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Old 03-09-2021, 03:36 AM   #1
EasyGoing1
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Default Swapping out a NiMh for a LiPo?

I bought these emergency lights that turn on when the power goes out. They are connected to 120VAC 24/7, keeping a battery charged which then kicks in when power goes out. They have inside of them a NiMh 1000 mah battery. I can't figure out how this circuit is charging the battery and I would like to swap it out with a 3000mah LiPo but I'm concerned that this circuit might damage the LiPo.

Are my concerns valid? ... Other thoughts?

Here is the circuit:






Also, what do you think about this concept as one way to use the LiPo without the lights’ charger circuit being able to affect the LiPo?

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Old 03-09-2021, 05:04 AM   #2
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Default Re: Swapping out a NiMh for a LiPo?

that board is for lion, not lipo - i think the charge voltage is different.
either way, it wont work.
you need to design it from scratch.
draw a schematic of the original board, keep the dc part and scrap the trickle-charge part.
what is the original battery voltage?
and how much current does the thing use when on? because if it's the type with a pair of car foglamps then you arent running it through that battery protection chip.
the protection will need to handle the current and then some overhead for inrush.
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Old 03-09-2021, 07:33 AM   #3
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Default Re: Swapping out a NiMh for a LiPo?

Quote:
Originally Posted by EasyGoing1 View Post
I bought these emergency lights that turn on when the power goes out. They are connected to 120VAC 24/7, keeping a battery charged which then kicks in when power goes out. They have inside of them a NiMh 1000 mah battery. I can't figure out how this circuit is charging the battery and I would like to swap it out with a 3000mah LiPo but I'm concerned that this circuit might damage the LiPo.

Are my concerns valid? ... Other thoughts?

Here is the circuit:

Also, what do you think about this concept as one way to use the LiPo without the lights’ charger circuit being able to affect the LiPo?
What is the voltage going to the battery pack with out the battery pack hooked up very important to know this will answer a lot of theses questions that you have

This depends on the voltage of the battery that in this emergency light if it a standard lim-ion battery voltage 3.2 / 6.4 / 9.6 / 12.8 volts

If it falls in one of these standard voltage
4.2 / 8.4 / 12.6 volts

Then maybe if you have the right protection board if it not then you would have to make your own board

Quote:
Originally Posted by stj View Post
”that board is for lion, not lipo - i think the charge voltage is different.
either way, it wont work.
you need to design it from scratch.
draw a schematic of the original board,

keep the dc part and scrap the trickle-charge part.” * might want to keep this depending on what the amperage is

“what is the original battery voltage?” Need to know
“and how much current does the thing use when on?” Need to know

“because if it's the type with a pair of car foglamps then you arent running it through that battery protection chip the protection board will need to handle the current and then some overhead for inrush.”

You would have to get the right protection board for the current you would need for the light bulbs on this setup
I would have agree you for the most part the part that have this next to the item “*” I have a slightly different take on what might work

But if they are using LED lights it might work depending on what voltage is needed for them to work correctly

Now if it is incandescent light bulb then yes but still might work depending on what voltage is needed but you have some leeway on this setup

Show a picture of the battery pack so I can get an idea what was inside of it

I have work on this type of lighting before but I do not recognize this type of setup until I see the battery
pack

By the way you have the battery charger board hooked up backwards this will not work the emergency board is your power source and the battery is hooked like normal in fact if you power it this way you might fry the battery protection board and hopefully nothing else

I hope this helps
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Old 03-09-2021, 12:32 PM   #4
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Default Re: Swapping out a NiMh for a LiPo?

Quote:
Originally Posted by stj View Post
that board is for lion, not lipo - i think the charge voltage is different.
either way, it wont work.
you need to design it from scratch.
draw a schematic of the original board, keep the dc part and scrap the trickle-charge part.
what is the original battery voltage?
and how much current does the thing use when on? because if it's the type with a pair of car foglamps then you aren't running it through that battery protection chip.
the protection will need to handle the current and then some overhead for inrush.
Battery voltage that came with the unit is 3.6V (reminds me of the battery packs they put into standard landline cordless phone hand sets). The LiPo pack that I want to use is 3.7.

