Soekris Dam Dac

[jkeny]

if i remember right it uses mosfets and ref voltage and a single ps
kinda charges like a voltage divider would

Any, circuit diagram?

It's OK, I got it

https://hackaday.io/project/9072-open-a ... harger-pcb

[nige2000]

must be on my other computer, think it was slightly different to that hackaday circuit though

[randytsuch]

John
Yeah, that hackaday was where I copied the circuit from

Here is my ltspice circuit I used for the sim.

Basically you stack the regs on top of each other, so you don't need separate ps taps like Nige did for his amp.
Adjust R1 for current you need, and maybe change Q3 and Q4 to larger devices.

[frd1996]

The charts here:

https://hackaday.io/project/9072-open-a ... simulation

indicate charging current of 100mA.

Below he mentions charging current of 1A. If you plan bypass the cell and maintain the 1A current I say you definitely need a bigger transistor and some heat sinking.

[randytsuch]

The design as shown was made for 200ma.

Should be enough for any dac. The transistors I used are rated for 500ma if I remember correctly, and the power supply that provided the raw power was probably less than that, so for my purposes 200ma was fine.

Maybe if you were powering an amp you would need more current, but for my purposes this is fine.
And since I have the batteries, they take care of any instantaneous demands over 200ma. As long as the average current draw for whatever you are powering is less than 200ma, this should work fine.

Note that his R1 is a smaller value than what I used. This resistor sets the current limit for the circuit.


Randy

[jkeny]

Thanks Randy - I presume you still need a relay/switch between each battery & it's charger to isolate it or is there very little current leakage draining the batteries?

[randytsuch]

I put a switch in, otherwise the batteries will drain.

[jkeny]

For single LiFePo4 battery you can use charger boards based on TP5000 IC - very low back leakage & no need for switch or relay to isolate battery
Indicator Led to show CC/CV charging & fully charged - 2 Amp CC when used with small heatsink, otherwise 1-1.5Amp & 3.6V max voltage

Using some additional circuitry, chargers could be connected to multiple batteries in series
Search for them on ebay - about $2 from China

[nige2000]

For single LiFePo4 battery you can use charger boards based on TP5000 IC - very low back leakage & no need for switch or relay to isolate battery
Indicator Led to show CC/CV charging & fully charged - 2 Amp CC when used with small heatsink, otherwise 1-1.5Amp & 3.6V max voltage

Using some additional circuitry, chargers could be connected to multiple batteries in series
Search for them on ebay - about $2 from China

is that something that needs multiple ps windings for multiple cells in series to provide isolation between each charger circuit supply?

[jkeny]

For single LiFePo4 battery you can use charger boards based on TP5000 IC - very low back leakage & no need for switch or relay to isolate battery
Indicator Led to show CC/CV charging & fully charged - 2 Amp CC when used with small heatsink, otherwise 1-1.5Amp & 3.6V max voltage

Using some additional circuitry, chargers could be connected to multiple batteries in series
Search for them on ebay - about $2 from China

is that something that needs multiple ps windings for multiple cells in series to provide isolation between each charger circuit supply?

Using these TP5000 a simple configuration like this could work (it's limited by the 10V max input voltage of the TP5000 stated in the datasheet although board sellers recommend 9V max) which effectively limits it to 3 batteries - maybe only 2?
These turn off when battery charge reaches 3.6V & if not powered the leakage from battery to TP5000 is very very small - so no worries about discharging battery - no need for relay or switches to isolate battery

multi-battery charging.jpg (19.22 KiB) Viewed 1275 times

These would also work & they have a 36V input max so good for 10 batteries - LTM8052 but they would need a relay or switch between each charger & battery to prevent back leakage

multi-battery charging 2.jpg (76.74 KiB) Viewed 1275 times

Sorry, that only does 2.5V output - what is needed for one of these voltage regulators is one that can source & sink current - a 2-quadrant regulator