Lead Acid battery vs Lithium battery for solar panels?

Thread Starter

Interestor

Joined Jul 25, 2021
16
I am looking into these batteries. As of now, i only know that the difference between the two are costs and charging efficiency What other pros and cons are there?
 

LowQCab

Joined Nov 6, 2012
1,096
Weight / Bulk,
Corrosive / Explosive Gases,
Chemical Reaction Fires,
Tolerance of Physical and Electrical abuse,
Critical Charge / Discharge Voltage Tolerances,
Number of Charge / Discharge cycles before reduction of capacity,
Recycling issues,
Availability / Cost in large sizes,
There's probably more ..................
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.
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Irving

Joined Jan 30, 2016
2,067
Pro for Lithium:
  • Life: 10y+ v 1-5y depending on depth of discharge, # of charge/discharge cycles.
  • Size/weight: 2 - 3x energy density of lead-acid
  • Capacity: 100Ah lithium will give you 90Ah real capacity at C-rate, v 50-60Ah for lead.
  • Voltage: Lithium has nearly flat voltage curve from 95% to 10% SoC

Cons for lithium:
  • charging regime slightly more complex, needs more care in design
  • possibility of thermal runaway mitigated by good design & protective electronics or move to LiFePO4 chemistry (about 10-15% less energy dense but still >> lead)
  • Initial cost, but total cost of ownership over 10y is 25 - 30% of lead.
 

Ian0

Joined Aug 7, 2020
3,232
Initial cost, but total cost of ownership over 10y is 25 - 30% of lead.
If you use a lead-acid battery that lasts 10 years (a tubular plate battery) that is capable of 2000 cycles down to 25% capacity, then the lead-acid battery works out at about half the price of Lithium, and in case of failure, individual cells may be replaced.
 

crutschow

Joined Mar 14, 2008
27,714
I like old-school lead-acid due to its low initial cost, its safety (other than hydrogen explosions), and ease of charging, but there are obviously good reasons to go with lithium-ion.
 

Irving

Joined Jan 30, 2016
2,067
If you use a lead-acid battery that lasts 10 years (a tubular plate battery) that is capable of 2000 cycles down to 25% capacity, then the lead-acid battery works out at about half the price of Lithium, and in case of failure, individual cells may be replaced.
I'll have to take your word for it, never come across a manufacturer offering such a beast...

Lithium prices have dropped significantly in the last 18months which mkes them even more compelling.

Edit...
OK, I've just found one - Leoch Powabloc. Interesting, but they have a relatively poor discharge rate. 110Ah pack is only 90Ah @ 0.1C and 80Ah @ 0.15C. According to the datasheet they offer 1,160Wh of capacity at the 20H rate (4.8A) to 1.85v (90% DoD) compared to 1220Wh for the equivalent 100Ah Lithium (LiFePO4), which takes 1/3 the space, thats £200 compared to £122 for the LiFe. Actually the 100Ah are hard to find now as most manufacturers are making higher capacity cells in a similar form factor. So for £275 you can have 280Ah in the same space as the lead-acid, that's 2.8x the capacity for 1.4x the price!

My earlier price comparison is for traction (wheelchair) batteries, a much harsher environment, where 8 x 3.2v 200Ah LiFePO4 cells replace 2 x MK 73Ah 12v SLA batteries ie £600 (was £850) v £400. The SLA typically last 18mo - 2y so over 10y thats a TCO of £2000 for the SLA v (now) £600 for the LiFePO4, ie 30% (was 43%).

Edited to correct maths
 
Last edited:

Irving

Joined Jan 30, 2016
2,067
I like old-school lead-acid due to its low initial cost, its safety (other than hydrogen explosions), and ease of charging, but there are obviously good reasons to go with lithium-ion.
LiFePO4 is one of the safer, if not the safest, rechargeable chemistries. It has none of the thermal runaway issues that Li-ion has, is relative easy to charge and the costs are dropping fast. When you're paralysed on a wheelchair, running away if it catches fire isn't an option!
 

Ian0

Joined Aug 7, 2020
3,232
LiFePO4 is one of the safer, if not the safest, rechargeable chemistries. It has none of the thermal runaway issues that Li-ion has, is relative easy to charge and the costs are dropping fast. When you're paralysed on a wheelchair, running away if it catches fire isn't an option!
Like the pun on "runaway"/"running away"!

