Can someone please help me? I'm looking for a solar panel charge to charge lithium 3.7V battery that works without a battery. I'm using one solar panel 6V, 12V or 24V which charges the battery and also supplies the power to the load. I need to be able to supply the power even though the battery is not connected or broken. How can I do this?
I found LT3652 part but I dont think this can do it. Or this part LTC4015 because it states the instant on when the battery is discharged.
Or could I design a switch that turns on when battery is not present and delivers power to the system? I was thinking to use a step down to 5V which is enabled only when there is no battery.
You mentioned a 3.7V lithium battery - is this the nominal voltage or the full charge voltage (basically, is this a LiFePO4 or Li-Ion/Polymer battery)? If nominal, what is the full charge voltage that you intend? Your answer here will determine what part I recommend for this application.
Also, you mentioned one solar panel but a range of voltages, can you elaborate on that? Will a variety of panels be used with this circuit or will the same panel always be used? And if the same panel, where do those voltages come from and why did you list three? Have you not decided on a panel yet?
Also, what charge current do you need?
The full charge voltage is 4.2V. Nominal is 3.7V. I'm using lipo 606066 3.7V 2400mah Lithium polymer battery.
Yes, it will be a one solar panel but it could be 6V, 12V or 24V but one at the time. I need one design that could work with either of these voltages.
I'm not sure yet what charge current. The battery capacity is 2400mah.
I decided to go for LTC4000-1 IC. Do you think its the right choice? It can take in a wide range of voltages and can supply power when the battery is dead.
I might actually recommend LTC4162-L. It has a dynamic tracking MPPT algorithm that will regulate your solar panel at the max power point at any illumination level. The charge current goes up to 3.2A max, so if that works for you then it may be the best fit.
Sounds like LTC4162-LADM or LTC4162-L42M will be a good fit here. the -LADM one is adjustable and offers a little more control if you have a processor in your system. If you don't, then you might want to consider LTC4162-L41M.
I think you'll find this to be much simpler than LTC4000-1.
If I use LTC4162-L41M then I wouldn't need a processor? Also do I need a DC-DC buck converter for this IC?
It looks simpler but I need to go through the datasheet.
Are there any benefits over LTC4000-1? What about the cost?
Which demo board would be suitable for LTC4162-L41M?
I already ordered a demo board for LTC4000-1.
Firstly, there was a typo in my previous response: I wrote LTC4162-L41M where I should have written LTC4162-L42M. You should not use the -L41M variant; that will charge your battery to 4.1V instead of 4.2V. You don't need a processor for LTC4162-LADM or LTC4162-L42M (or any LTC4162 variant), but you could use one if you wanted.
As for whether you need a DC-DC buck converter, it depends on what you mean. The LTC4162 has an integrated buck charger, so you don't need it for the charging functionality. However, it is not uncommon to follow the LTC4162 circuit with another DC-DC to convert the VIN and battery voltages to the same load voltage, regardless of which source is powering the load.
It is much simpler and there are many benefits over LTC4000-1 including the cost. The MPPT function is also more accurate in general. I recommend you take a look through the datasheet.
That said, the down-side is that the demo board is not released yet, but it should be in 2-3 weeks. In the meantime I could send you some design files to assist you. Otherwise, since you already have the LTC4000-1 demo board, maybe you should just stick with that for now.
LTC4162-L42M seems like a really good IC for my application.
I was asking if i would need a DC-DC converter before the IC like in LTC4000-1 part but it looks like I wouldn't need which is great. Has is got a buck converter built it?
I would use a DC-DC boost converter after the charging circuit because I need to supply 5V to the system.
What happens to the output when I use ,for example, a 12V solar panel? When the battery is connected it should provide 4.2V max if its fully charged. What about when the battery is dead or not connected? What sort of voltage I would expect at the output?
I'm looking to design a PCB very soon and I will test it myself. It would be great if you could provide the design files. I will check if I can simulate this IC using LTSpice as well.
Would you recommend a 4 layer board? Or I could get away just using a 2 layer board?
Is it possible for you to review my design once I finish it?
I've got another question. Will LTC4162 work with a polymer battery? Or should I use LiFePO4?
Thanks and Regards,