Some Electrics questions

[mattonthesea]

As our electrical system is quite old and has clearly been constructed on an ad-hoc basis I am planning to redo the charging and battery parts. I have already re-wired the switch panel and associated fuses. I have a standard alternator on a Penta 2020. We have 130W of solar PV. The only big power hungry load is the fridge. Otherwise it is standard nav equipment, lights and phones/laptops etc. We also have a Torquedo to charge. I have looked into it and I think I want to go down the LifePo4 route for domestic use. Our pattern is to cruise for three months where we anchor off for up to a week at a time and use the dinghy to go ashore; we then spend a couple of nights in harbour. Obviously, this pattern is subject to external influences. We will be in Northern Europe for the foreseeable but...

Qu 1: at the moment we have 24Ah domestic which is not quite enough when using 70% as minimum discharge limit. If we went for 150 LifePo4 Ah would this add about 50% more useable Ah?

Qu2: If we used a B2B option with Lead Acid Starter Battery then would the alternator regulator be able to cope with the surge if the BMS broke the domestic charging circuit?

Qu3: So far I've looked at Victron and Sterling. The Victron has an galvanic isolating option and is cheaper but the Sterling has a PV input option. (as a further question I have wondered why they don't do an integrated, all-in-one shore power charger, B2B, PV /wind gen input etc. One box ). Sterling batteries come with a BMS whereas Victron don't; however, the Victron BMS is future proofed in that it can be set for multiple batteries. I'm not bothered about bluetooth connections so, apart from this, does anyone have any other issues with either manufacturer/system etc?

Qu4: If we upped to 250W PV on goal posts would this give us enough to keep reasonably topped up? I know this is a piece of string but wondered about others' experiences in this part of Europe.

Qu5: If this all worked would be able to charge the Torquedo battery more efficiently? Our inverter can't cope so we charge at 1% per hour from 12V presently via the switch panel. Is there a way of faster charging from a LifePo4 battery?

Qu6: am I missing anything?

Answers on a postcard!

Thanks

M

 

[PaulRainbow]

Qu6: am I missing anything?

No matter now many ah of battery capacity you fit, you still have to replace what you use. I don't see the need for stupidly priced and over complicated Lithium installs in the vast majority of cases.

If you were to be away from shore power for, say, two weeks, during that two weeks you will need to somehow generate the electricity that you use. You actually need to generate it in the time it takes your batteries to deplete to an acceptable level. I would start off by working out how much you'll use in a 48hr period and fitting enough batteries to be able to supply this, without any charging (cloudy days away from shore power). Then, fit as much solar as you can sensibly accommodate, hopefully at least enough to match your daily needs.

I spent 6 years living full time on my last boat with 4 x Trojan T105s and 200w of solar. During the Summer i rarely used shore power to charge the batteries. Fridge running 24x7, TV, soundbar, phone and laptop chargers, electric toilet, electric water pumps etc.

 

[SteveGorst]

Qu5: If this all worked would be able to charge the Torquedo battery more efficiently? Our inverter can't cope so we charge at 1% per hour from 12V presently via the switch panel.

We use a 1000 watt continuous power inverter and charge our ePropulsion battery while the engine is running. I've yet to be at anchor long enough to seriously deplete it but have given it a short 30 minute charge from the inverter while the engine is not running and nothing untoward happened apart from the battery losing some charge. The solar panels have no chance of keeping up with the current that is drawn but if you charge in the morning they have time to recover. I just use standard leisure batteries with a 140 watt solar panel so I'm afraid I cant comment on the LifePo4 battery.

 

[mattonthesea]

No matter now many ah of battery capacity you fit, you still have to replace what you use. I don't see the need for stupidly priced and over complicated Lithium installs in the vast majority of cases.

If you were to be away from shore power for, say, two weeks, during that two weeks you will need to somehow generate the electricity that you use. You actually need to generate it in the time it takes your batteries to deplete to an acceptable level. I would start off by working out how much you'll use in a 48hr period and fitting enough batteries to be able to supply this, without any charging (cloudy days away from shore power). Then, fit as much solar as you can sensibly accommodate, hopefully at least enough to match your daily needs.

I spent 6 years living full time on my last boat with 4 x Trojan T105s and 200w of solar. During the Summer i rarely used shore power to charge the batteries. Fridge running 24x7, TV, soundbar, phone and laptop chargers, electric toilet, electric water pumps etc.

Thanks Paul, that's useful. Where were you living on your boat?

I have done the calcs about power use but I wanted to get a feel of the reality. When I first installed a central heating system in a house I did the calcs extensively. After one winter I added extra radiators or bigger ones in most rooms!

Re the lifePo4 - yes I will keep a close eye on cost/reward but several of the bits are close to needing replacement so I'm thinking of future proofing in stages.

 

[KompetentKrew]

There are now some varieties of AGM which might be worth looking at, which allow deeper discharging without the hassle of a lithium install.

E.g. Victron's Lead Carbon AGM. This particular model is horrendously expensive though.

