Sailboat upgrade to EVE LiFePO4 600ah @ 12v - design review

[andreshs1]

Hi all

thank in advance for the help and advice...

I am in the process to upgrading my house bank to LiFePO4, installing 8 EVE 304ah cells, making a 12v 600ah system. While the starter battery will remain a lead acid 110 ah battery

Solar array:
- is it possible to charge the 2 banks with the single MPPT? or do I need to isolate the banks and feed only the house bank?
- if I isolate the house bank, then I should use a relay to cut the PV from the solar panels before disconnecting the charge relay, correct?
Alternator and AC to DC charger:
- as the alternator will be connected to both banks, do I still need to install a DC to DC charger or isolator?
I would think that once the LiFePO4 batteries are full, the BMS will disconnect the charge relay, but the alternator should continue feeding the the starter battery, no?
Or is it a matter of the alternator producing too much voltage?
-what Dc to DC charger would you recommend?

BMS:
- what recommendations?
The Tao BMS seems a pretty comprehensive system and allows interactions with external systems (e.g. water heater), and the X2 BMS has good reviews from the Ran Sailing channel.

Below my design, any thoughts? obvious errors?


Regards
Andres

 

[Atomvoyager]

I can't directly answer your questions so will leave that to someone more knowledgeable on the subject. But I did just pose a question on another thread asking about using a common ground between lithium and Agm. It seems obvious that it should be common and I see from your sketch that is the way you have it. I have my Lithium "house" batteries and an AGM engine start battery isolated on always separate circuits for safety. The solar is charging the lithium only and I have a Victron B2B 9A charger on a switch to occasionally charge the AGM from solar since it rarely needs a small charge just to counter its self-discharge. The engine alternator charges only the AGM and I have a Renogy 40A DC-DC charger to transfer the alternator charge to the lithium bank.

 

[svsagres]

I'm doing a similar project (460AHr of EVE cells in my sailboat), but am going about it somewhat opposite of you. Alternator, Inverter/Charger, and Solar will directly charge the LFP house battery, and a small DC:DC charger will maintain the starter. This means I'll be able to pump as much power as possible into (re)charging the house bank, and be ready for when we eventually re-power and get a 120A alternator.

That said, I'm building out a fully integrated system, where Inverter/Charger, Alternator, Solar, and BMS all communicate with each other to coordinate things.

 

[Horsefly]

I'm doing a similar project (460AHr of EVE cells in my sailboat), but am going about it somewhat opposite of you. Alternator, Inverter/Charger, and Solar will directly charge the LFP house battery, and a small DC:DC charger will maintain the starter. This means I'll be able to pump as much power as possible into (re)charging the house bank, and be ready for when we eventually re-power and get a 120A alternator.

That said, I'm building out a fully integrated system, where Inverter/Charger, Alternator, Solar, and BMS all communicate with each other to coordinate things.

I'm helping someone put in a new mostly-Victron system and 560Ah LFP house battery, and he's doing the same way as @svagres. The three main charging sources will go to the LFP house battery, and DC-to-DC chargers will charge the starter battery and the bow thruster battery.

 

[Horsefly]

is it possible to charge the 2 banks with the single MPPT? or do I need to isolate the banks and feed only the house bank?

One MPPT charges one battery / battery bank. If you are going to charge the second battery from Solar, you need a second MPPT. If you use a DC-to-DC charger, you can have the two solar panels go through a single MPPT to the house battery, and charge the start engine from the DC-to-DC charger.

if I isolate the house bank, then I should use a relay to cut the PV from the solar panels before disconnecting the charge relay, correct?

Not sure exactly what you are saying, but if you mean should you disconnect the PV side of an MPPT before disconnecting the battery side, the answer is yes. Although, I'm not sure why you would be disconnecting the solar on a regular basis. I may not understand your plan.

as the alternator will be connected to both banks, do I still need to install a DC to DC charger or isolator?

