Split diode

[Mr Cassandra]

I have bought a new 120 AH split diode, I have two 150 w solar panels said to give 8 ah each. Could I wire the + from panels director to the centre pole of the diode and the - to the battery pole? Would the diode act as a regulator as my Fox220 regulator has failed.

 

[VicS]

I have bought a new 120 AH split diode, I have two 150 w solar panels said to give 8 ah each. Could I wire the + from panels director to the centre pole of the diode and the - to the battery pole? Would the diode act as a regulator as my Fox220 regulator has failed.

To clarify what you mean

You have bought a 120 amp diode splitter ??
and
You have two 150 watt solar panels said to give 8 amps each ?

The purpose of a diode splitter is to charge two batteries simultaneously from the same source , usually the alternator. Yours could handle the output from a 120 amp alternator ... that's quite a large alternator.

No your diode splitter will not function as a regulator for your solar panels!

 

[PaulRainbow]

300w of solar power absolutely must go through a controller.

I would not put solar panels through a diode. Your choices, IMO, are :

a) Fit a dual sensing VSR instead of the diode, connect the alternator to the engine battery and the solar controller to the domestic bank.

b) Fit the diode to the alternator output and connect the solar controller directly to the domestic bank. This means your solar power won't charge the engine battery, but unless you leave the boat unattended for long periods that won't matter.

I'd prefer option a.

 

[JanZ]

The bluesolar duo (no connection with bluesolar!) will charge both sets of batteries with progammable amounts of charge to both domestic and engine batteries. Uses PWM rather than MPPT technology but is cheaper and works for me.

Jan

 

[William_H]

Leave the isolation dioded as is serving the alternator out put. Just buy 2 cheap PWM solar regulators and connect to each battery individually. Or just one regulator to big house battery and possibly buy a small solar panel 10w connected directly to the engine battery. good luck olewill

 

[Mr Cassandra]

Hi
I have to ask why? The alternator gives out amps 10,20 30 40 60 whatever,its connected to the centre pole of the diode this is then split to charge the house or starter batteries .
Why cannot I connect my solar panel bank ,said to give 15a direct to he center pole of the diode ?via a single battery fox 200 regulator.
I did it once before on another boat and it "appeared" to work...

Not looking for an argument just advice.

 

[AntarcticPilot]

Hi
I have to ask why? The alternator gives out amps 10,20 30 40 60 whatever,its connected to the centre pole of the diode this is then split to charge the house or starter batteries .
Why cannot I connect my solar panel bank ,said to give 15a direct to he center pole of the diode ?via a single battery fox 200 regulator.
I did it once before on another boat and it "appeared" to work...

Not looking for an argument just advice.

I'm no expert on this, but surely it's because the VOLTAGE from a solar panel can exceed the maximum charging voltage for a battery? A 12V nominal solar panel can easily produce 20V on a sunny day - way above the 14.5V usually recommended as a maximum charging voltage. A diode won't affect that at all - a diode is simply a one-way valve in an electrical circuit. Solar controllers are used to regulate the voltage supplied to the battery, and to provide battery-friendly charging regimes.

 

[GrahamM376]

Hi
I have to ask why? The alternator gives out amps 10,20 30 40 60 whatever,its connected to the centre pole of the diode this is then split to charge the house or starter batteries .
Why cannot I connect my solar panel bank ,said to give 15a direct to he center pole of the diode ?via a single battery fox 200 regulator.
I did it once before on another boat and it "appeared" to work...Not looking for an argument just advice.

That's not what you said in your original post, you said your regulator is bust. If you want to charge 2 banks then put the diode between the solar panels and 2 regulators, 1 to each battery or, get a dual output regulator. If you put split charge diode after one regulator then it won't work properly.

 

[dk]

The only reason you wouldn't put the output from the solar charge controller through the diode splitter is that the diodes have quite a high resistance, which will considerably reduce the amount of charge getting to the batteries from your PV panels. The output should go directly to the leisure bank and ideally you'd fit a dual-sensing VSR between the starter and leisure batteries so that once either reaches a preset voltage (usually 13.8V) they are paralleled together for charging.

