How to improve engine charging?

[chrisbitz]

I'd like to improve the alternator charging my batteries..

at first, in the morning after a high drain, it starts off at say, 20 Amps, but then as the battery gains charge, the amps goes down.

Is there a way of keeping the amps higher or something?

I've seen the Stirling battery charger thingy, but it's £350!, and although it's a wonderful device, that's too much for me to afford.
Is there anything nearer £100 that I could use to improve charging??

 

[jdc]

I'd like to improve the alternator charging my batteries..

at first, in the morning after a high drain, it starts off at say, 20 Amps, but then as the battery gains charge, the amps goes down.

Is there a way of keeping the amps higher or something?

I've seen the Stirling battery charger thingy, but it's £350!, and although it's a wonderful device, that's too much for me to afford.
Is there anything nearer £100 that I could use to improve charging??

There is a limit to what can be done, and to know whether your 20A is normal or can be bettered one would have to know the battery size and percent charge you start from, but I have had excellent experience with the Adverc battery controller http://www.adverc.co.uk/products/1 on several boats.

Unhelpfully their prices are shown as 'POA' but I don't think they are £350.

 

[pvb]

If you only have one battery, you probably won't get much more charge in to it. If you have a battery bank, a "smart" regulator (Adverc, Sterling, etc) will help to maximise the charge rate. Bigger capacity banks accept bigger charge currents. If you only want to spend £100, your best investment might well be to add another battery in parallel.

 

[chrisbitz]

I have 2x105AH house batteries, and a 75ah starter battery.

 

[halcyon]

I'd like to improve the alternator charging my batteries..

at first, in the morning after a high drain, it starts off at say, 20 Amps, but then as the battery gains charge, the amps goes down.

Is there a way of keeping the amps higher or something?

The regulator on the alternator reduces amps to control / limit the output voltage.

So the first thing is what is the maximum voltage ? if only 13.6 volt, changing / fitting smart reg will increase regulation voltage, thus increasing the amount of time you see the higher output amperage.
You cannot increase alternator output current, that is limited by alternator construction, you can help by minimizing volt drops in the charging system, blocking diodes, bad connections.

First find out what your problem is, it may just cost nothing to put right, if not what the most cost effective answer is.

Brian

 

[chrisbitz]

The regulator on the alternator reduces amps to control / limit the output voltage.

So the first thing is what is the maximum voltage ?

Brian

Thanks for the reply, I think the voltage is around 14 - 14.4 ish?

 

[William_H]

To answer (or try to you) question we need to confirm that the alternator is charging all 3 batteries in parallel with no diodes in the circuit. (diodes will reduce the voltage to the battery by .7 volt and so reduce current going in to batteries. Ok if you have no restrictions ie you have a voltage sensing relay or manually switch all batteries in parallel and if you are charging at 14-14.4 volts (ish) then probably not much more can be done.
The current into a battery (that it will accept) is much dependant on the voltage and .1 volt can equate to some amps difference. That ofcourse assuming the alternator is happy to supply.
There are some tricks to get the regulator to regulate at a higher voltage. Unfortnately this can mean that on a long engine run you could overcharge (cook) the batteries.
hence a smart regulator Adverc Sterling etc are smart enough to increase the voltage on start up but reduce the voltage to float once batteries are charged.
I would suggest that you double check voltage at the battery on charge. If it is over 14v then you accept that is your best arrangement. If the voltage at the battery is less and the voltagee at the output terminal of the alternator is much greater then you need to track down where the voltage is being lost. It may be lost in wiring resistance or switch contacts or as said diodes.
The previously mentioned tricks to raise regulator voltage, (apart from buying a new regulator) involve disconnecting the negative earth of the regulator and insulating it from earth then fit a silicon diode from the reg negative to earth. ( cathode or band end to earth) This will raise the regulator .7 volt above earth so raising the regulated voltage by .7 volt. You can fit a switch to bypass the didoe so reducing voltage to normal for long runs. But you could damage the batteries if you forget. good luck olewill

 

[charles_reed]

What makes you think your batteries aren't being fully charged?
The 14.4 volts and 20 amp output look pretty good and it's far less pocket-draining to have slightly less fully charged batteries than to attempt to overcharge them.
Not knowing the type, construction of batteries or detail of wiring, leaves some large areas of mystery.
I'd suggest leaving well alone.

 

[halcyon]

Thanks for the reply, I think the voltage is around 14 - 14.4 ish?

In that case, check first what the voltage is on the battery terminal, not on connector as you charge.

If you leave the boat with no charging on, wind, solar, mains, check battery voltage on arrival before switching on the batteries, this will give you a rested voltage and a good guide to battery level.

Secondly, by checking the voltage each time you visit, if the voltage is similar each time, you have no battery problems, if over time the voltage is dropping slowly, you are under charging and have a problem.

