2021 RT Chase: Trying to understand (and fix) my coach electric

[PreciousRoy]

Hello all!

I'm going to try to keep this streamlined and to the point. Hope this isn't too much of a retread - I've read all I could find related to the Ecotrek systems in the various iterations of these vans but still would like some help "connecting the dots" as it were. The majority of the info available seems to be related to the older Hymer/Roadtrek models with hard switch controls, not the newer models with Firefly controls. I'm assuming that at least some of the issues present in the older models have been fixed in my van, but would like to determine exactly what does and doesn't need help.

Symptom: Extremely short battery runtime

My main symptom is my 12V Li batteries cutting out after very short periods (sometimes as little as 2-3 minutes), even after I've driven 6-8 hours or after/while plugged into shore power. I can hear contactors in the modules chunking and can see the voltage on screen go from 13.7-8 to the 12.8-13.0 range when this happens. Resetting the battery modules brings them back temporarily, but only for a few minutes.

I remember right after we bought it and took our first "shake-down" trip to the beach, being able to run the A/C while on battery for 4-6 hours without issue. However, after almost a year of ownership and treating the batteries as I was instructed (disconnect when not in use, otherwise let the solar handle it), I'm lucky if I can get a few minutes of time with the inverter on before the batteries clunk off (and lucky if the A/C will start at all unless on shore power).

I don't seem to have any visibility into the state of the system other than the voltage display on the Firefly panel (the panel shows Batt 1 and Batt 2 "on" seemingly regardless of their real world state, and the "reset button" is just a software function).

The Van:

The van is a 2021 Roadtrek Chase (a variant of Zion). Purchased used from a dealer in Oct. 2023 w/ under 6,500 miles. The van is equipped with the following:

• 2 x 200Ah Lithium modules (KS2 rev L3)
• 1 x ?Ah AGM battery in parallel
• 2nd alternator w/Balmar MC-614 charge controller
• 3 x (100W?) rooftop solar panels w/Epever charge controller
• KS2 3kW Inverter/Charger

Assumptions I've made from what I've read here and on the Roadtrek Zion Owners' FB group:

• All 3 charging systems are probably misconfigured
• The wiring in my van is probably OK, but I'd like to make sure of that
• The battery modules themselves are hopefully OK and are just shutting down to avoid damaging conditions

Things I don't know yet:

• Can I (and if so, how can I) actually know the status/health of the Li modules without disassembling them? They have what I assume is a LV monitoring connection, although I don't know what that harness is connected to.
• How is the "reset" function of the Firefly actually working and how do I know if the contactors I hear are opening/closing the Charge terminal, Discharge terminal, or both?
• (Slightly sarcastic but not entirely) Between the improvised electrics and "freedom-promoting (for flammable gases, that is)" propane systems (another fun problem I'm currently fixing), how are any of these vans still here?

Is this fixable (without any or at least much component replacement)?

I've already planned on reconfiguring and relocating the solar charger to a better place. It is currently inside an upper cabinet with zero ventilation. I'm planning on moving it down into the ventilated cabinet that currently houses the inverter (I will also add a DIN-mount circuit breaker to the solar panel feeder since it appears there isn't any disconnect on that).

I'm also planning on reconfiguring the UHG charge controller with the settings from SUIET.

I also need to verify that the charge setting on the inverter is correct and fix if not (it is currently set to "Gel").

Am I right in thinking that by correcting the charging setup (and possibly the wiring), I can get my 12V system working more or less as intended, hopefully without dropping and replacing battery modules?

[GeorgeRa]

How heavy load do you use? Gel charging parameters are slightly lower than AGM batteries, is this the setup stated in KS2 inverter/charger manual?

[PreciousRoy]

Originally Posted by GeorgeRa

How heavy load do you use? Gel charging parameters are slightly lower than AGM batteries, is this the setup stated in KS2 inverter/charger manual?

Not sure how to classify my desired load, but wife and dogs usually require the use of A/C when parked, so I'd like to be able to have a few hours of A/C for meal stops, afternoon trips, etc.

The A/C on this van is 120VAC only, so that brings inverter into the mix.

Lighting is all LED and we use a little as possible. Intermittent water pump usage. Fridge is 12V only.

Heat, cooking, and water heating are all Propane.

Not looking for a week of off-grid camping or anything, just enough to make a day trip without shore power. I figured 400Ah should be able to handle that if working properly.

