My Interstate Lithium Battery Adventures

[73shark]

Originally Posted by amirm

They are not having to camp overnight with no power source in middle of nowhere.

Seriously, what is the source of this statement? I just did a search and the first hit was this document which stipulates how to use Lithium battery in all naval facilities including subs and boats: http://www.public.navy.mil/navsafece...3FList%3D8006e

"LITHIUM CELLS AND BATTERIES. The use of lithium cells and batteries in Navy systems and equipment offers the advantage of increased voltage and longer life, when compared to other power sources. Lithium batteries can provide increased energy density, extremely high currents, and can discharge very rapidly when short-circuited. Although these characteristics are useful in applications requiring sustained high current, a too-rapid discharge of a lithium battery can result in overheating of the battery, rupture, and even explosion. Because of these risks, lithium batteries shall be considered hazardous at all times. The Department of the Navy has adopted a Lithium Battery Safety Program to minimize hazards associated with their use"

I have not read the rest of the doc but does not at all admonish their use.

Was based on what were told about 20 years ago about products we produced for subs.

Did some research and couldn't find anything that prohibits or allows their use on subs. Did find that laptops and watch Li batteries were OK.

[LB_3]

I'm still planning to use the solar BMS and here is one of 6 pictorial schematics I have put together. This one is my favorite. As I said, this is a pictorial schematic and omits things like fuses and any return or grounding connections. I would like feed back since my electrical background is a bit weak. If I'm missing some obvious parasitic load or if I'm missing a big fire hazard, please let me know. I'm still a couple months from having to lock this schematic down.

I don't have a cut off for the inverter because the spec sheet claims it only draws 4 mA when turned off. I like the large solid state relays discussed either in this or one of the battery threads but since one of my design goals is to eliminate the parasitic loads, I'm hoping there won't be much need for those space heaters.

The total parasitic load in this schematic when the system is turned off is about 25 mA. On a full battery, that would take over a year to discharge. I did however add a switch on the battery ground to assist in maintenance and long term storage.

I'm not really sure if the Sterling battery to battery charger on the left is really necessary or if I could just get away with a battery isolator. My main hesitation is where to locate that box since it is preferable to have them close to the alternator and chassis battery. Unfortunately I don't think it can go under the hood and there isn't really any room under the driver's seat.

On the AC side, I'm a bit conflicted about reusing Airstream's automatic transfer switch vs a manual three way switch. I put the refrigerator upstream of the inverter because I don't want to ever accidently power the 2-way fridge's resistive heating element using the battery.

[lewster]

Originally Posted by LB_3

I'm still planning to use the solar BMS and here is one of 6 pictorial schematics I have put together. This one is my favorite. As I said, this is a pictorial schematic and omits things like fuses and any return or grounding connections. I would like feed back since my electrical background is a bit weak. If I'm missing some obvious parasitic load or if I'm missing a big fire hazard, please let me know. I'm still a couple months from having to lock this schematic down.

I don't have a cut off for the inverter because the spec sheet claims it only draws 4 mA when turned off. I like the large solid state relays discussed either in this or one of the battery threads but since one of my design goals is to eliminate the parasitic loads, I'm hoping there won't be much need for those space heaters.

The total parasitic load in this schematic when the system is turned off is about 25 mA. On a full battery, that would take over a year to discharge. I did however add a switch on the battery ground to assist in maintenance and long term storage.

I'm not really sure if the Sterling battery to battery charger on the left is really necessary or if I could just get away with a battery isolator. My main hesitation is where to locate that box since it is preferable to have them close to the alternator and chassis battery. Unfortunately I don't think it can go under the hood and there isn't really any room under the driver's seat.

On the AC side, I'm a bit conflicted about reusing Airstream's automatic transfer switch vs a manual three way switch. I put the refrigerator upstream of the inverter because I don't want to ever accidently power the 2-way fridge's resistive heating element using the battery.

LB_3,

If I may comment?

Nice work! You don't necessirally need that Sterling DC to DC unit. The newer Interstates use a solenoid based battery isolator from Precision Circuits that seems to work well for lead batteries, but I believe that the voltage set points are not really suitable for alternator charging of lithiums as the voltage of same is significantly higher than lead types and they dos not exhibit voltage drop. The result will be a one way charging system to your coach battery rather than the intended 2-way system.

