Building an Lithium Battery Heater Kit

[booster]

Originally Posted by markopolo

Yes to defaulting to 13.6V for the 9100/9200 standard units.

Just a note: 13.6V will get the batteries to near 100% SOC. See: https://www.classbforum.com/forums/f...tml#post120850

We have had that discussion several times and certainly seems to be the trend for making batteries last. IIRC 13.6-13.8 is what many are using. It would also make for an interesting idea for those that have the combo lithium and AGM setup. Get a standard PD charger with unpluggable, or make switchable and you could charge both ways 13.6 for lithium and Charge Wizard multstage for AGM. Single switch could control charge relay and switch the charger.

[Davydd]

Originally Posted by Snowy

Your diagram seems to show the battery heaters taking power from your batteries. Is that so? I would caution on this - discharging a LiFePO4 battery below -4F is damaging.

Advanced RV has posted an excellent primer on RV Batteries.
https://advanced-rv.com/wp-content/u...hite-Paper.pdf

For LiFePO4 batteries, you want to prevent charging below 32F and discharging below -4F. There is also a spec stating that you should not store a LiFePO4 battery below -4F, but the storage spec is somewhat controversial. PleasureWay doesn't worry about storage temps in cold Manitoba - they just disconnect the battery for cold-weather storage. I have heard anecdotal reports of people letting their batteries get to -20F, and not observing any damage, although i wonder if they have reduced their capacity but just don't know it.

I live in Alaska, so i will be installing some sort of heater. I think the ideal heater would be a 120v battery blanket wired into the 120v side. This way for storage, you can plug the rig in, disconnect the battery to prevent charging/discharging, but get power to the battery blanket. If you just want to put a little heat on the batteries because you are using the rig during the winter, and don't have shore power, you can still use the battery blankets by turning on the inverter.

I had Advanced RV's first build of the high capacity 800ah battery lithium ion system in 2014. They were the Elite Power Solutions batteries listed ARV white paper on batteries published in 2018 you referenced. I don't know if they are installing them now. They install the Volta 56v system and I am getting the Lithiumwerks Valence system of 4 - 144ah 12v batteries = 576ah stored inside the van this time. On the road you would keep a van warm enough so supplemental heat would not be required. I now store my van inside a garage at 50F. minimum.

The -4F was ironclad when I contacted Elite Power Solutions for storing whether or not discharging. I had a 12v electric resistance pad of two 5 amps each sandwiched between the battery banks which fed directly off the batteries. They are in a fiberglass box under the van. They keep the batteries above 41F at all times when the ambient temperature gets down to -20F. 12v is more efficient because you don't have to keep your inverter on. With 800ah capacity it was not a problem on the road as one drives every day in those below freezing temperatures. In storage you would need shore power or heated storage. The batteries are still good after 6.5 years. I stored outside for the first two winters in Minnesota plugged into shore power.

[jakegw2]

Booster - this is a great point and one I had to test to figure out:

EPEVER Triron MPPT 40A solar charge controller - when the battery is disconnected (I have a disconnect switch right next to the battery so I can disconnect it when I work on it) the voltage floats all over the place, sometimes as high as 17v. I'm not too worried about this, the only thing that would ever get this voltage would be the propane / CO2 detectors and perhaps the lights. It settles down with a load but periodically resets itself (probably whenever it goes into scan mode).

Zamp PWM solar controller (I have both with a selector switch to choose between them. I just upgraded by adding the EPEVER, the Zamp dual-battery controller was already there so I left it in. When I am storing the unit I don't need the maximum efficiency, just a trickle charge and the Zamp delivers this to both the chassis and house batteries). With the battery disconnected it delivers between 13-15v, but the power is pulsed unless the load pretty closely matches the solar input at the moment. Useless for electronics and won't run the battery heater controller.

Xantrex XC 2k Inverter / Charger - Delivers 14.2v steady even when the batteries are disconnected. The battery heater will work fine on this.

Progressive 9200 InteliPower charger - This delivers a steady 13.6v with or without a load without a battery connected. I know this for certain because I use it as my benchtop power supply when testing RV electrical items.

[booster]

Originally Posted by jakegw2

Booster - this is a great point and one I had to test to figure out:

EPEVER Triron MPPT 40A solar charge controller - when the battery is disconnected (I have a disconnect switch right next to the battery so I can disconnect it when I work on it) the voltage floats all over the place, sometimes as high as 17v. I'm not too worried about this, the only thing that would ever get this voltage would be the propane / CO2 detectors and perhaps the lights. It settles down with a load but periodically resets itself (probably whenever it goes into scan mode).

Zamp PWM solar controller (I have both with a selector switch to choose between them. I just upgraded by adding the EPEVER, the Zamp dual-battery controller was already there so I left it in. When I am storing the unit I don't need the maximum efficiency, just a trickle charge and the Zamp delivers this to both the chassis and house batteries). With the battery disconnected it delivers between 13-15v, but the power is pulsed unless the load pretty closely matches the solar input at the moment. Useless for electronics and won't run the battery heater controller.

