Flat bank of batteries

[marmaduke]

I’ve just had 3 new leisure batteries, all 110ah, installed. I have also just installed a 1500w inverter, connected to one of the battery’s terminals. I have used this for running some computer speakers at relatively high volume, and run my laptop from it to watch a film or two. I had left the inverter on overnight, and came back to a flat bank of batteries.

 

I hadn’t run the engine much, but was under the assumption that the power I was using was quite minimal. This appears not to be the case.

 

I charged the batteries for a good 5 hours on the weekend, thinking that this would get them all back up to at least 80%. However, I bought a voltmeter yesterday and checked the batteries last night to see what they actually hold and it was a rather depressing 11.69v.

 

I then ran the engine for an hour. I checked the voltage coming from my alternator, which was at 13.56v. From reading these forums, 14.4v is the preferred voltage from the alternator in order to charge the batteries. After an hour of running the engine, I then tested the voltage on the batteries. They had gone up to 12.20v. After a couple of hours I checked again and they stabilised at 11.83v. I checked again this morning, and they were still at 11.83v. All these readings were the same across all the batteries, and when tested separately.

 

The questions I have are as follows:

 

- Is my alternator in a bad way if it’s only kicking out 13.56v? Or is it common for them not to reach 14.4v?

- Why do my batteries charge to a level, then stabilise at a lower level?

- Should the inverter be connected to the positive and negative of just one battery, or the positive of one battery, and the negative of the other? Is this a problem at all?

- Do you have any other advice based on the situation described above?

 

Your help is much appreciated,

 

Marmaduke

Edited February 8, 2011 by marmaduke

[Kiwipeter]

see the Smartgauge site - http://www.smartgauge.co.uk/batt_con.html

 

Peter

 

 

I’ve just had 3 new leisure batteries, all 110ah, installed. I have also just installed a 1500w inverter, connected to one of the battery’s terminals. I have used this for running some computer speakers at relatively high volume, and run my laptop from it to watch a film or two. I had left the inverter on overnight, and came back to a flat bank of batteries.

 

I hadn’t run the engine much, but was under the assumption that the power I was using was quite minimal. This appears not to be the case.

 

I charged the batteries for a good 5 hours on the weekend, thinking that this would get them all back up to at least 80%. However, I bought a voltmeter yesterday and checked the batteries last night to see what they actually hold and it was a rather depressing 11.69v.

 

I then ran the engine for an hour. I checked the voltage coming from my alternator, which was at 13.56v. From reading these forums, 14.4v is the preferred voltage from the alternator in order to charge the batteries. After an hour of running the engine, I then tested the voltage on the batteries. They had gone up to 12.20v. After a couple of hours I checked again and they stabilised at 11.83v. I checked again this morning, and they were still at 11.83v. All these readings were the same across all the batteries, and when tested separately.

 

The questions I have are as follows:

 

- Is my alternator in a bad way if it’s only kicking out 13.56v? Or is it common for them not to reach 14.4v?

- Why do my batteries charge to a level, then stabilise at a lower level?

- Should the inverter be connected to the positive and negative of just one battery, or the positive of one battery, and the negative of the other? Is this a problem at all?

- Do you have any other advice based on the situation described above?

 

Your help is much appreciated,

 

Marmaduke

[FORTUNATA]

Sometimes there's a voltage drop in cases where diode isolators are fitted. This happens when the alternator voltage is still higher than the battery terminal voltage. Or voltage drop can take place due to some other problem. Check the wiring between the alternator B+ output to the batteries. Check all terminals are clean, wires not excessively long or even knotted up somehow. Voltage drop is where the alternator voltage lowers in transit as it passes to the batteries.

To be sure it helps to test alternator output with a multimeter and then again at the battery but this can be tricky unless you know how to do it. It does seem in this case there's a voltage drop or the batteries are in need of attention. You may even need the charging system rewired and a relay system installed (something more efficient).

