Charging lithiums new boat..

[pandos]

I have just bought another boat. (A Southerly)

I am told there is a problem with the charging system.

Boat comes with two lithium batteries one of which has been fitted the other has not been used. The one that was fitted was put in parallel with a lead acid battery to protect the alternator in the event the lithium shut down.

The boat has a split charge relay, which does not function, and a 1,2 both switch.

It has a windlass and bow thruster.

Is this plan in sensible?

Put in two agm 100ah bats for an engine bank and connect the windlass and thruster here.

Put the lithiums together as a house bank.

Fit an Argofet isolator on the alternator output, connected to a Victron Energy Orion-Tr Smart DC-DC Charger -
feeding the lithiums and the other feed directly to the engine bank.

Thanks in advance..

 

[Tranona]

First question is do you need lithium? and if so how are you going to charge them? They only really make sense if you have lots of solar and a high usage pattern as in a sailing boat, although the lithium will charge quicker the real value is being less reliant on running the engine, If you do want to fit lithium then charging using a B2B from the start battery is one straightforward way.

You do not need a 100ah battery to start the engine, let alone 2. The usual ways are either wire them straight to the engine start - you do not need large capacity, just high CCA and only run them when the engine is running. This means running heavy cables through the boat if they are not already there. Alternatively (and I think better) is to fit a bow battery to service both and charged by a B2B from the start battery. You only need one pair of light cables as it is only taking the 30A charging current. On my boat I have a high output 32ah AGM start battery and a 105ah bow battery. House bank is AGMs as my pattern of usage simply does not justify the added complication and cost of lithium.

 

[Neeves]

In terms of the windlass and bow thruster - you will only be using either with the engine already running. You, apparently?, don't have the 2 x 110 amp batteries, so as Tranona suggests down size the investment.

How big are the lithium batteries? For how long has the one Lithium used, why was the Lithium purchased (they maybe cheaper than they were but still not cheap). My understanding would be that there might be issues if the 2 lithium batteries are different (different BMS, different size, different historic usage) - you might need to provide more information to enjoy a sensible recommendation.

The higher cost of Lithium, over Lead, is not so relevant as you already have the Lithiums - unless your lithiums are small. Your challenge might be how to use the Lithiums, your Lead choice is easier (as you don't have them yet), through you must have a starter battery and you must already have something to feed the windlass and bow thruster (that you have not yet clearly defined.

Jonathan

 

[PaulRainbow]

I have just bought another boat. (A Southerly)

I am told there is a problem with the charging system.

Boat comes with two lithium batteries one of which has been fitted the other has not been used. The one that was fitted was put in parallel with a lead acid battery to protect the alternator in the event the lithium shut down.

The boat has a split charge relay, which does not function, and a 1,2 both switch.

Get rid of both and fit on/off switches.

It has a windlass and bow thruster.

Is this plan in sensible?

Put in two agm 100ah bats for an engine bank and connect the windlass and thruster here.

As said, a single battery will be OK here.

Put the lithiums together as a house bank.

Yes

Fit an Argofet isolator on the alternator output, connected to a Victron Energy Orion-Tr Smart DC-DC Charger -
feeding the lithiums and the other feed directly to the engine bank.

Thanks in advance..

Connect the alternator to the engine battery as normal and use the DC-DC charger to charge the Lithiums, do not fit an Argofet.

Mains and solar charging can go to the Lithiums if the chargers have suitable profiles.

Fit solar.

 

[pandos]

Get rid of both and fit on/off switches.

As said, a single battery will be OK here.

Yes

Connect the alternator to the engine battery as normal and use the DC-DC charger to charge the Lithiums, do not fit an Argofet.

Mains and solar charging can go to the Lithiums if the chargers have suitable profiles.

Fit solar.

Thanks for that above and to the other posters...

Is there a reason to not fit the argofet?. I rather like the idea of not having the two battery banks joined other than via diodes or an argofet (unless it's by me with my 1 2 both..)

I will fit solar in time. But the boat is 4 hours drive away and to get home I must sail a few hundred miles of the West and South coast (of Ireland) so I intend to make a cruise of it. So I want a better than get me home solution...

(I have been 30 years promising to go to the Arann islands, I can hardly sail past with out stopping for a Guinness)


Realistically what is the minimum size of DC/DC charger that I can get away with.?.

It's only a 70 amp alternator. I was thinking 30 amps would be ok..

(The boat is full of raymarine gear including radar and MFD so there may be many more questions..)

Thanks..

 

[Neeves]

Thanks for that above and to the other posters...

Is there a reason to not fit the argofet?. I rather like the idea of not having the two battery banks joined other than via diodes or an argofet (unless it's by me with my 1 2 both..)

I will fit solar in time. But the boat is 4 hours drive away and to get home I must sail a few hundred miles of the West and South coast (of Ireland) so I intend to make a cruise of it. So I want a better than get me home solution...

(I have been 30 years promising to go to the Arann islands, I can hardly sail past with out stopping for a Guinness)


Realistically what is the minimum size of DC/DC charger that I can get away with.?.

It's only a 70 amp alternator. I was thinking 30 amps would be ok..

