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beachman
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# Posted: 26 Mar 2019 01:31pm
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Have a general question about lithium v. lead acid. Usually the LI batteries post an AH rating at around 100 whereas the LA post much higher - say 250 to 400 AH. Say you have a 12 v system (I know - 24 or 48 is better) and you have a lower AH rating, does this mean less WHs? Would you need more LI battery power to achieve the same watt hours?
Also, what about charge controllers and charging of LI compared to LA? What are the recommendations?
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justinbowser
Member
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# Posted: 26 Mar 2019 02:37pm
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The partial equalizer between Li and Pb is you can safely discharge a Li battery further so your 100 AH goes further. Most high-end charge controllers will handle Li just fine.
My battery bank is 300 AH at 24 VDC. I usually don't like to discharge below 75% SOC which would be using 75 AH of it's capacity. You can discharge (I've read) Li down to 20%-25% SOC so you have about the same usable capacity with a 100 AH Li.
Somebody will correct me if I'm too off-base...
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Brettny
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# Posted: 27 Mar 2019 12:22pm
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Flooded, gel and AGM you can really only use 50* of the batterys WH. The lithium batterys you can use almost 80* i believe.
Prety much every other battery has a 6-10yr life and lithium has a 20-30 year life. Lithium always wins in every catagory becids price.
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redwolfguild
Member
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# Posted: 27 Mar 2019 04:42pm
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Quoting: Brettny Prety much every other battery has a 6-10yr life and lithium has a 20-30 year life. Lithium always wins in every catagory becids price.
But you need to make sure you keep them at a certain temp when charging. They work for 99% of applications.
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beachman
Member
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# Posted: 28 Mar 2019 11:55am
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Thanks for the replies. I am thinking forward to the eventual replacement of my LA batteries. LI seems more practical for me and I don't really plan on any charging in below-freezing temps. I am just concerned about the power generated. Even with an 80% dod, 100 AH doesn't seem enough without the addition of several more batteries. Maybe I am still missing something?
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ICC
Member
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# Posted: 28 Mar 2019 01:34pm - Edited by: ICC
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What exactly are you using for batteries right now? What is the battery bank nominal operating voltage and the pack AH total?
IF you had a 12 volt bank and the AH capacity was 225 and IF you normally only used 25% of that 225 AH THEN you could use a Lithium pack of 100 AH.
BUT you would not have much reserve if the weather was very cloudy and the solar panel output was very low. However, a partial saving grace is that because the internal resistance of Lithium cells is much less than lead-acid cells solar does more work. In other words, the same amount of sunshine on the same panels will actually recharge more capacity into a lithium pack than into a lead-acid pack. Magic!
If you draw the above lead-acid pack down to 50% often then your lithium pack should be bigger, probably at least 150AH.
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beachman
Member
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# Posted: 28 Mar 2019 04:14pm
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ICC, Thanks. Right now I have 2 - 370 AH Trojan L16's 6V each in series for a 12 V system. I have about 510 watts of panels to charge the system -2 panels. The 370 AH at 12 V gives about 4,440 WH at 50% leaves 2,220 WH for 3 days if little sun gives me about 750 WH per day. I probably use less than this as the batteries easily charge back to full most days. My monitor has been out for a year but should be back up this summer.
Just wondering now what the best LI option would be in the future.
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justinbowser
Member
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# Posted: 28 Mar 2019 11:22pm - Edited by: justinbowser
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Here's a couple choices. Being at 12V cuts your options some but there are a couple there. When my battery bang bites the dust I am leaning toward two of the 24V 3.5kWh LFP batteries.
https://www.thepowerstore.com/battery-systems/batteries/lithium/lithium-ion.html
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creeky
Member
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# Posted: 29 Mar 2019 08:11am
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CALB has some pretty good LFP modules now. You can find some decent pricing if you're willing to ship out of China.
I still like the auto LG Chem cells. There's a guy out there with 165,000 electric miles on his chevy volt with 0 degradation. And the price used to be good.
General advice: go 48v. It will save a lot of money and gives you more long term flexibility.
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beachman
Member
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# Posted: 29 Mar 2019 08:36am
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Yah - hoping to retain the 12v stuff but everything points to 24v or 48v nowadays so will likely go that route. Especially considering more panels down the road in a new location. The Simpliphi stuff is very neat - note they ref 1.2KWH on a 24v model at 160AH so gives over 3,840 at maybe an 80% dod for just over 1KWH per day which would suit me fine. Will check out the CALB stuff also. Thanks all!
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offgrididaho
Member
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# Posted: 29 Mar 2019 10:43am
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Quoting: ICC However, a partial saving grace is that because the internal resistance of Lithium cells is much less than lead-acid cells solar does more work. In other words, the same amount of sunshine on the same panels will actually recharge more capacity into a lithium pack than into a lead-acid pack.
Wholesale Solar has good battery sizing calculator that can help compare FLA with lithium:
https://www.wholesalesolar.com/solar-information/battery-bank-sizing
But short answer is ICC is right, when sizing FLA bank you use an inefficiency factor of 1.2 (i.e. make your bank 1.2 bigger than you thought to cover for charging inefficiencies) whereas inefficiency factor for lithium is 1.05.
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Jebediah
Member
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# Posted: 29 Mar 2019 05:34pm
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Check out this Utube channel...Will Prowse, he is a young guy but knows just about everything there is to know about Lithium...He does a lot of comparisons(tests) with real time results.....
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