I'll search out some data on the tubular plate battery, but the manufacturer has re-done his website and I can't find anything any more. The tubular plate battery is the fork-lift battery. Single, replaceable 2V cells. We use them for off-grid power, and they seem to last 10 years, discharged to 50% every day, provided the customer remembers to check the electrolyte levels once a week (but when we remind them how much batteries cost compared to how much water costs, they soon remember)
Lead Acid doesn't seem much larger than a Lithium Ferrophosphate, but at 1.6 tonnes for 48V/840Ah rather heavier.
 

Irving

Joined Jan 30, 2016
2,067
Lead Acid doesn't seem much larger than a Lithium Ferrophosphate, but at 1.6 tonnes for 48V/840Ah rather heavier.
According to the Leoch data sheet a 12v 110Ah tubular SLA is 0.0121m^3 and weighs 30kg, giving 1160Wh,
thats 1160/30 = 38.7Wh/kg and 1160/0.0121 = 95.9kWh/m^3

(your 840Ah example I'd estimate @ 12v as 8200Wh, so 8200/400kg = 2.05Wh/kg! I know lead-acid doesn't scale well but that's rubbish)

A similar sized LiFePO4 is 12v 280Ah @ 0.010m^3 and 21.2kg, giving 3000Wh
That's 3000/21.2 = 140Wh/kg
and 3000/0.01 = 300kWh/m^3
 

Ian0

Joined Aug 7, 2020
3,232
(your 840Ah example I'd estimate @ 12v as 8200Wh, so 8200/400kg = 2.05Wh/kg! I know lead-acid doesn't scale well but that's rubbish)
840Ah @ 48V = 40kWh
40kWh/1600kg = 25.2 Wh/kg
(not fogetting that that includes the weight of the tank - It's the reading on the pallet-truck when I move it)
 

Irving

Joined Jan 30, 2016
2,067
840Ah @ 48V = 40kWh
40kWh/1600kg = 25.2 Wh/kg
(not fogetting that that includes the weight of the tank - It's the reading on the pallet-truck when I move it)
Ah, I put decimal point in the wrong place, mine should have read 20.5Wh/kg

You've used headline rate, I used a likely maximum rate, because voltage isn't constant, so assuming 2.2v @ 100%SoC, 1.75v at finish and straight line discharge then at 20H rate

((2.2+1.75)/2*840/20*24)*20 =39.8kWh
=39.8/1600 = 24.8kWh/kg

allowing for weight of pallet it's probably nearer 35kWh/kg

It's a moot point anyway because my wheelchair stops working at around 11.6v so on a brand new set of MK SLA 73Ah batteries you stop at around 60%DoD (because of Peukert effect).
 

Ian0

Joined Aug 7, 2020
3,232
I think that the main point here is that with regard to lead-acid batteries, "there's life in the old dog yet" even after 150 years.
Another factor worth considering is that the scrap-man will give you about £500 for a dead lead-acid battery. A similarly sized Li-ion battery might cost your £500 to dispose of it. The lead acid battery is over 90% recyclable, the lithium battery ends up in landfill where the casing corrodes, the contents leaks out and sets the landfill on fire.
 

Irving

Joined Jan 30, 2016
2,067
the scrap-man will give you about £500 for a dead lead-acid battery. A similarly sized Li-ion battery might cost your £500 to dispose of it.
I tried that with 6 dead MK, no scrapper nearby wanted them, certainly weren't interested in paying for them anything that justified my travelling costs. They went to my council recycling centre, who incidentally will take lithium too.
 

opera

Joined Jul 4, 2021
4
Whichever you choose, you will probably end up destroying your first set regardless of the planning done. Your anticipated needs won't be the same and hardware chosen was inappropriate. You may still be stuck in the ideas of the past when panels were more expensive than panels. You will likely under panel. I have a camp with PV hot water, refrigeration, dishwasher with heated dry and large capacity clothes washer with its own 40 gallon hot water tank, all cycles are done with hot water. Oh and a couple medical devices that keep me alive. I do that for 5 months a year and only have a car battery. Rain, no worries. I probably would like a little more capacity so I can get a big screen TV. Energy management is the secret.
 

Ian0

Joined Aug 7, 2020
3,232
There are other things that ought to be considered in choice of battery - Lithium mining destroying farmland in Chile, the working conditions of Cobalt miners in the Democratic Republic of Congo, China's dominance in the Lithium battery market, recyclability etc.
I would suggest that one should use Lithium Cobaltate if there is no viable alternative, unless they are "second use" car batteries, but who would really want to buy an ex-electric-car battery that has already lost 30% of its life, and you are paying good money to relieve the car manufacturer of his responsibility to dispose of the battery correctly or recycle it.
 
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