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Thinking of throwing some cash out on one of those cheap lifePo4 lithium batteries.
Price ranges seem to be around $850 - $950 for a range of 12v 100Ah batteries, then they drop down to around $500, most likely chinese seconds I guess.
Why am I looking at these? Well I need a new battery for a medical appliance, only needs to be 12v 50Ah, looked at LifeP04 but they're still around $450.00, so me thinks, why not get one of these cheap 100Ah ones.
OR ARE THEY A COMPLETE WASTE OF MONEY??????
Was looking at some specs on these today. All seemed to have battery management systems onboard, so drop them in where the agm was.
I did see that the cheaper ones can not be set up in parallel, and the maximum current draw was around 50 amps compared to 200+ on the expensive ones, which can be parrallelled.
Lithiums can be cycled MUCH much more deeply than an agm, and can be recharged MANY more times.
Not a waste of money, but the price will keep dropping.
The only two that I have any experience with are Itech and these http://www.lowenergydevelopments.com...thiumBatteries
I haven't had any problems yet with Itech and the Low Energy ones are only recent so to early call.
Both have good reviews so far on the W.W.W.L.B. (World Wide Web of Lying Bastards)
If you want up to a 3,000 amp draw for winching and literally bullet proof option you want these http://www.lowenergydevelopments.com...name&order=ASC
I've been looking on that website ET.
They offer 5 year warranty on just about all their lithium batteries which is the longest warranty I've seen yet.
Never had experience with the cheap ones but I have 2x50ah 4s propower lithiums ($600 each) running a 24v 3000w inverter in my shed. They run all my power tools bar the welder & compressor. They are rated to 100amp discharge current. They go hard.
https://www.ebay.com.au/itm/Pro-Powe...xX6YVaIqIWtn5A
Yow, how long have you been using them mate?Quote:
Originally Posted by pollenface
Sounds like a fair system but a bit low on watt hours and discharge current compared to the itech 120 ah units at around 900?Quote:
Originally Posted by pollenface
All of the drop in Lithiums have some sort of battery management system built in, inside the case. Many (most? all?) are of a type which shed excess current as heat. At the point they need to shed current, the batteries will already be close to being over voltage & thus getting hotter. Adding further heat, inside a sealed box is the last thing they need. Add in the fact that a major benefit of lithiums is their ability to accept high charge rates increases the possibility of more heat being shed by the BMS. The BMS will be a printed circuit board, & these too can fail if they are consistently overheated, without any access to air cooling. With a 'drop in' replacement if the BMS dies, the whole battery is cactus. The result will be a shortened lifespan of the battery. In addition, many of the cheaper battery management systems (BMS) will be just that, working only on overall voltage, rather than a cell management system (CMS) which incorporates auto cell balancing as required. Getting cells too much out of balance does occur with lithiums & can cause premature failure.
The above is a summary of my understanding of what a friend in the business of building, supplying & fitting lithium batteries has told me. He believes that for a long reliable life it is essential for a lithium battery pack to have a BMS which incorporates a CMS & that this should be external to the battery pack. I'm only repeating what I have been told, personally I have no experience of Lithiums. I do know however that were I to pay the significantly higher price for lithium over AGM (or other lead acid battery types) I would want them to last at least as long (ie. a minimum 10 year lifespan).
If the medical appliance is a CPAP machine, I run mine without a 2nd thought - average 20Ah per night or 26Ah with humidifier. If your solar/battery system is likely to struggle with similar 'extra' load. It may be a *lot* cheaper & more effective to stick with AGM battery(ies) & just add a bit more charging input (another solar panel, and/or dc to dc charging), space permitting.
Last year I bought a 12v 50Ah AGM for the CPAP and after about 3 weeks the battery was dying mid night. Each day I charged the AGM via a Nocco charger I was running off my inverter as I drove. Each day the AGM was fully charged. The AGM was around $170, maybe not the best brand, maybe a dud AGM, but maybe then again it may have been the best AGM for that price, we don't know.Quote:
Originally Posted by Cuppa
So I know I can charge anything.
