Batteries

[aquaplane]

Post W/E update.

We have been giving the domestic battery some pain this W/E, the heater has been on most of the day time except when I moved the control box to the forecabin so I can turn it on/off from bed

The battery was about 12.4V Saturday lunch time so we motored down to the Wardens for tea just to put some charge in it. It was 12.7V when it had rested a bit after arrival.

By 14:00 Sunday it was 12.1V, with the heater running but as it had stopped raining we motored back to Waterhead. After starting the engine, the engine battery had been 12.7V, I soon put the switch to Both. Half way up the lake I looked at the engine battery and it was gassing merrily so I put the charge into the domestic battery only.

About an hour after arrival the domestic battery was showing 12.7V again with no load, the sun was out

I assume that the engine battery was gassing because the alternator was pumping out Vs but my system isn't bright enough to send them to the domestic battery preferentially?

I was quite suprised that the 110 Ah domestic battery went from 12.1V to 12.7V with only 1 and a bit hours charging.

I didn't bother to rig the new pannel as it didn't seem to need it when we left.

The alternator is behaving it's self again, it worked everytime the engine went on which is more than can be said for it's performance over the last month/6 weeks. Intermittent faults, don't you just love 'em?

[sahona]

I suspect the battery monitoring regime may be spoiling the original concept of your dream afloat.
(and I am speaking as a long-term paranoid amp-snooper)
If you've got it going and the standard ships (volt/amp)meters are stable, I suggest you focus on the genoa leach, and stop that bit at the top flapping when you ease the sheets. Far more satisfying getting 'in the groove' than worrying about what's wrong under the floor.

[aquaplane]

Nay lad, I'm just trying to understand what's going on, then I'll decide if it's worth letting Vs get in the way of sailing.

I still have the oil lamp and the option of going to bed when it gets dark.

[ash]

Post W/E update.

By 14:00 Sunday it was 12.1V, with the heater running

I was quite suprised that the 110 Ah domestic battery went from 12.1V to 12.7V with only 1 and a bit hours charging.

If the 12.1 was measured under load, then it won't give a realistic figure for % charge.

12.1 to 12.7 would represent a 60% of 110 AHr = 66 AHr in 1.5 Hrs = 44 A output !!! Would't be many horses left to drive the boat.

Post W/E update.

I assume that the engine battery was gassing because the alternator was pumping out Vs but my system isn't bright enough to send them to the domestic battery preferentially?

The theory is that it should self regulate - the higher voltage of the fully charged battery should mean that all the amps should go to the other battery.

You should have a look at the voltage when motoring - the alternator is maybe putting out too high a voltage - my theory as above would then fail.

My digital multimeter is permanently wired into the fuse board with a longish wire so I can easily check voltage of either battery by use of the O1B2 switch. I try to remember to check the voltage first thing in the morning before switching on any load. I also like to make a check when motoring.

My newer 'leisure' battery never reaches as high a rest voltage ( 0.15V down ) as the older car starter style one.

Sahona might be right in that we shouldn't get too bogged down in the amps but I do like to keep an eye on things. I quite fancy treating Mistral to the newer surface mount Nasa Compact BM1 which you can now get in a grey case.

My crew likes to use the 12V vacuum to give the saloon a quick clean before leaving the boat so my domestic battery is always left with a bit off the top even after a long motor - I don't leave a mains charger on - a small solar panel might be the answer.

Ash

[ash]

I saw this at Maplins http://www.maplin.co.uk/Module.aspx?ModuleNo=223251



for £12.50, on promo 'till Monday.

Bearing in mind we don't have much in the way of power draw, and no burning desire to install any, I was thinking that maybe it's worth £12.50 to see if it's big enough.

I see that Maplin have the 1.5 Watt Solar Panel on a Sale promotion of £9.99 until tomorrow.

Ash

Edit - just realised that Aquaplane's unit is the 2.4 watt so much better value - I wonder if that will come back on promotion.

[ash]

I see that Maplin have the 1.5 Watt Solar Panel on a Sale promotion of £9.99 until tomorrow.

I bought one, but suspect that I may have wasted my tenner.

The unit seems well built, comes with 4 suckers but only uses 2 to hopefully stick it to the glass, has 2 alternative connectors - cigarette style plug and croc clips - with a reasonable polarity conscious bullet connector.

Tests weren't extensive - were carried out in the bedroom window on an overcast January afternoon, used a small analogue multimeter, and used a fairly well charged 7 VA power supply as a load.

Open circuit voltage 18 V. Current when connected to 12 V battery - 2 milliamps !!!!

The output pulses, but I don't think that this is advanced technology - I think that it's just the flashing LED stealing some of the output.

I'll try again in more realistic light conditions.

Ash

[sahona]

I think that LED has to go! Unless you're pretending it's an alarm...
For any charging device, it's obviously got to be nearing 15watts rated before you get 1 amp, so theoretically the 1.5W job should give 100mA, on a good day, with a following wind and no birdsh1t or shadows cast by flying pigs on the cells.

[Arghiro]

FWIW,
I bought summat similar off e-bay for that price a year or 2 ago. It was bought for what it was designed for - to keep an unused battery topped up over a period of weeks or months. It is superb at that. I keep it under the sprayhood by the min window & the battery it is connected to stays charged over fairly protracted periods of neglect. The other battery (not connected to the panel) tends to slowly lose charge (as one would expect).

Basically, the panel guarantees that I will have one battery fully charged to start the engine, which will then take care of recharging both batteries easily. Do not expect to run a fridge or dehumidifier - or even an anchor light off a 10 quid panel!

But it does what I require & I am considering buying a second panel to keep both batteries topped up - but I don't really need both in top condition as long as the one will start the engine.

[aquaplane]

But it does what I require & I am considering buying a second panel to keep both batteries topped up - but I don't really need both in top condition as long as the one will start the engine.

That's reassuring, I connected mine up for the first time as we left last W/E and thought "if this works I may get another for the other battery", the chances are it's going to work.