LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

[dinghysailor]

I am a bit dissapointed that my Sterling Lite charger, nominally 30amps output, only seems to put out 25amps charging my 4S 160AH LiFePo bank at home, (with a short mains lead) - it's yet to be installed on the boat. That is measuring the current through the smartphone app with the '123 Electric' BMS, when I get my Victron battery monitor I should be able to double check the current with that. I would really have liked more than 30amps, maybe 40 or 50, but I chose the Sterling Lite because it is light and compact - this is for a lightweight trimaran so I am trying to minimise weight, also space for the installation is pretty tight. Does anyone have a sugestion for a charger with a LiFePo charge profile giving around 40 to 50 amps, preferably small and light? And available in the UK.

[CatNewBee]

Originally Posted by dinghysailor

I am a bit dissapointed that my Sterling Lite charger, nominally 30amps output, only seems to put out 25amps charging my 4S 160AH LiFePo bank at home, (with a short mains lead) - it's yet to be installed on the boat. That is measuring the current through the smartphone app with the '123 Electric' BMS, when I get my Victron battery monitor I should be able to double check the current with that. I would really have liked more than 30amps, maybe 40 or 50, but I chose the Sterling Lite because it is light and compact - this is for a lightweight trimaran so I am trying to minimise weight, also space for the installation is pretty tight. Does anyone have a sugestion for a charger with a LiFePo charge profile giving around 40 to 50 amps, preferably small and light? And available in the UK.

You can add a second one in parallel to get 50A.

[Dockhead]

Originally Posted by newhaul

sounds like I will be able to expect about 45 amps consistently then running my 1k genset for charging if it can handle the 50 amp charge consistently and sell off my 3.5k . Wish my little one was a 12v dc generator . As all it will be for is charging the bank.

Which 1kW generator -- Honda suitcase? I had one of those -- its continuous duty rating was actually 800 watts or something. And this kind of light duty gear does not really like operating near its rated capacity for long periods of time.



I'd be careful with that -- and would not be in a hurry to sell of a 3.5kW generator -- a NexGen?


DC generators are fine, but I only see one really big advantage of them -- the possibility of modulating power output by changing RPM. Constant speed operation makes AC generators very sensitive to operation of small loads -- why you see so many with polished bores, when main engines almost never come down with this condition.


If you don't have lead batteries there is hardly any reason to ever run a generator at a small percentage of its rated power, so I personally wouldn't pay much attention to this -- whatever is cheaper and/or more compact and/or simpler, be it DC or AC, I wouldn't care. Starting from a clean sheet, I would probably go with that smallest Northern Lights, or else build a super simple belt driven DC generator with a small propulsion engine and a great big alternator (Noelex has something like that on his last boat).



For me personally, and of course YMMV, priorities for generator selection would be:


1. Reliable
2. Reliable
3. Reliable

4. Simple and easy to service
5. Compact
6. Light
7. Cheap


Fuel economy and a couple of percent efficiency gain from not converting to DC wouldn't even be on the list, as the difference between best and worst efficiency is chump change compared to the cost and hassle of fixing a broken generator.



I would probably take a small marine propulsion engine (and perhaps not an industrial Kubota engine which needs to be marinized) and put it in a sturdy frame with a very large alternator on it like an Ecotec, or else two ordinary school bus alternators (for simplicity and serviceability sake), in any case with a very reliable drive system.



For simplicity's sake, manual speed control.


Then, all you have are ordinary alternators which are dead easy to repair yourself or at any third world auto-electric shop, without any proprietary electronics or control systems or any other such crap, and a simple marine diesel engine which you already know how to fix and which almost never breaks anyway.


Not dissing my lovely Kohler heavy duty low speed 6.5kW generator, which has given me 10 years of faithful service with only a small air leak in the fuel system for a problem in all those years. But if it ever does break -- there are all kinds of parts which you might need which are not practical to keep on board and which you might not even be able to figure out without a trained tech.