As for the inverter, the manual does list the charge profile specs. Current setting of Gel states Bulk 14.0V/Float 13.7V. There is a LFP charge setting as well that states Bulk 13.6V/No float. That is changed with a tiny rotary switch on the inverter case so it won't be difficult.

[GeorgeRa]

What is the recommended bulk voltage in batteries’ manual?

AC will draw about 15A 120VAC while running (higher at start) which would be about 190A DC, at 50% duty cycle 400Ahr batteries should give you about 3.4 hrs. AC time. Definitely longer than just a few minutes but certainly not days. You could have lower wattage AC so you can recalculate more accurate drawing numbers.

[PreciousRoy]

Originally Posted by GeorgeRa

What is the recommended bulk voltage in batteries’ manual?

That's kind of how I arrived here. The KS2 modules are (literally and figuratively) a black box. The only documentation Roadtrek provided was a single-page quick start guide that explained how to reset the batteries (with a completely different control panel than my van, FWIW).

All technical info I've been able to glean about these batteries has come from existing threads on this forum and a couple of helpful websites made by Hymer/Roadtrek owners who were solving their own battery issues. Unfortunately, those models all had older modules, older wiring methods, and different management/control systems.

I'd like to know how the Firefly system interfaces with all of this. Is it just simply reading volts and relay status in a couple of places, or is there any "intelligence" behind it. That has been hard to discover so far.

[mumkin]

If you are a member of the FB Zion/Simplicity group, they could likely answer most of these questions. And there is a member, Nick, from Northeast RV in Beavertown, PA, who can be very helpful on the phone. We have members who drive across country for his shop to fix their Roadtreks. It sounds like you're knowledgeable enough to troubleshoot with him over the phone if he has the time.

As to AC, you are likely at a max of about 3 hours if your batteries are healthy. Longer requires the larger battery bank.

Since you are in CA, your best location for help is up near San Francisco, Edge Van Works.

https://edgevanworks.com/

Another in SoCal is Dan Neeley who freelances out of his home.

Home

The catch may be the Firefly; you may need to consult that company.

[PreciousRoy]

Some encouraging results from this afternoon.

Battery tests:

Got a chance to do some work in the van after work. I relocated the solar controller from the upper cabinet down to the inverter cabinet and cleaned up some wiring around the inverter while I was in there. They'd shoved about 10 feet of extra wire up inside the void behind the bodywork so I re-terminated all of that and put it in loom.

Once I had the battery-side wiring back together, I used the Firefly batt. disconnect to turn on the 12V system. When I turned the system on, it was at 12.8V with just the AGM enabled. Turning on both KS2 modules got me to 13.2V. It held stable at 13.2V while I ran various lights, the roof vent, and charged my cell phone.

During this time, the batteries didn't cut out once. This was with the solar charger connected to the charge side of the batteries, but not charging (panels disconnected).

After a half hour, I decided to test the inverter. With the load of just the inverter, the voltage dropped to 13.1V and held steady. I left it this way for around 5 more minutes.

At that point, I decided to go really nuts and test a big load. I started the A/C and ran it for 15 minutes. During the test, the compressor cycled on and off, with the system voltage dropping to 12.9V with the compressor on, recovering to 13.0V with just the fan on. After 20 minutes of that, I shut down the A/C and inverter, at which point the voltage recovered to 13.2V.

The entire time I ran from the batteries was roughly 90 minutes, during which time I never heard one of KS2 modules cut out. Seems like the batteries are quite healthy, even as this low of a SoC.

Next steps:

• I've reconfigured the inverter charger for LiFePO (13.6V) profile. Tomorrow I'll drag the cord over to the house and charge from the inverter. That way I won't damage them with any further testing.
  
• I'm waiting for the 30A disconnect for the solar panel array feeder before I can connect those back up, and I'm also waiting for the MT-50 programmer for the Epever solar charge controller.
  
• I still need to reprogram the Balmar UHG controller, but as long as I don't drive anywhere for a while, that's no biggie.

[booster]

13.6v will probably make your batteries charge very slowly if they are like ours and others I have heard of. They also will not get 100% full according to most specs but would get very close. At 13.6v our 618ah bank of SOK lithium is only charging at 33 amps with 85-90% SOC.


Most manufacturers are still recommending 14.0-14.6v for charging, although that is a bit higher than we use. They do it to get 100% and many need to balance and do it only when at the top voltage.


