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

[Muhendis]

38 minutes ago, Susco said:

 

If I attach one of these to a battery, would that result in the solar light switching off when the battery reaches 3v?

Probably because the rather vague specification indicates that discharge is controlled.

[Susco]

6 minutes ago, Crossy said:

 

Do you have two cells in series (2S)?

For some reason the pictures are not showing for me so I can't really comment ????

 

It doesn't say anything about low voltage cut-off.

 

 

 

Sorry, linked to the wrong one. This is the 1 cell version. I assume 1s and 2s stands for the number of cells

 

https://www.lazada.co.th/products/sissi-1s-37v-3a-li-ion-bms-pcmpcm18650-i1866576003-s5757826502.html?spm=a2o4m.searchlist.list.38.16575917KDITKX&search=1

 

• Overcharge detection voltage: 4.25±0.05V
• Overcharge release voltage: 4.23±0.05V
• Overdischarge detection voltage: 2.54 ± 0.1V
• Overcurrent detection current: 1-3A

 

[Muhendis]

3 minutes ago, Muhendis said:

Probably because the rather vague specification indicates that discharge is controlled.

"MOS transistor can control the battery charge and discharge;"

[Crossy]

Looks good to me ???? 

 

Can you find one that ships from inside Thailand?

 

[Muhendis]

8 minutes ago, Susco said:

Sorry, linked to the wrong one. This is the 1 cell version. I assume 1s and 2s stands for the number of cells

Yes. the "S" number refers to the number of cells. Just for clarification the "P" terminals are for load/charger connection and the over discharge will disconnect the battery. It will not necessarily turn off your light. If your charger is running and connected the light will stay on.

[Susco]

2 minutes ago, Muhendis said:

Yes. the "S" number refers to the number of cells. Just for clarification the "P" terminals are for load/charger connection and the over discharge will disconnect the battery. It will not necessarily turn off your light. If your charger is running and connected the light will stay on.

 

The charger will be the solar panel I presume, so at night it will not charge.

 

Is there a way to find out if the light itself has such a protection built in?

 

I have now 15 identical lights, same brand, but for some reason there are 2 versions of PCB inside, and one of them I don't really trust.

 

If someone could advise by looking at the pictures?

 

 

[Susco]

32 minutes ago, Crossy said:

Looks good to me ???? 

 

Can you find one that ships from inside Thailand?

 

 

Nope all from China.

 

Only a 2 cell from Thailand, but different style

 

That shop actually has many versions available, but not as cheap as China

 

https://www.lazada.co.th/products/2-bms-2s-74v-3a-37v-bms-pcm-pcb-battery-protection-board-18650-li-ion-lithium-i613084122-s1159126529.html?

[Crossy]

Would this one do the trick

https://www.lazada.co.th/products/bms-1s-37v-10a-li-ion-i1776690083-s5178600960.html

 

[Susco]

There seem to be a few Thai shops on Lazada, if the search function wasn't such a disaster. Almost as bad as TVF

 

https://www.lazada.co.th/products/18650-37v-1-i309516822-s546658407.html?

[Muhendis]

You could always buy your 18650 cells with built in protection 

https://shopee.co.th/LiitoKala-18650-3400mAh-Button-Top-(Protected)-Rechargeable-Li-ion-Battery-(ราคาต่อ1-ก้อน)-i.216480284.5413875484 

My only hangup about these is that if you have your own external protection circuit then replacement cells can be less expensive from an unrestricted selection of suppliers.

[Susco]

3 minutes ago, Muhendis said:

You could always buy your 18650 cells with built in protection 

https://shopee.co.th/LiitoKala-18650-3400mAh-Button-Top-(Protected)-Rechargeable-Li-ion-Battery-(ราคาต่อ1-ก้อน)-i.216480284.5413875484 

My only hangup about these is that if you have your own external protection circuit then replacement cells can be less expensive from an unrestricted selection of suppliers.

 

Can you see from the pictures I posted if there is a protection built in the light?

 

And can you see if one of both is better quality than the other?

[Crossy]

44 minutes ago, Susco said:

If someone could advise by looking at the pictures?

 

Without knowing what the 8-legged beastie is who knows. What voltage does it discharge your cells to if left on full power?

 

[maxpower]

41 minutes ago, Susco said:

 

If someone could advise by looking at the pictures?

 

 

 

 

The PCB you show is the common Chinese control board with optional movement detection sensor. The battery safety and charge is kept in check by a dedicated charge control chip. The lights features are controlled by a programmable chip.

 

 

When purchasing separate BMS boards consider the following.