For remote cruising like I like, KISS rules everything for such devices. It is supremely important to be able to figure out any possible failure and deal with it using your own tools and resources. YMMV!

[newhaul]

Originally Posted by Dockhead

Which 1kW generator -- Honda suitcase? I had one of those -- its continuous duty rating was actually 800 watts or something. And this kind of light duty gear does not really like operating near its rated capacity for long periods of time.



I'd be careful with that -- and would not be in a hurry to sell of a 3.5kW generator -- a NexGen?
.



For remote cruising like I like, KISS rules everything for such devices. It is supremely important to be able to figure out any possible failure and deal with it using your own tools and resources. YMMV!

no to both . The 1k is a generic gasoline 1250 watt rated so 1k continuous output. ( same fuel as my dingy motor. ) uses about a pint of fuel per hour. )
The whole purpose of getting it was charging at anchor.
The 3.5 is actually a 3.7kw is a yanmar air cooled unit. ( was given to me it needed a new injection pump. $18 dollars later have a good running diesel genset. )

remember I'm just a 29x8 defender

[john61ct]

Originally Posted by newhaul

Wish my little one was a 12v dc generator . As all it will be for is charging the bank.

I like this concept:
https://www.affordabledcgenerators.com/the-jr-kit

[dinghysailor]

Originally Posted by CatNewBee

You can add a second one in parallel to get 50A.

Yes, I am considering doing that. Space is tight, I will have to reroute some pipework then take measurements and see what I can fit in. The Victron Phoenix 12/50 (50amps) might be another possiblity, but a little bigger than two of the Sterling ones, are there others I could consider?

[CatNewBee]

I do not know your local market situation. Victron is for sure one of the brands, that are very flexible and configurable with the settings.

[gscriba]

So badly wanting to take the plunge, but I'm definitely feeling a bit overwhelmed.
I have the perfect space for 700 ah Winstons for a 12 volt system.
Received quotes for the 4 x 700 ah cells, Simarine's battery monitoring system and REC Active BMS. I've thought through and planned the install. Two things (at least) are holding me back...
1. How to initially balance the cells on the boat, without a garage/work bench/access to any of the equipment suggested in previous posts?
2. How to have the REC Active BMS configured from the manufacturer with regards to the Input/Output and CAN communication configuration (for those who have ordered and are using the REC BMS and have completed their "Active BMS Requirements Document", you will be familiar with this document).

Suggestions regarding the above bearing in mind I live aboard and would be making the transition from LA to LFP as smoothly (read, least disruptive) as possible.

Really appreciate all the input/education/visual examples provided by those of you using your systems as house banks. Thank you so much for all the time and effort.

[andyalford]

Originally Posted by gscriba

So badly wanting to take the plunge, but I'm definitely feeling a bit overwhelmed.
I have the perfect space for 700 ah Winstons for a 12 volt system.
Received quotes for the 4 x 700 ah cells, Simarine's battery monitoring system and REC Active BMS. I've thought through and planned the install. Two things (at least) are holding me back...
1. How to initially balance the cells on the boat, without a garage/work bench/access to any of the equipment suggested in previous posts?
2. How to have the REC Active BMS configured from the manufacturer with regards to the Input/Output and CAN communication configuration (for those who have ordered and are using the REC BMS and have completed their "Active BMS Requirements Document", you will be familiar with this document).

Suggestions regarding the above bearing in mind I live aboard and would be making the transition from LA to LFP as smoothly (read, least disruptive) as possible.

Really appreciate all the input/education/visual examples provided by those of you using your systems as house banks. Thank you so much for all the time and effort.

Ok, well you have an almost identical system to me. And I would say DO NOT HESITATE. It is amazing.

I will post full details when I get everything finished, but for now....

