Did not know what i was doing in 2020 Batteries and solar

[Rhylsailer99]

I have 2 leisure batteries 130ah each and I fitted a 20w solar panel to trickle charge one battery, then at a later date I fitted another 20w solar panel with a seperate controller. Both conttrollers are independant charging one battery each. Would it be better to have one larger panel with a dual output from the controller? I alao think the batteriea will need replacing next year, as the voltage drops to 11.6v when under load. I also have an issue the alternator not kicking in on a sunny day because of the solar volts. I also have a switch with 1,2,both for selecting which batteriy to use

I was thinking to uograde to 2x 120ah agm batteries next year, and a bigher pabel, as looking to get a small fridge.
My 2 current silar controllers are the very cheap chinese ones

 

[Supertramp]

If it works, leave it alone.

However if Chinese controllers worry you then replace with Victron or similar. Not sure how your system works as presumably the batteries are linked and having two controllers for a linked battery system doesn't feel right.

I have two linked SLA batteries with one panel and controller. I added an isolation switch as per Victron circuit diagrams so I can isolate solar if I want when on engine or shorepower. Also wise if working on electrics.

The voltage drop on load doesn't mean much without the context - current load, state of charge. My batteries are 5 years old and rest at 12.8 V, fully charged, dropping to 12.3 or4 under 5 to 10 amps load. At 80% SOC the same load gives 12.2 or 3. You need a chart showing voltage at different loads and state of charge. I keep a laminate one by my battery monitor so I can keep an eye on things.

Something like this



This may help explain.

SLA battery under load: Is the absolute voltage or the state of charge primary for wear avoidance?

Obviously replace batteries if their fully charged voltage is low, and if they drop excessively under load. Being a fan of simplicity I'm comfortable with SLA kept well charged but it depends on your usage pattern.

 

[Tranona]

Lots of questions and decisions there. If replacing batteries suggest you ditch the current system and fit separate start battery and service bank independently switched and a split charge from the alternator. You can keep the existing solar to charge the service bank - no need to connect to the start battery as that is usually fully charged from the alternator. 20W won't run a fridge, but will be useful to top up when you are not using the boat. 2*120ah is pretty generous for a boat like yours and a simple car battery of around 60ah is fine to start the engine. Increasing solar will of course reduce your deficit when sailing.

This is roughly the setup I have just installed except for space reasons there are 2*95ah service and a high powred start AGM. Switching and split charging using a BEP Marine switch cluster which also has a parallel switch so you can start the engine from the service bank in an emergency. bepmarine.com/en/p/716-SQ-140A-DVSR/Square-Btery-Distribution-Cluster

 

[William_H]

OP system of 2 separate solar panels for separate batteries I think is pretty ideal for battery maintenance over period of no activity. The batteries may be simply dieing of old age. A bigger panel will if it exceeds the capacity of the 2 smaller ones will do more charge and a controller with 2 outputs will charge both batterie while remaining isolated from one another. But no not suggested as a way to go.
I suggest he continue using the batteries and 1,2,b switch until he finds they won't do the job he wants them to do. If battery replacement is necessary as said a dedicated engine start battery will be cheaper to buy. This may enable old batteries to continue in use as service batteries or replace one or both depending on the capacity he wants. Fit a VSR and individual isolation switches. ol'will

 

[B27]

I have 2 leisure batteries 130ah each and I fitted a 20w solar panel to trickle charge one battery, then at a later date I fitted another 20w solar panel with a seperate controller. Both conttrollers are independant charging one battery each. Would it be better to have one larger panel with a dual output from the controller? I alao think the batteriea will need replacing next year, as the voltage drops to 11.6v when under load. I also have an issue the alternator not kicking in on a sunny day because of the solar volts. I also have a switch with 1,2,both for selecting which batteriy to use

I was thinking to uograde to 2x 120ah agm batteries next year, and a bigher pabel, as looking to get a small fridge.
My 2 current silar controllers are the very cheap chinese ones

If your 'voltage' is dropping to 11.6 under fairly small loads, then I would suggest checking out wiring, checking the battery is actually getting fully charged etc.
Measuring the volts at battery and load can reveal some wiring drops.
I've never noticed an alternator not kicking in due to solar voltage, what kind of alternator? Simple car type? Outboard motor type? Fancy regulator?

It's possible to run a fridge with a very basic system.
It's possible to spend a fair bit on 'better' regulators and switchgear and all that, so it's up to the individual to work out the cost/benefit.

I find a single 50W panel is effective in Summer. Simply because I mount it on an aerial post at the stern.

My fridge is a generic 12V compressor coolbox, about £200 on ebay. It averages about an amp, so if you have some solar and some motoring a single battery can keep the fridge running. A 50W panel mounted horizontal unshaded is very effective at keeping up with the fridge, but much as I prefer to sail rather than motor, there's generally enough engine time to cope with the consumption.

My boat has more voltage drop than I'd like, 30 year old wiring intended for the basics. The fridge pulls 3 to 5A when the compressor is running, so it's good to have reasonable wiring.

I don't really trust the cheap solar controllers, never sure what they'll be doing when the boat's not used, so I don't leave them connected permanently, but I'm able to visit my boat often and check the batteries.

 

[Rhylsailer99]

My boat was all re wired with heavy gauge marine grade wires and the alternator is only 2 years old on a Bukh dv20. In the bright sunlight my voltmeter was reading 13.4v and when I started the engine it never changed. I was expecting the volts to go higher as the alternator kicked in. I did some googling and found that an alternator wont kick in if the volts are high already.

 

[geem]

My boat was all re wired with heavy gauge marine grade wires and the alternator is only 2 years old on a Bukh dv20. In the bright sunlight my voltmeter was reading 13.4v and when I started the engine it never changed. I was expecting the volts to go higher as the alternator kicked in. I did some googling and found that an alternator wont kick in if the volts are high already.

If the set point of your alternator is 14v, the alternator will start charging if the batteries are lower that 14v. It may be worth checking the voltage at the battery. It may be that the battery is more charged than you think

 

[B27]

... I did some googling and found that an alternator wont kick in if the volts are high already.

Google can find you all kinds of stuff that's wrong!
A normal basic alternator will output 14V to 14.4V, all it needs is the charge light current to start it.
Starting the engine will normally drop the battery volts for at least a few seconds after you stop cranking anyway.

If your alternator doesn't bring the volts up from 13 point whatever to something over 14, it needs looking at.

Smart chargers and 'smart' alternators which see a battery at >13.5 because another source is trickle charging it can be fooled into thinking the battery is fully charged.

As Geem says, check the voltage at the battery.
I'd add check it at the alternator too.

Just because your wiring is only two years old, it's not above suspicion.

Also look for differences in 'ground' voltages.

Be methodical, check everything, including the things you think you can trust.

 

[Rhylsailer99]

Because I replaced my alternator just over a year back, could that have been a smart alternator?

 

[Rhylsailer99]

After opening up my switch board I noticed the voltage go from 11.6 to 12.7v, something was loose. After a lot of poking about I found the loose connections, and now my alternator is reading 14v after a few mins running. When I re wired I copied what was there previous but with better components, I now see mistakes made, ie my alternator wires are not big enough and need a more direct route to the batteries being charged.