd, even your high-dollar storage would be vulnerable to power outage.

Speaking of which, you mention remote start during storage. I assume you would clear out the accumulated CO somehow before you entered?

My condo garage has all underground electrical service out in farmland next to a former 1950's Nike missile base. Highly doubtful that service would be interrupted by weather. With lithium batteries it could last well over a week maybe a month since everything is off with any outage and since it is my man cave with internet and wood work shop I get out there more than a few days per week.

Rare that single family homes don't have an outside outlet is my point. Yes, there are probably exceptions. I had an unnecessary 30a outlet (15a would have done it) wired and put in my outside garage wall in my previous home by an electrician where I parked my RV about 14 years ago for $180. Sure inflation has occurred since but I doubt any other addition to an RV to protect lithium batteries would be as cheap. If you want to invest in expensive lithium batteries that are not easy to remove in northern climates you should make provisions to have some shore power at a minimum for long term storage to maintain them in place and internal or external heat when necessary.

I can and have remote start capability turned off in my garage. If stored outside, I would not trust remote start over shore power as reliable to keep batteries charged and internally heated or externally heated if necessary in freezing weather.

[avanti]

Originally Posted by Davydd

If stored outside, I would not trust remote start over shore power as reliable to keep batteries charged and internally heated or externally heated if necessary in freezing weather.

In a storage scenario, there is no need to keep batteries heated in freezing weather. The ONLY concern is the small but real risk of of a truly-frigid spell (which would virtually always be short) such that the minimum storage temperature is not maintained. This is typically well below 0F. THIS is the only scenario in which I would contemplate remote starting, and even then it would not be necessary until the battery's SOC was too low to power the heaters. Solves my problem. The Self-discharge rate of good batteries (of any chemistry) is so low that periodic recharging merely due to time is not an issue.

I don't know how many different ways I can say that I have a requirement for storage without power. It has nothing to do with saving $180. Telling me I shouldn't want this is not helpful.

[Davydd]

...Sez the man who has never had lithium ion batteries in a Class B. For one, connected batteries have much more loss than just self-discharge rates. If you have disconnected batteries from everything you can store long term. But then if you disconnect the batteries they are going to seek ambient temperature, not self-heat or power heaters and you will have a dead van electrically so you could not take advantage of all your automation ambitions or trickle charge you AGM chassis battery. Sez the man with 7 years practical and observable experience of having lithium ion batteries in a Class B. I don't know how many different ways I can say that.

[GeorgeRa]

Originally Posted by avanti

In a storage scenario, there is no need to keep batteries heated in freezing weather. The ONLY concern is the small but real risk of of a truly-frigid spell (which would virtually always be short) such that the minimum storage temperature is not maintained. This is typically well below 0F. THIS is the only scenario in which I would contemplate remote starting, and even then it would not be necessary until the battery's SOC was too low to power the heaters. Solves my problem. The Self-discharge rate of good batteries (of any chemistry) is so low that periodic recharging merely due to time is not an issue.

I don't know how many different ways I can say that I have a requirement for storage without power. It has nothing to do with saving $180. Telling me I shouldn't want this is not helpful.

Solar power should be able to keep batteries AGM or Li fully charge to last during these cold weather spells unless solar panels are covered with snow. Snow remedy could be vertical or almost vertical panel(s) mounts for no shore power storage. There are a few potential issues but unintended consequences should be lower than with remote starting malfunction, I think.

[@Michael]

Originally Posted by avanti

The ONLY concern is the small but real risk of a truly-frigid spell (which would virtually always be short) such that the minimum storage temperature is not maintained. This is typically well below 0F.

With a bit of insulation and a 15w battery heater at 100% duty cycle, I kept my single 100AH LiFePo4 above freezing when ambient was -20F. If all one needs to do is keep it above 0F, the current consumption from self-heating should support a battery that keeps itself warm during a brief cold spell (unless one is way up north).

Seems like one would need to hold reserve capacity in the LiFePo4's such that if they are below freezing, there is enough capacity for them to warm themselves with the battery heater to a point above freezing, at which point one could use the alternator (or solar) to re-charge them.

[avanti]

Originally Posted by Davydd

...Sez the man who has never had lithium ion batteries in a Class B. For one, connected batteries have much more loss than just self-discharge rates. If you have disconnected batteries from everything you can store long term. But then if you disconnect the batteries they are going to seek ambient temperature, not self-heat or power heaters and you will have a dead van electrically so you could not take advantage of all your automation ambitions or trickle charge you AGM chassis battery. Sez the man with 7 years practical and observable experience of having lithium ion batteries in a Class B. I don't know how many different ways I can say that.

OK, let's try one more time:
--When I build a battery disconnect, it is absolute. There is NO LOAD, therefore all we are talking about is self-discharge. I then very carefully add back a few critical monitoring circuits that I have engineered to have negligible load. I have explained this to you before (with pictures). An ESP32 connected to WiFi has a draw measured in milliamps, and will spend most of its time in a deep sleep mode I which the load is practically too small to measure. IT IS JUST NOT AN ISSUE. Just because the van that you have been driving for 7 years can't do this, does not mean that it can't be done.

