So .... charging is now sorted - onto back-up systems

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I have for small money completed a satisfactory charge system that keeps my two battery's in reasonable condition - based on regular provision of shore-power.

Now onto a development that I have in mind. Various items on the boat do not need high power supplies .... and only draw mA's ..... such as GPS, E/Sounder, Navtex etc. The power drain is low. So why have them always on the main domestic battery adding to the drain of auto bilge pump etc.

My idea is to consider inserting a Gel-Cel Alarm battery into the system .... only a small one is needed at each station..... with provision to switch back to main domestic if necessary. They can be charged very easily via mains plug-in chargers similar to a mobile phone type.

I am also close to completing the 12v transformer system to run of the 240v supply as well ...... this will give rest to battery's when mains is availble, but be able to utilise 12v fittings still.

None of the above is cheque book busting figures !!

So has anyone else used Sealed Gel batterys like alarm case ones ? Fitted 12v transformers etc. ? Interested in like minded budget people on this ......

(I'm not about to spend out on expensive Marine stuff ... so please ......) /forums/images/graemlins/tongue.gif /forums/images/graemlins/tongue.gif /forums/images/graemlins/tongue.gif
 
Hi Brian ....

I must get round to sorting the VSR with you .......... I know its been a long time since last discussion.

Yes ... but a little too sophisticated for my old tub possibly ...

Def. food for thought !!
 
Will your 12v transformer system be rectified to give DC or is it just going to supply the lighting circuits? If it's not rectified then it needs to be isolated from the normal 12v supply when not in use, or the secondary winding will be a drain on the DC supply - but I guess you thought of that already.

Will your charging system not already supply 12v (DC) to the boat when on shore power?

I'm interested in the small 'alarm' batteries. I was thinking of using one to drive all the instruments. The advantage being that it would help isolate the instruments from noise, glitches and surges that might occur on the domestic 12v DC supply. The idea would be to have it on constant charge from the domestic battery.
 
Re: Hi Brian ....

Hi, depending on the VSR control module, it's included with the link starting, you need only supply your own relay if you want to be penny pinching.

Brian
 
I have a 100W 240v - 12V transformer that was cobbled together to run Car radio-cassette and amp / Graphic equalizer years ago. It has zener + large can capacity to smooth etc.

All it needs apart from connecting up via a switch - is to box it.

So yes I have thought of the DC aspect.

Considering how small you can get the sealed cell battery's - they could also serve as individual items ....

Charging of the 12v system ? Mmmmmmm hadn't thought of that .... but doesn't that bring noise etc. back into the equation by virtue of connected again ?

12v from charger ? No as I use a bog standard car charger .... not a charger / power supplier.
 
[ QUOTE ]
Charging of the 12v system ? Mmmmmmm hadn't thought of that .... but doesn't that bring noise etc. back into the equation by virtue of connected again ?

[/ QUOTE ]Well possibly. I'm thinking of charging via a simple constant current regulator (home made) to limit the charging current to whatever is safe for the alarm battery. I reckon the impedance of this circuitry would be pretty high compared to the internal resistance of the alarm battery so would remove most of any noise, glitches, etc..

I remember there was a thread about this sort of idea some time ago and someone suggested using one of those humungous capacitors that are used for car audio rigs instead of using an alarm battery. The advantage of the battery is that I happen to have one that's doing nothing at the moment. /forums/images/graemlins/smile.gif
 
Another extra thought .... solar charging ...

I have used the Car trickle solar chargers before .... but they didn't keep up with batterys in the end and I stopped using them.

A Sealed battery - such as used in Alarm cases - could one be charged from such a solar panel ... the cheap car trickle jobs you see designed to stop car battery going flat when stood ... would it need anything between it and the battery ?? My thinking is the ampage is low and wouldn't hurt the sealed battery ????
 
Have to admit also ....

That a lot of what I'm using has been catching dust on the shelf .... so is free stuff. But even so - overall if I was to buy - would not cost a great deal and provide what is needed. Maplins and other shops have keen priced Sealed Batterys and chargers .... so why not ??
 
Re: Have to admit also ....

I can't help feeling that you are going overboard with electrics. Small SLA batteries are easily killed with overcharge however you can get integrated circuits deigned for controling the charging of small SLA batteries. The down side is that they need far more than 14 volts to start with so you would be able to only charge from a transformer/ rectifier on mains or a solar panel.

Bringing a touch of reality to sbc question. Forget SLA batteries solar chargers etc. The best is the simplest dual battery normal boat system. I think a VSR is the best way to recharge them from either engine alternator or mains battery charger. Complex is crazy... olewill
 
Disagree .....

If you look at a House alarm system .... you have on some - mains supply via drop down and then a back-up power supply from SLA. There is nothing OTT or complicated about it.

