Cahrging my Batteries?? (Long + several pics)

To measure the current you put your meter in series with the line/wire. In this case check the ranges of your multimeter, for "A"mp measurement there will be some low ranges such as 10mA, 50mA, 500mA and possibly one for 10A which requires you to put the meter +ve lead into a separate socket on the meter. Start off with the highest range and take the yellow lead off the B+ point then attach the +ve of your meter to the B+ terminal and the -ve of your meter to the yellow wire. Hook it all up before you start the motor. If the reading is very low, as I suspect it will be, change to a lower range on your meter but turn off the engine if you have to unplug the probe - it shouldn't cause a problem to lift the sense lead off when the motor is running but why tempt fate.

Just in case your batteries are fully charged, make sure there is a decent load whilst you are making the measurement - put a few lights on.

As regards the 4 diodes in my fridge fan circuit, yes that is just what happens, 4x0.6=2.4V (give/take). Actually there is another in the cct so I get a 3V drop which allows the fan to run slower and circulates air around the fridge to even out the temperature. Without this I found that stuff next to the evaporator would keep cool but in the back corners the temperature rose quicker. But that is a whole new subject that you can get onto after you sort out your batteries.

Now before we get too carried away, remind me, what is the maximum voltage you have seen at the alt B+ terminal - 13.6V or 14.4V? Remember if this trick works it will boost the volts by 0.6 or 0.7 and that may not be advisable if you can actually get to 14.4V already.

Just to give you some real info on the process of the diode. Jim raised the question of the voltage drop if the current is low. I made some measurements this morning. We always talk about 0.6v across a silicon junction (diode) but it does vary a bit with voltage and temperature. Spec sheets typically show 0.6V to 1V. Here are my readings for a 1N4002 with 13V supply
I = Current thru diode
PD = Votage drop across diode (potential difference)
R = Series resistance from diode cathode to -ve
I PD R
1.0mA 0.584V 12kohm
2.8 0.627 4.7k
5.75 0.658 2.2k
67 0.766 180ohm
300 0.826 40ohm

So you can see that as the current increases the voltage drop does too, but not linearly. I expect the I through the yellow wire to be quite low but we won't know until you test it. The sense line on my Balmar regulator is fused at 1/8A (125mA) but that is only an indication of what to expect.

If the sense wire current is lower than 200mA your 1N4148 could be used. The trouble is we don't know the range of current drawn under all circumstances. Measure first, decide action next.

Good luck
 
Re: Cahrging my Batteries?? - Lost My Rev Counter!!

[ QUOTE ]
It looks like you have a sensing wire from the reg to the large output cable, extend this to the service battery, and the alternator will compensate volt drop.

[/ QUOTE ]

So I've extended the sensing wire to the domestic +ve terminal and, whilst the alternator still provides a charge, the rev counter doesnt work.

reconnected the sensing wire back to the alternator, and the rev counter still doesnt work.

The grey wire feed the alternator, (and I havent even touched it), the brown wire is D61, whatever that is.

Back on battery sensing now, charging at 22A at what I think is about 1500 revs with the monitor showing the batteries -50Ah depleted, (220Ah bank)... not sure if that's an improvement.

Help!

Richard
 
Re: Cahrging my Batteries?? - Lost My Rev Counter!!

May be a stupid suggestion - but you have checked the engine key is in the right position for the rev counter to work (ours sometimes springs back to the 'Off' position once the engine starts and needs turning back to 'Ign' to get the rev counter to work - apparently the spring in the barrell is worn which is causing this - worried me the first time it happened!)

Incidentally - we had loads of trouble with our charging - the domestics weren't charging at all, all the wiring was a bit amateur etc. The guys at Merlin are really helpful and gave lots of advice - saw them again at SIBS this weekend to buy a battery monitor and the chap I spoke to was very knowledgable and spent over an hour suggesting ways to improve our system and drawing diagrams etc. May be worth a call / email?