 

[Mr Cassandra]

Okay let me try again.I have now got two solar panels, one 150w the other 100w. I think these will give around 12A total. I have now got a regulator which is rated at 20 A which came with the larger panel.
I havel connected both panel to the one regulator without load there is around 20 v. I have the regulator connected to 2 180A batteries with nothing charging the 120a starter battery.
Output from the regulator is 15 v and I presume 12A. If I connect the positive to the centre pole on the diode will it not charge both batteries?

 

[john_morris_uk]

The only reason you wouldn't put the output from the solar charge controller through the diode splitter is that the diodes have quite a high resistance, which will considerably reduce the amount of charge getting to the batteries from your PV panels. The output should go directly to the leisure bank and ideally you'd fit a dual-sensing VSR between the starter and leisure batteries so that once either reaches a preset voltage (usually 13.8V) they are paralleled together for charging.

Its innacurate to say the diodes have ‘quite a high resistance’. There’s a voltage drop inherent with the semiconductor junction but it can be as little as small fraction of a volt with certain specialist diodes up to over 0.7 volts for a silicon PN junction. It’s not a ‘straightforward resistance’ that obeys ohms law when a diode is forward or reversed biased.

 

[GrahamM376]

If I connect the positive to the centre pole on the diode will it not charge both batteries?

Maybe this will answer your question - I have 2 banks, each 240AH and initially I had 2 regulators, one to each bank, but found both banks to be balanced by morning as there was reverse flow through the regs. I then tried one regulator into a split charge diode I had lying around and this reduced the charge drastically. Seemed to be by more than just the expected 0.5 (or thereabouts) volt drop I had been expecting and I suspect that with the diode, the regulator wasn't sensing the batteries properly - others more knowledgeable may have thoughts on this point. I then put the diode in the feed from the panels and fed that into two regulators and charge rate increased to "normal". The slight voltage drop from the panels to the regs. made little difference.

Edit - I also have a separate engine battery but not charged from those regs. or panels.

 

[dk]

Its innacurate to say the diodes have ‘quite a high resistance’. There’s a voltage drop inherent with the semiconductor junction but it can be as little as small fraction of a volt with certain specialist diodes up to over 0.7 volts for a silicon PN junction. It’s not a ‘straightforward resistance’ that obeys ohms law when a diode is forward or reversed biased.

Just trying to keep things simple!

 

[Mr Cassandra]

Thanks all ,I was trying to find a simple way to trickle charge over winter without dedicating a panel,and controller for the starter battery.

 

[VicS]

Thanks all ,I was trying to find a simple way to trickle charge over winter without dedicating a panel,and controller for the starter battery.

Now that you have a replacement regulator ....... something you did not admit to at the time of your first post ...... yes you can connect both panels to it and perhaps connect its output to the diode splitter

BUT there will be a voltage drop across the splitter of around 0.7 volts which will reduce the effectiveness of the charging.

ALSO the diode splitter will prevent the regulator sensing the system voltage. It depends on what regulator you have. It may or may not work !

 

[Mr Cassandra]

Hi
Its a very cloudy here in Greece today and I am getting 13.4v input side of the controller and 13v on the output side this is then connected direct to house battery bank.

Quote
ALSO the diode splitter will prevent the regulator sensing the system voltage. It depends on what regulator you have. It may or may not work

What I am concerned about having read the above, will it cook the batteries on a sunny day if going through the diode and controller /regulator does not adjust input.

Anyway it was worth a try. Thanks.

 

[VicS]

Hi
Its a very cloudy here in Greece today and I am getting 13.4v input side of the controller and 13v on the output side this is then connected direct to house battery bank.

Quote
ALSO the diode splitter will prevent the regulator sensing the system voltage. It depends on what regulator you have. It may or may not work

What I am concerned about having read the above, will it cook the batteries on a sunny day if going through the diode and controller /regulator does not adjust input.

Anyway it was worth a try. Thanks.

If the regulator is a dual voltage one ( ie 12 / 24 volts and the diode splitter prevents the regulator identifying the system volts, ie 12 or 24 volts, it will probably probably not produce any output

( I suspect , unless you tell me otherwise, this is what would have happened if you had tried to use your Fox 220 in conjunction with the diode splitter)

If your "new" regulator is a dedicated 12 volt one then it may work. ..... try it.