LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

[john61ct]

And there WILL be emergency navigation scenarios where you need all the power you can get, and sometimes such conditions are not conveniently momentary, last for extended periods.

Not good running out of juice while navigating a tricky inlet against the running tide, with lots of docks and other boats around close by.

Insurance inspection will surely have similar questions.

[OceanPlanet]

Originally Posted by T1 Terry

Winston and possibly Sinopoly are the only manufacturers of LYP (lithium yttrium ferrous phosphate) cells, Sinopoly may has lost the right to the chemistry as it belonged to Winston Chung and there is bad blood between the 2 companies now, well worse that the bad blood that caused the split in the first place anyway :lol: For those that may not know the history with these two companies, the were once Thundersky, then the split and Winston Chung took his new formula with him, a big court battle, Sinopoly paid Winston an obscene amount of money thinking they had bought out his ability to manufacture, then discovered all they bought was the Thundersky brand name and the right to use the new formula.... now I see Winston sell both LYP under the Winston label and LFP under the Thundersky label, so who knows what the latest state of affairs are with them and no idea if Sinopoly still produce the LYP cells.

Jogn, no idea who supplies Redarc, I didn't even realise they were selling lithium batteries now, Enerdrive use Sinopoly cells, no idea what the deal is with Victron or even if they are manufacturing their own from the basic components, or maybe special order from A123, no idea.
Every man and his dog seem to claim they are lithium battery manufacturers these days but there really are only a handful of component manufacturers, the rest are just branded to suit a buyer

T1 Terry

T1 probably knows this...however there are many Li cell manufacturers, that do not to sell to the DIY market. The OPE-Li3 (Lithionics) batteries we sell don't use any of the cell mfgs discussed here.

[OceanPlanet]

Originally Posted by alctel

I'm looking at the Genasun solar controllers for lithium

Their 'CV Voltage' is 14.2 - which is bit higher than I'd like (I'd be more comfortable with 14.0) - but if that was a 'stop charging' mode that would be good, but I can't find a description on the site or in the manual what happens when it hits 14.2! Ideally it'd just stop, but in that case I can't find the voltage where it would start charging again!

Does it charge at a constant current until it hits 14.2 and then just switch to CV mode and hold it at 14.2 and reduce the current? Isn't that just a float mode that would ruin the batteries?

Anyone have any insight?

Genasun makes many different algorithms, and we sell hundreds with custom profiles done to our specs. Keep in mind that Genasun no longer sells Li batteries, and the 14.2v Li controllers they sell were matched to their batteries. So although that single target voltage may still work for some Li batteries, we now have them custom made with an algorithm we like for our OPE-Li3 (by Lithionics). For 12.8v nominal, the bulk/balance charge is to 14.5v, when that is reached there is a short absorption @ 14.2v (15min or so) then the target voltage is a float of 13.4v. Note that 13.4v isn't quite fully charged, however it is now well known that leaving Li sitting fully charged will slowly degrade the battery capacity over time.

Then If/when the battery discharges to <13.2 then the program resets back to bulk.

[andreas.mehlin]

Originally Posted by john61ct

And there WILL be emergency navigation scenarios where you need all the power you can get, and sometimes such conditions are not conveniently momentary, last for extended periods.

Not good running out of juice while navigating a tricky inlet against the running tide, with lots of docks and other boats around close by.

Insurance inspection will surely have similar questions.

Well, sorry but I disagree. During my 25 000 miles half around the world twice, I have never been in a situation where I have needed full throttle any time, especially not over longer time. As long one is aware of the range you also plan your entries and action from that. It might be different from person to person how one sail and where he sails.

So, with 20kwh battery bank, I think I would be fine. The question I had in mind was more if it was a good idea to split the bank i to several banks which all are able to connect as a main bank with fast connectors.

[john61ct]

Sure a truly expert sailor who really knows their boat and local conditions has less need of propulsion.

I myself wouldn't feel safe without longer potential runtime in reserve.

[T1 Terry]

Originally Posted by andreas.mehlin

Well, sorry but I disagree. During my 25 000 miles half around the world twice, I have never been in a situation where I have needed full throttle any time, especially not over longer time. As long one is aware of the range you also plan your entries and action from that. It might be different from person to person how one sail and where he sails.