I have a twin battery arrangement like most .... without fancy add-ons. The VSR is a definite add-on I will make later.

What I am talking about is reduction of use of the battery systems on board .... by introducing a 240 - 12 transformer, and back-up power to instruments via SLA.

Ok - let me explain why I look at this ..... I intend to sail my boat on an extended trip in the future .... that is UK to Baltic. I wish to add "emergency" back-up to instruments that does not rely on present wiring or power supplies. Breaking up the power requirements into small SLA units will give me power but without filling up precious stowage space with another Wet cell battery. It will also be an independent power source.
The charging is not a problem - they are available from various outlets ...

I am not falling into the never-ending cheque book trap here .... I am looking at ways to provide as well as safely. A SLA will survive any knock-down / even a 360 roll ..... a Wet cell will have spilled and be liable to serious problems .....

I am sure that like all things - each has their own way or ideas ...... same as cars - I don't like BMW, I prefer Volvo .... but another will hate Volvo .... so why not roll with the tide and give it thought ......

/forums/images/graemlins/tongue.gif /forums/images/graemlins/cool.gif
 
Nigel

I have adapted some of my wiring with a future, similar modification in mind. This relates to my VHF and GPS which I class as fundamental safety / rescue items, and I have wired them to a dedicated sub-system with bus bar and fuse box. This also has a 3 pin waterproof deck socket, more of which later.

Currently the above is direct to battery No.1, which is ordinarily reserved for engine starting, and the above instruments, and would only be below 99% charge after a long passage with VHF and GPS on. No.2 serves other domestic duties and is often deeply discharged. Both batteries are tail-lift truck spec. (I forget the number) so are totally interchangeable in use, via a Off/1/2/Both switch.

Subsequently I intend to power this circuit with the 2 vital (even more so if I ever go over to DSC) instruments from battery No.1, via a split charge relay to a sealed battery dedicated to the task (same technology / same charging). My rationale being that in the event of serious flooding and eventual fading of main batteries, fire or major electrical melt-down, the VHF and GPS (for position) are fed by a well charged dedicated battery isolated via the relay. It need not be large, and can be securely mounted high in the hull. It requires only enough reserve AH to talk to the relevant people in the event of a certain class of calamity. Clearly you could use such a sub-system to supply as much or as little as you choose.

As for the 3 pin socket, The large pin is -ve, one small pin is +ve and fused back direct to battery No.1, the other small pin is +ve and wired to an auxiliary fuse (marked 'Bilge Pump' as it happens) on the main fuse board. If I want to supply power, for instance to the roving bilge pump or spot-light, the relevant plug is wired to the +ve pin supplied by the swiched supply from the auxilliary fuse. My solar panels deployed on leaving the boat are wired to the 'direct to battery' +ve pin of this socket. Plug that in and charging takes place whilst all other electrics remain isolated.

As for the 12v transformer, any auto charger of sufficient capacity will take care of the domestic loads whilst present, with the battery bank providing the buffer in the event of over demand. Indeed, your batteries will love this, constant trickle, occasional slight discharge at periods of high demand followed by immediate replenishment. They have no need for a rest.

I don't fully understand why you would want the hassle of designing in a further sub-system, particularly when power supplies behave oddly (hopefully cut-out not burn-out!) when over stressed by certain loads - those that a battery buffered system will feed with ease.
 
The chargers I have are not that high a power ..... so would have difficulty coping with demand. I know I tried with the standard charger without float - the internal trip went when I switched on lights etc. Switched them off and within a few sec's clicked back charging again. (The charger is one of those that clicks on / off if battery is really low ... till battery is sufficiently part charged to take constant charge).

So I cannot wire in charger as support for 12V systems .... if I had a higher power charger - yes totally agree. I'm not about to buy one - when I have the transformer already at hand .... so problem solved with already "shed" goodies !!

The SLA idea is as you say an emergency consideration as well as reducing drain on main battery banks ...

A VHF tx's at 25w max ... allowing losses say .... 30W .... which is 2.5A at 12V .... for a short period .... rx' is at mA's .... so power demand is actually low but SLA needs to be able to supply that 2.5 - 3A in short bursts ... Size of SLA ?? I reckon a 3 A/hr would be sufficient given that normally it would be charged and only listening 99% of time.
 
Another thought if you really are concerned about a backup supply would be to get a set (8) of good dry cell D cells in a box all connected together with a connector that could enable you to connect to your VHF or GPS in lieu of the main supply. Alcaline batteries should be good for a season easily. The major risk would be in corrosion of battery contacts. Keep em in a sealed box with silica gel or similar moisture absorbant. My guess is they would be more reliable than SLA and of course no charger needed.... olewill
 
D-Cells ...

