Solar lighting - What do the specs really mean, how much light can I actually expect to get and for how long?

[Muhendis]

21 hours ago, Susco said:

There is no protection that I can perceive.

Interesting observation. I had a look on google to learn more about this protection and this is what I found. 

https://lygte-info.dk/info/battery protection UK.html

[Crossy]

7 minutes ago, Muhendis said:

Interesting observation. I had a look on google to learn more about this protection and this is what I found. 

https://lygte-info.dk/info/battery protection UK.html

 

Good find.

 

Sub-link from the above has some clues on how to check if your unknown cell has protection electronics.

 

https://lygte-info.dk/info/isMyBatteryProtected UK.html

 

 

[Susco]

12 minutes ago, Muhendis said:

Interesting observation. I had a look on google to learn more about this protection and this is what I found. 

https://lygte-info.dk/info/battery protection UK.html

 

3 minutes ago, Crossy said:

 

Good find.

 

Sub-link from the above has some clues on how to check if your unknown cell has protection electronics.

 

https://lygte-info.dk/info/isMyBatteryProtected UK.html

 

 

 

Not sure what you try to say, but going by my observations, and comparing the size of my battery and the size quoted in the link, it looks to me as that my battery has no protection.

 

Correct or not?

[Susco]

13 hours ago, Crossy said:

Our experience with real panels and the real world puts that nearer panel rating * 3.2 = 2.5 * 3.2 = 8 Wh.

 

So taking the optimistic number you need 12.5/3.6 =  3.6Ah for a 3.6V battery in order to store everything the panel can make. Anything bigger than 4Ah is just wasting capacity.

 

 

So going by your real world calculation, which I believe to be correct, a 2200 mAh battery is about the maximum my panel can charge?

 

13 hours ago, Susco said:

Considering LifePo4 batteries as well, as I know the advantage of them in my airsoft gun, but will the lights work properly on 3.2V?

 

I see 6000 mAh lifePo4 batteries listed on Lazada for less than 100 Baht, about the same price as a 3400 mAh Li-ion battery. Is this price realistic, or be fake without doubts?

 

What are your thoughts about this?

[Crossy]

5 minutes ago, Susco said:

So going by your real world calculation, which I believe to be correct, a 2200 mAh battery is about the maximum my panel can charge?

 

I wouldn't hurt to try a bigger cell, it certainly won't damage anything and on a really bright day you could get some extra charge. But generally I think you're right, 2,200 is probably optimal.

 

I got some 6,000mAh 32650 cells from The Power Idea for 110 Baht and they are definitely genuine (measured).

 

I don't see 18650s of that capacity being "real".

[Susco]

29 minutes ago, Crossy said:

But generally I think you're right, 2,200 is probably optimal.

 

Still going by your numbers Crossy.

 

In case of a LifePo4 battery the panel should be able to create 8/3.2= 2.5 Ah

 

So would a LifePo4 battery with a capacity of 2500 mAh, be any significant advantage over a 2200 mAh Li-ion battery?

 

My opinion, as a layman, is not, because it will get much faster to the 2.7V level, at which my lights shine much less bright.

 

Is that a correct assumption?

[maxpower]

2 hours ago, sometimewoodworker said:

There is no visual way to tell if an 18650, you show 1, has protection without destroying it. The protection is under the end cap if it’s fitted and the size is the same with or without protection.

 

[maxpower]

1 hour ago, Susco said:

So would a LifePo4 battery with a capacity of 2500 mAh, be any significant advantage over a 2200 mAh Li-ion battery?

 

Your light is setup to charge Li-ion not LifePo4. 

 

Take out the existing cell and replace it with one of these.

 

https://www.lazada.co.th/products/18650-panasonic-liitokala-3400-mah-liitokala-1-p-i1103988743-s2514868108.html?spm=a2o4m.seller.list.13.5a985f83XGmkE6&mp=1

 

The answer to your capacity questions will appear over time.

 

The alternative is to measure the real solar output and average light consumption then decide if there is any useful surplus.

[Susco]

31 minutes ago, maxpower said:

 

Your light is setup to charge Li-ion not LifePo4. 

 

Take out the existing cell and replace it with one of these.

 

https://www.lazada.co.th/products/18650-panasonic-liitokala-3400-mah-liitokala-1-p-i1103988743-s2514868108.html?spm=a2o4m.seller.list.13.5a985f83XGmkE6&mp=1

 

The answer to your capacity questions will appear over time.

 

The alternative is to measure the real solar output and average light consumption then decide if there is any useful surplus.

 

Thanks, I have seen that product before. What is the difference between the (p) battery in your link and the (j) battery from the same shop?

