Lithium facts in practice

[nut17]

On the subject of lithium battery technology. Terry is well aware of my recent plunge in this direction, but as time moves on it would appear that a lot of the issues to do with charging and cell balancing are fast becoming a thing of the past.

In April 2012 I replaced a couple of failing original fitment 100amp/hr AGM's with a new AA Solar supplied Lithium Iron Phosphate Yttrium 200amp/hr battery pack and at the same time fitted a "Votronic" battery monitor/computer as this was a requirement to qualify for the 10 year pro rata warranty. 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) The mains charger is a C-Tek M300 marine 25amp unit which is also powered up through a dedicated 600w PSW inverter with the 12v supply coming straight from the Jeep when on the road. (auto switches between caravan 230v supply and inverter)

The battery pack has performed faultlessly and easily copes with up to 125amps being dragged out when making a "Nespresso" coffee. I have yet to witness less than 12.8v at the battery even under excessive load and at 20% capacity remaining.

With the Jeep running and good sunshine I can often observe up to 45amps of charge going into the battery and this continues right up until the battery is full - no tapering off of charge rates as the battery nears full charge.

The whole exercise was fairly hefty in the dollar department but with a 10 year warranty and possibly 15 year usable life the overall initial costing becomes more realistic.

The battery pack has never got above ambient room temperature and the individual cell voltages are still within 0.1v which is actually an improvement on when they were installed.

So if your existing batteries are on the way out, give the option of embracing some brilliant new technology some serious thought. Every time we take the van out the battery performance never ceases to amaze me



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Cheers Chris

Whoops - Admin may wish to move this post to "Low Voltage Electrical" I am a slow learner
[EDIT: Admin has moved your post & changed the title to clarify subject of post]

Thanks Admin

[Craig]

Thanks Chris,

Can you tell us exactly what the hefty cost is?

Craig

[nut17]

Hi Craig - This http://www.aasolar.co.nz/AA%20Solar%20L ... eries.html site will supply a lot of the info. My battery pack was $NZ1994 and the Votronic BMS was $NZ269. This price needs to be compared with two lots of 400 amp hrs of AGM batteries due to the voltage drop and shortened life span of taking AGM's below 50% state of charge and a maximum expected life span of five years (I wish ) After 15 months mine were stuffed!

Cheers Chris

[T1 Terry]

Hi Chris, was the roughly NZ$2000 a fitted price including the BMS or battery only? Does the system have individual cell voltage monitoring? I'm just trying to work out how you know what the cell voltages are because I can't see any cell Logger wiring on the Sinopoly cells. A nice touch putting AA solar stickers over the Sinopoly logo but advertising is advertising
Just trying to do a rough comparison cost to using Winston cells and DIY. 4 cells required $1.40/Ah per cell - 200Ah = $1120. Cell logger and wiring, $30, strapping, $50, all up AU$1200 plus freight. What does AU $1200 equal in NZ $$ ?
The battery monitor is a seperate thing, either a Victron, Xantrex our one incorperated with a PL20 or Dingo, all similar $$, as a stand along monitor the Victron would be the winner I'd reckon but the combination of either the PL20 or Dingo and a shunt kit make them the better value for money, but only if you need a new regulator.

T1 Terry

[nut17]

Hi Terry, the battery was $NZ1994 and the BMS was $NZ 269 (c/w 200 amp shunt) There is no individual cell logging built into this system. I have been regularly manually checking the individual cells with a digital multimeter to confirm that an individual cell logger was not necessary. I have had the battery down to 20% SOC on a few occasions but it normally seldom gets below 70% and when charged with no load in or out there is only 0.1v variance - always the same cell.

Cheers Chris

[T1 Terry]

As you recharge at very high voltages for lithium batteries I would recommend spending the $30 and fitting a cell logger so it can give you a warning alarm if a cell goes over 3.6v, they will be damaged if over charged.

T1 Terry

[nut17]

Hi Terry, I really have to be guided by the outfit where I purchased my battery who are now supplying these batteries in quite large numbers to "off grid" homes running wind and solar in remote areas. I have had a temperature sensor from a weather station attached to the pack, but there is absolutely no heat being generated at all. The battery remains at ambient room temperature at all times. When fully charged, the current reduces right down to about 700ma and I assume my Votronic BMS is controlling this feature. I took the van back to AA Solar in late September when we were visiting Auckland and got them to double check my systems and they were relaxed that all was operating as it should.

However if a cell logger can obtained for $30 it would give me some piece of mind. Can you tell me where I can purchase one of these devices?

