Hi from Australia, NSW, Mid North Coast

Spazmor

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Mar 15, 2018
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Hi Legends, first time, long time.

I'm going to setup an off grid homestead on a block of land with no mains power.

Initially the first system I put together will be to power existing shed on weekends. Eventually it will power a house for 2 with a generator for backup.
Our current power consumption is around 16kw per day. If I design our homestead to be efficient I suspect 4-8kw of usable power should suffice.
I have started collecting and processing 18650s. Have come to share and for advice
 
Couple of questions. I have tried searching these and I'm finding discussions and debates but not consensus. Please correct me if I'm wrong

1) If a cell is reaching 50deg Celsius 122F (24degrees ambient 75.2F) during discharge test @ 1A you guys are chucking them (recycling)? or do you cycle it a few times to dissolve the electrolyte?

2) Self discharge test, 1-3weeks? Is it healthy for cells to be stored straight off a recharge @ 4.2v or do you recommend discharging a bit and storing at say 3.8v?
For long term storage, until I start actually drawing from my HBPW, would you suggest 3.7 -3.85V?

3) What operating voltage range do you guys use on powewalls i.e. 3.8-3.2V per cell?
 
Spazmor said:
Couple of questions. I have tried searching these and I'm finding discussions and debates but not consensus. Please correct me if I'm wrong

1) If a cell is reaching 50deg Celsius (24degrees ambient) during discharge test @ 1A you guys are chucking them (recycling)? or do you cycle it a few times to dissolve the electrolyte?

2) Self discharge test, 1-3weeks? Is it healthy for cells to be stored straight off a recharge @ 4.2v or do you recommend discharging a bit and storing at say 3.8v?
For long term storage, until I start actually drawing from my HBPW, would you suggest 3.7 -3.85V?

3) What operating voltage range do you guys use on powewalls i.e. 3.8-3.2V per cell?

1. Which charger are you using?
I have opus, nitecore and digital charger 4s. In this one the cells get hotter but this is due to charger not having a fan.
The opus tends to stay quite cool.
If only some cells are getting that high temp, I would personally ditch them.

2. Yes I go at least a week, sometimes 2-3, then check voltage.
It's fine to store fully charged for that length of time.

3. It's up to you. Personally I do around 3- 4, no more than 4.1
:)
 
Wattsup said:
Spazmor said:
Couple of questions. I have tried searching these and I'm finding discussions and debates but not consensus. Please correct me if I'm wrong

1) If a cell is reaching 50deg Celsius (24degrees ambient) during discharge test @ 1A you guys are chucking them (recycling)? or do you cycle it a few times to dissolve the electrolyte?

2) Self discharge test, 1-3weeks? Is it healthy for cells to be stored straight off a recharge @ 4.2v or do you recommend discharging a bit and storing at say 3.8v?
For long term storage, until I start actually drawing from my HBPW, would you suggest 3.7 -3.85V?

3) What operating voltage range do you guys use on powewalls i.e. 3.8-3.2V per cell?

1. Which charger are you using?
I have opus, nitecore and digital charger 4s. In this one the cells get hotter but this is due to charger not having a fan.
The opus tends to stay quite cool.
If only some cells are getting that high temp, I would personally ditch them.

2. Yes I go at least a week, sometimes 2-3, then check voltage.
It's fine to store fully charged for that length of time.

3. It's up to you. Personally I do around 3- 4, no more than 4.1
:)
Thank you Wattsup,

I have an opus BT-C3100 (4 cell and fan) and two more of the same coming in the post. I have only tested 30 or so cells so far but noticed that by the middle of the discharge they;re all warm. I do have a fancy thermometer somewhere. Haven't measured their temps yet but will, just wondering what benchmark you guys are using.

My idea was to extend the life as much as practical. If I somehow accumulate enough cells to build a pw I'll base the required size off the kindest voltage range. as in if I can get though a day or two by only needing to charge to 3.8 or 4v? and without needing to discharge below 3-3.2v?
Then I'll start building a second pw for my father who will be building a home on our same piece of land

Does that sound reasonable?

Actually so far I've been estimating required size using the following method:
estimated daily usage 6kw (complete guess at this stage)
Average capacity of tested cells 3.7v x 2A = 7.4w
7.4w x 70% usable energy = 5.18w
6000w / 5.18w = 1,158 cells
 
I don't test cells in hot conditions. Usually at night when ambient drops below 30c.

Cells on a 1a discharge test do tend to take in some of the heat from the charger. I personally check my cells at 500ma, even though it is slower. (I use the Opus to test and a number of other chargers to charge)

However, my major concern, is if a cell gets hot while charging. This is a very bad sign. I can't say I have had a cell get over 40c while discharging. But then I do only test in cooler conditions.

As for self discharge, If a cell self discharges toss it. It's no good anymore. Most cells do not, in fact aside of some no name cells, I have yet to have one that does. Most hold 4.12-4.2v for 3 weeks no problem.

