Yet Another Solar Panel Question;-)

[Dougal]

Well, two questions actually…

Apart from the alternator, my other two chargers are a 240v 30Amp 3 stage charger, and a 120W solar panel with charge controller.

When using the mains charger, once the batteries are fully charged, the battery voltage settles to about 13.2volts. I would suggest this is on the low side, but not sure?

With the charger switched off, utilising only the S/P, the voltage never seems to drop below 14.6volts. Surely this is too high???

Both systems are adjustable, but not by much.

What does my ‘on call’ expert panel think??? ;-)

Also, I currently have no switch to disconnect the S/P from the batteries. Should there be one?

Cheers guys n gals

EDIT: All batteries Flooded cell.

 

[VicS]

Not sure what you mean by settles to about 13.2 volts. Presumably thats the float voltage maintained by the charger. Depends on the charger and if settleable what type of battery its set for. Check with charger documentation.

14.6 is a little high but I guess depends on the controller and type of battery its set up for, Check with the documentation.

Would not normally expect a switch to disconnect the SP. ( If you fit one it may have to go between panel and controller rather than between controller and battery.. Depends on the controller.)

 

[macd]

Dougal: you don't say when and in what context the solar keeps showing 14.6V. In your neck(s) of the woods, it may well be that a 120W panel never quite fully charges the batteries, and is thus held in high voltage boost mode. Much would depend on what the battery bank's state of charge is when the sun gets high enough to deliver significant power, and the loads on the batteries whilst it's charging.

Plus, as Vic implies, it never does any harm to double-check the manual.

By flooded cell batteries, I presume you mean 'open' or top-uppable. Are you having to do much topping-up? The total Ah of the bank might also be helpful to know.

 

[Dougal]

Many thanks guys and sorry for lacking info... Here's the full SP;-)
Engine Battery: 95Ah Wet & Fill-able (3 years old and showing as excellent condition on hydrometer and built-in 'green marks')
Domestic Batts: 180Ah (2 x 90) Wet & Fill-able (as above)

Been on the boat 2 weeks now in Brittany and, until yesterday, had battery charger running 24/7. I have VERY little info on the charger. Its a Reya 299540 40A, built for the OEM market (only manual being a single page downloaded from the Dolphin website). So the batteries are as charged as they'll ever get. The unit is set to mode 00, which it states is for 'wet cell batteries'. The info I can't find, is at what setting supplies what voltages etc. It's listed as being a 'multi-stage' charger, but i haven't found anything more:-(
This was the point I hooked up the S/P into the system, so surely a 120W would have no trouble there; the batteries already being fully charged?
I have topped up the engine battery just ONCE since purchase, the domestics, never!

Tonight, I'll disconnect all charging and measure battery voltages tomorrow at rest.

 

[Dougal]

After resting batteries for a day, they read about 12.6 volts after being fully charged by mains charger.

However, if I connect the solar panel with full sun, the battery voltage still rockets to 14.6 volts!

 

[VicS]

After resting batteries for a day, they read about 12.6 volts after being fully charged by mains charger.

However, if I connect the solar panel with full sun, the battery voltage still rockets to 14.6 volts!

12.6 volts....... OK but might have hoped for 12.7 or a little more. ( There's a 10 year old car starter battery on my bench at the moment. It was last on charge yesterday. with one of the Lidl 3.8 amp chargers. It now reads 12.71 volts)

I guess your solar controller is set for 14.6 volts. Almost as soon as you connect the battery to the solar system the volts will whizz up to 14.6. Id have expected it to control a little lower. 14.4 perhaps. You dont say what make / type the solar regulator is.

 

[macd]

After resting batteries for a day, they read about 12.6 volts after being fully charged by mains charger.

However, if I connect the solar panel with full sun, the battery voltage still rockets to 14.6 volts!

I have topped up the engine battery just ONCE since purchase, the domestics, never!

