I need to upgrade my system to Lithium. What battery should I buy? I just had 6 lead acid sealed Marine batteries die after one year of use/never performed correctly (which is another topic). I believe investing in a Big Battery LIFEPO4 battery will give me peace of mind (10 years of warranty). Also it makes sense money-wise: 8 Marine batteries @$120 each for two years (in theory) vs one Big Battery 5.8KWH @ $2300 for ten years. The cost of the Big Battery is about $230 per year over 10 years. I live in PR where our electric system was just privatized to a ill-prepared LUMA Energy. In the two weeks since they took over we have had several outages. I have a hybrid system where my inverter can charge the batteries from the grid BUT ... with no reliable grid. My array is four 315w polycrystalline panels. I have an AIMS MPPT 100 amp controlar and an AIMS 2000w Inverter. I live alone and my usage is about 3.5 KWH per day or less (I tested and my refrigerator uses exactly 1K per day). I use lights, fans, TV and computer. The Big Battery website says that the 5.8KWH battery is out of stock. I hope not for long. My other option is the 24V HAWK MAX - LIFEPO4 5.2KWH (instead of the 5.8kwh MAX 2). I am told that I should have 3 times my daily usage in the battery power to account for cloudy days. Math: 3 x 3.5kwh = 10.5 KWH. But I live in sunny PR, so how about 2 X 3.5 KWH per day= 7.0 kwh. What size battery do I need? Thanks in advance for any help. Kathy
Which Big Battery to buy? leaning toward 24V HAWK MAX 2 - LIFEPO4 - 228AH - 5.8KWH
- Thread starter kathyg
- Start date
Update: Big Battery informe me that the 24V HAWK MAX 2 - LIFEPO4 - 228AH - 5.8KWH is discontinued. Big Battery says, "we can't get the cells in to make the battery". So now I will be hoping to but the 24V HAWK MAX - LIFEPO4 5.2KWH. Looking for help deciding if this will be a good choice based on my use of 3.0 to 3.5kwh per day.
svetz
Works in theory! Practice? That's something else
Welcome to the forums!
I can't help answer the question of which battery is the best deal, but @ghostwriter66 is always on the prowl for good quality and low price so you might check her posts out. She's more about buying cells rather than drop-ins, but that might lead you to what you're looking for or perhaps get you started on making your own (Will has a number of videos on that, and in the solar blueprints above you'll find what he thinks are the best quality parts for the lowest price).
It sounds like there are a few other things going on that perhaps some members can help with?
I'm not saying stay with lead, but it would help to understand why they died so history doesn't repeat itself.
Most common causes for low number of cycles are draining them 100% each night or leaving them discharged for long periods.
If you can tell us more about this, possibly a member can identify what went wrong.
You can validate that by looking at your monthly electrical bill and seeing the number of kWh used in the month and dividing by the number of days. For example, if the price of electricity there is 13.29¢/kWh then your monthly bill would be about 3.35 kWh/d x 31 days x 0.1329 $/kWh ~= $13.80 plus the surcharges. There are also some example calculations in How to figure out how much Solar and inverter wattage is needed to charge a battery that might help with the basics in regards to sizing solar panels and MPPT, but it sounds like you're set there. Ask if you have questions though!
Hope that helps!
I can't help answer the question of which battery is the best deal, but @ghostwriter66 is always on the prowl for good quality and low price so you might check her posts out. She's more about buying cells rather than drop-ins, but that might lead you to what you're looking for or perhaps get you started on making your own (Will has a number of videos on that, and in the solar blueprints above you'll find what he thinks are the best quality parts for the lowest price).
It sounds like there are a few other things going on that perhaps some members can help with?
That shouldn't happen.
I'm not saying stay with lead, but it would help to understand why they died so history doesn't repeat itself.
Most common causes for low number of cycles are draining them 100% each night or leaving them discharged for long periods.
If you can tell us more about this, possibly a member can identify what went wrong.
Nice analysis! 8x $120 x 10 years / 2 year replacement cycle = $4800 < $2300
Sounds like you have a good handle on it, the Energy Audit (see signature below for more helpful links) can put it in a nice table for future use for you.
The amount of reserve is purely a personal one, for a lot of folks it's what they can afford and they add a little more to it over time. But, there are concerns to know about when doing that, see Incrementally Adding DC Batteries for more.
You math is correct and 3.35 kWh per day is impressively low.
You can validate that by looking at your monthly electrical bill and seeing the number of kWh used in the month and dividing by the number of days. For example, if the price of electricity there is 13.29¢/kWh then your monthly bill would be about 3.35 kWh/d x 31 days x 0.1329 $/kWh ~= $13.80 plus the surcharges. There are also some example calculations in How to figure out how much Solar and inverter wattage is needed to charge a battery that might help with the basics in regards to sizing solar panels and MPPT, but it sounds like you're set there. Ask if you have questions though!
Hope that helps!
Last edited:
ghostwriter66
"Here - Hold my Beer"
Welcome to the forums!
I can't help answer the question of which battery is the best deal, but @ghostwriter66 is always on the prowl for good quality and low price so you might check her posts out. She's more about buying cells rather than drop-ins, but that might lead you to what you're looking for or perhaps get you started on making your own (Will has a number of videos on that, and in the solar blueprints above you'll find what he thinks are the best quality parts for the lowest price).
It sounds like there are a few other things going on that perhaps some members can help with?
That shouldn't happen.
I'm not saying stay with lead, but it would help to understand why they died so history doesn't repeat itself.
Most common causes for low number of cycles are draining them 100% each night or leaving them discharged for long periods.
If you can tell us more about this, possibly a member can identify what went wrong.
