OFF GRID POWER; various thoughts on...

Started by MountainDon, January 13, 2009, 02:18:39 AM

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MountainDon

Quote from: Dave Sparks on February 21, 2023, 01:49:56 PMDon,  what ever happened to Glen the moderator? Hope you and Karen are Peachy!

I haven't seen Glenn here for quite a while. I do see he did log in about a week ago. He is still around; he has a presence on facebook.

Karen and I are fine. We are waiting for it to stop snowing and begin melting in the mountains. We have had more snow up there than any year in the past 5 or so for certain. The snow is welcome, we just don't bother trying to access the cabin and may not until sometime in April. Then we have several bags of assorted seeds to sow. A mixture of annual and perennial grasses were donated by state and national reclamation agencies.
Just because something has been done and has not failed, doesn't mean it is good design.

OlJarhead

At first I thought Big Battery was just the store but it appears they are a US company and make the batteries in the US.
https://bigbattery.com/business-to-business/

Amazon has a Chinese 24v100AH LiPo4 battery for under $700...so I suppose I could get 3 of those for $2100 but the 10 year warranty and US support for the Big Batteries seems like it might be safer ;)

I'm almost 100% committed :D  I need to make plans to finish the super insulated room and move at least the Inverter to there as well but the Charge Controllers may remain where they are...I'm just not sure!!!  I could move them I guess and it would only add about 18 feet to the runs from the combiner boxes so I'm thinking that would be ok because I'm running over 60vdc at that point anyway.

And if I put the combiners and inverter in with the batteries in the back room (and secure it with a well secured steel door) it would be VERY HARD for a crack head to break in and take it all vs what I have today.

So, I'm 'this close' to going with LiPo!  Have the $$$ on hand too.

What am I missing?  What should I consider?  Any other battery suggestions?


MountainDon

Quote from: OlJarhead on February 24, 2023, 08:11:35 AMBig Battery ... ...it appears they are a US company and make the batteries in the US.

Well, that is something. So all we need to do is hope they remain in business for at least as long as the warranty period. It is tempting to go for the lower-priced unit from Amazon but then we get into more questions about who is behind them, and what's inside the box. It is sometimes hard to really know what the best choice is. The $700 "looks" like a deal.

Quote from: OlJarhead on February 24, 2023, 08:11:35 AM...if I put the combiners and inverter in with the batteries in the back room (and secure it with a well secured steel door) it would be VERY HARD for a crack head to break in and take it all vs what I have today.

Not to rain too hard on your parade, but when I built our cabin I thought the same about the steel door, 1" deadbolt, etc. Now I think that works best in town where there are neighbors close by and the noise of breaking in might also be a deterrent. The 2 brothers who broke into our cabin were drug users. There were no neighbors around. They had to work very hard to breach the door, but they did. Cabin, shed and barn. I ended up needing to replace the steel door and the frame on the cabin and make "make-do" repairs on the barn and shed doors. The new door has no fancy locks, just enough to keep out an honest person. I did have the satisfaction of seeing the two big bootprints on the door that likely happened before they resorted to the 6-foot steel digging bar and deforming the door and splitting the frame all to hell.

It sucks when we have to be so concerned about thefts. Back in my youth, I don't think the doors on the farmhouse were ever locked. The keys were always in the truck.

Just because something has been done and has not failed, doesn't mean it is good design.

OlJarhead

Good point.  Perhaps just the one I made, with insulation as planned and insurance ;)  If I can get it. 

jsahara24

There is a guy on youtube that tears apart a lot of the foreign made batteries, I can't recall his name but his videos are very informational.  Some batteries are definitely better than others but its probably worth checking out if your considering it.  Unfortunately I don't have any experience to offer.  


OlJarhead

Thanks.

I'm now very seriously looking at ordering the LiPo4 batteries and storing until I am ready for them as I'll need to do some work first.

With inflation and the fact they can come with a charger etc I'm thinking I could charge them up and store them fir the few months until the room is ready.

Then I'll sell the GCBs for cheap as they do have some life in them still.

MountainDon

I see Amazon has several different brand names of what appear to be the same 24V 100AH LiFePO4 batteries. None that I looked over made any mention of a low-temperature cutoff being included. High temp yes. That is sort of too bad, though I believe Victron has a low-temperature cutoff device available. Not sure how much it costs.

BigBattery mentions Over/Under Temperature Protections, but I didn't see any specs on that. But I didn't look too hard either.

I'm interested in what you do.
Just because something has been done and has not failed, doesn't mean it is good design.

OlJarhead

24V Battery Lithium 120Ah 3 kWh LiFePO4 LFP Residential Solar Trailer Cabin Boat (batteryevo.com)
I'm also looking at these now ;)

They are pretty much the same as the Big Battery ones I think.  Seems like the price comes from recycling cells that weren't used previously or not used enough to reduce life cycles.

The cells are from China, the batteries assembled and tested here.

One way or another, I've committed to doing this NOW (like to get in before they go up in price like everything else does lol).

Just trying to get the best one I can with support etc.
I plan to get with the charger and parallel bus so I can charge them and leave them in the shop before use :D  I think that will motivate me :D ;D

OlJarhead

On the amazon ones I kept seeing reviews that made me pause ;)  You have to hunt for them as they show the top ones up front but when it came to support it seemed like you had to talk to China....and getting a refund might not happen if something goes wrong.

