Electrical/ charging problems

[Ricco1]

A bit long winded this. Bear with me, thought I'd try to give as much information as possible.

 

I've been living aboard for a month now. As was suggested, it's a steep learning curve!

 

OK, my engine has a 40 amp alternator. I have 2 leisure batteries plus the starter.

 

I don't use a lot of electricity. I'm frugal with my 8 watt lights, have a 17 watt t.v.. Add a radio, pumps, netbook and phone charging, that's it. I estimate that I use 25 amps daily. Let's round it up to 30.

 

The problem is that I'm having to run my engine for at least 2 hours a day to produce that electricity. I regularly check the voltage with a multimeter. My batteries sit between 40% and 60% charge. The engine ran for 5 hours one day last week, when I was cruising but still, the next morning, the batteries were down to 40%. So it seems the additional 3 hours of engine running gave me very little, if anything.

 

A friend ran has ammeter clamp thing over my wires, while the batteries were at around 50%. This wasn't conclusive at all, showing between 8 amps and 18 depending on which were he put it round. The readings were up and down, all over the place.

 

Another thing I've noticed is that if I'm watching t.v. and run a pump, I lose the t.v. signal. If I plug in my computer to charge it while I'm watching t.v., the t.v. cuts off completely.

 

I know a 40 amp alternator won't often produce 40 amps but I would have expected it to produce more than what appears to be an average of 12 to 15.

 

Any thoughts, hints, ideas?

[nicknorman]

How are you measuring the state of charge? If with just a voltmeter, are you doing so after resting the batteries for at least an hour with no load on them?

 

What is the voltage whilst the engine is running, towards the end of say 2 hrs charging.

 

If you keep the batteries between 40 and 60% state of charge for a long time they will die quickly due to sulphation.

Edited October 11, 2013 by nicknorman

[by'eck]

I suspect your power usage is under-estimated. Further your two batteries (110 amp hour each?) have probably lost a fair amount of their capacity. This leads to the engine alternator (even a 40 amp one) quickly re-charging what capacity is left. It also explains why after a five hour run battery performance overnight was no better.

[Ricco1]

How are you measuring the state of charge? If with just a voltmeter, are you doing so after resting the batteries for at least an hour with no load on them?

 

What is the voltage whilst the engine is running, towards the end of say 2 hrs charging.

 

If you keep the batteries between 40 and 60% state of charge for a long time they will die quickly due to sulphation.

 

With a cheap multimeter. I know the meter will give a false reading until the batteries have 'settled'. After leaving them for a couple of hours I get around 12.3 volts. In the morning they are around 12.1 volts, or slightly less.

 

I also now have a volt meter that I plug into a 12 volt socket. As I look now, the engine has been running for an hour and three quarters, it shows 13.5 volts. That's without any load, it's lower if I watch t.v. or something. It went up fairly quickly when I first ran the engine but has been stuck on 13.5 volts for half an hour now.

I suspect your power usage is under-estimated. Further your two batteries (110 amp hour each?) have probably lost a fair amount of their capacity. This leads to the engine alternator (even a 40 amp one) quickly re-charging what capacity is left. It also explains why after a five hour run battery performance overnight was no better.

 

t.v. an hour a day= 17 watts

Lights say 2 (max) 4 hours a day= 64 watts

 

So around 7 amps there.

 

I charge my netbook for around 3 hours each day. Phone once a week. I don't know how much pumps use, or the radio, so I've guestimated 20 amps per day. Is that too low?

 

One of my leisure batteries is new, the boat only had 1 on it when I bought it. I've wired it to the existing battery with leads. Are they both now knackered perhaps, is there any way of checking?

[blodger]

Watch the charging voltage from start of engine running to when it stabilises and/or you switch off.

 

It should gradually rise to over 14v. If it does not I would suspect the alternator charge voltage is too low providing charging is lengthy enough and the batts are not totally goosed.

