Lion Energy Lithium Batteries - A No-brainer

[Jim Blackwood]

Well OK, but if you have a propane fridge, propane stove, propane heat and propane water heater that only leaves lighting and entertainment. Surely a single solar panel and lead batteries could handle that?

Jim

[richard5933]

We have propane heat which keeps thing toasty, but it still needs 12vdc for the fan. Fridge is 12vdc compressor unit which sips power, but it still needs power. Lights and entertainment are what they are. Fans for warmer weather and water pump, of course.

A single one of our 180-watt panels will only provide 15 amps, and that's if it's at 100%. Start considering passing clouds, shorter days, and lower sun and the number drops considerably.

There simply isn't enough time in a non-summer day to fully recharge FLA batteries off solar unless you have lots of it. Our three 180-watt panels will usually keep up fine during peak sun season, but not at other times. Especially not if you throw in a really cloudy or raining day.

I'm not running out to buy lithium today, but I can see where the advantages of lithium will be much more attractive as the prices continue to drop.

[dtcerrato]

What Jim said that's why we're going with 500 watts @ 29 amps on the roof. That and the inverter otr will free up our percentage of genny use drastically.

[freds]

Why aren't people buying used Tesla Model S battery packs ?  They sell for about $1200.   24V nominal.  5.2 KWHr *useable*.

I plan to pick up 2 of them this fall.

They have a pretty safe chemistry.  No need to monitor temps during discharge for typical bus loads.  You have to carefully monitor voltages though.  Discharge too deep and you'll kill them.   Ditto on overcharging them.  Can't charge them below freezing, but all lithium chemistries are like that.   

I'm going to test them as the chassis battery as well.

I don't recommend Tesla modules as chassis batteries; as they are nominally 24volts; but run a lower voltage range of 18-24 at 80% capacity. Most lead acid batteries are run in a 21 to 27 volt range.

I did a fair amount of posts in my bus thread on my use of two Tesla battery modules with a SimBMS. Going to make a second pass at documenting it when I finish my house electrical system redesign.

Not to say that using them as start batteries couldn't be done, but there are real challenges from a alternator charging perspective for lithium batteries, so definitely not plug and play.

In my case I have two major components which are the DC refrigerator and the diesel boiler for the hydronic system that don't like the Tesla battery voltage range. So the solution was to add a dc to dc charger in the mix to constantly low level float charge the 24V and 12V lead acid batteries in the bus that these devices draw off of.

In an emergency I do have a point in my system where it is easy to jumper the Tesla battery into the start battery system for an emergency start if it should be needed.

[Jim Blackwood]

The complexity worries me. It's been obvious for a long time that electrical systems run on smoke and sometime it's a real challenge to keep it from getting out. But Electronics work on Witchcraft. Just ask any Programming Engineer. And computers? Don't get me started. Computers have mental illnesses and sometimes complete insanity. All you have to do is consider how they were developed compared to organic intelligence. First there was a cell that learned to contract. Then there was a cell that could make an electrical charge. They got together and made babies that willy-nilly got ever more complex until we had people and considering that big brain had no plan as it was developed, there's just layer upon layer of redundancy and bizarre dead ends so it's no surprise there is a certain amount of insanity in the mix. Computers? Well, take Windows for example. Same general pattern. Result? Insanity. Or Java, now there's one that pretty much started out with mental illnesses.

So I have to ask myself, "Self, with the level of aberrance already aboard the bus, do you REALLY want to add more?"

Jim

[windtrader]

So I have to ask myself, "Self, with the level of aberrance already aboard the bus, do you REALLY want to add more?"

Having worked with computers almost from the beginning of time, did NOT work on tube computers, but did start in the business pushing cartloads of punchcards to load into sorters and decollators with hand wired logic control boards, I still feed off anything technology.


You have to be crazy and have much passion to do this stuff and definitely not for everyone. Just being a busnut tribe member required a fair bit of insanity and passion. Not simply flavoring bus with technology but mixing and integrating old and new is the epitome of insanity, only found in the last undiscovered tribe on the planet. lol


Start stocking up on tomatoes so after Gary publishes the DIY lithium battery article(s), you' have boxes of rotten tomatoes for ammunition. lol

[someguy]

I don't recommend Tesla modules as chassis batteries; as they are nominally 24volts; but run a lower voltage range of 18-24 at 80% capacity. Most lead acid batteries are run in a 21 to 27 volt range.

It is a little bit low but I think things will still work.

Telsa battery packs are 6S74P.  Cell voltage is 3.8 nominal, 3.3 shut off and 4.2V max.

6 x 3.3V = 19.8V at cut off.  Seems low for a 24V system except that 24V batteries drop to 20V or less under hard starting conditions due to the Peukert effect.  Tesla packs have very low internal resistance and drop very little.  I'm guessing there wouldn't be a lot of difference, even with a mostly discharged Tesla pack.

6 x 3.8 nominal = 22.8V, which is still a little low, but should work.  OCV at 10% SOC on a 24V system is 23V, but under load it would be 21-21V.  The bus should still run fine at the voltage.

6 x 4.2 fully charged = 25.2V, which is fine for running a bus.  Due to lack of Peukert effect, I suspect this will turn the starter over really well.

In reality the Tesla battery only gets used for starting the bus.  Once the engine is running the alternator(s) will bump the system voltage up to 24V charging levels and power whatever is needed.    The Tesla battery would only only supply the chassis with power when the chassis voltage dropped below the Tesla pack voltage.

