Anyone have idea how to fit 2 300AH batteries in that space or other?  Is one 300 enough?

I'd say that 300Ah is enough. It is comparable with 600Ah of AGM as you can discharge your LiFePO4 batteries down to around 10%

What age were the AGM batteries when you replaced them?  Mine are now 5 seasons old and I think they may be on their way out.

What changes did you need to make to the charging systems?

And finally can you recommend a brand / supplier?

 

Pretty sure I have subsequently read that the aggressive discharge can "reset" the battery ...but I'm no expert.

 

On the other hand, my red flash engine battery that I also bought for the last boat did not last well!

Not sure about age. My boat was manufactured in 2013 and I bought in in 2017. I do not think they were original batteries as they had labels in Swedish on them so they are less than 4 yrs old. Probably changed by the previous owner who did not have much knowledge about electricity and drained the old batteries a couple of times.

I bought 2x100 AH from Sunbeam systems ( https://www.sunbeamsystem.com/en/smart-l-i-t-h-i-u-m-2/" rel="nofollow - https://www.sunbeamsystem.com/en/smart-l-i-t-h-i-u-m-2/ ). They are smart and have built in BMS. They claimed that they can be mixed with AGM batteries but not in the same circuit. I still have my AGM starter battery. The only thing I did was to change the thresholds on my VSR to close at 13.6V and open at 13.4 volts. (LiFePO4 batteries have a higher voltage at rest - 13.3V compared to around 12.8V for fully charged batteries) and to avoid that the Lithium batteries drained current to the starter battery I chose to increase the opening voltage to 13.3V. This also means that as soon as I stop the engine, the current falls below 13.4, relay opens and there is no connection between housing and starter battery.

I also have a 100W Solar panel connected to the housing battery side of the relay which will start to charge the Lithium batteries first. If the current stays above 13.6V for a longer time, the relay will close and also charge the starter battery.

The batteries also have bluetooth connection for app to iOS or Android where you easily can see the status. Very nice, I can strongly recommend.

Hi Joey.  I was living on the hook for a fair bit last spring and summer using solar and measuring consumption and charging.  

I have a 505 with a double drawer fridge, LED lighting, WiFi router, and music as my main uses of power when at anchor.  I was averaging about 1.4 kWh per day (or 110 Ah).   The fridge was the large part of that.  I was in Greece that was pretty warm (30C+) most days.   So your estimate is a little high I think, but it depends on how you use it.

On the supply side I have two 120W fixed panels that I leave on deck pointing roughly at the sun avoiding shadows.  I got about 1.1kWh most days from that  (or 85Ah).   So I had a deficit of 25Ah a day.    It varies according to how often I open the fridge or was diligent in placing the panels - but that was the average.

My batteries are at total of 520Ah in four Victron AGM packs.   I am happy to let them get to 70% charge to get a reasonable life out of them - so 156Ah to use.  Therefore I can be at anchor for six days before getting to 70% charge.   Of course the lowest point of charge each day is first thing in the morning so you also have to take off overnight use.  My fridge works less hard overnight so there is a nighttime dip of another 40Ah - so actually about 4-5 days at anchor without going below 70%.  Usually I am moving on to another island by then and, being the Med, using enough engine to get that back to 100% easily.   

I also have a generator if I don't want to move - but rarely use that just for charging (but do when I run the washing machine).

Of course one more solar panel would remove the deficit entirely.

I thought of Lithium batteries.  I would need 300Ah to be equivalent.  I do have the option to take my AGMs down to 50% charge if I don't do it too often.

My AGMs cost me about 1,300 euro.   Lithium would have been about 2.5 times that.  I reckon on getting at least five years from the AGMs whereas Lithium maybe ten or so - maybe a bit more time on both.  So cost neutral if you plan on owning your boat at least ten years plus.  AGM cheaper if not.

Lithium is much lighter so I would do that if I raced, which I don't.   Also the tech is better and improving all the time.   I think the next time I change my batteries they will be Lithium.   But I will likely be owning a different boat.

Hope that helps.

Great information from all which I much appreciate to get me heading in the right direction.

My battery monitor and solar controller are both Victron.  So I added their Venus GX system monitor.  It is a little computer that measures all current flows from solar, battery and demand side in real time - saving it to very useful graphs.    I think other suppliers do similar.  It is really useful to know exactly how much I am getting from my panels or how much switching on that device actually is drawing.

My kids all charging ipads and phones adds a far bit.  So we have a "charge it when under motor" policy.  Or at least not overnight. 

converting to Lithium is an interesting subject - good to hear experiences.