Brian

 

[Marsupial]

What makes you think your batteries aren't being fully charged?
The 14.4 volts and 20 amp output look pretty good and it's far less pocket-draining to have slightly less fully charged batteries than to attempt to overcharge them.
Not knowing the type, construction of batteries or detail of wiring, leaves some large areas of mystery.
I'd suggest leaving well alone.

I would have to agree with Charles, you are entering the world of diminishing returns, lots of cash outlay for very little return.

You have to accept that the lead acid cell will accept a charge at a certain rate, you can throw more volts and amps at it but it will just get hot. So changing the regulator may - not WILL - accelerate the charging rate. In other words you may find that there is no tangible benefit to be gained from messing about with the alternator regulator.

You also have to accept that even with fast charging devices your batteries wont get much above 85% charged in a day, see the link below, these guys know more about batteries than there is to know, they work on a maximum of 90% charge capacity because there are not enough hours in a day to get beyond that. Attach to shore power for a week then you may see a 100% charge.

http://msor.victoria.ac.nz/foswiki/pub/Main/ResearchReportSeries/mscs03-08.pdf


Voltage drops from various technologies have been identified and overcome but you MAY find a very small advantage if you fit a battery combiner in place of a non sensed splitter diode - select which one with care they are not all equal. That will cost you about £40.00

With a budget of £100 I would buy a tin of contact cleaner and turn my attention to the consumption side, change all the filament lights for cheap LEDS - the ones I buy cost about 50p each and they work a treat. Then enjoy a cold beer.

 

[chrisbitz]

Thanks for all the detailed replies guys!
It's beginning to slowly dawn on me that there may be a problem with the wiring...

I have a NASA Battery monitor, and I told it I have 210 AH of capacity (2x105AH batteries in parallel) and off it went. Meanwhile, whatever I've done, I've never seen more than about 90 AH of capacity shown.

The batteries are linked in parallel, ie showing 12v, not 24v! but maybe there's something else wrong?

I think battery monitors work out the capacity on the voltage of the battery, so if there's two batteries, does the voltage automatically stabilise between them?

Next weekend, I'll study the wiring, and try and come up with a wiring diagram, just in case there's something stupid i've done with the connections?

 

[halcyon]

Next weekend, I'll study the wiring, and try and come up with a wiring diagram, just in case there's something stupid i've done with the connections?

Check voltages before you do anything, then the voltage on charge, voltage is the critical bit of data required.

Brian

 

[chrisbitz]

Check voltages before you do anything, then the voltage on charge, voltage is the critical bit of data required.

Brian

Thanks, I'll check voltages at the master switch, and on each battery terminal. is that enough? I can't easily get to the back of the alternator!

 

[Storyline]

.....
You also have to accept that even with fast charging devices your batteries wont get much above 85% charged in a day, see the link below, these guys know more about batteries than there is to know, they work on a maximum of 90% charge capacity because there are not enough hours in a day to get beyond that. Attach to shore power for a week then you may see a 100% charge..

I have got a 'Quick' 3 stage battery charger connected to 315ah's of domestic batteries. It goes into trickle charge and then sometimes I will turn it off. Are you saying it will still be trying to get the batteries from 90% to 100% of charge in trickle mode - ie I should always leave it on when connected to shore power ?

 

[halcyon]

Thanks, I'll check voltages at the master switch, and on each battery terminal. is that enough? I can't easily get to the back of the alternator!

Yes initially just at the switch and battery terminals will give a clue as to where to look. Having the initial voltage before you turn the batteries on will give a battery level, voltage with engine running will give charge indication if you have a likely problem.

Brian

 

[Richard10002]

Thanks for all the detailed replies guys!
It's beginning to slowly dawn on me that there may be a problem with the wiring...

I have a NASA Battery monitor, and I told it I have 210 AH of capacity (2x105AH batteries in parallel) and off it went. Meanwhile, whatever I've done, I've never seen more than about 90 AH of capacity shown.

The batteries are linked in parallel, ie showing 12v, not 24v! but maybe there's something else wrong?

I think battery monitors work out the capacity on the voltage of the battery, so if there's two batteries, does the voltage automatically stabilise between them?

Next weekend, I'll study the wiring, and try and come up with a wiring diagram, just in case there's something stupid i've done with the connections?

Wow! You have had lots of advice here - some of it a bit conflicting.

I have a NASA BM2 battery monitor. It is good for telling you the voltage of the battery bank, and for how many Ah are going in, and out, of it. IMHO it is no good at telling you anything else, I.e. the percentage bit isn't much use.

Do what Brian suggests, and measure voltage of individual batteries with everything switched off, (for hours or a day, if possible). Then start charging, and measure the battery voltages immediately then, say, every half hour, for say, 3 hours. Take the measurements across the battery posts to avoid a false reading due to poor connections.

It would also make sense to record the NASA reading each time you take a battery reading - volts and charge amps on the meter.

