bigcol Posted May 17, 2019 Report Share Posted May 17, 2019 So I now have an engine, in the work shop it comes with 2 x 12v alternators the engine alternator is okay as I will have a separate engine start battery. but for the domestic 12v alternator is no god as my main boat domestics are all 24v i Carnot oxford a new 24v alternator but on eBay we can buy https://www.ebay.co.uk/sch/i.html?_odkw=90+hp+beta&_osacat=0&_from=R40&_trksid=p2045573.m570.l1311.R-1.TR8.TRC2.A0.H0.X12v+to+24v.TRS0&_nkw=12v+to+24v+step+up+converter&_sacat=0 just wondered would this be okay to fit between alternator and battery bank?? thanks in advance col Link to comment Share on other sites More sharing options...
Tony Brooks Posted May 17, 2019 Report Share Posted May 17, 2019 Yes, but what is the maximum amperage it can carry? The one I looked at said 10 amps and I am not sure if that is 10 amps on the 12V input side or 10 amps output. My guess would be that with flattish batteries it would burn out PDQ. If you have an inverter the cheapest way as a temporary measure might to be charge via the inverter and a 24 volt battery charger while the engine is running. Link to comment Share on other sites More sharing options...
Alan de Enfield Posted May 17, 2019 Report Share Posted May 17, 2019 (edited) I would imagine that a suitable 12v - 24v step-up that would handle the output of a (say) 70 or 100 amp alternator would cost in excess of a 24v alternator. Try some truck supply places. I have phoned the local one I use and they passed me onto their electrical specialist (Gary Hare) I have spoken to him and he said "don't go down the 12v to 24 volt booster it just adds unreliable complexity and will cost a fortune to get one big enough anyway". What he has said is that if you provide him with the model number off the 12 v one you already have he will match it exactly (mounting brackets, pulley size / design etc) with a 24v version. Alternatively good photos with some dimensions and he could probably work it out. You then simply bolt it on in the same place using the same brackets. He even offered to come out to the boat (if you were local and sort it out for you) 40a - 50A 24v alternator prices start at £50-£60 but he could not give any idea of what yours would cost without more detail. Should you wish to call him his number is "079 three 0560 six 3 seven" Hope that helps. Edited May 17, 2019 by Alan de Enfield 2 1 Link to comment Share on other sites More sharing options...
MtB Posted May 17, 2019 Report Share Posted May 17, 2019 That's helpfulness beyond the call of duty Alan. Have a big fat greenie! 1 Link to comment Share on other sites More sharing options...
MtB Posted May 17, 2019 Report Share Posted May 17, 2019 Oh and there is another problem, I suspect, with those step-up devices. I bet they really do only step up to 24V, or a bit less. 24V stuff is only nominally 24V and actually expects to be fed with 25.0 to 28.8V under normal circumstances. Feed things like water pumps and fridges with 23.5V from a converter and they'll run sluggishly, or not at all (I suspect) in the case of a fridge. Link to comment Share on other sites More sharing options...
Alan de Enfield Posted May 17, 2019 Report Share Posted May 17, 2019 (edited) 17 minutes ago, Mike the Boilerman said: Oh and there is another problem, I suspect, with those step-up devices. I bet they really do only step up to 24V, or a bit less. 24V stuff is only nominally 24V and actually expects to be fed with 25.0 to 28.8V under normal circumstances. Feed things like water pumps and fridges with 23.5V from a converter and they'll run sluggishly, or not at all (I suspect) in the case of a fridge. 11-16v Input, stabilised 24v output. https://www.aliexpress.com/store/product/12V-TO-24V-100A-STEP-UP-DC-DC-CONVERTER-100-AMP-2400Watt-H100-12-24-Daygreen/1487825_32689386862.html?spm=2114.10010108.1000023.16.6ab76dceuZQWpq US$ 670 - not cheap. Edited May 17, 2019 by Alan de Enfield Link to comment Share on other sites More sharing options...