 

https://www.lazada.co.th/products/18650-panasonic-ncr18650b-1-j-i1104000112-s2514776525.html?

 

The light use 0.12A , but I have no idea how to measure the panel real output

 

 

[sometimewoodworker]

2 hours ago, maxpower said:

 

Your protected cell is not an 18650 it could be an undersized 18700.

The 18 is the diameter and the length must be at or close to 65mm long, 69.6mm is far from the required length.

 

So as I said an 18650 protected or not is exactly the same length and diameter and there is no way to tell from looking at the cell if it is protected or not 

Edited December 28, 2020 by sometimewoodworker

[maxpower]

32 minutes ago, sometimewoodworker said:

Your protected cell is not an 18650 it could be an undersized 18700.

The 18 is the diameter and the length must be at or close to 65mm long

 

Its a 18650 cell with protection circuit added. The cell remains 18650, call the protection whatever you like. The cell is the size spec, protection is an option that can change package size.

 

I could go to a nearby factory and ask them to roll short cells and cap them myself but I would not have a protected 18650.

[maxpower]

1 hour ago, Susco said:

 

Thanks, I have seen that product before. What is the difference between the (p) battery in your link and the (j) battery from the same shop?

 

https://www.lazada.co.th/products/18650-panasonic-ncr18650b-1-j-i1104000112-s2514776525.html?

 

The light use 0.12A , but I have no idea how to measure the panel real output

 

 

 

I appreciate you don't have the facility make accurate tests which is why I suggest the easy route of changing the battery for a lager capacity and maybe better quality. Not an expensive experiment.

[sometimewoodworker]

1 hour ago, maxpower said:

Its a 18650 cell with protection circuit added. The cell remains 18650, call the protection whatever you like. The cell is the size spec, protection is an option that can change package size.

You have a particularly long cell. The length is no guarantee that protection is or is not included, yours also doesn’t have a flat end so adding to the length 

[Crossy]

The link I posted earlier gives some clues as to how to check if your cells are protected or not but it seems more than somewhat variable.

 

https://lygte-info.dk/info/isMyBatteryProtected UK.html

 

 

 

[maxpower]

1 hour ago, sometimewoodworker said:

You have a particularly long cell. The length is no guarantee that protection is or is not included, yours also doesn’t have a flat end so adding to the length 

 

No I don't show a long cell, its a standard 65mm 18650 with optional protection circuit tacked on the end. It could be down the side or floating on a lead.

 

The appearance of the flat end as you call it come from the additional insulation cap.

 

It now becomes a protected 18650 cell and questions can be raised about size variation.

 

Protected 18650 cells have no standard size.

 

There was no mention in my replies about length indicating the presence of a protection circuit, so no need to cloud the subject.
 

[sometimewoodworker]

1 hour ago, maxpower said:

No I don't show a long cell, its a standard 65mm 18650

If you take a look at sites that have cataloged 18650 cells it is among the longest shown, so yes at 69.6 it is long

 

 

[Crossy]

4 minutes ago, sometimewoodworker said:

If you take a look at sites that have cataloged 18650 cells it is among the longest shown, so yes at 69.6 it is long

 

Any indication which of those are protected and which are not?

 

It certainly seems to be a grey and confusing area.

[sometimewoodworker]

5 hours ago, Crossy said:

 

Any indication which of those are protected and which are not?

 

It certainly seems to be a grey and confusing area.

The page has that info for all the tested ones

https://lygte-info.dk/info/Battery 18650 UK.html

And notes that the 69.5mm cell is an 18700

 

[Muhendis]

I notice there is significant variation in claimed capacity and measured performance of the so called 18650 cells and now we have another size, 18700 which is the protected 18650 but with variations in length as well as capacity. There seems to be no established standard. 

[Crossy]

34 minutes ago, Muhendis said:

There seems to be no established standard.

 

I think this is rapidly becoming apparent ????

 

I don't know about the 18*** cells but the 32700s I have are NOT protected 32650s they are actually larger capacity (6,000mAh vs 5,000mAh) but still without protection.

 

I think I need to go and lie down in a darkened room ???? 

 

[Muhendis]

22 minutes ago, Crossy said:

I think I need to go and lie down in a darkened room

Beer Sir?

[maxpower]

16 hours ago, sometimewoodworker said:

If you take a look at sites that have cataloged 18650 cells it is among the longest shown, so yes at 69.6 it is long

 

 

 

You appear to have forgotten why I questioned your statements and started to drift.

 

Reminder

QUOTE: The size is the same with or without protection.

QUOTE: Your protected cell is not an 18650.

