Lithium Batteries, who has them?

[cvtripper]

Really good write up, Peter - well done. And thanks to Terry for starting this thread and enlightening us all to this technology.

I've been running 700AH of Li (LiFePO4) with 1200W of solar since July this year.
Also have an Outback 2600VA inverter/110A charger.
I went with 700AH (560AH usable) as we had 480AH of AGM (240AH usable) and 760W of solar in our last van and still struggled some mornings to run the kettle due to the high internal resistance in the AGM batteries dropping below the inverter cutoff if down around 60% SOC.
Weight of 700AH of Li batteries is 92kgs
Weight of 480AH of AGMs was 128kgs!

I designed the electrical power plant in our new van and part of that design was that everything would run off the batteries while free camping (which we do a lot), and it has been working fantastically, but mostly due to the Li batteries.
This has included:

• Electric Kettle
  Coffee maker
  Microwave
  Convection (electric) oven
  TVs
  Laptops
  Waeco 175L fridge
  60L drawer freezer
  Electric hotwater
  6kg washing machine (always use a hot wash)
  etc etc

As long as we run one of the high current appliances at a time (kettle/coffee maker/washing machine while heating) then all runs very nicely - and it is free now the system has been purchased (perhaps should have gone with a bigger inverter? but that is about the biggest you can get on 12V)
So very happy with the technology.

One thing I did do early was decide that the A/C (IBIS 2) was too much load for the batteries as it is typically run for such a long period, and I also assumed the compressor startup current may be a little too much for the inverter as I have heard reports of people having issues starting the IBIS with the 2kVA Honda generators.

How wrong could I be?
Today I finally got around to testing the A/C on the inverter.
The batteries were pretty well full by 10am, so turned on the A/C t give it a try.

The IBIS is pulling 900W/95A DC, and with 65A feed from the solar, it leaves a residual of 30A from the batteries. Should be able to run the A/C for 3-4 hours in the heat of the afternoon and only lose 120AH - still plenty left in 700AH.
This would work fine with a 400AH setup also as you can take these batteries down to 10-20% SOC.
Beats running the generator the whole time the A/C is running, and the IBIS seems to be coping with 40+ degree days that we have been having in north QLD.

Thought this might be of interest to others with IBIS that are considering LiFePO4 batteries.... that don't want to change the A/C also.

Have a look at the attachment - the more observant will notice the battery voltage is still 13.2V even while under this load. This stuff really works, provided you have a means of replacing what you use. Your generator can replace what the solar doesn't, if need be - just get the largest charger you can afford - my 110A charger will pump that in until the batteries are at 98%. With my previous van with AGMs, the charger would wind back from 60A to 30A to 15A from about 70% SOC meaning longer generator run times. Also, they wouldn't have coped with such high charge currents, as Terry has already alluded to earlier in this thread. I have had the solar pumping in 70A then turned the battery charger on and have seen 180A - they just play so nicely together.

[Dot]

Very informative and well written David, even for an old lady..

[generdawg]

Thought this might be of interest to others with IBIS that are considering LiFePO4 batteries.... that don't want to change the A/C also.

Oooh, pick me pick me. Even though the EU20i handles the Ibis with ease, I would like the option of being able to run the a/c reverse cycle on a cold morning or the cooling on a hot night without having to exit outside to connect and/or put the generator away.

...well written David, even for an old lady..

Dave, are you going stand by and let Dot call you an "old lady"?

dawg

[T1 Terry]

Welcome to the forum David, a very informative first post on a normally taboo subject, and as you can see, besides Dottie's old woman reference there have been no other attacks Hope you stick around and show us a few photos of your rig in the "About your rig" section.

The 400Ah Li system we fitted to Gordon & Wendy's (Bugman47) new Evernew caravan ran their Ibis for the full 4 hrs at full load, we had the door open to stop it from cycling just to see if it could do it. When the Victron BMV registered 0% SOC the battery was still at 12.1v under a 95 amp load.