I personally don't worry about storage charge. However if you are going to store your batteries in hot conditions this is advisable.
 
Geek said:
I don't test cells in hot conditions. Usually at night when ambient drops below 30c.

Cells on a 1a discharge test do tend to take in some of the heat from the charger. I personally check my cells at 500ma, even though it is slower. (I use the Opus to test and a number of other chargers to charge)

However, my major concern, is if a cell gets hot while charging. This is a very bad sign. I can't say I have had a cell get over 40c while discharging. But then I do only test in cooler conditions.

As for self discharge, If a cell self discharges toss it. It's no good anymore. Most cells do not, in fact aside of some no name cells, I have yet to have one that does. Most hold 4.12-4.2v for 3 weeks no problem.

I personally don't worry about storage charge. However if you are going to store your batteries in hot conditions this is advisable.

I suppose I switched to 1A discharge because I got impatient. 2200mA capacity per cell / 500mA discharge rate = 4.4hrs to test 4 cells at once. Discharging only.
I haven't setup a charger yet so I'm using the Opus for that too. I have a slave job so I'm testing in the evenings only so I was only getting through 1 batch per evening. 4 cells
1,200 cells needed I estimate / 4 per evening = 300 evenings atm providing all the cells pass testing
If I get my other two Opus up and testing.. still 100 evenings and I cant do this every night. So far my recovery rate of cells that are of acceptable quality looks to be 50%...wow, this is a light bulb moment for me.. anyone selling testers?

I suppose I could setup a testing rig in a fire resistant metal tool box that I have on my concrete garage floor and test morning, evening and nights
3 chargers, 3 cycles, 4 cells, 50% recovery= 2 months roughly
Geeking out a bit
 
Spazmor said:
Geek said:
I don't test cells in hot conditions. Usually at night when ambient drops below 30c.

Cells on a 1a discharge test do tend to take in some of the heat from the charger. I personally check my cells at 500ma, even though it is slower. (I use the Opus to test and a number of other chargers to charge)

However, my major concern, is if a cell gets hot while charging. This is a very bad sign. I can't say I have had a cell get over 40c while discharging. But then I do only test in cooler conditions.

As for self discharge, If a cell self discharges toss it. It's no good anymore. Most cells do not, in fact aside of some no name cells, I have yet to have one that does. Most hold 4.12-4.2v for 3 weeks no problem.

I personally don't worry about storage charge. However if you are going to store your batteries in hot conditions this is advisable.

I suppose I switched to 1A discharge because I got impatient. 2200mA capacity per cell / 500mA discharge rate = 4.4hrs to test 4 cells at once. Discharging only.
I haven't setup a charger yet so I'm using the Opus for that too. I have a slave job so I'm testing in the evenings only so I was only getting through 1 batch per evening. 4 cells
1,200 cells needed I estimate / 4 per evening = 300 evenings atm providing all the cells pass testing
If I get my other two Opus up and testing.. still 100 evenings and I cant do this every night. So far my recovery rate of cells that are of acceptable quality looks to be 50%...wow, this is a light bulb moment for me.. anyone selling testers?

I suppose I could setup a testing rig in a fire resistant metal tool box that I have on my concrete garage floor and test morning, evening and nights
3 chargers, 3 cycles, 4 cells, 50% recovery= 2 months roughly
Geeking out a bit

I test 24/7 in my shed, even through the Aussie summer ;)

If things get too hot I set up a fan to blow on the chargers :cool:
 
Interesting what Geek said about the Cells taking heat from the Opus. Last night I noticed that the cells always heat up from right to left. That is, right hand cell gets warm first, then a couple of minutes later the one next to it gets warm then the one next to that etc.
I reordered the same cells and ran test again and same result. Always from the right. My guess is the Opus is getting warm and heating up the cells.

So Geek, the reason you charge at 500ma and not 1A so that you can better identify if cells are getting warm/hot? or is there another reason such as being softer on the cells

Wattsup, I like your idea of using fans. Might have to pinch it. Can you still identify hot ones? Also I like your avatar and no, I didn't pinch it.
 
Spazmor said:
Interesting what Geek said about the Cells taking heat from the Opus. Last night I noticed that the cells always heat up from right to left. That is, right hand cell gets warm first, then a couple of minutes later the one next to it gets warm then the one next to that etc.
I reordered the same cells and ran test again and same result. Always from the right. My guess is the Opus is getting warm and heating up the cells.

So Geek, the reason you charge at 500ma and not 1A so that you can better identify if cells are getting warm/hot? or is there another reason such as being softer on the cells

Wattsup, I like your idea of using fans. Might have to pinch it. Can you still identify hot ones? Also I like your avatar and no, I didn't pinch it.

Well it depends. If you plan to draw 1a from a cell you must test it at 1a. However I don't plan to draw anything like that from my cells.

