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Brent S

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Awesome products but they are still darned expensive! I’m really hoping within the next couple years the prices will begin to drop. I just installed two AGM 100amp 12v batteries that Doc told me about on my camper. Would have loved to use the lighter and longer lasting lithium ones but just not worth it to me just yet. Wish I was rich!
 

TexasFreedom

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Li ion batteries actually aren't more expensive than lead/acid or AGM. Consider...

Let's say you have a deep cycle lead acid battery for $150. It might be 12 volt, 150 amp-hour. And a reasonable life would be 100 cycles at 50% discharge. One way to look at it is what is the total charge/discharge capacity? 100 cycles x 50% x 150 amp-hour = 7500 cycle-amp-hours. And price per unit, it's $150/7500 = 2 cents/c-a-hr

Now compare this to a lithium ion battery. I can buy 12v Li-Ion 20 amp-hour batteries for $60 all day long. You can deep cycle it 80% for 500 cycles. So capacity: 500 cycles x 80% x 20 amp-hour = 8000 cycle-amp-hours. And price per unit, it's $60/8000 = 0.75 cents / c-a-hr.

So in this comparison, the lithium-ion battery is only 40% the cost over the life of the battery.

The more expensive factor with Li-ion batteries is immediate capacity. If you get that 12v 100a-hr AGM lead-acid battery, you're probably spending $100-150. And it has a usable 50 amp-hour capacity (50% drainage). That smaller Li-Ion battery is 12v 20amp-hour rated, of which 16 a-hr can be cycled. I'll need about 3 of these to get to the 50 amp-hour rating of the AGM, which means $180.

Another factor is weight. The example above, the AGM battery is probably 50+ pounds. The Li-ion batteries are 4 lbs each, so 3 of them are 12 pounds. It's also maybe 1/2 the volume.
 

DrHenley

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If you get that 12v 100a-hr AGM lead-acid battery, you're probably spending $100-150. And it has a usable 50 amp-hour capacity (50% drainage).
A couple of corrections Texas:

AGM batteries have a depth of discharge of 80%. It is flooded cell batteries that have a depth of discharge of 50%

Capacity is usable capacity, not total capacity. Deep cycle batteries have a 20 hour rating. A 100 Amp Hour deep cycle battery will deliver 5 amps for 20 hours. After that point it can no longer deliver a 5 amp current. Starting batteries have a 10 hour rating. So a 100 amp starting battery can deliver 10 amps for 10 hours.

Any higher current and you get fewer amp hours. Any lower current and you get more amp hours.
 
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Brent S

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Li ion batteries actually aren't more expensive than lead/acid or AGM. Consider...

Let's say you have a deep cycle lead acid battery for $150. It might be 12 volt, 150 amp-hour. And a reasonable life would be 100 cycles at 50% discharge. One way to look at it is what is the total charge/discharge capacity? 100 cycles x 50% x 150 amp-hour = 7500 cycle-amp-hours. And price per unit, it's $150/7500 = 2 cents/c-a-hr

Now compare this to a lithium ion battery. I can buy 12v Li-Ion 20 amp-hour batteries for $60 all day long. You can deep cycle it 80% for 500 cycles. So capacity: 500 cycles x 80% x 20 amp-hour = 8000 cycle-amp-hours. And price per unit, it's $60/8000 = 0.75 cents / c-a-hr.

So in this comparison, the lithium-ion battery is only 40% the cost over the life of the battery.

The more expensive factor with Li-ion batteries is immediate capacity. If you get that 12v 100a-hr AGM lead-acid battery, you're probably spending $100-150. And it has a usable 50 amp-hour capacity (50% drainage). That smaller Li-Ion battery is 12v 20amp-hour rated, of which 16 a-hr can be cycled. I'll need about 3 of these to get to the 50 amp-hour rating of the AGM, which means $180.

Another factor is weight. The example above, the AGM battery is probably 50+ pounds. The Li-ion batteries are 4 lbs each, so 3 of them are 12 pounds. It's also maybe 1/2 the volume.
There is no doubt when you look at the longer life of the lithium it becomes closer pricewise, but to get a 200AH lithium battery is an initial outlay of a lot more than a comparably AGM battery. I just checked Amazon and the range for 200AH lithium was 1550 to 3100 dollars, so Let’s say 2300. average. I got the 200AH AGM batteries for about three hundred twenty out the door. Even with the longer life and better discharge depth (as in more usable power without damaging the batteries), it’s hard to justify that initial expense. Don’t get me wrong here, when you factor in all this and the weight reduction, I think lithium is a much better battery. Just not in my budget to experiment on my campers solar system. There are other factors too. There is usually a substantial shipping charge for batteries, along with core charges and taxes. The quoted price is not the final cost.
 

