Leisure Battery not reaching full charge on Alternator

chas142

Full Member

Messages
198
Assuming that you have a standard alternator and a digital voltmeter, start you vehicle and check voltage at vehicle battery, then rev up the engine to say 1500-2000 rpm, the voltage needs to be above 14v, better a bit higher at about 14,4v assuming the batteries are charged, might have to run it for a few minutes. Check the voltage at the liesure battery, it should be the same-ish if all charged, again run for a few minutes. To check the amps output of the alternator switch on headlights, heater blower, and recheck voltages, here you would hope to get 14v at the vehicle battery, perhaps a bit less at liesure battery, now also switch on your fridge and recheck at both batteries. Hopefully you will have 13.8 and 13.5, which means it is balancing the load that you have switched on. It will charge at these voltages but will take longer. If you have a clamp on ammeter you can use that to check power going into the battery, a digital voltmeter is much better that a analog version.
 

Molly 3

Full Member

Messages
819
Some good eye opening videos on you tube . some by Sterling explaining the problems .with s mart alternators.
 
Last edited:

paulhelenwilko

Full Member

Messages
382
Assuming that you have a standard alternator and a digital voltmeter, start you vehicle and check voltage at vehicle battery, then rev up the engine to say 1500-2000 rpm, the voltage needs to be above 14v, better a bit higher at about 14,4v assuming the batteries are charged, might have to run it for a few minutes. Check the voltage at the liesure battery, it should be the same-ish if all charged, again run for a few minutes. To check the amps output of the alternator switch on headlights, heater blower, and recheck voltages, here you would hope to get 14v at the vehicle battery, perhaps a bit less at liesure battery, now also switch on your fridge and recheck at both batteries. Hopefully you will have 13.8 and 13.5, which means it is balancing the load that you have switched on. It will charge at these voltages but will take longer. If you have a clamp on ammeter you can use that to check power going into the battery, a digital voltmeter is much better that a analog version.
I shall give this a try when I next get to the van. Thankyou.
 

wildebus

Full Member

Messages
2,839
Left the van on hook up for 36hrs. Voltage has increased to 13.99 volts. (multi meter reading)
That is not necessarily actually very promising :(

Being on hookup for 36 hours, you would expect the battery to have got a full charge (which would have taken the battery to probably/ideally around 14.4V or so - could be more if any temperature compensation) and then the charger would, if it is a multi-stage charger, dropped into a Float mode, in which it will drop the charger voltage to between 13.6V-13.8V, depending on how it is setup.

This is an example of the kind of charging pattern you want on a Lead Acid Battery (my batteries like a lower 14.2V charge rather than 14.4V hence why that is low on this graph)
1580688933469.png
My charger also has a Storage Mode which lowers the voltage again (not all chargers do).
By 36 Hours if your battery is not in a Float or Storage mode situation, then either the Battery has a problem or the Charger is not suitable for this use (much to small an output or a basic one with a set output)

What mains charger have you got? It sounds like one in which you should not actually leave plugged in for so long as it is not letting the battery go into float OR it is not reaching a high enough voltage to fully charge the battery. Either way, I'd suggest it is something you look into further to best look after your battery.

Now it is possible your charger is in float and it is very cold where you are so the temperature compensation has increased the voltage by around 0.2V but I am going to guess that is not the case and what I said above still stands for your setup.
 

chas142

Full Member

Messages
198
Hi,
Looking at your graph am I reading that right that your in vehicle charger starts charging at 120 amps?:eek: I assume you must have a large battery bank and probably cook by electric? The graph shows very well what you system does and at what state it is in the process.

Now if Paul had you system we would know exactly what and where his state of charge was. Unfortunately he only appears to have a multi meter. His initial question, (I believe), was about driving 50miles and his leisure battery was not charged. If it was me I would start with the basics vehicle test first, see what readings he gets and go from there.

Sorry only my opinion.:)


That is not necessarily actually very promising :(

Being on hookup for 36 hours, you would expect the battery to have got a full charge (which would have taken the battery to probably/ideally around 14.4V or so - could be more if any temperature compensation) and then the charger would, if it is a multi-stage charger, dropped into a Float mode, in which it will drop the charger voltage to between 13.6V-13.8V, depending on how it is setup.