You could look at Victron's answer, as they have a great deal of experience in the marine industry where alternator charging is the norm on large power boats. Look at their Cyrix-Li-ct isolator that we use for their lithium systems. https://www.victronenergy.com/upload...n-230-A-EN.pdf

Also, from my experience with the Interstate and Airstream trailers, there have been many failures reported from the Parallax auto transfer switch. There are better quality units available for a 30 amp coach like the Progressive Dynamics unit.

With a lithium system, why not dump your 3-way inefficient gas/absorption fridge and go with a DC compressor (Danfoss) marine unit. I have installed many of these and they receive universal praise for the operational characteristics of them.

Are you showing that shunt on the positive side of your circuit? I have never seen one used there......only for all negative DC loads....

Hope this helps a bit in your lithium quest!

[LB_3]

Originally Posted by lewster

LB_3,
If I may comment?

Absolutely, I was counting on it.

Originally Posted by lewster

Are you showing that shunt on the positive side of your circuit? I have never seen one used there......only for all negative DC loads....

Hope this helps a bit in your lithium quest!

Yes, the shunt is on the positive. I don't really like it there either but the BMS I'm hoping tracks any loads passing through it and uses the shunt to track the loads external to the BMS. If the shunt were in the proper place, it would double count the current through the BMS.

The software for the BMS is open source and from my quick peak at the code, it looks pretty easy to update the calculations to make current draw the difference instead of the sum of the two currents. Unfortunately, just the thought of trying to successfully compile and install the software makes me dizzy so I've put most of my energy in trying to find a small plastic project box to enclose the shunt.

I'm not opposed to a DC fridge and love the idea of our propane lasting months instead of a two weeks. But our current fridge works and is relatively new so I don't want to risk our most important appliance during the shake down phase of this project.

Thanks for the input.

[FlyFishinRVr]

Originally Posted by lewster

With a lithium system, why not dump your 3-way inefficient gas/absorption fridge and go with a DC compressor (Danfoss) marine unit. I have installed many of these and they receive universal praise for the operational characteristics of them.

Lew, along the lines of DC compressors being more efficient, do they make DC air conditioning units for RVs, or ones that can be modified to work in a RV? It seems the two biggest draws on the batteries are the refers (which are readily available in DC, like the new AS Interstates) and the A/C. For battery operation I can definitely see people switching to DC refers if they don't already have them, but so far I've not seen any chatter about DC A/C units...... ???

[lewster]

Originally Posted by FlyFishinRVr

Lew, along the lines of DC compressors being more efficient, do they make DC air conditioning units for RVs, or ones that can be modified to work in a RV? It seems the two biggest draws on the batteries are the refers (which are readily available in DC, like the new AS Interstates) and the A/C. For battery operation I can definitely see people switching to DC refers if they don't already have them, but so far I've not seen any chatter about DC A/C units...... ???

WHAT A GREAT CONCEPT!!!!! AFAIK, I have never seen this done.

Now see what you did!!!!!! I'm going to have to resurrect an old roof unit with a blown compressor and see what it will take for pure DC operation.

Any Go Fund Me investors???? ;-))


Lew Farber

[Boxster1971]

There has been an ongoing discussion on the Sprinter-Forum about an under mount split A/C system that is powered by coach batteries.
http://www.sprinter-source.com/forum...ad.php?t=50729

A system of this type is available on the new Roadtrek Sprinter conversions
http://roadtreking.com/next-generation-rv-air-conditioning-systems/

Roadtrek is using a system from ProAir LLC in Elkhart, Indiana. It was reported that this was an exclusive agreement between Roadtrek and ProAir.
http://www.proairllc.com/

[FlyFishinRVr]

Originally Posted by Boxster1971

There has been an ongoing discussion on the Sprinter-Forum about an under mount split A/C system that is powered by coach batteries.
http://www.sprinter-source.com/forum...ad.php?t=50729

A system of this type is available on the new Roadtrek Sprinter conversions
http://roadtreking.com/next-generation-rv-air-conditioning-systems/

Roadtrek is using a system from ProAir LLC in Elkhart, Indiana. It was reported that this was an exclusive agreement between Roadtrek and ProAir.
http://www.proairllc.com/

It looks like Pro Air sells the bits needed to make your own system Lew. Just sayin'.....