The lights are an LED array on each side. They say it will run for 4 hours on a fully charged battery, but those NiMh batteries don't do well when their charge is never cycled so I would expect it wouldn't take too long before 4 hours turns into an hour. LiPo's are far more resilient and tripling the mah would certainly give the thing a longer run time and it would last a lot longer.

I was actually a little concerned that you would tell me to trace out that circuit board and draw up the schematic. That's not a task I particularly enjoy doing.

Is there no way to McGuiver what I want to do? And I know that the charger I put in the photo is a LiIon charger but I've used it on those LiPo packs before and it seems to work. Though admittedly I haven't use them for extended periods of time. And maybe a similar board exists that is actually designed for LiPo batteries...


What I REALLY wanna know is ... assuming I have a LiPo charger ... would my idea of connecting it with the diode the way I have it actually work? .... theoretically ....

Here is the link to the actual lights that I bought.
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Old 03-09-2021, 12:36 PM   #5
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Default Re: Swapping out a NiMh for a LiPo?

Quote:
Originally Posted by EasyGoing1 View Post
Battery voltage that came with the unit is 3.6V (reminds me of the battery packs they put into standard landline cordless phone hand sets). The LiPo pack that I want to use is 3.7.

The lights are an LED array on each side. They say it will run for 4 hours on a fully charged battery, but those NiMh batteries don't do well when their charge is never cycled so I would expect it wouldn't take too long before 4 hours turns into an hour. LiPo's are far more resilient and tripling the mah would certainly give the thing a longer run time and it would last a lot longer.

I was actually a little concerned that you would tell me to trace out that circuit board and draw up the schematic. That's not a task I particularly enjoy doing.



Is there no way to McGuiver what I want to do? And I know that the charger I put in the photo is a LiIon charger but I've used it on those LiPo packs before and it seems to work. Though admittedly I haven't use them for extended periods of time. And maybe a similar board exists that is actually designed for LiPo batteries...


What I REALLY wanna know is ... assuming I have a LiPo charger ... would my idea of connecting it with the diode the way I have it actually work? .... theoretically ....

Here is the link to the actual lights that I bought.
You can do it but you would have to get the right battery protection board for 3.2 volt battery lim-ion battery not the ones 4.2 volts ones that you want to use


Some like this this brand I have used before and they work very well

https://www.ebay.com/itm/2x-Batterie...cAAOSw1CxamENM

I have even used , used ones with out any issues
Be careful when buying non brand name batteries because the amp hour rating are exaggerated lot in some cases because I once bought a case of this type of battery and the battery amp hours rating was 1/3 of what was stated not they did not work but not as long as they claimed

So if you get non brand name batteries get them as cheap as possible

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Old 03-09-2021, 01:21 PM   #6
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Default Re: Swapping out a NiMh for a LiPo?

Quote:
Originally Posted by sam_sam_sam View Post
What is the voltage going to the battery pack with out the battery pack hooked up very important to know this will answer a lot of theses questions that you have
Stock battery pack is 3.6 volts. LiPo that I wanna use is 3.7 volts.

Quote:
Originally Posted by sam_sam_sam View Post
Then maybe if you have the right protection board if it not then you would have to make your own board

<snip>

Show a picture of the battery pack so I can get an idea what was inside of it


Here is the link to the actual item that I purchased

Quote:
Originally Posted by sam_sam_sam View Post
I have work on this type of lighting before but I do not recognize this type of setup until I see the battery
pack

By the way you have the battery charger board hooked up backwards this will not work the emergency board is your power source and the battery is hooked like normal in fact if you power it this way you might fry the battery protection board and hopefully nothing else

I hope this helps
My intention was to use the diode to protect the battery charge circuit board.
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Old 03-09-2021, 01:50 PM   #7
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Default Re: Swapping out a NiMh for a LiPo?

