Solar installation vs Alternator regulator

[Needtosail]

Hello all. Newly registered but was reading the forum since a while. Very helpfull informations.

I have a solar installation with MPPT regulator. My alternator is regulated by the built-in regulator.

While motoring, the alternator can't get over 13,7 volts. I've been told that this is because at the same time, the solar MPPT regulator sends 14,3 volts to the battery. So the built-in alternator regulator reeds that 14,3 volts and then reduces his voltage to 13.7 or less to go on absorbtion or floating.

To solve that problem, i need to shut off the Solar MPPT regulator. Then, the alternator will reed the exact battery voltage ( let say 12.8 volts) and then reach the bulk charge voltage of 14,3 volts. Didn't tried it yet since boat is winterized.

Does that make sense ?
Is there a better way to solve that problem ( Balmar regulator), don't want to spend my time switching on and off the solar installation ?
Any other idea on this ?

Thanks all for your help.

[travellerw]

Hhmm quick question.. Do you have a "Battery Combiner" aboard? If you do, this may be part of your problem. A diode based battery combiner will drop between 0.5v-0.6v between your alternator and the house batts. This could explain your max voltage of 13.7-13.8V.

[travellerw]

Ok wait.... One more question.. Does the alternator get over 13.8V when motoring at night? If so, then your MPPT has nothing to do with your problem.

[Needtosail]

I have a battery combiner but it reaches easily 14,3 amps on shore power or by solar while engine is not running.

Never check the amps while motoring at night or with the MPPT switched to off. Can't do it now since the boat is winterized.

''Does the alternator get over 13.8V when motoring at night? If so, then your MPPT has nothing to do with your problem''

I would think that if it was the case, the MPPT WOULD BE the problem....

There my be something I don't understand here....

[Dsanduril]

If the MPPT controller is at 14.3V then your whole bus must be at 14.3V (absent diode combiners, etc.). There is no way for you to be feeding 14.3V to the batteries from the MPPT and for the alternator to only be at 13.7V. If you are charging the same battery then the voltage has to be the same throughout the system.

Well, there is a way, and it is voltage drop because of bad connections/diode combiners/too small cables. But, other than that, if the MPPT is actually at 14.3V then so is the whole system. If the bus is at 13.7V with the alternator running then it is because of the alternator regulator. And that also means there is not enough solar output for the MPPT to get the voltage above 13.7.

[travellerw]

Originally Posted by Needtosail

I have a battery combiner but it reaches easily 14,3 amps on shore power or by solar while engine is not running.

Never check the amps while motoring at night or with the MPPT switched to off. Can't do it now since the boat is winterized.

''Does the alternator get over 13.8V when motoring at night? If so, then your MPPT has nothing to do with your problem''

I would think that if it was the case, the MPPT WOULD BE the problem....

There my be something I don't understand here....

In a typical installation of a battery combiner, it would not be involved when you are plugged into shore power or with solar.... Let me see if I can explain.

The battery combiner is installed between your alternator/start battery and your house bank. It isolates your house bank from your starter battery and alternator. Being a diode it only allows current to flow one way (from the alternator to the house bank). You can think of it as a one way valve with flow going out of the alternator to the house bank (however this valve is not %100 efficient and loses 0.5v-0.6v when passing the current).

Now on the house bank side of this one way valve will be all your other charging sources. Since they are directly hooked up to the house bank, they don't have to go through the combiner (and thus have no loss). This is exactly how my boat and countless others I have worked on are configured. My alternator will never charge my house batts over 13.8V-13.9V, even though I can put a multimeter on my start batt and see 14.4V. I'm guessing your boat is configured the exact same way..


and yes, you are correct.. I meant if your alternator does go over 13.8V at night then the MPPT is the problem (but very doubtfull to me).

[Needtosail]

If I install a Balmar external regulator, I know that it will sense the voltage on the output of the battery combiner. In that case, with the solar MPPT off, it would read 13,7 volts out of the combiner and then rise the voltage in order to get 14,3 volts after the combiner.(ex: 14,9 volts out of the alternator minus 0.6 volts lost in the combiner)

Am i right ?

[travellerw]

Originally Posted by Needtosail

If I install a Balmar external regulator, I know that it will sense the voltage on the output of the battery combiner. In that case, with the solar MPPT off, it would read 13,7 volts out of the combiner and then rise the voltage in order to get 14,3 volts after the combiner.(ex: 14,9 volts out of the alternator minus 0.6 volts lost in the combiner)

Am i right ?

No I have not seen a system that would actually raise the voltage on the alternator to compensate for the combiner loss. If it did that, then the voltage on the start batt would be WAY to high.

However, our boat was originally wired with and external regulator that sensed the voltage on the other side of the combiner. It would engage a bypass relay to connect the alternator directly to the house batts when it detected a higher voltage was required. It would then kick the relay off once the batts had hit float, leaving the combiner to float them at 13.8 or so.

