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General battery pack/PV planning
#21
@rikh
I don't know how it is possible but one of your links is in my shopping cart?????

At a 48v system with 18650 secondhand bought, the price is the same?
Approx 10 (12)kwh will cost around 1000E, it will last just 4-5 years? 7 if optimistic.
You will need to change the 18650 every 5 years to remain capacity.
Is 2000e, don't forget fuses, solder, cell holders, time.
With both you spend the same money.

Apparently the lifepo are safer, lower risks of a thermal runaway.
No need for fire suppression?


Indeed what can we buy in about ten years?
Still learning English. Learning Li ion and solar technology.

4200 cells in packs Exclamation above 2500mah and 90%soh.
1500 waiting for testing.

Saving for 3 times phoenix inverter 48/3000 230v to gain also 380v
3 chargers?

Time is our enemy, must work to, the sun is our friend, must relax to.
With best regards
Reply
#22
Did some calculations(my case):
1kw storage from secondhand 18650 = 87 euro incl terminals, fuses, holders, tin.
1kw storage from lifepo 201 euro.

From secondhand cells we use 65% to 80% of their capacity to give them a longer life/ more cycles.
But we give up in return some capacity back we can not use.

We also don't know what happened to them before us, we try to give them 2500-4000 cycles (65%)
That would result in a cost of 117 euro per kw storage.
If we are lucky enough to get 1825 cycles out of it, it would be 5 years, one cycle a day.
Option one: make your battery twice bigger than needed= 10 years lifespan? but double the storage costs.
Option two: rebuild everything in five years? dubbles also the costs, 234 euro.
Pick out the good remaining cells?

Those new lifepo have ~3000-4000 cycles.
What if we treat them the same as 18650 and can that extend their lifespan?, so there are not expensive afterall.

Best
Still learning English. Learning Li ion and solar technology.

4200 cells in packs Exclamation above 2500mah and 90%soh.
1500 waiting for testing.

Saving for 3 times phoenix inverter 48/3000 230v to gain also 380v
3 chargers?

Time is our enemy, must work to, the sun is our friend, must relax to.
With best regards
Reply
#23
https://www.aliexpress.com/item/40000017...6b9cjsJGIF

Makes you wonder...is it not to good to be true?
Still learning English. Learning Li ion and solar technology.

4200 cells in packs Exclamation above 2500mah and 90%soh.
1500 waiting for testing.

Saving for 3 times phoenix inverter 48/3000 230v to gain also 380v
3 chargers?

Time is our enemy, must work to, the sun is our friend, must relax to.
With best regards
Reply
#24
How so?

It’s just a BMS board with a pretty heat sink on it… Chinese spec inflation still applies as it would with most of their other ratings on stuff like this.

Id de-rate it by at least 50% for RMS as you should with any other BMS that come from China because everything gets HOT if you try to run them at their advertised currents which really are peaks.
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#25
I also meant in combination with the lifepo batter's
Normal the costs are 3x higher, per battery.
Those battery's are to pretty in price?

Or do we must follow the rule of chinisium ratings? and those cells are just 100A?

If you need for 36kw in 18650, 42 longmons (14s100p) would be 630e extra.

Thanks in advance
Still learning English. Learning Li ion and solar technology.

4200 cells in packs Exclamation above 2500mah and 90%soh.
1500 waiting for testing.

Saving for 3 times phoenix inverter 48/3000 230v to gain also 380v
3 chargers?

Time is our enemy, must work to, the sun is our friend, must relax to.
With best regards
Reply
#26
https://www.aliexpress.com/item/40000223...55f2a61510

Could those cells be any good for us diy?
Cous it is a very good deal.
But are they worth the money, to saving for?
Has anybody bought from that store and tested them?

Is it wise to buy one and test and trust them for a bigger purchase?
Or take a shot at it and hope for a bullseye?

Any info is welcome, thanks in advance
Still learning English. Learning Li ion and solar technology.

4200 cells in packs Exclamation above 2500mah and 90%soh.
1500 waiting for testing.

Saving for 3 times phoenix inverter 48/3000 230v to gain also 380v
3 chargers?

Time is our enemy, must work to, the sun is our friend, must relax to.
With best regards
Reply
#27
(09-02-2019, 08:21 PM)RikH Wrote: About LTO, one word: expensive! Look at this example from BLS on Aliexpress. 60 Yinlongs 40Ah for around USD 3,200 which is 53 each! Looking at the specs I don't know with what inverter these things can be used optimal. Charge cutoff at 2.9 V so lets say your inverter goes up to 62V. 62/2.9 = 21 pieces. Now to get everything out of these Yinlongs (remember you want to go to DoD 100 percent) ........

