Flat battery

[petem]

Our electricity isn't metred and it never spends a night off shore power so I don't think solar would help. It would just be something else taking up space and going wrong!

[Hurricane]

Pete
The big problem with batteries is the house set.
I think you are saying that it is your house set that have failed.

At anchor, IMO, you really need to charge them as fast as possible.
Batteries take most amps when they are most discharged.
In my case, I have a 100a charger which will put 90a in when charging empty batteries.
Half an hour later the charge rate is down to less than about 50a.
Half an hour later than that it is down to less than about 30a
Exponentially.
It actually takes about 8 hours to get the battery charge to a level where a float charger will keep them topped up.

So, in your case, if you don't want to do a quick charge, you could get away with quite a small charger and let it take days to charge.
But, a 30a charger would seem to me to be the smallest you should have.

If you want to charge batteries quicker, get a bigger one but there is also a limit to the maximum current that the batteries will actually take.

BTW - never take your batteries down to less than 50% or you will kill them.
Hence Bart's comment about getting a good battery monitor - don't just rely on the voltage.

[BruceK]

Edit

Pete has absolutely nowhere to install panels like that.
I have 4 smaller ones on a 20m boat and that was difficult to find somewhere to fit them.
Mine are from Photouniverse though.

Fair enough. I thought his setup may not be too different to mine both being 34foot sports cruisers. For any interest, you can see where I placed mine although admittedly not the photo's intent



Underneath the kids seating in this shot

[BartW]

Would something like this work for me?

https://www.victronenergy.com/blog/2...arger-30a-50a/

https://www.asap-supplies.com/victro...harger-12v-30a

the first is a very good choice,
model number : Phoenix Smart IP43 Charger 12/30 (1+1) PSC123051085

the latter:
"Victron Phoenix automatic charger"
is a older more expensive model, (with interface for remote controll..) you don't need that.

this model (available from asap) could also be used,
"Victron Blue Smart IP22 Charger 12/30 (3) BPC123044002"
https://www.asap-supplies.com/brands...rger-123044022
less expensive than the first,
has a fan, and is only IP22 (not at all water proove)
I have this in Blue angel for topping up the 12V cirquit (2 x 100Ah batts)

[BruceK]

Our electricity isn't metred and it never spends a night off shore power so I don't think solar would help. It would just be something else taking up space and going wrong!

What? No week away anchorages? Pete! You're letting the side down.

[petem]

Pete
The big problem with batteries is the house set.
I think you are saying that it is your house set that have failed.

At anchor, IMO, you really need to charge them as fast as possible.
Batteries take most amps when they are most discharged.
In my case, I have a 100a charger which will put 90a in when charging empty batteries.
Half an hour later the charge rate is down to less than about 50a.
Half an hour later than that it is down to less than about 30a
Exponentially.
It actually takes about 8 hours to get the battery charge to a level where a float charger will keep them topped up.

So, in your case, if you don't want to do a quick charge, you could get away with quite a small charger and let it take days to charge.
But, a 30a charger would seem to me to be the smallest you should have.

If you want to charge batteries quicker, get a bigger one but there is also a limit to the maximum current that the batteries will actually take.

BTW - never take your batteries down to less than 50% or you will kill them.
Hence Bart's comment about getting a good battery monitor - don't just rely on the voltage.

Mike, we only tend to go our for a three or four hours and the only thing that is running is the galley fridge (which was new his year so way more efficient than the old 2002 one). We're no way near discharging the batteries. Once we get back (later afternoon) the boat is back on shore power and charging for the next 18 hours.

[BruceK]

Mike, we only tend to go our for a three or four hours and the only thing that is running is the galley fridge (which was new his year so way more efficient than the old 2002 one). We're no way near discharging the batteries. Once we get back (later afternoon) the boat is back on shore power and charging for the next 18 hours.

you'd have been better off with timeshare and a trailer boat. No matter, between your jaunts to your marina queen you should take up some Welsh Med hospitality and come out with the mob. If we cant teach you nothing you can at least go home legless

[Croftie]

this model (available from asap) could also be used,
"Victron Blue Smart IP22 Charger 12/30 (3) BPC123044002"
https://www.asap-supplies.com/brands...rger-123044022
less expensive than the first,
has a fan, and is only IP22 (not at all water proove)
I have this in Blue angel for topping up the 12V cirquit (2 x 100Ah batts)

+1, I have a 20amp one with the 3 outputs to look after, engine/domestic/gen batteries. I have tried with a clamp meter and the total max output is 20amp split between the 3 outputs. So gen and engine batteries may need 2amp for float whilst the domestic bank takes say 10amp or whatever it needs.

[petem]

the first is a very good choice,
model number : Phoenix Smart IP43 Charger 12/30 (1+1) PSC123051085

the latter:
"Victron Phoenix automatic charger"
is a older more expensive model, (with interface for remote controll..) you don't need that.

this model (available from asap) could also be used,
"Victron Blue Smart IP22 Charger 12/30 (3) BPC123044002"
https://www.asap-supplies.com/brands...rger-123044022
less expensive than the first,
has a fan, and is only IP22 (not at all water proove)
I have this in Blue angel for topping up the 12V cirquit (2 x 100Ah batts)

Thanks Bart. The charger is in the engine room which is relatively dry but I think an IP43 variant would be less prone to rust.

Doing some further investigation, there seems to be a calculation that you should purchase a charger rated at 10% of the A/H. In my case, the two house batteries total 270 A/H so a 30amp charger would appear to be a good choice. Furthermore, the "(1+1)" variant supports charging to a house bank plus 3amps for a dedicated starter battery which would give me the option of connecting it to my stand alone starboard side battery.

https://www.es-store.co.uk/product_d...php?product=PH 12/030-1-SM&description=Phoenix-Smart-IP43-Charger-12V/30A-(1+1)&cat_desc=Victron-Phoenix-Chargers&cat_id=68&show_menu=21

[BartW]

Yes that midel looks good for you,
From the same range I have a 24v to 12v convertor in a locker on the FB, for topping up the tender batt. During winter.