[nicknorman]

With these things one needs all the information - if something is missing its easy to jump to a wrong conclusion, and that's why it can be hard to diagnose by "remote control"

 

But let's make a supposition and then test it:

 

If the alternator is producing 13.5v at the 12 or 15 amps you mentioned, that is bad! There are a few possibilities and explanations:

 

1) there is a bad connection somewhere between the alternator and the batteries that is causing voltage to be lost. To check this, with the engine running measure the voltage firstly at the batteries between the + and - posts (not for example between the + and some other source of -ve connection), and then at the alternator between the alternator case and the B+ terminal (the one with the thicker wire on it). I am presuming that you alternator is not "floating" - if it is there will also be a thick -ve wire so use that terminal instead of the case. The 2 voltages you measure (battery and alternator) should be virtually the same, within 0.1v or so. If there is a big difference, this is likely to be the source of the problem and needs to be fixed (bad connections, bad battery isolator etc) by working through the wiring between alternator and battery until you get to the point where the voltage drops.

 

If the voltages are pretty much the same, go on to 2)

 

2) the alternator is a very old style one that only designed to produces 13.5v. The only solution here is to replace the alternator, since you will never really fully recharge the batteries at that voltage and sulphation will be inevitable. It may be possible just to replace the regulator but that maybe beyond your DIY confidence level. A photo of the alternator will help those more knowledgable than me to indentify it.

 

3) the alternator is defective. If there are no bad connections and it can only put out 15A, it could be that a diode has blown resulting in much reduced output. Again, its possible to replace the rectifier / regulator but a new or reconditioned alternator is a better answer under the circumstances.

 

Finally, assuming you didn't find a significant fault in 1) above, I would suggest that replacing the alternator with a 70A one would be money well spent (not that much money, they are sub £100 I believe). Your batteries will by now be knackered, don't buy any new ones until you can get the charging sorted out otherwise they too will die quickly.

 

Finally finally, as someone once said "measure twice, cut once" - ie it might be worth you comparing your voltmeter reading with a mate's meter just to check that your meter is reading correctly.

Edited October 11, 2013 by nicknorman

[by'eck]

 

With a cheap multimeter. I know the meter will give a false reading until the batteries have 'settled'. After leaving them for a couple of hours I get around 12.3 volts. In the morning they are around 12.1 volts, or slightly less.

 

I also now have a volt meter that I plug into a 12 volt socket. As I look now, the engine has been running for an hour and three quarters, it shows 13.5 volts. That's without any load, it's lower if I watch t.v. or something. It went up fairly quickly when I first ran the engine but has been stuck on 13.5 volts for half an hour now.

 

t.v. an hour a day= 17 watts

Lights say 2 (max) 4 hours a day= 64 watts

 

So around 7 amps there.

 

I charge my netbook for around 3 hours each day. Phone once a week. I don't know how much pumps use, or the radio, so I've guestimated 20 amps per day. Is that too low?

 

One of my leisure batteries is new, the boat only had 1 on it when I bought it. I've wired it to the existing battery with leads. Are they both now knackered perhaps, is there any way of checking?

 

Well you could fully charge them such that standing voltage (after one hour) with no load is over 12.7 volts. Then use a known single constant load, say 5 amps to discharge them over 24 hours. If the standing voltage after that time is around 11.8 volts they will be technically be flat and have released 120 amp hours of capacity.

 

If the standing voltage is well below 11.8 volts from the two connected batteries sling them. If above you can calculate their capacity using this voltage/SOC table allowing for the 120 amp hours already taken out.

 

BTW if the older of the two batteries is faulty it may be taking charge from the other. Its best to replace batteries as a matched set.

Edited October 11, 2013 by by'eck

[nicknorman]

Oh I forgot to say, are you running the engine fast enough? Measure the voltage whilst increasing the revs from your normal charging rpm - it shouldn't change. If it does increase, you need to run the engine faster or get a better pulley ratio. Also the obvious one - check for belt slipping ie dusty or oily belt, belt sloppy etc.

Edited October 11, 2013 by nicknorman

[Ricco1]

Thanks for all the replies. Over the course of the coming weeks I'm going to carry out the suggestions made so far.

 

The volt reading has now been pretty steady at 13.5 for the best part of an hour.

