Battle of the chargers

[noelex]

I had a Sterling mains charger until recently, if i turned it on the Victron solar controller output was virtually nil.

This is to be expected if the solar output is capable of raising the battery voltage above the set point of the Sterling. If the voltage set point of the Sterling is too low and the set point of the solar controller is appropriate then ideally the voltage set point of the Sterling should be raised (or the charger changed for one that can be adjusted). If this cannot be done, the combined output of the Sterling and the solar will never be lower than Sterling alone.

 

[GHA]

Thanks for your very constructive comments Paul. You have al least confirmed my suspicions. Indeed, my next step is to arrange a simple means of isolating the solar whilst under engine and see if the alternator ups it’s game.

It won't.
The batteries are in control of how much current goes in, all your charging sources do is stop going over a set voltage limit. The batteries don't care where the charge comes from. So if the solar has a voltage limit of say, 14.6v and less than the available power from the solar, say 5A is going into the batteries at that voltage and if the alternator has the same voltage limit then it won't make any difference if either/or or both are connected. 5A will go in. If the batts will accept more current at that voltage then when the alt is on they will. If the alternator has a lower voltage set point and you turn off the solar then less will go in.

 

[PaulRainbow]

lol, yes heard that, I hope he actually meant stopped producing any Amps, however an excited alternator that starts sending pulses (W terminal or whatever you call it) surely cannot "loose" that status and stop sending pulses for the tachometer, can it?

I don't think that however charged the batteries are that the alternator "turns off", it would just produce a minimal charge, pretty much as you reported above. I'd think that if the alternator output was zero, so the tacho stopped working, the charge warning light would come on. It's certainly not something i have ever seen.

 

[GerardV]

To all electrical experts, and others.

When away from shore power and during daylight my sailboat’s batteries can receive a charge from two sources.

(1) Solar panels which charge at a rate determined by an algorithm in a sophisticated MPPT controller.

(2) When under power, the engine’s alternator which relies on an unsophisticated internal regulator to determine its charging current.

My question is;
If both sources of a charge are active and the MPPT controller applies a voltage that is higher than the alternator’s output voltage, could the alternator’s regulator be fooled into thinking that the battery is full? Resulting in the alternator significantly reducing its output even though the batteries are still hungry.

Mike

I had the problem that the alternator of my VP2030 stopped charging because of the solar panels. Also I had the tachometer problem. I solved this using a relay. The relay disconnects the solarpanels from the solarcontroller when the engine runs. It simulates the night situation for the solar controller.

 

[TernVI]

I don't think that however charged the batteries are that the alternator "turns off", it would just produce a minimal charge, pretty much as you reported above. I'd think that if the alternator output was zero, so the tacho stopped working, the charge warning light would come on. It's certainly not something i have ever seen.

In simplest terms, the alternator has a set voltage, it will attempt to generate say 14.4V. with some output impedance.
But it may be a case of turning itself down at 14.5V and back up at 14.3V say, so it is possible that a solar input which holds the batteries at e.g. 14.35V would reduce the output of the alternator.
These are not static systems, the control mechanisms are continually adjusting stuff and not always in a linear and immediate way.
Delays and hysteresis aid stability.

So in the fine detail you can get some right odd effects even with simple systems like 'dumb' alternators.

When you have 'smart' systems which make 'decisions' about the state of the batteries, there is potential for cocking up the information they work with to decide for example when to switch from float back to boost or how long to apply absorption charge.

Does it matter?
That depends on what you really need from the system.

Part of the problem is there are a thousand different smart charger firmware releases and thousands of different alternators and regulators. Then everyone's install is a bit different.

Boats tend to use equipment like chargers and alternators slightly different from what the designers intended, so I think there is an element of the user needing to keep an eye on things at least.

 

[PaulRainbow]

In simplest terms, the alternator has a set voltage, it will attempt to generate say 14.4V. with some output impedance.
But it may be a case of turning itself down at 14.5V and back up at 14.3V say, so it is possible that a solar input which holds the batteries at e.g. 14.35V would reduce the output of the alternator.
These are not static systems, the control mechanisms are continually adjusting stuff and not always in a linear and immediate way.
Delays and hysteresis aid stability.

So in the fine detail you can get some right odd effects even with simple systems like 'dumb' alternators.