I've had 4 120AH AGM (Fullriver) batteries installed since June 2014 - 7 1/2 years! - the fridge is always on and draws around 35AH overnight - maximum usage when onboard is around 100AH overnight although I try hard to keep it lower than that. I have found that having good quality chargers and limiting the battery drain to be the secret to long life.

The batteries no longer test as new ones do (voltage drop is higher when a good load is applied) but they are not anywhere near needing to be replaced. I'm hoping to get Lithium next time especially if the price keeps coming down.

Hi Jooce,

How did you change the threshold on your VSR? Is it the original VSR? I was considering to install a Victron ARGOFET to isolate the service battery from the starter battery, but it seems like a better idea to change the settings on the VSR.

Hi Magne,

I have the Sterling Voltage Sensitive Relay. Instructions on how to change the thresholds found here:  https://sterling-power.com/products/voltage-sensitive-relay-digital-80-160a-12-24v" rel="nofollow - https://sterling-power.com/products/voltage-sensitive-relay-digital-80-160a-12-24v

Looked at lots of options for Lithium; internal BMS batteries from USA, Victron and buying individual Winston cells to build up a battery ourselves. It is this latter option we chosen, importing 600Ah worth of cells from Winston's Czech based EU importer. We have it all connected at home with external BMS, charger/load shutdowns and an additional 100A charger to reduce 50% charge time to something under 2-hours. These cells will not fit within the existing battery box so we're also constructing a new box ~1" wider and ~4" longer which will still fit under the port-side saloon seating.

Total cost for 600Ah by this route is ~£3,500 ... but this is a big project and I'm an electronics Engineer by background which helps. We hoping 7.5kWh of stored energy aboard should be sufficient to see us through half a week on sun-free, wind-free days without running the engine/generator.

Cheers.

Ian & Andrea

SV Gabrielle

Reason for asking is that some lithium batteries, like the Victron Superpacks, seem to be limited in what they can product continuous and peak. Even the 200 Ah Victron Superpack does only 70 Amps continious.  I presume that if you put two in parallel you can get 140 Amps, but even that seems kind of low....

Harold

S/V Ventus

H415/314

Boston

I have designed mine around 300A continuous protected by a 500A fuse so the system must be capable of withstanding a short-term 500A load to blow the fuse! My thrusters have dedicated lead-acid batteries so the lithiums only supply recharge current through a pair of 30A DC/DC converters, not the full thruster loads. If your thrusters are powered directly from your lithiums, then you could be looking at more than 500A. Does you existing installation have any fuses to give you a clue as the the maximum current expected?

Given this I am wondering what the right design spec should be.   I am also, wonder how well the BMS in each battery balance the current draw and what happens when the maximum is reached.  Will it in practice really divide 50:50 if there are two batteries in parallel?   Do BMS in each battery just cut off current if the maximum is reached or cap it to the limit?

Your winches will not draw anything like 125A unless they're under heavy strain and suggest it is unlikely you will have both under heavy load at the same time. It is also very rare for us to use the windlass without the engine running with its 115A alternator turning so there is no load on the batteries. I'm sure with a system design for permanent 300A (fused at 500A), my system is very unlikely to be overloaded. This is an external BMS system of course.

Sure the battery supplier can advise if you share your power loadings with them.

As for balance, it is essential that battery cabling is identical in length and cross-section for each battery to ensure they charge/discharge evenly. Internal BMS batteries are almost aways autominous so have no idea what the other batteries are doing. It is possible that close to fully charged or fully discharged that one battery may cut-off before the other but you should avoid getting into this position anyway so I would not worry about this too much. You obvious need some good external battery monitoring to warn of high/low battery voltage such at the Victron BMV700 series (or equivalent). 

Hope that helps?

Cheers.

Thanks a lot!

Harold

There is another thread detailing my Lithium replacement but here is some data that may be interesting to those upgrading. 

We have the boat in Greece so sun availability is pretty good. 

We have two fridges and overnight these consume between 50 and 75Ah depending on ambient temperature. 

Three fairly old 100w solar panels and these produce between 1 and 1.75Kwh (approx 80-150Ah) depending on time of year. 

With minimal anchoring and mooring the engine use tops up any short fall. 

We have 300Ah total and have yet to get below 20% charge. 

Another question that was raised was the maximum discharge current. The BMS will limit this but the cells themselves will, apparently, tolerate  1c discharge rate. In our case that is 300A. More than enough for most uses, not sure I’d want to run at that current for an extended period. We have a lead bow thruster battery so only the windlass and winches are on the lithium.

Mike 

I've been considering a REC but am still contemplating other devices. 

Essential to me that charge and load controlled separately with proper hard-wired alarm for a low cell voltage. We've previously had electrics fail at night while on passage ... and it's not a great place to be!