By the way, running an engine on idle as a battery charger isn't so good for the engine. You can help matters by running it in gear so it pulls a bit on the ropes while charging and turn everything else off on the boat. This will stop any cylinder glazing which is what happens when engines are run purely as battery chargers at a mooring.

 

 

Ive just had 3 new leisure batteries, all 110ah, installed. I have also just installed a 1500w inverter, connected to one of the batterys terminals. I have used this for running some computer speakers at relatively high volume, and run my laptop from it to watch a film or two. I had left the inverter on overnight, and came back to a flat bank of batteries.

 

I hadnt run the engine much, but was under the assumption that the power I was using was quite minimal. This appears not to be the case.

 

I charged the batteries for a good 5 hours on the weekend, thinking that this would get them all back up to at least 80%. However, I bought a voltmeter yesterday and checked the batteries last night to see what they actually hold and it was a rather depressing 11.69v.

 

I then ran the engine for an hour. I checked the voltage coming from my alternator, which was at 13.56v. From reading these forums, 14.4v is the preferred voltage from the alternator in order to charge the batteries. After an hour of running the engine, I then tested the voltage on the batteries. They had gone up to 12.20v. After a couple of hours I checked again and they stabilised at 11.83v. I checked again this morning, and they were still at 11.83v. All these readings were the same across all the batteries, and when tested separately.

 

The questions I have are as follows:

 

- Is my alternator in a bad way if its only kicking out 13.56v? Or is it common for them not to reach 14.4v?

- Why do my batteries charge to a level, then stabilise at a lower level?

- Should the inverter be connected to the positive and negative of just one battery, or the positive of one battery, and the negative of the other? Is this a problem at all?

- Do you have any other advice based on the situation described above?

 

Your help is much appreciated,

 

Marmaduke

Edited February 8, 2011 by FORTUNATA

[mayalld]

 

By the way, running an engine on idle as a battery charger isn't so good for the engine. You can help matters by running it in gear so it pulls a bit on the ropes while charging and turn everything else off on the boat. This will stop any cylinder glazing which is what happens when engines are run purely as battery chargers at a mooring.

 

 

 

 

Unfortunately, doing that is a breach of your licence conditions, and causing damage to the canal.

[marmaduke]

see the Smartgauge site - http://www.smartgauge.co.uk/batt_con.html

 

Peter

 

Thanks Peter, that's bloody handy. Much appreciated

[jelunga]

Whilst waiting for Gibbo's comments, mine would be thus.

 

The charging voltage will not be 14.3 v until the battery reaches a high state of charge. Therefore, assuming the alternator is not faulty, it indicates really discharged batteries.

My experience of invertors is that they suck the life blood out of batteries at around the same rate as HMRC suck money out of my pockets!

 

Assuming your 110 ah batts are connected to give 12v, they have a theoretical capacity of 3 x 110 = 330 ah. If you load through the inverter is say 800 watts at 230v this will give a discharge current of around 75 amps at 12v, allowing for inverter losses. Therefore, at such a high discharge rate, I guess that after about 3 hrs use, your battery bank will have almost been bled dry.

 

My conclusion is not a large enough bank for the loads you have applied to it.

 

But others with more knowledge might be along soon.

 

K

[Keeping Up]

I've just had 3 new leisure batteries, all 110ah, installed. I have also just installed a 1500w inverter, connected to one of the battery's terminals. I have used this for running some computer speakers at relatively high volume, and run my laptop from it to watch a film or two. I had left the inverter on overnight, and came back to a flat bank of batteries.

 

I hadn't run the engine much, but was under the assumption that the power I was using was quite minimal. This appears not to be the case.

 

I charged the batteries for a good 5 hours on the weekend, thinking that this would get them all back up to at least 80%. However, I bought a voltmeter yesterday and checked the batteries last night to see what they actually hold and it was a rather depressing 11.69v.

