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Old 08-11-2020, 01:54 PM   #1
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EMS changes with Lithium upgrade

I am completing upgrades on my Interstate 2014 including 400 Ahr lithium battery bank, 300 watts solar and a 2000 w Inverter/Charger. I now wonder if the BMS is necessary any longer. This of course is the current sensing addition that switches off a couple of circuits if too much current is being demanded. Any thoughts from those of you who have recently upgraded your systems?
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Old 08-11-2020, 04:16 PM   #2
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You are apparently asking about the Power Control System, not the Battery Management System. They are two different things. BMS simple connects the batteries when appropriate.

I'll leave the answer to someone who has done the conversion, but the Power Control System is still critical when you are plugged into 30 amp service or running on generator.
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Old 08-11-2020, 04:57 PM   #3
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And that is exactly why I believe lithium isn't ready for prime time in a trailer application. A "real" BMS does much more than that....like liquid heating and cooling of the battery, among other things.
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Old 08-11-2020, 06:11 PM   #4
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Doesn't the lithium batteries come with built in BMS? Mine did.
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Old 08-11-2020, 06:28 PM   #5
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Is the BMS aka the BIM? I removed the BIM and isolator running the alternator to a Sterling dc to dc charger.
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Old 08-11-2020, 09:24 PM   #6
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The power management system is on shore power or generator side of the system, so lithium vs lead acid for the 12v side is neither here nor there for that component. You would keep this system in any event. Like Heckler56, I also removed the BIM which sometimes connects the chassis battery to the house batteries and put in a sterling dc to dc charger, in my lithium conversion.
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Old 08-12-2020, 01:27 AM   #7
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WOW, i blew that post. I meant to address the Power Control System as Pahaska pointed out! I regret the confusion that my post has caused. The BIM (Battery Isolation Manager) will be replaced as it appears not to be working anyway. My new batteries do have a BMS (Battery Management System) built in that reports the current SOC of the batteries. It is the Power Control System and its related current sensor that I mean to question. While making the other changes to the system I discovered that microwave circuit connection to this sensor was fried. The result of perhaps a loose connection. Appears that I may have to replace the sensor if that part of the system is still necessary.
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Old 08-12-2020, 09:29 AM   #8
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And that is exactly why I believe lithium isn't ready for prime time in a trailer application. A "real" BMS does much more than that....like liquid heating and cooling of the battery, among other things.
Hi

If that is your standard for a BMS ( "liquid heating and cooling" ) then roughly 99.9999% of all systems out there are "doing it wrong" .....

Bob
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Old 08-12-2020, 09:47 AM   #9
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Hi

If that is your standard for a BMS ( "liquid heating and cooling" ) then roughly 99.9999% of all systems out there are "doing it wrong" .....

Bob
Believe me, the BMS in my BMW I3 does exactly those things, not only when the HV battery is being charged, but when it is being used in hot or cold conditions. This is true of just about every EV on the road with the exception of the early Nissan Leaf and maybe the smart. Nissan tried to get away with no controls and failed miserably.

I charged in the hot garage yesterday afternoon and the cooling system automatically turned on to cool the HV battery. I normally automatically charge from 11:00 PM to 7:00 AM when the electric rates are the lowest and the temperature low enough that cooling is not needed.
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Old 08-12-2020, 10:37 AM   #10
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Believe me, the BMS in my BMW I3 does exactly those things, not only when the HV battery is being charged, but when it is being used in hot or cold conditions. This is true of just about every EV on the road with the exception of the early Nissan Leaf and maybe the smart. Nissan tried to get away with no controls and failed miserably.

I charged in the hot garage yesterday afternoon and the cooling system automatically turned on to cool the HV battery. I normally automatically charge from 11:00 PM to 7:00 AM when the electric rates are the lowest and the temperature low enough that cooling is not needed.
Exactly. My training and experience comes from the automotive world. Those manufacturers who chose air heating and cooling and not providing for multiple temperature sensors per pack, among other things, experienced premature battery degradation. Those with liquid cooling plates between cell packs did not.
My problem with rv applications is not so much the battery itself, but the radically cyclic extreme (for a lithium) temperatures in which they live, and are used, with no provision for constantly maintaining an internally acceptable temperature window.

(I was trained on Volt and Bolt and am a Volt owner)
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Old 08-12-2020, 11:04 AM   #11
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I, like Pahaska, have caught my Volt heating and cooling the battery of it's own volition. If the car has not been used for a time and the internal battery temperature is equalized to the ambient garage temp (a minimum or 24 hours is my observed SWAG), the heated water pump will come on at about 35* garage temp. The a/c compressor will run and chill the battery coolant at about 90* garage temp.
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Old 08-13-2020, 08:55 AM   #12
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Hi

..... and .... the charge / discharge rates in an EV battery are nothing remotely similar to those in an RV setup. It's not the same thing at all ....

Bob
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Old 08-13-2020, 09:58 AM   #13
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Hi

..... and .... the charge / discharge rates in an EV battery are nothing remotely similar to those in an RV setup. It's not the same thing at all ....

Bob
In proportion to overall capacity, they may not be as different as you may suspect. Especially if your use the inverter for some higher amperage items. Barring the level 3 and above charging rates of cars.

