Hello.
I've finished my first prototype, and some questions have popped up. This is a small smps charger designed for current controlled charging with power factor correction. It checks pack health via middle point balance, thermistors and ah-in - ah-out.
1. As of this moment I get 12 bit resolution on my voltage measurements. This works out to ~25mV resolution on under 100V packs. Lesser for higher voltage packs (bypass jumper allows higher voltages). I could add 16 bit voltage reading, but at higher cost. Worth it, or unnessecary given you don't need high accuracy for bulk charging?
Programming/Interface. Comments on these would be appreciated highly.
2a. LCD/pushbuttons programming and looking at pack state, ahrs consumed, middle point balance and temperatures. This seems to be the hardest way to implement, as i don't have much experience with ldc screens and such.
2b. Interfacing towards android (iPhone functionality will be outsourced probably) via usb cable. All programming and a separate app will be used for programming and showing all parameters. Ease of upgrading. Possible fancy GUI.
2c. Simple interfacing towards pc. Feedback from leds. Press a button, 'it should work' - as you programmed. But it sucks not being able to witness it.
Thermistors.
3. How many? I'd recon you'd like some for your engine aswell - what would you deem appropriate?
Power.
4. Would you like a fuse popping 4kW monster - or a 800W smallish thing. Right now I use a ~40g type 77 ferrite core with homewound windings, being operated at 250 khz - this isn't very efficient - clocking in at around 85% efficiency for 850W out. I could design something awefully powerful - but the cost and weight rises exponentially, things does not get cheaper with more power in smps design.
Enclosure.
5. I had some nice success spreading the heat from the converter throughout my aluminum bike frame. It worked better than expected as a heatsink. I realize most frames aren't aluminium, and I've yet to test it on steel. Would you have a very discrete 'frame cooled' charger, or is a fan (with the additional hole and environmental exposure (and tiny performance boost)) worth it?
I've finished my first prototype, and some questions have popped up. This is a small smps charger designed for current controlled charging with power factor correction. It checks pack health via middle point balance, thermistors and ah-in - ah-out.
1. As of this moment I get 12 bit resolution on my voltage measurements. This works out to ~25mV resolution on under 100V packs. Lesser for higher voltage packs (bypass jumper allows higher voltages). I could add 16 bit voltage reading, but at higher cost. Worth it, or unnessecary given you don't need high accuracy for bulk charging?
Programming/Interface. Comments on these would be appreciated highly.
2a. LCD/pushbuttons programming and looking at pack state, ahrs consumed, middle point balance and temperatures. This seems to be the hardest way to implement, as i don't have much experience with ldc screens and such.
2b. Interfacing towards android (iPhone functionality will be outsourced probably) via usb cable. All programming and a separate app will be used for programming and showing all parameters. Ease of upgrading. Possible fancy GUI.
2c. Simple interfacing towards pc. Feedback from leds. Press a button, 'it should work' - as you programmed. But it sucks not being able to witness it.
Thermistors.
3. How many? I'd recon you'd like some for your engine aswell - what would you deem appropriate?
Power.
4. Would you like a fuse popping 4kW monster - or a 800W smallish thing. Right now I use a ~40g type 77 ferrite core with homewound windings, being operated at 250 khz - this isn't very efficient - clocking in at around 85% efficiency for 850W out. I could design something awefully powerful - but the cost and weight rises exponentially, things does not get cheaper with more power in smps design.
Enclosure.
5. I had some nice success spreading the heat from the converter throughout my aluminum bike frame. It worked better than expected as a heatsink. I realize most frames aren't aluminium, and I've yet to test it on steel. Would you have a very discrete 'frame cooled' charger, or is a fan (with the additional hole and environmental exposure (and tiny performance boost)) worth it?