--OF COURSE the batteries will go down to ambient. That is exactly what we want them to do. It is actually GOOD for most chemistries to be stored cold when not in use, just as long as they don't exceed their absolute storage minimum temperatures, which we both agree is rare. Lithium was unacceptable to me until I had a plan to deal with this unlikely possibility. I now have one.

[avanti]

Originally Posted by GeorgeRa

Solar power should be able to keep batteries AGM or Li fully charge to last during these cold weather spells unless solar panels are covered with snow. Snow remedy could be vertical or almost vertical panel(s) mounts for no shore power storage. There are a few potential issues but unintended consequences should be lower than with remote starting malfunction, I think.

I am probably going to try to avoid solar entirely. A panel that could be oriented vertically is just a little too elaborate for my taste. I see no issues with remote start, and the chances of ever needing it are not great. The cumulative probabilities of needing the capability and then failing are within my risk tolerance. Just hoping for warm weather was not.

[avanti]

Originally Posted by @Michael

With a bit of insulation and a 15w battery heater at 100% duty cycle, I kept my single 100AH LiFePo4 above freezing when ambient was -20F. If all one needs to do is keep it above 0F, the current consumption from self-heating should support a battery that keeps itself warm during a brief cold spell (unless one is way up north).

Yeah, that's what I am thinking.

Seems like one would need to hold reserve capacity in the LiFePo4's such that if they are below freezing, there is enough capacity for them to warm themselves with the battery heater to a point above freezing, at which point one could use the alternator (or solar) to re-charge them.

My plan for that is to arrange to be able to power the battery heater from the engine charging source until they are warm enough to charge.

[avanti]

How important is this idea that lithium batteries shouldn't be kept fully charged during storage? I really want a system that will need minimum care and feeding, but it is not clear to me how to arrange to automatically keep the batteries charged but not too charged, especially if I decide to include a little solar. AGMs like to be charged, and it is so simple to use the solar panel and a Trik-L-Start to keep everything topped up. The "don't keep it full" stipulation adds a lot of complexity. What happens if I ignore it?

[booster]

Originally Posted by avanti

How important is this idea that lithium batteries shouldn't be kept fully charged during storage? I really want a system that will need minimum care and feeding, but it is not clear to me how to arrange to automatically keep the batteries charged but not too charged, especially if I decide to include a little solar. AGMs like to be charged, and it is so simple to use the solar panel and a Trik-L-Start to keep everything topped up. The "don't keep it full" stipulation adds a lot of complexity. What happens if I ignore it?

I have wondered similarly on that question. It is also a "how full is too full" type thing. One could imagine it has to do with some kind of unwanted plating or degradation on at totally full and holding so anything under that would not be a problem. But many are recommending storage at 50%, so is it a sliding scale between 50% and totally full, and if so is the damage linear over that scale?


It seems logical that the now more common "head space" with full cutoff charging might be just fine and get a majority of the benefit of 50% at the normal charging cutoff point of 13.8v or so that some are using. If so, it all gets easy because nothing really changes from day to day for the most part.


Still up for grabs, I think, but I think that is one thing that would sure be nice to have some real data on as so many vans are stored where they may need battery heat and capacity to run them is needed.

[GeorgeRa]

Originally Posted by avanti

How important is this idea that lithium batteries shouldn't be kept fully charged during storage? I really want a system that will need minimum care and feeding, but it is not clear to me how to arrange to automatically keep the batteries charged but not too charged, especially if I decide to include a little solar. AGMs like to be charged, and it is so simple to use the solar panel and a Trik-L-Start to keep everything topped up. The "don't keep it full" stipulation adds a lot of complexity. What happens if I ignore it?

Originally Posted by booster

I have wondered similarly on that question. It is also a "how full is too full" type thing. One could imagine it has to do with some kind of unwanted plating or degradation on at totally full and holding so anything under that would not be a problem. But many are recommending storage at 50%, so is it a sliding scale between 50% and totally full, and if so is the damage linear over that scale?


It seems logical that the now more common "head space" with full cutoff charging might be just fine and get a majority of the benefit of 50% at the normal charging cutoff point of 13.8v or so that some are using. If so, it all gets easy because nothing really changes from day to day for the most part.


Still up for grabs, I think, but I think that is one thing that would sure be nice to have some real data on as so many vans are stored where they may need battery heat and capacity to run them is needed.

I have the same questions, soon or later I will need to replace my AGMs. The easiest will be to replace with the same batteries but Li is an option. But Li option I would only consider if Li batteries would be as invisible as my current AGMs. I check SOC once a day in average, they are invisible. I don’t see my current system being able to automatically control Li batteries use. It seems as selecting one charging source at the time, limit charge current, keeping attention to charge endpoint would still require sone intervention. I am looking forward to see as you pave the road to a no attention Li system.

[MobileCabin]

A somewhat unbiased source of information on a technology are graduate students. Particularly their thesis since it has been reviewed by assumed technical experts on the subject. Following the discussion on this thread, you can find a study on almost any aspect of batteries from applied engineering to the material science of new concepts to the economics of batteries. Most of them do not suffer from the marketing bias displayed in all of those battery sales/marketing sheets and websites.

