Posted: Tue Nov 11, 2008 9:35am

hi there. was wondering if you could give me some help. we have a sterling inverter charger, 600 watts, this being connected to one of the three leisure batteries. we have then ran a 360 watt tile cutter with no probelms, whilst the engine has been running. when we come to turn the engine off we get no warning lights or buzzer sound, this being a beta 28 engine with control panel. when i try to start again no buzzer sounds whilst in the glow plug position and no lights come on, looking as if the battery is flat. but when i turn the red battery keys of then on and say leave it for a few seconds everything is fine. could you advise, thank you

Posted: Tue Nov 11, 2008 9:57am

Martin, I hope that you do not mean the inverter is only connected to one battery because if it is there is trouble ahead. even if you have a split charging system so a bank of two, plus the single "inverter" battery gets charged you will have reduced your effective battery capacity because the amount of electricity a battery can supply is dependant upon its charge and discharge rate. The slower charging & discharging are done the more a given battery bank can supply. Those who know more than me say one big bank is far better then two smaller ones for domestic use. I think the clue to your problem lies in the word "red battery key". These red key type master switches are well known for having "optimistic" specifications. I think that you passed nearly 400 amps through it all the time you were cutting tiles so it has over heated and melted inside. It is now not making a good contact. Test it either by bridging the two big nuts underneath it or by screwing up a piece of paper and putting it under the key. If the system then works please fit a new switch asap. Take time in choosing the switch - your inverter can draw about 600 amps for hours on end so a 500 amp for 2 minutes specification is no good for you. You are looking towards a large and expensive switch. In fact the best I could find in my catalogues are 250 amp continuous with 2500 amps for 5 seconds. Try to choose a switch where the terminal bolts are mounted in ceramic or a hard plastic that looks as if it will not melt very easily. Tony Brooks

Posted: Tue Nov 11, 2008 12:21pm

hi tony thanks for the reply. the inverter is connected to a bank of three batteries, obviously which are all linked then we have a starter battery as a well. could there still be damage inside the switch as i have not had a probelm after the initial fault. does this mean that the builder has not taken an iverter into account or does the nverter need to go through an isolation switch, as at the moment its direct with an inline fuse

Posted: Tue Nov 11, 2008 1:28pm

I understand the Boat Safety Scheme requires all batteries and the majority of circuits to be fitted with a method of isolation. If the BSS accept the fuse as a suitable method then its OK but my advise would be to ask the BSS by email so you have something to show future examiners. When you used the tile cutter you forced the alternator to full load. Now I do not know what type or specification applies to your charging system or how it is wired, but if its a single alternator then it could certainly have overheated the switch - especially if its a high output alternator. Heat causes things to expand and jamb and plastics to soften. I am at about of a loss to understand why it sounds as if the engine master switch played up, but it all depends on how the system is wired. It might be coincidence. I have known good quality switches suddenly go non-conductive until they are switched a few times. I put this down to some type of corrosion. If its working and the switches are not getting warm in use I guess they are probably still OK and it was just one of those odd things that happen from time to time. Tony Brooks PS If those tiles are going around a stove I trust you are not sticking them onto wood!

Posted: Tue Nov 11, 2008 11:30pm

hi tony, thanks for the info. i've checked the red switches and the fittings they go into and they both seem fine, with no signs of burnt areas. i also checked the voltage on each battery which was 14 volts per battery. everything was then fine when starting, running and turning the engine off, the engine has twin alternators. as for the inverter it was originally wired direct to the batteries of a friends boat, i then spoke to the builder of the shell and they said you have to wire the inverter through an isolation switch but when i spoke to sterling they said that you can connect it direct to the battery with the inline fuse. so i think i will ask a safety examiner, i think i will hire a generator until all works is done and until i can get some more help with the inverter. as for the tiles they are ones in the kitcheb & bathroom area only thanks again.

Posted: Wed Nov 12, 2008 8:56am

Please do not ask an examiner because much of the BSS must come down to opinion and I have seen boats that I would class as a fail from reading the regs, yet have just been given a certificate. Please email or write to the BSS direct so you end up with a definitive written ruling. That way you can show it to any future examiner who takes a different view. Tony Brooks