24 volt gear on 12v boat

[Anchorite]

I've inherited a 24v anchor winch and a 24v Webasto: is there a safe foolproof way to switch 2 of the 4 bank 12v batteries to power the 24v gear (leaving the other 2 on the alternator/services). Engine battery is separate.

 

[FlyingDutchman]

I stand to be corrected, but I don't think so.
You could put 2 batteries in series to get 24V but as the alternator is 12V, the problem will be the charging.

 

[Anchorite]

It can be done using relays to pull in or drop out 2 batteries: I was hoping someone has been down this road to say "Don't do it!" or get 2 new batteries (again with charging relays from 12v) or change the motors to 12v or sell them on ebay and buy 12v stuff... /forums/images/graemlins/crazy.gif

 

[cpedw]

Have a look at this. I don't know if it's what you are after but it seems as if it may be. I've never used the company so I can't vouch for them but the website has been around for several years if that's any recommendation.

Derek

 

[jay]

I had a similar problem getting a 24v eberspacher working on a 12v boat. I eventually used 2 of the of 12-24v converters from these peolpe. www.alfatronix.co.uk. Was fairly expensive and needed some fairly involved anlayis of the amperage requirements - and then wring them up was fun. They are extremely helpful but I'd price it up 1st versus the cost of replacing the 24v items you have. It may be cheaper and less hassle in the long run. I have no link with alfatronix - just a very impressed customer

 

[Airborne473]

Why not get an Inverter. That will produce 24v DC from 12v DC. Seems the best way forward to myself

 

[Anchorite]

That looks just the job! Thanks for the link

 

[Anchorite]

Thanks for your suggestion: I had a look at that site but even not knowing the prices the amperage seems too low for the unit I took to be their biggest (10/13A). The anchor winch weighs in at 80+ Amps on the 12v side so would need several units in parallel. The american gadget linked above handles this sort of load automatically for 119$ ex works.

 

[jay]

Yep true on the windlass. Had my mind on the heater. Wish id seen the american thing when i was doing mine. Would be interested in seeing an update on how easy it is to purchase/install/use.

 

[boatbuilder]

What price is a 12v motor for the anchor winch, often just a straight swop. As to the webasto, no idea, sorry.

 

[Anchorite]

Looked (looking) into that: replacement motor is over 300 quid. /forums/images/graemlins/crazy.gif

 

[halcyon]

Used to be common an rally cars, combined batteries to give you 24 volt to turn a hot engine with a 12 volt starter. Did the same job as the US system, try a search on the rally car sites.
I think I know of a British unit, will have a look when I have a sec.

Brian

 

[kandoma]

considering the cost of an anchorwindless and an Eberpächer, I would seriuosly consider changing the alternator from 12 Volt to 24 Volt. Changing some bulbs in the navigation lights and off you go. Modern electronics usually accepts 24 Volts. The rest, I would hang on 24 Volt with a (cheap) converter 24-12. The starter would just be connected to one of the batteries.

Peter

 

[duncanmack]

Anchorite,

When there was a craze for putting good modern diesels in old Land Rovers there was a similar problem to yours.
Toyota and Mazda engines - which were favourites - had 12v alternators but 24v starters.
Hella did do a unit which sorted out the problem, but I can't find it on their website.
I haven't seen one for years, but if you contact the LandRover owner's Club someone there will point you in the right direction

 

[William_H]

Yes the idea of converting your whole system to 24 volts is perhaps the best idea. The engine starter should be OK on 24 volts.
You might like to try the winch on 12 volts it just may be usefull at lower power for a smaller boat/anchor.

Right now to get 24 volts from your 12v system you need to accept that 24 volts will not be able to be used and charged at the same time. Or at least not to any usefull current assist degree.

You can either charge individula batteries at 12 volts and switch to 24 with relays when you need 24 volts or have dedicated 24 volt batteries which are slowly charged from a 12 to 24volt converter. Low current.
If you choose this last path you need an output of 27.5 to 28 volts under load. The easiest way to confirm being an ampmeter to check charging current into the 24 v batteries.
You need a switch or Voltage sensing relay to ensure they are only charged when the engine alternator is charging the 12 volt circuit.

The relay swirtching of the 12 v batteries might be an easier path. However be aware that your westasco could discharge the batteries including the engine start battery. Ujnnless you have separate batteries for engine start.

To explain you start with your 12 volt service battery. You need a contacting relay to connect the service positive to the negative of the (call it) winch battery. At the same time the negative of the winch battery needs to be disconnected from the ships negative.
This process can be done with a changeover relay. That is a contact that rests on one point and moves to touch another when power is applied. You may be able to find a suitable high current relay with changeover contacts suitable for 100 amps but more likely you can only find relay with contacts that make when power is applied. You need a high current relay to switch the negative of the winch battery to the pos of the ships 12v battery but the contact for connecting neg winch battery to neg ships battery when at rest charging does not need to be so big so you could use a changeover relay for the charging rest contacts and a big relay for winch use.
You will need another relay contact to connect winch positive to ships positive when at rest charging.
These functions could be done with big switches but must be done in correct sequence or simultaneously at avoid shorting the battery in the process. A relay means they all function at the same time hopefully not providing a short in the transit and it can be switched remotely when you need the winch. As I understand it the product sugested does all this in one box.
It might be easier for the heater to use a power converter even with relay switching for the winch . PM me if you are confused. olewill

 

[rogerthebodger]

It can be done by using 2 change over relays but to drive your windlass they must be big DC switching types and if one should fail there could be a big bang so be very careful. If you need more help PM of Email me