Jonny
 
Re: Cahrging my Batteries?? - Lost My Rev Counter!!

I did not realize the thread was still going!

If that yellow lead is a sense wire, and you made a bad connection or had the diode reversed then the regulator will see too low a voltage and so will drive the alternator to maximum output. Since the batteries are low the batteries voltage would not have risen much.

However the AC voltage before all the diodes could have exceeded the input of the tacho meter. Failing that you have just broken the lead to the tacho. The tacho sees the AC side of the diodes through W and displays the frequency (RPM).

Another issue is you can not just lengthen sense wires. They are either high impedance and suffer from noise, or are low impedance and the sense wire drops a voltage. Normal sense wires are taken as twisted pairs.

The function of the sense wire is to sense after the diode losses. Normal alternators sense just the D+ value and therefore the equivalent of B+ at a low current. This means that your alternator will compensate for the losses in the diodes from their internal resistance.

The danger of a sense wire becoming disconnected is quite real and can lead to alternator fires. Most alternators are not designed for continuous operation at high charge rates.
 
Re: Cahrging my Batteries?? - Lost My Rev Counter!!

Neil, I didnt put a diode in the sensing wire, so it cant be that, but there is obviously a possibility that there was a bad connection.... If there was, it was momentary, as I was constantly looking at the voltage and amps going into the batteries and neither were over the top... max amps I saw were about 20, and max voltage at that time 12.8.

Having said that, if I might have blown the tachometer, how can I test for that, or a broken wire, (It's hard to see how the wire has broken as I havent been near it, so it would have to be pure coincidence for it to happen at that moment).

and, if I have blown the tachometer, is it likely to be repairable, or is it a new meter?

Whilst I have obviously been listening to advice here, I have done nothing that isnt suggested in Nigel Calders book - he makes no mention of a sensing wire extension having to be of a particular type, but he does caution against a bad connection.

I think what I will do is put the sensing wire back on the alternator, and leave well alone till I get somewhere, (Malta), where, if something debilitating were to happen, I have time to sort it.

I can live without a rev counter for a while, but it would be good to get it going again if I can.

Thanks for the advice

Richard
 
Re: Cahrging my Batteries?? - Lost My Rev Counter!!

Sorry to hear of the loss of the tacho. Possibly a disturbed wire. Can't think of any other reason apart from the disaster alternatives suggested by SolarNeil which I would rather ignore for the moment.
You won't see any benefit from moving the sense wire in those early high current minutes/hour because the voltage is already lower than the maximum output. It is more important when approaching full charge when the voltage at the battery needs to be slightly more than the full charge V to get any more current into the battery.

The reducing charge rate you described elsewhere is quite normal. They absorb less as they are more fully charged. That is where smart chargers/controllers start to be useful. They increase the output voltage to maintain a constant charge current until the voltage reaches a preset level (determined by the type of battery) - this stage is known as the "bulk" charge. Then the voltage is kept constant (typically 14.4v) in the "absorption" stage during which the battery will take a continually reducing current until it is calculated to be charged and the 3rd stage of "float" is entered. The controller logic has to consider the temperature of the battery and either limit it's time in each stage and/or have temperature sensors on the batteries to provide it with real-time information.

Englander commented that your 220Ah domestic capacity is low for a liveaboard - I agree, you should think of doubling it so that you are far less at risk of discharging down to the danger zone of 50% (or 12.1V).

In the meantime, I agree, you are better to leave things as they are until you can get to Malta with time and resources to take you further.
Ray

PS. If you do decide to experiment with the diode, the end of the diode which has a band around it is the CATHODE.
 
Re: Cahrging my Batteries?? - Lost My Rev Counter!!

I was only trying to point out the dangers of sense wires. Yes, almost likely that something was disturbed but there are other reasons to consider.

I will be blunt. Even if I knew all the wiring of the boat and knew a solution, and I was there, I would not work on a boat when it was out of a secure environment. "I'm anchored off Sicily" does not qualify. I was trying to counter some of the people encouraging Richard to start experimenting.

