Energy management on a sailboat

Sailboats are like other mobile homes, (Motorboats, RV,) but somehow different.
-
Sailboats do not generate energy from a running motor, or at least
very seldom.
So care has to be taken to save energy and harvest differently.
- Sailboats spend some time at the dock, where grid energy is available to charge batteries and run devices. The rest of the time, it has to be autonomous.
I am trying to design a system that is easy to operate, reliable and efficient, here is the diagram.

To be efficient and save weight, I would like to use LiFePO4 batteries.
I am trying to avoid multiple sources to charge the batteries, so all the sources go thru the CC.
Sources are conbined to the CC via diodes to isolates them from each other.
When I arrive to the dock, the AC source trigger a relay to switch the 117v AC outlets from the inverter to the shore power.
Also there is a power supply that is turned on to supply power to the utilities, and charge the batteries.
There is always a load on the batteries (fridge, instruments, etc..), and always a charge when at dock.
I have a question: There will be a constant voltage from the CC to the batteries since there is always a load on it. How will that affect the batteries ? Will the LiFePO4 batteries suffer from this ?
Comments
I also see you have 120VAC outlets connected to an inverter. Your sailboat already has ALL outlets connected to the shore power plug and breaker panel, correct? Are you going to re-wire a small number of the outlets to the inverter, or all of them?
and
Let's see a picture of your 'hole in the water'
19 SW285 panels
SE5000 inverter
grid tied
KID #51B 4s 140W to 24V 900Ah C&D AGM
CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM
Cotek ST1500W 24V Inverter,OmniCharge 3024,
2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
West Chilcotin, BC, Canada
All the outlets are together on inverter, but switched to shore when shore is energised (relay)
@ westbranch... the fridge is 12vdc and can be handled by CC no problem.
I just don't like to see the battery always getting voltage from CC when at dock... :-(
With LFP, it's not so much that there is voltage on the battery, it's what that voltage is. LFP's don't mind sitting around for months at 60% SOC, but sitting for long periods of time at 90% SOC will shorten their lives. So if the boat is going to be sitting in dock for long periods of time then the float voltage would need to be around 13.1 volts, close to 50% SOC. Since there is a constant 36 volt PV input, the CC would remain in float and the batteries would be fine. If the CC is not that finely adjustable or does not have that preset then I would not recommend LFP. However, there are CC's available that have individual absorb and float adjustments to the 10th of a volt, but they are not cheap. Midnite Solar Kid marine version for example.
The wind generator needs it's own charge controller with a DUMP load or a brake to stop it from spinning when the battery is full. I've never seen wind and solar combined successfully on a single controller.
|| Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
|| VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A
solar: http://tinyurl.com/LMR-Solar
gen: http://tinyurl.com/LMR-Lister ,
Hi Mike, Thanks for the advice for the wind generator. I plan to get one, and will definitly install a protection device at the output.
I should receive the CC before next week, I will set up a lab for it and try few things, and keep you posted....
Thank you !
to know exactly how many Amps went into your battery you need something like this, the Whiz Bang jr http://www.midnitesolar.com/productPhoto.php?product_ID=519&productCatName=Charge Controllers - Classics&productCat_ID=21&sortOrder=9&act=pc
KID #51B 4s 140W to 24V 900Ah C&D AGM
CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM
Cotek ST1500W 24V Inverter,OmniCharge 3024,
2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
West Chilcotin, BC, Canada
That is what it should do but changes in PV output also affect that as well as loads.
KID #51B 4s 140W to 24V 900Ah C&D AGM
CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM
Cotek ST1500W 24V Inverter,OmniCharge 3024,
2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
West Chilcotin, BC, Canada
For the PV out, it should remain constant while at the dock. When I leave the dock, it is another story, load will be powered by the battery with the help of the PV when there is sun. This case is more like normal behaviour.
And you have Boost & Float so, set your float at the long term float voltage (about 85-90% full charge) The higher the float voltage, the shorter battery life you get.
In short, follow the battery Mfg spec, don't trust the charger vendor to have done it right.
|| Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
|| VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A
solar: http://tinyurl.com/LMR-Solar
gen: http://tinyurl.com/LMR-Lister ,
When docked and connected to shore power and you set float to 13.1 volts, the battery pack will supply the loads until it reaches 13.1volts and then the CC will be pretty much be supplying the loads and keep the battery at that voltage. Keep in mind, these settings are not for a DIY battery bank. i.e. 4 LiFePO4 prismatic cells wired in series.
Rick
http://members.sti.net/offgridsolar/
E-mail [email protected]
Cute headsail.
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
@ Dave... it is for sure a risk, but they will be smaller and lighter... also I like to go forward... my boat is called "Fast Forward".. :-)
@ Estragon... I will build a support on the back, 2x 120watts that will serve also as bimini
I received the CC yesterday... I am impressed with the construction.... very sturdy..
