Lithium Batteries, who has them?

[generdawg]

...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.

This is way beyond me as all I know about electricity is AC/DC, AM/FM and battery to ground*. This water is too deep for me to swim in, but I am rooly interested and realise the benefits of solar powered lithium.

* even that has caused me problems with the Fiat non earthed inline lighting wiring! Aaarrrgh

[cvtripper]

Further to my testing of the AC on my Li batteries, I tested the system on the AC heat setting yesterday with similar results to when it is on cooling, so all good for heat if you have the battery and inverter capacity.

I saw 128A DC flash momentarily during compressor startup, so 128 x 12 = 1500W.
While running with the compressor kicked in, 95A = 1140W (although my Outback meter showed 900W)
When the compressor kicks out when temp is reached, only about 3A DC is being drawn, which is trivial.
You can get longer out of your AC while on batteries if you turn the temp up to say 25C so the temp is reached easier and the compressor kicks out - personally, I like 20C

So, I imagine a good quality 1800W inverter would be an adequate size.

Just watch your battery capacity - part of a good quality BMS that Terry has already discussed to monitor cell voltages is one that counts amps in and out of your battery.
I suggest it is mandatory with Li batteries and will let you know how much you have used and replaced.
Take care not to run the AC too long (watch the meter) if you do not have large batteries.

PS I would not even attempt this with AGM unless you have very large capacity and using an inverter AC.

[T1 Terry]

Part of the push for me to develop a better understanding of Li batteries and if they could be used for house batteries, then all the rest of the learning curve, was a desire to run the split system air con in big bus. I had 28 x 100Ah AGM batteries with a total of 3kW of solar recharging them, the inverter was drawing 100 amps so the math says I should get 14 hrs air con run and still stay above the 50% SOC as the C20 discharge rate of 5 amps per 100Ah meant I should be able to draw off 140amp constant and still get the 50 Ah per 100Ah capacity... I got less than 8 hrs before the inverter dropped out due to low voltage and the current draw was over 120 amps due to the reduced voltage available. It then took 3 days before the AGM batteries stopped accepting charge meaning they were again as close to 100% charged as they were going to get. The air con was never going to be an option with lead acid batteries so the search for a viable alternative started, well over 6 yrs ago now, that's how long I've been researching these batteries and over 3 1/2 yrs hands on with my house system and Brian's (Homeless) bus system as the first of many.

T1 Terry

[slowhand]

...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.

This is way beyond me as all I know about electricity is AC/DC, AM/FM and battery to ground*. This water is too deep for me to swim in, but I am rooly interested and realise the benefits of solar powered lithium.

* even that has caused me problems with the Fiat non earthed inline lighting wiring! Aaarrrgh

Understand how you feel, felt like that for years with my kids, but if they use plain english and not technical jargon then lifepo4 and low voltage is easy to understand. Can't work out why some use all this jargon to those who have no knowledge of it, doesn't really help them at all and there is no need, as there are simple explanations. Most only want to be able to work out what's happening and fix it and for that, you certainly don't need to know all the techo stuff.

I've been playing with lifepo4 for over a year now and my kids for at least 6-7 years, they now use plain english when talking to me and it's given me the ability to understand and be able to fix just about any problems these things throw at me.

The biggest problem with them is balancing and getting even charge and discharge into them. Been playing with a great BMS, but it still doesn't do what I want and what lifepo4 needs and there is no BMS/charge system around that does the job properly.

For some reason manufacturers and also those who work with them, are still stuck in LA land, even though they claim they aren't. The charge and control systems they use all revolve around LA theory and not what's required. My kids say it's because the aim is profit growth and not good controls, I understand that, but not the technical reasons, which are way beyond me.

I've got a 640ah pack which I'm using to play with and run my house, using different BMS and BVM setups and now believe I know what is really needed to control the system. But there is nothing around which is capable of doing it and everything is orientated to LA technology and not lifepo4. Just purchased another 1000ah and will put them on the house and the 640ah on my bus, then electrical life will be easy to cope with and no bills. Will get my money back within a couple of years with saved costs.

If I had the expertise would make a BMS myself, but that's way beyond me by light years and my kids are to busy to make it. When asked my daughter to design a schematic for what I want, she just laughs and says next year as she is to busy. They have their own BMS, but it's sealed and for domestic use so customers don't fiddle with it, because of that, it does have a redundancy built as it's not user adjustable.