12.6 is a little low for a fully charged battery (assuming there was no drain while it was resting). What does your hydrometer tell you?
As before, my suspicion is that the solar regulator is seeing a battery bank not quite at 100% charged so is going to boost mode somewhere in the final 10% or so. It's probably putting in very few amps whilst at 14.6V: do you have a reading of this?

Regarding topping-up, I'd normally expect it to be the other way round. Starter batteries (assuming a good engine) get a doddle of an existence, and rarely need topping up. Domestics get 16 hours at t'mill and much more of a thirst. By my reading, this tends to support the notion that your domestics perhaps aren't reaching 100%. If they're not gassing, they're not getting fully charged.

 

[Dougal]

12.6 is a little low for a fully charged battery (assuming there was no drain while it was resting). What does your hydrometer tell you?
As before, my suspicion is that the solar regulator is seeing a battery bank not quite at 100% charged so is going to boost mode somewhere in the final 10% or so. It's probably putting in very few amps whilst at 14.6V: do you have a reading of this?

Regarding topping-up, I'd normally expect it to be the other way round. Starter batteries (assuming a good engine) get a doddle of an existence, and rarely need topping up. Domestics get 16 hours at t'mill and much more of a thirst. By my reading, this tends to support the notion that your domestics perhaps aren't reaching 100%. If they're not gassing, they're not getting fully charged.

Thanks Mac
I've never seen much evidence of gassing, nor had to ever top off much, even with the previous (old) set of batteries. Not even after one haul of 15hrs of motoring.
Can't remember the numbers off the hydrometer (never thought them to be that accurate or calibrated), but all three batteries were well into the green zone. I'm inclined to agree about maybe not reaching 100%, but running out of ideas how to reach that figure, if even the mains charger wont get them there:-(

 

[macd]

Can't remember the numbers off the hydrometer (never thought them to be that accurate or calibrated), but all three batteries were well into the green zone. I'm inclined to agree about maybe not reaching 100%, but running out of ideas how to reach that figure, if even the mains charger wont get them there:-(

It's worth keeping a log of the hydrometer readings (well, if you want to become battery-obsessive like some of us...). Even if not totally accurate, it will identify any trends, and tell you when they need equalizing.

What you write also begs the question of whether your charger is truly fit for purpose. Lead acid batteries love being 100% charged from time to time. They can get sulky if not fully fed.

 

[PaulRainbow]

For flooded, not sealed, batteries :

Float charge should be 13.2 to 13.5 volts.
Bulk charge should be 14.4 to 14.8 volts.
There should be no excessive gassing.

I agree that the solar controller is correctly identifying the batteries as needing charge and applying a 14.6 bulk charge, but due to insufficient amps is unable to fully charge them.

I doubt the mains charger is fit for purpose.

 

[VicS]

I too wonder about the charger.

You quote 13.2 as the voltage to which the batteries settle but this is presumably when the batteries are charged and is the "float" voltage.

What is more important is the voltage it reaches during the "bulk" and "absorption" stages If you start with a partially discharged battery I'd expect to see the volts steadily rise during the constant current bulk charging stage until they reach 14.6. Then I'd expect to see a constant voltage absorption stage during which this voltage is maintained as the battery approaches its fully charged state and the current falls. Finally I'd expect to see the float stage at the 13.2 volts you have mentioned.

One day when watching paint drying seems like an exciting thing to do partly discharge your batteries and then monitor the charging. If you see something resembling the above, reaching 14.6 volts at some point, then all should be well with the charger. If OTOH it never, at any point, goes above 13.2 then it is not effectively charging the battery.

The behaviour when the solar charger is connected suggests that in reality all is well with the Reya charger and that it is in fact properly charging the batteries.

 

[sarabande]

No switch on the solar panel ? if you had one and switched it OFF, some panels can overheat unless you cover the face.

Is the SP fused on the positive side BTW ?

 

[William_H]

No switch on the solar panel ? if you had one and switched it OFF, some panels can overheat unless you cover the face.
?

