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paulz
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# Posted: 24 Aug 2019 03:47pm
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Just back from the cabin. This time of year we spend more days than usual before returning to our flop house in the city. 3 days and nights this time, about 72 hours.
I run the cabin off 3 group 27 lead acid batteries in parallel in my truck and charge them at the house before leaving, they also charge when driving. They are old,4-5 years but seem to hold a 12.5 volt charge fine when idle. Also have a small solar that keeps an additional battery in the cabin charged that I plug in if we take the truck out to dinner or errands.
Everything in the cabin is 12v. I put an ammeter at the truck yesterday. Running the basic cabin stuff that's on all the time used about 1 amp. If I turn on some LEDs, a fan, tablet or what not it goes to 2-3. The 12v TV and water pump use some juice but they don't go on much if at all, gravity feed water supply works fine most of the time.
So, after 72 hrs or so my truck batteries were showing 11.7 while the cabin was plugged in, after unplugging they went up to 12.1 or .2. Too much drain? I've been trying this online calculator which says for what I just did I need about 200ah. Is that to get down to 12.2? I'm asking because there are some good deals on LA deep cycle batteries at the moment around here, guys converting to lithium, which I'm guessing would cost me about a grand to do what I do now.
https://www.batterystuff.com/kb/tools/calculator-sizing-a-battery-to-a-load.html
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FishHog
Member
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# Posted: 25 Aug 2019 06:40am
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Your batteries are too old. Fully charged you should see 12.7 or 12.8 minimum. 12.2 is about 50% charge which is as low as you should take a lead acid battery if you want it to last
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creeky
Member
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# Posted: 25 Aug 2019 11:03am
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For a grand I would convert to lithium too.
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paulz
Member
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# Posted: 25 Aug 2019 05:56pm
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OK I'm convinced, after a bit more reading. Which mentioned that 100 ah for lithium is actually more than LA because of further discharge capability, also faster charging, etc. etc.. Just missed a smoking deal on a 160ah battery for $500 with accessories. I can likely limp along on the batteries I have until something else comes along. Too bad they're not like flat screen TVs, a grand one year and two hundred bucks the next.
I live close enough to Tesla, maybe i should take a drive over there..
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Brettny
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# Posted: 25 Aug 2019 08:32pm
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Look up valance u27 batterys on ebay. I believe 130ah for roughly $500-600. In this day in age and how fast lead acid batterys age i would mess with them unless they are the cost of scrap.
I do belive your doing it right though. Charge at home or when the vehicle is normaly driving and bring your power in. Buying power from the power company is almost always cheaper than making it your self.
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Nobadays
Member
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# Posted: 25 Aug 2019 11:06pm
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Brettny.... great tip on the Valance u27 LiPo batteries! I don't need any right now but they look like they would be a great alternative to the Chevy Volt modules I'm using.... 4 Valance batteries to make 48v but at 138ah/EA that 552ah. The Chevy Volt 2kw modules (~$400/ea) are only about 47ah/ea so almost 12 CV modules to equal 4 of the Valance LiPo batteries.
Of course my solar math is always questionable but unless I'm missing something... >$2,500 opposed to $4,800 for the same amp hours.... deal here!
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paulz
Member
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# Posted: 26 Aug 2019 09:39am
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Yep, those looks like the ticket. Thanks Brettny!
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SCSJeff
Member
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# Posted: 26 Aug 2019 10:52am
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Those Valence batteries are used. So I would guess closer to 100AH usable remaining... Still not bad though.
Here's a good video review on them...
URL
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Nobadays
Member
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# Posted: 26 Aug 2019 03:34pm
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SCSJeff...IF... and that's a big IF, these used batteries only have the advertised "300" cycles, they could be considered practically new. The manufacturer estimates 4000 cycles so if you look at degradation curves on LiPo batteries, 300 cycles is barely "off full'up!"
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paulz
Member
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# Posted: 26 Aug 2019 06:31pm
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One of the ebay sellers is in San Francisco, driving distance for me, apparently has a boatload of them, and offers exchanges on any battery that's not up to snuff. Also a 20% discount on multiple purchases. Might see about 2 or 3.