TexasFreedom

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A couple of corrections Texas:

AGM batteries have a depth of discharge of 80%. It is flooded cell batteries that have a depth of discharge of 50%

Capacity is usable capacity, not total capacity. Deep cycle batteries have a 20 hour rating. A 100 Amp Hour deep cycle battery will deliver 5 amps for 20 hours. After that point it can no longer deliver a 5 amp current. Starting batteries have a 10 hour rating. So a 100 amp starting battery can deliver 10 amps for 10 hours.

Any higher current and you get fewer amp hours. Any lower current and you get more amp hours.
Doc, I didn't know AGM were 80% discharge rated. I knew they were more reliable than flooded. This brings the value closer to 1:1 with li-ion.

On the capacity, do you have a link for that, related to usable vs total capacity? In your example, 20 hour / 5 amp = 100 amp-hour rating, I consider that a full discharge, 100%. So to discharge that to 80% would mean getting 80 amp-hours out of it. Just looking for clarity & make sure we're using the same reference.

There is no doubt when you look at the longer life of the lithium it becomes closer pricewise, but to get a 200AH lithium battery is an initial outlay of a lot more than a comparably AGM battery. I just checked Amazon and the range for 200AH lithium was 1550 to 3100 dollars, so Let’s say 2300. average. I got the 200AH AGM batteries for about three hundred twenty out the door. Even with the longer life and better discharge depth (as in more usable power without damaging the batteries), it’s hard to justify that initial expense. Don’t get me wrong here, when you factor in all this and the weight reduction, I think lithium is a much better battery. Just not in my budget to experiment on my campers solar system. There are other factors too. There is usually a substantial shipping charge for batteries, along with core charges and taxes. The quoted price is not the final cost.
Brent, I wouldn't get a single lithium-ion battery that large. I'd rather have smaller batteries, so when one cell fails it's less work to swap it out (and less damage). Price helps too. If you just compare 200 a-hr AGM vs 200 a-hr li-ion, you spent $320 for AGM. With li-ion, I'd get 10 of the 20 a-hr batteries at $60 each. $600. Yes, almost twice the price. But you can expect 3 to 5 times the useful life vs AGM. And for weight, your AGM batteries are probably 100 to 200 lbs? The li-ion would be 40 lbs, so 1/5th the weight. I get it, spending twice as much up front can hurt.
 

DrHenley

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The most common measure of battery capacity is Ah, defined as the number of hours for which a battery can provide a current equal to the discharge rate at the nominal voltage of the battery.
http://pvcdrom.pveducation.org/BATTERY/capacity.htm

I think the most promising technology is LiFePO4. They have made big improvements in the technology, and the price is coming down. They are safer than both Li-Ion and Lead-Acid batteries. They are more difficult to ignite than Li-Ion, and so will tolerate more abuse.

There are already practical LiFePO4 motorcycle starting batteries and small LiFePO4 automotive batteries. But at several times the cost of comparable AGMs...

https://www.walmart.com/ip/LiFePO4-...amaha250-YFB250-F-Timber-Wolf-92-00/134987756

https://www.walmart.com/ip/LITHIUM-...hium-Ion-Power-Pack-12v-800-Max-Amp/365240916

There are still some problems with making large LiFePO4 batteries, having to do with heat dissipation I believe.
 
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DrHenley

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From the Battery University web site: https://batteryuniversity.com/learn/article/absorbent_glass_mat_agm

Learn what differentiate AGM from other lead acid battery types

AGM technology became popular in the early 1980s as a sealed lead acid battery for military aircraft, vehicles and UPS to reduce weight and improve reliability. The sulfuric acid is absorbed by a very fine fiberglass mat, making the battery spill-proof. This enables shipment without hazardous material restrictions. The plates can be made flat to resemble a standard flooded lead acid pack in a rectangular case; they can also be wound into a cylindrical cell.

AGM has very low internal resistance, is capable to deliver high currents on demand and offers a relatively long service life, even when deep cycled. AGM is maintenance free, provides good electrical reliability and is lighter than the flooded lead acid type. While regular lead acid batteries need a topping charge every six months to prevent the buildup of sulfation, AGM batteries are less prone to sulfation and can sit in storage for longer before a charge becomes necessary. The battery stands up well to low temperatures and has a low self-discharge.

The leading advantages of AGM are a charge that is up to five times faster than the flooded version, and the ability to deep cycle. AGM offers a depth-of-discharge of 80 percent; the flooded, on the other hand, is specified at 50 percent DoD to attain the same cycle life. The negatives are slightly lower specific energy and higher manufacturing costs than the flooded, but cheaper than the gel battery.