MtB Posted May 17, 2019 Report Share Posted May 17, 2019 6 minutes ago, Alan de Enfield said: 11-16v Input, stabilised 24v output My point exactly. 24.0v is not what nominally 24v gear is designed to run on. Link to comment Share on other sites More sharing options...
Alan de Enfield Posted May 17, 2019 Report Share Posted May 17, 2019 (edited) 16 minutes ago, Mike the Boilerman said: My point exactly. 24.0v is not what nominally 24v gear is designed to run on. Exactly. Edited May 17, 2019 by Alan de Enfield Link to comment Share on other sites More sharing options...
MtB Posted May 17, 2019 Report Share Posted May 17, 2019 19 minutes ago, Alan de Enfield said: Exactly. Its actually impossible to find a step up device that steps up to the 26v you actually need. They all step up to 24.v Until you realise the thing to buy is actually a 12v to 24v step-up battery charger. Link to comment Share on other sites More sharing options...
ditchcrawler Posted May 17, 2019 Report Share Posted May 17, 2019 Try a breakers yard that also does comercial, that is where I got my first 24 volt alternator from Link to comment Share on other sites More sharing options...
Alan de Enfield Posted May 17, 2019 Report Share Posted May 17, 2019 Just now, ditchcrawler said: Try a breakers yard that also does comercial, that is where I got my first 24 volt alternator from I thought of that, but Col is going to need help to ensure that the fittings will match up with what's already on his engine (mounting brackets etc) He has already spent money buying 'stuff' that is not suitable and has resulted in spending more money to make it fit. Surely better to pay a little more in the 1st place, get a new alternator with a warranty and one that fits the brackets and belts already on the engine. No more expenditure or bodging needed. Link to comment Share on other sites More sharing options...
Boater Sam Posted May 17, 2019 Report Share Posted May 17, 2019 Bodge it now and then have to bodge it again when you need a replacement, its not the best way. Link to comment Share on other sites More sharing options...
bigcol Posted May 17, 2019 Author Report Share Posted May 17, 2019 (edited) 3 hours ago, Mike the Boilerman said: That's helpfulness beyond the call of duty Alan. Have a big fat greenie! 3 hours ago, Alan de Enfield said: I would imagine that a suitable 12v - 24v step-up that would handle the output of a (say) 70 or 100 amp alternator would cost in excess of a 24v alternator. Try some truck supply places. I have phoned the local one I use and they passed me onto their electrical specialist (Gary Hare) I have spoken to him and he said "don't go down the 12v to 24 volt booster it just adds unreliable complexity and will cost a fortune to get one big enough anyway". What he has said is that if you provide him with the model number off the 12 v one you already have he will match it exactly (mounting brackets, pulley size / design etc) with a 24v version. Alternatively good photos with some dimensions and he could probably work it out. You then simply bolt it on in the same place using the same brackets. He even offered to come out to the boat (if you were local and sort it out for you) 40a - 50A 24v alternator prices start at £50-£60 but he could not give any idea of what yours would cost without more detail. Should you wish to call him his number is "079 three 0560 six 3 seven" Hope that helps. Both of you have more greenies now Edited May 17, 2019 by bigcol Link to comment Share on other sites More sharing options...
bigcol Posted May 17, 2019 Author Report Share Posted May 17, 2019 2 hours ago, Boater Sam said: Bodge it now and then have to bodge it again when you need a replacement, its not the best way. Yes, I always seem to go down that route, okay will find a alternator sam you are so right! col Link to comment Share on other sites More sharing options...
Alan de Enfield Posted May 17, 2019 Report Share Posted May 17, 2019 21 minutes ago, bigcol said: okay will find a alternator Happy to help (if you want me to) using my contacts at Newark Truck Parts - just let me know the make model etc of the existing 12v one and I'll see if we can get a match. I'll not be offended if you want to sort it yourself locally. Link to comment Share on other sites More sharing options...
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