Also, the US stores seem to all offer affiliate programs which could be nice.


jsahara24

I found the guy I was watching on youtube.  If you are interested in a specific battery he may have torn one down.  I don't know anything about him but I do enjoy his videos.  

DIY Solar Power with Will Prowse


OlJarhead

I've made a decision (unless I find a better deal while I wait for them to come in stock)....

I'm going with the BigBattery ones.  They are NEW cells, 10 year warranty and 3000-5000 life cycles at 100%DoD according to them vs recycled batteries, 3 year warranty and 4000 life cycles at the other place.  Pricing is almost the same.

So I'll order the 360AH bank which will give me 288AH of useable backup (80% DoD) without much worry which is more than 3 days of backup before I hit 80%.  Vs the 2 days I had to get to 20% DoD on my FLA GCB's.

Basically now I can go 4 days without solar vs 2 days before.

Only thing I need to sort is when to make the genny come on which I'm guessing might be around 50%DoD instead of 20% like do now (actually probably more like 10%)...I'll have to see a voltage curve but I suspect I'll run the generator a lot less now.

OlJarhead

Need LiPo4 Batteries?!  Check this out:  24V Battery Lithium 120Ah 3 kWh LiFePO4 LFP Residential Solar Trailer Cabin Boat (batteryevo.com)

At checkout put in the Coupon Code of OldJarhead and you'll get 10% off!

I haven't announced this ANYWHERE else yet but do plan to do a video soon with the announcement to let everyone know.

I also see the price of these is down a little to $995ea so you'll get $99.50 off EACH battery if you buy these but the code is good for ANYTHING on the site.

Hope that helps someone :D

OlJarhead

One thing I need to find is a voltage guide to SOC levels for LiPo....anyone have a good source?

MountainDon

Quote from: OlJarhead on March 15, 2023, 04:42:09 PMOne thing I need to find is a voltage guide to SOC levels for LiPo....anyone have a good source?

Rather than referring to these as LiPo I believe you should be using the term  LiFePO4, as LiPo can refer to a type that has a nominal voltage of 3.7 volts and is not the same chemistry as LiFePO4.

I understand SOC to mean "state of charge", correct?  Voltage is not a very good guide to SOC for any lithium-based rechargeable cells and batteries unless a very accurate voltage meter is used. They do not drop voltage as much as lead acid. Being off by 0.1 volt makes a bigger difference than with lead-acid cells and batteries.

I've seen a few tables but I can't say one is better than any other. I don't know where the data is coming from as they mostly all seem to have the same anomalies that I figure are coming from rounding off voltages to a tenth of a volt.
Just because something has been done and has not failed, doesn't mean it is good design.


OlJarhead

Interesting!  I always learn here :D

The controllers on the batteries only show DC Volts and Amps so it's hard to know where they are.  Currently they show 26.7v and I have a charger which is set to charge at 28v I believe (need to double check that).

I know the shut off is set between 20-21v so I can assume that's 100%DoD but was hoping they would have some kind of ramp that would give me an idea of where they are now.

I was told not to store them more than 3 months without charging them but I also read somewhere not to store them at 100% SoC.

???

MountainDon

Quote from: OlJarhead on March 15, 2023, 06:24:43 PMI also read somewhere not to store them at 100% SoC.

???

I believe the voltage for a planned storage period with LiFePO4 should be 3.3 to 3.4 volts per cell.
Just because something has been done and has not failed, doesn't mean it is good design.

OlJarhead

I'll have to see how many cells there are and get the charge voltage right.  I have the PDF somewhere at home ;)  Time to get them up to speed on charge I think.

OlJarhead

I've learned that I just need the three batteries to be within 1v of each other which they are now after some charging.  it's clear though, that the BOM's decide when they are full or not and shut off any incoming charge to stop them from overcharging.

Also, for now, I've decided to install them where the old FLA's are for now to get them in use sooner.  Then I can spend the time needed to get the back room ready.

MountainDon

#1568
BOM's    BMS  :D

I believe that voltage should be more in the neighborhood of 0.1 volt between 12 volt batteries connected in parallel, not 1.0 volt. However, I have read other opinions that 0.2 volts to 0.3 volts difference is okay too.

A small voltage difference between lithium cells and batteries is a greater difference in total charge or energy, than what we are used to with lead-acid.
Just because something has been done and has not failed, doesn't mean it is good design.

OlJarhead

What they are saying is that it must be within 1v before connecting.  Not sure why it doesn't need to be closer...maybe something to do with getting them balanced after connecting?  

Or maybe he said 1V but meant .1V...hmmm


MountainDon

I guess we can't go too wrong by following what the seller states.
Just because something has been done and has not failed, doesn't mean it is good design.

OlJarhead

QuoteI just need to confirm that my voltage between 3 Mules I will be running in parallel should be within 1v of each other?

Is that correct? Bascially one is at 27.5v one is 28v and one is 27.7v

Dylan 11:06 AM
Yes that is correct
I'd decided to double check with tech support on my 3 LiFePo4 batteries. and the above is what I got back.

Also, they have a button to turn them 'on' or 'off' in the front so all three will need to be 'on' whenever in use which for me will be all the time.

MountainDon

Just because something has been done and has not failed, doesn't mean it is good design.

OlJarhead

OH man I LOVE my new batteries!  I'll report more on them later but just know that I now see the light!!!

Woot!

MountainDon

Just because something has been done and has not failed, doesn't mean it is good design.