 

[PaulRainbow]

Thanks Paul, that's useful. Where were you living on your boat?

I have done the calcs about power use but I wanted to get a feel of the reality. When I first installed a central heating system in a house I did the calcs extensively. After one winter I added extra radiators or bigger ones in most rooms!

Re the lifePo4 - yes I will keep a close eye on cost/reward but several of the bits are close to needing replacement so I'm thinking of future proofing in stages.

East coast UK.

 

[vyv_cox]

Not quite comparable as we are in Greece. We currently have a domestic bank of 3 X 105 Ah open cell lead acid batteries, Winner Solar, that are excellent. We have 125 watts of solar. PWM regulator. Fridge runs 24/7 drawing 3-4 amps for about 33% of the time. Even now, past the equinox and on partially cloudy days we are totally self sufficient for power at anchor.

 

[Supertramp]

Re the Torqeedo you don't need to use the inverter. You can make or buy a 12v charge cable and use the normal charging socket. Take care to get the +/- terminals the right way round. The Torqeedo electrics are pretty smart but not to reversed polarity.

Interested that you use a 70% minimum discharge. Is there a recommended figure to work to?

 

[Tranona]

Thanks Paul, that's useful. Where were you living on your boat?

I have done the calcs about power use but I wanted to get a feel of the reality. When I first installed a central heating system in a house I did the calcs extensively. After one winter I added extra radiators or bigger ones in most rooms!

Re the lifePo4 - yes I will keep a close eye on cost/reward but several of the bits are close to needing replacement so I'm thinking of future proofing in stages.

From what you say, you are a long way from being able to justify LifePo4. You have relatively modest demands and arguably a bit short of power generation, although a coup[le of nights on shorepower will mean that you start each off grid session with fully charged batteries. As you suggested in the first post the obvious thing to do is increase your "buffer" capacity to cope with the possible daily variability in charging capacity.

There is a lot of hype about Lithium - not difficult to identify what the benefits are, but little attention is paid to whether you can actually gain from those benefits. For example, you are not able to benefit from the high charge acceptance rates because you don't use a generator, or get into a position where the engine is charging an almost flat battery. Your challenge is identifying the range of deficit between your daily usage and generation then sizing your buffer to cope with it. Pretty sure you will be able to do that comfortably with 3-400Ah of LAs, particularly if you go AGM. That will "future proof" you with a life of probably 10 years unless you change tack and kit your boat out for massively increased electrical consumption!

 

[Pete7]

We have a 120Ah Sterling Lithium (LFP) battery wired in parallel to two 85Ah Trojan flooded lead acid (FLA) batteries. This is charged by 300w of solar. In good sunny conditions this will run all domestics including the fridge etc, but also allow the use of a small 1Kw electric kettle, toaster and induction hob for a 50/50% electric / gas cooking. In okay conditions we are a little bit short of solar say 30Ah each day, so can survive a couple of days before needing to charge via the Victron Orion DC>DC charger.

During 3 weeks in Aug 21 we only used the Orion twice to charge when it was foggy rain for a couple of days. We saw 60w from the panel even in the rain at mid day. This years cruise in September was a bit more difficult with lots of strong wind, clouds and rain so we hid in Weymouth and used the shore power to supplement extra demands by going 100% electric cooking, including baking.

In use when the kettle is switched on, the LFP provides about 90% of the power, the FLA 10% at night, for a total demand of 75A. During the day, solar provides maximum power first before the batteries to power the inverter and kettle, so the draw is 60A or so. The only reason we have two Trojan FLAs is they were the original house bank. Once they expire I will probably replace them with a single 100Ah AGM battery which is a good match to LFP. We disconnect the LFP when not on board to avoid float charging leaving the FLA to run the bilge pump.

The Victron Orion gets hot, very hot. Ours is mounted on the nav seat with a 3" hole behind it. Even so we have recorded 59c after an hours use. There is a reason for those big fins on the back. So mount it somewhere with good ventilation. I am just installing a small 12v computer behind the fins to increase cooling.

The 100A aftermarket alternator wired to the engine start battery and from there to the Victron Orion DC>DC. There is a slight change in engine speed but otherwise no effects switching in and out the Orion.

Couple of points, it takes a bit of time to realise you don't need to fully charge lithium, indeed we leave it half charged. Secondly, it charges up far more quickly than lead acid. So instead of taking hours to top off the last 20%, it does it much more quickly leaves you thinking of what to also charge up hence using electric to bake cakes because we can. If your not cooking on electric, you could use the power to charge the Torquedo. 300w will generate 1.26Kwh a day, but there is long periods of the MPPT sitting in float, so only drawing a minimum from the solar power. We can increase this to 1.4Kwh by finding something useful for the MPPT to do.

Pete

 

[Trident]

I fitted a large bank of Sterling LiFePo4 batteries to a boat last year for a customer - he bought them without consulting me.

