We support charging temperatures from 0-40 degrees, and it is possible that ambient temperatures near the minimum or maximum will affect the S50 charging situation.

You guys do know that people mostly use their Seestar units in the winter don't you? Shooting at temps below 0C is quite common.

Maybe turning on the dew heater would help keep itself warm enough to charge (at the cost of higher drain from the battery bank).

Daemon42 You can charge the device indoors in a warm environment or near a heat source (but not too close)

Support@Seestar With really long sessions (especially required with mosaics) it is often necessary to charge while imaging.

Daemon42 I think you could use heating tape.

The fact that the Seestar's internal battery cannot be charged below 0 deg C is not something ZWO can avoid. It is simply the physics of lithium ion batteries which dictates this low temp charging (and the high temp charging) cut off spec limits. If you look around you will find that every 12V LiFePO4 battery, every lithium Portable Power Station (whether it uses LiNiMnCoO2 or LiFePO4 cells) and every lithium power bank has the same 0 deg C low temperature cutoff spec. When a lithium ion battery is charging, Li+ ions move from the cathode across the electrolyte and through the separator to the carbon anode. There they must diffuse between the graphite planes and tuck themselves into bonds with the surrounding carbon atoms. That process, called intercalation, requires thermal energy which goes as ~ Exp (-a/kT) where T is the temperature. So the diffusion rate drops exponentially as the temperature drops. What happens then? Li+ ions begin to pile up at the base of the anode where they plate out as lithium metal, forever lost to future discharging processes resulting in lost battery capacity. Do this enough times and the lithium metal can form dendrites which punch through the separator to the cathode shorting out the battery and potentially causing a fire. This is why ZWO has wisely included a low temp sensor to let the internal BMS know when to cut off the charging process. Most lithium batteries do not have this feature, although you can usually find a slightly higher priced model that does.

cengell Hi, I know what you want to do, but you don't need to go through so much trouble. Here are two ways to help you:

1. you can buy a rechargeable charger which can supply power directly
2. you can buy yourself a 65 watt fast charger and type-C direct connection charging port for faster charging.

Support@Seestar Powering the Seestar at temps below 0C is a very important topic as there are lots of posts on line asking about how to get around this. Maybe you can help shed some additional light on the power circuitry by answering a few questions.

1 If we remove the battery pack in the bottom compartment and attach an external power supply to the Seestar through the USB port on its side, will everything still work as it should? Or, do we still need to keep the internal battery attached?

2. Can you please confirm my following understanding of the Seestar power operation? The Seestar has a low temp charging cut-off to prevent the internal battery from charging below 0C. So, ff we leave the battery pack in place and attach an external battery through the USB port will the Seestar continue to operate as normal below 0C using the power from the external battery? We could put the larger capacity external lithium ion battery inside a cooler to keep it above 0C so as not to damage it as well. We could also add a heating pad inside the cooler if needed to keep it warm. Then folks in cold climates would not have to worry about damaging the Seestar internal battery pack. People already have setups like this for their other astronomy rigs.

3. You mention a 65W fast charger. First, one of the specs in the Seestar documentation calls out 12V 3A as the maximum charging power, i.e. 36W. This is in conflict with the 65W. Also, keep in mind that lithium batteries should not be charged at higher than 0.5C current where 1C is the maximum current rating of the battery. And, every battery manufacturer suggests the optimum and preferred charging current is 0.2C. For the 3.7V 6Ahr batteries in the Seestar 1C = 6A. So 6A would be 1C for these cells which is way too high of a charging current if you want the battery pack to last for its rated life. When you charge a lithium ion cell at a high current the same metal plating at the anode takes place even when the temperature is not below freezing because too many lithium ions are arriving at the anode faster than they can intercalate in the graphite structure.

Best Regards,
Curtis

I did some more research and found a S50 user the uses an external power all in one unit and used the USB-A fast port to USB-C cable to the S50 and he says that (what concerns me is) when the ZWO battery is 50% or 30% the power unit will charge the S50 battery when below 32 F degrees, (we don't want that) but also uses the power unit to power the S50 all night.

So Good news is something that can power 5v - 12v 3 Amp USB- A to USB-C, or USB-C -USB-C 60 watt PD cable can do this!
Bad news is the S50 when temps are below 32 F degrees will still try to charge the S50 battery pack slowly. This person noted it was like 30% and out in the cold all night was at 50% charged. I would suggest fully charge the S50 battery and then use a power unit so the internal battery should not recharge and then the S50 will power as long it can get 5v -12v 3 amps all night.

ZWO can you confirm this is the case? If the S50 battery is at 30% will it slowly recharge when below 30%, maybe old firmware? As you NEVER want to charge a Lithium battery below 32 F degrees as it will start to damage the battery's chemistry.

