More interesting Tesla battery news

[wincrasher]

This was posted today. I'm sure they are working on several fronts, but making this public I think they are trying to push this idea they are working hard to radically lower costs. Can't see any fault with that.

http://www.wsj.com/articles/tesla-pa...sts-1434553116

[booster]

When materials currently make up 60% of the battery cost, it is going to be pretty tough to make their 50% cost reduction without some kind of design breakthrough using substantially less expensive materials. They mention silicon instead of graphite. Just bringing vendors in house won't get them there.

Bummer with the new designs is always that they wind up back at the beginning of the learning, testing, reliability curve.

[markopolo]

They identified the problem - cost.
Coincidentally is the same problem facing most Class B van builders in growing the Class B market I think.

It's interesting that they expect/hope that 85kwh lithium batteries will cost between $10,000 and $12,500 in just 5 years.

Using that math, a 8.5kwh battery pack for a Class B at around $1,000 or a 17kwh battery pack for $2,000 would be great.

[booster]

If I am calculating right, that puts them a bit under $1.50 per AH, which is in wet cell territory. Lifeline AGMs are about $2.75 per AH. I sure do hope they are right on being able to get there.

[wincrasher]

I thought that just sheer scale of the giga factory was going to produce some significant savings. This one plant eclipses the total global production of lithium ion batteries!

So to go further by find materials or methods savings is terrific in my view.

[Boxster1971]

A few weeks ago I watched an interesting YouTube video of Professor Dahn explaining how lithium batteries eventually die. It's long but a good lecture.

http://youtu.be/9qi03QawZEk

[mlts22]

The issue isn't just lithium batteries. It is having a battery charger and discharging management system. Unlike lead-acid batteries where you can hang off whatever electrical loads, converters, solar controllers, alternators, all at once, if one doesn't have the charge/discharge rates precisely controlled on a lithium battery, then one learns the meaning of "runaway thermal expansion" pretty quickly.

Of course, this is a solved problem, or else Volts, Priuses, and ARV rigs wouldn't be possible... but it is an expensive, niche technology where you can't just stop by a RV store, buy an EMS for a lithium battery bank, and call it done.

Once this gets solved, then lithium batteries will be a lot more useful for RV-ing.

[Boxster1971]

You are correct it's not just the batteries.
I did a lot of research on upgrading to LiFePO4 batteries. I like the power to weight they offer. Was all set to buy a 400 AH LiPO system from AM Solar, along with a new 2000 watt Magnum inverter. They were not yet ready to ship their LiPO systems when I called them a few months ago. The Magnum and my Blue Sky solar controller could be programmed to properly charge the LiPOs. But then I discovered that my Interstate only has a 4 gauge wire from the chassis battery to the house battery. I didn't think that was adequate to handle the current that could flow from my Sprinters 220 amp alternator to the 400 AH LiPO batteries. The new Interstates have upgraded this wire to 1/0 gauge.

But the issues of proper charging from Sprinter alternator and dealing with freezing temp issues made me stay with AGMs for now. Those issues can be solved, but it was too much work for me to take on right now.

[avanti]

^^^^^^^
Yes, I am feeling the same way. In another year or three, I am quite sure that there will be drop-in solutions (probably in the shape and size of an Onan genset ) that will deal with charging, heat, and physical protection--and probably at half the current cost.

[booster]

I have gone through the same drill and came to the same conclusion on the lithium-close but not quite ready yet, so we will also be going with AGM.

Boxster-I am surprised that even AGMs wouldn't pull higher than the 4ga would like, which would be about 100 amps. Our wet cells will pull that much. Do you have a separator or isolator? Isolator would drop the voltage and current quite a bit. What size fuse or breakers from the engine to the coach?

[Boxster1971]

Originally Posted by booster

...Boxster-I am surprised that even AGMs wouldn't pull higher than the 4ga would like, which would be about 100 amps. Our wet cells will pull that much. Do you have a separator or isolator? Isolator would drop the voltage and current quite a bit. What size fuse or breakers from the engine to the coach?

