Battery tester

[Mrcoolabah1au]

Wow yes will wait for the test results to come through

[native pepper]

When comparing lithium to LA and the ah's they provide, there is only one real relevant test and that's how much usable energy is available above 12v in a 12v system. Below 12v the energy supplied is inadequate for many 12v uses and those that will still work, have to work harder with the lower voltages. In my experience, LA provides about 1/3 of it's energy above 12v, after that it's all down hill.

Lithium will provide more than 80% of safe usable energy above 12v and most of that is above 13v, which allows appliances, lights etc to give constant high voltages, meaning things don't have to work so hard. Have a set of 380ah gel batteries in my bus, which didn't remove when installing lifepo4 as they still work fine and they are well over 10 years old, so now they run all the 12v stuff and the lifepo4 runs all the 240v stuff. When the gel cark it, will replace with my 120ah lifepo4 pack, or a better lithium if there is one then.

The 12v gel are charged by the engine, through a 50amp DC-DC charger via a redarc and 60ah deep cycle 24v agm setup. So no need for different charge regimes, the solar handles the lifepo4 and the engine handles the gel, which being used for lights and other 12v stuff, will last over a week. However can switch the solar to the gel and can switch the engine to the lifepo4 if needed, so far have never needed to do that.

You can get as technical as you want, but it's the usable outcome that's important and you can tell when the gel it below 12v, the lights are much dimmer but with lithium, they will stay bright all the time and much brighter than anything LA can provide, as all their usable voltages are well below 13v. In my opinion the difference between performance and usability of LA compared to lithium, is wide, with lithium coming out on top by light years.

Also noted the claim of their longevity being unproven, yet my 3 system are over 10 years old, still provide 100% of their capacity and have a li-ion battery in my camcorder, that is now either 21 or 19 years old and still performing, although the last year has seen it lose some capacity, but it still works well and will probably go on for a few more years.

Even the lifepo4 car starter batteries I experimented with years ago that failed after a couple of years, are still in use, they power a couple of wi-fi security camera and are charged by a couple of 20w panels. Don't use a BMS on them and they don't have one internally but they provide the cameras 24/7 and have for the last 5 years.

Also have spare lifepo4 cells, which have never been charged or used in over 10 years, they still sit at 3.2v and am waiting for them to drop. There is no way you can do any of those things or get that sort of life out of any LA battery, lithium are far superior and in real life, provide much more real usable energy than an LA system double the size. Even when they start to lose capacity, they still provide almost all their energy over 12v, so how can there be an argument saying LA is equal to lithium.

[T1 Terry]

Hi NP. The test is to evaluate the two chemistries and the voltage will be constantly recorded so the point the battery crosses the 11.8v mark under load I'll be marking as "Usable capacity." The rest of the test down to 10v or in the case of the lithium battery, any cell dropping to 2.5v under load, will determine the total capacity using a C20 test as used for AGM battery capacity calculations. Then both batteries will be recharged at the same C rate set by the AGM manufacturer until the charge current drops to what ever the manufacturer uses for their fully charged calculation for the AGM battery. They never fall to zero current, the cell will continue to act as an electrolyser and that uses electrical energy, the recombiner returns this to water so it remains a constant electrical energy use when this point is reached. The lithium will be deemed to have reach fully charged when all 4 cells return to 3.6v or saturation charged. The Junsi graph will show just how quick the voltage climbs once a cell is saturation charged and also show the AGM reaching the 14.4v much earlier yet still having current flowing in to it as it is still recharging. This will help to determine the difference between reaching X voltage and actually fully recharged to 100%. No doubt there will be 101 arguments about just what percentage the SOC is when the upper voltage is reached and the current starts to drop back, it will be very hard to argue with the graph showing what is really happening.
Hopefully it will also bust the myth that lithium batteries can only be discharged to 80% SOC and anything past 100% SOC is immediate death for a lithium battery.
These tests will show the difference in electrical energy required to return each chemistry to a 100% SOC and the difference in time taken.
If the cells weren't so expensive I'd do a repeat discharge on both chemistries to 4v, 1v per cell on the lithium and 0.67v on the AGM and see which looses its capacity first .....

T1 Terry

[native pepper]

G'day Terry, sadly your explanation makes little sense to me, but understand what you are saying. May years ago remember an experiment which went a bit wrong and over night, the 12v 40ah lifepo4 pack discharged to below 2v, each cell registered very small readings and my mate was pretty shocked he had let it happen.

If I remember correctly, it was the same pack used to see what it required for a lifepo4 pack to catch fire and that was attained by drilling through the metal case and a spark from the drill caused the cell to emit smoke which was put out by smothering it, didn't blow up or catch fire. So my mate used that pack for other experiments, including charging it to over 15v, after changing the cell with the hole in it which still registered a voltage but don't remember what it was but below 2v. The pack sat for a few days and then he decided to see if it would recharge, because it had not come back at all.

He put it on the charger with his BMS and the next day it was sitting at 13.8v. Left it for a week or so and it still registered 13.8v, so he started using it as the experimental pack and it still operates today after all the abuse, A friend bought it at the clearing sale and has been using for a couple of years connected to the rest of his house pack, which has the exact same cells and according to him, it still provides 100% capacity. Whether that's relevant for your experiments, don't know but it may give you an idea of what happens when you discharge lifepo4 cells down to almost zero. That pack had been discharged really low twice to my knowledge. Look forward to what you come up with in your tests.

By the way, Lamborghini is using super capacitors in their first hybrid EV, they store the energy from the regen braking and they are claiming the capacitors are 3 times more powerful than the equivalent weight in batteries. My late mate seems to have been right, when saying many years ago, that super capacitors will really make EV's go a long long way. When you add embedded solar cells, could be on a roll.

https://www.drive.com.au/news/lamborghi ... ign=tile-3

[T1 Terry]

The super capacitor pack is actually a smaller Ah capacity than the Prius traction battery. The trick is in the wording,

Instead of lithium-ion batteries the Sian uses super capacitors, which are claimed to be three times more powerful than a battery of the same weight

.
Weight is not volume or area, worth checking out the Ah capacity of a super capacitor v the weight and size, not even in the same postcode, not just the ballpark, for the requirements of todays EV of 400km+ range. This super capacitor pack is used to drive the vehicle during gear changes to flatten out the gaps so it can compete with a pure EV.

At the heart of the Sian's hybrid drivetrain is a more powerful V12 engine capable of making 577kW at 8500rpm. It is coupled to a 25kW electric motor located in the transmission.

The Prius hybrid electric motor produces 76kW and over 200Nm of torque, so a 25kW electric motor that only provides drive during and just after a gear change and a spurt for rapid off the line or overtake manoeuvres hardly rates as even a hybrid.

As far as recovering an LiFeP04 cell from rested above 0v, a recharge at less than 0.5 amp till the cell will hold 3v at rest will recover the cell without building lithium plating spikes that short out the cells.
We have developed a "conditioning" process that stops the dendrite build up forming a spike/bridge that can cause a short circuit between the plates and that is what generally kills a cell, the other sure fire way of killing a cell is dragging it into reverse current flow or holding it at 4.5v for long periods that heat the cell so much all the electrolyte vents.

T1 Terry