This actually harps back to days of the Seafarer Echo-Sounder. You could take the back of and insert a 9v Lantern battery for power. Worked well as well.

I have thought in past about recharge packs - similar to elctric race cars (Scale RC) .... they have high capacity ~ up to 1.7A/hr and scaleable in voltage. But price is then increasing.

The whole idea is still forming into final config and nothing's cast in stone yet.

I can go 4 days comfortably on present on-board batterys .... so what we are looking at is "redundancy" and "safety back-up" really.
 
I forgot your normal source of batteries! So they are normally under voltage but sufficient for light loads only.

I hope your transformer is a big one. You will need to rectify and filter the transformer output, limit the current and provide considerable heat sinks / ventilation, otherwise you could easily start a fire with such a set-up. Unlimited the transformer will happily melt itself down and ignite it's surroundings. You will also need to arrange switching to separate your (charging) battery bank from the domestic bus-bar, which will be fed by the transformer.

A cheap analogue charger feeding the batteries would be far simpler and better for the batteries. It might even work alongside the digital charger you have.

If you can't bear to buy another charger, you could turn your transformer into one quite simply - probably simpler than your proposal - if I understand you correctly.

For a robust PSU design try:
http://sound.westhost.com/project77.htm

There are plenty of lead acid battery charger designs on the web, but most tend to be low current applications, for alarm back-ups and battery powered home Hi-Fi. Gooogling may provide some answers.

Andy
 
Now I am completely confused andy ....

I have a 12v 100W transformer made up from components that were sold as a kit many years ago. A block wound transformer with various input tags 240 - 120V .... and ouput tags 12 - 24V
A Zener diode and a big can capacitor .... all in a pcakage about 4" L x H x W ..... square block in fact.

It was built to power a Booster / Equalizer and car radio when I was on the ships ...

It is not for charging anything - just to supply 12v to boats domestics .... not serious loads - just lights etc.

Fires ? Filters ? etc. etc. ?????? Why I'm not talking some humongous affair ....

Blimey - it's even been used to run my Coolbox in my caravan at times .... from mains ...

It has a barely discernible hum that once mounted in suitable locker box etc. will be fine. Ventilation will not be a problem - as even when pushed its temp. never really rose that much .... just a few degrees.

I take your points though as concern for safety - and that will be observed.
 
Re: Now I am completely confused andy ....

Hi SBC I don't know whether you use the term Zener diode with accuracy. A zener diode is a diode which when voltage over loaded in the reverse direction (where a normal diode blocks current) will start to pass current at it's zener voltage ( and stop passing as voltage falls again). So a zener diode passes current as the voltage of a power supply begins to exceed the zener voltage ie the voltage you want to limit your power supply to.(by simply wasting it) It is necessary to have a resistor in series with the load and the zener diode to drop the voltage.(help with the required waste) In some cases the power supply transformer will drop the voltage by its own internal resistance but usually the power supply can melt the zener. A zener is usually rated at .3 watt or a large one at 1watt dissipation.
So a zener is only suitable for low power supplies or situations where current drain and voltage do not vary very much.

The zener is usually used in a circuit where its voltage is used as a comparitor to a control transistor. in this case almost any power can be regulated and controlled. Purpose designed regulator chips are cheap and contain the zener and the pass transistor but usually are limited to a few amps.
The simplest arrangement in your case is to have a power supply ie transformer recifier regulator that gives a regulated 13.75 volts. This will charge the battery and or supply current to lights etc very much like the generator on you boat engine or car. The down side is that the transformer recifier must provide at least 16 volts DC to allow for losses in the pass transistor or regulator and the difference is given off as heat.

A sophisticated charger will have current limiting and possibly stepped charge rates and you are back to buying a purpose built charger. These often use a switching mode to reduce the power wastage and heating.

In any case I would house any charger in a place or container that could handle a lot of heat in the case of a transformer melt down especially if you leave it on when absent from the boat.

PM me if you want to know more about do it yourself regulators..........olewill
 
Duh ???? It was a long time ago !! and i may have remembered wrong

The "Zener?" .... is a square black plastic block with 4 connections coming of ..... silly me !! It's the b****y bridge rectifier ... or whatever you call it !!

Anyway - the whole assembly supplies semi smooth DC 12V ... good enough to run car stereo without hum etc. It also was used for a CB set-up and that ran without hum which is common when using cheap power supplies on CB.

Sorry about my mis-info.

As I understand from my basic college electrickery .... I have a transformer capable of 120 - 240VAC input. Output is 12 - 24VAC into the rectifier. This is backed up by a large can capacitor to even out the wave form and smooth the 12VDC final output available at leads ....

Output rated at 100W max.
 
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