Hello,
im playing since a few days with the idea of an Battery Power Supply that can support a possibly wide variety of devices
for me is important that it can provide around 9V for opamp circuits (your usual preamplifier/dacs/line levels i would say) but also 5V is a fairly common voltage, USB for example
Voltages:
So... i compared the voltage ranges (and possibly other pros/cons) and i feel like LTO could be the "perfect" candidate....
(4.4V) 4.6V - 5.2V seems like a perfect 5V USB range
and 9.2 - 10.4 seems like a reasonable 9V replacement
both with the benefit of "pure battery power" ( tho it also seems reasonable to use a low dropout regulator for the 9V range, or diode for a more passive solution)
Batteries:
there are honestly not many solutions LTO wise around.... most attractive size wise are these:
https://hakadibattery.com/products/...y-battery-pack-electric-wheelchair-power-grid
https://hakadibattery.com/products/...w-temperature-battery-cells-25000-cycle-times
as far my search went these two options are pretty much the only cylindrical LTO's
the 18650 have around double ESR and need holders which increases ESR too so i feel like the cap style ones are probably the better option
Design Ideas:
using 4 of the capacitor style hakadi 2500mAh batteries, which can be switched (either by a soldering job or low ESR switching solution) from 2x2 batteries configuration (2 batteries in parrallel and a second double pack in series) or 1x4 series configuration (4 batteries in series)
as these batteries have under 15mOhm ESR the 5V parallel configuration would give around 8mOhm + 8 mOhm, pretty much identical to A123 LiFePo4 batteries, tho im not exactly sure how LiFePo4 compares to LTO directly, i kinda hope for the best here
Charging:
LTO's can be very easly charged via ldo, the cap style ones have a max charge current of 25A and charging with 3A takes around 30-60minutes
preferably i would include a "charge en" input/output, which allows multiple batterie supplys to charge at the same time to optimize "pure power runtime"
since the voltage is either 5 or 10 volt its probably best to use some LDO with a main supply not far from the desired voltage
i saw you can wire something like a LT1083 in constant current mode, but does that mean i need a pregulation LDO for the right voltage max voltage?
Balancing:
preferably simply trough resistors, which power dissapation should i aim for for 3-5A charge current?
Protection:
(optional)
- not really nessecary with LTO but i could include a low ESR mosfet + seperate TLV3702 to disconnect load for overdischarge protection (same mosfet could be used as a load switch for EN input)
im playing since a few days with the idea of an Battery Power Supply that can support a possibly wide variety of devices
for me is important that it can provide around 9V for opamp circuits (your usual preamplifier/dacs/line levels i would say) but also 5V is a fairly common voltage, USB for example
Voltages:
So... i compared the voltage ranges (and possibly other pros/cons) and i feel like LTO could be the "perfect" candidate....
(4.4V) 4.6V - 5.2V seems like a perfect 5V USB range
and 9.2 - 10.4 seems like a reasonable 9V replacement
both with the benefit of "pure battery power" ( tho it also seems reasonable to use a low dropout regulator for the 9V range, or diode for a more passive solution)
Batteries:
there are honestly not many solutions LTO wise around.... most attractive size wise are these:
https://hakadibattery.com/products/...y-battery-pack-electric-wheelchair-power-grid
https://hakadibattery.com/products/...w-temperature-battery-cells-25000-cycle-times
as far my search went these two options are pretty much the only cylindrical LTO's
the 18650 have around double ESR and need holders which increases ESR too so i feel like the cap style ones are probably the better option
Design Ideas:
using 4 of the capacitor style hakadi 2500mAh batteries, which can be switched (either by a soldering job or low ESR switching solution) from 2x2 batteries configuration (2 batteries in parrallel and a second double pack in series) or 1x4 series configuration (4 batteries in series)
as these batteries have under 15mOhm ESR the 5V parallel configuration would give around 8mOhm + 8 mOhm, pretty much identical to A123 LiFePo4 batteries, tho im not exactly sure how LiFePo4 compares to LTO directly, i kinda hope for the best here
Charging:
LTO's can be very easly charged via ldo, the cap style ones have a max charge current of 25A and charging with 3A takes around 30-60minutes
preferably i would include a "charge en" input/output, which allows multiple batterie supplys to charge at the same time to optimize "pure power runtime"
since the voltage is either 5 or 10 volt its probably best to use some LDO with a main supply not far from the desired voltage
i saw you can wire something like a LT1083 in constant current mode, but does that mean i need a pregulation LDO for the right voltage max voltage?
Balancing:
preferably simply trough resistors, which power dissapation should i aim for for 3-5A charge current?
Protection:
- fuse at the output for short circuit/overcurrent protection
- charging could be triggered by TLV3702 UV threshold
(optional)
- not really nessecary with LTO but i could include a low ESR mosfet + seperate TLV3702 to disconnect load for overdischarge protection (same mosfet could be used as a load switch for EN input)
Yup, what the world sorely lacks is a 5V battery power supply with 5V natively, something similar to IanCanada Mini 3.3V/6.6V power supply. I need a couple..three or five.
yup, indeed 🙂 feel free to share any ideas/tips since im still in the planning phase
im thinking about something like this as the pure battery portion, (some opto-isolators are left out triggering the relay, which should be a two trigger magnetic latch-type)
trigger voltages (5.4/5.2V charge end and 4.6/4.8V charge start) can be set via jumpers, its voltage range vs capacity
this design would work for parallel and series configuration (in 10V series mode just half of the bank is voltage checked), im a bit unsure about how unbalanced the batteries can get, it might be worth checken each cell individually for safety? tho since LTO's are the safest around this might be enough?