Most AGM batteries are mid-sized and range from 30 to 100Ah. They can also be found in UPS, big and small for stationary and deep cycle use. They are commonly built to size and are found in high-end vehicles to run power-hungry accessories such as heated seats, steering wheels, mirrors and windshields. NASCAR and other auto racing leagues choose AGM products because they are vibration resistant.

AGM is the preferred battery for upscale motorcycles. Being sealed, AGM reduces acid spilling in an accident, lowers the weight for the same performance and allows installation at odd angles. Because of good performance at cold temperatures, AGM batteries are also used for marine, motor home and robotic applications.

AGM is making inroads into the start-stop function of cars. The classic flooded type is simply not robust enough and repeated cycling causes a sharp capacity fade after only two years of use. (See BU-806a: Heat, Loading and Battery Life.)

As with all gelled and sealed units, AGM batteries are sensitive to overcharging. A charge to 2.40V/cell (and higher) is fine; however, the float charge should be reduced to between 2.25 and 2.30V/cell (summer temperatures may require lower voltages). Automotive charging systems for flooded lead acid often have a fixed float voltage setting of 14.40V (2.40V/cell); a direct replacement with a sealed unit could overcharge the battery on a long drive. (See BU-403: Charging Lead Acid.)

AGM and other sealed batteries do not like heat and should be installed away from the engine compartment. Manufacturers recommend halting charge if the battery core reaches 49°C (120°F).
 

DrHenley

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https://batteryuniversity.com/learn/article/types_of_lithium_ion
Lithium Iron Phosphate(LiFePO4)
In 1996, the University of Texas (and other contributors) discovered phosphate as cathode material for rechargeable lithium batteries. Li-phosphate offers good electrochemical performance with low resistance. This is made possible with nano-scale phosphate cathode material. The key benefits are high current rating and long cycle life, besides good thermal stability, enhanced safety and tolerance if abused.

Li-phosphate is more tolerant to full charge conditions and is less stressed than other lithium-ion systems if kept at high voltage for a prolonged time. (See BU-808: How to Prolong Lithium-based Batteries). As a trade-off, its lower nominal voltage of 3.2V/cell reduces the specific energy below that of cobalt-blended lithium-ion. With most batteries, cold temperature reduces performance and elevated storage temperature shortens the service life, and Li-phosphate is no exception. Li-phosphate has a higher self-discharge than other Li-ion batteries, which can cause balancing issues with aging. This can be mitigated by buying high quality cells and/or using sophisticated control electronics, both of which increase the cost of the pack. Cleanliness in manufacturing is of importance for longevity. There is no tolerance for moisture, lest the battery will only deliver 50 cycles. Figure 9 summarizes the attributes of Li-phosphate.

Li-phosphate is often used to replace the lead acid starter battery. Four cells in series produce 12.80V, a similar voltage to six 2V lead acid cells in series. Vehicles charge lead acid to 14.40V (2.40V/cell) and maintain a topping charge. Topping charge is applied to maintain full charge level and prevent sulfation on lead acid batteries.

With four Li-phosphate cells in series, each cell tops at 3.60V, which is the correct full-charge voltage. At this point, the charge should be disconnected but the topping charge continues while driving. Li-phosphate is tolerant to some overcharge; however, keeping the voltage at 14.40V for a prolonged time, as most vehicles do on a long road trip, could stress Li-phosphate. Time will tell how durable Li-Phosphate will be as a lead acid replacement with a regular vehicle charging system. Cold temperature also reduces performance of Li-ion and this could affect the cranking ability in extreme cases.
 

Brent S

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I’m eager to test out my 200AH AGM batteries and the 100w solar panel charger system. I’ve learned that reading statistics and charts don’t necessarily equate to real world use. I’m hoping to test it out within the next 30days or so, and will post how much actual use I get out of the system. One thing I just did was ordered a pack of 30 12v lamps for the camper. I’m getting rid of all the incandescent lamps in it to improve efficiency as much as I can. I got the whole 30pack for 13.00. Another thing I learned is inverters use power even when not being used, so another disconnect switch will be installed between it and the batteries, and will only have it energized when needed.
 

TexasFreedom

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A couple of notes.

Doc, first, I think we're not seeing eye-to-eye on how batteries are rated. Let's say you have a 12v 150 amp-hour battery (doesn't matter if flooded/AGM/Li-ion). That 150a-hr is the full capacity, no reserve. So if it's 80%, then you have 120 a-hrs. If it's 50%, you have 75 a-hrs of usable power. Nobody rates a battery at the downgraded rating but rather at the full "dead battery" rating.

