Adding Constant Current CC Feature to power supply.

[Dinesh6252]

Hi,

LM317 very common TO220 1.5 amps. Small package TO92 100ma.
Should be ok for normal room temperatures or temperature as adjusted.

78xx series not good, like 7805. Too much variation in output voltage.

I have LM317 and Lm339N both available with me.

Edit: 78L05 also available.

[MrAl]

Hi,

LM317 very common TO220 1.5 amps. Small package TO92 100ma.
Should be ok for normal room temperatures or temperature as adjusted.

78xx series not good, like 7805. Too much variation in output voltage.

I have LM317 and Lm339N both available with me.

Edit: 78L05 also available.

Hello,

Ok great.  Do you have the LM317L (TO92 package) or just the LM317 (TO220 package) ?
The LM317L is smaller that's all.

The 78L05 or any of those regulators like 7805, 7806, 7812, etc., are not good enough for this.

It will take a little time to draw up the schematic but shouldnt take more than a day.
Here is a rough idea of what it will look like but not the grayed out parts...

[Dinesh6252]

Hi,

LM317 very common TO220 1.5 amps. Small package TO92 100ma.
Should be ok for normal room temperatures or temperature as adjusted.

78xx series not good, like 7805. Too much variation in output voltage.

Would you be able to demonstrate a working circuit using these components?

Do you have the LM317L (TO92 package) or just the LM317 (TO220 package) ?

Edit: Missed that, I have TO220 package of LM317. Also, attaching the comparator IC picture since I don't know its package name. Thanks

[MrAl]

Hi,

LM317 very common TO220 1.5 amps. Small package TO92 100ma.
Should be ok for normal room temperatures or temperature as adjusted.

78xx series not good, like 7805. Too much variation in output voltage.

Would you be able to demonstrate a working circuit using these components?

Do you have the LM317L (TO92 package) or just the LM317 (TO220 package) ?

Edit: Missed that, I have TO220 package of LM317. Also, attaching the comparator IC picture since I don't know its package name. Thanks [ Attachment Invalid Or Does Not Exist ] [ Attachment Invalid Or Does Not Exist ]

Hi,

Ok TO220 package will have to do then.

That IC looks like an LM339 yes.

What do you mean 'demonstrate" i cant build the circuit although i may be able to provide a simulation.

[Dinesh6252]

What do you mean 'demonstrate" i cant build the circuit although i may be able to provide a simulation.

I meant to say if you can provide a working circuit diagram like before you had provided.

[MrAl]

What do you mean 'demonstrate" i cant build the circuit although i may be able to provide a simulation.

I meant to say if you can provide a working circuit diagram like before you had provided.

Ok here is a preliminary schematic.
It's getting a little complicated now sure if you really want to build this.
This schematic has to be changed to provide foldback current control because it has to sense the voltage at the output and not at the input as the schematic shows.  That means it will get more complicated.
Are you sure you want to build this thing?
Take a look...
You can see the current limit we did and the two original divider resistors near the right side before the load.

[Dinesh6252]

What do you mean 'demonstrate" i cant build the circuit although i may be able to provide a simulation.

I meant to say if you can provide a working circuit diagram like before you had provided.

Ok here is a preliminary schematic.
It's getting a little complicated now sure if you really want to build this.
This schematic has to be changed to provide foldback current control because it has to sense the voltage at the output and not at the input as the schematic shows.  That means it will get more complicated.
Are you sure you want to build this thing?
Take a look...
You can see the current limit we did and the two original divider resistors near the right side before the load.

I think,  i will pass on this idea and will be happy with the 1A output only, thanks for the effort though.

[MrAl]

What do you mean 'demonstrate" i cant build the circuit although i may be able to provide a simulation.

I meant to say if you can provide a working circuit diagram like before you had provided.