We do most of our charging at 13.8v setting on the 2nd alternator regulator and stop the charging at 81-85% SOC to preserve battery life. For day to day charging our solar is set lower to prevent accidental overcharging, but speed doesn't matter because it can only put out 15 amps anyway. When I do a yearly "calibration" point charge with our shore charger I do reduce the voltage to 13.6v and stop the charging at 34 amps. Then I reset the battery monitor that controls the remote alternator regulator to 80% so it shuts off charging right there on every charge.


We don't use the batteries for air conditioning so would use much less capacity per day than you probably will.


I think that at 13.6v you won't have enough time driving to fill the batteries at the low charge rate many days, so would need shore power to recharge fully. 400ah of batteries is probably right on the edge of enough for AC running on a regular basis and will require a lot of recharging.

[PreciousRoy]

Thanks for the info, all.

Regarding charge voltage and SoC, now that I've at least determined that the modules are happy to be used with all of the chargers off, my primary goal is making sure I can keep them inside that window between extremes where the BMS shuts them down (although, theoretically if the charge-side cutout works as intended, the discharge relay should stay closed. My prior experience suggests otherwise, but I'm not inside the box so I don't know for sure).

I've read that KS2 is now recommending 13.6V across the board for charge voltage, so my first act will be to keep everything there and see where we are after a few trips. I've also read that they have a 13.7V charge-side cutout. I'm not sure I fully believe that as it seems really low, but now that I have more visibility and control of the charging systems, at least I can test that hypothesis and adjust.

The entire thing seems unnecessarily complicated for what it does, but I guess there were reasons. Few people want to know much more than how to turn things on and off, and the fewer service calls the better.

For now, I'm happy just getting more than a few minutes out of the Lithiums so I'm celebrating the progress made and planning for the future. Once I'm satisfied with the stability, I can start tuning charge voltages to push the boundaries of capacity. Honestly, though, I'd rather get 300Ah than nothing.

[booster]

It will be interesting for you to see where in the charge cycle the battery charging starts slowing down. Some of it may be determined by how they define 12.6 and 12.7 volts. This has been somewhat of an issue for me on our system because it appears that none of the sources go to more precise than a .1v setting.


Does 12.6v mean it will see and display 12.6v from 12.6-12.7, or from 12.55 to 12.65 volts? For instance. Plus is the shutoff read to more accuracy so actually shuts off at 12.60 with little variation. Our sources appear to handle it differently but it is very hard figure out exactly how they do it.


Another concern that happens to us if we use a voltage cutout for charging is that the sources may not have a hold timer on them so they have to see the voltage hold for a period of time, like a minute or two. It is very easy to get spikes of 3v or more by turning loads on and off as the charger can't react quick enough to prevent them. On our magnum, the startup spike from starting the charging is enough to do and it shuts off by the absorption set time at that point which isn't accurate.


Hopefully, you will not have these issues with your system but be aware.


How big is your charger?


This appears to be for the old system, but the settings would likely be the same and are very low voltage and especially current.

https://roadtrek.com/wp-content/uplo...-June-2020.pdf

30 amps for one battery so only .15C
50 amps for two batteries so .125C
90 amps for 4 batteries so .11C


All of them are under the .20C charge rate that is commonly used for super safe charging so their system must have some issue with high rate charging like they used to recommend to recover capacity quickly due to AC use.


The Balmar will also need to be turned down, which can be done but it isn't always obvious, by two different methods. The alternator could easily do over 150 amps continuous.


The solar will not need any throttling as 300 watts will be much lower than the recommended voltages.

[PreciousRoy]

Testing on the inverter charger

Opened the van up this morning to test the batteries on the inverter charger. When I started the system, the voltage on the Firefly showed 12.6V (!). This is with both KS2 batteries off, so I've determined that

a) That is the AGM battery voltage (and it isn't great either)
b) The voltage displayed on the Firefly panel is the voltage on the charge side of the batteries.

Test results weren't great. I engaged both modules one at a time. Displayed voltage went up to 13.2V with Batt 1 engaged, and 13.3V with both. This seemed OK to me, especially since they haven't been charged for a while.

Once I turned on the inverter/charger and plugged into shore, I heard the tell-tale chunk of contactors and the displayed voltage spiked to 15.0V, eventually settling to 13.7-13.8V.

"Resetting" the batteries is the only way I can think of to tell which one(s) shut down. Resetting Batt 1 forced the contactors on, then within a couple of seconds it shut down again. Resetting Batt 2 changes nothing, which to me suggests that Batt 2 was happily connected the whole time.