Confused again. The alternator should be charging the house bank, or the start engine, but not both. That won't work. As mentioned before: Let the alternator charge the house bank and then a DC-to-DC charger to charge the start engine from the house bank. NOTE: There are several risks in hooking an alternator to an LFP battery. You need to use a good regulator like a Wakespeed-500s to prevent bad things from happening. You can probably Google "alternator to Lithium risks" or something like that for details.

I would think that once the LiFePO4 batteries are full, the BMS will disconnect the charge relay, but the alternator should continue feeding the the starter battery, no?

Again, doesn't make sense. Alternator is to one battery or the other, not both. You don't need the BMS (or anything) to disconnect the charge sources from the LFP bank. Instead, have charge sources that manage the charging profile, and can tell as the battery gets full to go into float mode. The BMS is generally there as a last-ditch to protect the battery / cells (some BMS's do actually help to manage the charging, but that is way more than just disconnecting charge sources).

Or is it a matter of the alternator producing too much voltage?

The alternator needs a load. If it is charging the LFP batteries without a sophisticated regulator and the BMS disconnects the charging, the alternator will likely burn up quickly. (that's one of the things you should find from the above Google)

what Dc to DC charger would you recommend?

There are lots of brands, but Victron comes first to mind. Victron comes first to mind on most of the equipment you are talking about.

BMS:
- what recommendations?
The Tao BMS seems a pretty comprehensive system and allows interactions with external systems (e.g. water heater), and the X2 BMS has good reviews from the Ran Sailing channel.

I looked at the Tao BMS some time ago and it seemed pretty impressive, but I don't think I've heard any first-hand reviews of it. I don't know what the X2 BMS is, so I can't help you there. Many sailboat owners with LFP love the REC BMS. It will talk directly to all the Victron gear (and probably others, if you have CAN bus or RS-485). If you go with REC, be ready to shell out some serious money.

 

[captainrivet]

Taos is better and has more features then REC, cost 800Euro. Top notch if you can and want spend 800Euro then go for it, Rec will cost about the same at the end. you cannot go wrong with Tao and Phil (Tao) delivers excellent support. Tao is made from a lifeaboard sailor for boats in the first place and then adapted, REC as far as I know made for RV and then offgrid or vice versa.
Having budget EVE cells my recommendation would be Electrodacus BMS for 150Euro, Problem is availability as Dacian the developer of it is missing parts to produce some…
Know actually anything else beside Electrodacus, Tao or Rec that really works well for boats. yes there are many but mostly junk for boaters.
for me Budget cells, budget Electrodacus BMS…or top notch Winston cells and top notch Tao BMS. Both you can save a lot money and get much more for your buck.
But If you wanna go midprice forget cells, you won’t save anything. suggest to get SOK marine drop in 206AH for 1000$ and save yourself the DIY hassle. Works and real 7 year warranty….

 

[svsagres]

Taos is better and has more features then REC, cost 800Euro. Top notch if you can and want spend 800Euro then go for it, Rec will cost about the same at the end. you cannot go wrong with Tao and Phil (Tao) delivers excellent support. Tao is made from a lifeaboard sailor for boats in the first place and then adapted, REC as far as I know made for RV and then offgrid or vice versa.
Having budget EVE cells my recommendation would be Electrodacus BMS for 150Euro, Problem is availability as Dacian the developer of it is missing parts to produce some…
Know actually anything else beside Electrodacus, Tao or Rec that really works well for boats. yes there are many but mostly junk for boaters.
for me Budget cells, budget Electrodacus BMS…or top notch Winston cells and top notch Tao BMS. Both you can save a lot money and get much more for your buck.
But If you wanna go midprice forget cells, you won’t save anything. suggest to get SOK marine drop in 206AH for 1000$ and save yourself the DIY hassle. Works and real 7 year warranty….

So my REC, with all the needed bits, other than contactors (which would also be needed for the Taos) cost me around $500. For a solution that’s known to integrate with both my alternator regulator and power system. Looking at the comparison chart, I don’t know that the Taos is $400 better. But that’s just me.

