I do not have unfortunately.

FrancisAdl:


Do you have any fairly used inverter for sale?

NiyiOmoIyunade:
I think the issue may be comparing these batteries based on their burst load handling capabilities.

Let us consider a more typical scenario where the loads are average for typical home use.

48v 400Ah is about 19.2kwh stored - the C20 discharge rate for this is about 960w. Say I run an average 800w load on this battery bank,. I can do so happily for about 12 hours before reaching 50% DoD. In this scenario a good AGM battery will last well over 2 years before it conks. Key to note an AGM will easily handle burst loads up to 25% of capacity for short periods.

Now for a 48v 50Ah Lithium bank, I have 2.4kwh stored - 90% (to use your numbers) is about 2.16kwh - so I can run my 800w load for about 3 hours before exhausting the useable energy in the battery.

12hours backup with AGM looks more like a typical usage scenario vs 3hours with Lithium and to put this on an equivalent footing I would need at least 48v 200Ah to 230Ah of Lithium batteries to give thesame backup time.

Cycle life for a good quality AGM is anywhere from 600 to 1,750 cycles (easily 2 to 5 years) if used within the recommended design range.

If I take Quanta as representative of a good AGM and BYD as representative of a good Lithium based battery, I am looking at a 3:1 cost ratio for Lithium vs AGM.

The average guy on the street would struggle to pay 3 times the regular price to acquire Lithium batteries to secure him thesame capacity but with longer service life. This is the struggle I am in currently trying to upgrade my 48v 800Ah battery bank to Lithium - I am looking at 48v 500Ah of Lithium to give me thesame useable capacity with a slight buffer built in and it is clear to me that I am extremely unwilling to afford that much for a battery or pay that much for Lithium.

niyi,
i agree with you totally.
my experience with new technology is its tendency to being 'souped up' to serve the needs of whoever is
peddling it. at the initial time lithium broke into the scene, we were told it could be drained down to 0% dod
without any issues at all, and thus we would need exactly half the capacity of lead-acid batteries as replacement
for our battery banks. over this short span of time however, i've seen changing dod figures. from 90% to 85% as
the sweet spot where maximum number of cycles would be best guaranteed. this for me is a red flag and it simply
tells me that all is not settled yet as far as this nascent technology is concerned. so, if I have a lead-acid bank that
i'm maintaining at 50% dod, and i have lithium which is 3 or 4 times the cost of lead-acid and I can only go 85%
for best results, what difference does that make to me?
most of the hype of lithium revolves around its superlative number of cycles and its ability to charge faster while
needing lesser number of solar panels to do so. maybe that would strike a chord with someone looking to go solar
for the first time but for an enthusiast like yours truly already heavily invested in an oversized array and running an
agm bank pushing nearly 7 years, it would take a little more convincing that lithium is actually worth the effort -
and cost.

GeorgeD1:

niyi,
i agree with you totally.
my experience with new technology is its tendency to being 'souped up' to serve the needs of whoever is
peddling it. at the initial time lithium broke into the scene, we were told it could be drained down to 0% dod
without any issues at all, and thus we would need exactly half the capacity of lead-acid batteries as replacement
for our battery banks. over this short span of time however, i've seen changing dod figures. from 90% to 85% as
the sweet spot where maximum number of cycles would be best guaranteed. this for me is a red flag and it simply
tells me that all is not settled yet as far as this nascent technology is concerned. so, if I have a lead-acid bank that
i'm maintaining at 50% dod, and i have lithium which is 3 or 4 times the cost of lead-acid and I can only go 85%
for best results, what difference does that make to me?
most of the hype of lithium revolves around its superlative number of cycles and its ability to charge faster while
needing lesser number of solar panels to do so. maybe that would strike a chord with someone looking to go solar
for the first time but for an enthusiast like yours truly already heavily invested in an oversized array and running an
agm bank pushing nearly 7 years, it would take a little more convincing that lithium is actually worth the effort -
and cost.

GeorgeD, I can always count on you to speak my mind before I do. What's more, lithium is considerably more dangerous. In the background, I've been messing with lithium (I'm that kind of DIY guy who keeps tinkering with things even when they're optimally tuned). I've had two remarkable experiences. In one, I had to bail while I watched a small bank burn brilliantly for a few minutes. In the other, I got a pretty nasty burn.
The hazards are real! I did nothing out of the ordinary other than pushing the limits.