When you have 'smart' systems which make 'decisions' about the state of the batteries, there is potential for cocking up the information they work with to decide for example when to switch from float back to boost or how long to apply absorption charge.

Does it matter?
That depends on what you really need from the system.

Part of the problem is there are a thousand different smart charger firmware releases and thousands of different alternators and regulators. Then everyone's install is a bit different.

Boats tend to use equipment like chargers and alternators slightly different from what the designers intended, so I think there is an element of the user needing to keep an eye on things at least.

Absolutely agree, it's important to keep an eye on things, at least to start with, so you know how your equipment works, on your boat.

 

[PaulRainbow]

This is to be expected if the solar output is capable of raising the battery voltage above the set point of the Sterling. If the voltage set point of the Sterling is too low and the set point of the solar controller is appropriate then ideally the voltage set point of the Sterling should be raised (or the charger changed for one that can be adjusted). If this cannot be done, the combined output of the Sterling and the solar will never be lower than Sterling alone.

That's not the case. I've had days when the Sterling has gone into standby mode and the solar yield has been very low, but the Sterling has not "woken up", leaving the battery current with a minus reading.

The settings on the Sterling, the new Victron and the solar controller are all the same.

I only fitted the Victron charger on Saturday, not had time to do much testing yet.

 

[Ammonite]

I don't think that however charged the batteries are that the alternator "turns off", it would just produce a minimal charge, pretty much as you reported above. I'd think that if the alternator output was zero, so the tacho stopped working, the charge warning light would come on. It's certainly not something i have ever seen.

I haven't seen it with my solar but when I was testing the engine with the shorepower/mains charger connected the tacho would stop working. The warning light didn't come on

 

[nigel1]

I had a Sterling mains charger until recently, if i turned it on the Victron solar controller output was virtually nil. I just changed the mains charger to a Victron one and the solar controller keeps charging, whilst the mains charger quickly went into standby. Early days for the new combination, but i'll keep monitoring.

So, It's hard to say for sure what would happen in your case. A decent battery monitor should help to see what's going on. Should you find that the alternator output is severely limited by the voltage from the solar controller you could look into ways to prevent that. For instance, a normally closed relay in the circuit from the solar panels to the controller, with the energising coil connected to the ign switch. I do suspect that you won't need to though.

That seems to be the opposite to what I am experiencing with a new Sterling Pro charge ultra.
When it is first turned on, it goes to bulk/absoption, and an hour later, if the solar output is good, the Sterling Charger goes straight to standby mode.
As the solar charge drops in late afternoon, the Sterling wakes up when it senses battery voltage less than 12.8V or there is more than a 5 amp load.
However, it only wakes up into float mode. I need to contact Sterling to find out what would kick the charger back into bulk.

Incidently, I have a bog standard 60A alternator contolled by an Adverc regualtor, solar panels with a Blue Sky MPPT controller, and a D400 wind geny.
I have adjusted the wind geny controller voltage output to 14.7V, and have the solar set at 14.8V, to avoid a gust of wind prematurely putting the solar controller into float.

 

[roaringgirl]

We have a Balmar controller on the alternator, an MPPT controller on the 250W solar panel and another MPPT on 200W of solar and a Rutland 1200 windgen. Each charge controller reads the voltage of the battery and decides the charge state. If the battery is receiving sufficient charge from one source to raise the voltage to a level where it looks fully charged to the other controllers, you can't push more charge in anyway so you shouldn't care.

Yes, there is some chaotic interaction between the slow switching of charge profiles on different controllers in response to cloud cover or wind gusts, but not enough to make a real-world difference. We make enough power with wind and solar at anchor to be able to run the (DC) watermaker every day to top up the tanks, we never run the engine to charge the batteries and only have to plug in in marinas if we stay for several days where the main solar panel is overshadowed by masts.

 

[noelex]

That's not the case. I've had days when the Sterling has gone into standby mode and the solar yield has been very low, but the Sterling has not "woken up", leaving the battery current with a minus reading.

The settings on the Sterling, the new Victron and the solar controller are all the same.

I only fitted the Victron charger on Saturday, not had time to do much testing yet.

If the solar output is not keeping up with discharge, the voltage will drop slightly and the Sterling charger will kick in and initiate a new bulk cycle. It should take only a very minimal discharge before the Sterling recognises this.