 

[andreshs1]

I'm helping someone put in a new mostly-Victron system and 560Ah LFP house battery, and he's doing the same way as @svagres. The three main charging sources will go to the LFP house battery, and DC-to-DC chargers will charge the starter battery and the bow thruster battery.

Thanks for that, can you share the list of components being used?

 

[andreshs1]

Taos is better and has more features then REC, cost 800Euro. Top notch if you can and want spend 800Euro then go for it, Rec will cost about the same at the end. you cannot go wrong with Tao and Phil (Tao) delivers excellent support. Tao is made from a lifeaboard sailor for boats in the first place and then adapted, REC as far as I know made for RV and then offgrid or vice versa.
Having budget EVE cells my recommendation would be Electrodacus BMS for 150Euro, Problem is availability as Dacian the developer of it is missing parts to produce some…
Know actually anything else beside Electrodacus, Tao or Rec that really works well for boats. yes there are many but mostly junk for boaters.
for me Budget cells, budget Electrodacus BMS…or top notch Winston cells and top notch Tao BMS. Both you can save a lot money and get much more for your buck.
But If you wanna go midprice forget cells, you won’t save anything. suggest to get SOK marine drop in 206AH for 1000$ and save yourself the DIY hassle. Works and real 7 year warranty….

I cannot afford the SOK drop-ins, for the same capacity I am looking at over 3K USD and the fact that I am based in HK, so not even sure if I can get those here

cheers

 

[andreshs1]

So my REC, with all the needed bits, other than contactors (which would also be needed for the Taos) cost me around $500. For a solution that’s known to integrate with both my alternator regulator and power system. Looking at the comparison chart, I don’t know that the Taos is $400 better. But that’s just me.

I have been looking at the REC, but I am not able to have a clear idea on what I need on it, while the Tao interface/information seems very straight forward
do you have some good info/documents I could look at?

cheers

 

[andreshs1]

One MPPT charges one battery / battery bank. If you are going to charge the second battery from Solar, you need a second MPPT. If you use a DC-to-DC charger, you can have the two solar panels go through a single MPPT to the house battery, and charge the start engine from the DC-to-DC charger.

Not sure exactly what you are saying, but if you mean should you disconnect the PV side of an MPPT before disconnecting the battery side, the answer is yes. Although, I'm not sure why you would be disconnecting the solar on a regular basis. I may not understand your plan.

Confused again. The alternator should be charging the house bank, or the start engine, but not both. That won't work. As mentioned before: Let the alternator charge the house bank and then a DC-to-DC charger to charge the start engine from the house bank. NOTE: There are several risks in hooking an alternator to an LFP battery. You need to use a good regulator like a Wakespeed-500s to prevent bad things from happening. You can probably Google "alternator to Lithium risks" or something like that for details.

Again, doesn't make sense. Alternator is to one battery or the other, not both. You don't need the BMS (or anything) to disconnect the charge sources from the LFP bank. Instead, have charge sources that manage the charging profile, and can tell as the battery gets full to go into float mode. The BMS is generally there as a last-ditch to protect the battery / cells (some BMS's do actually help to manage the charging, but that is way more than just disconnecting charge sources).

The alternator needs a load. If it is charging the LFP batteries without a sophisticated regulator and the BMS disconnects the charging, the alternator will likely burn up quickly. (that's one of the things you should find from the above Google)

There are lots of brands, but Victron comes first to mind. Victron comes first to mind on most of the equipment you are talking about.

I looked at the Tao BMS some time ago and it seemed pretty impressive, but I don't think I've heard any first-hand reviews of it. I don't know what the X2 BMS is, so I can't help you there. Many sailboat owners with LFP love the REC BMS. It will talk directly to all the Victron gear (and probably others, if you have CAN bus or RS-485). If you go with REC, be ready to shell out some serious money.

