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Old 01-27-2018, 11:00 AM   #21
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Most beach houses are not subjected to movement from wave action over long periods of time.

For beach houses that are subject to wave action, the duration is fairly short and the Powerwall will probably be damaged.
Electric cars, motorcycles and bicycles ARE subject to movement and Tesla seems to be able to make them work......
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Old 01-27-2018, 11:47 AM   #22
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What about the float charge, doesn't that last for several hours of light genset usage? In my experience that period is much shorter with lithium batteries.
Yes, so for my hypothetical system described I added a 200 watt solar panel to use to top up the last 10%.

Lithium batteries need little or no top up.

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Old 01-27-2018, 12:16 PM   #23
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I think that how the batteries will be used is an important factor in the decision of what type (and how many) of battery (lead, AGM, lithium) would be good for any project.

One could build the case of using lead, AGM, or lithium, depending on the individuals use of the battery. If one has a huge engine room with lots of unused space perhaps lead makes sense. On the other hand, AGM require less maintenance. Lithium makes sense if one requires a lot of energy and have little space.

Checking batteries at Smartmarine.com, a 12V 150 Ah lithium ion battery, group size 8D, weighs 65 lbs. Three of these batteries would give one about 400 Ah available. The cons of course, is the price. At $1900 each, three batteries would cost about $5700. Whether this makes, of course, depends on one's wants and needs.

That is what makes this an interesting thread, in that the OP is trying to identify if the Telsa Powerwall is an option for marine use. The Powerwall 2.0 is price at $5500, with 2000 Ah. It makes for an interesting option to investigate.

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Old 01-27-2018, 04:36 PM   #24
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If the goal is to not run a generator while using AC, the right inverter and battery bank works. I don't see the extra cost of lithium batteries worth it. I still use Dyno 8dc batteries and go several days at anchor w/o running a generator. I have electric incinerating toilets, a dd reefer, 2 freezers and almost all the lights are ac. I usually get 8-10 years out of Dynos. I time charging to when making water is necessary.
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Old 01-27-2018, 04:38 PM   #25
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I am going to look at a boat with a 34kw generator and mostly 120vac systems. The boat seems to be setup as a commercial vessel where the genset starts up when it leaves the dock and shuts down when it gets back. It seemed that the Powerwall would be a viable alternative to lead-acid allowing full systems service at night with a quiet boat. 34kw should allow a rapid recharge with an appropriate charger......?
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Old 01-27-2018, 06:13 PM   #26
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I am going to look at a boat with a 34kw generator and mostly 120vac systems. The boat seems to be setup as a commercial vessel where the genset starts up when it leaves the dock and shuts down when it gets back. It seemed that the Powerwall would be a viable alternative to lead-acid allowing full systems service at night with a quiet boat. 34kw should allow a rapid recharge with an appropriate charger......?
I'd wait and see your actual usage and circumstances before trying to figure out a better solution. That's not necessarily setup as a commercial vessel. We never run without generator.

I see the possibility of great benefit from Powerwall really coming when you're able to power it with solar.
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Old 01-27-2018, 11:24 PM   #27
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A quick read of the PowerWall "literature" yields the following that I think is relevant to this discussion:

- It's 13.5kwh of power, not 24kwh.

- The design is totally based around a grid-tied power system

- It cannot currently be charged by a generator. They hint that it might be a future feature, but no dates or promises.

- It cannot be charged from a DC power source, so no charging from engine alternator(s), and no direct charging from solar.

- To charge from solar, the solar needs to go to a grid-tied inverter which feeds the grid which feeds the PowerWall to charge. That's an impractical arrangement on a boat, and reflects the grid-tie centric design.

- Purchase requires a site survey and application approval. They don't say anything about mobile applications, but I suspect any attempt to purchase for use on a boat wouldn't make it past the screening process.

Bottom line is that there is currently no fit for a boat, or any other mobile application. There might be some day, but not now.
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Old 01-27-2018, 11:45 PM   #28
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That's disappointing, I had hoped that a modular, off the shelf system had become available, one with a large deep pocketed company behind it. Perhaps in a year or two........
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Old 01-28-2018, 05:00 AM   #29
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A quick read of the PowerWall "literature" yields the following that I think is relevant to this discussion:

Bottom line is that there is currently no fit for a boat, or any other mobile application. There might be some day, but not now.
Good points
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Old 01-28-2018, 09:00 AM   #30
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That's disappointing, I had hoped that a modular, off the shelf system had become available, one with a large deep pocketed company behind it. Perhaps in a year or two........
Victron has a complete, integrated LiFePo4 system, and they are a significant company that has been around for a lot longer than Tesla. I'm working with a friend currently to utilize this system in a boat he is building. It's really quite interesting because pretty much everything you ever learned about batteries, charging, operation, and how to build a good DC power system no longer applies, and is probably the wrong thing to do. You definitely can retrofit these into existing boats, but to do it right requires quite a few changes. And if you are starting from scratch, there are a bunch of things you just approach differently.
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Old 01-28-2018, 09:21 AM   #31
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I'm working with a friend currently to utilize this system in a boat he is building. It's really quite interesting because pretty much everything you ever learned about batteries, charging, operation, and how to build a good DC power system no longer applies, and is probably the wrong thing to do.
Would *love* for you to expound on this. Either here or a meaty blog post works I've really enjoyed going through your archives and have learned a lot. Thank you.
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Old 01-28-2018, 09:25 AM   #32
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Would *love* for you to expound on this. Either here or a meaty blog post works I've really enjoyed going through your archives and have learned a lot. Thank you.
I will. I've just not had much blogging energy lately.
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Old 01-28-2018, 09:56 AM   #33
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The tesla powerwall is 72 volts, I believe.
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Old 01-28-2018, 10:42 AM   #34
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Specs for power wall 2

Spec sheet.
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Old 01-28-2018, 02:43 PM   #35
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The tesla powerwall is 72 volts, I believe.

It's 50VDC, but it's completely internal to the unit so it really doesn't matter.
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