T1 Terry

[cvtripper]

Welcome to the forum David, a very informative first post on a normally taboo subject, and as you can see, besides Dottie's old woman reference there have been no other attacks Hope you stick around and show us a few photos of your rig in the "About your rig" section.

Thank, Terry. I didn't think it was taboo on this forum. Am I about to be banned already??
My wife thinks I carry on like an old woman, so I let that one slip...

The 400Ah Li system we fitted to Gordon & Wendy's (Bugman47) new Evernew caravan ran their Ibis for the full 4 hrs at full load, we had the door open to stop it from cycling just to see if it could do it. When the Victron BMV registered 0% SOC the battery was still at 12.1v under a 95 amp load.

Good to know! I hadn't read any other reports of IBIS usage only inverter A/C, so thought it would be of interest - surprised me too.

I don't think I will flog mine that hard. 700AH would take me 6 hrs to fill it back up... or 4hrs in full sun...
Got to love it!

Oooh, pick me pick me. Even though the EU20i handles the Ibis with ease, I would like the option of being able to run the a/c reverse cycle on a cold morning or the cooling on a hot night without having to exit outside to connect and/or put the generator away.

Quite do-able! An much quieter than running the generator.
I did install a 4kW diesel heater. That is MUCH quieter than the IBIS, uses less electrons and does a better job so that is my preference for the cold. For cooling down though, a quick couple of wires changed in my electrical panel will save me running the cable around.
I'll do a test on heat, if you like and let you know what it draws.

[Izabarack]

Just checked my DIY 40 AH battery at 13.96. Just using solar to pump them up. Should I be trying for 14.4?

Iza

[dapope]

We run a fan heater (2000w) up to 40 mins on full if required, but usually only on the second setting, seems to be enough to get snug. Done a couple of hrs that way. We regularly run both dometic and Coleman on air con and on heat mode. The engine driven air con isnt enough on a warm day, but with a supplemental boost via the rooftop one, we are very comfortable. We also run whatever is needed when we stop for lunch. The induction cooktop is bloody brilliant, just dont have a permenant spot, and the electric jug in the morning is much quicker, the 2200w element sucks about 180 or so amps, and costs about 4% capacity to boil a near full jug. The toasters current draw is usually replaced by the time I have finished eating my toast
Iza, I wouldnt change what you have working, doubt there is much to be gained. JMHO

[T1 Terry]

Just checked my DIY 40 AH battery at 13.96. Just using solar to pump them up. Should I be trying for 14.4?

Iza

What type of battery is it Iza? If it's a flooded cell or AGM battery it needs to be charged to 14.4v, but if it's a lithium battery it will be fine at 13.8v to 13.9v, any higher than that for any longer than 1 hr will damage the cells and reduce the batteries capacity.

T1 Terry

[T1 Terry]

Is the vent a pressure type, ie, will it only vent if the internal pressure builds?
And will it allow gas to come in again when the pressures reverse?

Thinking along the lines of mounting, perhaps the practice of sideways constraint of the cell that has been advocated is a bad thing?
If each cell were allowed to expand and contract due to thermal variance- even when overcharged- then it wouldnt suck oxygen back in when it cooled down again.