The other problem with a 1a test, is the opus overheats and stops. This hardly ever happens at 500ma. Also not all 18650s are rated to charge/discharge at more than 1a. So that's why I choose 500ma.

You can place a fan under the opus to avoid this. Also the power supply on the opus doesn't supply enough power to charge at 1a. You can read more about that here. Opus are notorious for blowing power supplies. I suggest that if you are going to charge at 1a, use a different supply.

I charge my batteries with a different charger, and check for self discharge before I bother testing them too. This saves wasting time testing cells that are no good anyway.

As I stated before, if a cell gets hot while charging - at all, this is a very bad sign. If you leave one sit, then try charge it again, sometimes the problem goes away, but I sure wouldn't use it in a big pack. If in doubt throw it out policy applies. You don't want to be looking through a large pack later on for a problem cell, and that's best case.

If you use fans, it is important not to let them blow on the cells. You only want to cool the charger, not the cells. There are people who 3D print new bases for the opus. Or you could just cut a hole in it and sit it on a fan.
 
On optimal storing voltage, I found this on https://batterybro.com

"The 25R spec sheet... to prevent degrading... the recommended voltage is 50 5% of its standard (4.2V) charged state.
This works out to be a range between 3.64V and 3.71V
Other batteries have different ranges, but most are close to ~50% voltage which is usually around ~3.7V."

Someone commented on the article "3.64V and 3.71V if you will top up. If not, consider storing them with a higher charge to accommodate for discharge.
For maximum safety, check their voltage once per month and make sure it does not dip below 3.2V or so"

Appreciate you sharing your process :) I hadn't considered charging then follow by self discharge test but seems like a much more efficient sequence. thank you
Ultimately I'd like to have enough cells to only be demanding a small draw from each. I 'v been discharging at 1A to save time and I thought it might weed out some suspects but so far it hasn't. The only cells I've rejected so far (or put into a different pile) have either not charged at all maybe because they got pressured or too low voltage for the Opus? or their tested mA were too low. I may revisit these cells if I get short on ones that make the first cut.

I haven't had an overheating problem with the Opus yet and I have been charging at 1A. I don't think there has been much heat during charging in cells or Opus.

I have a hacked ATX PS that I'm planing to use for charging. I have 10 x TP4056s on the way. I was hoping to use a TP4056 to charge 2 x 18650 in parallel so if cells were identical they'd receive 500mah each.

Fans still probably a good idea. maybe thats how I can discharge my cells for storage. I do have a 3D printer that I've badly neglected.. might be time to dust it off
 
Got a new batch of lollies to prepare

image_uymuzz.jpg

Still waiting for my tp chargers and couple more testers
 
Welcome! I still want to come for a drive one day :)
 
hbpowerwall said:
Welcome! I still want to come for a drive one day :)

Thanks. You're welcome to.

Come out for a "consult" and claim your fuel.

New development.. I've rescued a bunch of small UPS batteries from the scrapper.

I'm contemplating using these as an interim system until I can source enough 18650s
 
Save what you can and make it work for you :) Your quite the drive away might have to be a weekend trip !
 
hbpowerwall said:
Save what you can and make it work for you :) Your quite the drive away might have to be a weekend trip !

I reckon I have around 6kw usable capacity of lead. that'll do.
yes im probably further away than you realise. Hidden paradise is another 2hrs from where we are. opposite direction from you. def a long weekend trip. we are going down this w/e.

hey, I was considering a PIP so that I could run 18650s if I ever got enough. But.. maybe you could confirm this...the specs say it (4048) uses 50w with no load?! tht seems alot for a smallish system to support. not a deal killer but seems very excesive. do you know if thats accurate?
 
I think it's more like 60watts but it's kinda what you expect from an inverter in the price bracket
 
hbpowerwall said:
I think it's more like 60watts but it's kinda what you expect from an inverter in the price bracket

Wow. 60w is 1.4kw per day.
Did I hear someone say the 4048 was the only charger that could stop charging once batteries are fully charged instead of continuing to float charge them?
Do you know if any other PIPs can do this?

This says draws 11w
 
Spazmor said:
hbpowerwall said:
I think it's more like 60watts but it's kinda what you expect from an inverter in the price bracket

Wow. 60w is 1.4kw per day.
Did I hear someone say the 4048 was the only charger that could stop charging once batteries are fully charged instead of continuing to float charge them?
Do you know if any other PIPs can do this?

This says draws 11w

and I have two ehehbut for the price, two extra panels will cover that - that said is that just the idle self-consumption or under load consumption?I not going to math and work it out.

On the pips you can't change the cccvbut i can do it on my mppsolarpcm60x SOO i set my Pips to charge 0.1v under the PCM60x so the pips stop charging earlier than the PCM60x .

As for 11w Yep, sure *wink*
 
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