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

[ebaugh]

Originally Posted by Lagoon4us

Are these an option to run one charger whilst motoring? Then the same charger by shore or genset???

http://www.meps.com/New_Site/Documen...ochure-kVA.pdf

I'm not sure if your boat is 50 cycle or 60 cycle. The Victron inverter chargers can use some propulsion engine mounted AC generators in the same load sharing fashion. Light AC loads then you can charge, heavier loads add the inverter capability to the engine generator. We have 2 full size gensets, but that's probably not possible on many sailboats, so I like the idea of redundancy of 2 sources of power, especially with an electric galley. Here is a Victron application note that identifies two other manufacturers of engine driven AC power systems, but both are 50 cycle power:

http://www.victronenergy.com/upload/...20rev%2001.pdf

[Lagoon4us]

From memory Aussie is 50 hertz and 220/240 i'll go through the aircon/desal etc and check.. Poer generated would have to be kept separate i don't believe synchronisation would be possible?

[ebaugh]

Originally Posted by Lagoon4us

From memory Aussie is 50 hertz and 220/240 i'll go through the aircon/desal etc and check.. Poer generated would have to be kept separate i don't believe synchronisation would be possible?

Victron pioneered synchronizing inverters to other AC power sources. I know a couple of Manufacturers are doing load sharing on commercial power now, but Victron does it with gensets. It's pretty nifty.

[goboatingnow]

I would question the need for any sort of " centre fielder " dual alternator controller. Since lithiums have a reasonable linear recharge. The two alternators will merely see a low impedance load and both will drive as hard as possible. Ie the input impedance of the battery is much much lower then the output impedance of the alternator controllers. The trick will be preventing the alts from burning up

There is no problem with alternators being reduced fast as long something is left in the circuit. A make before break crossover relay and a power resistor would do. But as laid out below its not neccessary anyway.

I'd also question the need for low or high voltage disconnects. Alarms yes, actual disconnects no why

(A) since most boats will struggle to even charge close to 1C , damage is unlikely to occur.

(b) most standard boat charging devices will not actually ever reach HVC as that voltage is quite high .

(C) the last thing I'd want is a sudden , unexpected and total loss of battery power due to a cutoff disconnect. I'd prefer the risk" of damage " ( it is only a risk )

(D) the LVC point is in effect well below 12v , everything on the boat will already be screaming low battery long before an LVC event. It's not like you will not know this.

At sub 1C charging regimes, I'd even forget automatic cell balancing. All a BMS needs to do is monitor and alarm on cell voltage . Do your balancing manually and in practice other then initial balancing , it's rarely need in typical boat domestic systems with both <1 C charge and discharge regimes.

Dave

[ebaugh]

Originally Posted by goboatingnow

I would question the need for any sort of " centre fielder " dual alternator controller. Since lithiums have a reasonable linear recharge. The two alternators will merely see a low impedance load and both will drive as hard as possible. Ie the input impedance of the battery is much much lower then the output impedance of the alternator controllers. The trick will be preventing the alts from burning up

There is no problem with alternators being reduced fast as long something is left in the circuit. A make before break crossover relay and a power resistor would do. But as laid out below its not neccessary anyway.

I'd also question the need for low or high voltage disconnects. Alarms yes, actual disconnects no why

(A) since most boats will struggle to even charge close to 1C , damage is unlikely to occur.

(b) most standard boat charging devices will not actually ever reach HVC as that voltage is quite high .

(C) the last thing I'd want is a sudden , unexpected and total loss of battery power due to a cutoff disconnect. I'd prefer the risk" of damage " ( it is only a risk )

(D) the LVC point is in effect well below 12v , everything on the boat will already be screaming low battery long before an LVC event. It's not like you will not know this.

At sub 1C charging regimes, I'd even forget automatic cell balancing. All a BMS needs to do is monitor and alarm on cell voltage . Do your balancing manually and in practice other then initial balancing , it's rarely need in typical boat domestic systems with both <1 C charge and discharge regimes.