 

There are two basic sets of voltages considered when using lithium cells to power products.

1. Safety BMS cut off voltages. Example - 2.5V - 4.3V

2. Control charge and discharge range. Example - 3V - 4.2V

 

In the above example, the BMS over discharge voltage might not the best choice for switching off the load. Lithium batteries have happy working ranges to ensure long life and safe charging.

 

[Susco]

11 minutes ago, maxpower said:

 

The PCB you show is the common Chinese control board with optional movement detection sensor. The battery safety and charge is kept in check by a dedicated charge control chip. The lights features are controlled by a programmable chip.

 

 

When purchasing separate BMS boards consider the following.

 

There are two basic sets of voltages considered when using lithium cells to power products.

1. Safety BMS cut off voltages. Example - 2.5V - 4.3V

2. Control charge and discharge range. Example - 3V - 4.2V

 

In the above example, the BMS over discharge voltage might not the best choice for switching off the load. Lithium batteries have happy working ranges to ensure long life and safe charging.

 

 

Since you seem to be knowledgeable about this particular product.

 

You quoted the top picture in my post, which I suspect is a board of lesser quality than the bottom one.

 

Is that something you can figure from looking at the pictures, or is it something just in my head?

 

EDIT: I think to notice in the bottom picture more capacitors with the number 201 and 202 on them

 

12 minutes ago, Crossy said:

What voltage does it discharge your cells to if left on full power?

 

The last batch I got all had the PCB as in the top picture, which I suspect to be of lesser quality.

 

One of the lights with that PCB had a voltage of 2.2v, but was still "glowing".

[Crossy]

7 minutes ago, Susco said:

One of the lights with that PCB had a voltage of 2.2v, but was still "glowing".

 

If your cells really are Li-ion then I wouldn't want them going below about 2.5V.

[Susco]

4 minutes ago, Crossy said:

 

If your cells really are Li-ion then I wouldn't want them going below about 2.5V.

 

I think they are actually LI-PO, because in the small text on the battery it says 3.7v and they charge to 4.15- 4.20V.

 

My feeling is that the one board has discharge protection built in and the other not, but I'm just guessing of course

[Crossy]

2 minutes ago, Susco said:

I think they are actually LI-PO, because in the small text on the battery it says 3.7v and they charge to 4.15- 4.20V.

 

LiPO would make it even worse then, 3.0V minimum.

[Susco]

5 minutes ago, Crossy said:

 

LiPO would make it even worse then, 3.0V minimum.

 

Found a Thai seller for LifePo BMS

 

https://www.lazada.co.th/products/bms-1s10a32v-1s12a32v-1s25a32v-lifepo4-1s-i1336524013-s4145208530.html?spm=a2o4m.searchlist.list.10.6b0f434cQWANQQ&search=1

[Crossy]

5 minutes ago, Susco said:

Found a Thai seller for LifePo BMS

https://www.lazada.co.th/products/bms-1s10a32v-1s12a32v-1s25a32v-lifepo4-1s-i1336524013-s4145208530.html?spm=a2o4m.searchlist.list.10.6b0f434cQWANQQ&search=1

 

Yeah, I ordered the 12A LiFePO version of that unit this morning.

The Power Idea is quick shipping too and his 32650 cells are genuine (he doesn't have 18650).

 

 

[Susco]

How exactly to determine what battery you have?

 

On the battery is written in small script 3.7V 7.4W, as it is supposed to be a 2000mAh capacity. 3.7V is LI-PO

 

In the spec of the light it says 2000 mAh Li-ION battery, which should be 3.6V

 

I have such a Imax B6 smart charger (genuine) so I can charge the battery as LI-ION or LI-PO.

 

When charging as LI-ION at full charge my multi meter shows 3.99V, when I charge as LI-PO the end result is 4.10 - 4.15V

[Susco]

Found a BMS with these spec

 

Over discharge testing range: 2.50±0.1V
Over discharge recovery voltage: 2.90±0.1V

 

Can someone explain what is over discharge recovery voltage?

[Crossy]

4 hours ago, Susco said:

Found a BMS with these spec

Over discharge testing range: 2.50±0.1V
Over discharge recovery voltage: 2.90±0.1V

Can someone explain what is over discharge recovery voltage?

 

Without knowing exactly which device the little 6-pin chap is (there are many 6-pin 1S BMS devices) I'm thinking that:-

• The "Over discharge testing range" will be the cell voltage at which the BMS prevents further discharge by turning off the FETs (and your load) to avoid damaging the cell.
• The "Over discharge recovery voltage" will be the voltage at which the FETs are turned back on (to allow discharge again) after the cell has charged somewhat.