Firstly they are simply a rebranded product with no upgrade, as far as I can see from Sterling, except their natty "AMPS" sticker - but at over twice the eBay price for the same battery without that sticker!!

Secondly the tech guy I spoke to at Sterling had almost no idea about the chemistry of Lithium and how it has to be charged to last long term and thought that "if it lost 50% capacity within the 5 year warranty we'll replace it but if its just a normal (!?) 10-20% loss it would not be a warranty issue" A properly fitted and good quality Lithium battery should never lose 10% capacity in 5 years

I would caution very strongly against Sterling branded batteries

Meanwhile Victron are very over priced

If you do decide to go with LiFePo4 take a look at Battleborn and Renogy as the two bets brands currently available

 

[Pete7]

Got an e bay link to a similar battery to Sterling?

Agreed, Victron are expensive, but then they use high quality Winston cells. Clearly there are those who are happy to pay for this.

I looked recently a Renogy but the feedback from UK customers for some of their products is dire. Battleborn seem twice the price of Sterling.

Life Batteries have a good reputation on a FB 12v boating group, so could be worth considering.

Pete

 

[Tranona]

We have a 120Ah Sterling Lithium (LFP) battery wired in parallel to two 85Ah Trojan flooded lead acid (FLA) batteries. This is charged by 300w of solar. In good sunny conditions this will run all domestics including the fridge etc, but also allow the use of a small 1Kw electric kettle, toaster and induction hob for a 50/50% electric / gas cooking. In okay conditions we are a little bit short of solar say 30Ah each day, so can survive a couple of days before needing to charge via the Victron Orion DC>DC charger.

During 3 weeks in Aug 21 we only used the Orion twice to charge when it was foggy rain for a couple of days. We saw 60w from the panel even in the rain at mid day. This years cruise in September was a bit more difficult with lots of strong wind, clouds and rain so we hid in Weymouth and used the shore power to supplement extra demands by going 100% electric cooking, including baking.

In use when the kettle is switched on, the LFP provides about 90% of the power, the FLA 10% at night, for a total demand of 75A. During the day, solar provides maximum power first before the batteries to power the inverter and kettle, so the draw is 60A or so. The only reason we have two Trojan FLAs is they were the original house bank. Once they expire I will probably replace them with a single 100Ah AGM battery which is a good match to LFP. We disconnect the LFP when not on board to avoid float charging leaving the FLA to run the bilge pump.

The Victron Orion gets hot, very hot. Ours is mounted on the nav seat with a 3" hole behind it. Even so we have recorded 59c after an hours use. There is a reason for those big fins on the back. So mount it somewhere with good ventilation. I am just installing a small 12v computer behind the fins to increase cooling.

The 100A aftermarket alternator wired to the engine start battery and from there to the Victron Orion DC>DC. There is a slight change in engine speed but otherwise no effects switching in and out the Orion.

Couple of points, it takes a bit of time to realise you don't need to fully charge lithium, indeed we leave it half charged. Secondly, it charges up far more quickly than lead acid. So instead of taking hours to top off the last 20%, it does it much more quickly leaves you thinking of what to also charge up hence using electric to bake cakes because we can. If your not cooking on electric, you could use the power to charge the Torquedo. 300w will generate 1.26Kwh a day, but there is long periods of the MPPT sitting in float, so only drawing a minimum from the solar power. We can increase this to 1.4Kwh by finding something useful for the MPPT to do.

Pete

All very interesting - but just proves my point. Identify what your requirements are and design your power system accordingly. What you describe is totally different from what the OP is seeking to achieve. His consumption is a fraction of yours and he expresses no intention of using all the electrical appliances that you do. Of course the properties of lithium provide opportunities to do things differently, but that is not the problem posed.

He has doubts his current solar is sufficient, so the 2 obvious choices (after identifying the scale of the deficit) are to increase the solar capacity or increase the buffer (house bank size).

 

[Pete7]

All very interesting - but just proves my point.

He has doubts his current solar is sufficient, so the 2 obvious choices (after identifying the scale of the deficit) are to increase the solar capacity or increase the buffer (house bank size).

Point taken, but remove cooking and insert charging the electric outboard and now he will have much a greater demand. However, that is highly variable depending on how much the dinghy is used.

His idea of upping to 250w plus of solar would be my choice if he wants to cruise off grid regularly for a week at a time.

 

[Tinto]

My experience of Renogy solar panels, 2kW inverter and MPPT controller has been very good

 

[mattonthesea]

Update. Thanks all.
I have got a 200W panel to add to the 130W already installed. Maybe over kill but it worked out cheaper than smaller ones!
To cope with extra power I had to get a new mppt regulator so went for the sterling combined PV and B2B version. This way we have the choice of batteries when the present ones reach their end.

What has been a shock is the cost of all the accessories to fit them. I'm in no way the tidiest but I couldn't say that I could easily find my way around the battery compartment. So I've bought busbars, mounted fuse holders and proper cable in proper size and all the connectors to go with it.

Thanks again

M