Dave

I agree LVC is not a huge issue other than protecting the battery investment. But HVC is another issue.

Above 3.6 V per cell they start to generate heat. At our admittedly low charge rates, they are stuffed full at this point. Beyond that, heat generation starts. Enough heat, and they vent. Unless there is a good battery management system, there will eventually be disparity between the cells at this top end. So the simple math says 3.6x4 is 14.4V and no issue. But the disparity will force the high cell over before the low cells catch up. So problems can occur, I think starting about 14.2V, easily reachable.

Now an alarm works. If you are onboard. And if you are the one who designed and installed the system. But what about if you sell the boat?

Even on your boat, do you want to leave your charging systems on at dock? Or the solar system on at anchor while ashore. No one to handle the alarm should it go off. How sound do you sleep?

I agree this is an unlikely scenario, but it can happen. You only need a failure of one of the many charging systems. And again, even more unlikely, it could lead to more than damaged batteries.

How much is a solenoid? Pretty cheap if you have an alarm. YMMV, but I think it's needed.

[goboatingnow]

Originally Posted by ebaugh

I agree LVC is not a huge issue other than protecting the battery investment. But HVC is another issue.

Above 3.6 V per cell they start to generate heat. At our admittedly low charge rates, they are stuffed full at this point. Beyond that, heat generation starts. Enough heat, and they vent. Unless there is a good battery management system, there will eventually be disparity between the cells at this top end. So the simple math says 3.6x4 is 14.4V and no issue. But the disparity will force the high cell over before the low cells catch up. So problems can occur, I think starting about 14.2V, easily reachable.

Now an alarm works. If you are onboard. And if you are the one who designed and installed the system. But what about if you sell the boat?

Even on your boat, do you want to leave your charging systems on at dock? Or the solar system on at anchor while ashore. No one to handle the alarm should it go off. How sound do you sleep?

I agree this is an unlikely scenario, but it can happen. You only need a failure of one of the many charging systems. And again, even more unlikely, it could lead to more than damaged batteries.

How much is a solenoid? Pretty cheap if you have an alarm. YMMV, but I think it's needed.

Winston batteries give max charging at 4V at 25degrees C ambient. Even accepting the more commonly used 3.7v as max charging this gives HVC at 14.8-16v, This is typically above ( or can be set to be above) most of the charging sources on a boat. , particularly alternators. Equally experience has shown that limited excursions above these voltages does not cause significant damage.

It is worth pointing out that similar and even worst catastrophic damage can occur to LA cells subjected to prolonged high voltage & currents, as might be speculated in gross fault scenarios. Yet HVC cutoffs are very rare.

The fact is leaving aside the HVC alternator disconnect issue, which is easily solved. I personally would never want an unpredicted and total loss of electrical power, which could result from HVC/LVC systems. I don't believe their is any more risk than exists today with LA equipment. In fact my own experience with LFP tech. Is that it is more robust then LA, and is capable of more charging and discharging abuse. HVC/LVC and balancing BMS came out of the early EV experience often with much more sensitive and dangerous Li technology. In these cases they were dealing with multi C charge and discharge rates , situations that do not exist on a typical boat. ( leaving aside electric propelled boats etc )

As I said it is useful to monitor cell voltage to detect potential out of balance situations which COULD generate cell HV events. However all the user experiences here and elsewhere indicate that in low C environments, top cell balance issues are very rarely a problem ( if anything in my experience cells converge ). Furthermore high current auto balance systems are few and far between ( and costly )in my experience a simple alarm is sufficient.

Taking your unattended boat scenario. Firstly that will rarely include alternators. For modern battery chargers the reliability is equally as good as a potential HVC system, hence no additional protection is really provided., Solar in my opinion should be used in LFP system by way of dc-dc systems like MPPT units and never PWM ,hence again the fault protection is as error prone as the controller.

The fact is HVC protection uses electronics to protect other electronics from damaging your batteries. It's a debatable protection.