So, with 20kwh battery bank, I think I would be fine. The question I had in mind was more if it was a good idea to split the bank i to several banks which all are able to connect as a main bank with fast connectors.

The problem with multiple batteries in parallel is each battery requires its own BMS to protect it. They would also require current limiting for each battery so one doesn't do all the work till it is fully discharged nor take all the charging current till it reaches the high SOC knee curve.
The thing to keep in mind is the very low internal resistance of Li cells and the almost flat discharge and charge curves through the mid range. The battery bank with the shortest cable or best connections will be the priority bank, the other bank simply tags along until the priority bank is deeply discharged.

I would not consider using single 300Ah or 400Ah cells in series, you will go crazy trying to keep them in any sort of balance, 3 or 4 x 100Ah cells in parallel would be a far better proposition as the multiple cells balance out each others strengths and weaknesses resulting in a battery pack that requires very little is any balancing to keep the cells within the necessary 150mV imbalance range...... balancing under 150mV deviation is just an exercise in futility and fiddling for the sake of it. At 150mV it ain't broke so doesn't need fixing

As far as 16 x 100Ah cells for the outboard motor, how big is this motor and just how long do you want to run it at full power? Is it just for tender or are you planning to water ski behind it? A 12ft dingy will run all day as a fishing boat up a river with an electric outboard on a 100Ah 12v battery and still not exhaust the full capacity, 16 cells in series would be a 48v battery and delver over 14kW of power for around 20 mins.... if you could actually stay in the dingy for more than a few mins at full power so I doubt you actually use full power for 20 mins in any one day.
As far as the prismatic cells doing part time duty as a propulsion battery, as long as the majority of the run time was 1CA or less, not a problem, they can deliver up to 5CA but voltage sag becomes an issue and cell temp if held for a prolonged period.... but a boat motor never sees full load unless it is over propped and as the electric motor has all the torque from stationary up to max rpm I'd hate to think about the carnage as you left the mooring under full power

T1 Terry

[pacific_voyager]

Can we please take electric propulsion to a separate thread? There is enough information, misinformation, and just plain b.s. on the subject topic without wandering off the track to another layer of confusion.

[OceanSeaSpray]

Originally Posted by alctel

I'm looking at the Genasun solar controllers for lithium

Their 'CV Voltage' is 14.2 - which is bit higher than I'd like (I'd be more comfortable with 14.0) - but if that was a 'stop charging' mode that would be good, but I can't find a description on the site or in the manual what happens when it hits 14.2! Ideally it'd just stop, but in that case I can't find the voltage where it would start charging again!

Does it charge at a constant current until it hits 14.2 and then just switch to CV mode and hold it at 14.2 and reduce the current? Isn't that just a float mode that would ruin the batteries?

Anyone have any insight?

Yes, those "lithium" controllers are quite useless in spite of some nice power engineering inside. I have modified some GV-5 and GV-10 for someone to make them regulate at 14.0V instead (piggy-back a 2.2M 0805 SMD resistor on top of another one, so pretty easy), but they will still hold your cells at a constant voltage indefinitely, so you need a SWITCH.

I can post a picture of the mod later if someone is interested.

[john61ct]

Originally Posted by T1 Terry

They would also require current limiting for each battery so one doesn't do all the work till it is fully discharged nor take all the charging current till it reaches the high SOC knee curve

I'd really appreciate details on such a current limiting device, ideally links to purchase.

[OceanSeaSpray]

Originally Posted by john61ct

I'd really appreciate details on such a current limiting device, ideally links to purchase.

It is called a length of cable. Any voltage drop will cause that battery to immediately contribute less current. If you parallel banks, the cabling resistance should be balanced as much as possible and having a little resistance helps for that matter.

When you parallel cells using link plates, one cell may work harder than the others at times and you never see it. It all comes right again when they get in a region where the voltage gradients are more noticeable, i.e. outside 40-65% SOC.

[T1 Terry]

Originally Posted by pacific_voyager

Can we please take electric propulsion to a separate thread? There is enough information, misinformation, and just plain b.s. on the subject topic without wandering off the track to another layer of confusion.