A large diode will be needed to isolate the Tesla pack from chassis voltage when the engine is running.  And a BMS will be needed to handle charging the Tesla battery.

I'll report back what I find when I have it running.  We want to use Tesla packs to power some stationary engines too.  Testing will commence this fall.

In my case I have two major components which are the DC refrigerator and the diesel boiler for the hydronic system that don't like the Tesla battery voltage range. So the solution was to add a dc to dc charger in the mix to constantly low level float charge the 24V and 12V lead acid batteries in the bus that these devices draw off of.

I'm surprised those are 24V loads.

[someguy]

Not to say that using them as start batteries couldn't be done, but there are real challenges from a alternator charging perspective for lithium batteries, so definitely not plug and play.

Low pass filter in front of the BMS ? 

In an emergency I do have a point in my system where it is easy to jumper the Tesla battery into the start battery system for an emergency start if it should be needed.

Unless you properly isolate the Tesla battery, as soon as the engine starts and the alternator produces power, you'll see charge voltage across the Tesla battery if it is in simple parallel with the LA batteries.

Have you ever measured your starter voltage and current on LA versus Tesla ?   I'm dying to do this.

[JT4SC]

Hey guys, I just bought 2 of these AGM Pure Lead + Carbon deep cycles for $450 each at Deep Cycle San Diego.  Will be trying them out bondocking in a month or so, will let you know how they go. 

What I like about the pure lead + carbon is it minimizes the worst things about FLA batt's (long charge cycle, maintenance, plus can discharge to 30% without issue). 

https://youtu.be/Z0r65O22dvA

[someguy]

Are the "12V" lithium batteries people are buying 3S or 4S ?   They must be 4S ?  But if they are, how does a stock charging system get them to 100% SOC ?

3S = 12.6V max, 11.4V nominal.   4S = 16.8V max, 15.2V nominal.  (I'm using 3.8 and 4.2V nominal and max.)

[someguy]

The complexity worries me. It's been obvious for a long time that electrical systems run on smoke and sometime it's a real challenge to keep it from getting out. But Electronics work on Witchcraft. Just ask any Programming Engineer. And computers? Don't get me started. Computers have mental illnesses and sometimes complete insanity. All you have to do is consider how they were developed compared to organic intelligence. First there was a cell that learned to contract. Then there was a cell that could make an electrical charge. They got together and made babies that willy-nilly got ever more complex until we had people and considering that big brain had no plan as it was developed, there's just layer upon layer of redundancy and bizarre dead ends so it's no surprise there is a certain amount of insanity in the mix. Computers? Well, take Windows for example. Same general pattern. Result? Insanity. Or Java, now there's one that pretty much started out with mental illnesses.

I want some of whatever you smoke.

[richard5933]

Hey guys, I just bought 2 of these AGM Pure Lead + Carbon deep cycles for $450 each at Deep Cycle San Diego.  Will be trying them out bondocking in a month or so, will let you know how they go. 

What I like about the pure lead + carbon is it minimizes the worst things about FLA batt's (long charge cycle, maintenance, plus can discharge to 30% without issue). 

https://youtu.be/Z0r65O22dvA

What batteries did you get? When I try and search for these I'm only finding 2v and 4v models, none of which seem like they would be drop-in replacements for either 6v or 12v.

[windtrader]

I'm currently running benchmarks and sea trials on the new solar array and lithium house battery bank upgrades. On my bus, the largest consumers of AC power are air conditioner, refrigerator, and water heater.


If your goals is full off grid boondocking in a hot location, typical daily load is 26+ kW. A typical rooftop AC running 20 hours a day consumes 20 kW, the typical Norcold RV refrigerator consumes about 5kW, and electric water heater uses a couple thousand.


That alone is 26kW per day, not counting the other trivial loads from sources. Mitigating the amount of electrical generation and storage equipment can help but is going to still require a lot more than what has been mentioned here.


I am swapping the rooftops for high efficiency mini-splits. The same 20 hours of AC now consumes 8kW, swapping RV reefer for high efficiency residential unit reduces consumption to about 1kW and heating water once a day saves a thousand or so.


At 10kW a day, one can size up equipment to squeeze by. I'm adding a couple more panels to increase daily PV output to about 2.5kW allowing for charging battery bank while running AC. The 12kW battery bank supplies the AC when the PV is done for the day. The DOD is about 50%, still ensuring very solid long term battery life.


As mentioned, trials and benchmarks are underway as I type here so do not carve these figures into stone; it will change on both the demand and supply sided. The goal is to get it sorted out in the next month or two so extended stays in desert areas this winter will be very comfortable, pain and stress free.


And yes of course you can run more equipment off propane and reduce electrical demands but if the goal is propane and generator free operations, you too will be following in my wake.

[dtcerrato]

Windy we'd been following your post pretty close & even stealing it a bit on other forum to show our solar progress which in fact is just a fraction of what your accomplishing! Yes we still have on board genny(s) & lots of propane so we'll be far from total solar but am looking forward to the increased freedoms & independence  the upgrades will afford us. In your case LET THERE BE SUN! 

[someguy]

If your goals is full off grid boondocking in a hot location, typical daily load is 26+ kW. A typical rooftop AC running 20 hours a day consumes 20 kW, the typical Norcold RV refrigerator consumes about 5kW, and electric water heater uses a couple thousand.

You mean KWHrs, right ?  Not KW.  KWHrs ?

KW is power.  KWHr is energy.