Thanks for the detailed review
the Charge relay, will help me disconnect the PV to keep the LFP bank at the mid range. I only use the boat on weekends and the odd week when I am on holidays, and I have read that it is better in that case to keep the bank around 70% (although this might be wrong). So the idea is with the BMS to be able to cut the PV keeping the charge around 70%, and then the weeks when I am actively in the boat, I change the config back to 100%

cheers

 

[svsagres]

I have been looking at the REC, but I am not able to have a clear idea on what I need on it, while the Tao interface/information seems very straight forward
do you have some good info/documents I could look at?

cheers

So the list of equipment I'm using is as follows:

• REC Active BMS (Victron/Wakespeed Version)
  • 500A shunt
  • Variable Pre-Charge Unit
  • REC software/RS485 cable (not strictly needed, but nice to have)
• Battery itself is a 2p4s 460AHr pack, built with 230AHr EVE cells
• Victron Smart BatteryProtect 65 (Low Voltage Disconnect, controlled by REC)
• Blue Sea Systems 7713 500A bi-stable relay (High side disconnect)
  • This is actually a little more difficult to interface then I originally thought, and I partially regret buying it
• Wakespeed WS500 Alternator Regulator
  • Controlling a Hitachi 80A alternator until we re-power with a new engine
• Victron Multiplus Compact 12/2000-80 Inverter/Charger
• Victron Cerbo GX
  • Core piece that interconnects the Inverter/Charger to the BMS/Alternator
• Victron Orion-Tr 18A DC:DC charger
  • Maintains the starter battery (A simple Group 24 Marine Start battery)
• Victron 75/15 MPPT controller
  • Power from 2x 60W 24V solar panels
  • Just enough power to keep the parasitic loads of the monitoring system live if shore power disconnects

Then, because I'm a system integration geek who likes his toys, I have the following extras:

• Victron Smart Shunt
  • Monitors the house loads
• Victron BMV-712
  • Monitors the starter battery
  • Relay used to turn the Orion-Tr on and off
• Netgear M1 Nighthawk LTE router
  • Allows VRM monitoring and remote control of the Cerbo GX over the internet

We're investigating how to remotely control the REC, but I think we can do it from Node Red on the Cerbo (essentially reconfiguring the REC on the fly) to achieve the target SOC of around 70% while the boat is at the dock and just in use for day sailing. The idea is to be able to flip it to 100% the day before we head out for a multi-day trip. Also, I'm probably going to use Node Red to control the Orion, as its alternator detection probably won't work too well the flat charge curve on the Lithium house bank.

Lastly, this will all be tied into our NMEA 2000 network, so I'll probably wind up running SignalK on the Cerbo as well, exporting all the nav data via wifi to my various devices.

So yeah, it's definitely a high-end system, but like I said, I like my toys, and love the challenge of doing system integration.

Edit: forgot to add, there's also a whole lot of circuit protection (Class T fuse, disconnects etc) and various bus bars to interconnect and protect everything.

 

[captainrivet]

So the list of equipment I'm using is as follows:

• REC Active BMS (Victron/Wakespeed Version)
  • 500A shunt
  • Variable Pre-Charge Unit
  • REC software/RS485 cable (not strictly needed, but nice to have)
• Battery itself is a 2p4s 460AHr pack, built with 230AHr EVE cells
• Victron Smart BatteryProtect 65 (Low Voltage Disconnect, controlled by REC)
• Blue Sea Systems 7713 500A bi-stable relay (High side disconnect)
  • This is actually a little more difficult to interface then I originally thought, and I partially regret buying it
• Wakespeed WS500 Alternator Regulator
  • Controlling a Hitachi 80A alternator until we re-power with a new engine
• Victron Multiplus Compact 12/2000-80 Inverter/Charger
• Victron Cerbo GX
  • Core piece that interconnects the Inverter/Charger to the BMS/Alternator
• Victron Orion-Tr 18A DC:DC charger
  • Maintains the starter battery (A simple Group 24 Marine Start battery)
• Victron 75/15 MPPT controller
  • Power from 2x 60W 24V solar panels
  • Just enough power to keep the parasitic loads of the monitoring system live if shore power disconnects