For example, I found the background review in this master's thesis on Li batteries to be helpful (https://mospace.umsystem.edu/xmlui/handle/10355/73777) to understand storage issues. This is just one of many on the subject, just the one I grabbed off the internet first.

Do you your own searches and you might find answers to your battery build problems.

[booster]

Originally Posted by MobileCabin

A somewhat unbiased source of information on a technology are graduate students. Particularly their thesis since it has been reviewed by assumed technical experts on the subject. Following the discussion on this thread, you can find a study on almost any aspect of batteries from applied engineering to the material science of new concepts to the economics of batteries. Most of them do not suffer from the marketing bias displayed in all of those battery sales/marketing sheets and websites.

For example, I found the background review in this master's thesis on Li batteries to be helpful (https://mospace.umsystem.edu/xmlui/handle/10355/73777) to understand storage issues. This is just one of many on the subject, just the one I grabbed off the internet first.

Do you your own searches and you might find answers to your battery build problems.

I do quite a bit of that kind of research and would warn that when you searching be sure you are looking at information on LiFePO4 batteries and not other lithium chemistries. Unless the information states the finding also relates to the LiFePO4 batteries that information may or may not be applicable. There is very much more information on other chemistries out there than the RV styles, so can be quite hard to find good information. Much of what you do find it either paid for or made by the battery manufacturers, sometimes even disguised as an impartial technical paper.


I certainly wish that there was a lot more on the LiFePO4 batteries like there is for phone batteries and mass storage ones.

[@Michael]

Originally Posted by avanti

How important is this idea that lithium batteries shouldn't be kept fully charged during storage?

Specific to LiFePo4 (vs. other Lithium chemistries) I found this article:

https://nordkyndesign.com/practical-...battery-cells/

About half-way down he has charts showing the amount of degradation vs. state of charge, and state of charge vs. resting voltage. Seems like one could maintain the battery at or near 50% SoC by carefully sampling resting voltage and keeping it right around 13.15-13.25V (if last discharged) or 13.24-13.26 (if last charged).

Rather than charging until a voltage is reached, one could charge for a fixed period at a fixed rate, let the batteries rest until a low voltage threshold is reached, then charge for a fixed period at a fixed rate. That would keep the batteries SoC within a range (I.E. 40-60% SoC).

[booster]

That is a pretty interesting article in quite few ways. If the data at 77*F for degradation vs SOC during storage in applicable to lower temps we see in storage many places, being as low as possible in SOC to have the least degradation. This would be detrimental to saving capacity to run heaters.



The very end of the article was the best for me where they finally gave recommended charge voltage minimums to get rid of memory, which appear to be certain to appear. The 3.5v/cell is in the 14v range and is substantially over charging capable when compared to the much lower full voltage they show earlier. They acknowledge this and kind of wound up by the end saying that the combination of reading voltage, which would probably the 14v, and also reading charging amps to the batteries to indicate when to end charging to stop around 90% SOC. This, by coincidence, is also the best for way lead acid charging termination for their desired 100% SOC. For our Lifelines they want the current at .5C amps at absorption voltage. They described chargers with voltage and time charge termination but not a charger that could do amp based in practice. ASFAIK, the only shore chargers, would be the MS2000 and higher Magnums with the BMK kit, maybe the Outback chargers with a shunt, and probably a centrally controlled Victron system. There are at least two solar controller brands that will do it, Blue Sky and Trimetric. Of course it is pretty certainly possible the charge termination could be terminated by using a battery monitor with monitor activated relay contacts to terminate the charging from volts and amps, but would take some additional hardware.

[MsNomer]

It is indeed quite handy to have the Trimetric set so that solar will never fully charge lithium.

[avanti]

Originally Posted by @Michael

Seems like one could maintain the battery at or near 50% SoC by carefully sampling resting voltage and keeping it right around 13.15-13.25V (if last discharged) or 13.24-13.26 (if last charged).

Thanks for the reference.

So, if the goal is to have a van that doesn't require complicated care and feeding by humans, the problem is that if I have to store at 50% SOC but want to operate at 100%, this seems to require a mode that has to be set so the van knows that it is going to be stored. That might not be too bad if we could build a "sleep" button (or some such). But it is worse than that. I have to remember to set the mode BEFORE I get home, because it will be too late then--the van would charge to 100% during the drive home. Worse yet, I have to do it while the battery is already below 50% (which may never occur on some trips). This kind of sucks.

Maybe the answer is to just let it charge to 100% and have a mechanism by which the van bleeds the SOC down to 50% (or whatever) after entering "sleep mode", perhaps by running a heater or something. A little wasteful, but probably no big deal in the grand order of things.

An then there's the issue that @booster mentioned: Having to go down to 50% is counter to the goal of saving power to run the heaters when weathering a frigid spell during storage. No obvious way around this, beyond giving up storage at the optimal SOC. Going down 10% is one thing--50% is kind of painful.

Now I remember why I have been lukewarm to lithium.