I've avoided joining the lithium vs. lead chemistry wars simply because it's pointless. They both have their applications. If you're a power user with short bursts of high power demand or space and weight mean a lot to you, lithium is your guy. If you're old school and you want that trusty bank you can mess around with (ignore what people tell you about PbSO₄ being unstable) that can last you the whole day on reasonable drain without selling your kidney (for some of us), please do FLA or AGM.

- Before I go, I should mention the random cell failure which plagues lead chemistry cells also plagues lithium.
- Dry joints appear (akin to failure of connections between cells for lead).
- When hot, while thermal runaway is not an issue but . . . they get very hot, very fast, very much without tell tale signs.
- You thought your days of babysitting your bank were over? Think again!
- Balancers go poof!

All the aforementioned are things I have personally experienced in a 6 year window.

Anyway, the good, the bad, the ugly. Do what suits you and choose the one that would work for you. Avoid the overwhelming urge to do something simply because everyone is doing it. Unless for experimental purposes or "the experience".

Peace! I'm out.

Saipro:

GeorgeD, I can always count on you to speak my mind before I do. What's more, lithium is considerably more dangerous. In the background, I've been messing with lithium (I'm that kind of DIY guy who keeps tinkering with things even when they're optimally tuned). I've had two remarkable experiences. In one, I had to bail while I watched a small bank burn brilliantly for a few minutes. In the other, I got a pretty nasty burn.
The hazards are real! I did nothing out of the ordinary other than pushing the limits.

You don't mess with lithium and you definitely never push lithium beyond its limits. It's result could be fatal. Only people who know know what they are doing should ever mess with lithium. Lithium should never and I mean never be over charged (4.2v for Li-ion, and 3.65v for LiFeP04) and the use of battery management system is crucial. If you can abide by these rules, then you will have no safety concerns.

I've avoided joining the lithium vs. lead chemistry wars simply because it's pointless. They both have their applications. If you're a power user with short bursts of high power demand or space and weight mean a lot to you, lithium is your guy. If you're old school and you want that trusty bank you can mess around with (ignore what people tell you about PbSO₄ being unstable) that can last you the whole day on reasonable drain without selling your kidney (for some of us), please do FLA or AGM.

It's good to join the lithium vs lead chemistry debate, so we can all share experiences. I am of the strong belief that the solution to our energy problem in Nigeria is solar, as the energy companies are highly incompetent apart from being corrupt.

Lithium is obviously more dangerous that lead, because you are packing more energy in a smaller amount of space (and mass), so the chemistry is more unstable than lead.
Having said that, the future of energy storage is lithium. Without lithium we would never have had the cell phone or smart phone. No other chemistry would have been able to pack such huge amount of power in such a small device. Same thing with laptops. (Imagine running a laptop computer with lead batteries). So it will also be with solar energy storage. As lithium batteries become more widely used and safer, it's prices will come down. In terms of safety new LiFeP04 is relatively safe, they don't explode with abuse like Li-ion.

- Before I go, I should mention the random cell failure which plagues lead chemistry cells also plagues lithium.
- Dry joints appear (akin to failure of connections between cells for lead).
- When hot, while thermal runaway is not an issue but . . . they get very hot, very fast, very much without tell tale signs.
- You thought your days of babysitting your bank were over? Think again!
- Balancers go poof!

All the aforementioned are things I have personally experienced in a 6 year window.

Anyway, the good, the bad, the ugly. Do what suits you and choose the one that would work for you. Avoid the overwhelming urge to do something simply because everyone is doing it. Unless for experimental purposes or "the experience".

Peace! I'm out.

To guard against BMS failure, I recommend you don't go for cheap $2 BMS on alibaba. Go for reputable BMS with lots of safety features. In addition I recommend adding a battery monitor that bleeps if one of the cells go off balance. They are quite cheap (less than $10). New cells that was balanced initially don't go off balance easily. Furthermore, drawing less than C/0.2 will keep your cells from going off balanced.

Introducing Lithium Titanate (Li2TiO3) batteries. These are future technologies for electric storage. They have a cycle of over 20,000 cycles and can be drained to 95% DOD. 20,000 cycles means 54 years if cycled everyday.
This battery would probably outlive the owner. The draw back right now is the huge cost and the usual lithium chemistry issues.

GeorgeD1:

.................an enthusiast like yours truly already heavily invested in an oversized array and running an
agm bank pushing nearly 7 years , it would take a little more convincing that lithium is actually worth the effort and cost.