I started to do tests.... For MPPT, it will react in about 1.5 minutes from 24v to 34v in simulated PV.
The CC will stay in float mode with a 10 amp load. The PV input will supply the load fast (20 secs) after turning on PV (dock situation with 36vdc supply) and leave the battery in float mode after. I will keep doing tests for few days and more. The CC has a modbus rs485 connection to a wifi server (smail dongle) so I can remotely monitor and change parameters.... keep you posted !!
KID #51B 4s 140W to 24V 900Ah C&D AGM
CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM
Cotek ST1500W 24V Inverter,OmniCharge 3024,
2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
West Chilcotin, BC, Canada
Most of us are all land based and can walk away from a fire. There is nothing worse than a fire at sea. Carry a good life raft or a dinghy and Good Luck!
http://members.sti.net/offgridsolar/
E-mail [email protected]
The BMS serves 3 functions,
1. It has bleeder boards that are connected between the + and - post of each cell. When the charging voltage reaches 3.65 volts the bleeder board circuitry will activate and bleed off power through a resister until all the boards are activated and the cells are rebalanced at 100% SOC.
2. Battery monitoring, either to a digital display or a communications port.
3. It can activate a high and low voltage disconnect relay
In the case on no BMS, setting absorb (boost?) to 13.8 is necessary because of the nature of the LFP charging curve. At the top of the charge curve, between 80 and 90% the curve starts to go from almost flat to vertical at 100 % SOC. Here the voltage rises very quickly and can cause cell damage if it goes too high, so without a BMS it's best not to go there. Setting absorb and float lower keeps the state of charge from ever getting near the vertical aspect of the upper knee in the charge curve. The margin of safety at the top and bottom of the charge and discharge curves costs about 30% of battery capacity.
So there is also something else to consider. A high and low voltage disconnect if you don't use a BMS. But there are solutions for this also.
I use a digital amp hour meter and DC contactors on my system for this purpose.
Later,
Rick
http://www.pbase.com/mainecruising/lifepo4_on_boats
Rick
The daily charge regime for my offgrid battery is to charge to 3.45V/cell if there is enough sun and terminate the charge and shift to float when the charge current reduces to C/50. This results in a battery SOC of >99% (battery >99% full). A float voltage of 3.35V/cell will keep the battery at around 99%SOC. At night we run off the battery. After nearly four years I haven't noticed any change in the performance of our battery.
One change I would would make would be to have your shore battery charger set to 3.35V/cell (13.4V for 12V battery) and connect it via a fuse straight to the battery. The wind turbine will probably have its own charge controller which could connect directly to the battery.
What are you doing with regards to a BMS?
Here is some more light bedtime reading, http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069.html
Simon
32x90Ah Winston cells 2p16s (48V), MPP Solar PIP5048MS 5kW Inverter/80A MPPT controller/60A charger, 1900W of Solar Panels
modified BMS based on TI bq769x0 cell monitors.
Homemade overall system monitoring and power management https://github.com/simat/BatteryMonitor
"After 12 1/2 months of doing nothing but sitting there, at 100% SOC, the cells had lost -11.6% of their previous rigorously confirmed Ah capacity. Remember this is just sitting there at full charge with no float...."
in this post
http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069-367.html#post2312168
This has left me scratching my head as the experience of myself and a number of others who post on the Australian Energy Matters forum and user SteveG who has an LFP based system that is over 6 years old and occasionally posts on what I would call the "alternate facts" forum is somewhat different.
None of us have had anything like that level of loss of capacity. The big difference as far as I can see is that although we are charging to and floating at ~100%SOC during the day we are cycling our batteries on a daily basis.
With this in mind I would change the charge voltage from your shore charger to 3.27V/cell which corresponds to around 50%SOC and disconnect the solar panels from the solar controller if your boat is going to be docked for a period of time.
If you are using solar and wind to charge the battery when cruising I would still keep charging to and floating at ~100% as you need as much reserve as possible to get you through cloudy weather.
For those that want some recently published technical information on capacity loss of lithium batteries during storage it can be found here http://jes.ecsdl.org/content/163/9/A1872.full.pdf . Thanks to user OceanSeaSpray from the cruiser forum for finding this.
Simon
32x90Ah Winston cells 2p16s (48V), MPP Solar PIP5048MS 5kW Inverter/80A MPPT controller/60A charger, 1900W of Solar Panels
modified BMS based on TI bq769x0 cell monitors.
Homemade overall system monitoring and power management https://github.com/simat/BatteryMonitor
Like Dr. House says : Everyone lies. Especially when they can sell you something
At 375 pages, and starting in 2011, the http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069.html was way too chatty to try to bother with.
|| Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
|| VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A
solar: http://tinyurl.com/LMR-Solar
gen: http://tinyurl.com/LMR-Lister ,