 

Until I get the money together to fix whatever needs fixing: it seems that the alternator gets my batteries up to their 'current maximum' of around 60% fairly quickly. So, running the engine for 2 hours in one go is a waste. I'm thinking of now running the engine until I hit 13.5 volts, then doing that again more regularly throughout the day. Would you agree that's a better option for now?

[Sir Nibble]

13.5 is way too low, ideally you want another volt on top of that. This is actually beginning to sound like another case of a failed output diode. Check the voltage on the alternator output terminal and the warning light terminal with engine running and compare. If there is any appreciable difference (more than say quarter of a volt) then that's your problem.

[nicknorman]

Well to be honest I think "over the coming weeks" is too slow! The longer you mis-charge the batteries the less likely they are to be salvageable. At least find out what the problem is ASAP, even if you can't afford to fix it. But if its a bad connection (my 1) above) it may be free to fix. "Over the coming weeks" translates into "its all too confusing and difficult, maybe if I do nothing it will go away". Sorry, one has to be cruel to be kind!

 

Sir nib may tell us how much a new rectifier/regulator would cost but it will be less than £50 I suspect, much much less than a new set of batteries.

 

Go on, bite the bullet!

[Ricco1]

Right! I'm going to have a go now, brave the gale force north easterlies here. I'll report back!

[Ricco1]

Progress, I think! First the belt from the engine to the alternator is loose and there's no more adjustment. Saying that it's not slipping at the moment so not causing the problem, I'll add a new belt to the 'to do' list.

 

I just turned the engine on and had a reading of 13.25 on the meter at the battery terminals. Struggled to find the alternator connections but there's a cylindrical thing below and to the front of it. From this a thick red cable goes to the batteries, so I presume this must be right? Anyway, the reading here was 14.25, exactly 1 volt more than I'm getting at the battery. So does this mean that it's probably a loose connection? where should I check first?

[nicknorman]

Well that's good news because it means the alternator is OK, although 14.25 is a little on the low side, its definitely better than 13.25! Are you sure that is alternator you are looking at - from the description with the smaller cylinder below and in front of it, that sounds more like the starter motor! Sorry if I am talking down to you but the alternator has a pulley on the end, with the belt going around it, and it will have connections on the back.

 

Anyway, there will be a high resistance connection somewhere. That means it will be disspating power and getting warm / hot. All you can do is to trace the wires from the alternator, and possibly via the starter motor, to the battery area. It may or may not route via the battery isolator but if it does, this is a popular area to have problems. You might try cycling the battery isolator(s) off and on a few times WITH THE ENGINE STOPPED and that might clean the contacts temporarily.

 

Dont forget that it is both the +ve and -ve wiring that needs to be checked. To determine whether its +ve or -ve (or maybe both), with the engine running measure the voltage from the alternator + terminal to the battery +ve post, and also from the alternator chassis to the battery -ve post. In each case the voltage should be very low (virtually zero), but you will presumably find that one or other line is dropping the 1v, so you will find the 1v and then know whether its the +ve or -ve.

 

 

Assuming cycling the battery isolator(s) doesn't make any difference to the battery voltage when charging, leave it charging for 10 mins or so and then stop the engine (for safety) and feel along the wiring connections, switches/isolators etc all the way from alternator to battery posts to look for something warmer than it should be. Also from the battery -ve terminal to where it connects to the engine. This will be where the power is being lost. (The alternator itself will of course be warm or hot, you will need to just visually check the connections to it)

 

 

One last possibility, presuming you have one alternator, but two sets of batteries - one starter battery plus your two domestic batteries, how is the charging split between those two sets of batteries from the one alternator? Do you have a "1 - 2 - 1+2 - Off" type battery selector, or is it automatic? If its automatic, there is a chance that it uses diodes to split the charge. These diodes are a very bad idea as they inherently drop at least 0.7v. If this is the case, you will need to replace the diode splitter with a voltage sensitive relay or the like otherwise you will always be chronically under-charging the batteries.