I can repeat this process ad-infinitum with the same results. Batt 1 just does not want to stay on while there is a charging source connected. Batt 2 seems happy with whatever.

Originally Posted by booster

This appears to be for the old system, but the settings would likely be the same and are very low voltage and especially current.

https://roadtrek.com/wp-content/uplo...-June-2020.pdf

30 amps for one battery so only .15C
50 amps for two batteries so .125C
90 amps for 4 batteries so .11C

Charger is the KS2 KS3K110.01 inverter charger. Going by that KS2 battery guide (the posted guide is for rev L2 - mine are L3 so it's the closest thing I've seen so far), they say to leave your inverter on charge profile "1", which on their inverter is "Gel USA" (14.0V Boost/13.7V Float). On more recent advice from KS2, I'd changed mine to charge profile "9" (LiFePO4, 13.6V Boost/No Float). I suppose I could change that back seeing as it doesn't seem to have made much of a difference anyway.

From the dealer, my inverter was set to 50% charge current, which from tables in their manual looks to be roughly 37.5A. For a 2 battery system like mine, that looks like ~.075C if I'm doing that calculation correctly.

I still need to plug a voltage meter into the discharge side of the system so I can compare what's on that end and see if the Battery 1 is completely disconnecting or just shutting down the charge side when it goes. Wish I had more data from the BMS, but it doesn't seem to be in the cards.

I'm finding myself questioning why the inverter/charger is combined. The 12V terminal on the inverter is connected to the 4/0AWG cables which travel underfloor and correspond to the charge terminals on the Lithium modules (the AGM is also on that circuit) That means that when not plugged into shore, it is drawing from the charge side of the batteries (and the AGM). This is also where the solar charger connects (and possibly the UHG? - Haven't traced that one yet).

At the same time, all the other 12V distribution in the van is fed from a 2/0AWG cable connected to the discharge of the Lithium batteries, which is common with the charge side (and the AGM) only when both charge and discharge relays on both Lithium batteries are closed.

Since my Lithium Batt 1 is immediately opening one or both relays with a charging source connected, I'm only able to use whatever is in the 200Ah Battery 2 and the AGM. However, with no charging source connected, both Batt 1 and Batt 2 happily stay online, as I discovered during my testing yesterday.

When I'm on shore power, I can use the 120V but I'm not charging the Lithium batteries if they've cut out. Once I unplug (which is the way I was told to do it - always connect and disconnect shore with the inverter on), the inverter tries to start drawing from the batteries, but usually one or both of the Lithiums have shut down so it hits the AGM hard and quickly shuts down from undervoltage.

I don't like the idea of just going back to discrete batteries for 12V and a genset for 120V, but sometimes I see the beauty in the simplicity.

I won't get the parts to finish the solar charger until tomorrow, so that remains to be reconfigured. For now it is disabled. I should be able to reprogram the Balmar today as all I need for that is a magnet and time.

Perhaps I can reconfigure the inverter to be just an inverter, then get by with just the solar and UHG charging the batteries. Maybe I can complicate things even more with a better 120VAC charger plugged into the 120VAC distribution in the van.

[booster]

Originally Posted by PreciousRoy

Testing on the inverter charger

Opened the van up this morning to test the batteries on the inverter charger. When I started the system, the voltage on the Firefly showed 12.6V (!). This is with both KS2 batteries off, so I've determined that

a) That is the AGM battery voltage (and it isn't great either)
b) The voltage displayed on the Firefly panel is the voltage on the charge side of the batteries.

Test results weren't great. I engaged both modules one at a time. Displayed voltage went up to 13.2V with Batt 1 engaged, and 13.3V with both. This seemed OK to me, especially since they haven't been charged for a while.

Once I turned on the inverter/charger and plugged into shore, I heard the tell-tale chunk of contactors and the displayed voltage spiked to 15.0V, eventually settling to 13.7-13.8V.

"Resetting" the batteries is the only way I can think of to tell which one(s) shut down. Resetting Batt 1 forced the contactors on, then within a couple of seconds it shut down again. Resetting Batt 2 changes nothing, which to me suggests that Batt 2 was happily connected the whole time.

I can repeat this process ad-infinitum with the same results. Batt 1 just does not want to stay on while there is a charging source connected. Batt 2 seems happy with whatever.



