Solar - please enlighten me!

Hi Robin
Does this mean that the solar controller supplied by the van manufacturer could have different cut in/ cut out voltages than those of the Plasmatronics regulator? If so, what are the implications of this please. If not then I need some help with an explanation :)

Cheers
TG

Hi TG

Yes thats a reasonable way to state the issue without getting to technical.

There are then several possible senarios , mainly

1/ both controllers are set the same and to low - batteries won't get fully
charged.

2/ Both are set the same and to high - batteries may be overcharged depending on type.

3/ The controllers are set to different outputs - In this case the lower one will be under utilized.


Many accessories in these low volumne markets just get purchased and installed by the supplier with the manufacturers default values - so I suggest one asks specifically questions like "What type chemistry does the battery you supply use and has the controller been set for it , also could you write that setting down in the products manual please "

The response will act as a guide to how the rest of the van should be checked out !

Robin - I've lifted the info below from Plasmatronics website. It would suggest to me the regulator on my portable panels is suitable for charging AGM batteries (?) The solar controller in my camper trailer was able to be set for different battery types so am assuming the new one in the van should be similar and will be set to AGM. If this is the case, can you see any problems with overcharging occurring?
If I've got this completely wrong (very likely!!) please feel free to set me straight!!

Cheers
TG

PR1210L 12 Volt 10 Amp Regulator
FOR SEALED OR GEL LEAD ACID BATTERIES
A simple two stage regulator for charging sealed or gel lead acid batteries from
photovoltaic panels.
SPECIFICATIONS
Boost Maximum 14.2 V
Boost Cut in 12.5 V
Float Maximum 14.0 V
Float Cut in 13.4 V
All voltages +/- 0.1 volts
Charge Current 10 A
The PR1210L is not adjustable.

Hi TG,

sorry for butting in, but I feel that the PR1210L isn't the best regulator for charging AGM batteries which have a boost charging requirement of 14.4 to 14.8V based on 25 degree ambient, with a temperature coefficient of -240mV/degree.
The boost voltage should be 'seen' by the battery for about 1~2 hours on a daily basis, if the SOC drops below 90% the night before.
But this controller has no brains so that it can't actually measure any time intervals/segments.
All it does is wait for the battery voltage to hit 14.2V briefly and then it goes straight to float.

For float charging, this controller cycles between 13.4 and 14V, averaging at 13.7V which is kind of ok, although still not perfect because of the lacking battery temperature compensation and the crude on/off regulation which is the most inefficient way of raising the SOC.

This regulator makes the battery work best, if it's not discharged too deeply, say 30~40%, because it can't supply the crucial 5~10% over-charge necessary to bring back a reasonably deeply discharged battery to 100% SOC.
A controller like this one shortens battery life by about 30 to 50% depending on a number of operating conditions.
So instead of 6 to 8 years your battery may last only 3 or 4.

For any other questions, just contact us through our profile.

cheers, Peter

Hi Tj Peter

I was going to say that the Plastronics 1210 is a pretty simple device , you can't go much wrong using it , agree with Peter that there are better items around , but suspect that the unit that comes with the van is probably a simpler device also and much the same as the 1210 so the 2 units , while not optimum will get along ok.

Hi Robin,

there's still hope that the OP's other regulator has better specs in which case the battery would benefit from it.
BTW, what's this Tj? Or did you mean to type TG? Just curious ;)

@TG,

it's good to have the choice of selecting battery type on the regulator.
But it's better to actually measure the voltage, and then decide which 'chemistry' to select.
That's for two reasons: number one is that a great majority of solar regulator manufacturers don't know much about batteries hence assign the wrong setpoints to the individual chemistries.
Number two is the inaccuracy of the built in voltage reference.
A reasonably accurate voltage reference with 1% accuracy can be 10 times more expensive than a reference with 4% accuracy.
But in a 12V environment, 4% is almost 0.5V which explains why the setpoints can be all over the place on some regulators.

So how do you select the right 'chemistry'?
First find out what your battery manufacturer's recommended charging end voltages are for the float and absorption stages.
Then you need to measure the battery voltage using a multimeter (even the cheap ones are reasonably accurate for this).
Battery should be fully charged in order to be able to measure the 'end' or setpoint voltages of the regulator.

cheers, Peter

Thank you all for your well considered replies. Although you left me behind a bit Peter I get the drift re 'smart' vs 'dumb' controllers. Given that the portable panels will only be deployed occasionally when the van is in shade or prolonged cloudy periods it seems that what I intend to do, whilst not the most efficient/smart etc etc will do a reasonable job. My main concern was that I'd be totally screwing up my house batteries and it appears that this will not be the case. Thanks all once again.

Cheers
TG

Hi Peter , yep TG

We type to fast sometimes , ( suspect you may not have meant -240mv/degree)

Love it when you sometimes see a voltage like 12.65 - measured with a Dick Smith special.

yep, how true Robin :)

you can safely ignore the '0' in my -240mV/degree typo lol.

I know, this rollover error of +/- 1 count in the LSD ...but it's only responsible for 0.05% inaccuracy @ 20V FS.

I've found the overall accuracy to be better than 1% on a $12 (from memory Ja.car) unit, which makes these suitable for the type of measurements we're concerned here.
But maybe I just struck it lucky with this unit as the individual accuracy figures could be spread over a broader range.

@Bucky,

very good point, mounting the solar regulator as close to the battery as possible for minimal voltage drop in this wire pair.

cheers, Peter