4x 700AHA winstons
- I got 4 with consequtive numbers and a factory test of 745 Ah.
- When I measured it with a slow discharge test I got 770 Ah out of them.
- They are monsters though, 31Kg I think, and long and difficult to manoeuvre into a space,
- I learnt to use sailing gloves as the yellow ribbed plastic is really sharp

Balancing on the boat
- I tried them for a few days, and they were ok but not quite perfect balance
- so I charged them to approx 3.50V each cell (14.0V) using the engine alternator
- then I pulled them back out (quite an effort) and connected in parallel (4 cells at 3.50V)
- I had purchased a DROK buck boost 12V to variable 0-60V power supply
- https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
- I connected this at 3.55V with a current around 3-4 Amps, reducing until 0.2 A (it took 12+ hours)
- Then I increased to 3.60V, it started around 2-3 amps, reducing until 0.2 A (another 12+ hours)
- I had some time on my hands, so I set it to 3.65V, it started at 2 Amps, reducing more quickly to <0.1 A (about 6 hours)
- They are now within 4-5 mV of each other and I have cycled them up and down the full SOC range

REC-ABMS
- definitely get the CAN version, assuming you have devices which accept this input (e.g. Victron MPPT controller / MultiPlus inverter-charger)
- it is the logical way to control LFP, as it ramps down the current as the charge completes
- you should buy the PC interface and control the parameters yourself
- initially I had it set for 3.45-3.58 V top balancing to test the batteries were ok
- but now, I have run a few weeks and looked at my charge / discharge curve and chosen 3.35-3.38V as top balance, leaving the top 5-8% SOC unused and keeping 'out of the knees'
- I am still playing with it, and will continue to adjust it
- The Victron web portal VRM is superbly useful for viewing graphs of your usage, and immediately you can see what is happening
- BMV712 battery monitor is a bit of a waste of money, but you need a shunt anyway, so I guess it is ok, and a little redundancy
- be aware that the CAN takes complete control of MPPT controllers and chargers, so you don't need anything fancy with 'charge programmes' as the can just says max current and max voltage, then a reducing current ramped to top balance whilst REC-ABMS tried to balance the cells

Which BMS?
- If you are short on dosh, or just want to experiment before you are committed
- Buy consequtive numbered Winston cells and a $30 ISDT BG-8S colour display
- You will find that the cells do not need monitoring and do not go out of balance
- I am ok that I spent $500 on REC-ABMS, and another $500 on 3x ML-RBS 7700 contactors, but I don't think it will ever get used.

ALSO
- Buy a Raspberry Pi and install VENUS OS for $200 with the 7" Official Raspberry Pi LCD and the required number of USB - VE.Direct / MK3 converters. Absolutely amazing, cannot say enough good things about Victron and the fact they made this Open Source and free. This gives you a CCGX but with a 7" touch screen


Then, I think you could decide after some time, what you think you really need. But be prepared for a profound change in your liveaboard experience once you get LFP. My boat is 30 years old but overnight all the systems are working perfectly again, pumps are efficient, breakers operate perfectly, light are bright and constant, the alternator is working well (but I need a bigger one soon.)

DO IT. Sorry for lack of detail. PM me for more details, and I promise to post pictures at some point in the future. Andy

[CatNewBee]

Ideally you need a lab power supply where you can adjust voltage and current and a tough battery charger (you probably already have).

The cells arrive almost empty, charging them can take over a week with a regular battery charger.

They say, you have to equalise charge the cells before using them in a battery. This is very hard to achieve and takes long if you do not have a 4V high current charger.

Here is a work around.

Build temporary a 12V battery off the cells and charge the battery with a regular charger. Watch the cell voltages carefully. Lets say, you have a 30A charger, it will take over 24h to charge 700Ah, a 10A charger would need need 3 days. Stop charging when the first cell reaches 3.5...3.6V.
You can use a car lightbulb or some other load on that cell only while charging further to divert part of the current and allow the other cells to charge. Try to get all the cells around 3.5...3.6 Volts.

Then dissamble the battery, connect all cells in parallel (all plusses connected to each other on one side, all minusses on the other by the bridge elements) to make a big 3.4V (resting voltage after some time charging has stopped) battery.