Yes I agree. This was not a smart wire design by Airstream, probably why they changed it to 1/0 gauge. The fuse is 125 Amp to a battery isolator. The isolator is a Precision Circuits unit which is just a Trombetta 150 Amp relay/contactor with an electronic control module made by Precision Circuits. There is minimal voltage drop across the contactor. The batteries are 2 Lifeline GPL-24T 12 Volt AGMs rated at 90 Ah each for total of 180 AH.

The systems work well since I added 400 watts of solar on the roof. It just doesn't provide the option of using the microwave on the inverter. The way Airstream set it up the 1000 watt Magnum inverter only powers the TV/DVD players. I added an additional inverter powered 120 volt outlet to the galley so I can use small appliances, like my 600 watt K-cup brewer.

[mlts22]

This might be a lucrative business:

Make a well armored box, stick a bunch of LiFePO4 cells in it, have all the cells be attached to a charge/discharge controller, and have two large terminals. Then, the controller emulates a 12 volt lead-acid battery, taking in charging current and turning it into a meaningful volt/amp amount for the LiFePO4 cells, and regulating discharge.

This way, external charges, solar charge controllers, wind turbine controllers and whatever the heck clamps onto flood lead-acid batteries will still work. The controller can also synthesize a proper voltage drop, so when it senses the lithium cells are at 50% SoC, it sets the voltage to that.

Computer science is all about having an interface that lies to something about something (for example, a SSD having cylinders and tracks) , so why not synthesize a lithium based battery that does voltage like a standard car or deep cycle battery?

[booster]

I think what mlts22 is talking about is what Smart Battery was trying to do, although we don't really know how well the actually did it.

I think we will see systems like that.

[Boxster1971]

Originally Posted by mlts22

This might be a lucrative business:

Make a well armored box, stick a bunch of LiFePO4 cells in it, have all the cells be attached to a charge/discharge controller, and have two large terminals. Then, the controller emulates a 12 volt lead-acid battery, taking in charging current and turning it into a meaningful volt/amp amount for the LiFePO4 cells, and regulating discharge....

There are plenty of those types of units out there already. Here is just one I found in my research.
http://www.balqon.com/store-2/#!/RVs...sort=priceDesc

[Davydd]

Advanced RV is doing it. BTW, it is not as simple as buying a bunch of batteries and dropping in a box from what I can tell. Balqon and AM Solar are only providing part of the solution from what I know and can tell maybe about the same if as much as Elite Power Solutions provides ARV. I admit I haven't tried to investigate what they are doing but a cursory look leaves me with what are their answers to overcharging, discharging, heat and cold weather charging? Do they address all that or do they leave it up to the buyer?

[Boxster1971]

Originally Posted by Davydd

Advanced RV is doing it. BTW, it is not as simple as buying a bunch of batteries and dropping in a box from what I can tell. Balqon and AM Solar are only providing part of the solution from what I know and can tell maybe about the same if as much as Elite Power Solutions provides ARV. I admit I haven't tried to investigate what they are doing but a cursory look leaves me with what are their answers to overcharging, discharging, heat and cold weather charging? Do they address all that or do they leave it up to the buyer?

Balqon and AM Solar have solutions for overcharging and discharging. Balqon leaves the freezing and heat to the buyer. AM Solar has told me they are working on a heater for the freezing issue and recommend installing inside the van for heat issue.

[Jostalli]

Originally Posted by Boxster1971

Balqon and AM Solar have solutions for overcharging and discharging. Balqon leaves the freezing and heat to the buyer. AM Solar has told me they are working on a heater for the freezing issue and recommend installing inside the van for heat issue.

Balqon and AM Solar offer assembled packs with a BMS and contactor, which disconnects when discharge or charge hits a set voltage. I don't know which BMS and contactor Balqon is using but AM Solar is using (not completely certain) this contactor: http://www.rec-bms.com/datasheet/Tec...et_Kilovac.pdf and the House Power BMS and cell modules from here: http://minibms.mybigcommerce.com

I'm using the same parts as AM Solar.