Absolutely no issues and the configuration options are excellent. I've been monitoring several forums for 'off grid' solar and this BMS seems to be popular with very few issues.  I've never come anywhere close to the 200A limit and if you do my guess would be a momentary draw, stalled windlass for example, and the config allows for a specific time to be set for these excesses and a wait time for the reset.  

Happy to answer any question about the BMS.   

My configuration allows starting engine at the batterybank (no extra start battery)

To my sceptical being I am now convinced that my system is really good 

https://lime-power.se/sv/produkter/paket/paket-fritidsbat-large.html" rel="nofollow - https://lime-power.se/sv/produkter/paket/paket-fritidsbat-large.html

I have a setup that only charges to 85% full in reality it’s close to 92% full due the chargepaten that my victron solar charger has

I have the fridge on whole summer in Sweden 

On each side I have a 110w solar panel wired in parallel to same regulator both panels 

And a 50w on deck with it’s own solar regulator 

It’s now at its fourth year cycle still working flawlessly 

During summer I only use the engine for moving the boat not charging 

Still autopilot and electric running at same battery bank 

To date never got lower than 60% of full 

Today I visited the boat and took some photos

No it’s not integrated the alternator is still setup for led battery 

That gives me a system that’s not charging the lithium batteries to full and not engaging the alternator when the batteries are over ca 80%

The BMS limits has up today never been reached 

As to the solar regulator I have a slight lower max voltage than standard setup 

As winter is currently coming I have cut the main svisch and let it be at near 90% all winter and suspended the solar regulator in the menu (Bluetooth)

In the spring I svisch on the main and enable the solar that’s all

I guess this is the simplest way running lithium and maybe not the best but it works well enough for us

Normally the battery is fully charged before noon no matter how low it goes at every evening whiteout starting the engine 

So my solar panels and regulator is working perfectly for my setup 

Regarding my alternator it’s temperature regulated 

And I don’t run my motor in idle to charge I just use it in and out of harbour 

What I noticed is more belt wear than running Led battery but it’s not that much of an issue 

Regards jonas

PS batteries are sold branded LIME but they are Winston cells 

Can you elaborate on your alternator and how it’s regulated? Does it monitor voltage output etc?  I’m located in Puget Sound and it’s not uncommon for me to motor for a day to get to my destination - so I am wondering about overcharging. And the thing about lfp‘s frying the alternator.

Also curious what you use to charge when on shore power. Sounds like you might not need this as your solar does this for you? My boat spends too much time on the dock and it has an older Magnum inverter/charger that I’m told is not compatible for charging lfp. I have thought about charging lfp with a cheaper (say 20 amp) unit that is capable of this.

Thanks,

PS before every one starts badgering me about 1. motoring - the Sound can have really light winds combined with 2 or 3+ knots of current means a really long sail to get anywhere, and 2. dock time - hoping that will change in a couple years when my wife retires although boats seem to require monetary feeding…. 

As my normal sailing is in Sweden’s arhepelage and seldom at marina I values that the need for additional charge is low 

During long day sailing instruments and autopilot work fine whiteout need for engine power to charge extra

Fridge is ASU only modifications is a extra diod in serie at + to the ASU module (this keeps it from running at max cooling al time)

If motoring for a night the voltage drops to 13,8 at the monitor to 13,9 from alternator only

So the solar panels is what tops it up

We have a dimmer on the lights in the boat (all LED)

And charge mobiles and a modern laptop 

But that’s all 

Hi.

I have detailed the installation in two other threads but in essence the start and bow thruster batteries are AGM and the charging for these is unchanged from factory install that is for alternator and mains charger. The Lithiums are connected to, and isolated from,  this side of the system via two DC-DC chargers. These chargers present themselves to the alternator and mains charger as just another load and so there is no need for any communication.  The DC-DC chargers take whatever voltage the alternator supplies and raises or lowers this to meet the charging needs of the Lithiums these have a charge profile for the lithiums and so dont communicate with the BMS. They are 'intelligent' in that they detect when the engine is not running and disconnect so that the start battery isn't discharged.  This replaces the standard automatic battery combiner. The solar charger is connected direct to the Lithium bank and doesn't charge the AGMs.  There is no communication needed between the solar charger and the DC-DC chargers.  The BMS has no need to communicate with the other systems and is also stand alone and is only used for active balancing of the cells and detecting fault or over current conditions.  There is a wiring diagram in my threads

The reason for upgrading this way was to minimise the physical changes and minimise the costs.  its been working well with the exception of the mains charger that cant provide sufficient current for the Lithiums with both DC-DC charges running.  One is switched off when on mains.  

If building a system from scratch in a new boat this wouldn't be the best approach to be honest. 

Hope that helps.