Lithium Battery Project

[Nuke-E]

I've finally gotten around to doing a little bit of writing on the lithium battery project. So far, most of it is introductory, but I've generated a voltage vs. SOC curve, put the battery under load, and looked at a few other things. I should be rolling out more info on a pretty regular basis now, as the project gets a little more attention.

 

Here's the first post: http://rvnerds.com/2016/01/18/new-project-installation-of-a-new-lithium-ion-house-battery-bank/

 

If you want to keep tabs on the project, here's the link that will get you a list of all of the posts about it: http://rvnerds.com/category/projects-and-how-tos/lithium-house-battery/

 

Comments, questions, and suggestions are appreciated--and I'll try to post back here when there's new information posted.

[Jim Gell]

Thanks for sharing this project with us, David. I will be following with interest.

[Ronbo]

I think you need your own page on the forum for this project

[Broncohauler]

Good reading thank you

[Nuke-E]

Just added another section. Don't be shy about asking me questions or picking apart my logic! I'm behind on writing things up still as far as where the project stands today, but if I've done (or can avoid doing) something in a less than ideal manner, I want to hear from you!

 

I promise to include more pictures as the hardware starts to come together too.

[RickW]

Look forward to learning more as I plan to apply the concept to both my RV and office.

[Larry&Donna-AK]

Thank you. Waiting to read more.

[Nuke-E]

I'm working on it!!! I should have a post up about disassembling the pack early this afternoon, and another with some charge/discharge data later today.

 

I made the mistake of mentioning the project in a Facebook group--everyone there wants to talk about all of the battery fires with Volts. Of course, there has only been one documented fire, 3 weeks after a crash test.

[Star Dreamer]

I thought you needed an Arc to go with the Volt to start a fire. But then a fire on a wooden boat would not be a good thing.

 

Very nice reading. I will be curious on how much space and where to locate the batteries and equipment so we can design a new trailer to accommodate if possible.

[Nuke-E]

Dave,

 

I'll try to post some dimensions soon. The smallest section is about the same size as 2 T105s lined up end-to-end, but probably needs a couple inches more in height. Good news is that's 3.2kWh usable, compared to 1 from the T105s. I'm working on writing up the data from the first time charging it right now.

 

So far, no welding has occurred. Hope to keep it that way!

[Larry&Donna-AK]

Great news I'm excited see your good work, I'm all in.

Maybe I'm ahead of myself but I thought the BMS was a problematic area. Just saying, I can wait to read everything.

[rbertalotto]

Well, you got my interest! BIG TIME! Great idea using a Volt battery pack. Wish I knew how to subscribe to your site so I don't miss anything.

 

I just recently read another blog about a full timing couple that are "nerds" that went the Lithium route with reasonable results. But it sounded like they were two or three years early. Technology has improved in the last two or three years.

 

I have 10.5Kw on my roof at home from Solar City. This fall they are installing a 8K battery pack in my garage so I can get rid of my backup generator. Once they get that huge factory they are building out in Reno up and running I hope they offer all kinds of Lithium options.

 

The new Porsche used a Lithium battery that costs something like $1200. I've not researched it but I understand it is quite small and very light.

 

Standing by for more updates on your system.....Thanks for sharing!

[Star Dreamer]

After your post about a T105 battery, I figured I better do some research as I didn't know what you were talking about since I have all 12 volt batteries.

At least I figured out that a T105 us a 6 volt golf cart battery.

 

I see that the Volts battery pack is T shaped and is also heated/cooled to maintain life expectancy. Do you plan to keep the same shape configuration and plan to run lines for heating and cooling the pack?

[Nuke-E]

I've broken down the pack into 3 sections (the top of the T is one, and the long part of the T is broken into 2 sections). I've waffled back and forth between mounting the batteries "outside" between the frame rails at the back of my rig and putting them "inside" in a cabinet in the bedroom. Inside, heating and cooling would be unnecessary with the charge and discharge rates in RV use. Outside, I'd be hooking it up with a heat exchanger and pump, and use the water tank inside as a heat source/sink.

