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LTO for SailBoat
#11
Thank you completelycharged.

The boat is now nearly 15 years old so, I'm upgrading the electrical system in advance of the batteries. This will be Victron gear (when it gets here!). It is a little pricey but seems purpose built for marine and gives me a little more flexibility when I'm learning. (And an old guy can write off just about any amount on his beloved boat).

The Victron charger has a number of profiles including for lithium, which can be customized. There is a max voltage of 16V (12V system) so I'm hoping I can tweak their LiFePO4 profile up to this to run the 6s LTO ( ie 2.67 which seems pretty close to full). I'm pretty sure the desulphate / equalize function on my current charger is north of 16V (they do whizz a little faster) so I'm relatively confident all the loads can handle the likely voltages.

I'm keeping lead acid for the start battery. The boat is in Thailand and this is both the readily available battery technology now and well into the future. The house (LTO) bank can have a problem , but the main engine needs to be able to be sorted locally and fast if there is ever an issue. And the cost of one of these starter batteries every 4-5 years is not consequential.

The Victron 12/200 BMS deals withlead acid start battery combined with lithium house. It charges the lead acid first , then the lithium and can self regulate how much charge is taking from the alternator . The alternator is 100 or 120 A.. and my other research told me that lithium could suck all that in and more so needed some kind of limiter to the standard alternator / regulator to avoid overheating.

Most of the nooks and crannies in the boat are already jammed full of stuff! So these batteries have to fit in the old battery bay. More and more I'm doing things in a way that should help make the boat more saleable down the track. For the right buyer , lifelong batteries and night time silent air con in the tropics should be a great feature.. and if they dont want to pay a premium I will simply pull the LTO out, drop in lead acid, and recycle the LTOs to an ESS somewhere.

I've been trying to figure out what's wrong with these batteries from the start.. they seemed too good to be true. This supply hiccup may indicate problem number 1. You're dependent on one supplier (YinLong) who can yank the supply(from the resellers) at any time. Kylin , who seem to have great customer service , jumped from 17.50 -> 30.00 in about 10 days. I'm really hoping this supply gap/price rise is as a result bunch of Americans buying in ahead of 25% tariffs in January rather than something else more structural. We will see.
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#12
Alternators regulate the upper current based on the engine rpm so just avoid running the engine at high rpm when charging or take the alternator 12V coil feed wire and switch it separately so you can then keep the alternator turned off if needed.

I would wire the LTO to the starter and keep the existing battery on float in that case and the reason being was from what difference I saw. Granted I only had a 20hp twin V but that was starting a lot better than the 65Ah lead acid with just 2x6s packs connected, I had an extra pack for capacity to run some computers on the vehicle while it was not moving. I had the starter running (on and off) for the equivalent of over a minute while I was sorting out getting the engine running again. Started up, 55A charge back into the cells. The voltage drop with the starter also knocked the computers out with the lead-acid as the voltage fell too far, but not with the LTO.

With LTO it would be ideal to replace part of the keel balast in a boat but for existing boats near on impossible ! I was thinking more along the lines of shaping the cells to match the shape of the hull so that they could fit each side or along the bottom and only add one cell width to the space used.

I'm surprised that at the momemtn YinLong are not doing what the vehicle manufacturers are doing and recyling their own cells into home or commercial powerwalls. That situation may change but the cell will still end up on the market, just like relatively new Tesla batery packs from crashed cars.

If I had a supplier who quoted 17.50 one week and then quoted 30.00 the next I would not necessarily call that great customer service, depends on their real reasoning for the hike.... special pricing just for you or market wide ?
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#13
Believe the pricing is market wide.. I hit them all and got nothing under $28.. and of course they then make up that in the freight anyway.

Rev 2 for the battery packs.. Will stick with aluminium (aluminum) bus bars to match the pole material.  Needed to beef them up.. essentially anything serial has to take up to 400A.  The load is fused at 300 so battery internals should withstand that and more.  May power (inverter load) should be 200A (per battery.  There will be two batteries.. and I plan to add a 225-250A circuit breaker to one to handle situation if I've run one and accidentally switch them in parallel ie different SOC.

