#149823  by Nut17
 Fri Mar 15, 2019 8:40 am
This article pretty well sums up the reasons why I am totally committed to LiFePO4 batteries.

Why Lithium?
What does lithium give you that the old lead acid technology doesn't?

Faster charging and discharging
Lithium batteries will accept a charge much faster than lead acid. This means your battery can take the charge from your solar panels, DC to DC charger or mains charger as fast as they can give it. This can mean the difference of an hour vs a day to recharge from mains power.
The fast discharge allows you to run appliances that require a sudden peak load without a serious drop in voltage. This would apply to air conditioning startup, microwave ovens, induction stoves, coffee machines, bread maker, etc.
A lithium battery can accept 100% of its advertised capacity (100amps per 100Ah) before the battery voltage is affected. This is because lithium batteries have a very low internal resistance. They have a very low internal resistance because they work by lithium ion transfer rather than the chemical reaction that lead acid batteries use. A lead acid battery can only be charged at 20% of its advertised capacity (20 amps per 100Ah capacity) before the battery's internal resistance will cause the battery voltage to rise faster than its true state of charge.
They weigh less per amp hour
Lithium batteries weigh a lot less than lead acid per useable amp hour. So you can either save some precious weight allowance in your RV, or upgrade to a higher-capacity battery for the same weight.
For example, a lead acid battery's weight is between 30kg and 32kg per 100Ah. If your 100Ah lead acid battery weighs less than 30kg, it is not a 100Ah battery - you've been ripped off.
A 100Ah lithium battery weighs 16kg. As mentioned before, a lead acid battery can supply 50% of its capacity from fully charged before it drops below 12V under load. A lithium battery can supply 100 of its capacity from fully charged without dropping below 12V. This means effectively, per useable amp hour, lithium weighs a quarter of the equivalent lead acid.
They like to work
The days of keeping a close eye on your battery voltage for fear of shortening the life span of a lead acid battery are over when you switch to lithium. Lithium batteries discharge without a serious voltage drop due to their low internal resistance. They don’t have to be returned to 100% state of charge (SOC) each time they’re discharged in order to keep a good cycle life. They like to work, so there is no need to fear shortening their life by working them hard. They will actually thank you for it.
Trouble-free storage
Lithium batteries don't like to be stored at 100% capacity and don't need to be regularly recharged the way lead acid batteries do. Hard to get your head around, but it's the complete opposite of what you've known about batteries so far.

They have a much longer cycle life
Just how long, we don't really know, as we haven't had any die of old age yet, but let me explain the advertised figures of lead acid and lithium batteries.

A cycle for a lithium battery is measured by charging the battery to 100% state of charge, then discharging to 0% state of charge. This is one laboratory cycle. However, that's not how most people use their batteries, but we're talking about figures advertised by the manufacturer here.
A lithium battery will cycle from 100% to 0% state of charge for 1000 cycles while retaining 100% capacity.
It will cycle a further 4,000 cycles (total 5,000 cycles) and still have 80% capacity remaining
It will cycle a further 2,000 cycles (total 7,000 cycles) and still have 70% capacity still remaining.
A cycle for a lead acid battery is measured by charging the battery to 100% state of charge, then discharging to 50% state of charge.
A lead acid battery will cycle from 100% to 50% state of charge for 600 to 700 cycles before it will permanently drop below 60% capacity, in other words, 10% capacity remaining (they can only be discharged to 50% before they reach end of life).
You can use more of the available amp hours
A lead acid battery can only give you a maximum of 50% of its available charge before it drops below 12 volts under load.
Lithium can supply a much higher load without voltage drop or loss of capacity. Let me explain what I mean by loss of capacity:
A lead acid battery (AGM, gel, flooded cell, lead crystal) has its capacity rated over a 20 hour discharge (C20). This means for a 100Ah battery, the maximum rate you can discharge is 5 amps to still get the full 100 amps - or truly 50 amps to 50%. If you try to discharge the battery faster, some of the capacity is lost. This is known as the Peukert Factor.
So, if you discharge at a rate of 10 amps, the total capacity of a lead acid battery reduces to 90Ah. Because you can only dishcarge a lead acid battery to 50% before the voltage drops below 12V, you in effect have only 45Ah available if you discharge the lead acid battery at a rate of 10 amps
 #149827  by mattn
 Fri Mar 15, 2019 9:58 am
Every 'Why should you' deserves are 'why not'.... Only 'Why not' I can think of is cost......