[amirm]

Originally Posted by LB_3

I'm still planning to use the solar BMS and here is one of 6 pictorial schematics I have put together. This one is my favorite. As I said, this is a pictorial schematic and omits things like fuses and any return or grounding connections.

Actually, these bits comprise a significant portion of re-wire. Optimizing them and minimizing wiring and switches is important.

I would like feed back since my electrical background is a bit weak. If I'm missing some obvious parasitic load or if I'm missing a big fire hazard, please let me know. I'm still a couple months from having to lock this schematic down.

Your biggest fire risk is during wiring! Even with careful attention, you can still short things out. This happened to me once. It was related to the stupid point below.

Airstream uses residential style, bare solid copper grounding wire. I had a positive cable touch it, sparks flew and I had myself lots of extra work . I ripped all but one of them out (there are three) and replaced them with marine (Ancor) stranded, insulated wire.

I don't have a cut off for the inverter because the spec sheet claims it only draws 4 mA when turned off. I like the large solid state relays discussed either in this or one of the battery threads but since one of my design goals is to eliminate the parasitic loads, I'm hoping there won't be much need for those space heaters.

Even though I intend to hook this up eventually I have not felt the need yet. The shut off voltage of the inverter is around 10% or so SoC (state of Charge).

On the 200 amp solid state relay, it will not work unfortunately. It is a very limited device which latches in the on state and will NOT shut off in many circumstances. If you use it, it has to just be a high side switch, powering a load. In the case of the inverter, it could work but the problem is that the inverter pulls way over 200 amps if you attempt to power the A/C with it.

Regardless, I would not use it with the inverter. Just use the ignition control and its own low voltage shut off and that should be enough together with knowing when you use it.

I'm not really sure if the Sterling battery to battery charger on the left is really necessary or if I could just get away with a battery isolator.

The solar BMS has a 100 amp current limit. The batteries can accept charge at higher level than this. Whatever device you use, it must current limit below 100 amps - Solar input. The sterling devices do this (use the battery to battery chunky square ones not the one you have pictured. These other ones have ignition control to shut them off).

My main hesitation is where to locate that box since it is preferable to have them close to the alternator and chassis battery. Unfortunately I don't think it can go under the hood and there isn't really any room under the driver's seat.

They are not waterproof, nor like to be next to a hot engine. And as you say, there is not much space around the battery under the driver seat. I managed to fit mine in next to the inverter so it worked out. Will post pictures when I do my write up one of these days.

On the AC side, I'm a bit conflicted about reusing Airstream's automatic transfer switch vs a manual three way switch. I put the refrigerator upstream of the inverter because I don't want to ever accidently power the 2-way fridge's resistive heating element using the battery.

AC management is an area by itself that you should design in as it includes the EMS. In my system I now have dual circuit breaker panels: one for loads without inverter, and one with. My inverter is now wired to power all loads except the A/C battery charger.

Speaker of A/C battery charger, where is that? When you are at an RV park, you want to run from their electricity rather than depleting the batteries and recharge using the engine or solar as that counts towards your recharge cycles/aging of the battery. Not that the sum of charge from this source, the alternator and solar must remain below 100 amps again. So whatever you use, you need to be able to have remote shut off for it and a priority system to run it or not.

I did use the AC transfer switch to select between generator and shore power. I ripped out most of the Romex wire and replaced it with marine (Ancor) wiring (couldn't untangle the generator wire so left that in there). I highly suggest while you are in there, fixing and improving all of this.

[InterBlog]

Lew, I'm maybe warming up to the Danfoss idea depending in part on how the REST of the unit is constructed. The limitation of our 3-way Dometic is that its overall construction is mediocre. The insulation is really not up to task for use in the subtropics. It is also insufficiently air tight to the point where internal condensation is a pain - it gets soaking wet in there even before the door is opened one time. These are the kinds of issues that probably would not impact users in places like California or New England but they are an ongoing aggravation to this Houstonian. I'm wondering if perhaps a marine manufacturer might have realized, "Gee, humidity is always near 100%... maybe my design ought to account for that...". As time allows, I'm going to see if any of these units are available locally so that I can check them out.