For first build I wont be fusing cells.  Is this necessary in a 5P? I assume if one cell internally shorts it can only take current from the adjacent parallel cells so in this case 4 other cells for a total of 40 * 2.3approx 370W.. if near fully charged.  Interesting in the alternative LiFEPO4 4s54P is would be 53*3*6 W to dump into a shorted cel ie 1017 W ie 3 x the power into a volumetric mass 1/10 the size (32650/66160).

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#14
Add a breaker on each battery pack if your hoping to be at sea and have a cell issue, that way you can switch/trip out either battery pack. Plus, there may be a time when you want to discharge half the pack or keep half a pack fully charged as a reserve.

If an LTO cell in your configuration shorted and was capable of actually holding an internal short (which they are not) then the short circuit current per cell is around 800-1200A depending on the internal resistance age so you would see around 4,000A trying to short into the cell at somewhere around 1.5V, so about 6kW. This would melt the aluminium rather quickly. There is a video of someone with a clamp meter and shorting a cell with welding cables on youtube. The current and power capabilities of the cells is a lot lot higher than you have in your calculation.
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#15
I saw some Toshiba 2.4V 20AH lto for $14 usd piece
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#16
(11-26-2018, 10:55 PM)Jason Morris Wrote: I saw some Toshiba 2.4V 20AH lto for $14 usd piece

Where did you see them ,Jason?
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#17
(11-26-2018, 09:15 PM)completelycharged Wrote: Add a breaker on each battery pack if your hoping to be at sea and have a cell issue, that way you can switch/trip out either battery pack. Plus, there may be a time when you want to discharge half the pack or keep half a pack fully charged as a reserve.

If an LTO cell in your configuration shorted and was capable of actually holding an internal short (which they are not) then the short circuit current per cell is around 800-1200A depending on the internal resistance age so you would see around 4,000A trying to short into the cell at somewhere around 1.5V, so about 6kW. This would melt the aluminium rather quickly. There is a video of someone with a clamp meter and shorting a cell with welding cables on youtube. The current and power capabilities of the cells is a lot lot higher than you have in your calculation.

Thanks CC.. I've just received the cells and inverter/charger and getting the busbars machined so should be able to get set up in test in the next few weeks.  I intend to run with just QNBBN equalizers to start as this seemed to be the most effective in the 5 unit test.  The inverter charger has a max charge of 16V so with the equalizers on it should hold things together , at least into the medlum term. 

My plan now is to randomly assemble the parallel packs ie not try to pre measure for capacity .. the logic being that they should randomly total out at 5 x 40 = 200A per parallel.  As there will be 2 banks.. I will strip one down alternatively every 2-3 months , let sit for a bit.. and measure the parasitic loses on each cell to see if there are any duds.

Believe the equalizers are rated to at least 30000 hours.  At this stage I will simply wholesale replace them every 4-5 years.

In that time I will give some thought the BMS I really want.  For such long life cells I suspect something different is needed to current off shelf and Batrium seems like overkill. My guess is shunts in the balance lines and tracking the balancing current might be the trick..   Failure to balance (eg equalizer failure) or changes in relatively amount of balancing (indicating possible cell failure ) seems to make most sense.  Also a need to alert externally and maybe some kind of proof-of-life feature is needed remotely eg a routine on a Linux server pinging the BMS every month or so to confirm it is functionally , seems to make most sense to me where I'm at now.

I will be fitting breakers to each battery.  For the reason you suggest and also in case I inadvertently connect them in parallel and they are are wildly different SOC.
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#18
Before assembling the packs, connect all the cells together and leave them for a few hours to balance out. If your cells are anything like a typical delivery they will be in a few different voltage groups from whatever state of charge they were at before they were taken out of whatever it is they came from. If the voltages are greater than around 0.5V difference you may want to ease the balancing current or have some rather warm cells and wires....

Having seen some test data I did not bother measuring before assembling packs and have been running my cells for 6mth now without a BMS at all and they are still very close (cell to cell voltage) to when they were put in. The QNBBN units should last a long, long while and you only need them connected once per week for a few hours..... the more they work the more you have something wrong in your system. Some form of over/under charge protection is a must. My over charge protection is in the MPPT charge controllers and under charge is the inverter cut-off. Again no separate all in one BMS style.

Batrium is good for some as it provides a lot of information, pricing in my view, it is very expensive for what it does for the specs if you have a high series cell count which you get with LTO on 48V. That's my opinion and will probably get flamed for it.