The cells will be different by some mV to 10s of mV, no big deal. Then use the lab power supply, set it to maximum current an set the voltage to 4.0V, connect the battery and charge, the voltage will drop when you connect the battery. The 4.0V are only a safety setting to not exceed the maximum recommended initialization if you are not around. Assume, you have to charge another 400...500Ah until you reach the right voltage, even if you have been at 3.6V before (around 90%, there are still 70...100Ah per cell to the initial charge top, and 4 cells in parallel mean 4 times the capacity at 4V, so 280...400Ah to be charged at 4V), your lab Power supply would deliver 10..15A usually, expect a charge duration of several days until you reach 3.8V, you not need to go higher all the way to 4.0 even it is recommended by the manufacturer, but dont stop lower. Once you have the pack at 3.8V with this low charge current, the cells will be OK, disconnect the charger, but let the pack rest for another 2 days connected to balance out the charge, the voltage will drop probably back to 3.6...3.7V without a charge source connected.

You can now remove the bridges and build yout 12V battery, that is now fully charged and balanced. Connect the REC bms and the shunt for monitoring, connect a inverter to the pack and discharge it with some high load, like a heater or similar and check the capacity, stop discharging when the first cell hits 2.9V under load. You will be around 20% SOC then, the cell will quickly recover to 3.1..3.2V. You will probably have drawn around 700...800Ah at this point with fresh initialized and fully charged cells. Connect your charger again and charge the pack full to 14.4V (90.. 95% SOC) note the AH charged, you will probably read about 70...100Ah left to full, this is because you not charge up to 3.65V, and the battery was initialized with a higher voltage), reset the 100% SOC and the Ah counter there, this is the level you consider full in the future.

You can use your BMS when charging and discharging to control the process and test the BMS and the interfaces.

If everything works, install the battery and all control gear into the boat permanently, use NoAlOx at the contacts, use a torque wrench to tighten the connectors, use all poles with bridges to allow a low resistaance connection between the cells, 700AH cells have 2 positives and 2 negatives, so you need 6 bridges for the pack. It adds redundancy.

Clean the contacts carefully from any oxydation and dirt before assembly, add a few NoAlOx on the surface put the sense connector on top, then a stainless washer, a stainless spring ring or spring washer above and then the stainless screwof the right length, torque the connection to the required value. Do not overtorque it, and dont make it too loose. You need the best connection possible between the bridge and the battery pole and it must be reliable for a long time.

Install everything and test it then. Fire up your inverter and put the maximum load on what it accepts. Check all sonnections and cabling fot heat, they will get warm, but should never get hot. If there are spots with heat, redo the connection, the crimping of the wire or whatever causes the trouble. You may need to increase wire crossection or double the wiring to the inverter. Check also the fuses and fuse holders. Sometimes they are crap.

After everything is OK, seal all bridges and connections with liquid rubber to keep moisture out and prevent shorts if a tool falls onto a connection. Isolate and cover all screws and bars etc.

Isolate your wrench when working on the poles too...

Good luck, and have fun!

[gscriba]

Thank you, Yachtshah and CNB!! Such a huge help and confidence boost. I’m trying to get a better understanding of how the In/outputs on the REC-ABMS are configured. Also, any thoughts about the Simarine battery monitor?
Many thanks, once again.

[CatNewBee]

Originally Posted by gscriba

Thank you, Yachtshah and CNB!! Such a huge help and confidence boost. I’m trying to get a better understanding of how the In/outputs on the REC-ABMS are configured. Also, any thoughts about the Simarine battery monitor?
Many thanks, once again.

Mine is now 2.5yo, but it is easy to explain. The REC ABMS has a water protected connector and a cabling set you can buy with different options. The unit is always the same. I would recommend to order the cable too, instead of sourcing the connector and making your own, the wiring is well done, the wires and isolations are of a good quality and well labelled, so easy to set up.