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creeky
Member
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# Posted: 27 Aug 2019 11:34pm - Edited by: creeky
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Nobadays
adding batteries in series to increase volts doesn't also increase amp hours
so take 4 140ah Valence at 12v each for 48v is still 140ah. (12vX4) at 136ah = 136ah
So 4 of the Valence are = to 3 chevy volt modules
48v X 3 at 47ah = 141ah.
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paulz
Member
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# Posted: 28 Aug 2019 10:35am - Edited by: paulz
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Day 3 at the cabin and my lead batteries are dead, runnimg of a generator. So it looks like I'm going to take the plunge asap. Fortunately a couple guys are interested in that mile of pvc pipe I'm selling..
Will it be ok to charge the Valence batteries with my truck? How about at home or off a generator? Standard automotive charger? How many amps? Apparently they have anti screwup protection?
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Brettny
Member
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# Posted: 28 Aug 2019 12:40pm
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There are better forums to ask that specific question on. Lithium is a bit more picky on how it charges but im sure you can google it.
How much are you getting those u27 batterys for? I may be interested in one or two.
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Nobadays
Member
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# Posted: 28 Aug 2019 03:40pm
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Ahhhh.... I knew that Creeky! I said my solar math was suspect! Why I can't keep that stuff straight I don't know!
Thanks for the schooling! Looks like Chevy Volt modules win out.. if you can find them in the $400/2kw/48v modules. The guy I get mine from has 7 from a 2015 Volt for sale on Ebay, free shipping.
The cool thing about the Valance batteries is I believe they have a BMS built into them... at least according to the YouTube link above in this thread.
Cheers! Don
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paulz
Member
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# Posted: 28 Aug 2019 05:00pm - Edited by: paulz
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Brett,
I contacted this seller in San Francisco, because I could drive there and see/test them for myself. Also if needed exchange one that wasn't good. And they apparently have many of them.
They said 10% off on 3, maybe more would get better. I don't mind shipping them. Looked there may be some cheaper ones on Ebay..
https://www.ebay.com/itm/12V-138Ah-Valence-Lithium-Phosphate-Battery-Great-for-RVs/18 3927514612
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Brettny
Member
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# Posted: 29 Aug 2019 08:29am
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Ok thank you.
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paulz
Member
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# Posted: 29 Aug 2019 02:16pm
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This just popped up locally. I emailed him, he says it can be wired for 12v 600ah!
Hmm.
https://sfbay.craigslist.org/sby/for/d/sunnyvale-lifep04-lithium-ev-batteries/6965340 165.html
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creeky
Member
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# Posted: 1 Sep 2019 01:34pm
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He's got them (craigslist) at 5 cells per module. You would do them as 4 per module. So instead of 5 cells and 4 modules visible. You'd have 5 modules of 4.
4x3.2 nominal is 12.8v. Pretty close match for lead.
I only see 20 cells. So he must have another module somewhere.
But as a 4 pack you could do 48v at 100ah. 5.5 kwh of storage.
Great for a small solar system.
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paulz
Member
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# Posted: 1 Sep 2019 05:32pm
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Yeah I missed that, only 20 cells showing. Still mulling it over, I've exchanges a couple emails and done some reading. They are Winston cells, supposedly not the greatest and no idea how many years old but not a lot of cycles. I would need to figure out a bms that would work with my truck alternator as well as a 110ac charger. I'm wondering why no one has snapped them up already? Meanwhile I'm back at the cabin today with my dying LAs...
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paulz
Member
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# Posted: 20 Sep 2019 12:07pm
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Quoting: Brettny How much are you getting those u27 batterys for? I may be interested in one or two.
I just bought a U27 on Ebay. A seller out of LA has them for $350 or offer plus shipping. Ebay had a 10% off coupon and the seller took my $340 offer so it cost me $350 shipped.
My lithium experience commences... I plan to try it in my current setup: powering my 12v cabin (leds, water pump, phone chargers, fans..) in place of my 3 weak lead batteries. Supposedly has built in BMS, hopefully can charge with one of my 110 chargers.
Should arrive next week, I'll report back.
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redwolfguild
Member
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# Posted: 20 Sep 2019 12:21pm - Edited by: redwolfguild
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creeky I love the way you are looking at this. I am hesitant to pick up used batteries, but it seems like the way to go. Do you still put together packages for Rookies like me who just need a good plug and play system?
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