Charger is the KS2 KS3K110.01 inverter charger. Going by that KS2 battery guide (the posted guide is for rev L2 - mine are L3 so it's the closest thing I've seen so far), they say to leave your inverter on charge profile "1", which on their inverter is "Gel USA" (14.0V Boost/13.7V Float). On more recent advice from KS2, I'd changed mine to charge profile "9" (LiFePO4, 13.6V Boost/No Float). I suppose I could change that back seeing as it doesn't seem to have made much of a difference anyway.

From the dealer, my inverter was set to 50% charge current, which from tables in their manual looks to be roughly 37.5A. For a 2 battery system like mine, that looks like ~.075C if I'm doing that calculation correctly.

I still need to plug a voltage meter into the discharge side of the system so I can compare what's on that end and see if the Battery 1 is completely disconnecting or just shutting down the charge side when it goes. Wish I had more data from the BMS, but it doesn't seem to be in the cards.

I'm finding myself questioning why the inverter/charger is combined. The 12V terminal on the inverter is connected to the 4/0AWG cables which travel underfloor and correspond to the charge terminals on the Lithium modules (the AGM is also on that circuit) That means that when not plugged into shore, it is drawing from the charge side of the batteries (and the AGM). This is also where the solar charger connects (and possibly the UHG? - Haven't traced that one yet).

At the same time, all the other 12V distribution in the van is fed from a 2/0AWG cable connected to the discharge of the Lithium batteries, which is common with the charge side (and the AGM) only when both charge and discharge relays on both Lithium batteries are closed.

Since my Lithium Batt 1 is immediately opening one or both relays with a charging source connected, I'm only able to use whatever is in the 200Ah Battery 2 and the AGM. However, with no charging source connected, both Batt 1 and Batt 2 happily stay online, as I discovered during my testing yesterday.

When I'm on shore power, I can use the 120V but I'm not charging the Lithium batteries if they've cut out. Once I unplug (which is the way I was told to do it - always connect and disconnect shore with the inverter on), the inverter tries to start drawing from the batteries, but usually one or both of the Lithiums have shut down so it hits the AGM hard and quickly shuts down from undervoltage.

I don't like the idea of just going back to discrete batteries for 12V and a genset for 120V, but sometimes I see the beauty in the simplicity.

I won't get the parts to finish the solar charger until tomorrow, so that remains to be reconfigured. For now it is disabled. I should be able to reprogram the Balmar today as all I need for that is a magnet and time.

Perhaps I can reconfigure the inverter to be just an inverter, then get by with just the solar and UHG charging the batteries. Maybe I can complicate things even more with a better 120VAC charger plugged into the 120VAC distribution in the van.

From what we hear quite a number of folks have ditched the KS2 system for something that is actually usable and understandable. With lithium pricing way down now, that might be worth investigating.


At 400ah, you are marginal on AC use anyway, so a generator may be the best option, especially now that you can get an Onan that is actually livable on noise level and is less sensitive to ethanol fuel.


400ah of normal aftermarket lithium system is not all that expensive, probably less than replacing one module from KS2. 400ah is plenty for a compressor frig and your other use so no saving of power required because of the need for AC.



There have more and more 200-600ah systems documented on this forum and it probably would be worth the read of them. Pouring money, time and angst into a incapable system is the probably one of the worst power system things to live with.


I hope Mumkin jumps in on the best way to replace the system as I think she follows it closer than the rest of us here.

[PreciousRoy]

Well, as it happens, I'll be ditching at least part of the KS2 system anyway. The magic smoke has been released from the Inverter/Charger.

They provide an RJ-45 port on the module as well as instructions for connecting to the unit via TCP/IP. I connected the dots incorrectly and assumed the RJ-45 was for Ethernet. Turns out that the RJ-45 is for some proprietary connection and connecting it to Ethernet will cook the control board.

I'm fairly sure I can repair it, but I have a trip in 2 weeks and don't have time to bother with that right now. Maybe in the future I'll refurb it and use it for a home solar project or something.

Incidentally, I've found that Cosuper Power Systems is the actual manufacturer of the KS2 inverter in case anyone else is interested.

Now that I'm replacing the inverter/charger anyway, I need to decide if I want to replace it with the same box or take the opportunity to get a better product with better charging control at the same time.

I plan on retaining the KS2 battery modules for now to keep costs down. At least until I can determine if they are useless.

Am I dumb for thinking it might be better to replace the inverter/charger with an inverter only? The batteries already have solar and UHG as charging sources. The only real complication would be replacing the functionality of the transfer switch and separating the charge/discharge terminals of the Lithium modules.