Ok here is a preliminary schematic.
It's getting a little complicated now sure if you really want to build this.
This schematic has to be changed to provide foldback current control because it has to sense the voltage at the output and not at the input as the schematic shows.  That means it will get more complicated.
Are you sure you want to build this thing?
Take a look...
You can see the current limit we did and the two original divider resistors near the right side before the load.

I think,  i will pass on this idea and will be happy with the 1A output only, thanks for the effort though.

Ok no problem, and if you want to build the circuit as is you can do that to get some protection.  The reason why i didnt think it was good enough like that was because of the voltage drops AFTER the divider for the LM339.  A perfect circuit would measure the actual output. But as is it will provide for an extreme over voltage like within 1/2 volt maybe or maybe better like 0.25 volts.  Maybe that's good enough though for a multi cell pack with several cells in series.  Each cell top voltage is allowed a 1 percent tolerance in voltage, so for 4 cells in series as long as the cells were balanced the tolerance would go up to 4 percent.

[Dinesh6252]

I am thinking of limiting the Charging voltage to 28V for the battery pack. That way each cell would stay charged at 4.0V always.

[MrAl]

I am thinking of limiting the Charging voltage to 28V for the battery pack. That way each cell would stay charged at 4.0V always.

Good idea. Cell last longer too then.

[--Oz--]

Also take a look at the LM1085, its sorta like the lm317 but a LDO version and 3A capable.

Another easy way, but probably not in the spirit of diy, just buy a dcdc that has current limit.
For $6 these are pretty good, add a $2 V/I meter if you like.
https://www.aliexpress.com/item/2255799836335314.html?spm=a2g0o.productlist.0.0.4543505cybeDnF&algo_pvid=8591200a-7c7d-49e6-bf7f-8a56b75dd8e6&algo_exp_id=8591200a-7c7d-49e6-bf7f-8a56b75dd8e6-11&pdp_ext_f=%7B%22sku_id%22%3A%2210000000051585837%22%7D&pdp_npi=2%40dis%21USD%214.8%213.84%21%21%21%21%21%402103250d16620983018312388e23aa%2110000000051585837%21sea&curPageLogUid=ININLa23rKSe

[--Oz--]

The best "dirt cheap" is a simple current limiting resistor.
With a BMS on the battery, never use higher charge current than the BMS can balance (remember the hoverboard fires).

Charging to 4.20V gives 100% capacity, to 4.10V gives ~89%, and will almost double your life cycles (never leave your battery fully charged), for max life cycles, dont discharge below 35%.

On my LiPo's I am getting over 2000 cycles doing this in a high preformance 230mm quad, using 4s-1300 lipo and peaks at 120A (1800W) and flight times are 90 sec, pretty hard on the battery.

I still like the $6 dcdc solution I posted above (yea not dirt cheap), easily settable (I use external pots mounted on the front panel).
I use a server psu (850W 12v 70A, $17 pre-covid), a couple of these 300W dcdc buck converters and a couple V/I meters for a low cost triple output power supply.

[MrAl]

The best "dirt cheap" is a simple current limiting resistor.
With a BMS on the battery, never use higher charge current than the BMS can balance (remember the hoverboard fires).

Charging to 4.20V gives 100% capacity, to 4.10V gives ~89%, and will almost double your life cycles (never leave your battery fully charged), for max life cycles, dont discharge below 35%.

On my LiPo's I am getting over 2000 cycles doing this in a high preformance 230mm quad, using 4s-1300 lipo and peaks at 120A (1800W) and flight times are 90 sec, pretty hard on the battery.

I still like the $6 dcdc solution I posted above (yea not dirt cheap), easily settable (I use external pots mounted on the front panel).
I use a server psu (850W 12v 70A, $17 pre-covid), a couple of these 300W dcdc buck converters and a couple V/I meters for a low cost triple output power supply.

Hi,

Yes there are a lot of the small converter boards available but i am not sure what he can actually get because of his locations.  India has some very sever restrictions on purchases outside of the country.