Its not only the initial cost of the batteries, but the cost of the charger(s) to make use of the advantages. If you want to take advantage of 1 hour charging into 100AH batteries, you need a 100AMP charger.

Related to cost is the life cycle argument - for a full timer its a not a question. For a full time worker with three weeks use over summer and a couple of long weekends, the batteries (lead or Lithium) will die of old age before the cycle count gets anywhere near killing them.

I am still on Lead Acid - largely because I cannot justify the cost of Lithium (helped as until recently I had a (legal) source of free lead acid batteries.). If I had buy new at retail price, it would be a tough choice even for me in the 'three weeks and a couple of weekends' end of the spectrum.

As an aside, and it s a real peeve of mine - The author makes a series of 'statements of fact' about lead acids are inaccurate. Anyone with more than a basic understanding of Lead Acid batteries would the suspect the facts presented in entire article are equally flawed and possibly be put off Lithium batteries as being 'too good to be true' being sold by a snake oil peddler.
 #149828  by myles
 Fri Mar 15, 2019 11:15 am
Agree with mattn. A very biased article that deliberately overstates Lithium and understates Lead Acid. No mention of any of the negatives of Lithium...but overstates the negatives of Lead Acid and no mention of the positives of Lead Acid...
 #149829  by Nut17
 Fri Mar 15, 2019 11:48 am
Interesting comments - but both from those who have not used them. One point of reference. You do not need any specific charging systems. If you have say a 30 Amp mains charger - this will deliver a solid 30 Amps to a lithium battery until it is at a 100% SOC. The same charger hooked up to lead acid batteries will begin tapering off the charge current at about 85% dropping of to a mere trickle as it reaches 100%.

Yes, the cost is significant, but with a design life of 15 years and an estimated life of 20 years ( The battery can be transferred to any RV upgrade) - The cost soon becomes very realistic.

I am a definite convert, and the author of that article has been my mentor through my conversion to lithium in early 2012 and we still communicate comparing ideas and systems. http://t1lithium.com.au/why-lithium.html
 #149832  by DarrenM
 Fri Mar 15, 2019 2:38 pm
Yep cost is the only down side I can see. But its a pretty big one, and with the worldwide demand for Lithium its not likely to get any better any time soon.
For me personally, only if I can get them at the right price, will my build will include LiFePo4.
Sure I want them, I know they are way better. Everything else I own is already running on Lithium batteries, even my car so I am well familiar their extreme capabilities, and yes you should believe the hype, they are extreme in every way.
But I don't really need a 20+ year battery life, I'm building a bus so weight isn't really a factor either. It's purely performance (and coolness) vs dollars.
Fact is, if I stumble across a great deal on lead carbon, or some damn near free acid filled batteries from the ark, my lithium dreams will remain dreams. But maybe cheap cells from Aliexpress....
Damn you Chris for reminding me Why Lithium
 #149837  by myles
 Fri Mar 15, 2019 6:14 pm
Nut17 wrote:Interesting comments - but both from those who have not used them.
I have used them!!! As seems to be an ongoing theme...miss information...
 #149936  by NeilV
 Thu Mar 21, 2019 3:12 pm
And here’s a pretty sweet price on TM at the moment... with 7 years warranty left too!
https://www.trademe.co.nz/trade-me-moto ... 387942.htm

Compared to their source: $1555
https://aasolar.co.nz/AA%20Solar%20Pric ... #Batteries

My issue is now having set my whole system up in 24v, I’d need 2 🤔
 #149937  by Nut17
 Thu Mar 21, 2019 4:13 pm
That is identical to the ones I recently purchased for $875 each (Second Hand 2 years old)
An excellent purchase for someone wishing to dip their toes into the lithium pond.
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