 

I then ran the engine for an hour. I checked the voltage coming from my alternator, which was at 13.56v. From reading these forums, 14.4v is the preferred voltage from the alternator in order to charge the batteries. After an hour of running the engine, I then tested the voltage on the batteries. They had gone up to 12.20v. After a couple of hours I checked again and they stabilised at 11.83v. I checked again this morning, and they were still at 11.83v. All these readings were the same across all the batteries, and when tested separately.

 

The questions I have are as follows:

 

- Is my alternator in a bad way if it's only kicking out 13.56v? Or is it common for them not to reach 14.4v?

- Why do my batteries charge to a level, then stabilise at a lower level?

- Should the inverter be connected to the positive and negative of just one battery, or the positive of one battery, and the negative of the other? Is this a problem at all?

- Do you have any other advice based on the situation described above?

 

Your help is much appreciated,

 

Marmaduke

 

I assume your readings of 12.20 and 11.83 were both taken at the batteries with the engine switched off? But presumably the first one was taken soon after switching it off? If so, some of the charge had not yet soaked into the battery but was lying on the surface of the plates (which is why it's called "surface charge"). Leaving it for a while allowed it to soak in and thus stabilise.

 

If the batteries had only risen to 12.20 when charging, they were still flat. It takes many hours to fully recharge a flat bank. If they were charging properly for 5 hours, they shouldn't be all that flat although they'd still be nowhere near full. It does of course also depend what power you were taking from them between when you finished charging and when you measured them. Inverters don't take a huge amount of power when they have no load, it is typically between 1.0 and 1.5 amps for a sine-wave model.

 

 

As Jelunga says, the alternator output voltage is held down to the battery voltage, so if they are still flat then the alternator will be showing a low voltage, and will not reach its regulated voltage (be it 13.8 or 14.4) until the batteries are much nearer to full charge. If it never got above 13.56 that would indicate a fault.

 

With a 330 Ah bank you have an effective usable capacity of 165 Ah, and you would have much less than this if you took a high load. In Jelunga's example of an 800 watt load you would effectively flatten them in less than an hour and a half.

[marmaduke]

Thanks Jelunga and Allan. Looks like I'm going to have to put a fair few hours of charging into them in the coming days...whilst taking readings of course. And readjust the connection of the inverter so the load is balanced across the batteries.

[blodger]

Do you know what alternator you have?

 

Some you can easily up the charge voltage and current by adding diodes appropriately as on the

SG site or, consider investing in a 'battery boiler' alt controller to reduce the duration of

the first stage of charging

 

As someone has pointed out idle revs often do not charge much so invest in a clamp on ammeter,

about 20.00 on EBay, so you can see what you are or are not achieving and, the effect of rpm

upping.

[Tony Brooks]

Do you know what alternator you have?

 

Some you can easily up the charge voltage and current by adding diodes appropriately as on the

SG site or, consider investing in a 'battery boiler' alt controller to reduce the duration of

the first stage of charging

 

As someone has pointed out idle revs often do not charge much so invest in a clamp on ammeter,

about 20.00 on EBay, so you can see what you are or are not achieving and, the effect of rpm

upping.

 

 

Please - not again. Can we all get it into our heads that during the first phase of charging (bulk) it is the alternator that is limiting the charging volatge and thus the charging currant to protect itself from burning out. ANY form of advanced controller will just sit there twiddling its thumbs until the alternators volatge regulator starts to control the voltage. Only then in the second phase of charging (acceptance) is it possible to for the controller to mess with the alternator and increase the charging voltage.

 

Even then if it really is a "battery boiler" that induces gassing any apparent increase in charging currant may be illusory as far as any increase in actual charging is concerned.

 

As far as the question is concerned I would not like to infer much from those readings apart from flat batteries. As my first paragraph states heavy charging currants depress the charging volatge so any charging volatge (like the expected 14.2 to 14.4) should only be taken with well charged batteries. Lucas used to say with 10 amps or less flowing".

 

So far I am unable to distinguish between a low voltage due to high charging currant (normal) or low volatge due to a failed diode (fault). Only getting the bank fully charged and then measure the charging volatge will sort it out.

