dankenning

Yes it has a little fan, good to know they're quieter on float mode hopefully it makes it before I go to bed.

Right, it's wired up, humming away and the voltage is slowly climbing. I connected the positive to the protected side of the mega fuse (from the batteries) via an in line car type fuse. The negative is connected to the main negative busbar. Thanks for your help.

Thanks, that's what I thought. Should be able to get this up and running tomorrow morning now, thanks for your help.

Thanks for the reply. Can you tell me where the fuse is fitted?

I've just bought a 10a battery charger (thanks for your help choosing one). I was about to embark on wiring it up through the bulkhead to the battery bank next to the engine but ran out of light. Then I thought why not connect it directly to the battery cables inside the boat which are right next to the charger. Is there any reason why I can't do this, the battery cables are much bigger than I needed and connect to opposing sides of the bank. Thanks in advance for bmx advice. Sorry, should read any advice, i'm writing from a phone.

Just ordered one, i'll let you know how it goes.

Thanks for the replies. This is for a liveaboard but it is quite a simple boat. The fridge is quoted at 1.3A/h average over 24 hours. I will assume 2A for 24 hours. I might have any one set of lights on at a time over about 6 hours in the evening, max 6 and each bulb 10W. I will assume 6A for 6 hours. The water pumps may run for up to an hour, and is 10A. I will assume 10A for 1 hour. Over a day that is an average draw of 4A per hour. Assuming it is best to generally use the charger over the batteries it must be over 8A for the lighting and fridge. I have seen a Numax Marine 10A charger for £66.33 (see below). Is this the one that was mentioned? http://www.tayna.co.uk/Numax-Marine-Battery-Charger-10A-P6133.html

Hi, I have a winter mooring with a shore line and want a battery charger to use whilst i'm not moving the boat very often. I have 4 110ah Numax lead acid leisure batteries. The main draw is the shoreline fridge and I generally have to run the engine up to twice a week. I would like to know if I can use a small C Tek charger of about 7a to trickle charge the batteries or if I need to get something bigger.

Hi, I have been fitting out a boat over the last year with my partner and we finally moved on last month. I have learnt a lot of things in the process, but still have moments of stupidity... Yesterday before running the engine I made the usual checks and found that the positive battery charging cable mounts had slipped and the cable was very close to the alternator belts. I therefore decided to re route the positive battery charging cable over the engine temporarily so I could move the boat a short distance. I isolated the cabin circuit and loosened the nut holding the cable to the domestic battery alternator. Without thinking I moved the cable and shorted it on the other side of the alternator (I hadn't isolated the charging circuit) causing a lot of sparks in the process. After some time to calm down I had a look at the damage. The cable connection was black so I cleaned it up and connected it back up carefully. I checked the cabin circuit and the batteries which seemed to be discharging normally. I then ran the engine to see if everything was working. The engine started normally and the starter battery alternator warning light went out a few seconds later as normal. The domestic battery alternator normally kicks in when the engine is rev'd to 1500rpm but it didn't kick in. I rev'd the engine all the way to 2000rpm where the alternator light when out and the engine stalled simultaneously. My partner had checked the voltmeter during this time and it was up to around 14V as normal. When the engine stalled I had a look at the alternator and cable. The domestic battery alternator was very hot, whereas the starter alternator was only just warm. The first few inches of the positive battery charging cable (to domestic batteries) was also very hot. I am now unsure whether I need a new alternator, new cable or both. As the voltage was normal for charging how else can I test the system? Any help appreciated, Dan.

Hi Tony, thanks for your replies. I finished wiring the domestic battery bank yesterday and connected the domestic battery negative to the engine bed (above the vibration mounts) as the starter battery is on the other side of the engine compartment. I connected the domestic battery positive to the large alternator and removed the link wire between alternators. The domestic batteries were bought a while back and are well overdue a charge. The starter battery is well used and fully charged. When I started the engine both alternator warning lights came on and stayed on. The small alternator warning light looked like it had a bad connection and seemed to be pulsing slightly and the large alternator warning light was lit up steadily. The distribution panels have a voltmeter which had been reading 12.35V but shot up to about 15V while the engine was running. (Is this normal?) After running the engine for a couple of minutes the warning lights were still on so I turned it off and the voltage returned to about 12.45V. Any ideas? Thanks.

Hi, I am in the process of wiring up a domestic battery bank in a sailaway and have had a lot of help from this forum and www.tb-training.co.uk However, I am a little confused (still) about wiring the battery bank to the larger alternator. I have a wire linking the large and small alternators which has instructions to remove when adding a domestic battery bank (I currently only have a starter battery) and to replace it with the domestic positive to the largest alternator only. However, there are no instructions about what to do with the domestic battery bank negative so I checked www.tb-training.co.uk and found the following page... http://www.tb-training.co.uk/twinalt.html In the top schematic the domestic battery bank is only wired to the domestic negative busbar and not to the 'main engine negative connection'. Is this correct for me as well or is there an error or subtlety that I haven't picked up on? Any help greatly appreciated. Thanks, Dan.

Thanks for all of your replies. Sounds like I should either go with 50mm for 12V only or 70mm if I don't want to wire the inverter separately (if I get one). Decisions, decisions.

Thanks for your reply Mike. After a quick search I have found that 50mm^2 cable is rated to 204A continuous current. As it is protected by 150A fuse it should be fine in this respect. The other think you mentioned was the volt drop. Apparently the cable has a volt drop constant (MV/A/M which I assume is mV/A/m) of 0.45. With a 5m run and 100A continuous current this is a 0.225V drop. Does this sound excessive bearing in mind that there will be more voltage drop over the rest of the cable. Otherwise with a 70mm^2 cable the voltage drop will be reduced to 0.160V (volt drop constant is 0.32). Good point on the inverter, I will probably look for something smaller if I decide to go down that route. Thanks Smelly.

Hi, I am fitting out a widebeam on the Kennet and Avon and looking to fit the batteries in the next week. The run will be about 4-5m from the battery bank (4x110Ah) through a 150A mega fuse, battery isolation switch and to the positive busbar feeding the 12V distibution panels. At the moment the boat is only 12V but in the future I may fit an inverter (probably 1kW). I was planning to buy some 50mm^2 cable. Will this be sufficient or should go splash out on some 75mm^2? Should I also use this cable to connect the batteries of can a smaller cable such as 35mm^2 be used due to the short lengths? Any help is greatly appreciated, Dan.

Hi, I am fitting out a widebeam on the Kennet and Avon and looking to fit the batteries in the next week. The run will be about 4-5m from the battery bank (4x110Ah) through a 150A mega fuse, battery isolation switch and to the positive busbar feeding the 12V distibution panels. At the moment the boat is only 12V but in the future I may fit an inverter (probably 1kW). I was planning to buy some 50mm^2 cable. Will this be sufficient or should go splash out on some 75mm^2? Should I also use this cable to connect the batteries of can a smaller cable such as 35mm^2 be used due to the short lengths? Any help is greatly appreciated, Dan.