Lithium Batteries for astrophotography

[JohnH]

Has anybody had success with using Lithium batteries for portable power of an AP rig? I have tried two different models from different suppliers but the results are the same. There is a swift decay in the output voltage such that I experience equipment dropouts after only an hour or so of use. The battery self check is still showing 80% capacity at this point but the voltage output is below 12V.



Fully charged these batteries seem to put out only 12.5V (no load) which is well below what a lead acid system would produce. It seems to me these batteries are ok for camping use but not for AP.


I have not been able to find a LI battery with a regulated output.


Happy to hear if you have found a solution.

[Wilsil (Wilco)]

I have used the 100Ah SolarKing lithium battery a few nights without any problems.
Everything hooked up: mount, camera, laptop, dew heater.

[muletopia (Chris)]

https://itechworld.com.au/collection...lar-golf-buggy


much cheaper than the solar king

and will probably do the same job
Chris

[gregmc (Greg)]

When you say Lithium, you perhaps should qualify it as multiple types of Lithium batteries exist and they behave differently.

It might be a battery people often use to power a mobile etc. They usually use the same technology as lithium batteries in cameras, mobiles etc which is Lithium Cobalt. (and can also explode etc as a mobile battery can do)

Lithium batteries used in the RV/Camping industry are usually Lithium Iron Phosphate (or LiFePO4) - BTW - Which don't explode

Don't use a Lead Acid battery charger on LiFePO4. It just will not fully charge no matter what the advertisement may claim. It will also not charge as fast as a charger with a Lithium charging profile (because lead-acid chargers have an anti sulphation phase). Depending on the battery specifications, unlike lead-acid batteries, the charge voltage will need to be around the 14.5v. A charged battery will be around 13.8v (ie. 12v is a nominal voltage).

Understand your load - i.e. Know what the max current draw from the battery. Multiply the load by the time to get a rough capacity requirement.
Target a 50% depth of discharge as you will get a lot more discharge cycles from the battery at this rate and it will give you some wriggle room if say your dew heaters use more that night or you want to spend a bit more time in the field or that new camera uses more power to heat to your new lower temperature you decided to run at that night.

LiFePO4 have a reasonably flat discharge curve so measuring the voltage to get an idea of it's charge state is a bit useless. Either get a battery with built-in capacity level monitor (such as Enerdrive or Invictor with associated mobile app via Bluetooth) or use a lithium compatible battery monitor (with appropriate current shunt) from Enerdrive or Victron (and not a cheap junk monitor built for lead-acid batteries)

So LiFePO4 with a proper lithium charger (such as a Victron charger) charging close too but under the max charge rate specified by the manufacturer is the best. Fully charge at the beginning of each session is the best at keeping the DOD small.

Having a built-in capacity monitor is the easiest way to go

Understand your load. It's no good buying a battery based on the physical size and expecting it to carry your load.

Don't forget to fuse the positive as close to the positive terminal as possible with an appropriate fuse to protect the wiring (from shorts etc)

Keep the battery as close to your gear as possible and use the thickest wire possible to reduce voltage drop.

Think about using anderson powerpole connectors (Rigrunner is a good example of a fused solution) in place of the cigarette style connectors.

I hope this helps with the lithium battery discussion

cheers
Greg

[JohnH]

OK Greg, I was trying not to do this but I will name names here, the two products I have tried are :

The PowerTech Lithium Powertank and the iFourway Lithium battery. Both were sourced from astronomy suppliers.
I am not aware of the chemistry - I assume LiFePO4- but could be wrong. Both were used only with the charges supplied.

Neither of these units produce more than 12.5V when fully charged and both showed a RAPID but small (0.5 to 0.7) drop in the first 30 mins of use and yes, after that, it is flat(ish) BUT this is of no use to me as the output is then down at 11.8V (and still dropping of course) or so at which point my NUC becomes glitchy. It seems when fully discharged these systems output as little as 9V.
The issue here is not to do with attached load (my rig's current draw is 3A max - but typically << 2A) while the capacity quoted is ok for my purpose (2-3 hrs in the field) it is not accessible in my case, I can only get only to about 25% discharge (according to the inbuilt level meter) before I start to get drop outs.

I was after an integrated, portable solution - I was hoping not to have to build my own but, perhaps sourcing the charger and battery plus relevant connectors etc is a better option. I take your point re capacity and perhaps 100Ah is a better target for me.

NOTE: I also have a small powerbank (probably the nasty LiCo) bought from Officeworks - and that allows me to select an output voltage and will drive my system happily for 3-4 times as long as either of the two options above despite being rated at only 20000mAh...

[Wilsil (Wilco)]

Originally Posted by muletopia

https://itechworld.com.au/collection...lar-golf-buggy


much cheaper than the solar king

and will probably do the same job
Chris

Cheaper indeed because it is only 24Ah while the SolarKing is 100Ah.
If you compare Ah cost, SolarKing is cheaper.

[JohnH]

Originally Posted by Wilsil

Cheaper indeed because it is only 24Ah while the SolarKing is 100Ah.
If you compare Ah cost, SolarKing is cheaper.

Yup - I got excited there for a minute....

[JohnH]

Originally Posted by Wilsil

I have used the 100Ah SolarKing lithium battery a few nights without any problems.
Everything hooked up: mount, camera, laptop, dew heater.

Do you have a neat way to connect this up - use a battery box - any recommendation?