 

As the OP seems to have connected the inverter in a "not recommended way" we must also be suspicious about voltdrop on the charging circuit (Pos & Neg side). Certainly if a split charge diode is in use but other charge splitters can develop a high resistance as can terminals and connection.

 

Sorry to comer on a bit strong in the first paragraph.

[blodger]

Please - not again. Can we all get it into our heads that during the first phase of charging (bulk) it is the alternator that is limiting the charging volatge and thus the charging currant to protect itself from burning out. ANY form of advanced controller will just sit there twiddling its thumbs until the alternators volatge regulator starts to control the voltage. Only then in the second phase of charging (acceptance) is it possible to for the controller to mess with the alternator and increase the charging voltage.

 

Even then if it really is a "battery boiler" that induces gassing any apparent increase in charging currant may be illusory as far as any increase in actual charging is concerned.

 

As far as the question is concerned I would not like to infer much from those readings apart from flat batteries. As my first paragraph states heavy charging currants depress the charging volatge so any charging volatge (like the expected 14.2 to 14.4) should only be taken with well charged batteries. Lucas used to say with 10 amps or less flowing".

 

So far I am unable to distinguish between a low voltage due to high charging currant (normal) or low volatge due to a failed diode (fault). Only getting the bank fully charged and then measure the charging volatge will sort it out.

 

As the OP seems to have connected the inverter in a "not recommended way" we must also be suspicious about voltdrop on the charging circuit (Pos & Neg side). Certainly if a split charge diode is in use but other charge splitters can develop a high resistance as can terminals and connection.

 

Sorry to comer on a bit strong in the first paragraph.

No thanks Tony, I would have been better not to have mentioned stages and stuck to 'reduce overall charging time'.

 

I agree it is difficult to diagnose much from the info available but does not sound like an alt putting out 70a into flat batteries, etc etc

[smileypete]

The questions I have are as follows:

 

- Is my alternator in a bad way if it’s only kicking out 13.56v? Or is it common for them not to reach 14.4v?

Depends on the charge current.

 

If the charge current is high (say above about 20A) it just means the batteries are being charged.

 

If the charge current is lower it could be one or more of:

 

Loose drive belt.

Regulator voltage too low.

Defective alternator brushes/regulator.

Alternator 'under pulleyed' ie spinning too slow.

 

The rest of your problems could be caused by one or more of:

 

Undersized wiring.

Poor connections.

Insufficient charging time.

Defective split charge diode/relay.

Defective battery isolator.

Poor/defective/abused batteries.

 

A big help in preventing and diagnosing problems is to have a decent accurate panel mounting voltmeter, and a reasonable panel mounting shunt ammeter, and knowing how to interpret them as far as battery charging and discharging goes.

 

cheers,

Pete.

Edited February 8, 2011 by smileypete

[Tony Brooks]

No thanks Tony, I would have been better not to have mentioned stages and stuck to 'reduce overall charging time'.

 

snip

 

 

 

Even that is open to question if the voltage goes high enough to start them gassing. An ammeter may make it look as if they are taking a higher charge but in reality the extra current may just be used to heat the batteries and electrolyse the water, but I leave it to Gibbo to argue that one.

 

If fitting such a device to a boat seems to make a significant difference to the charging with a modern alternator it is probably covering up a circuit fault.

[blodger]

Even that is open to question if the voltage goes high enough to start them gassing. An ammeter may make it look as if they are taking a higher charge but in reality the extra current may just be used to heat the batteries and electrolyse the water, but I leave it to Gibbo to argue that one.

 

If fitting such a device to a boat seems to make a significant difference to the charging with a modern alternator it is probably covering up a circuit fault.

 

I have A127 Alts with a stirling controller on one. It seems to me the controller ups the volts and amps from the start until it cuts out and leaves it to the alt reg. I am just changing one battery bank after 8 years but the batts I am replacing are still holding 12.7v (with diminished capacity else why renew) so will be used elsewhere.