[Crossy]

9 hours ago, Susco said:

On the battery is written in small script 3.7V 7.4W, as it is supposed to be a 2000mAh capacity. 3.7V is LI-PO

In the spec of the light it says 2000 mAh Li-ION battery, which should be 3.6V

 

I'd believe the battery (if one can believe anything these days) and assume it's LiPO.

What voltage does the cell read after it's been fully charged and rested for a couple of hours?

 

The difference in voltage is probably right on the line of the accuracy of your multimeter on the 10V range anyway.

[Susco]

2 hours ago, Crossy said:

I'd believe the battery (if one can believe anything these days) and assume it's LiPO.

What voltage does the cell read after it's been fully charged and rested for a couple of hours?

 

At 15 hours after the batteries have been charged, the voltage of both has dropped by 0.01V

 

3 hours ago, Crossy said:

The "Over discharge recovery voltage" will be the voltage at which the FETs are turned back on (to allow discharge again) after the cell has charged somewhat.

 

You're right, I should have googled it.

1.Load output recovery voltage

When the battery voltage is too low, the load output of controller will cut off the output to prevent the battery over-discharge.When the battery voltage re-charging again, the voltage recovery to the specified value, the load will restore the output, this voltage is called the load recovery output voltage.

 

In general,between the load recovery output voltage and the low-voltage protection voltage,there is about 1.5V dropout voltage,the proposal is to prevent the fluctuations of battery voltage lead to the load output intermittent.

 

[maxpower]

21 hours ago, Susco said:

You quoted the top picture in my post, which I suspect is a board of lesser quality than the bottom one.

 

Is that something you can figure from looking at the pictures, or is it something just in my head?

 

I have no knowledge of your particular product but I do have experience with the many chips and circuits kicking around the Shenzhen market.

 

Variations of these solar light circuits have used many battery chemistry including NiMH LiPo Li-ion and LiFePO4. The most common being the 18650 Li-ion.

 

A photo of the battery might help reduce some guesswork. There are standard sizes that often identify the chemistry.

 

A 3.7 2Ah LiPo flat battery will normally have built in protection sometime visible sometime hidden in the wrapping.

 

Light design and limited space sometimes dictates the type of battery used but its not always the best choice for capacity.
 

[Susco]

22 minutes ago, maxpower said:

 

I have no knowledge of your particular product but I do have experience with the many chips and circuits kicking around the Shenzhen market.

 

Variations of these solar light circuits have used many battery chemistry including NiMH LiPo Li-ion and LiFePO4. The most common being the 18650 Li-ion.

 

A photo of the battery might help reduce some guesswork. There are standard sizes that often identify the chemistry.

 

A 3.7 2Ah LiPo flat battery will normally have built in protection sometime visible sometime hidden in the wrapping.

 

Light design and limited space sometimes dictates the type of battery used but its not always the best choice for capacity.
 

 

There is no protection that I can perceive. The Length of the batter is 65mm

 

The batteries do discharge below 3V. I had yesterday a light that was very dim after 7 hours, and the battery measured 2.7V

 

[maxpower]

48 minutes ago, Susco said:

 

There is no protection that I can perceive. The Length of the batter is 65mm

 

The batteries do discharge below 3V. I had yesterday a light that was very dim after 7 hours, and the battery measured 2.7V

 

 

 

In many of these circuits, over discharge of the battery is prevented by the shutting down of control processor chip when the supply voltage falls too low. This will result in the LED array mosfet turning off and battery discharge stopped. This method will not allow the battery to discharge to a dangerous point but may not be the optimum value.

 

18650 cells are cheap and readily available. I wouldn't sweat over the discharge level too much
 

[Susco]

Few more questions, if allowed.

 

My lights have a panel rated 5.5V/2.5W and the batteries are 3.7V 2000 mAh

 

So what will be the average power the panel will generate ?

 

Maybe explain how to calculate, so don't need to ask this question again.

 

Thinking about putting larger capacity batteries inside, but if the panel will not be able to charge them most days, it won't make sense of course.

 

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?

[Crossy]

The solar industry want you to calculate energy generated as panel rating * 5 hours = 2.5 * 5 = 12.5 Wh.

 

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.

 

That said, the quoted panel rating can be a little "optimistic".

 

Why not try a bigger cell, they're not expensive and if you get no more life you've lost little?

 

 

 

[sometimewoodworker]

21 hours ago, Susco said:

There is no protection that I can perceive. The Length of the batter is 65mm

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. Price may help as will the cell performance matching the claims printed on the plastic sleeve.