@GeorgeD1

nearly 7 Yearsssssssssssssss!!! That is quite commendable. This confirms once again that with better management and right sizing, one can do more cycles with a Battery Bank setup. Honestly, your Zenith Batteries are rare gem. Which they are still in circulation.

Happy democracy day friends

wirinet:
Introducing Lithium Titanate (Li2TiO3) batteries. These are future technologies for electric storage. They have a cycle of over 20,000 cycles and can be drained to 95% DOD. 20,000 cycles means 54 years if cycled everyday.
This battery would probably outlive the owner. The draw back right now is the huge cost and the usual lithium chemistry issues.

Yeah, you can even drill through it without any risk of explosion.

I recently watched a youtube review of this battery in which the youtuber bought the batteries at Aliexpress at a cost of $276 or approximately N100k with free shipping for a lot of 6. The capacity was quoted to be 2.4V @30AH each cell.

wirinet:

You don't mess with lithium and you definitely never push lithium beyond its limits. It's result could be fatal. Only people who know know what they are doing should ever mess with lithium. Lithium should never and I mean never be over charged (4.2v for Li-ion, and 3.65v for LiFeP04) and the use of battery management system is crucial. If you can abide by these rules, then you will have no safety concerns.



It's good to join the lithium vs lead chemistry debate, so we can all share experiences. I am of the strong belief that the solution to our energy problem in Nigeria is solar, as the energy companies are highly incompetent apart from being corrupt.

Lithium is obviously more dangerous that lead, because you are packing more energy in a smaller amount of space (and mass), so the chemistry is more unstable than lead.
Having said that, the future of energy storage is lithium. Without lithium we would never have had the cell phone or smart phone. No other chemistry would have been able to pack such huge amount of power in such a small device. Same thing with laptops. (Imagine running a laptop computer with lead batteries). So it will also be with solar energy storage. As lithium batteries become more widely used and safer, it's prices will come down. In terms of safety new LiFeP04 is relatively safe, they don't explode with abuse like Li-ion.

To guard against BMS failure, I recommend you don't go for cheap $2 BMS on alibaba. Go for reputable BMS with lots of safety features. In addition I recommend adding a battery monitor that bleeps if one of the cells go off balance. They are quite cheap (less than $10). New cells that was balanced initially don't go off balance easily. Furthermore, drawing less than C/0.2 will keep your cells from going off balanced.

You forgot the most important application of it and the best at that: EV's. The high mileages now available on them couldn't hv been possible w/out lithium. An Off-road truck is debuting in a few months time with a 650KM range on a single charge...



https://www.youtube.com/watch?v=Qc64gMpReOU

wirinet:

You don't mess with lithium and you definitely never push lithium beyond its limits. It's result could be fatal. Only people who know know what they are doing should ever mess with lithium. Lithium should never and I mean never be over charged (4.2v for Li-ion, and 3.65v for LiFeP04) and the use of battery management system is crucial. If you can abide by these rules, then you will have no safety concerns.



It's good to join the lithium vs lead chemistry debate, so we can all share experiences. I am of the strong belief that the solution to our energy problem in Nigeria is solar, as the energy companies are highly incompetent apart from being corrupt.

Lithium is obviously more dangerous that lead, because you are packing more energy in a smaller amount of space (and mass), so the chemistry is more unstable than lead.
Having said that, the future of energy storage is lithium. Without lithium we would never have had the cell phone or smart phone. No other chemistry would have been able to pack such huge amount of power in such a small device. Same thing with laptops. (Imagine running a laptop computer with lead batteries). So it will also be with solar energy storage. As lithium batteries become more widely used and safer, it's prices will come down. In terms of safety new LiFeP04 is relatively safe, they don't explode with abuse like Li-ion.

To guard against BMS failure, I recommend you don't go for cheap $2 BMS on alibaba. Go for reputable BMS with lots of safety features. In addition I recommend adding a battery monitor that bleeps if one of the cells go off balance. They are quite cheap (less than $10). New cells that was balanced initially don't go off balance easily. Furthermore, drawing less than C/0.2 will keep your cells from going off balanced.

i think you are not getting the bane of contention sir. saipro hasn't said li-ion technology should be discarded, but as far as renewable energy use is concerned, at this time, li-ion mat not be ready for massive real word application....The aspects you highlighted where li-ion tech is being used like mobile devices and co are superb applications of them because of better weight/energy density characteristic....ordinary rechargeable fans still go back to lead acid use. That should say something about the application of lithium to the common user yet.

my two cents.

mctfopt:



Yeah, you can even drill through it without any risk of explosion.