Hello.

I have built a LTO battery pack, using 110pcs 40Ah 66160H LTOs, 5p22s.
I also have an active 2A balancer, (from Aliexpress) and it works beautifully. (after I modified the start voltage checking)

The three mppt inverters I am using with this pack are Chinese off-grid 5000W230Vac 48V PIP.

I am NOT charging this pack with more than 2.65V/cell, neither discharging to less than 1.9V, that means about  58.4V - 41.8V total, and adjusted the inverter/chargers for these.
If You check the charge/discharge curves for these LTOs, You surely understand why, there is no idea to go higher or lower to get more real capacity.

Do NOT buy the LTOs from Aliexpress, I bought from two aliexpress sellers six cells each, all sold as new A-grade 40Ah cells, all 12 were used fakes with low capacity and new fake 40Ah shrinkwraps.
Luckily I got all my money back from Aliexpress!

I bought these 110 I have now, from an Alibaba-seller, the price was a bit less than 30 US$ apiece.

The pack works beautifully, I have ordered lots more cells to build several identical packs, I am trying to get rid of all my old AGM-batteries.

It is a pity that now I have only 29,990 LTO charge cycles left....  Rolleyes

/piglet

By the way, the capacity is a bit over 10 kWh and the balancer/equalizer can handle all my 5p22s cells.  (24s max)
PhilipW and 100kwh-hunter like this post
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#28
I'm with piglet with regards to the Yinlong LTO's. At this point I own 60 off that were delivered earlier this year, although for complicated reasons I've been unable to work with them yet.  My application is a 24v house battery for a yacht; this means the extra weight and price are only modest considerations, while their safety is a most valuable feature. Plus their relative robustness with respect to under/over charging is important. Nothing worse than the house battery kicking out just as you're entering a narrow rocky channel with an adverse tide/wind.

This reliability means I can reasonably design around a single 24v 200AH bank. Normally with AGM's or LiFePo's I'd split it into two separate independent banks of 100AH each for redundancy. But this introduces an extra BMS, extra contactors, fuses and so-on, plus nasty problems with very high circulating currents if the two banks are paralleled in different SoC's. Overall much simpler and more cost-effective to go with one bank in this application.

@piglet  Can I ask which BMS you are using? I'm planning on the Orion Junior but if you have a better choice I'd be keen to hear.

Cheers
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#29
(09-10-2019, 06:46 AM)PhilipW Wrote: I'm with piglet with regards to the Yinlong LTO's. At this point I own 60 off that were delivered earlier this year, although for complicated reasons I've been unable to work with them yet.  My application is a 24v house battery for a yacht; this means the extra weight and price are only modest considerations, while their safety is a most valuable feature. Plus their relative robustness with respect to under/over charging is important. Nothing worse than the house battery kicking out just as you're entering a narrow rocky channel with an adverse tide/wind.

This reliability means I can reasonably design around a single 24v 200AH bank. Normally with AGM's or LiFePo's I'd split it into two separate independent banks of 100AH each for redundancy. But this introduces an extra BMS, extra contactors, fuses and so-on, plus nasty problems with very high circulating currents if the two banks are paralleled in different SoC's. Overall much simpler and more cost-effective to go with one bank in this application.

@piglet  Can I ask which BMS you are using? I'm planning on the Orion Junior but if you have a better choice I'd be keen to hear.

Cheers
I am not using a real BMS at all.  Only an equalizer/balancer and some automatic circuit breakers.

I do not know anything about this Orion Junior, but check this!

https://secondlifestorage.com/showthread...1#pid51481

The modification took about one minute.

I have bought two of these 2A bluetooth equalizer/balancers, one from eBay and the other from Aliexpress.

A bit over 100 Euros for one.

Both needed to be modified, but maybe the latest versions already work without any modification, hope the manufacturer has fixed the first LTO-cell voltage problem.

It takes a while for this to adjust the voltages, but during nights (no sun, no charging!) this adjusts all the 22  5P cellgroups voltage differences to about 0.005V!
I have this on all the time.

The bluetooth works beautifully too.

Remember to check the internal resistance of Your cells, the closer to each other, the better, the lower, the better.
My LTOs are from 0.24 to 0.33milliOhm.

I got about 6 that had 0.4 milliOhms and a bit over, but I am using those for other things.
If I happen to get many more of those, then I will build a pack using only those.

/piglet
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