Unless i'm missing something* I can't see the justification for the extra cost, especially where size/weight isn't an issue.
They can last 10 times as long seems the boldest claim, what? 40+ years? Will I last that long?!
*Am I?
They are becoming popular where there is regular cyclic use.
1) They usually have their own Battery Management System, so are less likely to be damaged 2) They can be discharged to 10% without damage.Lead acid will sulphate up where charge is less than 50%. A 50Ahr lithium should be compared with a 100Ahr Lead Acid. 3) Can accept charge more quickly. LAs tend to have a low tail current and can take hours to put in the last 10% of charge 4) A cheap LA battery could be down to 100 charge/discharge cycles before toast, and at just 50% cyclic capacity. A lithium can be 3,000 cycles at 90% cyclic capacity.The only issues are one of temperature but generally a BMS will disconnect a battery that will be damaged through being charged or discharged out of temperature range.
If only occasional use, then I would agree that LA is the way to go. Cheap and cheerful.
I struggle to see the case for them in most consumer applications. The big advantage is capacity / weight but the cost to get this is very high and I do wonder if some of those who buy them for motorhomes with the idea they need them for wild camping have really done their homework.
I don’t have solar panels - although I’m considering them. While we don’t do wild camping, I was concerned about battery capacity when I replaced our (failed) three way fridge with a 12v compressor one. I looked at the spec and did some measurements before installing it. I estimate I can run it for the claimed 72hrs off the two 100 Ahr installed batteries ( ie using
100Ahr). That is adequate for wild camping !A compressor fridge is probably the biggest load most people would have. ( Running a three way off batteries isn’t practical - a typical load would be
10A + )
The biggest benefit for many people is a much shorter charging time than lead-acid. Where the battery is used deep-cycle, the owner often wants to get it back charged as quickly as possible.
I believe there's a capacity loss with time, independent of charge cycles. Laptop batteries only seem to last five or six years, with significantly reducing capacity before they die completely. It's a progressive reduction, so probably not dead cells, though the final ending probably is.
I noticed the other day that a moped user reckoned that the battery on his normal moped was Lithium, and hence a lot smaller than on previous models. I just wonder if cars of the internal combustion variety might be next? Brian
Lithium Iron Phosphate seems to be getting a lot more popular. The capacity is a bit lower because of the lower voltage per cell, but that also means the corrosion mechanisms that cause time dependent degradation in ordinary Lithium Iron cells is less active. They also don't tend to burn in the same spectacular way.
John
I think there are some cars with lithium instead of lead-acid starter batteries. Of course electric cars are mostly (all) lithium celled anyway aren't they?
They exist, and the fact you can start a car with a tiny lithium polymer jumpstart pack is a good indicator of the possibilities.
One of the issues though is lithium iron phosphate doesn't like being run in freezing temperatures. In a normal EV that's not a problem because you can use a little energy from the battery to warm the rest of it via the liquid cooling system, but it's harder to do in a typical car battery sized unit. It's also tricky when you need to take a low current through low temperatures, like running the alarm all night.
Much of the time a car doesn't need the full Ah of the battery - some is for margin (never discharge below 50%) and some to get the CCA required. I could imagine a scenario where you have a smaller/high current starter battery (like the lithium jumpstart pack) and then a battery sized for whatever auxiliary loads you have, maybe better able to run when cold.
I can see the advantage for LiFePO4 especially in places where you need a larger battery to run auxiliaries when you don't want the engine running - trucks with tail lifts, cranes, rubbish compactors etc etc.
Theo
My Suzuki is a soft hybrid with a lead acid starter battery and a Lithium battery to drive the small electric motor.
If the Lithium battery catches fire condolences to the passenger as it's under their seat.
It's quite common to have a large lithium pack and then a small 12V lead acid. The accessories and computers run off the 12V system, and the car won't turn on the traction battery until it is completely happy.
The lead acid is often a common point of failure, and I think there's general movement to transition towards lithium 12v batteries.
Theo
The one I'm getting has a lithium main battery (hybrid) and an auxiliary one which is calcium/lead-acid.
Some compressor fridges have a 'cold store' which means you run the fridge while you're travelling or on a hook up, then when you aren't you turn its power off. It'll stay cold for a day with zero leccy used.
Bill
As a measure of the CCA, when my car was having a little trouble starting, I connected a voltmeter and a clamp-on DC ammeter. The battery was fully charged to start (resting at 12.8). The meters were set to "peak record mode". The voltmeter measured 9.5V (set for downward peak value capture). The ammeter measured 150 amps. Just to give some idea what a lithium pack would have to provide. The 150 amp number is a little on the high side for a four cylinder engine, and should probably be around 100 amps. You can see in that case, my battery is NOT capable of 600 CCA, or anything remotely close. The internal resistance of the battery is too high, to draw 600 amps.
I understand some lithium cells can provide 20 amps under those conditions. Maybe you would need seven strings in parallel, to handle a 150 amp load.
Lithium cells come in Wh ones, and ampere ones. The Wh ones excel at slow steady loads. The ampere ones, are better for CCA applications. Like, flying a drone or running an RC race car. It's the ampere flavor that can do 20 amps. The high current lithium cells, hold roughly half the Watt-hours of the "power" version of lithium. In a BEV, those are "power" cells, to give the range.
Normally, watt-hour Li packs, want to be discharged over a 3 hour period. Rather than unleashing all the stored power in ten seconds. A traction automotive application is good, because the Li pack is discharging over a period of hours of driving. I don't know what an appropriate metric is for the power ones. Presumably you run those at 20 amps, until they happen to go flat. And it could be power ones, used in hand-held reciprocating saws or the like.
So if you re-cell Lithium, there are a few more variables involved than normal.
Paul
These are pouch cells, not cylindrical cells. eg these LiFePO4 cells:
You are not trying to start using a drill battery made of 18650s, these are cells chosen for the job.
(although I note DeWalt have started using pouch cells in some of their packs, presumably to help with high starting currents and discharge rates of some of their performance tools)
Theo
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