Xantrex XC 2k Inverter / Charger - Delivers 14.2v steady even when the batteries are disconnected. The battery heater will work fine on this.

Progressive 9200 InteliPower charger - This delivers a steady 13.6v with or without a load without a battery connected. I know this for certain because I use it as my benchtop power supply when testing RV electrical items.

The solar controllers would be of worry to me as the voltage is uncontrolled, it appears, without reference from a battery. This is very common. You probably aren't seeing the actual peaks in voltage as they could be short spike, particularly when the switch is thrown to take the battery out. One of the biggest risks with it, per the manufacturers of the controllers, is having the battery disconnected while in dark conditions and driving it out into bright sunlight. Depending on the solar panels max open circuit voltage the controller, and maybe downstream items could be hit with maybe 22v as that is what many modern panels max at. I think you would also find the voltage to vary depending on sun conditions as it is likely you are just balancing the loads against available power. Turn something off or on and it will change and maybe spike. Even 17v is really to0 high for any electronics that are hooked up at the time, even backfeeding on other chargers, separators, etc.


This is the reason so many of the lithium systems don't run the chargers to cover van current use and connect the loads only to the batteries separate from the charging sources. If the batteries go offline for any reason, and there are quite a few that can happen, you don't want the loads to see a big uncontrolled spike. Unfortunately, this also leaves you needing to recharge batteries more often because you won't be carrying daily use with solar or shore charging and will run off the batteries until you hit recharge settings. It can also leave you low on charge when you would have been full if you had been running off the chargers.



Switching the loads to the PD power supply when on shore power would be safe, but solar gets much tougher. Maybe there are some, but I don't know of any solar controllers that work without a battery reference, basically as a power supply like the PD does. I assume you are on a single alternator, so that would be giving reference to system when driving, but having solar then is of little benefit. If you had the system setup so that the solar saw the starting battery whenever the lithium was not online it could see the starting battery for reference. You would, of course, lose some the solar to chassis use, but would work.

[markopolo]

Originally Posted by Davydd

................. The batteries are still good after 6.5 years............

A capacity test is the only way to know that. I would really like it to be proven true because it would be so much easier just to keep the batteries at a high state of charge during the frequent lay-up periods common to RV use. It's becoming a nuisance bringing my portable packs down to around 50% every time they're not going to be used for bit.

If Davydd's battery pack is say above 90% of original capacity remaining then that would be good enough for me. If already at or nearing 80% of original capacity then that would be a red flag.

I'm hoping we get to see data from any trustworthy source to settle the no-float (no standby) vs float (standby voltage) uncertainty.

[booster]

Originally Posted by markopolo

A capacity test is the only way to know that. I would really like it to be proven true because it would be so much easier just to keep the batteries at a high state of charge during the frequent lay-up periods common to RV use. It's becoming a nuisance bringing my portable packs down to around 50% every time they're not going to be used for bit.

If Davydd's battery pack is say above 90% of original capacity remaining then that would be good enough for me. If already at or nearing 80% of original capacity then that would be a red flag.

I'm hoping we get to see data from any trustworthy source to settle the no-float (no standby) vs float (standby voltage) uncertainty.

Yep, capacity testing is so very often missing from what we hear about "100% full" and "perfect condition" related to battery banks, but is the critical thing, IMO.


The float/no float is a big question that needs to get answered accurately, and I hope it does soon. I would also add that it would be nice to know if charging at and then floating at 13.6-13.8v or so is harmful or not, even if floating at full might be

[avanti]

Originally Posted by markopolo

If Davydd's battery pack is say above 90% of original capacity remaining then that would be good enough for me.

Yes, it would be great to see these data.

Of course, this begs the question of how you define "original capacity". Do we understand the relationship between published specifications and actual, measured capacity of new batteries? Absent load-test data on the batteries when new, I think I might take the difference between 90% and 80% with a grain of salt.

[booster]

Originally Posted by avanti

Yes, it would be great to see these data.

Of course, this begs the question of how you define "original capacity". Do we understand the relationship between published specifications and actual, measured capacity of new batteries? Absent load-test data on the batteries when new, I think I might take the difference between 90% and 80% with a grain of salt.

I agree, it is in your own best interest to check the capacity of your new batteries to confirm the batteries are good and your charging is adequate. Periodic retesting can be done whenever later on to see how they have done over time. I did ours when new after a few cycles to get them to full capacity as Lifeline recommends, and they tested above rated by nearly 5% so this would affect the 80 or 90% or rated point quite a bit.


I will be interested in how ours test this year, as it has been more of a non use than use year, so they didn't get used much at all and spent a lot of time on float. They haven't been tested in two years at this point.