Quote:
Originally Posted by sam_sam_sam View Post
You can do it but you would have to get the right battery protection board for 3.2 volt battery lim-ion battery not the ones 4.2 volts ones that you want to use


Some like this this brand I have used before and they work very well

https://www.ebay.com/itm/2x-Batterie...cAAOSw1CxamENM

I have even used , used ones with out any issues
Be careful when buying non brand name batteries because the amp hour rating are exaggerated lot in some cases because I once bought a case of this type of battery and the battery amp hours rating was 1/3 of what was stated not they did not work but not as long as they claimed

So if you get non brand name batteries get them as cheap as possible
I vape, and I have a dozen 18650's laying around. I made the mistake of buying a pair of Sony-branded 18650s that had a part number that was recommended on a vape site as being a solid battery for vaping ... we aim for batteries that can sustain short bursts of high current draw preferably with enough capacity to last a day without needing to be recharged.

What I received were batteries that looked exactly like what I saw in the picture... however, they performed worse than the batteries I was intending to replace. They didn't hit hard enough and they died WAY too quickly...

How do you check the actual capacity of these LiIons? I was going to build an Arduino project to do that, but for some reason, I can't seem to find a current sensor module that's worth a shit. They never seem to show current values that are remotely honest ... and what I mean by that is - for example, when I use a current sensor module like an INA219 and I connect a AA battery fully charged to a resistor through the current sensor ... what the Arduino gets over the i2C port are current readings that constantly fluctuate ... and I'm not talking like between 75 milliamps and 78 milliamps ... I'm talking about CONSTANT fluctuations from like 25ma to 500ma with it changing dozens of times in a second. Which seems completely unlikely to me given a AA battery and a resistor. Those values would be useless when trying to calculate the MAH of a battery.

What do you use to figure out where your batteries are at. That information is valuable in vaping.

I'm not opposed to your idea by the way. These 18xxx LiIons certainly have the capacity to keep some LEds running for a long time, and I already have the charging circuit for them... so what you're saying is that the way I drew it, it would work ... assuming I use that charge circuit with a couple of 18650's connected in parallel? That diode will keep the lights charger from feeding voltage to my charger?
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Old 03-09-2021, 03:15 PM   #8
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Default Re: Swapping out a NiMh for a LiPo?

Quote:
Originally Posted by EasyGoing1 View Post
I'm not opposed to your idea by the way. These 18xxx LiIons certainly have the capacity to keep some LEds running for a long time, and I already have the charging circuit for them... so what you're saying is that the way I drew it, it would work ... assuming I use that charge circuit with a couple of 18650's connected in parallel? That diode will keep the lights charger from feeding voltage to my charger?
One note the way you drew it , it is not correct it needs to be on the input side of the board you have a board that is only a charging board and do make them as well but you can not use the wrong board for this because you are going to do one thing either you are frying the charging board or you are going to short out the battery and neither one would be good

I would highly recommend that you get the correct board for how you want to use this setup

The problem you are going to have if use the emergency light charging circuit it will not charge the 18650 batteries fully you would probably only have about 1/4 to 1/2 way charged which would not what you would want

( because your output voltage is not high enough it needs to be 4.2 volts not 3.6 volts )

you unless you some kind of booster circuit that other wise you are going to have to use the batteries I showed you earlier

You would not be able use the protection board you have because it does not have a separate load and charge circuit they do make them but you have to look for them unless you do away with the charging circuit from the emergency light charging board like STJ comments earlier in one of his post and I also made some comments as well

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Old 03-11-2021, 10:50 PM   #9
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Default Re: Swapping out a NiMh for a LiPo?

Quote:
Originally Posted by sam_sam_sam View Post
One note the way you drew it , it is not correct it needs to be on the input side of the board you have a board that is only a charging board and do make them as well but you can not use the wrong board for this because you are going to do one thing either you are frying the charging board or you are going to short out the battery and neither one would be good

I would highly recommend that you get the correct board for how you want to use this setup

The problem you are going to have if use the emergency light charging circuit it will not charge the 18650 batteries fully you would probably only have about 1/4 to 1/2 way charged which would not what you would want

( because your output voltage is not high enough it needs to be 4.2 volts not 3.6 volts )

you unless you some kind of booster circuit that other wise you are going to have to use the batteries I showed you earlier

You would not be able use the protection board you have because it does not have a separate load and charge circuit they do make them but you have to look for them unless you do away with the charging circuit from the emergency light charging board like STJ comments earlier in one of his post and I also made some comments as well
Actually, the way those boards work ... what they were designed to do, is they allow you to connect a circuit that requires 4.2 volts to the output of the board and you can run that circuit on the battery that is attached or if that battery needs to be charged and you apply 5 volts to the other side of the board (where the USB charge port is) then whatever is attached to the output of the board will run even while the battery is being charged.