These methods are not ideal because the BMS should really only protect the cells, not be responsible for how they charged. The charging is where most get it wrong. These batteries do not like to be held in a fully charged state. They like to sit at 50-60%. The charge profile should really be Bulk then Off. No Absorption or Float. This is a problem since most devices sold to charge batteries have the same charge profile options: Bulk, Absorption, Float. So, you really need equipment that can be programmed to optimally charge these batteries. Charge the pack to 14V then turn off the charger.

The only thing Elite Power Solutions offers above what Balqon and AM Solar provide is a higher end BMS that supports CAN so I assume it can trigger commands to chargers, contactors, fans, heaters, etc.


In the end you don't absolutely need a BMS if your cells are properly balanced and you check cell voltage regularly. There are folks on cruisers forum.com who have packs that have remained balanced for years. At the very minimum to charge you could wire your alternator to the pack and have a fuse, battery SOC display, and switch. Keep the cells inside the van, keep it above freezing and that's it.

[Davydd]

I don't think it is as simple as keep your your cells inside a van. A van is not a conditioned space 24/7 like a house. I have experience with this issue. Try living in Minnesota and head out for a trip on February 2. I'd also like to re-emphasize this. Space inside a B is precious. An 800ah battery pack as I have would essentially kill all the under bed storage I have. That is not acceptable especially when a simple heating system works.

Everything I have read is the jury is still out about where you keep your batteries charged, but at 50-60% you are handicapping yourself for no benefit. There has been enough testing to predict 5,000 cycles if properly cared for at full charge. That's over 13 years. Even if you lose charge like Technomadia claimed they still have battery power greater than 50-60% available. Besides, how does one keep a battery charge at 50-60%?

[gerrym51]

aren't smartbatteries drop in solutions?. when i watched their video it seemed each battery case had all the devices in them-ergo the price



this might be helpful-although i think a perfect lithium battery is superior to a TPPL agm- iam now partial to tppl agm-now that i have one-is that a surprise-lol

http://www.bruceschwab.com/uploads/li-vs-la.pdf

[booster]

There is so much conflicting information out there on charging, it will make your head spin, even for wet and agm, but even worse for the lithium.

I have read a bunch of places that say to end the charge based on voltage, but how to do that accurately never seems to be explained. To check cell voltage accurately, the charger would have to be off and no loads on the battery I would think. Or you might be able to use a constant current source and stop it when the voltage got to a certain point, but again you couldn't have anything else running off the source.

Other sources say to end the charging based to the current going to the batteries from a constant voltage source, which is pretty much the same way you can do wet or agm charging, and is the best way for them. If lithium batteries react similarly to wet and agm, you would be able to stop at pretty much any state of charge you wanted. Loads wouldn't matter in this style of control, but temperature might.

If current is a good way to do the charging control, existing chargers would be able to a good job as there are some that can be programmed for voltage and current transitions, although best would be if you had one that you could also cancel the float.

The charge voltages that are recommended at also widely varying, hopefully indicating that lithium can handle a decent range without damage. If that is true, charging off the van alternator or engine generator would not need a lot of other charging stuff beyond the BMS. You could just watch the current going to the batteries on an ammeter, or automate it, and disconnect the engine from the coach when you hit the amps that give you the state of charge you want. Alternator voltages aren't all that consistent over time, so I doubt you could use it for a constant voltage ending calculation, unless you used a voltage stabilizer of some sort.

I have to agree with Davydd, that keeping the lithiums at 50-60% would not be very practical, and would require a huge bank of batteries. If you have BMS taking you off at 20% and only go to 60%, you only have capacity that is 40% of the bank size, which makes for some very expensive AH.

Personally, if I were to heat the batteries electrically, it would be with 12v heaters so you could start the engine and heat the batteries without shore power when you start out on a trip in the cold. Not everybody has a place to plug in to warm things up before they go, or if they get caught someplace cold.