Posted: Wed Nov 12, 2008 8:56pm

hi,i am thinking of buying a numax 10amp charger for my 4 domestic batteries,is it possible to charge all the batteries together or will i need to disconnect them seperatly.At the moment i have a beta controller fitted which i was told controls the charge from my alternator when the engine is running this is a 70amp alternator for the domestic batteries only,i have second alternator which charges the starter battery separatly.As winter is upon us i want to keep my batterys charged while im away from the boat is this visable?Regards Andy

Posted: Wed Nov 12, 2008 11:08pm

It sees Numax only think this should be used for up 135 Ah capacity batteries and I have been unable to find a technical specification. It seems to be at least a two stage charger so you should be able to leave it connected for long periods without damaging the battery. However assuming your batteries are 110 Ah then you will be trying to charge a 440Ah bank with just 10 amps. As long as the batteries are fairly well charged I expect this will be adequate for keeping the batteries charged and possible doing the final little bit of charging, however if you fully discharge the batteries it will take a long time to recharge them. Normally the engine batteries are kept well charged by the engine alternator so I do not usually recommend a two output charger. I suspect all you will need to do for the engine battery is to transfer the charger to it for a day or so every month. This Si certainly more likely to be successful than those small "in window" solar charged that are supposed to keep your batteries charged. Tony Brooks

Posted: Thu Nov 13, 2008 9:30pm

hi tony would it be better if i upgrade the charger to a 30amp also from Numax which is capable of bulk charging and will it be o.k to leave connected,looking at there website this looks a better option thow pricey.Regards Andy

Posted: Fri Nov 14, 2008 8:44am

I think a 30 amp charger will be far better at RECHARGING a four battery bank in a reasonable time, however I am, not going to be pushed into making what in effect is a recommendation for a specific product. Especially when I have not been able to quickly find the "makers" website or get a full technical description. I spent time looking last night. Much depends upon how you use your boat and YOUR assessment of the advisability of using a charger that is not described as being suitable for marine use on your boat. If you are in constant attendance and can ensure it is in a damp & condensation free area then it should be OK. If, however, you are intent on mounting it in the engine bay of a steel cruiser stern narrowboat and intend leaving it unattended for long periods then I may have some concerns. All this assumes the charger will automatically drop back to a float charge at an appropriate time. I am afraid I am not willing to say any more the this on a public forum. If you want to know what I would do you will have to email me on a one to one basis. Tony Brooks