[Jack Mayer]

All the Lithium chemistry's I'm aware of for RV use require the environmental control that is best done inside the rig....It is easy that way if you are fulltiming. Where it gets tricky is if you are not and the rig gets very cold. In that case....no charging. I'd be inclined to put them inside...way easier.Assuming you have the space.

[Nuke-E]

All the Lithium chemistry's I'm aware of for RV use require the environmental control that is best done inside the rig....It is easy that way if you are fulltiming. Where it gets tricky is if you are not and the rig gets very cold. In that case....no charging. I'd be inclined to put them inside...way easier.Assuming you have the space.

 

Exactly. I'm going to have a disconnect for the battery that will open on low or high voltage, and low or high temperature as a safety measure, and additional disconnects for the charging (over voltage and/or low temperature) and load connections (under voltage).

 

The good news is that we know how much power is necessary to keep the battery warm enough for charging in all of the external environments GM considered--600W. Worst case, the liquid loop on the battery pack could be connected to a hot water source (via heat exchanger) to warm it for charging, and 600W is well less than the 1800W or so of the electric elements in our water heaters. But putting it in heated/cooled space is definitely easier, and since that's what's expected for the inverter/charger, it makes sense.

 

Putting them inside would run afoul of the ANSI/RVIA low voltage standard, but at 48V, that standard isn't applicable. ;-)

[Nuke-E]

Just added a post with a state of charge curve. http://rvnerds.com/2016/01/21/charging-a-48v-volt-battery-section/

[rbertalotto]

Nuke...Have you been following this blog

 

http://www.technomadia.com/lithium/

 

He seems to be a real pioneer in the "L" world.

 

[Nuke-E]

Yes, I have. I initially started with a similar approach (except higher voltage), but I really think the Volt battery is a much better deal and will end up being a simpler installation in the end.

[rbertalotto]

I agree...I think you are on the right path.

[Broncohauler]

So if temperature is such a be deal,how does GM handle it with the volt in cold climates?

[Nuke-E]

GM actually runs antifreeze through the pack, part of the same system that cools the inverter, and there's a 600W heater to warm the battery. It doesn't charge until the battery is warm enough. I'm not sure if they use the heater at other times (where it'd be less sensitive to being cold) or just when charging.

[Star Dreamer]

For us snow birds that aren't smart enough to leave before it gets cold, I wonder if we could plumb a small engine block heater into the antifreeze system that we could plug into the same circuit that we would normally us to keep batteries charged during non use. It may need to be thermostatically controlled so once it was warm enough it would shut off and turn on when too cold.

 

For normal use, would locating it in the basement of the 5th wheel be OK?

[Nuke-E]

I think you'd be fine. I'm of the opinion that an over/under-temperature shutoff is necessary, both for safety and to protect the battery, which will keep you from getting into too much trouble. One thing to keep in mind is that these batteries aren't significantly different from what you have in cell phones, laptops, etc.--those things don't like temperature extremes either, but we still use them over a pretty wide range of environmental conditions. Of course, I've also had both a phone and laptop battery swell up while on a hot bus ride. Both were connected to power when it happened, and even though the batteries almost doubled in thickness, they still worked fine for the month or so it took me to get replacements.

 

Even the lead acid batteries we all have now suffer degradation in temperature extremes, but there's not much opportunity to protect them in a vented compartment, and even under the best circumstances, if you're using them, they might see 10 years before replacement. I think with the proper care, these lithium batteries should be able to go much longer, and that's at least part of the justification for spending the money.

[Randyretired]

In our business we use lithium ion batteries in a wide range of temps. However, we use a solar charge that is way less than the rated max and the discharge is way less than the max rating. Many of these batteries are still performing very well even 7 years later. It seems that if the loads and charging are modest the temps are not as critical. This fits very well with solar applications. Running a few lights at cold or hot temps do not seem to cause problems either.