But internally generated heat from discharge rates and charge rates are only half the story. My trailer can easily be over 100* on any given summer day. So, depending on the length of the heat soak, the internal temp of the cell pack could be that high. As the above video mentions, even in the BattleBorn...only one temp sensor and it is on the top, outside of the cell pack.

Then to top things off, where do we put the batts in our trailers? Small enclosed compartments with little to no airflow.

Again, I love lithium technology, I am just not willing, yet, to spend the amount for a complete conversion into an environment which is detrimental to the battery's longevity.

BTW, while we are on the subject. Don't use or charge your charging bricks, vacuum batteries, e-bike batteries, etc. immediately after heat soaking all day in the RV or TV. Also, always try and park your e-bikes in the shade or remove the batt and take with you in a backpack or something. Those suckers get really hot in the sun.

I love the latest and greatest, but there are some valid decision points here.
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Old 08-14-2020, 07:32 AM   #14
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In proportion to overall capacity, they may not be as different as you may suspect. Especially if your use the inverter for some higher amperage items. Barring the level 3 and above charging rates of cars.

But internally generated heat from discharge rates and charge rates are only half the story. My trailer can easily be over 100* on any given summer day. So, depending on the length of the heat soak, the internal temp of the cell pack could be that high. As the above video mentions, even in the BattleBorn...only one temp sensor and it is on the top, outside of the cell pack.

Then to top things off, where do we put the batts in our trailers? Small enclosed compartments with little to no airflow.

Again, I love lithium technology, I am just not willing, yet, to spend the amount for a complete conversion into an environment which is detrimental to the battery's longevity.

BTW, while we are on the subject. Don't use or charge your charging bricks, vacuum batteries, e-bike batteries, etc. immediately after heat soaking all day in the RV or TV. Also, always try and park your e-bikes in the shade or remove the batt and take with you in a backpack or something. Those suckers get really hot in the sun.

I love the latest and greatest, but there are some valid decision points here.
Hi

In RV service, we don't run discharge rates over C/1. Indeed the way most of us put systems in, even *with* the inverter C/4 is about the max. When I tear apart EV battery packs I note:

1) They are set up for charge / discharge rates up in the C * 2 to C * 5 range.

2) I have yet to see *any* pack from any manufacturer that has fittings for heating / cooling. That includes packs from most of the big guys.

3) The chemistry in the EV packs often is something exotic and not the more durable LiFePO4 stuff that we use ...

Lots of variables ....

Bob
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Old 08-14-2020, 11:18 AM   #15
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Hi

In RV service, we don't run discharge rates over C/1. Indeed the way most of us put systems in, even *with* the inverter C/4 is about the max. When I tear apart EV battery packs I note:

1) They are set up for charge / discharge rates up in the C * 2 to C * 5 range.

2) I have yet to see *any* pack from any manufacturer that has fittings for heating / cooling. That includes packs from most of the big guys.

3) The chemistry in the EV packs often is something exotic and not the more durable LiFePO4 stuff that we use ...

Lots of variables ....

Bob
Well then apparently you have never torn down a GM nor a BMW pack. I'll speak for my GM training only. Volt has many(I'll refresh my memory and get the number, if you'd like) thin metal "radiators" between cell groups. They are circulated with (separate cooling system) propylene glycol which is heated or cooled electrically (a/c compressor or electric element) as required. If ambient are modest, that coolant system has a separate chamber in the front radiator and air will regulate the coolant temp.
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Old 08-14-2020, 11:25 AM   #16
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My volt has lithium manganese oxide battery cells. Not sure what you call exotic. Cruising down the highway my discharge rates are observed at C/.6 to C/1.5 Typical acceleration from a stoplight is c/2.5
Obviously, a hot rodder or very hilly terrain can produce peaks.
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Old 08-14-2020, 11:39 AM   #17
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Battle Born Lion and Victron Lion battery( just two examples) have built in BMS.
The OEM know their batteries, thus their BMS design do the best for their batteries.

Thus it's best to get an integrated BMS on any Lion batteries, vs home brew
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Old 08-14-2020, 11:43 AM   #18
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I should add that those numbers are artificially inflated from true capacity of 18.4kW to the 14.1kW " useable" capacity.
There is buffer at the top and bottom.
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Old 08-19-2020, 10:51 AM   #19
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I have the exact same system, all Victron. The inverter kicks off if you try to overload it. I’m guessing the BMS does virtually the same thing. Mine was installed by AM Solar, Springfield, OR. They would answer your question.
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Old 08-19-2020, 12:27 PM   #20
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Just because a battery has it "built in" doesn't mean it is controlled properly. The battery systems we build rely on a proper controller which is built into the vehicle. There are 2 main companies making the Isospi systems. We are currently using the ones from Nxp. There is a lot of things that need to get programmed into this interface to make it work properly. This is no small task. Most people have no idea what it takes. I'm currently working with the engineers on testing systems of these batteries.

I would have to agree with the statement that these batteries are not ready yet for the trailer market.

Currently we have designed battery systems for many auto manufacturers including the most popular ones. Sorry can't give more details than that.
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