 

Considering your statements above and using the picture below -

 

The 18650 cell in on the right, it is 65mm long

The optional protection circuit is in the center, its about 3mm thick.

The protected cell is on the left and clearly shows how the option has increased package length.

The cell remains 18650 and teams up with a protection board to create a package we call protected 18650.

 

[Crossy]

A few more observations on my solar street lights.

 

One light now has a (measured) 42Ah battery pack (with a protection board this time).

It has become evident that it and the other two (unmodified) lights have about the same (dimmed) brightness at 6AM after a night on "auto".

Turning both "off" and then "on" (not "auto") brought them back to full brightness (as did "auto").

The unmodified light was showing 3 lights on the battery indicator, the modified 4 lights (out of 4).

Evidently the dimming over night is being controlled by the light controller and is not related to the battery voltage.

 

Next test will be to run them overnight set to "on" rather than "auto".

 

[Susco]

I want to buy these thingies, but how do you connect them?

 

My understanding is that they get soldered to the positive and negative of the battery, or maybe the battery holder, but why would the discharge not use the shortest way, instead of passing through the BMS?

 

[impulse]

FWIW, here's a good discussion of the real power available from various brands of 18650 batteries.  In conjunction with bigclivedotcom's YouTubes on 18650 issues and teardowns, they go a long way to 'splaining why the huge capacity 18650's I used to buy in BKK Chinatown cratered way too quickly...

 

 

[Crossy]

5 hours ago, Susco said:

I want to buy these thingies, but how do you connect them?

 

The "tails" or the large rectangular pads at the end of the board (marked B+ & B-) go to the relevant terminal of the battery.

 

The smaller square pads towards the centre of the board (marked P+ & P-) go to your load EDIT and charger.

 

The controlling FET on the other side of the board is between P- and B-.

 

EDIT Here's a better picture showing the connections, battery on the end pads, load on the centre pads.

 

 

[Muhendis]

5 hours ago, impulse said:

FWIW, here's a good discussion of the real power available from various brands of 18650 batteries.  In conjunction with bigclivedotcom's YouTubes on 18650 issues and teardowns, they go a long way to 'splaining why the huge capacity 18650's I used to buy in BKK Chinatown cratered way too quickly...

You beat me to it. I watched this last night. It's incredible what some manufacturers will try to get away with. Claims of over 9,000 mAh in such a small volume are obviously way over the top. If it looks too good to be true............

[Muhendis]

5 hours ago, Susco said:

My understanding is that they get soldered to the positive and negative of the battery, or maybe the battery holder, but why would the discharge not use the shortest way, instead of passing through the BMS?

Batteries of all types will have a shorter life if they are charged and discharged too quickly. There are more stresses involved. By using a BMS for both directions the amount of stress is minimised and the batteries last longer. 

Soldering is not the preferred method of connection. The batteries are spot welded to the interconnecting strips. Once again it is less stressful in terms of the amount of heat against the length of time to make the connection. 

[Crossy]

On 1/2/2021 at 6:30 AM, Crossy said:

Next test will be to run them overnight set to "on" rather than "auto".

 

Soooo.

The unmodified (20Ah) light manages about 8 hours in "on" mode before becoming significantly dimmer. It's still lit after 12 hours but is definitely in glowfly mode.

 

The modified (42Ah) light is still at full brightness after 12 hours in "on" mode.

 

Both lights seem to recover to full charge (by the charge lights) over a decent sunny day.

 

Being a lazy a** (not wanting to manually operate the lights) and having no way to re-program the controllers I'm probably going to un-modify back to 20Ah as it works fine on "auto". The 6Ah cells can be re-purposed.

 

Here endeth the experiment.

 

[Muhendis]

6 hours ago, Susco said:

My understanding is that they get soldered to the positive and negative of the battery, or maybe the battery holder, but why would the discharge not use the shortest way, instead of passing through the BMS?

In addition to my earlier comments (I just checked the specs.) I noticed this:-

Main function: over charging protection, over discharge protection, short circuit protection, over current protection function. So that's a job the BMS does not appear to do now. I do have a concern however that not all cells will charge and discharge at the same rate and eventually there will come a time when one cell is significantly different from the others and will make the whole pack under-perform. Normally a BMS would monitor each cell and balance the whole pack ensuring higher charge rate in some cells which need it and also ensuring that all cells discharge at the same rate. This is essential for higher voltage series connected strings. Parallel connected packs are similarly affected but it would be difficult to know which cell is poorly without monitoring all of them. With parallel packs the good cells would ensure that the poor cell is kept upto date so to speak but the whole pack would still be affected because of this self maintenance effect. Charge from the better cells would be shuttled into the poorer cell.