Disturbing any boat electrics is always a problem. At present it works. OK poorly, but it works.

I have fixed many boats in anchorages (in fact 2 in an anchorage not too far away from Richard) with battery problems but these have always been when the boat is in such a state that it can not leave or was towed in.

So far he has lost the tacho. But it could have been the starter wires that were disturbed or those relays that seem to be oddly mounted and in direct line of the water pump spray gap.

If the Alternator was at full output then it should be producing about 55A. If it can not produce full output when the batteries are low then there is no chance. It is nothing to do with the sense lead. It has more to do with resistance in the charging circuit after the alternator. In the original form, if that resistance is high the Alternator would not be at maximum output as it sees the higher voltage at the Alternator and limits its output.

Although they are called voltage regulators, they are actually voltage sensed current regulators. It is the battery that determines the voltage for a given current. Without the battery you can get over 100v from an alternator if you remove the sensing.

If the wire is taken to a lower voltage point (or shorted to 0v) then the Alternator would go to maximum output. However by having all that resistance and trying to make the Alternator produce 55A the internal voltages will be much higher than the original designers would think normal. Since the internal coils are producing full current but at a much higher voltage its power consumption and losses are higher and so will cause more heating and failure.

Do what you will but when peoples lives are at risk I take care.
 
Re: Cahrging my Batteries?? - Lost My Rev Counter!!

[ QUOTE ]
I will be blunt. Even if I knew all the wiring of the boat and knew a solution, and I was there, I would not work on a boat when it was out of a secure environment. "I'm anchored off Sicily" does not qualify. I was trying to counter some of the people encouraging Richard to start experimenting.


[/ QUOTE ]

Neil,

I think we're all agreed.

As I've said... I'm calling it quits now and will do more when I get "secure".

Thanks for the input so far, (including the warnings).

Richard
 
Re: Cahrging my Batteries?? - Lost My Rev Counter!!

Neil I agree with almost everything you have put forward but I suggest Richard is highly unlikely to get more than 40A into his batteries even when they are flat. His bank is only 220Ah and as you would know batteries will only take about 20% of their capacity during charge. The other factor is that we don't know what the "gearing" is like on the alternator i.e. crankshaft to Alt pully. It may be that he can never get full output from the Alt at reasonable revs and probably not at those he would run his motor at at anchor.

But from the beginning I have suggested he wait till Malta and I have given him a name of a helpful and (I believe) honest person to get started with.

The problem Richard faces is that he naturally wants to understand it all and has a steep learning curve. However, all that he can learn about electricity and electronics in the process will help him immeasurably as he continues his cruising - and he will have knowledge and experience to help others as you have along the way.

We will have to wait till he gets to Malta for the continuation of this tutorial.

But returning to your forum name - SolarNeil - I hope Richard opts for a good dose of solar current in his solution. It's free, quiet and is much easier to control/regulate.
Ray
 
Re: Cahrging my Batteries?? - Lost My Rev Counter!!

To come back to your boat after a hard days exploring to find that the batteries are all full is wonderful. So many times we have heard, "Sorry, take a rain check, we have to go back to the boat to charge before it gets too late to run the engine/generator"

There is a boat in the Caribbean with 1KW of panels and they run the watermaker directly off it midday.

As for learning then you need to find someone to draw the full charging circuit (with approx distances) and then we can go through it at our leisure.
 
Re: Cahrging my Batteries?? - Lost My Rev Counter!!

[ QUOTE ]
There is a boat in the Caribbean with 1KW of panels and they run the watermaker directly off it midday.

[/ QUOTE ]I'm in the Med with 370W solar panels, and I make 20 litres per hour of fresh water direct from my panels from my Spectra watermaker from around 1030 to 1630 AND give useful charge into the batteries as well as running the laptop, fridge, pumps, etc.!
 
You must log in or register to reply here.

Share this page

Top