Then, because I'm a system integration geek who likes his toys, I have the following extras:

• Victron Smart Shunt
  • Monitors the house loads
• Victron BMV-712
  • Monitors the starter battery
  • Relay used to turn the Orion-Tr on and off
• Netgear M1 Nighthawk LTE router
  • Allows VRM monitoring and remote control of the Cerbo GX over the internet

We're investigating how to remotely control the REC, but I think we can do it from Node Red on the Cerbo (essentially reconfiguring the REC on the fly) to achieve the target SOC of around 70% while the boat is at the dock and just in use for day sailing. The idea is to be able to flip it to 100% the day before we head out for a multi-day trip. Also, I'm probably going to use Node Red to control the Orion, as its alternator detection probably won't work too well the flat charge curve on the Lithium house bank.

Lastly, this will all be tied into our NMEA 2000 network, so I'll probably wind up running SignalK on the Cerbo as well, exporting all the nav data via wifi to my various devices.

So yeah, it's definitely a high-end system, but like I said, I like my toys, and love the challenge of doing system integration.

Edit: forgot to add, there's also a whole lot of circuit protection (Class T fuse, disconnects etc) and various bus bars to interconnect and protect everything.

That’s a very low amp and simple spec setup…nicely integrated. REC is overkill for that. Also add your Cerbo to the 500$ of the REC
Wakespeed ws500 for a 80A alternator that delivers max. 40A safely. For 40A DC-toDC charging of LFP much simpler, cheaper and more reliable.
All the 1st Tier and expensive high spec stuff all around but core of your system are cheap budget cells…that setup screems for top notch Winston cells 4x300AH would deliver the same then your EVE and again safer as 1P4S setup so you control each cell and not 2p that seen as 1 by BMS…
look at Taos BMS comparison chart and you see what REC lacks compared to Taos BMS.

Go to a Setup with 500A continuous load, 2 engines+alternators+ Real 1200W solar with 3 MPPTs, 12V watermaker, fully electric galley and 220V water heater that’s all managed by the BMS according to SOC eg run waterheater and HF inverter permanently till down to 75% SOC to bleed energy off, shut automatically off watermaker and both inverter at 30% SOC….to optimize cycling between 40 and 60% to extend live off LFP
Can you operate your system manually in case REC dies? I can…all above with a 150Euro BMS called Electrodacus and I have a spare on Board for that price takes 15min to replace and all up and running again.
Anker windlass connected to and run of LFP house, enlarges life of the motor quite strongly as voltage drop very low,operational voltage higher so less amps needed to operate, long operation in case Anker gets stuck…can your REC handle the huge surge and inrush current?

 

[svsagres]

That’s a very low amp and simple spec setup….look at Taos BMS comparison chart and you see what REC lacks compared to Taos BMS

Go to a Setup with 500A continuous load, 2 engines+alternators+ 1200W solar with MPPT, 12V watermaker, fully electric galley and 220V water heater that’s all managed by the BMS according to SOC eg run waterheater and HF inverter permanently till down to 75% SOC to bleed energy off, shut automatically off watermaker and both inverter at 30% SOC….to optimize cycling between 40 and 60% to extend live…
Can you operate your system manually in case REC dies? I can…

Absolutely. All I have to do is force the two contactors on, easy enough to do with both the BatteryProtect and the 7713. Not the wisest thing to do, sure, but anyhow this setup could easily handle a 500A continuous load if I really wanted to, just need to size the contactors right (the 7713 I’m using is rated for 500A, I mostly picked it due to its low static current draw).

The reality, though, is if I was going to that high of a powered system, I would be looking at minimum 24V, or perhaps 48V. I’m just looking at 12V systems here.