HVC and LVC thinking is (a) really a reaction to the cost of the batteries, rather then a real scientific requirement and (b) a carry over from other Li technologies and high C EV environments and the resulting early catastrophes.

Ps the solenoid to do proper Li disconnect under severe fault conditions is very expensive.

Dave

[ebaugh]

Originally Posted by goboatingnow

Winston batteries give max charging at 4V at 25degrees C ambient. Even accepting the more commonly used 3.7v as max charging this gives HVC at 14.8-16v, This is typically above ( or can be set to be above) most of the charging sources on a boat. , particularly alternators. Equally experience has shown that limited excursions above these voltages does not cause significant damage.

It is worth pointing out that similar and even worst catastrophic damage can occur to LA cells subjected to prolonged high voltage & currents, as might be speculated in gross fault scenarios. Yet HVC cutoffs are very rare.

The fact is leaving aside the HVC alternator disconnect issue, which is easily solved. I personally would never want an unpredicted and total loss of electrical power, which could result from HVC/LVC systems. I don't believe their is any more risk than exists today with LA equipment. In fact my own experience with LFP tech. Is that it is more robust then LA, and is capable of more charging and discharging abuse. HVC/LVC and balancing BMS came out of the early EV experience often with much more sensitive and dangerous Li technology. In these cases they were dealing with multi C charge and discharge rates , situations that do not exist on a typical boat. ( leaving aside electric propelled boats etc )

As I said it is useful to monitor cell voltage to detect potential out of balance situations which COULD generate cell HV events. However all the user experiences here and elsewhere indicate that in low C environments, top cell balance issues are very rarely a problem ( if anything in my experience cells converge ). Furthermore high current auto balance systems are few and far between ( and costly )in my experience a simple alarm is sufficient.

Taking your unattended boat scenario. Firstly that will rarely include alternators. For modern battery chargers the reliability is equally as good as a potential HVC system, hence no additional protection is really provided., Solar in my opinion should be used in LFP system by way of dc-dc systems like MPPT units and never PWM ,hence again the fault protection is as error prone as the controller.

The fact is HVC protection uses electronics to protect other electronics from damaging your batteries. It's a debatable protection.

HVC and LVC thinking is (a) really a reaction to the cost of the batteries, rather then a real scientific requirement and (b) a carry over from other Li technologies and high C EV environments and the resulting early catastrophes.

Ps the solenoid to do proper Li disconnect under severe fault conditions is very expensive.

Dave

Dave,

I understand your thinking here. And I agree with most of it. But a couple of observations:

1) Not all the LiFePO4 cells are rated like the Winston's. I'm not sure the yttrium addition makes this difference or not. But other cells have lower limits, and I'm not convinced you really want to treat Winston's different based on the rating.

2) The cost to do the disconnect is not high. CellLog8, sensitive relay, solenoid, and some wire. Under $200. I am not suggesting a full blown BMS with balancing is needed. I agree that this solution is not more reliable than the charging systems, but what matters is; now there must be two simultaneous failures, a very unlikely event.

3) LiFePO4 is undoubtably the safest, most stable Li out there, but I think we still have more to learn. I'd rather err on the safest side when in doubt until there is a much broader base of experience.

Best Bob

[Lagoon4us]

I totally appreciate the depth of advice in this thread it's a goldmine for someone wishing to do a project like mine with solid advice, i thank you guy's much!

NOW:-
My thoughts are because this boat already has an installation of 2 lead acids one for each main engine start (able to be connected to each other) and a lead acid in the bow for the thruster that are in very good condition i shall leave that as a separate circuit chargeable by the existing Dolphin 80 amp 240 volt charger, 4 small solar panels/morningstar controller and monitor and the two OEM Alternators on the Volvo mains.

My thinking is to isolate this from the house system as it is working well and has redundancy inbuilt as it presently stands. Surely this in itself is superior or equal to most yachts/boats/systems. I realise there is argument for one bank BUT i think my logic is strong.

