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Old 12-05-2015, 13:42   #4516
Tri
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Hi hellosailor,

thanks for your reply. On the Victron page (that is the manufacturer of the equipment) for their BMS it says you need a 12/12 DC/DC Converter. I understand it is to stabilize the voltage going in the LFP and to eliminate residual swinging (not sure if that is the right translation) resulting from the AC to DC conversion in the regulator of the outboard engine. There is a regulator for normal batteries in the outboard engine (Tohatsu MFS 30 C) but I understand in conjunction with LFP batteries one needs a DC/DC Converter to not harm the battery (even if the regulator from the outboard engine provides normal 12 V to load a standard battery). I understand Mastervolt recommend the same for their systems.

With regard to the BMV 700 I think it works on the basis of voltage but with a LFP the voltage stays basically the same until about 30% loaded and then it drops. Not sure therefore if the BMV 700 works for that.

Cheers,
Achim
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Old 23-05-2015, 00:28   #4517
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Hi Tri,

My understanding is that for LiFePO4 batts you need a DC-DC charger specific for Li batts so they are charged at CC/CV, constant current rising to around 14.4v @constant voltage until the current drops to below 5% of capacity then it will disconnect at full charge.

Dc-DC chargers for Li have a voltage step down and booster to regulate and keep the voltage constant no matter what the output is on your alternator, i am not that farmiliar with boat engines but i use one on my car to charge my Li batts and it also works with regenative braking systems.
Also use a bmv700 to monitor batts and it shows Ah left and time to go, i am very happy with it, also use it to disconnect batts when 80% discharged, and sounds alarm at 70% SOC.

Cheers
Ken
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Old 23-05-2015, 01:44   #4518
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Hi,

I dont want to disturbe the flow but thought I could pick your brains. I think about installing the following system on board (see attached picture - hope it is visible). I have 4x 115 Wp solar panels. Two are connected in line and will go into one of the two MPPT chargers. I have no AC on board and only a 15Ah max additionally from my 30hp outboard engine that could / will load the batteries. There is no additional starter battery. I was told I might need two DC/DC Converter. One to feed the battery from the outboard engine and one after the battery to protect electronic equipment from the higher voltage of the LFP battery. Is that correct?

Would be great to get you feefback.

Thanks and cheers

Achim
Haven't been here for a while, but I received an email to say there was another post... and there are hundreds of them :lol:
You haven't mentioned the voltage of your solar panels, but if they are 12v nom. panels and connect them in parallel, you can link the outboard battery feed in as well, add a Schottky diode to prevent back flow and a fuse to protect the wiring, and the Victron MPPT controller will take care of the charge control. Not sure if the Victron BMS works in with the Victron MPPT controller, something you would need to ask Victron about, but I believe the Victron products can all link into a computer control program and tell you everything while controlling all.
As for the 700BMV telling you accurately how much remains in the battery pack at any one time... the only thing that will stuff that up is balancing modules on the battery cells as they waste power the 700BMV isn't aware is happening, so it would not deduct that amount from the total battery capacity. Without the nuisance balance boards, the 600 and 700BMV can very accurately trace battery capacity over quite long periods and has an auto resync feature that can correct the 100% SOC point each time the battery actually reaches 100% charged. They are a great bit of gear, not overly stunned by the Victron product in general, but these units work really well. Apparently there is now a down loadable upgrade available to correct the loss of battery capacity after a disconnection, an issue someone complained about on this thread a while back.

T1 Terry
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Old 23-05-2015, 04:31   #4519
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Wow, I see the chaff gets thrown back into the seed bin still for some reason :lol:
The only safe way to run an Li system is separate positive bus bars, but I agree with the inverter/charger living on the load bus and the 240vac supply to the inverter/charger switched by the HVC, but that cut must be cell level driven, not terminal voltage, the margin for error is too large between the highest and lowest cells.
With separate load and charging bus arrangement, the LVC can separate the battery from the load yet the charging sources still have the access to recharge the battery till the LVC return level has been reached, then the system returns to normal operation. The same with the HVC, you want the load to pull the high cell voltage down till what ever rest parameters are met and the charging can resume.
This is the only way you can have an automated system that requires no outside interference. The only thing the owner needs to do is watch what the max variation there is between the highest and lowest cell at the end of boost charging. If it is under 250mV, go back to what ever it was you were doing, if it is over 250mV, make a note of which cell is high and which cell is low, then recheck the next time the top of boost charging is reached, if it's the same 2 cells, make a note to charge the low cell the next time you have a few spare mins. If the difference is 500mV, give yourself a back hander for being so slack, then fid out if there is a problem causing the imbalance, like a loose terminal bolt. Then fix the problem.