Agreed, but this is really about a hybrid use of propulsion and house batteries so it sort of fits in here.... but another thread if this becomes a reality would be a must. At the moment it is just talk about what is possible so at this level it is really only a secondary use of a house battery bank rather than a main propulsion designed battery pack.
In all seriousness, after the number of posts on this thread I doubt there is anything much new to add besides reports of capacity retention after so many yrs use or cycles.
After over 6 yrs of installing systems big and small into RV's I can say that the only cell failures have been the result of human error and these were murdered, they didn't die of natural causes. Those that have been treated right no matter that they have been worked very hard every day have showed no signs of deterioration, so that short cycle life myth can be put to bed along with the 10 yr calendar life, some of the cells in the early system were already 4 yrs old since manufacture but still in the box, new old stock. This was intentional as the question regarding the effects of mixing old with new cells and LFP cells with LYP cells had never been answered, to date there appears to be no adverse effect.

T1 Terry

[toddedger]

I had my GV-10 's custom made at 13.8. At a fraction C rate my bank doesn't have any trouble sucking in the power 13.8. When I requested that lower voltage the Genesun engineer called me up and said with that voltage my batteries would never fully charge. I told him yah that's the idea. I use a switch after each charger to be able disconnect manually if I want.

[OceanSeaSpray]

Originally Posted by toddedger

I had my GV-10 's custom made at 13.8. At a fraction C rate my bank doesn't have any trouble sucking in the power 13.8. When I requested that lower voltage the Genesun engineer called me up and said with that voltage my batteries would never fully charge. I told him yah that's the idea. I use a switch after each charger to be able disconnect manually if I want.

On stock units it is quite a simple matter of skewing the voltage divider in the measurement circuit, so it looks like that the output has reached 14.2V when the voltage is in fact lower... Genasun will have tweaked the value in the code instead.

Yes... 13.8V is certainly enough to fully charge them (and some more) anyway and also low enough to allow memory effects to set in. You need some voltage to help preventing that and it is important to get a decent, proper charge now and then so the whole system doesn't start drifting south.
Sometimes the alternator can provide that on boats that don't motor often.

[Maine Sail]

Originally Posted by toddedger

I had my GV-10 's custom made at 13.8. At a fraction C rate my bank doesn't have any trouble sucking in the power 13.8. When I requested that lower voltage the Genesun engineer called me up and said with that voltage my batteries would never fully charge. I told him yah that's the idea. I use a switch after each charger to be able disconnect manually if I want.

I actually used to believe that until I started physically testing the theory. These cells will charge to 100% SOC at voltages below 13.8V / 3.45VPC. I have charged them to 100% at just 13.6V / 3.4VPC all of this confirmed with physical capacity testing. By how most LFP cell makers define "charged" they won't hit 100% SOC / full at 13.8V but their definition is; "Charge to 13.8V or 14.2V or 14.6V and stop charging". This does not mean "Charge to 13.8V or 14.2V or 14.6V and continue holding voltage". "Charge to XX.XX volts then stop" and "Charge to and maintain XX.XX volts" are two entirely different things.

The difference lower voltages make is to allow a bit longer absorption time/duration when adapting them to lead acid type chargers where "duration" is minimally adjustable. It also allows you some head room were a cell to start to drift.

When the batteries are full is dependent upon current, target voltage and duration at target voltage. With a very low current source, and a 13.8V target, the batteries are essentially at or very close to 100% SOC by the time they get to 13.8V. With a higher current, say .3C - .5C they can do about 15-40 minutes at 13.8V before becoming full. Drop down to 13.6V and they still become full but the duration at voltage can be slightly longer, dependent upon available current. Of course this current at a maintained voltage can not be indefinite or you are stressing the cells by "floating" them at 13.8V.

The switch you have is a very good idea. When the battery attains 13.8V simply turn it off.

[alctel]

Thanks for all the feedback guys.

So currently there is no charger/controller on the market that just has a straight switch on/off when it hits a certain voltage?

Note I'm not talking about the battery protection system with relays here, I'm just talking about the chargers so I never even hit the BPS voltages