Do you keep your battery on some type of charger overnight while in use Cuppa??? An inverter or similar?? What brand of battery are you using??
I suspect it may not be a battery problem per se, but rather a CPAP machine which uses way more than mine - most do. It is quite likely , for example, that a Resmed machine will want 50Ah+ per night, more if humidification is used. More if you need a high pressure setting. Essentially I suspect that a 50Ah battery is too small for the use you are putting it too (regardless of what the machine's manufacturer might say!). If I'm correct, then a 50Ah Lithium will be no different . You would either need a larger battery or a more efficient cpap.Quote:
Originally Posted by 10G
No my batteries are not charged overnight. Only via solar or from DC to DC when driving. I probably have more battery & solar capacity than you, but the batteries are generally back to float by mid to late morning each day regardless of whether we drive or not. That is with overnight use by lighting (minimal), a 60 litre fridge, a 35 litre freezer, phone & laptop recharging & the Cpap which gets between 6 & 9 hours use a night. Batteries (3) are 120Ah Ritar, DC series.
Provided your Nocco charger has sufficient output (amps) to bring a battery back to float each day within your driving period then I reckon larger capacity battery is what you need. How much larger depends upon what else yo run from it other than the cpap. If only the cpap I'd say a 100Ah should do the trick, 120Ah if you can fit it. Only reason to make it a lithium is if you want less weight (hard to justify the weight saving/cost ratio alone though), or if you expect to be regularly only driving for insufficient time to get the battery back to float (& even then, it would probably be cheaper to invest in greater charging (bigger charger or more solar) than to go with lithium.
Don't get me wrong, I'm not anti lithium, but just believe that lithium only makes sense if you need it for high current devices/fast charging/less weight. Without the high current devices (eg. coffee machine, hair dryer etc) I personally feel it is hard to justify the higher cost. And I also remain unconvinced by the 'drop in' lithium options. I will probably go lithium (with external battery/cell management) when my AGM's die (now in their 8th year) if still planning to keep the Patrol & if it's convenient at the time, primarily to lose weight - I would expect to save around 60kg if I replaced 360Ah Agm with 200Ah Lithium. I does only make sense (for me) if it were a long term investment though.
Thanks Cuppa. I did take a look at the cpap running specs & it listed the m/c in the 25Ah range, hence the 50Ah battery. The Nocco just illuminates an LED at 100% when it thinks it's completed it's work, so I just go by that.
Thinking about it, you may be right, maybe the cpap m/c is pulling more power than they state.
Might talk to local sparky and see if he has anything to measure power while the device is running.
You'll have to take an average, as the power consumption rises & falls with breaths in & out - or at least mine does. You'll need to wear the mask & get it up to pressure, with the humidity turned to what you usually use. (including a heated tube if you use one). I just use the battery monitor I have to see the power consumption in real time. The sparky will probably have a clamp meter he can put arpund one of the battery cables (with everything other than the cpap turned off).It's a quick & essy task so long as the positive & negative can be accessed separately.Quote:
Originally Posted by 10G
just ticked over 12 months, I have 500w of solar and a cheap 30amp PWM controller keeping them topped up.Quote:
Originally Posted by 10G
$900 is a fair price for a 120ah unit, I'd assume it to be of reasonable quality.Quote:
Originally Posted by Mickhead
I only slapped my system together for a bit of fun, the 2x50's do surprisingly well, I never see them below 26v. If I was to do it again I'd run a 48v system with 6000w inverter, maybe that would run my compressor :)
So I'm looking again at a lithium battery,
Prices have come down a few hundred bucks since the start of the year.
One thing that annoys me is how some brands are labelled as lithium IRON and not lithium ION, it's ION, AFAIK there's no such thing as lithium iron, but there is such a thing as lithium ion.