This is an example of the kind of charging pattern you want on a Lead Acid Battery (my batteries like a lower 14.2V charge rather than 14.4V hence why that is low on this graph)
View attachment 52823
My charger also has a Storage Mode which lowers the voltage again (not all chargers do).
By 36 Hours if your battery is not in a Float or Storage mode situation, then either the Battery has a problem or the Charger is not suitable for this use (much to small an output or a basic one with a set output)

What mains charger have you got? It sounds like one in which you should not actually leave plugged in for so long as it is not letting the battery go into float OR it is not reaching a high enough voltage to fully charge the battery. Either way, I'd suggest it is something you look into further to best look after your battery.

Now it is possible your charger is in float and it is very cold where you are so the temperature compensation has increased the voltage by around 0.2V but I am going to guess that is not the case and what I said above still stands for your setup.
 

wildebus

Full Member

Messages
2,839
Hi,
Looking at your graph am I reading that right that your in vehicle charger starts charging at 120 amps?:eek: I assume you must have a large battery bank and probably cook by electric? The graph shows very well what you system does and at what state it is in the process.

Now if Paul had you system we would know exactly what and where his state of charge was. Unfortunately he only appears to have a multi meter. His initial question, (I believe), was about driving 50miles and his leisure battery was not charged. If it was me I would start with the basics vehicle test first, see what readings he gets and go from there.

Sorry only my opinion.:)
I was answering the last part only and his update about his battery after a day and a half on a mains charger :) (I have deliberately not replied to the question about alternator charging as plenty of people had already contributed to that and I didn't want to add confusion by adding my own thoughts on that aspect).

The graph shows the voltage and current from my MAINS Battery charger and yup - it is only putting in 120A as the charger cannot provide any more :( Below I am helping it out by running the engine so the net current went upto 147A :D
1580745934227.png
As far as shoving 120A into a battery (or 147A for that matter), you are quite right - it depends on the size and type of the battery bank. Typically for AGMs, you should aim at no greater than 25% charge rate i.e. no more than 25A per 100Ah. My bank is 645Ah, so I could on that basis have a maximum rate of around 160A (my actual batteries are specifically noted as having no upper limit but in reality they follow the standard charge pattern - they are sucking up that much current as the batteries were at around 40% SOC so needed the juice!)
 

in h

Full Member

Messages
747
I don't know how you have come to that conclusion Tony as for instance in my self built installation where I have a van battery which is connected via a split charge relay to 2 leisure batteries and at the end of a 2 to 3 hour journey all 3 batteries are showing over 14v when tested.
"Showing over 14v is a sign that the batteries are not yet fully charged. Only when the voltage drops back to 13.7v showing that the regulators thinks they're full.
The alternator is charging the starter battery. The habitation batteries have a different state of charge, needing different treatment, which a split charge system cannot give.
 

paulhelenwilko

Full Member

Messages
382
Assuming that you have a standard alternator and a digital voltmeter, start you vehicle and check voltage at vehicle battery, then rev up the engine to say 1500-2000 rpm, the voltage needs to be above 14v, better a bit higher at about 14,4v assuming the batteries are charged, might have to run it for a few minutes. Check the voltage at the liesure battery, it should be the same-ish if all charged, again run for a few minutes. To check the amps output of the alternator switch on headlights, heater blower, and recheck voltages, here you would hope to get 14v at the vehicle battery, perhaps a bit less at liesure battery, now also switch on your fridge and recheck at both batteries. Hopefully you will have 13.8 and 13.5, which means it is balancing the load that you have switched on. It will charge at these voltages but will take longer. If you have a clamp on ammeter you can use that to check power going into the battery, a digital voltmeter is much better that a analog version.

Since being on mains charge the moho has been returned to storage and back (4miles) and sat for 10days (with some i/p from solar).

On return home today : LB was 13.5V and VB was 12.76V. (LB = leisure battery, VB=Van battery)

As suggested I took the following measurements (without being hooked up ) :

1581544027646.png

Switched on headlights and blower :

1581544159711.png

Switched on Fridge :

1581544302824.png

This appears to be close to your expectations ?

Is this all telling me that it is unlikely I will achieve a fully charged leisure battery using the alternator alone ?

Paul
 
Last edited:

chas142

Full Member

Messages
198
You should also rev the engine to 2000 rpm for the last 2 tests, you are looking for an increase from what you have @ 800 rpm. Fridges draw approx. 10amps, can be quite a high load on that circuit, especially if its linked in with the LB charging circuit.

