Charging batteries and regulators

[Amulet]

I have never had a good grasp of how this all works.

I have a wee Farymann diesel engine with an alternator built into its flywheel, a regulator on the back, and a cable loom of incomprehensibility back to my batteries warning lights etc.

I use the engine very little (sail everywhere), and I have trouble keeping enough charge in my batteries.

I would like to stuff more charge into them when they are really low and wondered about (a) faffing with the incomprehensible regulator, maybe replacing it with something more intelligent, or (b) putting another alternator on the prop shaft with its own system to beef things up.

If I went for (b) would it cause any problems to connect two different charging systems with their own regulators to the same battery bank? (I'd like to be able to switch it between banks and so they are both likely to end up on the same one at some point.) I'd have thought that all that could happen is that the regulator on whichever alternator was delivering the lowest voltage would simply shut it down and let the other do the work.

Or is this all madness?

 

[Oldhand]

I don't know your particular installation but it sounds similar to that fitted to a BMW D7. If it is similar, it employs fixed magnets in a ring inside the flywheel as the field magnet and non rotating coils inside the ring as the "aramature" magnets. This arrangement can't be regulated in the normal way by adjusting field current, thus only the actual armature output can be regulated. With such a system it is safe to assume it will not be compatible with any of the standard "booster" alernator regulators on the market.

If the above is applicable to your installation, you will require an additional belt or shaft driven alternator to improve your battery charging and should consider whether you are prepared to accept additional engine power loss as well as the expense of such an addition.

 

[rogerthebodger]

I have 2 small ferymann engines one with alternator on without. I have a manual and will dig it out tonight to see what info it has about the alternator regulator. I think it is a "black box" so no internal info.
Diesel power in mitcham can supply spares

www.dieselpower.co.uk

 

[halcyon]

What ever you do to your alternator, or fitting a second one, will make little differance to your problem, which is you sail every where.

As you run the battery low, recharge it very little, you probably have a sulphated battery, and your getting surface charge, putting you on a slippery down hill slope.

Spend your money a decent solar panel and regulator, and use the alternator as a little top up.

Brian

 

[Amulet]

Thanks for that. Yes I am a compulsive sailor. I have shore power and a Sterling charger which means in the marina I get sensibly charged up. Most of the year my batteries are all fine. Then I go on a two week cruise and want to run the autohelm all the time. Maybe a windvane steering system is the solution - but it's a teeny wee boat (8 metres but heavy). Most vane systems on the market would be a significant increase in sail area! I'm a also a compulsive avoider of marinas, and anchor in the most unlikely creeks. I don't like having to regularly find a marina for a power fix.

 

[Amulet]

Thanks Rogershaw - have got the manuals and the website.

I don't think I can solve this problem. Can't generate power if you don't run the engine. I have just bought pretty beefy sheet winches - would the crew notice the extra load if I bolted an alternator underneath them?

 

[halcyon]

We have vane steering and wind gen, on the the back of a 8M, have yet to try in anger. Though it has found the USA, so must work !!

Brian

 

[William_H]

It sounds like the alternator on your diesel is the same as that on small outboards. Regulation is by power wastage like a solar panel regulator.
You can not improve the output of the existing alternator.
Your options are to add an additional car type alternator preferably with smart regulator. or go for wind gen or solar.
I don't think anything but a large solar panel or large wind gen will provide the rapid recharge you want. Solar especially is good for long term low rate recharge and I read that you want occasional short term recharge.
Perhaps a seperate 240V gen to drive your shore battery charger woulld be most suitable.
An additional charge source will not normally concern an existing regulator it will just assume the battery is charged and stop charging. The new higher voltage charger will continue to pump it in.
olewill

 

[john_morris_uk]

The real problem is that you are trying to get something for nothing - ie lots out of the battery without putting anything back in. If you don't run the engine a lot or go alongside to plug in, you'll self evidently never put charge back into the batteries.

Solar panels and a wind generator will probably sort things out, but I also commend some sort of battery charge monitoring system. It concentrates your mind wonderfully about the amount of electrickery you are using, and makes you realise how easy it is to destroy the batteries by running them down, and how hard it is to keep them charged up.

 

[Amulet]

Dammit of course you are all right. I'm Scottish and trying to get something for nothing. If I had a wee bit more space I'd simply carry a small generator, but asking one of the crew to share their bunk with it is a bit much - though it might be a more attractive companion than some poeple I've sailed with.

I do wish I could find an even smaller petrol generator than the ones I can see on the market. I even wondered if I could make one using an engine designed for model cars.