The voltage set point where the battery charger will initiate a new bulk cycle is known as the "battery return voltage". On the better chargers this set point is adjustable and it sounds like the Sterling is set too low for your configuration, but unless the setting is totally inappropriate the battery charger will initiate a new bulk cycle before the battery discharge is significant, so it is not a great concern.

If the "battery return voltage" is adjustable, it is worth modifying the default to ideally suit your system. This is important not just when there are multiple charge sources, but also when there are discharge loads greater than the battery charger's output. This will create the same issue.

Keep in mind that the simple battery charging algorithms in our charge sources will never be perfect. Even when ideally set, it is a compromise. There will be minor amounts of under or overcharging in various situations. These small deviations from the ideal annoy perfectionist, like me but they have little practical influence on the lifespan of a lead acid battery and rather than worrying unduly just go sailing.

 

[nigel1]

If the solar output is not keeping up with discharge, the voltage will drop slightly and the Sterling charger will kick in and initiate a new bulk cycle. It should take only a very minimal discharge before the Sterling recognises this.

The voltage set point where the battery charger will initiate a new bulk cycle is known as the "battery return voltage". On the better chargers this set point is adjustable and it sounds like the Sterling is set too low for your configuration, but unless the setting is totally inappropriate the battery charger will initiate a new bulk cycle before the battery discharge is significant, so it is not a great concern.

If the "battery return voltage" is adjustable, it is worth modifying the default to ideally suit your system. This is important not just when there are multiple charge sources, but also when there are discharge loads greater than the battery charger's output. This will create the same issue.

With the Sterling charger I have, the return voltage is set at 12.8V, and does not appear to be adjustable.
I have only just fitted this charger, the previous Sterling charger I had did not have a standby mode. Only been able to observe this one workking for a couple of days, but when it comes out of standby mode, it goes into float charge, rather than bulk.

I called Sterling to ask about this, and the tech was not 100% sure on when it would go back into bulk, but did say if the load was big enough, the charger would go into bulk. Will need to experiment with this at some point.

 

[noelex]

I have only just fitted this charger, the previous Sterling charger I had did not have a standby mode. Only been able to observe this one workking for a couple of days, but when it comes out of standby mode, it goes into float charge, rather than bulk.

I called Sterling to ask about this, and the tech was not 100% sure on when it would go back into bulk, but did say if the load was big enough, the charger would go into bulk. Will need to experiment with this at some point.

Interesting.

Normally the "battery return voltage" will initiate a new bulk cycle rather than a float cycle. In fact, some manufacturers call the "battery return voltage" the "bulk return voltage".

The Sterling battery chargers must have some alternative set point which will cause them to return to bulk otherwise even if we ignore alternative charge sources they would not function correctly.

Imagine the situation where the battery is fully charged and connected to the battery charger, but then a large load is engaged which is much greater than the battery charger output. For example electric cooking, watermaker etc. these loads can be greater than battery charger is capable of outputting and the battery will in some situations become significantly depleted despite a permanent connection to the battery charger. A battery charger that only defaults back to a float voltage after this high load would potentially leave the battery in low state of charge.

The battery charger needs to recognise the battery has suffered some loss and initiate a new bulk and absorption phase before dropping down to the float voltage. This is normally governed by the "battery return voltage" setting. Once the battery charger records a voltage below this threshold it will initiate a new bulk and absorption cycle. It is strange that the Sterling does not do this and only initiates a float cycle. This may be why Paul is finding the Sterling charger has a problem compared to his Victron charger.

I am not very familiar with Sterling battery chargers, but they have a good reputation so I think they must have some set point where they initiate a new bulk/absorption cycle otherwise the battery charger would not function well even as the only charger connected to the batteries.

 

[nigel1]

I am not very familiar with Sterling battery chargers, but they have a good reputation so I think they must have some set point where they initiate a new bulk/absorption cycle otherwise the battery charger would not function well even as the only charger connected to the batteries.

When I'm back on the boat I'll see what happens if I put the invertor on to power the water heater, that should put a 100 amp load on the bank.

 

[PaulRainbow]

If the solar output is not keeping up with discharge, the voltage will drop slightly and the Sterling charger will kick in and initiate a new bulk cycle. It should take only a very minimal discharge before the Sterling recognises this.