So basically, with it connected the way it is in the drawing, the idea is to give the light circuit 3.6 volts - but without that circuit being able to apply a charge current back to the battery source, which is the charge board output.
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Old 03-12-2021, 12:29 AM   #10
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Default Re: Swapping out a NiMh for a LiPo?

It might work that way
but it would not work if you use the power supply from the emergency light charging controller part and also provide power to 18650 charging board as well this setup probably would end up damaging something but I am not sure what

I would be careful testing this setup but I would interested if this setup would actually work correctly or not please use a incandescent light bulb like a MR16 20 watt in series with the battery hook up just to be safe because if the light bulb is very bright you might have some issue that need to be investigated to make sure it not a dangerous situation now if it only dim you would be alright but I would monitor it for a while with a meter in the current mode and see if after a while the current drops down to zero milliamperes if not you might have an issue

The reason I am pointing these things is because I have work with this type battery for a very long time and I have done some not very safe things with them in the past with protection boards but I am very aware what can go very very wrong and are prepared for this just in things go very wrong

I once had a battery protection board that did not work correctly and would not turn off the charging current completely OFF but had the current turn down to 100 milliamperes from the bench power supply and was watching but not real closely and when I came back the battery was starting to get warmer and the voltage was hanging around 4.2 at 100 milliamperes so I new something was wrong and sure enough the cutoff voltage was more like 4.6 volt this was not good at all I parted this protection board out

Now if you can tap into the secondary side of the transformer and get 5 volts regulated and disable the charging output voltage you might have a better solution to charge this type of battery with your charging controller board for the 18650 battery just something to think about but be careful not to disable the circuit that turn off the light when you have power hook to emergency light power supply

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Old 03-12-2021, 09:13 PM   #11
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Default Re: Swapping out a NiMh for a LiPo?

......throwing a monkey wrench into your plans. The battery pack isn't NiMh, it's a 3.6V 1000mAh Ni-Cd.

The battery type is on the battery pack pic you took and it's in the product description where you linked.
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Old 03-14-2021, 10:07 PM   #12
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Default Re: Swapping out a NiMh for a LiPo?

NiCd can deal with trickle charging better then NiMH so you may not need to modify it at all.
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Old 03-15-2021, 07:54 PM   #13
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Default Re: Swapping out a NiMh for a LiPo?

- Agent24 - While the NiCd may handle trickle charging better than NiMH, they do need to be deep-cycled on occasion or they develop memory issues.
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Old 03-16-2021, 12:21 AM   #14
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Default Re: Swapping out a NiMh for a LiPo?

Uh...a bit of confusion here.
The original battery is NiCd. Apparently OP wants to swap for Li-Ion.
Likely the current charger trickle charges already which is a no-no for Li-Ion.

Still the same outcome - likely a re-design is needed.
If your li-ion battery pack has overcharge protection, it likely will work just fine in its place but likely you'll find its cycle life severely degraded or possibly destroyed. Something that will limit charge voltage to shunt off the trickle charge, whether it be another auxiliary protection circuit or redesign will be needed.
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Old 03-16-2021, 06:07 AM   #15
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Default Re: Swapping out a NiMh for a LiPo?

Quote:
Originally Posted by delaware74b View Post
- Agent24 - While the NiCd may handle trickle charging better than NiMH, they do need to be deep-cycled on occasion or they develop memory issues.
This is exactly why I wanted to replace it with either LiPo or Lion
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Old 03-16-2021, 10:05 AM   #16
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Default Re: Swapping out a NiMh for a LiPo?

So does your 'new' lithium pack have protection circuitry?
It's probably more work to incorporate a built-for-Li-ion charging circuit into an existing design that's tightly coupled with other circuitry.

If you don't have protection circuitry on the Li-ion then get protection circuitry. And if you can tweak the protection circuitry to stop charging at 4.2 volts (or less), all the better. Other than being a bit inefficient when the cell is fully charged, it should work just fine.
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Old 03-24-2021, 08:46 PM   #17
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Default Re: Swapping out a NiMh for a LiPo?

