If the shunt is on the battery, that is good for tracking charge state as current tapers with constant voltage, and perhaps terminating charge based on profile.
Also good for keeping battery current near zero, and picking up all house loads.
BUT
It doesn\'t allow capping alternator current. So depending on the config, it could drive the stator very hard. Temperature control will limit this for the medium term, but the short term currents could be high. (APS 56V 160A alternator)
Is there a way to run dual shunts, one to monitor battery current, one to limit alternator current?
Or is this simply set by trial and error through maximum rotor duty cycle?
Paul, you raise a good point. We have recently been doing some REC / Victron /WS500 integration testing and found that when we had the REC BMS monitoring our battery current the system seemed much more stable when we added an alternator current shunt and set the WS500 to alternator centric.
Our rationale was that in this configuration the Alternator can look after itself and optimize its operation for the alternator only. Then the REC BMS can act as a high limit controller to the WS500 should the battery conditions need to override the alternator and put the WS500 into CVCC mode.
During our testing this seemed to work quite well and we noted significant improvements in the stability of the overall system.
We passed this back to WS and are hoping to get their thoughts on the matter, as there may be factors which we have not considered.
@al-thomason@officeogss
I will likely start a new post for this one. We are also continuing some pretty detailed testing over the next couple of weeks and will want to keep it all in the same thread.
If I can remember I will post a link on this thread to the new post :)
Dear Rick,
I am planning to install wakespeed 500\'s on a yacht with twin engines.
One engine with 2x 400 amps 24V alternators, the other just one 400 Amps 24V alternator
All three charge the same 24V Lithium bank (14x 280Ah.)
Is this possible? Or are the amps too high?
Best regards, Kees
You have nearly 29 kW of maximum power generation and a just over 12 kWh of LFP. That is not well matched, particularly if you are trying to charge at 0.5C, or 6 kW.
Also, 14 cells in a 2S2P layout is giving you a 22.4V bank, probably not what you want.
With that kind of power available, you probably want a 32 cell battery, which would accept 14 kW at 0.5C, and likely can be efficiently charged by two 400A alternators.
Adam makes a good point about capacity, and you would need some very large wires off of those alternators, very good belt drives, and will need to be careful about side loading on the crank bearings. If you can put one alt. one either, that would help cancel some of the load.
From a configuration perspective it will work. The WS500s can take up to 30 amps on the field. You could even drive the 2 alternators from a single WS500 on the one engine if you wanted, then network the two WS500s together.
Dear Adam and Rick, thank you for your quick response.
In fact the yacht has already Victron 12V Gel batteries of 200Ah each 40 pieces in total. There are 4x alternators of 400 amps each, one will be removed.
The batteries are all connected to a central busbar in a 24V configuration. So are the alternators, on the same busbar. Cables and all is in place. We just want to replace the gel batteries for Lithium and create a balanced and temperature regulated (batteries+alternators temps) charging from the alternators.
to remind: twin engine, one with 2 alternators each 400amps, and one with one alternator of 400 amps.
Idea is that when underway engines running, they supply enough to run the entire 3 phase AC system and the DC system, and also have enough to charge the batteries.
When dropping anchor, the yacht can run all its systems on the batteries for about 8 to 10 hours.
AC three phase is produced with 3 Victron Quatros of 8Kw each, these are already in place as well and working fine. The Quatros also charge the batteries when shorepower or generator power is available.
Tricky thing, I know, it worked before with the gel batteries, but not balanced, so on alternator did almost all the work at the end of the charge cycle, and batteries where warming up as well.
I haven\'t yet purchased the Lithium batteries, as I need to know how many I need for our configuration.
Thanks again for your advice.
Back of my napkin math says you currently have 48 kWh hour of useable battery capacity in your gel cells. So if you are going to have the equivalent, or maybe more \'cause it\'s always better, you would want 64 280 Ah LFP cells wired in a 8S8P configuration to produce 24V. You would then have a safe charge and discharge rate of roughly 29 kW, if you wanted them to last forever.
I\'m curious, why are you removing one of the alternators? Seems to me that you would want to size the system to run on a single engine, in a twin engine setup, for ease of maintenance and fault tolerance.
Dear Adam,
64x 280Ah LFP? to replace 40x 200Ah gel? Should be less LFP no? I was told by a batterie supplier that 14x 24V 280 Ah LFP would do..
The fourth alternator is removed as in it\'s place we\'ll fit a hydraulic pump. Engines are 27 liter 8 cilinder inline Gardner engines. They handle anything..only 245Hp and a max rpm of 1000
Breaking my head on this, as the electricians I have here aren\'t familiar with it either.
Thanks again Adam.
Kees,
If it were me, I would be working it the other way around. Lay out a spreadsheet and list all of your loads, current draws, and run hours per day. Add in what overcapacity you might want, and how many hours of run time you want. That should give you a minimum load demand to use as a starting point, then let your wallet dictate how much bigger you want to take it.
64x 280Ah LFP? to replace 40x 200Ah gel? Should be less LFP no? I was told by a batterie supplier that 14x 24V 280 Ah LFP would do..
Right! You are talking about using pre-made 12V LFP batteries with built-in BMS’?
In that case, you would need 14 indeed. But I don’t like that approach.
Dear Adam,
64x 280Ah LFP? to replace 40x 200Ah gel? Should be less LFP no? I was told by a batterie supplier that 14x 24V 280 Ah LFP would do..
The fourth alternator is removed as in it\'s place we\'ll fit a hydraulic pump. Engines are 27 liter 8 cilinder inline Gardner engines. They handle anything..only 245Hp and a max rpm of 1000
Breaking my head on this, as the electricians I have here aren\'t familiar with it either.
Thanks again Adam.
Lithium cells are 3.4v
LA are 12v
So 64/4 = 16 equivalent x 280AH
That may make more sense
As Rick says below - run the load / demand numbers
The idea of 14-16 self-contained 12V LFP batteries, without any kind of monitoring of their state, is too scary for me. What happens if one of them decides to shutdown?
Wow...more participants, thanks !
I\'ll take 14 24V MG batteries with built in BMS. They are 100% compatible with the Victron system which is already in place. The previous AGM capacity was fine, a tiny bit more always better off course.
One can shut down with this system, and if so, it needs to be replaced. We still have a generator back up to keep going if the system blacks out.
Perhaps nice for you guys to see which yacht it is: http://www.yachtchartersultana.com/ Built in 1969 and I have rebuilt her to new in 2010. Except the engines, they are original but rebuilt better (and prettier) than new. She has just been sold and the new owner asked me to look after her refit again. (I work for a shipyard now)
Thanks again, really appreciate all your inputs