 

[captainrivet]

Absolutely. All I have to do is force the two contactors on, easy enough to do with both the BatteryProtect and the 7713. Not the wisest thing to do, sure, but anyhow this setup could easily handle a 500A continuous load if I really wanted to, just need to size the contactors right (the 7713 I’m using is rated for 500A, I mostly picked it due to its low static current draw).

The reality, though, is if I was going to that high of a powered system, I would be looking at minimum 24V, or perhaps 48V. I’m just looking at 12V systems here.

That 500A blue system 7713 melts with 350A continuous....they can really do 250A, half of the spec…

24v or 48 was no option, lots new or overhauled high current 12V equipment from windlass to 2x new engines with new alternators and starters…to just put this to 24V would cost me 4000Euro in parts and lots labour myself without a real benefit. 24-12V converter won‘t handle the surge of a windlass or an electric whinch…
the huge load continuous is a 4kw 12V LF inverter plus you have to spec some of that gear runs simultaneousl.
its actually simple, the big inverter connects directly with 40cm long 2x120mm2 cables to 2x350A T3 fuses and they via massive busbars directly to shunt of battery which are directly connected via the battery busbars. The main load busbar is via 3rd 300A T3 fuse connected to the same shunt too. All very short, so voltage drop is insignificant even with these loads, cost for 2x40cm 120qmm2 below 100Euro and t3 fuses are rated for real 1250A continuous.
inverter gets switched on and off by its remote so nothing additional gear between inverter and battery, just massive busbars, fuses and 2x120qmm2 cables. The rest is like a 200A continuous system that’s even separated in 2 main load and 1 charge bus bar. one must haves loads bus bar that can be switched to LFA and one rest. Like these loads are smaller, gear cheaper and voltage drop smaller too.
the legacy 12V switch board in the salon where all standard gear and bilge pumps get connected the 12V power goes via Dc-to-Dc12V 70A converter and voltage gets pushed to 15,5V so even pumps or everywhere else get I get min. 14V after voltage drops and 12V gear will run optimal.

 

[Atomvoyager]

I put a disconnect switch on every solar panel output before it goes to the MPPT. That makes troubleshooting and monitoring output low-cost and easy. You can also easily turn off some or all panels when away from the boat if you don't want the lithium to stay at 100% SOC. I don't put a switch between the MPPT and battery because you might damage the controller.

the Charge relay, will help me disconnect the PV to keep the LFP bank at the mid range. I only use the boat on weekends and the odd week when I am on holidays, and I have read that it is better in that case to keep the bank around 70% (although this might be wrong). So the idea is with the BMS to be able to cut the PV keeping the charge around 70%, and then the weeks when I am actively in the boat, I change the config back to 100%

 

[andreshs1]

Hi @Atomvoyager

yes, I have manual disconnect switches, but I am looking for something automated that could be controlled by the BMS.
Do you have any recommendations for relays?

cheers

 

[Horsefly]

Hi @Atomvoyager

yes, I have manual disconnect switches, but I am looking for something automated that could be controlled by the BMS.
Do you have any recommendations for relays?

cheers

I still don't understand what you are trying to do. You should be able to set your MPPT so that it maintains a float voltage at the battery, which will keep your LiFePO4 cells happy. If you are not there for many days on end and the MPPT is doing its part to keep your cells in float, why disconnect? There is no reason to disconnect the solar, and asking your BMS to do that just adds complication.

 

[andreshs1]

there are a number of reasons why you might need to cut off the charge from the MPPT based on alarms/triggers from the BMS, that is why Victron for instance has a remote on/off switch function. As this is not the case with the Epever, the relay is added between the solar panels and the MPPT, in order to disconnect the solar input before disconnecting the charge relay

cheers

 

[Horsefly]

there are a number of reasons why you might need to cut off the charge from the MPPT based on alarms/triggers from the BMS, that is why Victron for instance has a remote on/off switch function. As this is not the case with the Epever, the relay is added between the solar panels and the MPPT, in order to disconnect the solar input before disconnecting the charge relay

cheers

I just think you are overcomplicating it, but it's up to you. I don't think I have much else to contribute here.