Quote:
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So does your 'new' lithium pack have protection circuitry?
It's probably more work to incorporate a built-for-Li-ion charging circuit into an existing design that's tightly coupled with other circuitry.
So this is where I struggle - though I wholeheartedly agree with this statement, this particular circuit is about as stupid simple as it gets ... we have:

1) A circuit that connects to standard home AC electricity.
2) The circuit converts AC to DC (though it's still kinda noisy, I checked).
3) The circuit has two primary functions:
a) Keep the battery charged while its AC source is hot.
b) When the AC source goes cold, switch on the LED lights and power them from the battery.

I mean ... THAT'S ALL IT DOES... and all I wanna do is replace said battery with batteries that are better suited to constantly being charged without developing memory, and would also provide a longer run time for the lights when the power goes out. Without question, the NiMh battery pack MIGHT provide the 2 hours of run time they claim TODAY ... but next year? That number will be noticeably smaller and it will continue to get smaller the more it develops a memory.

SO, All I wanna do is replace that battery pack with better batteries, but the problem being, that the connection where the battery connects to the circuit, will be trying to charge the batteries all the time ... and I was hoping that a simple diode properly placed, would block that charge current from getting to the batteries, while I then provide my own method of charging the batteries.

But so far, No one has told me if my diode theory for blocking charge current would actually work. I suppose I could just test it ... what's the worse that could happen?

Quote:
Originally Posted by eccerr0r View Post
If you don't have protection circuitry on the Li-ion then get protection circuitry. And if you can tweak the protection circuitry to stop charging at 4.2 volts (or less), all the better. Other than being a bit inefficient when the cell is fully charged, it should work just fine.
These little gizmo's should do the job...
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Old 03-24-2021, 09:53 PM   #18
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Default Re: Swapping out a NiMh for a LiPo?

Quote:
Originally Posted by eccerr0r View Post
If you don't have protection circuitry on the Li-ion then get protection circuitry. And if you can tweak the protection circuitry to stop charging at 4.2 volts (or less), all the better. Other than being a bit inefficient when the cell is fully charged, it should work just fine.
OK, check out this diagram on that charging board I referred to:



Notice that the battery is protected from whatever it's powering by the charge circuit being in the middle...

So what I was thinking of doing was something like this:



So that the charger circuit basically becomes the battery that is connected to the emergency light, with the diode preventing any charge current from being back-fed into the output of the charger ... but that charger is designed to monitor the battery at all times and prevent it from being over-discharged (by cutting power to whatever the charger is powering and then continuing to charge the battery) and it prevents the battery from being overcharged because it actually does the charging...

That circuit by the way ... is meant to be used as a portable power source for whatever ... and when you have 5 volts connected to it, then it won't even let the battery supply the power to the outputs ... it feeds the output directly from its 5 volt / USB input until the input power is cut then it lets the battery take over supplying voltage to the outputs.

It's a pretty cool circuit.

THE ADDED BENEFIT that I am figuring on getting from having the diode inline, is losing .7 volts across the diode ... since the original battery is 3.7 volts and the LiIon is 4.2 volts, having the diode in place brings the voltage at the emergency light back to 3.5 which is a little lower than the original battery but it certainly won't damage anything.
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Old 03-25-2021, 05:16 AM   #19
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Default Re: Swapping out a NiMh for a LiPo?

so if you do that,
2 things to watch.

1: keep the usb socket isolated from any metal casing - or your ground will bypass the battery protection.
2: dont overload the battery protection circuit with your load.
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Old 03-25-2021, 01:26 PM   #20
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Default Re: Swapping out a NiMh for a LiPo?

Quote:
Originally Posted by EasyGoing1 View Post
... Other thoughts?
Are you continuing using them as emergency fixtures? If yes, I wouldn't bother changing battery technology. In my experience, NiCd does not have a lower life span than other, "newer" type batteries in this application. From my observations, NiCd might be somewhat better in this application.

Remember, emergency fixtures should be regularly run down to their hourly rated running time to test the battery capacity.
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