I ended up removing that setup as it was starting to have problems (the regulators were just old). I have left the relays connected to switches at the helm. I can manually turn the relay on if required, however I have never had the need (we have tons of solar).

[travellerw]

Sorry.. I forgot to add.. There are now more modern combiners that don't use diodes. They essentially use solid state relays and do not have the loss. That would be the easiest way to solve the issue you are facing.

[smac999]

Originally Posted by travellerw

Sorry.. I forgot to add.. There are now more modern combiners that don't use diodes. They essentially use solid state relays and do not have the loss. That would be the easiest way to solve the issue you are facing.

the old diode based ones are called isolators. they split alternator current between outputs. the newer non diode, relay based ones that simply parallel batteries together, are called combiners. there are also now low loss isolators using fets

if your MPPT is reaching absorb voltages then they batteries aren't that low and the alternator doesn't need to be putting out full current anyways.

if the house bank is at 14.3 from solar. the alternator can not reduce voltage. it will reduce current. if you are measuring 14.3 at the house bank and 13.7 at the alt. you have some wiring issues going on.

you really need to provide a compleate drawing of your system before people can help you much more.

[smac999]

Originally Posted by travellerw

No I have not seen a system that would actually raise the voltage on the alternator to compensate for the combiner loss. If it did that, then the voltage on the start batt would be WAY to high.

if you are refering to an isolator. then yes. you take a voltage sense wire to the battery. the alternator will run at over 15v. the isolator drops 0.6v to each output. the start will drop a little less since less current. but both batteries should be ok. measuring off the start battery will be a little safer. and house will charge a little lower voltage. best to get rid of isolators if people are still using them.

[Mainebristol]

I'm sure other more informed people will chime in, but another possibility is that your self regulating alternator has fried a diode. This happens rarely, but the result could be that it cannot put out its full voltage anymore. Just a thought.

[sailorboy1]

If you use an external alternator regulator and connect sense and ground wires to the batteries instead of the default of connecting at the engine the regulator will do a true charge of the batteries!

[travellerw]

Originally Posted by smac999

if you are refering to an isolator. then yes. you take a voltage sense wire to the battery. the alternator will run at over 15v. the isolator drops 0.6v to each output. the start will drop a little less since less current. but both batteries should be ok. measuring off the start battery will be a little safer. and house will charge a little lower voltage. best to get rid of isolators if people are still using them.

In the last 2 years I have never seen a system such as you describe. All the systems I have worked on have the start battery connected directly to the alternator and the combiner (which you call and isolator) connected between the alternator and house bank. In that setup, if the alternator rose to 15V, it would be putting 15V into the starter battery (lots of excess offgassing). Would be strange to have 2 isolators and voltage drops (one on the house batts and one on the starter batts). That would be a huge waste of power to heat! I'm sure those systems exist, but I haven't seen one yet.

Again.. Like you say.. The OP needs to provide a drawing of his system, otherwise we are working on complete speculation.

The word isolator and combiner are used pretty universally around here. The people working on them know what they are looking at once we open the hatches. As to "getting rid of diode isolators", not sure I agree. With loads of boats having high power solar arrays and secondary modes of charging (diesel gens) a diode isolator is fine, at least where we cruise. There are still TONS of diode based isolators in use and still being sold (hell I just seen one bought today). Actually in an LFP installation a diode can be beneficial as it keeps the voltage to 13.8V, but that is a whole different conversation..

In any case.. I would put a bet down the OP has a "Diode Isolator" in his charging circuit

[smac999]

Originally Posted by travellerw

In the last 2 years I have never seen a system such as you describe. All the systems I have worked on have the start battery connected directly to the alternator and the combiner (which you call and isolator) connected between the alternator and house bank. In that setup, if the alternator rose to 15V, it would be putting 15V into the starter battery (lots of excess offgassing). Would be strange to have 2 isolators and voltage drops (one on the house batts and one on the starter batts). That would be a huge waste of power to heat! I'm sure those systems exist, but I haven't seen one yet.

the diode isolators have 1 input and multiple outputs. designed for one direct from alt input. and battery banks out. if you feed the alt direct to the start battery. and then feed the start battery (same as alt at this point) to the input of a diode isolator. and then one output of the diode isolator to the house bank. then when the engine is off, and the house battery is draining, and 0.6v lower then the start battery. now you are draining the start battery through the isolator to the house battery. the start battery is charging the house battery. defeating it's entire purpose of isolating them. that is defiantly not how you wire them.

were where it says remove original wire
https://www.newmarpower.com/wp-conte...-165_-5-12.pdf

if are you going to use it wrongly. I would atleast wire the alt direct to the house bank. so the house bank hitting full voltage for faster charging. and the start battey is 0.6v less. and then then start battery can not drain. as the house would drain into the start battery.