The voltage set point where the battery charger will initiate a new bulk cycle is known as the "battery return voltage". On the better chargers this set point is adjustable and it sounds like the Sterling is set too low for your configuration, but unless the setting is totally inappropriate the battery charger will initiate a new bulk cycle before the battery discharge is significant, so it is not a great concern.

If the "battery return voltage" is adjustable, it is worth modifying the default to ideally suit your system. This is important not just when there are multiple charge sources, but also when there are discharge loads greater than the battery charger's output. This will create the same issue.

Keep in mind that the simple battery charging algorithms in our charge sources will never be perfect. Even when ideally set, it is a compromise. There will be minor amounts of under or overcharging in various situations. These small deviations from the ideal annoy perfectionist, like me but they have little practical influence on the lifespan of a lead acid battery and rather than worrying unduly just go sailing.

Although the Sterling charger has worked well (as a charger) I don't think it plays as well with my solar setup as the Victron one does, but it's early days with the Victron. It's looking good so far though.

 

[mikegunn]

Hey guys, thank you very much for your contributions of experiences and knowledge. It’s good to know that my problem is not unique to my setup. As a result I’ve now fitted a more accessible switch into my PV feed into its MPPT controller. When I next get sailing/motoring free from shore power I’ll do some experimenting. If I do confirm that the solar is preventing the alternator from charging it’ll be a simple solution to replace my temporary switch with a relay, per Paul’s and GerardV’s suggestions. I’ll endeavour to report back anyway.
Mike

 

[noelex]

Hey guys, thank you very much for your contributions of experiences and knowledge. It’s good to know that my problem is not unique to my setup. As a result I’ve now fitted a more accessible switch into my PV feed into its MPPT controller. When I next get sailing/motoring free from shore power I’ll do some experimenting. If I do confirm that the solar is preventing the alternator from charging it’ll be a simple solution to replace my temporary switch with a relay, per Paul’s and GerardV’s suggestions. I’ll endeavour to report back anyway.
Mike

As you may gather from my posts on this subject, I do not think this is a good idea, but if do want to implement this, be careful what is switched. Most solar controllers require the power from the solar panels to be disconnected before disconnecting the controller from the batteries, but there are some controllers that specify the opposite order. You can sometimes permanently damage the controller if this is done in the wrong order, especially if this is switched frequently.

If you are switching the solar panel side, which would be better for most controllers, the voltage output of the solar panels need to be considered. High DC voltages are difficult to switch safely so make sure the switch is rated for the solar panel voltage, especially if you have modern high voltage panels or multiple low voltage panels in series.

Good luck and please report your findings. You should be able to easily see if the total current entering the batteries goes up or down as you switch the solar panels off and on. You might consider a temporary set up until the results are in.

 

[vas]

does switching say 80+V DC create any spikes that could damage things? is that amongst your concerns noelex?

btw, if the OP has a Victron MPPT controller, it's dead easy to disable it from s/w using BT connection, done it a few times while testing, no need for any switches and messing with cables!

 

[noelex]

btw, if the OP has a Victron MPPT controller, it's dead easy to disable it from s/w using BT connection, done it a few times while testing, no need for any switches and messing with cables!

Your idea of switching off the controller output via the software is an excellent one. It does not require any physical changes and can be easily reversed when it doesn’t work .

does switching say 80+V DC create any spikes that could damage things? is that amongst your concerns noelex?

Switching 80+ V AC is easy, as the AC waveform passes through 0 V therefore any arc between the switching contacts is extinguished. Switching 80 V DC is much harder. There are switches and circuit breakers that will do this safely, but most standard marine switching gear is limited to 32 V DC. The consequences of exceeding these ratings can be quite spectacular, and not a good kind of spectacular .

So just a heads up to the OP if he wants to use a physical switch to make sure it has a suitable rating if he has multiple panels in series or one of the increasingly common high voltage panels. This is not difficult to do, but is a detail easily overlooked when most boat wiring is 12 V DC and these concerns do not apply.

 

[Pete7]

So, you think the video above is not a load of nonsense ?

No the exact opposite, it is a load of nonsense, well I think so anyway. I watched another of his videos a couple of years back when he was trying to flog products he sold during a presentation only broken by lots of waffle.