Solar Panel

m8

Just fitted a solar panel to the roof of my camper last week and all looks good.


It's a 100w panel wired to a regulator and then to the leasure battery(fused ).
But I did not expect it to charge the starter battery.

Using the camper the leasure battery shows usage but not the starter battery and as expected the leasure battery charges when driving but how is it charging the starter battery from the solar panel?


Anyone know how this works?

moodrater

m8 wrote: »

Just fitted a solar p anel to the roof of my camper last week and all looks good.


It's a 100w panel wired to a regulator and then to the leasure battery(fused ).
But I did not expect it to charge the starter battery.

Using the camper the leasure battery shows usage but not the starter battery and as expected the leasure battery charges when driving but how is it charging the starter battery from the solar panel?


Anyone know how this works?

Why do you think its charging the starter battery when the ignition is off the starter battery should be disconnected from the leisure battery by a relay so that it doesnt discharge. A good battery will hold voltage for months so you expect it to remain full.

If you mean that you want it to charge the starter battery you d have to add some diodes to the regulator output to separate the Batteries.

m8

The started battery had about 90% charge when I fitted the solar panel and the leasure battery was about 75%. After a few hours of sun both are 100% charged. (full to the brim)

When using the leasure battery it does not drain the starter battery as I know from use. But I was not expecting the Starter battery to get a charge when engine is off.


Just as if i have pluged it into the mains power all batteries charge.

moodrater

m8 wrote: »

The started battery had about 90% charge when I fitted the solar panel and the leasure battery was about 75%. After a few hours of sun both are 100% charged. (full to the brim)

When using the leasure battery it does not drain the starter battery as I know from use. But I was not expecting the Starter battery to get a charge when engine is off.


Just as if i have pluged it into the mains power all batteries charge.

Possibility 1:- solar panel is not charging the starting battery:
You can only vaguely estimate state of charge on a rested battery. If you had started the van or had the radio or lights on etc. within a few hours of measuring the starting battery it might have indicated 90%* then when rested the voltage would gradually recover and might indicate 100%*.

Possibility two:
If you have a mains charger that charges the starting battery then the solar panel may be charging the starter battery back through that.

However your coming up with those percentages zig unit etc. think at least +/- 10-20% those things are not accurate at all. They can be mile off under certain conditions. If the battery has been recently charged of discharged the state of charge will read high or low respectively. Also type of battery, discharge rate, depth of discharge, previous discharge rate, temperature are factors.

Average insolation for last week in dublin was 2.53kwh/m2/day which means that your solar panel flat mounted would have produced about 25Ah per day taking into account charging efficiency of the battery it would take two days for that panel to bring a 110Ah leisure battery from 75% to 100% charge.

m8

Your calculations are impressive but are based on certain assumptions which are incorrect.

The camper was parked up for 3 weeks and only started 3 days before I fitted the solar panel.

On the day I fitted the panel the camper was at rest for 3 days no power used. That’s where I got my settings. We had a full day of bright sun and I checked the following night and this is where I could see that both batteries had charged fully. This also happens when on 220v mains but the charger is not 12v so how would both batteries charge?

moodrater

m8 wrote: »

The camper was parked up for 3 weeks and only started 3 days before I fitted the solar panel.

Which excludes the possibility 1 above.

m8 wrote: »

This also happens when on 220v mains but the charger is not 12v so how would both batteries charge?[/COLOR]

There must be a charger batteries can't charge themselves.
Which leaves possibility 2 above as my best guess without seeing the setup.

m8 wrote: »

Your calculations are impressive but are based on certain assumptions which are incorrect.

Yes sorry I went off on a bit of a tangent I did a solar project at university. The biggest assumtion of course was assuming your in Ireland as even the brightest clearest thoretically possible day last week at Irish latitudes would be about 4kw/m2 on the horizontal.

Couldn't really help any further without some facts like what vehicle is it, what charge controller do you have, what solar regulator, a circuit diagram etc.

m8

Yes it has to be option2 and it's a nice supprise

tibia

On my camper, a relay in the charging unit connects the two batteries if the voltage of the leisure battery is above a certain level (or if the engine is running). This happens around 13.5-14V but I can't remember the actual figure. An LED on the panel indicates when they are linked. Perhaps this is what your's is doing.

So if the engine is started, the two batteries are linked straight away. If the charger is turned on, they are linked after the leisure battery voltage increases sufficiently.

There is also the consequence that the two batteries often remain linked for some time (several minutes) after the engine is stopped or the charger turned off. A moderate load on either will pull the voltage down quickly and the relay drops out. The current drawn by the engine glowplugs will cause it to drop out immediately if the key is turned.

Hope that helps.