Edited October 11, 2013 by nicknorman

[Ricco1]

Well that's good news because it means the alternator is OK, although 14.25 is a little on the low side, its definitely better than 13.25! Are you sure that is alternator you are looking at - from the description with the smaller cylinder below and in front of it, that sounds more like the starter motor! Sorry if I am talking down to you but the alternator has a pulley on the end, with the belt going around it, and it will have connections on the back.

 

Anyway, there will be a high resistance connection somewhere. That means it will be disspating power and getting warm / hot. All you can do is to trace the wires from the alternator, and possibly via the starter motor, to the battery area. It may or may not route via the battery isolator but if it does, this is a popular area to have problems. You might try cycling the battery isolator(s) off and on a few times WITH THE ENGINE STOPPED and that might clean the contacts temporarily.

 

Dont forget that it is both the +ve and -ve wiring that needs to be checked. To determine whether its +ve or -ve (or maybe both), with the engine running measure the voltage from the alternator + terminal to the battery +ve post, and also from the alternator chassis to the battery -ve post. In each case the voltage should be very low (virtually zero), but you will presumably find that one or other line is dropping the 1v, so you will find the 1v and then know whether its the +ve or -ve.

 

 

Assuming cycling the battery isolator(s) doesn't make any difference to the battery voltage when charging, leave it charging for 10 mins or so and then stop the engine (for safety) and feel along the wiring connections, switches/isolators etc all the way from alternator to battery posts to look for something warmer than it should be. Also from the battery -ve terminal to where it connects to the engine. This will be where the power is being lost. (The alternator itself will of course be warm or hot, you will need to just visually check the connections to it)

 

 

One last possibility, presuming you have one alternator, but two sets of batteries - one starter battery plus your two domestic batteries, how is the charging split between those two sets of batteries from the one alternator? Do you have a "1 - 2 - 1+2 - Off" type battery selector, or is it automatic? If its automatic, there is a chance that it uses diodes to split the charge. These diodes are a very bad idea as they inherently drop at least 0.7v. If this is the case, you will need to replace the diode splitter with a voltage sensitive relay or the like otherwise you will always be chronically under-charging the batteries.

 

My electrical knowledge extends as far as wiring a plug, so you're certainly not talking down to me!

 

It could well be the starter motor I referred to. The thick red wire from the battery isolater goes here. There are some (thinner) wires going to the alternator but I can't get at these, the connections are shrouded by the bit of the engine that holds the water. Can I reasonably assume that if I had a reading over 14 volts in that general area, it means that the alternator is producing this?

 

I'm trying to work out the next step from what you told me. +ve is positive, red wire, -ve is negative, black wire, right?

 

So it seems that I should run the engine, run my hands over all the wires and connections, feeling for heat, and that's my problem area, is that right? I've already checked all obvious connections, none are loose.

 

I don't know if this has any relevance but the starter battery is showing 12.95 with the engine off, fully charged I assume.

[nicknorman]

OK you're right, it doesn't really matter if you are measuring the voltage at the starter motor since its obviously before the fault. Before you start feeling for warm wires, I would try to determine whether its the +ve or -ve set of wires by measuring the voltage between the alternator (or starter) and the battery +ve post, and also from the alternator or engine chassis to the battery -ve post, with the engine running (careful of loose clothing and belts / pulleys!).

 

Also try cycling the battery isolators with the engine off as I mentioned before, then check the battery voltage again whilst charging.

 

There are lots of different ways of wiring up a boat with 1 alternator, but a popular way is to connect the alternator + to the starter + thick cable, from the starter + thick cable to the starter battery via an isolator. From before the engine isolator another connection, via some sort of split charge function (diode, relay etc) via the domestic isolator to the domestic +ve batteyr post. Typically the negatives of the batteries will be connected together and thence to the engine chassis.

 

There are other ways of doing it, including having the isolator in the -ve line.

 

Anyway, regarding your comment on the starter battery yes it will probably be fully charged because when you use it to start the engine, it normally takes very little out of the battery (unless the engine is hard to start) and so only takes a short while to recharge. 12.95 at this battery is an artificially high reading resulting from recent charge, but clearly its reasonably healthy. It would be interesting to know what the starter battery voltage is whilst the engine is running, ie the same as the domestic bank, or significantly more..

