Lithium (LiFePO4) Install

[s/v Thea]

Ian,

I've left my prosine 2000 and ample power regulator at the flooded gc settings. Most of my charging has been with solar (I have 800 watts of panels). I've bumped the voltage up to 14.5 on the solar regulator.

A few times I've closely monitored the voltages as the charge neared completion when charging at 30 to 40 amps. Current stays pretty constant up to 14.2v or so, then current starts dropping off and voltage rising quicker. As the voltage approaches 14.5 volts I'll get a few cells shunting (3.7 volts on mini bms), lowest cell about 3.6, no cell has gone above 3.7v. I have to be paying attention as the shunting phase only last a couple of minutes then controller goes to float. I haven't timed it but I'm guessing that time from full charging current to charge finished is about 15 min.

Doug

[Namoian]

Thanks Doug that is very helpful. We too have quite a bit of solar and am looking forward to seeing the interaction of the Blue Sky solar controllers and the Thunderskys.

[goboatingnow]

Doug whats the solution for large format cells, the shunt system would have to handle large currents. any ideas

Dave

[s/v Thea]

Dave,

My cells are 200A the shunts on the mini bms handles up to 0.75A which seems to be ok. I think as long as the cells are balanced then then the shunting current should be quite low. As the cells age I may have to top balance once in a while or maybe move them around between banks (mine are in a 4 x 4 arrangement). I did buy a spare cell so if after a few years I have a particularly bad one I can swap it out.


Doug

[Namoian]

When the batteries where installed last week, they had never been balanced and when a full charging current (80A) was applied this week, one of the cells went to 3.8V while others were still down at 3.4V. The LED on the cell board of the 3.8V cell began flashing an error condition and if I had a BMS, the contactor would have tripped and disconnected the batteries. The installer advised balancing the cells which was accomplished by slowly upping the charger voltage to 14.8V (3.7 V/cell) until all the cell boards were shunting and the voltage on each one was 3.7V (well, one stayed at 3.6V). The cell boards can "burn off" 1.5A each via their attached resistors which did get hot during the balancing process. This is not enough "burn off" however to stop a cell going over voltage if they are unbalanced and a high charging current is being applied.

As Doug says, very little shunting has occurred on subsequent charges now that the cells are balanced.

I guess one issue to come to consider if one had a BMS managing a contactor is that an event such as the above could result in losing all power at critical juncture such as entering a pass or during a critical radio call. A BMS audio alarm but with a contactor override capability may be the ideal.

[CharlieJ]

Namoian-
One of our CF members (Electric1) has built a mini BMS specifically for the marine market. It includes alarms prior to opening the contactor for either a low voltage or high voltage event.

Charlie

[NahanniV]

Namoian- (and others)

I would be interested to hear how your LiFePo4 battery pack is working out after a full season ?

Cheers,
JM.

[senormechanico]

I'm one of "the others" with a 200 aH LiFePo4 bank (4 cells).
Boat's got all the toys and 320 watts of solar with a BlueSky 2512iX MPPT controller.

I LOVE these cells !

[NahanniV]

"LOVE" ! That sounds good.

I'm contemplating installing LiFePo4 as the house bank on my boat.

Any details you could share would be helpful, like:

- do you have a BMS ? What brand ? Do you Love it too ?
- do you have some kind of automatic under/over voltage protection ?
- What brand of cells do you have ?
- do you use them to start your engine ? If so, what size ?
- any problems or pitfalls I should be aware of ?

Cheers,
JM

[mrm]

Originally Posted by Namoian

...we replaced it with a Thundersky bank (16 X 160AH cells) organized into 4 X 160AH batteries for a total capacity of 640AH...

Are you going to use them as a single bank of 640Ah capacity? If yes, then the more common approach (and considered superior) is to first build capacity and then build voltage. Your pic shows the opposite.

If I understand correctly it is your supplier who warrants this installation so it is mostly their problem, but still I would suggest talking to them about this configuration.

[senormechanico]

HiPower brand
MiniBMS from Dimitri
Overvoltage cuts off alternator field, also shorepower charger (which I never use due to solar meeting all my needs)
Only one bank on boat. It starts my Volvo MD2020.
They are for all practical purposes a direct replacement for flooded lead acid.
I'd never go back to flooded cells.

[s/v Thea]

I've had 16 x 200 amp thunder sky arranged in 4 banks of 4 in service for two full seasons now, very happy with them. I'm using two minibms systems each handling 2 x 4 cells connected to a contactor, so if I have an LVC/HVC event on one cell will only disconnect 1/2 of batteries.

I have not experienced any problems with cells going out of balance or banks being unequally charged/discharged with the series/parallel arrangement.

[deckofficer]

Originally Posted by senormechanico

They are for all practical purposes a direct replacement for flooded lead acid.
I'd never go back to flooded cells.

I'm sure hearing that a lot here on CF. Explains why Balqon had such a run on their clearance cells just from the gang here on CF. The 700 a-hr cells at $462 dropped from 80 something in stock to 18 today. If Balqon didn't know about the Cruiser's Forum, they do now.

[Namoian]

Lithium battery update: No problems with the Lithium house battery bank after two cruising seasons (plus we live aboard). Lots of power and fast charging. We sailed around the West Coast of Vancouver Island last summer and even in remote anchorages, my wife enjoyed running her hair dryer, the microwave, blender etc (fortunately we had lots of sunshine which is rare in this part of the world).
Best wishes for a happy new year.
Ian