Once you have done that, I would report back here with a comprehensive set of results.

FYI my 330Ah bank is currently charging via the engine/alternator at 14.0V and the batteries are drawing 15.1A. When I started charging an hour or so ago, they were drawing about 30A.

I have seen the voltage as high as 14.2V, so I guess that is the max available from my alternator. When the amps being drawn falls to about 3A, I generally consider them as full as they are going to get, I.e. 1% of my bank size of 330Ah.

 

[jdc]

...they work on a maximum of 90% charge capacity because there are not enough hours in a day to get beyond that. Attach to shore power for a week then you may see a 100% charge.

http://msor.victoria.ac.nz/foswiki/pub/Main/ResearchReportSeries/mscs03-08.pdf

...

Are you sure you posted the correct link? The paper you posted does a good job of listing and justifying 3 different mathematical models for lead acid batteries, but does no empirical work or measurements to determine which is best for any particular purpose, and I found nothing connected to your assertion that 'they work on a maximum of 90% charge capacity' or 'not enough hours in a day to get beyond that' in the paper anywhere. The paper struck me as perhaps a good first step developing a physics based model for batteries, but of extremely limited relevance to the OP's query.

 

[Marsupial]

I have got a 'Quick' 3 stage battery charger connected to 315ah's of domestic batteries. It goes into trickle charge and then sometimes I will turn it off. Are you saying it will still be trying to get the batteries from 90% to 100% of charge in trickle mode - ie I should always leave it on when connected to shore power ?

Its a property of lead acid batteries - all types - that as the charge capacity goes beyond 80% the charge acceptance drops off and charge efficiency drops off. In practice this means it takes days to get a battery from 80% charged to 100%. This is why the submariners don't expect to get much more than 80% during normal surface running and they have more charging equipment on board than we have room for and dedicated crew whose reason for living is charging batteries. My link above to the submariners battery management shows a graph of charge attrition its very similar to what we see in yacht systems. Back to charging; the whole thing is further complicated by temperature and the great unknown :- what IS the actual capacity of the battery we are trying to charge? We know what the manufacturer thinks it was - so lets not worry to much about that.

In short if you have an intelligent charger with a correctly set float voltage you can leave it connected and it wont harm the batteries but will bring them slowly up to 100% over a couple of days. As soon as you cast off and go cruising you are in the 85% - 50% capacity range and should size your consumption to suit that. SO for example a 100 AH (nominal) battery will give you around 35 AH of usable power on a good day without its life being shortened by over discharging. AND you should be able to replace the charge within one day. Harsh but true.

ALL the above assumes batteries and charging systems are in good order.

 

[Marsupial]

I was more interested in the graph on page 2 that shows the ability to recharge (or not) batteries when the sub is in service. Not backed up by evidence but provided as a statement of fact. They have the same problems we have and suffer from the same limitations of lead acid technology. I would have thought that if anyone can get a lead acid cell to 100% in day they could - but it seems they cant so it does cast a few doubts on the claims from the "tuned up" regulator suppliers, the weak link is the lead acid cell.

 

[William_H]

Wow! You have had lots of advice here - some of it a bit conflicting.

I have a NASA BM2 battery monitor. It is good for telling you the voltage of the battery bank, and for how many Ah are going in, and out, of it. IMHO it is no good at telling you anything else, I.e. the percentage bit isn't much use.

Do what Brian suggests, and measure voltage of individual batteries with everything switched off, (for hours or a day, if possible). Then start charging, and measure the battery voltages immediately then, say, every half hour, for say, 3 hours. Take the measurements across the battery posts to avoid a false reading due to poor connections.

It would also make sense to record the NASA reading each time you take a battery reading - volts and charge amps on the meter.

Once you have done that, I would report back here with a comprehensive set of results.

FYI my 330Ah bank is currently charging via the engine/alternator at 14.0V and the batteries are drawing 15.1A. When I started charging an hour or so ago, they were drawing about 30A.

I have seen the voltage as high as 14.2V, so I guess that is the max available from my alternator. When the amps being drawn falls to about 3A, I generally consider them as full as they are going to get, I.e. 1% of my bank size of 330Ah.

I second that statement on battery monitors. They can give useful short term AH s in or out. Not really useful for battery percentage.
OP asked about batteries in parallel. This can either be hard wired at the batteries if you have a separate engine start battery or via a 1,2,both switch. If you have a 1,2,both switch then always charge on both. ie with batteries in parallel. The batteries will ballance charge and voltage. 2 batteries will take more total charge than one.
it is desirable in either set up to operate and discharge and engine start the batteries as individuals. One will die before the other and it is important to know they are both up to the necessary job of engine start. if they are hard wired in parallel then occasionally disconnect one to check the other. Certainly if you are going to check battery voltages when you go to the boat they need to be left isolated and checked individually. good luck olewill