(The boat is full of raymarine gear including radar and MFD so there may be many more questions..)

Thanks..

I am sure I will be corrected, and for some corrections I have already instigated the ignore function. But DC/DC chargers tend to be small and 30 amps seems a common size (as does the size of your alternator) - you are amongst friends.

Jonathan

 

[Tranona]

Thanks for that above and to the other posters...

Is there a reason to not fit the argofet?. I rather like the idea of not having the two battery banks joined other than via diodes or an argofet (unless it's by me with my 1 2 both..)

I will fit solar in time. But the boat is 4 hours drive away and to get home I must sail a few hundred miles of the West and South coast (of Ireland) so I intend to make a cruise of it. So I want a better than get me home solution...

(I have been 30 years promising to go to the Arann islands, I can hardly sail past with out stopping for a Guinness)


Realistically what is the minimum size of DC/DC charger that I can get away with.?.

It's only a 70 amp alternator. I was thinking 30 amps would be ok..

(The boat is full of raymarine gear including radar and MFD so there may be many more questions..)

Thanks..

You don't need to join the 2 banks except perhaps for an emergency switch to connect the house bank to the engine. If you are using the engine battery to power the windlass and the bow thruster you don't need any split charging. The 2split" comes from using a B2B (30 amps is the correct size) which directs the alternator charge to the lithium house bank. You would only need the Argofet if you were charging a bow battery direct from the alternator as it would split the charge between that and the start battery. You don't say what the windlass and thruster are currently powered by (see post#2)

 

[B27]

.....


Realistically what is the minimum size of DC/DC charger that I can get away with.?.

It's only a 70 amp alternator. I was thinking 30 amps would be ok..

(The boat is full of raymarine gear including radar and MFD so there may be many more questions..)

Thanks..

The minimum size of DC/DC you can get away with is the number of Ah you need to put into the lithium, divided by the engine hours available to do that.
So you could try defining your daily energy needs in Ah, and consider how much motoring you will do to provide that.
Both numbers are going to be estimates and there may always be days with less motoring.
Other people's estimates of the numbers will be more error prone than your own!

The size of your battery bank determines how many days you can average things over.

If you're thinking about maybe doing 2 day passages under sail with autopilot and fridge running, with only half an hour's motoring while you anchor, then it gets difficult.

Eventually, you find an edge case where you have to admit your boat is not on the National Grid and you have to adjust your power use to match the generation, or motor just for the generation to match the power use.
You can spend more on 'stuff' to reduce the number or impact of the 'outlier' days when you motor less than normal and consume more.
But the cost/benefit may vary.

How many days a year are you prepared to think 'I could do with motoring a bit more to charge the batteries'?

Even a modest amount of solar moves the goal posts a lot. At least in Summer!

Do you have shore power, so you can start every cruise fully charged and not worry about mooring up with low batteries?

The other thing is, 30A is probably a reasonable load for a 70A alternator that will also be feeding engine battery and so on.

 

[B27]

The 'bow battery' for the thruster and windlass is a separate question, firstly, is there a physical space for a bow battery?
Or is there wiring to run these from an engine bank?
Running them from a 'small' lithium house bank is probably not going to work.

The physical location of battery space will influence the solution.

 

[bignick]

Lithium batteries will draw lots of current and can cause an alternator to overheat and fail. You don’t say what size of boat or engine (ie alternator rating) you have, but this should be an additional consideration when sizing your dc-dc charger, as it will protect the alternator to some degree.

 

[Tranona]

He does and it is a Southerly with a 70A alternator and a 200ah lithium so a 30A B2B would be fine.

 

[bignick]

Missed that.
Yes, a 30A B2B charger will be absolutely fine with a 70A alternator.

 

[pandos]

Thanks for the replies. Next stop Amazon...

 

[PaulRainbow]

Thanks for that above and to the other posters...

Is there a reason to not fit the argofet?. I rather like the idea of not having the two battery banks joined other than via diodes or an argofet (unless it's by me with my 1 2 both..)

If you only have an engine/windlass battery and a Lithium domestic bank, what is the Argofet going to do ? It should be used for charging 2 or 3 banks from the alternator, whilst keeping them separate. You only have two banks and the B2B will be charging the Lithiums from the engine battery/alternator, whilst keeping them separate. If you used a Argofet to charge the Lithiums your alternator is likely to overheat.

I will fit solar in time. But the boat is 4 hours drive away and to get home I must sail a few hundred miles of the West and South coast (of Ireland) so I intend to make a cruise of it. So I want a better than get me home solution...

(I have been 30 years promising to go to the Arann islands, I can hardly sail past with out stopping for a Guinness)


Realistically what is the minimum size of DC/DC charger that I can get away with.?.

It's only a 70 amp alternator. I was thinking 30 amps would be ok..

30 amps would be fine, as others have said.

(The boat is full of raymarine gear including radar and MFD so there may be many more questions..)

Thanks..

Fire away......

 

[pandos]

Many thanks..

Wifee and I have COVID, so all plans on hold for a few days,

 

[PaulRainbow]

Many thanks..

Wifee and I have COVID, so all plans on hold for a few days,

Hope you're feeling better soon.