The breakers are must in my mind, I have seen and caused enough shorts in my life and dare to imagine some of them without fusing to reduce the peak current before the weakes point vapourises, melts and burns a hole through the bottom of the boat....
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#19
So put the first of 2 batteries together 6s5p this evening. The engineering shop did a good job on the busbars (4mm Al) so all fitted quite nicely.

Made up all the 5p packs but connected them in || overnight to equalize per CC suggestion.

The only issue here where the aluminium nuts. I'd bought in 150 from China. I stuffed up my first 5P assembly by 'forcing' with a wrench the nut.. it burred into the cell pole.. ugg. After this I finger tightened all of them first. those that would not finger tighten into the sin bin. I had one 'golden' black carbon nut and was able to verify that not a single Yinlong cell (out of 60) had a problem on the thread... ie very clean. All the problems were with the nuts with 22 failing..on the way to geting the 120 I needed: they probably can be easily cleaned up ... but you really have to be super careful working with aluminium! (Spelling is Australian).

After the first 5P disaster, the next 11 x 5Ps went fine (after applying the finger tighten test to the nuts) so lesson learned. Tomorrow I'll sort out that dud 5p and || the second pack.. any suggestions for getting these frozen Al nuts off?

Inspected the new inverter.. looks like its been banged a bit in transit.. .fingers crossed. it will work.. that test likely in about 2 days.

Have to say I'm pretty pleased with the bus bars.. put a lot of effort into the design of those and it paid off - assembly was remarkably easy and each 5P group seems quite robust. One issue.. lock washers.. Based on the compatibility issues alerted by Jim Jr I've been trying to keep everything Al to match the cell poles. So busbars and nuts are also Al. The metal is so soft (kind of locking the nut) that I have no problems with testing and even some production use as is.. but there is some vibration when sailing.. For the life of me I have not found Al lock washers anywhere... does anyone know a source? I could double up on nuts (but thats about USD60 landed.. which is a bit there).. or even dab a little loctite in the end.. I dont want to revert to stainless ones (which seem to be everywhere) as I'm all to well aware of the galvanic issues that will create.

I may not fit the equalizers for a while .based on CCs recently and Jim Jr some time earlier.. I will be all over the cells for a while constantly checking and learning.. ..

As for high / low voltage protection. . For high side the inverter /charger max is 16V. I figure one of the advantages of the 6S config is that 16 / 6 is 2.66 V.. just a tad (0.04) under full charge for these LTO.. I'm hoping that's close to perfect (esp when they are balanced). For the low the inverter has some adjustable shutdown settings and I will likely set this to 12v. I believe in the box of stuff I ordered there is a Victron Battery protect device which can also de-coulple at a selected voltage.. so this will ultimately be what I will use.

I need to give some more thought to comments of the weekly or monthly need for balancing ie only connect equalizers then... this kind of adds complexity to the balance wiring (ie switching somehow)..... I have solar panels that are and can can be connected even when away form the boat.. (about 900W). I assume the problem with leaving the equalizers connected all the time is that they chase parasitic loses around the pack until they flatten it. I reckon if I leave the solar always connected (as it is now for the lead acid) , and have the equalizers connected this should become a non problem. Comments on this logic welcome.
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#20
Here's the first battery (12V 6s5p) in the flesh...


I'll recant on my earlier favourable busbar comment.. when I tried to put the heavy duty joiners in .. they did not fit.. the holes in all these 5p end plates were not quite centred.. will have to go back and enlarge holes in joiners to accommodate and work with the machinist on accuracy !

Separately.. went back and tested the first 5 cells after a month of sitting.  They had all been stored at 2.56V.

Today , 1 month later and with the same multimeter, the voltages are now:

#1  2.55  -0.4%
#2 2.52  -1.6%
#3 2.53  -1.1%
#4 2.53
#5 2.56   0%

For an average loss of 0.8%.  Need to relate that back to the specs and also note that its not a statistically valid sample size.  But still interesting.  Back to my last update on parasitic losses.. these presumably will chase themselves down in parallel packs and ultimately lead to different voltages between the series connections.

Since I do have a solar panel available I'm inclined to leave the balancers connected perpetually.
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