All those who are waiting for drop in lifepo4, which are already available, but in Aus are ridiculously expensive. Must realise all current control systems have built in redundancy in them, which means you will be lucky to get 5-7 years from them which is the norm for most things of an electrical nature.

Otherwise producers would not be able to maintain their profit growth without redundancy. But a well set up and balanced system, will last 15-20 years and that can only be achieved by having a BMS which charges, balances and controls each individual cell line and not the current pack charging which is destroying people lifepo4 cells slowly currently.

Charging the pack and not cell lines, creates many problems, especially when it comes to high cell voltage limits. I watched two test cell packs over 5-6 years, one balanced and the other unbalanced, the unbalanced has already had cells replaced, whilst the balanced system hasn't missed a beat and both are used to run the same office complex.

You don't have too have a degree in electronics, just enough info to be able to understand what's happening and what to do. There are many forums and sites which use plain english to explain electronics and lifepo4, search for them and you will find it won't be long before you have enough knowledge to understand and use lifepo4 as you'd use LA, just in a better safer way.

[Busman]

STORAGE
We have 2 sets of Liths.
We purchased 8 x 100 Ah cells quite some time ago when the hysteria was at its peak, to see what all the fuss was about, and to find out if these things were as good as some claimed. Certainly got a positive answer to that one.
We also wanted to see if any re-arrangement of the battery area would be possible.
Original plan was 1200 Ah of La's to give us 600 Ah useable capacity, enough to run a small aircon all night if needed. This would have weighed 1.25 tonnes so the interior was designed around that figure, in one of the rear bins.

Investigation revealed they were pretty good so the LA plan was abandonded, and eventually 800 Ah purchased of Liths. This house bank is 24 Volts and runs 8 x 100 Ah cells in series for each of the 8 cells in the ban (64 in total)
The 8 x 100 Ah initial purchase (different brand) were reconfigured into 4 cells to give us 200 Ah at 12 Volt to run all the 12 V stuff.

REGENERATION
We are able to massively charge these batteries when required.
The system consists of 2000 watts of solar panels (10 x 200 W) on the roof which gives us up to 70 amps at a time (probably a little higher in perfect conditions)
and 2 DC-DC switches controlled by the control system (see below) each of which can add another 70 amps to the flow from VP's 240 amp, 24 V alternator.
So you can see we have the capacity to charge at over 200 amps if required,

CONTROL
We are using a Rich Electric Super Combi and its satellites which are interconnected with data cables. These are:

Super Combi: Charger (up to 70 amps, up to 50 deg C) from mains and a 3000/6000 watt inverter which will run both small aircons at once. 3 programmable relays, one of which we use to run some fans forcing air though our black and grey tanks and exhausting on the roof. Time and voltage programmable.

Sunstar Solar Regulator: 2 x 60 amp ones as you can't get the 45 amp ones any more. Controlled by the SC

DC/DC switches. 2 of these are used as charging sources from the coach alternator. If switched on they will add to the Sunstar input (if coach motor is running) In reality they are there for a rainy day! So far the solar is more than enough, but it is nice to know there is the option if the sun don't shine ! An adjustable voltage regulator for the cranks has been fitted as well.

DC/DC Switches: 2 x used as load controllers.

1 The eutectic fridge/freezer in the bins is controlled by one of the load switches. They have a timer function so basically from the time the solar starts inputting the FF has power (24V) available to pull the eutectic plates down to minus 22 deg C. We run the fridge part quite low, though with a planned change it will probably all become freezer down the track.

2 The hot water system. We have fitted a 50 ltr domestic hot water system which has a 240 V element in it, although before going this way we had set up a chamber with 3 x 400 watt 24 V elements and a 24 V hot water circulation pump. The second load switch has 2 time periods operation to switch on the LV elements, it gets 1/2 an hour just before peak sun time and 1/4 just after, this allows the batteries to top up in between, though with the sun we have been having lately, even with hot water heating there is still charge going to the batteries. The hot water system is also used as a dump load when required.

After quite some time learning the system (there are over 400 constants you can set) and organising some software to "talk" to the SC via PC we have gained a pretty good understanding of the system and these batteries.