[lewster]

IB,

Take a look here: https://www.indelwebastomarine.com/u...0-big-classic/

and here:http://www.vfamerica.com/eng/seasteel.html

Both Isotherm and Vitrifirgo sell quality marine units made in Italy. I install 6-10 units/year on average with the majority being used in Airstreams. The smaller sizes (below 130 liters) is probably where you should investigate.

PM me if you have any specific questions. Happy hunting!

[pattonsr]

Lew,

Have you ever worked with a Nations second alternator for a Sprinter? The Sprinter Store in Eugene installs them along with a Balmar regulator. I read an article by AM Solar which talked about adding a second alternator for the lithium battery bank.

Barry

[amirm]

Originally Posted by pattonsr

Lew,

Have you ever worked with a Nations second alternator for a Sprinter? The Sprinter Store in Eugene installs them along with a Balmar regulator. I read an article by AM Solar which talked about adding a second alternator for the lithium battery bank.

Barry

I looked into that but then found the specs and measured the performance of the stock alternator. It is actually superb! It is rated at 220 amps and at normal idle, it was charging my AGM batteries at over 100 amps! That is more charge capacity than you get from A/C source and miles ahead of any solar.

So there is no need to mess with that.

In my current system, my charge controller pulls 120 amps from the alternator and outputs about 100 amps to my lithiums. This gets added to whatever other charge sources there are. If there is AC input, I can add another 70 amps to this using my charger. So plenty amount of charge is available.

The general rule by the way on Lithium batteries is to charge them at 0.5C which for my 300 amp battery pack is 150 amps.

[LB_3]

Amirm,

Is this the charger you're using?


I'm curious how much current your batteries will draw if you set your charger output to ~14.15 volts to match the alternator output. If the current is pretty low on a drained battery, then we can assume that the charger's boost controller is needed to get input voltage up around 14.6V If the current on a drained battery is up around 80A-100A, there may be no need to add the charger. If it charges at greater than 80A-100A then Sterling's line of current limiting relays may be a cheaper option:

http://www.sterling-power-usa.com/Pr...tiveRelay.aspx

[lewster]

Originally Posted by pattonsr

Lew,

Have you ever worked with a Nations second alternator for a Sprinter? The Sprinter Store in Eugene installs them along with a Balmar regulator. I read an article by AM Solar which talked about adding a second alternator for the lithium battery bank.

Barry

Hi Barry,

No, I haven't done an aux. alternator yet but after experiencing a faulty, leaking aux. transmission cooler that Sprinter Store installed a couple of years ago on my 2011 Sprinter and then gave me the run-around when I wanted to come back to have them fix it, I would NOT have them touch my rig again!!! Found that they not only used the wrong type of fittings on the new cooler, but they were welded to the copper tubing instead of flared on and tried to cover it by using gobs of pipe dope and teflon tape........VERY AMATEUR JOB!!!

Just had it replaced with much better quality components!!

If going for a second alternator, I would probably use a complete Balmar system though.

[FlyFishinRVr]

Originally Posted by lewster

Hi Barry,



No, I haven't done an aux. alternator yet but after experiencing a faulty, leaking aux. transmission cooler that Sprinter Store installed a couple of years ago on my 2011 Sprinter and then gave me the run-around when I wanted to come back to have them fix it, I would NOT have them touch my rig again!!! Found that they not only used the wrong type of fittings on the new cooler, but they were welded to the copper tubing instead of flared on and tried to cover it by using gobs of pipe dope and teflon tape........VERY AMATEUR JOB!!!



Just had it replaced with much better quality components!!



If going for a second alternator, I would probably use a complete Balmar system though.

Lew, to amirm's point, is there really any need for a second alternator given the 220A output of the stock unit? Seems if the stocker can get the job done, why mess with adding another one? What am I missing? The only thing I can see adding is the MB idle kick up switch to keep the emission crap happy and the juice flowing.