NOW the house system will be the 16 x 160 ampere Winstons that will be chargeable by the following.
1) 850 watts of solar array with an appropriate MPPT Controller.
2) A new Victron charger set for Lithiums only.
3) A cruise alternator on the Stb main engine to run any 240 volt demand.
4) Shore power 240 volt that exists but with the addition of an isolation transformer.
5) Our already installed Paguro 6Kva gen-set.

Now we currently have a shore power/genset isolating switch that removes the possibility of engaging two sources of 240 volt at once and the inherent problems of synchronisation etc SO i need a 3 way switch/selector so only one source can be selected. Any suggestions?

Our installed inverter is a 2000 watt Perfect Power by WAECO it seems to be intelligent enough to not try to synchronise so may not be an issue?

Terry/Dave/Bob/John is my logic sound? Please comment

[ebaugh]

Originally Posted by Lagoon4us

I totally appreciate the depth of advice in this thread it's a goldmine for someone wishing to do a project like mine with solid advice, i thank you guy's much!

2) A new Victron charger set for Lithiums only.

Terry/Dave/Bob/John is my logic sound? Please comment

Is this an inverter charger or just a charger? The load sharing part previously mentioned needs the inverter charger.

[hellosailor]

"I'd also question the need for low or high voltage disconnects. Alarms yes, actual disconnects no why"

Dave, as mentioned an alarm just fetches the local wetware, assuming there's one around. A disconnect can prevent battery bank damage, charger damage, explosion or fire. IF that disconnect blows an alternator, that's either poor engineering or an intentional design choice. I'd call a "sacrificial alternator" a poor design choice, since an alternator is capable of being effectively shut down by zeroing the exciter current, even if it is still rotating. Of course that's assuming there's a real alternator, not a generator, so maybe the "sacrificial alternator" is a one-size-fits-all type of solution.

It is sadly 'interesting' to keep hearing after all these years that various lithium battery makers can't agree on whether a BMS is necessary or just an expensive waste. Put two of 'em in the same room, and it sounds just like a Presidential Debate.

[Lagoon4us]

Originally Posted by ebaugh

Is this an inverter charger or just a charger? The load sharing part previously mentioned needs the inverter charger.

Our 240 req's are as follows.
1) The planned respective 2 chargers. 1 for lead acids 1 for Lithium. In practice the lead acids will require minimal charging.

2) Hot plate only on shore power/paguro gen set/planned cruise alternator.

3) Air con on shore power/paguro gen set/ planned cruise alternator.

4) De-sal on any 240 source including existing inverter.

5) Small white goods usually on inverter so no engine start up is required.

Do i need a load share or do you think it complicates things? Cheers

[ebaugh]

Originally Posted by hellosailor

"
It is sadly 'interesting' to keep hearing after all these years that various lithium battery makers can't agree on whether a BMS is necessary or just an expensive waste. Put two of 'em in the same room, and it sounds just like a Presidential Debate.

LOL....What is a BMS? If it includes automated balancing, then no. I'm not sure there are even effective options out there for DIY installations. If it means voltage monitoring with an automated disconnect, I think yes. But it is subject to a reasonable debate.

[Hyprdrv]

I've seen this as well
BMS= Battery Management System
BMS= Battery Monitoring system
2 totally different things

Lagoon, what starts your Genset?

Steve in Solomons MD

[Lagoon4us]

Originally Posted by Hyprdrv

I've seen this as well
BMS= Battery Management System
BMS= Battery Monitoring system
2 totally different things

Lagoon, what starts your Genset?

Steve in Solomons MD

Has it's own independent start battery, when we bought the boat it was a bit sluggish so simply pulled the dinghy battery out and swapped. There is a small 240volt charger to top it up if powers available, battery city methinks!!!!!

Frank

[Hyprdrv]

The reason I asked was Lagoon was wiring the genset into the House bank, not a good idea with the drawdown while Electronics where runing.

Steve in Solomons MD