Brent, I hope you put a monster switch in there. Whatever the watt rating of the inverter, divide that by 12 (assuming 12v system) and that's how many amps the switch should be rated at. So if you have a 2000 watt inverter, that switch needs to be rated at 170 amps. And you are going to get a monster arc when you flip on the inverter. It charges a big bank of capacitors and that's quite a surge. Something to consider.
 

DrHenley

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Texas, do you have any sources for that? I have not seen anywhere that the amp hour rating is amp hours to a dead battery. I've given you a source that says the opposite. I can give you many more.

Brent, I tested four of my inverters today with a DC current tester. The no-load DC draw was between 3-10 watts, with the no-load draw going up roughly proportional with capacity. All had a maximum of between 85-88% efficiency at around 40% capacity. At less than 10% capacity efficiency fell off rapidly, usually down to 60 something. The voltage under a 200 watt load was all over the board: from 110 v to 120 v.

I tested at 25 watts, 35 watts, 90 watts, 200 watts, and 600 watts.
 

Brent S

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A couple of notes.

Doc, first, I think we're not seeing eye-to-eye on how batteries are rated. Let's say you have a 12v 150 amp-hour battery (doesn't matter if flooded/AGM/Li-ion). That 150a-hr is the full capacity, no reserve. So if it's 80%, then you have 120 a-hrs. If it's 50%, you have 75 a-hrs of usable power. Nobody rates a battery at the downgraded rating but rather at the full "dead battery" rating.

Brent, I hope you put a monster switch in there. Whatever the watt rating of the inverter, divide that by 12 (assuming 12v system) and that's how many amps the switch should be rated at. So if you have a 2000 watt inverter, that switch needs to be rated at 170 amps. And you are going to get a monster arc when you flip on the inverter. It charges a big bank of capacitors and that's quite a surge. Something to consider.
I figured on a 125 amp resettable circuit breaker switch. As long as the inverter isn’t under a load when switching there shouldn’t be an arc when switching. This is mainly for shutting it off during the day or all night to help stop the small drains on the batteries.
 

Brent S

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Texas, do you have any sources for that? I have not seen anywhere that the amp hour rating is amp hours to a dead battery. I've given you a source that says the opposite. I can give you many more.

Brent, I tested four of my inverters today with a DC current tester. The no-load DC draw was between 3-10 watts, with the no-load draw going up roughly proportional with capacity. All had a maximum of between 85-88% efficiency at around 40% capacity. At less than 10% capacity efficiency fell off rapidly, usually down to 60 something. The voltage under a 200 watt load was all over the board: from 110 v to 120 v.

I tested at 25 watts, 35 watts, 90 watts, 200 watts, and 600 watts.
That sucks to hear of the efficiency dropping that low on minimal output. I will test mine out with my actual use and see how I can modify my usage to make it as efficient as I reasonably can.
 

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TexasFreedom

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Texas, do you have any sources for that? I have not seen anywhere that the amp hour rating is amp hours to a dead battery. I've given you a source that says the opposite. I can give you many more.
https://web.mit.edu/evt/summary_battery_specifications.pdf

It talks about a 'cutoff voltage'. That is where you lock your amp-hour capacity. It does not factor in the battery technology (ie AGM vs flooded).

http://www.batteryeducation.com/2006/04/what_is_battery.html

Again, they reference the cutoff voltage, and here note it is 10.0v for a 12v lead-acid battery. I can assure you 10.0v does not have 20 nor 50% capacity left over.

https://modernsurvivalblog.com/alternative-energy/battery-state-of-charge-chart/

And there is a table showing that 10% battery capacity for a 12v lead-acid battery is at 11.51 volts. Of course the 11.51v is with no load, with a C/10 or whatever load, a battery at 10% will be meaningfully lower than 11.5v.

I'm not trying to argue, this is how I have always seen batteries rated. It's good to make sure we both are using the right terms and math!
 

DrHenley

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Again, they reference the cutoff voltage, and here note it is 10.0v for a 12v lead-acid battery. I can assure you 10.0v does not have 20 nor 50% capacity left over.
By definition, at the cutoff voltage the Depth of Discharge is 100%. In other words, if you have a 100 amp hour battery, and you have used 100 amp hours, then you have 0 amp hours left at the nominal voltage. Yes it still has some power left in it but no longer at the nominal voltage so it is 0% capacity remaining technically, or 100% DoD.

Depth of Discharge Ratings are about the service life of the battery. If you have a battery that is rated at 100 amp hours and has a service life of 500 cycles at 80% DOD, then you should be able to use 80 amp hours 500 times before it starts to wear out. If you discharge it deeper, you will get fewer cycles. The deeper DoD for AGMs is because they are less prone to sulfation at low voltage.
 

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