I recently watched a youtube review of this battery in which the youtuber bought the batteries at Aliexpress at a cost of $276 or approximately N100k with free shipping for a lot of 6. The capacity was quoted to be 2.4V @30AH each cell.

100k for a 14.4v 30ahr battery?

maybe for aerial vehicles or something like dat oh, but for energy storage for home power supply? its well ni oo

Trippledots:


i think you are not getting the bane of contention sir. saipro hasn't said li-ion technology should be discarded, but as far as renewable energy use is concerned, at this time, li-ion mat not be ready for massive real word application....The aspects you highlighted where li-ion tech is being used like mobile devices and co are superb applications of them because of better weight/energy density characteristic....ordinary rechargeable fans still go back to lead acid use. That should say something about the application of lithium to the common user yet.

my two cents.

That's where we disagree. I contend that right now lithium batteries is the best for solar applications, even rechargeable fans and rechargeable anything. They still employ lead in rechargeable fans because of costs and business strategy issues. Lead is cheaper and does not require complicated BMS, and also it pays battery manufacturers for you to replace lead battery every year. ( most times every 6 months). Remember your laptop batteries with cooling fans employ lithium batteries.

As chuckdee mentioned below, a road truck will debuting in a few months time with a 650KM range on a single charge. Now, if a truck with with fans, lights and all paraphernalia of a truck can run such a distance, what are your average home appliances? Now, try running a car or even a drone with lead batteries.
I know people are slow to accept new technologies and lead has been around for centuries, but believe me, lithium will replace lead very soon.

Trippledots:



100k for a 14.4v 30ahr battery?

maybe for aerial vehicles or something like dat oh, but for energy storage for home power supply? its well ni oo

You can charge it under 6 minutes and get 20,000 cycles. That, I think may be enough to dole out that money

mctfopt:


You can charge it under 6 minutes and get 20,000 cycles. That, I think may be enough to dole out that money

I agree that it depends on situations and applications. Imagine NEPA loadshedding your house to 1 hour supply per day. You virtually "download" your whole 24 hour electric usage under 10 minutes.
Also imagine traveling long distance on an electric car and running out of charge. Would it not be a dream to be able to drive into a charging station and get a full charge at the same time it takes to fill a traditional petrol engine car.

Tchyfingy:
Please, how good is luminous Cruze+ 4kva inverter? Does it have low idle current? How does it compare to TBB Pure Sinewave Inverter Charger 4kW 48VDC? I urgently need a new inverter. Candid advice will be well appreciated.

the luminous have low idle consuption and low charging current. i dont know about the other brand.

i am team lithium
i am also team lead acid

wirinet:

That's where we disagree. I contend that right now lithium batteries is the best for solar applications, even rechargeable fans and rechargeable anything. They still employ lead in rechargeable fans because of costs and business strategy issues. Lead is cheaper and does not require complicated BMS, and also it pays battery manufacturers for you to replace lead battery every year. ( most times every 6 months). Remember your laptop batteries with cooling fans employ lithium batteries.

As chuckdee mentioned below, a road truck will debuting in a few months time with a 650KM range on a single charge. Now, if a truck with with fans, lights and all paraphernalia of a truck can run such a distance, what are your average home appliances? Now, try running a car or even a drone with lead batteries.
I know people are slow to accept new technologies and lead has been around for centuries, but believe me, lithium will replace lead very soon.

What is BMS?

Well, below is the strange way I connected lithium batteries from "dead laptop batteries" to my rechargeable fan. The fan can now blow at very high speed for more than 24hours non stop. It's been working like that for 3 months now, no issues at all and I didn't use BMS anywhere.

I will never use that rubbish they call battery that came with the fan again! I wondered why they use the battery in the first place. Something that barely blows for 5 hours at the lowest speed.

hotdealz:
What is BMS?

Battery Management System. An electronic circuit or device to make sure your batteries operate within recommended limits, like operating voltage, and to ensure none of the cells (in series) go out of balance.

wirinet:

Battery Management System. An electronic circuit or device to make sure your batteries operate within recommended limits, like operating voltage, and to ensure none of the cells (in series) go out of balance.

Hmm... Interesting.

wirinet:

I agree that it depends on situations and applications. Imagine NEPA loadshedding your house to 1 hour supply per day. You virtually "download" your whole 24 hour electric usage under 10 minutes.
Also imagine traveling long distance on an electric car and running out of charge. Would it not be a dream to be able to drive into a charging station and get a full charge at the same time it takes to fill a traditional petrol engine car.