Nice analysis! 8x $120 x 10 years / 2 year replacement cycle = $4800 < $2300
Sounds like you have a good handle on it, the Energy Audit (see signature below for more helpful links) can put it in a nice table for future use for you.
The amount of reserve is purely a personal one, for a lot of folks it's what they can afford and they add a little more to it over time. But, there are concerns to know about when doing that, see Incrementally Adding DC Batteries for more.
You math is correct and 3.35 kWh per day is impressively low.
You can validate that by looking at your monthly electrical bill and seeing the number of kWh used in the month and dividing by the number of days. For example, if the price of electricity there is 13.29¢/kWh then your monthly bill would be about 3.35 kWh/d x 31 days x 0.1329 $/kWh ~= $13.80 plus the surcharges. There are also some example calculations in How to figure out how much Solar and inverter wattage is needed to charge a battery that might help with the basics in regards to sizing solar panels and MPPT, but it sounds like you're set there. Ask if you have questions though!
Hope that helps!
If you killed 6 Marine Lead Acid in 2 years then I would figure what that ISSUE is before switching to LiFePO4 and perhaps - as @svetz says - repeat history.... I love LiFePO4 BUT we have AGM batteries out here and Lead Acid that have been cranking stuff for over 10 years ... if you take care of an AGM our WET and keep them topped off and the right specific gravity and don't drop them below abut 50% they will last forever - well almost ... TWO years and dead is a major concern ..
Welcome to the forums!
I can't help answer the question of which battery is the best deal, but @ghostwriter66 is always on the prowl for good quality and low price so you might check her posts out. She's more about buying cells rather than drop-ins, but that might lead you to what you're looking for or perhaps get you started on making your own (Will has a number of videos on that, and in the solar blueprints above you'll find what he thinks are the best quality parts for the lowest price).
It sounds like there are a few other things going on that perhaps some members can help with?
That shouldn't happen.
I'm not saying stay with lead, but it would help to understand why they died so history doesn't repeat itself.
Most common causes for low number of cycles are draining them 100% each night or leaving them discharged for long periods.
If you can tell us more about this, possibly a member can identify what went wrong.
Nice analysis! 8x $120 x 10 years / 2 year replacement cycle = $4800 < $2300
Sounds like you have a good handle on it, the Energy Audit (see signature below for more helpful links) can put it in a nice table for future use for you.
The amount of reserve is purely a personal one, for a lot of folks it's what they can afford and they add a little more to it over time. But, there are concerns to know about when doing that, see Incrementally Adding DC Batteries for more.
You math is correct and 3.35 kWh per day is impressively low.
You can validate that by looking at your monthly electrical bill and seeing the number of kWh used in the month and dividing by the number of days. For example, if the price of electricity there is 13.29¢/kWh then your monthly bill would be about 3.35 kWh/d x 31 days x 0.1329 $/kWh ~= $13.80 plus the surcharges. There are also some example calculations in How to figure out how much Solar and inverter wattage is needed to charge a battery that might help with the basics in regards to sizing solar panels and MPPT, but it sounds like you're set there. Ask if you have questions though!
Hope that helps!
Thank you both for raising the issue of my six dead marine batteries. They died in one year or maybe less. After the system was installed by my solar installer a few weeks later I noticed they often switched to the grid to recharge but it only took about two hours. Since I didn't know what should be happening, I didn't write to the installer until about six months later when it seem to be going to the grid more often. The batteries seemed to go to the grid only early in the morning or during the night, not during the day. If my memory is correct, the controller usually read over 25.2 volts when the sun went down. I averaged about 3.5 kwh of energy put into the batteries (reading from the controller). During the night I run one fan and one refrigerator (1kwh per day) - not very much. Although I made the request, for various reasons, the installer did not come to check the system for the first time until 12 months after the installation. After a considerable amount of time and two visits, he saw that there was liquid acid on top of one battery, powder on connections and melted electrical tape, and said that the batteries "boiled over with just 25 amps charge" and is certain that the batteries were bad when I got them from the store. I am about to return them to the store (they are giving me a credit for 3 batteries, even though the one year warranty has expired) . During this one year, I think I was using solar power most of the daytime. I have one meter and three apartments in my house. he solar is connected only to my apartment. In the attached spreadsheet, you can see I had to have been living on solar during the summer months. I had a guest in one apt using AC for 7 nights at the end of October and the use increases from 1 kwh or less per days to 7 kwh. During COVID, those tourist apts were empty and my bill did show a sharp decrease from the end of May when he system was installed until Oct/Nov when I began to have tourists again. You can also see that the April and May bill - after COVID started and before the system was installed were 2.4 kwh and 2.97 kwh - basically how much I use living alone. See attached file on electric bills. PS: Installer has good "credentials", he is "Master Electrician/Technician (25+ yrs) and Automotive Master Electrician, ASE (30+ yrs)". I think I am reasonably knowledgeable on the components of home solar - but I cannot analyze what happened to the batteries. Thanks very much. (I apoligize if this is too much info.)
Attachments
The system was installed on May 27, 2020.
ghostwriter66
"Here - Hold my Beer"
I have an Electrical Engineer degree from a TOP 3 University -- I specialized in Power Management - I work on and am certified on some of the largest generators and transmission lines in the world - and when they told me that I was going to work on SOLAR I never realized how little I knew .... as my boss likes to say Solar is exactly the same as Shore Power - but totally different ../// AC is very straightforward -- solar on the other hand has allot of voodoo magic and things work or don't work for no rhyme or reason. I say all of that just to say that I have learned more about solar here in this forum from regular ppl then all those "experts" that certified me ....
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