T1 Terry
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Old 23-05-2015, 17:35   #4520
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Originally Posted by T1 Terry View Post
Wow, I see the chaff gets thrown back into the seed bin still for some reason
The only safe way to run an Li system is separate positive bus bars, but I agree with the inverter/charger living on the load bus and the 240vac supply to the inverter/charger switched by the HVC, but that cut must be cell level driven, not terminal voltage, the margin for error is too large between the highest and lowest cells.
With separate load and charging bus arrangement, the LVC can separate the battery from the load yet the charging sources still have the access to recharge the battery till the LVC return level has been reached, then the system returns to normal operation. The same with the HVC, you want the load to pull the high cell voltage down till what ever rest parameters are met and the charging can resume.
This is the only way you can have an automated system that requires no outside interference. The only thing the owner needs to do is watch what the max variation there is between the highest and lowest cell at the end of boost charging. If it is under 250mV, go back to what ever it was you were doing, if it is over 250mV, make a note of which cell is high and which cell is low, then recheck the next time the top of boost charging is reached, if it's the same 2 cells, make a note to charge the low cell the next time you have a few spare mins. If the difference is 500mV, give yourself a back hander for being so slack, then fid out if there is a problem causing the imbalance, like a loose terminal bolt. Then fix the problem.


T1 Terry
Good write up, I have since redrawn the diagram to 2p4s and have the I/C wired to load and have the LVC wired to a 12v/110v ac relay. Most pieces are there, just need to pick up the batteries and bms when I get home.

- Ronnie...on the geaux
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Old 27-05-2015, 19:44   #4521
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

I was about to install a bank of 4 Winston 1000 AH cells. Simple, easy to setup for 12 volt.

Someone mentioned that they had gone with 2 banks of 4 x 400 AH cells instead. The rationale being that if they happened to have a cell fail they could disconnect one bank and still have a working bank. Seems a reasonable idea. Cost is not that different (a little cheaper) and the difference between 1000AH and 800AH for us is very minor.

I then started looking at how to set it up. I would think the easiest is Parallel 2 cells making a single 800 AH cell then series the 4 to give me a 12 volt 800 AH bank (2P4S). It needs 4 cell boards and 1 head BMS unit. If I lost a cell I would have to reconfigure breaking the parallel links to just a bank of 4. I would think that the parallel cells would always be the same voltage so I can put the cell boards on either of the parallel cells.
The alternative is to configure 2 banks of 4 then parallel the 2 banks, so 4S2P. This would require a cell board for each cell (so now 8 instead of 4) and 2 Head boards and try and manage each bank separately. The big advantage is that in the case of a failure it’s very easy to separate the banks. Bit of a bigger issue with HV or LV events as where do you break the charging or discharge, but I’m thinking maybe I’m over complicating things for the sake of something that shouldn’t happen (cell failure) unless it’s initially faulty or I really mess up the install.

Can anyone see an issue with 2P4S as it seems easier to do? How likely is a cell to fail if looked after?
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Old 27-05-2015, 20:49   #4522
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

I would be more inclined to go with 4 x 200Ah cells in parallel to make the 800Ah, then 4 sets in parallel to build a 12.8v battery pack. This way the pluses and minuses from manufacturing tolerances better balance each other out resulting in a far better balanced pack that will maintain its balance for longer.
I would avoid balance boards and devices that control them as the added complications are not required and just add more things to go wrong.... and balance boards do that with monotonous regularity. The wholw balance board and central control unit is designed to incorporate a mains charger control so it can drop the charge back to trickle to allow the balance boards to control the voltage by burning some of that cells capacity off. That's even a little sus when using 100 x 40Ah cells in series as the whole lot bar 1 cell must be held high till all the cells reach the preset voltage.... every time you recharge, there is not a hope in hell that the little board can burn off enough to balance 800Ah unless it was already balanced.... then it wasn't needed anyway. If the charge rate does not drop back to a trickle charge, the over voltage cell will continue charging until both it and the balance board are damaged, then the whole system falls down because that cell will always be out of balance and it will continue to get further out of balance.
easiest method, monitor the cell voltages, stop charging if a cell reaches 3.6v, if the difference between cells exceeds 250mV at the top end of charging, 14v, charge the lowest cell till all the cells voltage adds up to 14v without a cell reaching 3.6v. It doesn't get easier than that and there is no need to complicate something that easy simply because it looks too easy.