Cheers Chris

[Chuck]

Wow! Now I'm really interested.

With the Winnie sold & now reverted to another caravan - Crusader Manhattan - at a hefty 3 ton & a ball weight of 300kg I'm seriously looking at reducing that front end weight which isn't helped by the placement of 2 x 120 AH batteries in there.

What would be the weight difference/saving between these two types of batteries... assuming this magic new system is of equal or greater capacity than what I currently have with 2 x 120w panels on the roof?

Ooohh... getting a little excited here!!

Chuck

[T1 Terry]

What would be the weight difference/saving between these two types of batteries... assuming this magic new system is of equal or greater capacity than what I currently have

This one is a tricky one, first you have to determine what you actually have at the moment compared to what you think you have, then compare that to the newer batteries and their weight. This is based only on weight saving and attemptin to compare apples with apples.
An attempt to explain. Currently there are 2 x 120Ah batteries fitted, they are charged by solar so roughly 90% recharged at best. There is an accepted 50% capacity that can be used before the cycle life starts to shorten serioisly but more importantly, before the voltage drops below useable. Minimum useable voltage at the terminals is around 12v, the load throgh the cables will drop this down to 11.8v or lower, the fridge stops working at about this level, the sound goes on the tele and the diesel heater doesn't want to fire up.
12v on an AGM = 50% state of charge of a good battery, only 90% state of charge on average is reached when solar only charging from this 50% state of charge level so this gives us 40% of the advertised capacity as the useable amount.
120 x 2 x 40% = 96Ah, 100Ah for round figures.
A lithium ferrous battery can be used down to 100% of it's capacity or 0% state of charge and still have 12v at the terminals. so if we are comparing useable capacity, a 100Ah lithium ferrous battery will replace 240Ah of AGM, sounds rediculous but am I wrong with the numbers?
!00Ah of lithium ferrous battery weighs 14kg, 240Ah of AGM weighs 75kg approx, roughly a 60kg weight saving.
you won't get the 7 to 15 yrs life if you drag the lithium ferrous batteries down to 100% every day but then how often do you drag the AGM's down to 50% SOC? Even if you did drag them down to 100% discharged every day they still claim 1,000 cycles, that's 3 yrs.

T1 Terry

[John M]

Hi Terry,
There is one factor that I am still not sure of, I no that there are various types of Lithium batteries, and they all have different capabilities, but during my working life I used, and was rapidly disillusioned with portable power tools largely because of the battery life, I am yet to meet anyone who is getting much more than 5 years out of even the best batteries, granted these batteries get thoroughly abused, that is run dead flat and then fast charged before running them right down again, they are then put away and then often flat or semi flat when you go to use them again.
Watching a show on electric cars (Nissan) the other night and they state that the life of the batteries is eight to ten years provided the batteries are never discharged beyond 50% and if they are continually discharged below this mark the life expectancy will be as low as three years or even less, and if they are fully discharged they require a minimum of 14 hours charge time.
I know a lot of taxis have gone to the Prious (I believe because of smart advertising and possibly a deal with Toyota) and the majority that I have talked to 12 months or more down the track have said never again, the batteries don't last "five minutes" and a number of other complaints, nearly all related to the electric/ battery operation.
I don't believe that they have the battery charging/ discharge regimes correct as yet, if that is the case with large companies such as Toyota and Nissan cant get it right what are the problems yet to be encountered.
I know there a a number of people that are experimenting with these batteries, when coupled to solar charging and I have no doubt that they work, I know that the weight saving is quite dramatic and all weight saved is fuel in the tank, but all this still leaves me wondering about the life span, the real life not the advertising blurb, I know that Lithium Ion as in power tools are good they continue giving full power up until they are dead flat, and then they are able to be charged relatively quickly, but on larger banks how much time is required to fully charge the batteries?
I know on my own solar system, my current batteries, 4 x 100 ah full river, with 460 w of solar through an MPPT regulator seems incapable of charging my batteries much beyond 98% (by the Xantrex meter), not because the power isn't there but because the batteries seem incapable of absorbing the charge in the time. The solar supplies the fridges etc but by mid afternoon the charge rate is down to 3A and the voltage around 13.4, if I plug the charger in the batteries will come to full charge overnight, (I think around 3-4 hours of trickle after dark) I am thinking that my batteries need more than the 9 hours of daylight they are currently getting,(where I am parked I get shaded from 3 pm) so how would other batteries that require 14 hours to fully charge?