 

In my experience 'battery boilers' are worthwhile.

 

There is a Peter Hopley used Acorn "Kestrel" contoller on EBay currently for 30.00

 

I use the Diode modification on a lawnmower generator to do equalisation charges, etc.

 

There is no one answer. The OP needs to look to his system and any remedy any defects first agreed before looking further

Edited February 8, 2011 by blodger

[marmaduke]

Ok, so last night I charged the batteries for a further two hours. Before charging, the voltage across all three was 11.83v, and after the two hour charge (after they settled) it read 11.97v.

 

This seems like such a paltry amount...is that normal? I would have thought 2 hours of charging would have made a more significant impact on them, surely?

 

I'll stick another two hours in them tonight and record the readings again.

 

Also, a couple of things to mention:

 

- I've used only some lights and the water pump during these charges, nothing else, the inverter is not on, so a minimal draw

 

- I don't know what the alternator make is, but I have a BMC 1.5, built in 1980 by Peter Nicholls...would anyone be able to make an educated guess from those details?

 

- The starter battery is always at 12.7v on every reading i've been taking

[Naughty Cal]

Your batteries are very flat though. 2 hours wont really touch them, plus as you say you are still using power on the boat in the mean time. Your batteries really need a good long charge otherwise you will kill them.

[marmaduke]

Your batteries are very flat though. 2 hours wont really touch them, plus as you say you are still using power on the boat in the mean time. Your batteries really need a good long charge otherwise you will kill them.

 

They've had about 9 hours in total now since they went flat...is that just not enough?

[Justme]

Was that 9 hours in one go? If so then possibly.

 

If it was 9 hours in small chunks whilst using lots of power at the same time then no.

 

Totally flat bats could take a day or 3 to be fully recharge if they ever will.

[Naughty Cal]

They've had about 9 hours in total now since they went flat...is that just not enough?

 

No, not in the 2 hour stints you have been giving them with you using power as well in between. They really need a good long charge in one go. Go out cruising for the day, that way you can charge them up and get out in the boat at the same time

 

Do you know anyone who is on shore power and has a battery charger that may be willing to charge them for you. If you keep abusing them and leaving them flat they will soon keel over and die

[Tony Brooks]

Ok, so last night I charged the batteries for a further two hours. Before charging, the voltage across all three was 11.83v, and after the two hour charge (after they settled) it read 11.97v.

 

This seems like such a paltry amount...is that normal? I would have thought 2 hours of charging would have made a more significant impact on them, surely?

 

I'll stick another two hours in them tonight and record the readings again.

 

Also, a couple of things to mention:

 

- I've used only some lights and the water pump during these charges, nothing else, the inverter is not on, so a minimal draw

 

- I don't know what the alternator make is, but I have a BMC 1.5, built in 1980 by Peter Nicholls...would anyone be able to make an educated guess from those details?

 

- The starter battery is always at 12.7v on every reading i've been taking

 

 

Does it have a big plastic cover over the end?

 

If so I bet its a Lucas ACR unit and some of them did not much better than a dynamo. I think 35 amps output was a big one. They also have the main earth connection between diode pack and case made by a single 4 or 5mm stud and nut. These can come loose and totally mess up the charging. I suspect many of them were only set to charge at between 13.8 & 14.2 volts (with a well charged battery).

 

We need voltages measured across the battery whilst they are on charge otherwise we have no way of guessing the state of the alternator. We also need ammeter readings but for that you need (as you have been told) a clip on ammeter of some sort.

[marmaduke]

Ok, I'll go for a good long cruise this weekend then.

 

For the future though...would members of this forum recommend me buying a generator, and using that to charge the batteries, rather than using the engine of the boat (in neutral) all the time? Would it be a more efficient charge, and perhaps quicker?

 

A generator I would imagine, could be useful regardless of charging.

 

If yes, any recommendations?

[blodger]

Ok, I'll go for a good long cruise this weekend then.