You say that voltage was 13.5 & 12.76, how long was the engine switched off for before this test? Was the Solar connected? I assume it charges the liesure battery only? or is it a dual battery controller, I don't think so due to the readings given, but some can be set with a battery charge priority and or % split.

The battery voltage will gradually drop back down after charge, it wont stay at 14volts as that is the approx. voltage when it is being charged. If the battery is charged then disconnected so no load or solar you can check the off load voltage after 12 -24 hours, it should be above 12.6 volts. This is only a guide on your battery condition. You could have 12.6 volts month later but still have a low power output from the battery.

It depends what you mean by getting a fully charged battery, (what are you expecting?), if you were to have a none maintenance free battery you could remove the lids and check with a hydrometer the S.G. of each cell, 1260 or hopefully above say 1280 is good, but ideally all cells would read the same, with a reading of just voltage of the 6 cells it is not giving you the details of each cell, and you also have to wait for the residual charge to dissipate.

Most batteries will probably never be fully charged, 1260 SG is 50% charge. Most batteries are sealed now so many off the old tests can't be done, that has taken away lots of options, this is why there are lots of different types of electronic systems now available that basically compute where you battery is in regard to charge and condition. Some people will just have a digital voltmeter on the dash, perhaps a dual meter for both batteries.

Hope this helps.








Since being on mains charge the moho has been returned to staorage and back (4miles) and sat for 10days (with some i/p from solar).

On return home today : LB was 13.5V and VB was 12.76V. (LB = leisure battery, VB=Van battery)

As suggested I took the following measurements (without being hooked up ) :

View attachment 53008

Switched on headlights and blower :

View attachment 53010

Switched on Fridge :

View attachment 53011

This appears to be close to your expectations ?

Is this all telling me that it is unlikely I will achieve a fully charged leisure battery using the alternator alone ?

Paul
 

Tony Lee

Full Member

Messages
72
I don't know how you have come to that conclusion Tony as for instance in my self built installation where I have a van battery which is connected via a split charge relay to 2 leisure batteries and at the end of a 2 to 3 hour journey all 3 batteries are showing over 14v when tested.
I think others have covered it but at that stage - assuming the battery voltage was still increasing - I would say 80% would be pushing it. To get to 100% the voltage would need to reach well over 14 V and then be held there for at least a couple of hours at which time it would still be only 90% full. That last 10% is the hard part

Obviously depends on how full the batteries are when you set out, but the arithmetic is simple. Pump 15 amps in if you are lucky for 3 hours will add about 40 amp hours or less and probably closer to 30 amp hours or even less, isn't going to fill 2 batteries unless they are only down to 90% to start with.
 
Last edited:

chas142

Full Member

Messages
198
"Showing over 14v is a sign that the batteries are not yet fully charged. Only when the voltage drops back to 13.7v showing that the regulators thinks they're full.
The alternator is charging the starter battery. The habitation batteries have a different state of charge, needing different treatment, which a split charge system cannot give.
A standard alternator regulator will not drop back to 13.7v, voltage will remain above 14, depending on the load and revs. Test bench situation; It only monitors the voltage, as the battery voltage increases it reduces the amperage in the rotor circuit, thus reducing the alternator output. Note this is with a standard regulator fitted in a standard alternator.

Note, I came across some batteries that were advised by me, 1 faulty and 1 incorrect type 1 year ago. Horsebox drove to Portugal, hooked up to mains for 5 weeks, both batteries exploded. Those batteries were probably 100% fully charged. Faulty battery approx 15 years old, may have gone open circuit and caused a spark inside the battery. Could have also been excessive gassing eating through a wire close to the battery or one of the relays chattering causing a spark inside one of the relays, a mouse had eaten through various wires in the control pannel. I don't know if it was an English mouse or a European mouse.:LOL::ROFLMAO::LOL:
 
Last edited:

xsilvergs

Full Member

Messages
98
Here is charging from a 2017 Fiat Ducato alternator. This was a drive down a motorway, a bit stop - start and slow progress due to an accident. I will be fitting a B2B charger

View attachment 52793
I posted this earlier which from my 2017 Ducato. I will be fitting a B2B before I fit a second battery unlike many motorhomes I come across. A single Battery "fully charged" will last me, coupled with my decent solar set up, for a couple of nights.
Without a B2B I would have two partially charged batteries which seems a bit pointless.
Thanks to Victron I know the SOC of my batteries and can see the weak link is the alternator.
Come May when I fit a B2B I will post the results, sort of before and after graphs.
 
