12V from 24V

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Redfox226

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Hi

I have made the decision to convert to electric auxiliary power on my boat, which requires 24V batteries. The boat is not large - space is at a premium.

Current system: 12V – currently supplied from 120Ah battery under companionway steps and charged by 80W solar panel through victron 75/15 controller (will do 24V). Under shorepower, Ctec charger also available.

Plan: Change Main battery bank to 24V to supply Pod Motor

House Power:
either: replace LA battery with 20Ah LiFe battery in toilet compartment (small space to fit it). Charge 20Ah battery through Sterling 24-12 BtoB charger from 26/104. (Expensive option)
or: Use Victron 24/12 20A DC-DC Converter (Cost effective option - < 50%)

My power requirements are meagre, <20Ah daily. Does the panel have a view on either of these arrangements?
 
I have a 24V system and use a BEP 24/12 DC/DC Converter. It works fine and manages quite a lot of 12V stuff. However, do you really need 24V on your boat? I recent rewire was a total faff with having two voltage systems.
 
BlowingOldBoots said:
I have a 24V system and use a BEP 24/12 DC/DC Converter. It works fine and manages quite a lot of 12V stuff.
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Thanks - useful info - what capacity is the converter?
BlowingOldBoots said:
However, do you really need 24V on your boat? I recent rewire was a total faff with having two voltage systems.
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Electric motor - 2 choices - 24 or 48V.
 
BlowingOldBoots said:
I have a 24V system and use a BEP 24/12 DC/DC Converter. It works fine and manages quite a lot of 12V stuff. However, do you really need 24V on your boat? I recent rewire was a total faff with having two voltage systems.
Click to expand...

The same , boat is 24volt but have a 30 amp drop down to 12 volt on a seperate smaller fused panel , but really only power , my VHF and stereo ,
As asked why do you need to go to 24 volts as your usage is rather small so why bother
 
Redfox226 said:
Hi

I have made the decision to convert to electric auxiliary power on my boat, which requires 24V batteries. The boat is not large - space is at a premium.

Current system: 12V – currently supplied from 120Ah battery under companionway steps and charged by 80W solar panel through victron 75/15 controller (will do 24V). Under shorepower, Ctec charger also available.

Plan: Change Main battery bank to 24V to supply Pod Motor

House Power:
either: replace LA battery with 20Ah LiFe battery in toilet compartment (small space to fit it). Charge 20Ah battery through Sterling 24-12 BtoB charger from 26/104. (Expensive option)
or: Use Victron 24/12 20A DC-DC Converter (Cost effective option - < 50%)

My power requirements are meagre, <20Ah daily. Does the panel have a view on either of these arrangements?
Click to expand...

20Ah per day isnt quite the whole picture. If you took all that in 1minute then its a whole different kettle of fish. However, in the real world.... a DC/DC converter is certainly the way to go, cheaper, smaller, less faff than a separate 12V battery and charger. With switch mode (as it certainly ought to be) power loss will be minimal (less than 5%)

Do you really need 20A, seems like a lot for 20Ah per day... I see smaller ones.
 
moomba said:
As asked why do you need to go to 24 volts
Click to expand...

Because he's propelling the boat with it!

The two different systems being proposed are actually pretty similar, with a DC-DC converter from 24v to (nominally) 12. Then one system has an additional small battery on the 12v side and the other doesn't. I suppose this battery adds a touch more overall capacity to the boat, though only usable for house loads and not propulsion, but otherwise it doesn't seem to be doing much.

If house power requirements are "meagre", is a 20A DC-DC really necessary?

Pete
 
Having 24v and 12v systems is not at all uncommon, most big mobos are wired that way. Just fit 24v system and a DC-DC converter as in your second option in post #1. As Dougal points out, small ones are available, but allow some margin for future proofing.
 
Because he's propelling the boat with it!

Yup my mistake , missed that bit , yes a simple DC converter 24 volt to 12 volt , really up to you for the size , are you thinking of upgrading , adding more equipment, getting a bigger fridge for the beer , so up to yourself , on the converter
work out your amps and make some redundancy into it if you want a 30 amp converter its slighlty more money but its your money.
 
Converters can be quite cheap from China and Ebay. I would suggest that you make a list of all equipment that must have 12v presumably lights and electronics. Consider a converter for each item. Rather than 1 big converter. I would normally suggest a separate 12v battery for services with a 24 v battery for diesel engine but as you do not need charge to start the engine you may as well just have one battery source. Or put another way make all batteries available for propulsion. ol'will
 
Thank you all for your replies. The feeling of the panel would therefore appear to be in favour of the more cost effective option - for which many thanks!

I already had the Victron Orion DC-DC converter in my sights, and yes, the larger capacity would allow flexibility for future increased power usage - if I can find deck space for more solar capacity!

Once the project comes to fruition, I shall post a description on here.
 
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