Ugh - the saga continues.

[booster]

At least now you have an assignable cause for at least part of the issue


Before you make any real changes to the system, it may be a good idea to open up the batteries, which appear to be out of warranty so no problem there, and test charge each of the cells to see what their condition is, and also individually balance them. If they have problems and you don't know it, you will very likely get poor results for your repairs and replacements you will be doing.


All it takes to do is a $30 10 amp regulated and settable power supply to charge them and a good, preferably to .001v reading and accuracy, multimeter.



If they confirm as good, you will be in much better shape for determining and testing your improvements.

[PreciousRoy]

Originally Posted by booster

At least now you have an assignable cause for at least part of the issue

Yep. Got a chance to remove the old inverter yesterday. I've ordered a new inverter/charger (Renogy REGO 3kW) and that will arrive in a few days. This one has the ability to create custom charging programs and includes a BT radio + smartphone app so I can monitor it without crawling under the bed.

The reasons I went with a replacement inverter/charger were cost and simplicity. I found that separating the functions (adding my own 30A disconnect, shore-side 15A breaker + outlet for charger, AC transfer switch, separate charger, and separate inverter) would cost just as much or more and take up way more space than I have available.

Now while I wait for the new inverter/charger, I just have to install the solar panel disconnect, clean up some of the factory 12V distribution wiring, and mount the solar charger in its new location.

The existing 12V wiring is... interesting. It seems like whoever did this van had no cutters (extra wire was just shoved up inside any cavity available), had no strippers (strips appear to have been made with a pocketknife - sometimes half the strands were cut off too), and crimped the grocery-store grade terminals with needle-nose pliers.

Originally Posted by booster

Before you make any real changes to the system, it may be a good idea to open up the batteries, which appear to be out of warranty so no problem there, and test charge each of the cells to see what their condition is, and also individually balance them. If they have problems and you don't know it, you will very likely get poor results for your repairs and replacements you will be doing.

That will definitely be a future project, but for now it seems that as long as I can keep the voltages low enough to keep Batt 1 from cutting out, I'll be able to use them both. In the future if I want to deal with battery replacement, I may just gut the boxes and install one of the many commodity 12V LifePo 200Ah batteries out there.

[booster]

Originally Posted by PreciousRoy

Yep. Got a chance to remove the old inverter yesterday. I've ordered a new inverter/charger (Renogy REGO 3kW) and that will arrive in a few days. This one has the ability to create custom charging programs and includes a BT radio + smartphone app so I can monitor it without crawling under the bed.

The reasons I went with a replacement inverter/charger were cost and simplicity. I found that separating the functions (adding my own 30A disconnect, shore-side 15A breaker + outlet for charger, AC transfer switch, separate charger, and separate inverter) would cost just as much or more and take up way more space than I have available.

Now while I wait for the new inverter/charger, I just have to install the solar panel disconnect, clean up some of the factory 12V distribution wiring, and mount the solar charger in its new location.

The existing 12V wiring is... interesting. It seems like whoever did this van had no cutters (extra wire was just shoved up inside any cavity available), had no strippers (strips appear to have been made with a pocketknife - sometimes half the strands were cut off too), and crimped the grocery-store grade terminals with needle-nose pliers.



That will definitely be a future project, but for now it seems that as long as I can keep the voltages low enough to keep Batt 1 from cutting out, I'll be able to use them both. In the future if I want to deal with battery replacement, I may just gut the boxes and install one of the many commodity 12V LifePo 200Ah batteries out there.

It will be interesting on the cutout. If you have a 13.7v cutout stated if doesn't need much of a spike or such to trigger it, depending a lot of the speed of that trigger. If it ignores really short spikes, you will be more likely no to cut out compared to if it is a near instantaneous read like our Magnum is for the timed absorption timer start.


Most of the newer BMS systems monitor the individual cells for high cutout so they would be looking at individual cell voltage of 3.425v to trip out, so very little cell imbalance to cut off the charging. Early cutoff of charging is now recognized as one the best ways to tell if you have cell imbalances on systems that trigger cutout from any given cell going high enough. I have no idea how Roadtrek did it.

[PreciousRoy]

Balmar Charger Config and More Testing

With the inverter/charger dead but still connected (this was important because the connection points for the Firefly coach disconnect switch and solar chargers were at the inverter terminals), I set to re-configuring and testing the Balmar UHG controller.