Where did that come from? I have never heard of that idea that a solar panel can overheat from being disconnected.
Yes they can get hot in the sun but that is regardless of current drain.
Re OP problem. For the cost it might be worth buying or borrowing another volt meter. Digital multimeter can go inaccurate (read high) when battery gets low or can just lose or never had correct calibration. If battery is good
but meter reads high on chep meters you can often find a tiny potentiometer on the board. Turned by a tiny philips head screw driver which will change the calibration of all ranges at once. olewill

 

[ex-Gladys]

Where did that come from? I have never heard of that idea that a solar panel can overheat from being disconnected.
Yes they can get hot in the sun but that is regardless of current drain.
Re OP problem. For the cost it might be worth buying or borrowing another volt meter. Digital multimeter can go inaccurate (read high) when battery gets low or can just lose or never had correct calibration. If battery is good
but meter reads high on chep meters you can often find a tiny potentiometer on the board. Turned by a tiny philips head screw driver which will change the calibration of all ranges at once. olewill

When I installed my Solara panels the instructions were explicit to keep the panels covered until the connections to the controller were complete...

 

[William_H]

When I installed my Solara panels the instructions were explicit to keep the panels covered until the connections to the controller were complete...

Ah they were I think more concerned about your safety in the process of wiring up. Even then very cautious.
I think with all controllers when the battery is fully charged they in effect stop taking power from the panel ie no load or equivalent of disconnect. olewill

 

[VicS]

No switch on the solar panel ? if you had one and switched it OFF, some panels can overheat unless you cover the face.

If this was so simple on/off controllers would be a problem

 

[ex-Gladys]

Ah they were I think more concerned about your safety in the process of wiring up. Even then very cautious.
I think with all controllers when the battery is fully charged they in effect stop taking power from the panel ie no load or equivalent of disconnect. olewill

Nope, "may affect the longevity of the panel" or words to that effect.

 

[Dougal]

As ever guys, I seriously appreciate all the amazing feedback I get here. I just wish that MY 'absorption rate' was as good as the batteries!!!

Slowly, slowly the info seeps in by osmosis though;-)

Another question on the subject while I'm here... Why are solar panels factory fitted with such hoofin cables? According to the spec on my 120w panel, the max amp output is just under 7, yet the darn thing is fitted with 4mmSq leads! Do they assume the cable runs will be huuuuuge?

 

[Dougal]

...and while I'm on a roll... another if I may be so bold;-)
When ONLY the charger is running, and has been charging for a while, it DOES appear to be putting out the correct (listed) 'float' charge voltage of 13.2v
Prior to reaching float, the voltage now shows 14.4 which again, is the correct (listed) voltage.

This charger has a common ground and three outputs, marked as +DC1, +DC2 & +DC3 and the manual states:
'It is essential that +DC1 is connected to the Main Battery'
'Please connect +DC2 and +DC3 to the motor battery and the aux battery respectively'
How do you guys interpret that? I only have only two battery banks; a single engine starter (connected to +DC1) and two parallel domestics (to +DC2). Is this how you would run it?

I've tried contacting the manufacturer and distributor, but all I get is standard responses (in French) that are about as clear as mud!

 

[Poecheng]

Hi Phil,

I think the "main battery" for DC1 is what you describe as your "two parallel domestics"
DC2 for the "motor battery" is your "single engine starter"
DC3 for "aux battery" - you do not have one.

Therefore to accord with the manufacturers instructions you need to swap the leads over on DC1 and DC2. They want the main load going out on DC1 which is the load going to your two domestic batteries. Also (depending on the program) it is probably DC1 which senses what is needed. None of these two or three output chargers sense the individual outputs - it senses once and then the output is shared by the outputs (here DC1, DC2 and DC3 if connected)

At the moment it may well be just sensing the starter battery through DC1 and therefore, once that is OK (and it will be most of the time), the charger will "slow down" when, in fact, the domestics still need lots of work on them !