[Davydd]

Originally Posted by markopolo

A capacity test is the only way to know that. I would really like it to be proven true because it would be so much easier just to keep the batteries at a high state of charge during the frequent lay-up periods common to RV use. It's becoming a nuisance bringing my portable packs down to around 50% every time they're not going to be used for bit.

If Davydd's battery pack is say above 90% of original capacity remaining then that would be good enough for me. If already at or nearing 80% of original capacity then that would be a red flag.

I'm hoping we get to see data from any trustworthy source to settle the no-float (no standby) vs float (standby voltage) uncertainty.

Meaning, I still have the percentage of battery use today as before. ARV locks out 20% in that with an 800ah battery bank you are really working off of 640ah. The battery bank automatically shuts down after 640ah are used up and they you have to recharge. I generally set it arbitrarily at 50% where I have to recharge. Recharging is generally driving though with a second alternator you can high idle. The way I understand it if original capacity did indeed lose 20% I would never know it judging by the usage and performance of the batteries. The lock out also means there will be no abuse of the batteries by accidentally discharging them completely as people are free to do with lead-acid in most all Class Bs. The other safe guard I have is the batteries have always been above 41F optimally so there is no freezing abuse. I only had batteries go below freezing one time when I finally discovered the battery heater was miss wired when I thought it was on but it was not. On the other higher end abuse I have seldom, if at all, encountered that. The other loss potential is cycles and I haven't come close to that concern.

Anyway, I won't be doing any further testing. Our van is being traded in back to ARV in two weeks.

If you want to read about my particular batteries, check out Technomadia.com. They had the same batteries in a 500ah configuration in a converted bus and they retired them after 7.5 years (installed 2011.) They also abused their batteries much more than mine. I haven't read the article yet but in an earlier report is they routinely stored on asphalt in Phoenix, AZ for long periods of time. I imagine their batteries got caught in the higher end temperatures.

[jakegw2]

Based on the testing I will turn off my solar controllers whenever I expect a battery disconnect event.

The one item I haven't been able to test, and the one that is the most likely challenge area for my setup, is what happens when the batteries are below freezing but above 0 deg. In this range the BMS will allow discharge, so the batteries will be available to supply continuous power, but will not accept charge to buffer surge current. I think that the solar controllers will operate properly in this state and provide current to power the loads, but I have no way to replicate this one-way current flow state at the moment.

I'm not worried about a complete battery disconnect event, my plan is to keep the batteries warm enough that it won't happen.

In other news - I a layer of rock wool insulation to the side of each battery opposite the heating pad and a 1.5" layer on top of the batteries (with a layer of plastic over top to protect it from water / dust / mud - the underlayer however is direct rock wool against the batteries). In my follow-up heating test with this new configuration I got a 20 degree temperature rise over ambient, which should be more than enough to protect the batteries in any weather I will be experiencing. It also leaves enough exposed that I don't think I will have any serious overheating issues to worry about either. Hopefully I have achieved the balance of heating / cooling and will not need to drop the battery tray again for the remainder of my ownership (fingers crossed)! On the other hand however I have gotten so good at it that I might do it anyway to add some new upgrade down the road.

[booster]

Originally Posted by jakegw2

Based on the testing I will turn off my solar controllers whenever I expect a battery disconnect event.

The one item I haven't been able to test, and the one that is the most likely challenge area for my setup, is what happens when the batteries are below freezing but above 0 deg. In this range the BMS will allow discharge, so the batteries will be available to supply continuous power, but will not accept charge to buffer surge current. I think that the solar controllers will operate properly in this state and provide current to power the loads, but I have no way to replicate this one-way current flow state at the moment.

I'm not worried about a complete battery disconnect event, my plan is to keep the batteries warm enough that it won't happen.

In other news - I a layer of rock wool insulation to the side of each battery opposite the heating pad and a 1.5" layer on top of the batteries (with a layer of plastic over top to protect it from water / dust / mud - the underlayer however is direct rock wool against the batteries). In my follow-up heating test with this new configuration I got a 20 degree temperature rise over ambient, which should be more than enough to protect the batteries in any weather I will be experiencing. It also leaves enough exposed that I don't think I will have any serious overheating issues to worry about either. Hopefully I have achieved the balance of heating / cooling and will not need to drop the battery tray again for the remainder of my ownership (fingers crossed)! On the other hand however I have gotten so good at it that I might do it anyway to add some new upgrade down the road.

Does your BMS actually separate the charge and discharge sides? This is the first I recall hearing about that. It is what Roadtrek tried to do with ecotrek, but eventually gave up on it. Even if they do separate, you will need to wires to battery connected to two different terminals, I would think, I for charge and one for load, plus they would need to connect together during charging. If the solar is just still connected to the battery on a single wire, I am relatively certain the battery will still accept the charging, it is just that you shouldn't do it because of harming the battery. For a while, so systems were saying you could charge down to colder temps because they would put very low current to the charging until the battery warmed up.


The BMS will normally disconnect on several different scenarios besides temp, including over and under voltage and maybe some others including glitches.