Here are the settings I landed on (sort of a hybrid between the SUIET Hacks and KS2-recommended settings). These are very gentle to the batteries and will result in not getting the absolute max capacity but that's no longer the primary goal.

Program: UFP
High voltage limit: 13.6v
Temp Co limit: 13.6v
Bulk voltage: 13.5v
Bulk time: 6h
Abs voltage: 13.5v
Abs time: 6h
Float voltage: 13.5v
Float time: 6h
Low volt limit: 12.7v
Bulk/Abs field limit: 27%
Float/Abs field limit: 65%
Alt temp limit: 100C
Batt temp limit: 52C

I also configured the startup delay to 10s so I'd have a chance to start the engine and go back to watch the voltmeter.

I started the test by turning on the coach batteries at the Firefly. AGM voltage was 12.2 at startup.

Turning on Lithium Batt 1 raised system voltage to 13.1 and held stable.
Turning on Lithium Batt 2 raised system voltage to 13.3 and held stable.

I started the engine at this point and went to watch the voltmeter. After 10s, the voltage raised to 13.5 as expected and held steady. After roughly 2 minutes, Batt 1 clunked off.

Resetting Batt 1 resulted in it clunking off again after 7 sec.
Resetting again, clunk off in 5 sec.
Resetting over and over resulted in near immediate cutout. Batt 2 stayed online the whole time.

I ran the engine for roughly 30 minutes, charging Batt 2. When I turned the engine off, system voltage held stable at 13.5v.

With all charging off, I reset Batt 1 again. Instant clunk-out. I said screw it, left the batteries on, and went inside for lunch and did some other work.

After a few hours I went back to the van. System voltage had dropped to 13.4v. On a whim, I reset Batt 1 and it stayed latched. I ran the overhead fan and lights for hours while cleaning up and doing other stuff and both batteries stayed online the entire time. Final voltage when I shut it down was 13.3v.

My theory on Batt 1 is that its internal BMS is reading the system voltage or charge current inaccurately and shutting down too early. For what it's worth, Batt 1 seems OK to charge slowly off of Batt 2 while both are connected, as long as the voltage stays at 13.4v or below.

I verified that by engaging Batt 1 only and observing the system voltage drop to 13.1v. (This is with no chargers active) Batt 2 only raised the system voltage to 13.4v. With both batteries engaged, system voltage hunted between 13.3v and 13.4v and both batteries stayed on.

The "nominal" voltage range on the nameplate for the KS2 batteries is 12.0v-13.2v anyway, so I'm going to call this OK for now. I may be leaving capacity on the table, but I'd rather underuse the battery and get some use from it than nothing at all.

I cannot believe these things left the factory with the Solar MTTP set to 14.4v, UHG set to 14.8v, and inverter/charger seemingly pumping out ~15v regardless of setting. Original owners probably traded it in after 6K miles because they were sick of the damn thing having no battery power and didn't want to mess with it.

I plan to reconfigure the UHG for 13.4v today and retest.

[GeorgeRa]

I use heat shrinkable wire terminals and had no connction issues. This is a good place to get them

https://www.delcity.net/store/Termin...hoCHccQAvD_BwE

[booster]

They may well be testing individual cell voltages and you have one going high in Bat 1. The symptoms you see would be pretty much right on if that was the case. It will be easy to tell for sure when you open up the case.


If the batteries are the originals, they could be bad, as that happens often with them from what we hear. They can be replaced with other brands a whole lot cheaper than KS2 charges. Probably get double the capacity for half the cost.


The high settings you are seeing would be typical in the past and many/most systems still use those settings, so not surprising at all. It would be interesting to find out just when KS2 got so very much more conservative with their requirements as I am pretty sure they were much higher than that for a long time.

[Richard Cranium]

Did I read this right?

2 x 200Ah Lithium modules (KS2 rev L3)
1 x ?Ah AGM battery in parallel

You have LiFePo and AGM batteries connected? all the time?
They have pretty drastically different full charge and charging profiles. If the AGM has less voltage than the lithiums they could be trying to charge the AGM all the time.
I only have 200AH LiFePOs in my rig but they are completely isolated from the starting lead acid and I get 2 + days running the fridge, WiFi, and lights before they shut off. I never run the A/C by choice, so I can't say how long that would run. Since it's an 06 I'm betting it isn't efficient and would kill 200 AH pretty quickly.