One thing we have found is the charging rate at the high end of the charge cycle, affects cell balance dramatically, but if you limit what voltage you charge to by a little bit, all of those hassles are avoided. We generally sit on 27.4 V which gives us more than enough capacity.
If we want more capacity we will use cells chargers for each cell until battery is within 20 Mv and then increase the charging voltage to 28. gives a bit more capacity, in reality, go for a little less and they will sit there at about 22Mv difference (which is something like 00000000000000001 % and they will accept whatever you throw at them.

We are pretty happy with the purchase !

Not happy that VP is in Brissie getting a new crankshaft oil seal and clutch, feel like I have lost something !!
Oh well she should be back tomorrow, couple of changes to make, go and do some shopping and sayonara
William

[Craig]

Hi William,

how did you come up with a figure of 1.25 tonnes for 1200ah of LA batteries? My 100 ah batteries weigh around 30kg each.

[BernieQ2]

at a guess fork lift battery's maybe?
Bernie.

[Busman]

Oops seems an over calculation.
I was going to use Electus's Sleek AGM's 150 Ah weighs 52 Kg times 8 = 416 times 2 for 24 v = 832 Kg

Dunno where I got the 1250 Kg from ?

Oh well, still happy with the Liths !!

[T1 Terry]

This post will put me at logger heads with the on cell board type BMS battery balancing sellers, but sometimes the facts will be disputed purely on $$ grounds. I’m willing to stand corrected if anyone can come up with validated proof I’m wrong.
There is trend towards the belief Li cells can be float charged at 3.6v to 3.8v, but this is not correct, the cells will be damaged if you do. This is a quoted post from an admin member of the Australian Electric Vehicle Association forum. These guys eat and sleep this stuff and the combined qualifications of these guys would make your head spin, you can read more from where it came from here Upgrade to Lithiums? -The Australian Electric Vehicle Asn - Page 2

Quote:
I once used a 0.35A LED constant current power supply to balance out a set of 16 90Ah cells, all with BMS modules on them that shunted at 3.65v
I left it on over a weekend

after the weekend, all cells were 3.65v, all bulged, all lost capacity, all had higher internal resistance.
please don't float them. [If] you already have a single cell charger - just leave it attached to the lowest cell until it is full, then move to the next one……..


A short burst to 3.6v will not harm the cells, holding them at 3.6v or higher will wreck them. A short burst means stop charging when the cell reaches 3.6v until the cell voltage drops below 3.4v, then resume charging and repeat the cycle as often as required to reach the 14v or 14.2v for faster charging max battery voltage. Once a mth manual equalising if you must to reset the 100%SOC, but stay under the 3.62v mark as your max. individual cell voltage, cell cycle life depends on it.
No doubt this will be widely disputed by those who sell BMS systems that rely on floating the high cells with a resistor burning off current while trickle charging at the resistors discharge capacity while waiting for the other cells to reach the same voltage. If you want to gamble that I don't know what I'm talking about after over 1,000 cycles of house battery experience it's up to you, they are your $$ not mine.

T1 Terry

[slowhand]

Terry, I agree with you, looked at one or two BMS that float, seen many charge controllers claiming to be for lifepo4 also have float settings, very bad advice and approach.

I'm looking at a solar charge controller that's programmable and another version with a 240v 3kva inverter, being able to adjust the upper and lower voltage parameters for off/on charge and load, means it may suit lifepo4. They are checking to see if it is linux compatible, which would be the only hassle. Then again China is switching away from microsoft and apple using open source systems. That's another interesting happening.

A proper BMS reaches a pack voltage and switches off charge completely. Cell balances would be working during charging to reduce any cell which has gone over the upper cell voltage parameter and bring it back to the right voltage. Which means with a good BMS, when reaching peak pack voltages, all the cells will be very close to balanced. The only balancer that would be working, would be if a cell was over voltage.

A better BMS, would take charge from a high cell line to a low one, that should be the next step in BMS development in my view. When all cells are at or below their voltage, balancers only provide cell voltages to the BMS which switches charge back on when pack voltage drops to 80% SOC. Same with load, it switches back on at 80% SOD, or whatever you program in for your load and charge parameters.