 

For the future though...would members of this forum recommend me buying a generator, and using that to charge the batteries, rather than using the engine of the boat (in neutral) all the time? Would it be a more efficient charge, and perhaps quicker?

 

A generator I would imagine, could be useful regardless of charging.

 

If yes, any recommendations?

 

If the alt is the older and low charging ACR type (as Tony anticipates) I would replace with a

70amp A127 (or clone) before buying a genny. However, you may need a genny to get you back if

you stop this weekend! A batt voltage of below 12v after two hours charging sounds like

something in SmileyPetes list and/or the alt needs addressing.

 

If you want a genny for emergencies get the cheapest. If you intend regular use go for an

expensive quiet suitcase jobbie.

 

Godd luck and do advise how you get on

[Justme]

 

1, would members of this forum recommend me buying a generator, 1a, and using that to charge the batteries,

 

2, Would it be a more efficient charge,

 

3, and perhaps quicker?

 

 

 

1 & 1a, Yes.

 

2, most probably apart from the days you plan to use the engine for other things at the same time like moving & hot water.

 

3, almost certainly no. Charge time is a result of depth of discharge & battery chemistry / type. Charger size plays a much smaller part than most realise.

[Dorman]

I’ve just had 3 new leisure batteries, all 110ah, installed. I have also just installed a 1500w inverter, connected to one of the battery’s terminals. I have used this for running some computer speakers at relatively high volume, and run my laptop from it to watch a film or two. I had left the inverter on overnight, and came back to a flat bank of batteries.

 

I hadn’t run the engine much, but was under the assumption that the power I was using was quite minimal. This appears not to be the case.

 

I charged the batteries for a good 5 hours on the weekend, thinking that this would get them all back up to at least 80%. However, I bought a voltmeter yesterday and checked the batteries last night to see what they actually hold and it was a rather depressing 11.69v.

 

I then ran the engine for an hour. I checked the voltage coming from my alternator, which was at 13.56v. From reading these forums, 14.4v is the preferred voltage from the alternator in order to charge the batteries. After an hour of running the engine, I then tested the voltage on the batteries. They had gone up to 12.20v. After a couple of hours I checked again and they stabilised at 11.83v. I checked again this morning, and they were still at 11.83v. All these readings were the same across all the batteries, and when tested separately.

 

The questions I have are as follows:

 

- Is my alternator in a bad way if it’s only kicking out 13.56v? Or is it common for them not to reach 14.4v?

- Why do my batteries charge to a level, then stabilise at a lower level?

- Should the inverter be connected to the positive and negative of just one battery, or the positive of one battery, and the negative of the other? Is this a problem at all?

- Do you have any other advice based on the situation described above?

 

Your help is much appreciated,

 

Marmaduke

 

Just a thought and l speak from experience--check each battery individually l did this at a Battery centre, l had the same problems and found one battery had a bad +ve post which was partially detached from the cells and only showed up when the meter was pressed hard on it. This caused the alternator to suffer and not charge properly to the others linked to the dudun.

Sorry if this has been mentioned but believe me was the last thing l checked after alternator overhaul!!

 

Simon

[FORTUNATA]

Maybe we're moving closer to battery sensing and its significance. Systems whereby the regulator senses battery terminal voltage for better charging. What I do recall is diode isolators bring about a tiny voltage drop so must not be used with machine sensing.

Incidentally I once tested some batteries that appeared to be pancake flat but later found the terminals were caked over and needed sanding clean. Too much resistance gave wonky voltage readings. I cleaned them up, charged them and got a decent reading of close to 13 volts.

 

Even that is open to question if the voltage goes high enough to start them gassing. An ammeter may make it look as if they are taking a higher charge but in reality the extra current may just be used to heat the batteries and electrolyse the water, but I leave it to Gibbo to argue that one.

 

If fitting such a device to a boat seems to make a significant difference to the charging with a modern alternator it is probably covering up a circuit fault.