My eASI of the future won't have a genny or propane tank and will have a 100% electric house, with everything DC, no inverter, and increased diesel capacity.......

Sent from mTalk

[amirm]

Originally Posted by LB_3

Amirm,

Is this the charger you're using?

Hi LB. Can't see the above message but this is the one I used: http://www.sterling-power-usa.com/BB...r12vto12v.aspx

Note that the amp rating they specify is input current, not output.

I'm curious how much current your batteries will draw if you set your charger output to ~14.15 volts to match the alternator output. If the current is pretty low on a drained battery, then we can assume that the charger's boost controller is needed to get input voltage up around 14.6V If the current on a drained battery is up around 80A-100A, there may be no need to add the charger.

The charger is current limited to its maximum so can't use it to test the theoretical, direct short connection. Without the long interconnecting cable, in theory it will suck the Alternator dry, potentially causing damage to it. But in reality there is a 20 foot cable so that could provide the current limit through its voltage drop. Have not been daring enough to try it and potentially kill the alternator in the middle of RV season

If it charges at greater than 80A-100A then Sterling's line of current limiting relays may be a cheaper option:

http://www.sterling-power-usa.com/Pr...tiveRelay.aspx

It is a big challenge sorting through these devices to figure out what they really do. Here is a bit from the manual:

"Current limiting Model, what does it do that is different
from the conventional version ( how does it work ).

The current limiting model has 6 x 14 amp thermal PTC
fuses connected in parallel with each relay, these
thermal fuses allow a relative high short burst of current
but heat up causing high resistance through the fuse ,
this in turn makes then heat up until they shut down
from about 14 amps to about 0.5 amps, the software
can sense the high deferential voltage and knows that
the unit has been overload, the software then open
circuits the relay at a low safe 6 amps load and not at a
higher 200 amp load ( based on the 70 amp model ) in
order to speed up the cooling of the fuses ( to allow the
unit to re activate ) the unit allows 5 mins for the fuses
to cool before re engaging the system again, if the unit
trips again and again then the there is either a major
fault with the circuit or the CVSA has been under
specked."

From what I can tell, it considers overcurrent a fault condition and will keep shutting off. This would sharply reduce the amount of charge and I don't know how many cycles it can tolerate before the fuses go bad. It is not a true current limiter based on that description.

Also, the unloaded output of the alternator is about 13.6 from what I recall. This would mean a per cell voltage of 13.6/4 = 3.4 volts which is too low for the cells unless you want to be super conservative. I charge mine to 3.65.

[lewster]

Originally Posted by FlyFishinRVr

Lew, to amirm's point, is there really any need for a second alternator given the 220A output of the stock unit? Seems if the stocker can get the job done, why mess with adding another one? What am I missing? The only thing I can see adding is the MB idle kick up switch to keep the emission crap happy and the juice flowing.



My eASI of the future won't have a genny or propane tank and will have a 100% electric house, with everything DC, no inverter, and increased diesel capacity.......

Sent from mTalk

FF,

The only alternator experience that I have had was on a 2016 Interstate that I had just placed an 800 amp/hour lithium bank and Magnum MSH3012-M inverter/charger.

During the final orientation for the client, I turned on the roof A/C and ran it from the battery/inverter combination only with no other charging input. Just to see what would happen, we then started the engine and watched the battery monitor for the net amperage draw from the batteries.

Before the alternator was engaged, the A/C was drawing around 155 amps from the lithiums. After starting the engine (left at normal idle speed) the net draw was reduced to 90-95 amps, which meant that he alternator was supplementing the A/C draw with 60-65 amps thru the Precision Circuits BIM that was left in place. We did not increase engine speed during the exercise.

I will definitely check the alternator's amperage input on the next Interstate lithium installation that I do (have one coming up in a few weeks) and will test the alternator's contribution to the lithiums under a variety of conditions, including driving down the road and will report back with those hard numbers.

[pattonsr]

This post was from sprinter-source.

http://sprinter-source.com/forum/sho...&postcount=100

[lewster]

Originally Posted by pattonsr

This post was from sprinter-source.

http://sprinter-source.com/forum/sho...&postcount=100

Thanks for the link! It agrees with what I saw happening in that lithium installation. Perfect!!