Support@Seestar can you please answer my 3 part question above? These go to the heart of what everyone wants and needs to know so that they can use their Seestar in the cold but not damage the battery.

curtismacc Sorry to keep you waiting. I haven't seen your message in the last few days due to other work matters, so I'll respond to your questions one by one now:

1. The S50 does not support removing the battery pack from the unit, you cannot do this. You can connect an external power supply to use the S50, but you need to keep the battery. But first of all, you should know that using S50 while charging will not lead to S50 damage nor damage the battery, but it may reduce the life of the battery. Because lithium batteries are charged and discharged about 500 times (charge from 0-100 counts as one time, 50 charge counts as 0.5 times)

2. Connecting the power supply at 0 degrees Celsius does not ensure that charging can be carried out properly, but it will not affect the use of the S50. But as I said in the first article, it will battery reduce the life. We don't recommend and support modification of higher capacity battery packs for modification. You should be aware that the S50 will not be damaged or rendered unusable at 0 degrees Celsius, but prolonged use at low temperatures will reduce the range, what would normally last 6 hours may only last 4 hours at low temperatures. The heating pad just may make the S50 charge normally, there is no protection for the battery.

3. Using a 65 watt charger will not damage or affect the battery, because although the charger is powerful, the S50 only needs so much, it just increases the charging speed, it will not affect it. If you are not sure, you can use a 36 watt charger.

cengell You'll have no problem charging the S50 with this charger.

cengell Below 10 degrees Celsius the S50 will not continue to charge, lithium batteries are characterised by not being able to charge at too low a temperature.

Support@Seestar Thank you for the detailed answers. As a follow up:

1. Yes, while waiting for your reply I took a look at the battery and noticed that it has 3 wires, 2 for charging and 1 for the thermistor which reports the battery temperature back to the Seestar software so that it can prevent charging below 0C and above 40C. And I do understand about the 500 full discharge cycle spec as I have worked with Jackery, Li Time, Bluetti, EBL and GoKWh to test and review their batteries and/or portable power stations.

2. We are talking about using the power from an external source with the Seestar battery fully charged so that the Seestar draws power only from the external power source as the Seestar battery will be below its charging cutoff temperature of 0C. That should have no effect on the Seestar battery cycle life since it is not being charged or discharged in this scenario. My understanding is that when the Seestar battery is fully charged, the Seestar will draw power from the attached external power source and not the Seestar until the external power source is depleted. Please correct my understanding on this part if I am wrong.

3. I understand that using a high rate charger will not overcharge the Seestar battery. But, as I said above, every lithium ion battery manufacturer recommends charging no higher than 0.5C and preferably at 0.2C. In the case of the Seestar battery that would be 3A and 1.2A. The physics works the same for the Seestar lithium ion battery as it does for every lithium ion battery as I described above. I know folks are anxious to re-charge, but with lithium ion batteries, slow is better to maintain, in this case, the 500 full discharge cycle rating.

Again, thanks for your detailed information. I hope that you will check out some of the physics properties of lithium ion batteries which I have mentioned here so that you can better advise Seestar owners.

Best Regards,
Curtis

curtismacc Firstly, thank you for your careful analysis and understanding, you are professional enough.
About your second question, you understand incorrectly. Let me explain: Seestar needs the battery as a power source to provide electricity, that is, at this time the S50 is low on power and needs to be recharged, after connecting to an external power source, the S50 is still using the power from the battery, and is not directly recharged by the external power source. When the external power supply is connected, the power provided by the external power supply will be stored in the battery, and the battery will then provide power to maintain the normal use of the S50. I hope you can understand.
The third problem you don't need to worry about, we provide batteries for purchase, just buy them again when they are broken. But generally speaking this problem will not occur.

Support@Seestar
Forgive me for wanting to confirm my understanding of you response to my second question, but there are many, many folks with a new Seestar living in places where the temperature drops below 0C frequently during the winter months who need to know exactly what to expect.

So, if I understand what you are saying, the energy from the external power source is used to continuously recharge the internal battery while the Seestar's components (camera, motors, heater, computer) run of the energy from the internal battery. If true, this would mean that once the thermistor inside the Seestar battery reports the temperature has dropped below 0C it will no longer accept charge from the external battery. Charging from the external battery will stop at 0C and the Seestar can continue to function only until the internal battery is fully discharged even if the external battery still has lots of energy and is, itself, maintained above 0C.

In simplest terms, once the temperature drops below 0C the Seestar can only be run off whatever energy is left in its internal battery regardless of whether an external battery is attached. Is this correct?

Best Regards,
Curtis