[Arthur Brown]

Progress, I think! First the belt from the engine to the alternator is loose and there's no more adjustment. Saying that it's not slipping at the moment so not causing the problem, I'll add a new belt to the 'to do' list.

 

I just turned the engine on and had a reading of 13.25 on the meter at the battery terminals. Struggled to find the alternator connections but there's a cylindrical thing below and to the front of it. From this a thick red cable goes to the batteries, so I presume this must be right? Anyway, the reading here was 14.25, exactly 1 volt more than I'm getting at the battery. So does this mean that it's probably a loose connection? where should I check first?

Progress is good. a replacement belt will be better (a 70a alternator would be better still -even fit two! 40 for the starter and 70 for the house battery).

 

Very importantly you need to find that lost volt it is the difference between where you are and where you want to be. Use a multimeter to test for volts between the alternator +ve and the battery +ve I'll guess it's there somewhere. When you find all or part of that volt across a component or a connection, clean bits, check bolt tightness polish all copper and use only copper (or NO) washers in the current path.

 

In my personal opinion a 40 amp alternator may not be sufficient to .keep you fully charged unless you can offer a long cruise weekly

 

It will put 40A into a totally flat battery but maybe only 15a into a half charged battery getting even less as the batteries approach full

[Ricco1]

I'm getting back on this this morning.

 

Just so I can try to understand the relationship between volts and soc of my batteries: When I run my engine voltage goes up fairly quickly, within 15/ 20 minutes, to around 13.5 volts. It then stays at 13.5 volts, regardless of how long I run the engine. Does that mean that after 20 minutes no more charge (amps) are going into my batteries?

 

Also I'm a bit confused with what voltage to expect. I found 14.25 volts at the alternator, 1 volt more than the reading at the battery. The advice given is that they should be almost exactly the same. Is that the case regardless of the soc of my batteries? If so this means there is no link between voltage (when the engine is running) and soc. Soc can only be measured by voltage when the engine is off and the batteries have rested. Voltage shown when the engine is running gives no indication whatsoever as to the soc of the batteries.

 

Are the last 3 statements correct, or have I got it wrong?

[nicknorman]

There isn't a specific relationship between voltage and SoC during charge because the voltage depends on the alternator, not the batteries. What will happen, when starting with batteries in a low state of charge, is that despite working flat out, the alternator is unable to get the voltage up to its regulated value (14.25 or whatever) - it is limiting on maximum current. This is called the bulk charging phase.

 

As the SoC improves, the current taken by the battery decreases and the alternator regulates at 14.25 (or whatever). During this phase, called the Absorption phase, the alternator voltage stays at its regulated voltage and the current gradually decreases. This phase is likely to last many hours because the battery takes less and less current as its SoC approaches 100%. Finally, once the current has fallen to say 1% of the amphour capacity, it is considered to be fully charged.

 

If you terminate the charge at the start of the absorption phase, the batteries will be only partially charged and if you repeat this over days or weeks, the batteries will rapidly lose capacity due to sulphation.

 

What is interesting in your case is the relationship between the alternator voltage and battery voltage. From your description it sounds as though there is a pretty much fixed voltage drop. However with a resistive load (bad connection) one would expect the voltage lost to be proportional to the charging current. This would result in the difference between the 2 voltages gradually decreasing during the absorption phase. However from your description this may not be happening - of maybe you just haven't left it long enough.

 

Anyway, if the voltage drop seems fixed regardless of charge current, this suggests that a diode splitter is fitted. This will intrinsically drop too much voltage and would need to be replaced with a voltage sensitive relay. However, we don't have enough hard information to definitely come to this conclusion.

 

Today, consider giving the engine a long run, 2 - 3 hrs at least, and measure, say every 15 mins, the alternator voltage, domestic battery voltage and starter battery voltage.

 

Eta your last 3 comments are pretty much correct. I would say there is no useful link between voltage with engine running, and SoC.