[AdamJL]

I've got and use both a LifePO4 battery pack (Solarking) and a Lithium NMC (Jackery) on my rig.

The Jackery (240Wh) powers my mount, dew heater via DC output, and laptop via the Sine-wave output. Note the Jackery is one of the very few REGULATED lithium packs out there, so I get guaranteed 12V output. This is really important! Many lithium batteries can drop voltage as the power levels drop which is not good for your mount or other electronics that require 12V minimum.

If the Jackery power levels drop too far during a night, I'll top it up with the Solarking (192Wh) via the DC-in.

I did use the Solarking exclusively before I bought the Jackery but it didn't have the AC out plug I needed for my laptop, so got the Jackery.

I'm now going to wait until May when the next batch of Jackery's hit Australia and either get the Jackery 300, 500, or even wait until Bluetti's AC50S hits Australia (I chase the company regularly, it'd be great for others to do the same )

[Wilsil (Wilco)]

Originally Posted by JohnH

Do you have a neat way to connect this up - use a battery box - any recommendation?

At the moment the battery has a cig lighter plug with those battery crocodile clamps.
A 4-way splitter is plugged in which powers the mount, dew heater, laptop directly and the DSLR through a 50W invertor.

[JohnH]

I think I will be going for this:


https://itechworld.com.au/collection...-50ah-itech500


It is regulated and has sufficient capacity for my needs....or perhaps wait for the 100Ah Jackery units to come in. Anybody used this company and/or their products? They are in Perth and I am in Sydney, I would prefer a local supplier if there was one...

[Rerouter (Ryan)]

I've gone the approch of modifying all my gear to handle higher voltages and running it off a 153Wh external laptop battery at 16V. I would hazard a guess that a fair amount of gear could be run off this voltage once verified.

For me its peace of mind knowing that 7-32v is fair game. And having decent reverse polarity protection.

For runtime take your gears consumption current. Times it by the supply voltage and you have rough watt hours. For me I know my battery lasts me multiple nights of astro. But cooled cameras and cranked up dew heaters would shorten that.

[AdamJL]

Originally Posted by JohnH

I think I will be going for this:


https://itechworld.com.au/collection...-50ah-itech500


It is regulated and has sufficient capacity for my needs....or perhaps wait for the 100Ah Jackery units to come in. Anybody used this company and/or their products? They are in Perth and I am in Sydney, I would prefer a local supplier if there was one...

that looks great!
I reached out to that company last year when I was researching this stuff; they didn't have regulated power supplies, so it's awesome to see them offering something now
If you get it, please let us know how it goes, I'd be very interested in it as well!

[JohnH]

Ryan that is a great suggestion, all my kit is fed power via an Eagle3 which will be quite happy to accept 16V and output 12V - in fact this is what I have as a temporary solution as the Powertech tank is not useable. The unit I have is only 20000mAh but at least is has selectable output voltage.


I did not realise you could get such large capacity units. Can you point me at the supplier please?


On another topic - researching the itechworld company online raised a few red flags - given the price and the location of the company I have decided not to go that way.


Never imagined it would be this complex to find a suitable battery...seems there are a lot of suppliers misquoting capacity of these units....caveat emptor I guess.

[Rerouter (Ryan)]

My exact one is an EL1901 however seems they are no longer sold as far as I can tell. Getting a tad old. As i bought it in 2017. It has 18x 2400mAh cells in it. Has balancing. Trickle charging and electrically is built to be really hard to kill

I plan to eventually replace the cells as 2 have failed short during 2 years without charging it. But the balancer is smart enough to now only charge up to that new max voltage. Derates the charge current for weaker cells. and atleast on 16V is running fine on that lower max voltage

What I have found that heavily borrows from that design is this. However I cannot speak for its internals. atleast seeing as the dimensions and exterior look similar, I would guess its 18x 2900mAh cells.
https://www.bixpower.com/Bat-BP160-p/bat-bp160.htm

[JohnH]

I returned my Powertech unit for a refund and purchased a 50000mAh external laptop battery which has a switchable output from 5 to 20 V. It arrived yesterday and happily drove my setup for 6 hrs.

[Wilsil (Wilco)]

Originally Posted by JohnH

On another topic - researching the itechworld company online raised a few red flags - given the price and the location of the company I have decided not to go that way.

Location is fine

[AdamJL]

Originally Posted by JohnH

I returned my Powertech unit for a refund and purchased a 50000mAh external laptop battery which has a switchable output from 5 to 20 V. It arrived yesterday and happily drove my setup for 6 hrs.

Have you got a link to this at all?

[kalon (Kevin)]

I went with a Hardkorr 4WD battery box (2x cigarette ports, 2x USB) and a Renogy 50AH LiFePO4 battery. Powers my NUC, portable monitor, HEQ5 Pro mount, dew heater, ZWO 1600MM camera cooled to -15C and charges my iPad while I am playing Hearthstone or Slay the Spire. Lasts all night and barely dropped voltage (from 13.4V to 13.0V) so plenty of capacity left over.

I recently added a second battery so I now have 100AH and recharge it every... few months.

[Rerouter (Ryan)]

50000mAh x5V = about 250Wh (may be x3.7V if the designers chose there specs in a misleading way)
100Ah x 13.2 = 1320Wh

Take the nominal voltage x the amp hours to get watt hours to get an estimate on how things compare.