solar split charge question

[contessaman]

Hi folks,

Im going to fit a 60 watt solar panel and 'off the shelf' (or off ebay) regulator to my boat. Can I connect the panel to the regulator, then the regulator via diodes to two seperate battery banks? or will the voltage drop of the diode fool the regulator into not charging the battery up to full?

would I be better of splitting the output of the panel with diodes (where there is plenty of surplus voltage) and then driving 2 seperate regulators, one for each battery bank.

I thought I was pretty good with electronics but I cant work this one out!

Help please!!

 

[halcyon]

would I be better of splitting the output of the panel with diodes (where there is plenty of surplus voltage) and then driving 2 seperate regulators, one for each battery bank.

Connect the regulator to one battery, then use a small cheap VSR from Ebay to charge the second battery, though it may depend on what voltage the regulator works at.

Brian

 

[VicS]

Diodes in the regulator output will result in under-charging

The obvious solution is to use a regulator with two ouputs. One for each battery eg http://www.google.co.uk/products/ca...=VbrsTtznCo23hAf4g-3BCA&sqi=2&ved=0CHMQ8wIwAA

or http://www.marlec.co.uk/wp-content/uploads/2008/09/morningstar-sunsaver-duo-datasheet.pdf

Do you really need solar charging of both battery banks?

EDit ... use VSR as Brian suggests !

 

[VicMallows]

If you are on board while using the panel, I would advise not bothering about a regulator at all. If you don't have one already invest in a charge monitor (the nasa BM-1 is fine IMHO) and simply manage the solar charge manually.

Most of the (£12 ish) EBAY ones are intended for solar powered street lights with predictable discharge/recharge characteristics. In a boat environment they reduce the charge to 'float' level (13.8v) far too soon on a time-based algorithm. (they are fine though as basic voltage regulators to simply maintain the batteries when boat unattended.).

Vic

 

[pappaecho]

If you use a cheap Maplin charge controller, which costs about £10, it has two outputs, and charges all or one dependant on the relative voltages of the two banks.

To buy a controller and then involve diodes in addition will result in voltage drop and I suspect wallet drop as well!

I have an 80 watt panel via the Maplin unit and it works perfectly.

Quite separately I have a diode splitter for the alternator ouputs to the battery banks, which allows charging of batteries from the engines, or engine

 

[Paul_R]

Are the two banks a domestic and engine bank? If so there's little point making extra provision to charge the engine bank unless you have very atypical engine usage for a cruising boat and have evidence that there's a problem maintaining the level of charge in the engine bank. Save your money and charge the domestic bank only. If you do want to fit a VSR then you should remember that the relay will require a current to hold it on - negligible with respect to alternator output but possibly not in comparison with a solar panel in marginal conditions. Also your VSR will activate whatever the charge source. You need to consider it as part of your overall system.

 

[contessaman]

Are the two banks a domestic and engine bank? If so there's little point making extra provision to charge the engine bank unless you have very atypical engine usage for a cruising boat and have evidence that there's a problem maintaining the level of charge in the engine bank. Save your money and charge the domestic bank only. If you do want to fit a VSR then you should remember that the relay will require a current to hold it on - negligible with respect to alternator output but possibly not in comparison with a solar panel in marginal conditions. Also your VSR will activate whatever the charge source. You need to consider it as part of your overall system.

Your assumptions are correct with respect to domestic and starter banks. the reason I was thinking of a charge output to the starter bank is for maintenance charge - due to the nature of my work it can be weeks or even months that the boat is left. perhaps a better approach will be a second (much smaller) solar panel for the starter bank?????

 

[Stu Jackson]

You might be interested in Reply #4 here about solar panel regulators: http://forums.catalina.sailboatowners.com/showthread.php?t=136421

Beware eBay for that stuff.

Diodes are so way old technology. They kill voltage just when you need it the most. Why not go the VSR route with one panel and one good controller and be done with it?

 

[William_H]

Diodes

Yes diodes after the regulator will reduce the regulated voltage so not charge the batteries much.
Yes diodes before 2 regulators will work well. Indeed many solar panels have a built in diode for stopping discharge at night. If you find this diode and fit another in the same way from panel positive to another outlet wire you will have no more voltage drop than the panel with one diode. However voltage is not usually a concern as the panel produces around 20 volts open circuit.
Of course if you have large battery bank and not much sun (or poor alignment of the panel to the sun)(ie flat panel or swing mooring) you might be OK with 2 diodes and no regulator. A bit of a risk of overcharging in summer. Or find a regulator with 2 outputs.Probably 2 diodes at output but with regulator voltage raised to cope with diode drop. good luck olewill

 

[Stu Jackson]

The Shottkey diode for solar panels is, as you say, before the controller. The OP did say he was thinking about putting them after the controller. Good explanation, thanks,