Lithium facts in practice

[T1 Terry]

Even I am impressed with you two boys

hope there is no intimate meetings planned

Peter still owes me that beer after the cease fire before the last cease fire.. or was it the one before that No body would come to see the action if we got too friendly, I think our "disagreements' were the fire that kept the CF running, it sure got quite when they banned us
Back to the original program not the arguing, the lithium discussion

T1 Terry

[dapope]

Getting prices Wahoo!!!

[John M]

Thanks Terry and Chris that has dispelled a number of doubts I had, thanks for taking the time to explain in simple language. I am not in the market for batteries at the moment but will continue to watch with interest.

[T1 Terry]

I can't see any point in replacing batteries that are still operational, unless it's a weight or size issue if you need to increase capacity. Like any battery, they have their issues, as long as you understand what those issues are and build a system that keeps the issues in check they are a great choice for batteries, but ignore the issues and they will bit you in the back pocket.

T1 Terry

[PeterM]

My charging regime is not much different to what was being used on the AGM's, with the bulk charge function being boosted to 14.6v on my Blue Sky SB2000E 25 amp MPPT solar controller (330w panels on roof)

Thanks Terry for clarifying discharge capabilities and issues for LiFePO4 batteries. It appears that 12 V are less of a problem than 24 V, especially for cell imbalance - half the number of cells! It also seems that a simple battery disconnector that can be set at 11.8 V such as was available from Jaycar would be a wise addition.
What further comment do you have about nut17's charge regime? 14.6 V seems too high and may lead to failure? If not a problem, then even my solar and mains chargers would be useable without adjustment.

[oldtrack123]

Always made sense to me! you can only get so much in the glass, and you can empty it as fast or slow as you like!!
House settled today. Battery shopping coming up when I find trev's email address

Hi
I think T1 makes the points out that while you can over fill a glass without damage,the overflow will just run over the sides ,some batteries[some more than others] react differently & can be permanently damaged

Also when the glass is empty ,it is empty.

But ALL battery cells in any series set up do not stay empty , they start being charged in the reverse direction.if not closely monitored

This is actually a reason for failure of many rechargeable Nicads etcs
Not good for ANY CELL of any type to be reverse charged

As Terry has rightly pointed out the relatively flat voltage curve of Lipofe's does require care to not commit either sin ,since the actual sudden changes in voltage are at either extremity

CELL monitoring & alarms are essential with LiPo4,I believe, in both Terry's & my opinion

Certainly that has always been mine

I do agree with Terry that if you have a good CELL monitoring & alarm system [audible] cell balancing systems are not require, as you can manually balance if needed'


Peter

[T1 Terry]

Hi Peter M,
The cell logger I mentioned earlier has an alarm port that can be used to switch a relay. The logger has alarm settings for high cell voltage and low cell voltage as well as pack voltage and differential between cells so this alarm can switch off the charging via a relay if a cell voltage goes over 3.6v or a load greater than the charging voltage, linked to a timer circuit you can heat the shower water with the excess solar for instance. The low cell voltage of 2.8v could be used to turn all loads off, or start a generator or just an alarm, lots of options. The down side is the alarm port will switch on any point, so a low cell voltage turning the solar off is not a desirable thing, nor is a high cell voltage turning the load off, so if both functions are required 2 loggers would be needed.
A better way around the low voltage is to use a good battery monitor. Both the Victron battery monitor and the Plasmatronics controllers have an alarm switching facility that can be set to state of charge (SOC), setting this to say 20% SOC and linking it to a relay to shut down non essential items saves what's left in the battery for the fridge and emergency lighting
It’s all a case of making a system that suits the application, not a one size fits all, everyone has a different way of using their batteries, some seem to carry them as pets, others flog an undersize pack to death, some simply abuse their batteries through lack of understanding. This is why I set up the private forum, I think the owner builder learning as they go far better understands their system when it’s finished, it suits their use patterns and if anything need attention they know just where to parts are, what connected to where and can follow the basic flow chart to fault find if required. A much more robust and reliable system if you can fix it yourself or even fix it before it’s broken.

T1 Terry

[nut17]

Have been playing with the settings on my Votronic battery computer and have adjusted the warning/ current shut off point up to 25% state of charge. It had been set up by AA Solar at 0%. This should effectively prevent any of the cells getting down to zero. It is also set to cut charge current when the battery reaches 100% or 200 Amp/hrs. The monitor is mounted in a prominent position, just above the sink bench and provides a great talking point and is in constant view from the living area of the van.

Cheers Chris

[T1 Terry]

When the cell logger is fitted the graph charts it can generate via the computer will be interesting to see. Now I understand why the current suddenly drops to zero, they are using the not 100% full and not 100% empty to reduce the risks of cell damage at either end of the cycle. It will be interesting to see if it matches up with 4 fully charged cells at 3.5v. It may well be yet another alternative method of battery management that works well enough to protect the cells from either voltage extremes, i still think the cell logger is a nice safety back up though.

T1 Terry

[BruceS]

Peter I think it might be a good idea if you started this on a new thread so we can make sure it stays on topic & relevent to your install/progress.
If you'd like to do that let us know & we can split it off.
It's important that anyone who gives you information is totally aware of your present install, your useage pattern and your desired end results. Perhaps an idea of your 'budget' as well?


See topic under new heading