T1 Terry
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Old 28-05-2015, 10:08   #4523
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Another advantage of smaller cells over the big ones is that it is more practical to carry a spare. No need to break the bank in half if you could swap out a bad cell.
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Old 28-05-2015, 11:19   #4524
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Need help - Looking for a compatible diversion (dump) charge controller that will complement my 400 ah LiFePO4 bank. The controller will regulate a 350 watt (max) SailGen hydro generator, so it needs diversion capability. The SailGen kit came with a Flexcharge NCHC-12, but after consulting with the knowledgeable folks at the Flexcharge I cannot use it with LFP cells due to their “Energy State Taper Charge Method” which pluses the voltage in the 14.3 to 15.9 range – much too high for LFP.
So, looking for a safe PWM (user adjustable) controller with diversion function. Would a Schneider Electric (aka Xantrex) C40 work? Other options??
Thanks in advance - Gerry
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Old 28-05-2015, 16:14   #4525
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Quote:
Originally Posted by T1 Terry View Post
I would be more inclined to go with 4 x 200Ah cells in parallel to make the 800Ah, then 4 sets in parallel to build a 12.8v battery pack. This way the pluses and minuses from manufacturing tolerances better balance each other out resulting in a far better balanced pack that will maintain its balance for longer.
I would avoid balance boards and devices that control them as the added complications are not required and just add more things to go wrong.... and balance boards do that with monotonous regularity. The wholw balance board and central control unit is designed to incorporate a mains charger control so it can drop the charge back to trickle to allow the balance boards to control the voltage by burning some of that cells capacity off. That's even a little sus when using 100 x 40Ah cells in series as the whole lot bar 1 cell must be held high till all the cells reach the preset voltage.... every time you recharge, there is not a hope in hell that the little board can burn off enough to balance 800Ah unless it was already balanced.... then it wasn't needed anyway. If the charge rate does not drop back to a trickle charge, the over voltage cell will continue charging until both it and the balance board are damaged, then the whole system falls down because that cell will always be out of balance and it will continue to get further out of balance.
easiest method, monitor the cell voltages, stop charging if a cell reaches 3.6v, if the difference between cells exceeds 250mV at the top end of charging, 14v, charge the lowest cell till all the cells voltage adds up to 14v without a cell reaching 3.6v. It doesn't get easier than that and there is no need to complicate something that easy simply because it looks too easy.


T1 Terry
I had thought of the 200's but its a problem of real estate. I can fit the 8 x 400 but that many 200's would just not fit. Thanks
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Old 28-05-2015, 20:09   #4526
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Need help - Looking for a compatible diversion (dump) charge controller that will complement my 400 ah LiFePO4 bank. The controller will regulate a 350 watt (max) SailGen hydro generator, so it needs diversion capability. The SailGen kit came with a Flexcharge NCHC-12, but after consulting with the knowledgeable folks at the Flexcharge I cannot use it with LFP cells due to their “Energy State Taper Charge Method” which pluses the voltage in the 14.3 to 15.9 range – much too high for LFP.
So, looking for a safe PWM (user adjustable) controller with diversion function. Would a Schneider Electric (aka Xantrex) C40 work? Other options??
Thanks in advance - Gerry
Plasmatronics in Aust make a 20 amp and 40 amp PWM regulator that has a dump load function as well as the normal solar control function, a very wide programming range in the program 4 menu and a number of very useful functions that can be programmed to work independently of its primary control function. A great piece of gear and only around the $200 make from a few E Bay sellers.

T1 Terry
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Old 28-05-2015, 20:19   #4527
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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I had thought of the 200's but its a problem of real estate. I can fit the 8 x 400 but that many 200's would just not fit. Thanks
Have you thought about 4 packs in series of 8 x 100Ah cells in parallel?
I fitted a 700Ah pack built this way in a European van a few mths back and the owners are over the moon on just how well it works and how well it fitted into the available area, half on each side of the van with cables to link the 2 x 6v packs. Once balanced this pack has not even looked like wandering at all and it gets worked hard, runs their air con, 3 way fridge, water heater and microwave, plus the usual stuff, all recharged via solar and topped up with alternator charging when needed.

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Old 29-05-2015, 08:37   #4528
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Plasmatronics in Aust make a 20 amp and 40 amp PWM regulator that has a dump load function as well as the normal solar control function, a very wide programming range in the program 4 menu and a number of very useful functions that can be programmed to work independently of its primary control function. A great piece of gear and only around the $200 make from a few E Bay sellers.

T1 Terry
So the typical PWM controller is okay to use with LFP cells - good to know! http://www.cruisersforum.com/images/...humb.gifThanks T1 Terry!
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Old 29-05-2015, 17:16   #4529
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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So the typical PWM controller is okay to use with LFP cells - good to know! http://www.cruisersforum.com/images/...humb.gifThanks T1 Terry!
Only if the charging voltages for bulk, absorption and float can be changed, the length of the absorption phase and the voltage plus time it returns to boost. Unfortunately most solar controllers do not have this degree of flexibility and that makes them unsuitable without some form of interface doing the actual control.

T1 Terry
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Old 29-05-2015, 17:49   #4530
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Only if the charging voltages for bulk, absorption and float can be changed, the length of the absorption phase and the voltage plus time it returns to boost. Unfortunately most solar controllers do not have this degree of flexibility and that makes them unsuitable without some form of interface doing the actual control.

T1 Terry
Understand & agree! - I have identified 2 units that have the ability to be set to lithium friendly voltages, including setting to float low enough to effectively disable it. And, since we're going to cycle the cells rather than hold them fully charged, I have designed a simple 12v light & buzzer warning in parallel with the dump circuit so we can retract the generator from the water when charging begins to taper.
Thanks again!
Gerry
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