Edited October 12, 2013 by nicknorman

[blodger]

You cannot get a SOC indication by voltage when the batts are in use or charging or have recently been so.

 

After prolonged charging the voltage at the alternator should more or less equal the voltage at the batteries and effective charging may have ceased. However, getting the last 10% of charge in takes up to four times longer than the charging getting them to 90%.

 

The large difference in voltage at your batts compared with that at the alternator implies some problem of resistance on the route of the current to the batts such as bad connections or a dodgy isolator switch. Think about it, its the same piece of wire with different voltages at each end. However, a totally goosed battery will drag down the voltage at the receiving end.

 

You need a good 14v + voltage at the batts to get maximum charging at the batts to use running the engine efficiently which is where so called 'battery boilers' come in to obviate 1/2 volt drops in voltage which come in if you are using a diode to separate engine and domestics as opposed to relay split charging.

 

Hope that helps. It is not as simple as yes or No to some questions

[Ricco1]

Thanks for the replies. There may be some progress:

 

I ran the engine this morning and once again there was a difference of 1 volt between the alternator and the leisure batteries. On the panel that the isolators are fixed to there is a cube shaped affair. This has 2 thickish positive wires going into it, plus a thinner brown and black one. The readings at the red wires are .1 volt less than the alternator but .9 volt more than the batteries. I wouldn't say these connections are hot, but they are certainly a little warm to the touch.

 

Have I found the problem do you think, what to do next?

[by'eck]

Not sure if the cube shaped affair is a connection point, isolator, fuse or shunt. A photo would help. See if you can trace a direct connection from this device to battery positive to ensure there are no other connections to be checked.

 

In any case wherever there is heat of this nature, there is a bad connection. Disconnect batteries first then undo, clean with abrasive and re-assemble connections to this device. Ensure that crimping of terminals onto the thick battery cables appears good with no corrosion within the terminals which otherwise require replacement.

 

After doing this run engine and check voltages again.

[blodger]

Thanks for the replies. There may be some progress:

 

I ran the engine this morning and once again there was a difference of 1 volt between the alternator and the leisure batteries. On the panel that the isolators are fixed to there is a cube shaped affair. This has 2 thickish positive wires going into it, plus a thinner brown and black one. The readings at the red wires are .1 volt less than the alternator but .9 volt more than the batteries. I wouldn't say these connections are hot, but they are certainly a little warm to the touch.

 

Have I found the problem do you think, what to do next?

 

It may be a significant contributory factor. I also suspect one of your batterries/charging regime.

 

The box with wires is in all probability your split charge relay with the two thin wires being what actuates it when the ignition is on and the alternator is running. The two thick positives will be a live from/to the alternator to the starter battery and live to the domestics. Relays should not drop 0.8v so if cleaning terminals and retightening does not work it may be a case of replacing.

 

If you have a means to jump the two lives thus cutting out the relay you should see the higher voltage at the batts proving the need to replace; Perhaps the contacts internally are burning out/corroded.

In all probability it is your split charge relay with the thinner wires being what actuates it from the ignition being on and the alternator running respectively. The lives will effectively be one from the starter battery & alternator and one from the domestics if your starter battery is getting alternator voltage.

Relays should not drop 0.8v so if cleaning terminals, refitting and tightening does not improve things it is replacement time.

The contacts are possible burning out/corroded. Small Lucas relays are notoriously short lived.

If you have the means to jump the two big terminals at the relay or remove and bolt together you should see the higher voltage at the domestics. Be aware that in doing so you are joining (parallelling) the domestics with the starter battery.

 

ETA Two posts here as first disappeared; Slightly different content so leaving alone.

CWDF seems very slow today

Edited October 12, 2013 by blodger

[ditchcrawler]

Is there a split charge diode by any chance

[blodger]

Is there a split charge diode by any chance

 

A diode would be bigger than most relays with fins for cooling and no need for the two thinner wires.

 

My guess is that due to the small 40a alternator this is an inadequate type car relay or a lucas more suited to heater plugs than split charging.