I love the charging rate. Of course, one can buy it if he can afford it. If it lives up to the specification, it'd pay for itself over time. But of course, anyone can always buy the type of batteries they can afford without breaking the bank. I may give this a try. Fingers crossed.

hotdealz:
What is BMS?

Well, below is the strange way I connected lithium batteries from "dead laptop batteries" to my rechargeable fan. The fan can now blow at very high speed for more than 24hours non stop. It's been working like that for 3 months now, no issues at all and I didn't use BMS anywhere.

I will never use that rubbish they call battery that came with the fan again! I wondered why they use the battery in the first place. Something that barely blows for 5 hours at the lowest speed.

Do you have a spot welder? I noticed one of those pink batteries that look like Samsung batteries were spot welded.

How many of the 18650s did you use and what is the wattage of the fan?

I'm also interested to know the voltage and amps of the charger you used for charging the batteries.

I'm just curious about anything renewable energy so pardon me for the questions

hotdealz:
What is BMS?

Well, below is the strange way I connected lithium batteries from "dead laptop batteries" to my rechargeable fan. The fan can now blow at very high speed for more than 24hours non stop. It's been working like that for 3 months now, no issues at all and I didn't use BMS anywhere.

I will never use that rubbish they call battery that came with the fan again! I wondered why they use the battery in the first place. Something that barely blows for 5 hours at the lowest speed.

hope you have a fire extinguisher nearby?

hotdealz:
What is BMS?

Well, below is the strange way I connected lithium batteries from "dead laptop batteries" to my rechargeable fan. The fan can now blow at very high speed for more than 24hours non stop. It's been working like that for 3 months now, no issues at all and I didn't use BMS anywhere.

I will never use that rubbish they call battery that came with the fan again! I wondered why they use the battery in the first place. Something that barely blows for 5 hours at the lowest speed.

My brother, that your contraption is very dangerous o. You could burn down your house. Li-ion batteries are the worst ones to toy with. They explode and almost nothing can quench the fire.

The idea is good but your execution is very poor. First you need to determine the voltage requirement of your fan (I suspect 6v ), you now need to connect your li-ion batteries in series to achieve around 6v. 2 li-ion batteries in series would give 7.4v nominal and 8.4v maximum. Now, you must never charge above 8.4v. I need to know the charger you are using to charge the batteries.

Laptop batteries are usually 3 batteries in series, which is 11.1 nominal and 12.6 maximum. If you are using a condemned laptop battery one of the series of cells is probably bad.

I see you bypassed the BMS. (The BMS is the small circuit cased in plastic attached to the cells). Your cells is probably out of balance. The luck you might have is that the cells could have protection circuit embedded in it which will just stop the cells from working instead of exploding.
Please get someone with a knowledge of lithium batteries to look at your set up

dragnet:

hope you have a fire extinguisher nearby?

Chineke!

But the batteries doesn't even get hot o. Would it still explode just like that?

wirinet:


My brother, that your contraption is very dangerous o. You could burn down your house. Li-ion batteries are the worst ones to toy with. They explode and almost nothing can quench the fire.

The idea is good but your execution is very poor. First you need to determine the voltage requirement of your fan (I suspect 6v ), you now need to connect your li-ion batteries in series to achieve around 6v. 2 li-ion batteries in series would give 7.4v nominal and 8.4v maximum. Now, you must never charge above 8.4v. I need to know the charger you are using to charge the batteries.

Laptop batteries are usually 3 batteries in series, which is 11.1 nominal and 12.6 maximum. If you are using a condemned laptop battery one of the series of cells is probably bad.

I see you bypassed the BMS. (The BMS is the small circuit cased in plastic attached to the cells). Your cells is probably out of balance. The luck you might have is that the cells could have protection circuit embedded in it which will just stop the cells from working instead of exploding.
Please get someone with a knowledge of lithium batteries to look at your set up

below is the battery that came with the fan. It says 12V.

I'm not using any external charger to charge it. It's a rechargeable fan. I'm using the inbuilt charger, I guess.

I disconnected the battery that came with it and connected the laptop battery directly to the wires.

I think you should rather ask how he got it to work than this too many ways why-it-will-never-work!

wirinet:


My brother, that your contraption is very dangerous o. You could burn down your house. Li-ion batteries are the worst ones to toy with. They explode and almost nothing can quench the fire.