again, just musing

The topic of my next post.
Prismatic cells have plastic casings that can withstand 150*C before it lets go under the pressure from the boiling electrolyte inside, the pressure relief valve lets go at ????? but well before the plastic case ruptures. It's a one way valve, but once a of volume of gas at high pressure had blasted through it I doubt it's one way integrity would remain.
The important part to keep in mind, the plastic case becomes pliable when heated, so the pressure will stretch the plastic case in any direction it can and this heating/stretching can occur during extremes in voltage at either end of the charge cycle. If the internal temp exceeds 70*C (not the case temp) the first of the volatile liquids will start to gas and this increases the internal pressure. The plastic is soft enough at this temp to stretch and allow the cases to swell. Holding a cell above 3.45v or below 2.8v for an extended period will cause the internals and particularly the electrolyte to heat up, the further past these extremes the shorter the time damage will start to occur, these extremes are voltage, not current rates in or out of the cell, something many BMS manufacturers and other "knowledgeable" people simply don't understand for some reason or another. Just past these extremes and/or for very short periods reduces the heating period so natural cooling can occur so little or no damage is done.
What does happen is a loss of capacity if the case swells and this links back to something I mentioned in an earlier post, the electrolyte starvation in the cell. If the cases are allowed to swell the active plates are no longer held in contact with the separator material so the electrolyte can drain away to the lowest possible level within the cell. No electrolyte contact between the active plates results in no ion exchange, so now only the area of the plates at the bottom of the cell are in contact with the electrolyte. If that equals only the lower 10% of the cell then you will only get the use of 10% of the cell function. In other words, the 100Ah cell now has only 10Ah of it capacity functioning.
The good news is, return the case to it's original shape with the active plates again in contact with the separator so the electrolyte contacts all the plate surfaces and the capacity returns. Boil the electrolyte so it vents out of pressure relief valve and it's gone. Just like letting the smoke out of electronic equipment, you can't put it back in, when you have lost the electrolyte the cell will no longer function.
How to work with this issue..... that's for another day

T1 Terry

Thought I'd better quote the last entry as it's so far back in this thread, sorry about the gap in updates.
As you probably have seen in a number of the posts that the cells have been packed and held compressed by various methods, this is essential if you want the cells to maintain their capacity. It is also essential to limit the max cell voltages and how long they stay above 3.45v per cell and definitely keep them below 3.6v per cell, they will fail prematurely if you don't. Simply ignore the issue will not make it go away, you just won't know it's happening, so not using a cell voltage monitors system is basically burying your head in the sand and thinking everything will be ok, it won't, but you just won't know about it till the cells start to loose capacity and it's too late then to do anything about it. These are tough buggers, they can be abused for some time before the symptoms become obvious, that doesn't mean they aren't being damaged every time they are over voltage charged but the effects are accumulative and once the damage starts it will snowball if you continue punishing them.
There was a line of thought for quite some time that a cell could be held at 3.6v indefinitely so cell top BMS boards were developed to burn off current via a resistor if the cell went past 3.6v and the charger output was reduced to less than these BMS boards could burn off. The idea was to burn off the capacity from the high cells while charging continued to fill the lower cells, till all cells reached 3.6v. A great theory and it appeared to work well, until cell life started to suffer after 12mth to 2 yrs. As these cells were originally used in electric vehicles this early reduction in capacity was blamed on the punishment they copped in general use so the cell balancing was not considered to be an issue.
When these cells started to be used as house battery storage the severe loads were eliminated, yet the same capacity issues were still apparent. At the same time a group of EV enthusiasts turned away from the high voltage cell balancing method and changed to what is known as bottom balancing, where all the cells are discharged to 0% SOC and then charged with exactly the same number of Ah (coulombs actually but we all know what Ah means) and they found the early reduction in capacity did not occur.
While all this was happening labs around the world were doing cell testing to find the ultimate electrolyte mix. The common finding through all approaches was that over voltage charging heats the electrolyte and this damages the cell resulting in lost capacity. It's a nice feeling when a lab has spent millions of $$ proving what I'd said 3 yrs ago was correct
Anyone who is into this sort of punishment, here is link to a presentation of some of these findings, thankyou very much to Peter James who forwarded me a new link as I'd lost my previous one when the computer turned up it's toes. Here's the You Tube link, get someone to come and check you are still breathing every so often, but it does get interesting after a while, trust me http://www.youtube.com/watch?v=pxP0Cu00sZs

T1 Terry

[Izabarack]

What type of battery is it Iza?

LiFePo Terry. Just playing with a little one before embarking on a serious installation in a RV. ATM, I am using a couple of very old panels and charging is slow enough to keep an eye on things. Thanks for the advice.

Iza