On the contacts there are 2 NO/NC relay contacts available, means a contact switches between two outputs, one is NC (normally closed) the other is NO (normally open) when the relay swithes, the first opens and the second closes. They can carry loads of one Amp. The first relay is for allow charging, the second is for allow discharging. (according to the programmed cell voltages etc.) Normally both are off, after booting up, both relays flip and enable the battery operations. Additionally there are two open drain outputs of opto couplers. Means inside is a.led and a photo transistor, when the led inside the circuit lights up, the transistor allows current flow the pins can be used in your own circuit independent (galvanically isolated) from the BMS, current is limited to 200mA. They both are usually programmed to switch with the relays, but as I did, I asked REC / Tine for custom programming with different variables, so I can have two independent settings for charge and two for discharge, I use the relays with solenoids to disconnect the busses and protect the cells as last line of defense for ovr voltage and deep discharge, while I use the optocouplers for signalling by the 2 wire BMS macro to my Victron Quattro at different set points, mainly to force it to float from the BMS when the battery is full without dropping all other charge sources and also disabling the inverter early by keeping 20% usable capacity for the 12V board circuits without disconnecting the loads bus.

The REC has also a CAN interface, that can be used to communicate to other CAN devices, default settings are CAN, opto coupler and relays work at the same time on the same settings. If you want / need different settings, you must ask for a custom firmware. To be able to configure any parameter or make a firmware update / install a fix, you need the computer interface and the software, otherwise you get the unit pre-set in the factory and must ship it there for updates or fixes. So I do recommend to buy the software with the USB interface.

Rumors are the new REC has BT on board, cannot comment on that, mine is older. I do have the optional wired display and like it, but maybe the BT is a good replacement for it.

Besides this outputs there are one or optional two temp sensors pre wired, so you can measure the cell tempertures, placing one between cell 1 and 2 and the second between 3 and 4. If one cell runs off, the BMS will react.

Additionally there are 5 voltage sense wires, minus, plus cell one, plus cell 2, plus cell 3, plus cell 4,

Another 2 wires are for the shunt to measure the current, you can buy the REC shunt or use your own, e.g. from a Victron BMV 712. It must be a resistive shunt, you can configure it with the software.

Then there are a serial interface (DB9) for programming or connecting the display and a CAN bus interface (DB9) . The one is a male connector, the other a female.

There is also a switch (2 wires) to turn off the BMS (and the battery.) all this is already pre-wired. You have to ask for a full wiring, otherwise the relays will be NO wired, the NC wires are considered optional.

One user in the forum has recently reported, that his BMS was rebooting all the time, he has ordered the CAN bus config for Victron. Resolution was, the bus must be connected when configured, otherwise the unit reboots. I have on my unit the CAN connection too, but not configured for Victron (older firmware) and never had such trouble. But if you not intent to use the CAN, you probably should ask for a config that keeps away from rebooting while waiting for the bus.

Thats all about it.

No idea about Simarine.

[john61ct]

Simarine Pico is a fantastic all-in-one systems monitor with a lot of different functions.

However, Battery Monitor as in SoC estimation is less accurate than most competitors.

For LFP my reco's are Victron BMV-712 and Link Pro

Sterling, Magnum, Bogart Trimetric, but all of them do take some work
https://marinehowto.com/programming-a-battery-monitor/

Maybe SG-200 will prove better, still very new afaic.

[gscriba]

Just want I needed, CNB. Thanks for taking the time to share all those details. Seriously, very very helpful. I am so excited. I've been watching, reading, learning for at least 4 years; just waiting for prices to drop and time for the batteries to prove themselves appropriate for the marine application.

John, are you using the Simarine Pico? I'm looking for more details from someone who has installed one and is using it.

[john61ct]

No, but you can find them here

http://www.cruisersforum.com/forums/...ws-194848.html

http://www.cruisersforum.com/forums/...re-223222.html

http://www.cruisersforum.com/forums/...co-192131.html

http://www.cruisersforum.com/forums/...ml#post2500668

Bruce @ OceanPlanet did some benchmark comparison testing, he may discuss if you email him.

Apparently he gave them feedback that helped with improving their firmware in subsequent releases.