Maybe this is how we can tell the difference between a genuine well engineered battery and a relabelled chinese second, the 2nds are made with iron!
I thought Renogy were not a bad brand, but they're labelled iron. Might go with a solar king 100Ah or 120Ah, not 100% sure yet??
Have a look at this link, it will describe the difference between both.
Happy reading [emoji6]
https://goenergylink.com/blog/key-di...ron-batteries/
Sent from my iPhone using Tapatalk
Haven't read it yet, but thanks I will, looking forward to learning something.Quote:
Originally Posted by Maxhead
Good link, I learnt something new. That’s my quota for the day done.Quote:
Originally Posted by Maxhead
Same here Jack.
I've got a dumb question. If I have a device that draws that 20Ah and run it for 6 hours off a 120Ah battery, does that mean the battery will be completely flat after 6 hours? Is it that simple?
Assuming a standard Lead Acid tech battery and if the 20Ah device does not have a low voltage cutout...Quote:
Originally Posted by 10G
It will be "completely" flat well before 6 hours due to other losses.
It will be "effectively" flat after about 3 hours
You will risk damage to the device/cable/ after 2 to 3 hours because as the battery supply voltage falls the device will draw more current IE as the battery voltage falls the current draw will increase proportionally (P = E x I ... where P equal power, E equals voltage and I equals current).
or...
if the device is voltage sensitive it will not operate at best efficiency which is equally likely to damage it.
Edit... Devices are rated in Watts not A/H so whilst the above is not exactly technically correct, I left it as is to avoid confusion.
Thanks ET.
I disagree with that part. The power delivered will not remain constant so the logic of applying that formula is flawed. As the voltage drops, so will the current supplied, so the power delivered will reduce with the voltage. The possible exception to this would be a brushed motor load which will increase the current draw as its speed reduces and be max when it is stalled, but the voltage would be quite low at this point. And that formula still does not apply.Quote:
Originally Posted by the evil twin
For lights, analog loads, leccy motors etc I agree with you 100% and my original wording was a tad poor...
but...
DC/DC chargers or Supplies and the Digital Power Supplies associated with or found in a lot of medical or electronics are all examples of devices that often have constant power consumption independant of input voltage.
The whole idea of these devices is that no matter the input voltage/current they deliver a controlled output to the load.
DC/DC chargers in particular are notorious for being a source for blown fuses and burnt out wiring or connectors in equipment power circuits.
When/if the vehicle supply voltage falls due to smart alternators, wiring voltage drops or other loads, the device compensates and pulls more current to get the same power output and a failure can occur especially if connecting a DC/DC into existing wiring.
Found this here:
https://www.evergen.com.au/batteryte...gydifferences/
Thought it was worth putting up ...
For manufacturers trying to decide whether lithium-ion or lithium iron phosphate will be ideal for applications, consider these key factors:
Highest energy density: lithium-ion
Good energy density and lifecycle: lithium iron phosphate
Stable chemical and thermal chemistry: lithium iron phosphate
No thermal runaway and safe when fully charged: lithium iron phosphate
Portability and lightweight characteristics: lithium-ion
Long life: lithium iron phosphate and lithium-ion
Low costs: lithium iron phosphate
Also, take the operating environment into serious consideration as well as any vibration issues that may be experienced. These instances may influence a manufacturer’s choices as the chemistry stability that lithium iron phosphate offers are superior than that of lithium-ion.
Not long after making this post both of my lifepo4 deep cycles had BMS failures.Quote:
Originally Posted by pollenface
Knowing what I know now, if I wanted to do it cheaply I would buy the individual 3.2v cells and use my own BMS and run important loads straight independent of the BMS.
Not being critical just making an observation but a 3000 Watt Inverter can demand a shit load more than 100 Amps so that may have been what cooked the internal BMS.
A 3kW Inverter running off a 24 Volt supply can draw well over 200 amps momentarily.
I agree.
Live and learn.