The idea is good but your execution is very poor. First you need to determine the voltage requirement of your fan (I suspect 6v ), you now need to connect your li-ion batteries in series to achieve around 6v. 2 li-ion batteries in series would give 7.4v nominal and 8.4v maximum. Now, you must never charge above 8.4v. I need to know the charger you are using to charge the batteries.

Laptop batteries are usually 3 batteries in series, which is 11.1 nominal and 12.6 maximum. If you are using a condemned laptop battery one of the series of cells is probably bad.

I see you bypassed the BMS. (The BMS is the small circuit cased in plastic attached to the cells). Your cells is probably out of balance. The luck you might have is that the cells could have protection circuit embedded in it which will just stop the cells from working instead of exploding.
Please get someone with a knowledge of lithium batteries to look at your set up

hotdealz:
below is the battery that came with the fan. It says 12V.

I'm not using any external charger to charge it. It's a rechargeable fan. I'm using the inbuilt charger, I guess.

I disconnected the battery that came with it and connected the laptop battery directly to the wires.

The charger that came with the fan is a lead acid charger, which probably charge at about 13.9v. That's far too high for a 3S li-ion battery. At 13.9 each cell receives about 4.6v . That is a recipe for disaster. Your charging voltage should never exceed 12.6v. If you had connected through the BMS, you will not have any problem but you are connecting direct. You also seem to connect 3 of such laptop batteries in parallel, making the whole battery set up 3S6P.

I repeat get someone who is knowledgeable in lithium batteries to do the set up for you. I just pray the cells themselves are protected.

SolnergyPower:
I think you should rather ask how he got it to work than this too many ways why-it-will-never-work!

Please try and read and comprehend before hiting the submit button. The workability of the set up was not in discussion, I was talking about the safety. He had no safety measures whatsoever.

wirinet:


The charger that came with the fan is a lead acid charger, which probably charge at about 13.9v. That's far too high for a 3S li-ion battery. At 13.9 each cell receives about 4.6v . That is a recipe for disaster. Your charging voltage should never exceed 12.6v. If you had connected through the BMS, you will not have any problem but you are connecting direct. You also seem to connect 3 of such laptop batteries in parallel, making the whole battery set up 3S6P.

I repeat get someone who is knowledgeable in lithium batteries to do the set up for you. I just pray the cells themselves are protected.

Is the BMS the small board inside the laptop battery? I always cut it off and throw away. I'm a newbie in this.

There is no way I can know if it's fully charged or not so i stop charging after 5hours regardless of if it's fully charged or not. Then use it till its completely down before recharging for 5hours again.

@ bolded lines

Indeed simplicity is the hallmark of genius!!!

I am amazed that you got this to work at all [without incident/accident] while appearing not to fully grasp how everything comes together.

Kudos to you!!! But please take all the guidance you have received into account for safety's sake at least.

hotdealz:
Is the BMS the small board inside the laptop battery? I always cut it off and throw away. [/b]I'm a newbie in this.

[b] There is no way I can know if it's fully charged or not so i stop charging after 5hours regardless of if it's fully charged or not. Then use it till its completely down before recharging for 5hours again.

hotdealz:
What is BMS?

Well, below is the strange way I connected lithium batteries from "dead laptop batteries" to my rechargeable fan. The fan can now blow at very high speed for more than 24hours non stop. It's been working like that for 3 months now, no issues at all and I didn't use BMS anywhere.

I will never use that rubbish they call battery that came with the fan again! I wondered why they use the battery in the first place. Something that barely blows for 5 hours at the lowest speed.

PLEASE PLEASE PLEASE i dey beg u, that setup is waiting to explode.. your fan is 12volt i guess, u are using 3 in series as early said, so the lithium at full will only allow 12.6v, but your charger will go up to 13v or so, you might lucky so far cause maybe the bank is large so the battery never gets to full depending on the charger ..... I beg help yourself. if you still want to go the rugged way, put a volt display so you can monitor and shut it down when it reaches about 12.4v... but no be me advice u o... another problem u might face is when on bat dies out and the charger is still trying to meet up 12v, imagine trying to push 12v into 7.4v cause one has failed...

i can help u, if u send the bat to me, i will rebuild it with a bms so u can go out of your home in peace...

hotdealz:
Is the BMS the small board inside the laptop battery? I always cut it off and throw away. I'm a newbie in this.

There is no way I can know if it's fully charged or not so i stop charging after 5hours regardless of if it's fully charged or not. Then use it till its completely down before recharging for 5hours again.

"completely down" you are killing the life cycles as well.... what voltage is "completely down"?