Last edited:

chas142

Full Member

Messages
198
Looking at your graph I assume that you didn't start to drive until approx. 09.00, and your battery was already 75% charged. TBH, I wondered if you had your fridge on 12v and other electrics on, as that would explain with your stop start traffic the lower than expected readings, for volts and amps. You also say you have solar, that could also differ some readings depending on conditions and where connected in. So lots of variables to take into account, which is why I said in my post test bench conditions. What time did you stop driving as with solar added in from say 10.00 more variables & clouds.

Your Victron will obviously give you a much better idea of your battery and charging system than just a voltmeter. Other systems are also available.

Will be interesting to see your results later, before and after B2B, ideally with identical conditions though. Is your alternator standard? and do you have a standard split charge system?
 
Last edited:

chas142

Full Member

Messages
198
Should have said some systems can monitor vehicle and leisure battery, so can make it clearer as to what is happening with second set of readings.
 
Last edited:

xsilvergs

Full Member

Messages
98
Looking at your graph I assume that you didn't start to drive until approx. 09.00, and your battery was already 75% charged. TBH, I wondered if you had your fridge on 12v and other electrics on, as that would explain with your stop start traffic the lower than expected readings, for volts and amps. You also say you have solar, that could also differ some readings depending on conditions and where connected in. So lots of variables to take into account, which is why I said in my post test bench conditions. What time did you stop driving as with solar added in from say 10.00 more variables & clouds.

Your Victron will obviously give you a much better idea of your battery and charging system than just a voltmeter. Other systems are also available.

Will be interesting to see your results later, before and after B2B, ideally with identical conditions though. Is your alternator standard? and do you have a standard split charge system?

QUOTE="xsilvergs, post: 172270, member: 5434"]
I posted this earlier which from my 2017 Ducato. I will be fitting a B2B before I fit a second battery unlike many motorhomes I come across. A single Battery "fully charged" will last me, coupled with my decent solar set up, for a couple of nights.
Without a B2B I would have two partially charged batteries which seems a bit pointless.
Thanks to Victron I know the SOC of my batteries and can see the weak link is the alternator.
Come May when I fit a B2B I will post the results, sort of before and after graphs.
[/QUOTE]
Our fridge is a Thetford 3 way fridge and would have been on DC supply drawing about 10 amps.
The alternator is standard Fiat fitment (non smart type).
From info supplied by Wildebus the output from a B2B would be 30 amps from the moment the engine starts to the point it goes into absorption. Unlike the graph trace I attached.
I think the drive in the graph finished about 12 noon.
A few days before the graph above the battery had been discharged to 50% SOC and from memory the the charge current was alarmingly low.
Our van has a Nordelectronica control unit, there is very little volt drop in the lead (I monitor that too). I can see better charging with my Victron MPPT charger than the alternator!
 

chas142

Full Member

Messages
198
Yes the charge current & voltage seem low to me after about 09.30, but your SOC seem good, according to your Victron, but it took a long time to get there. Did you check for volts drop on both sides + & - side. As a separate unit with separate wiring a B2B may give you a better charge, but if your system was showing a 40amp charge dropping to 20amps perhaps not so much.

My battery testing days go back to pre-maintenance free, when all battery tops could be removed and a Specific Gravity test and a Cadmium Voltage test cold be done on each cell. I wonder if anyone has that capability here, having a standard liesure wet battery, a hydrometer and a Victron. Just interested to see if all readings matched.
 

xsilvergs

Full Member

Messages
98
Yes the charge current & voltage seem low to me after about 09.30, but your SOC seem good, according to your Victron, but it took a long time to get there. Did you check for volts drop on both sides + & - side. As a separate unit with separate wiring a B2B may give you a better charge, but if your system was showing a 40amp charge dropping to 20amps perhaps not so much.

My battery testing days go back to pre-maintenance free, when all battery tops could be removed and a Specific Gravity test and a Cadmium Voltage test cold be done on each cell. I wonder if anyone has that capability here, having a standard liesure wet battery, a hydrometer and a Victron. Just interested to see if all readings matched.
My battery days go back to the early 80's, I worked on aircraft so doing capacity tests etc on lead and alkaline batteries/cells.

B2B is the answer 😀
 

Users who viewed this discussion (Total:0)

Top