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Old 24-09-2020, 02:02   #1
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Splitting solar power to 2 battery banks

What is the best way to split solar power to 2 battery banks?

I have 130 watts of solar panels fed into a


Votronic SR140 Duo Dig. Solar Laderegler 9A 12V

https://www.votronic.de/index.php/en...sr-140-duo-dig


which only has 1 output, what is the best way to split this between 2 (180 amp/hr)
battery banks?


I have a 3 way battery diode splitter


https://www.nauticgear.nl/bootaccess...uitgangen.html


through which I direct current from the engine alternator & wind generator, it splits to the Start battery & domestic bank 1 & Domestic bank 2 (the Fridge battery)

could I connect the solar up to this as well? and if so do I place the solar regulator before the input to to the diode splitter?
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Old 24-09-2020, 21:40   #2
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Re: Splitting solar power to 2 battery banks

step one, get rid of the piece of crap diode splitter from the last century

step 2 join your 2 house batteries.

step 3 connect the alt, solar, and wind to the house bank.

step 4. connect a blue sea acr between the house and start battery

step 5. get a better solar controller. that looks like a pwm
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Old 24-09-2020, 21:43   #3
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Re: Splitting solar power to 2 battery banks

The voltronic solar charger that you linked has the option to trickle charge a start battery as well as charge the house bank.
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Old 24-09-2020, 22:01   #4
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Re: Splitting solar power to 2 battery banks

Quote:
Originally Posted by admiral 31 View Post
...could I connect the solar up to this as well? and if so do I place the solar regulator before the input to to the diode splitter?
Short answer, yes. Solar panels -> solar regulator -> diode separator input -> batteries will work.

As noted, diode isolators are a bit out of favor because the cause voltage drop (and therefore power loss) but nevertheless it will work. If you have “normal” batteries (wet, add water or AGM) I would watch the battery voltage when solar charging. You may be able to compensate a bit for the diode isolator by setting the solar regulator to the “gel” setting; this will increase the output voltage about enough to compensate for the diode. If you did this I would monitor battery voltage very closely the first few cycles to make sure it is not too high.
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Old 24-09-2020, 22:48   #5
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Re: Splitting solar power to 2 battery banks

I agree with SMAC99, can't see the point of two house banks on a 31ft yacht. Join them together and they will be discharged to a much shallower depth and last longer.

I wouldn't worry about the engine start battery, that can go for weeks without a charge.

One of the nice things about a small yacht, is they are simple and I am a firm believer in the KISS approach.

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Old 25-09-2020, 07:15   #6
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Re: Splitting solar power to 2 battery banks

Gentlemen,

Thank you to you all for taking the time to reply,

For the moment I am going to add the solar power (after the solar regulator)to the diode splitter,

Then wire the start battery output on the solar to the start battery output on the diode splitter.
As some of you have stated, while this set up may not not be optimal, it will work.
Thank you again for your help, you have given me more options & taken away my uncertainty.



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Old 25-09-2020, 10:27   #7
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Re: Splitting solar power to 2 battery banks

EPever DuoRacer MPPT Solar Charger and Discharger Controller, designed for two banks, is available in 10A. 20A and 30A versions.
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Old 25-09-2020, 14:42   #8
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Re: Splitting solar power to 2 battery banks

Quote:
Originally Posted by smac999 View Post
step one, get rid of the piece of crap diode splitter from the last century

step 2 join your 2 house batteries.

step 3 connect the alt, solar, and wind to the house bank.

step 4. connect a blue sea Blue Seas acr between the house and start battery

step 5. get a better solar controller. that looks like a pwm
What smac99 states above.

The diode splitter will knock .7 volts off the probable 14.4 volts the solar controller outputs. That means the batteries receive 13.7 volts max. I know of no lead/acid batteries that are happy at 13.7 volts bulk/absorption voltage. The batteries will have a shortened life at that voltage.

Blue Seas or Victron Cyrix combiner is your best bet.
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Old 25-09-2020, 15:18   #9
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Re: Splitting solar power to 2 battery banks

Quote:
Originally Posted by mitiempo View Post
What smac99 states above.

The diode splitter will knock .7 volts off the probable 14.4 volts the solar controller outputs. That means the batteries receive 13.7 volts max. I know of no lead/acid batteries that are happy at 13.7 volts bulk/absorption voltage. The batteries will have a shortened life at that voltage.

Blue Seas or Victron Cyrix combiner is your best bet.
This is an often cited item about diode splitters that isn't complete. Power diodes like those used in a splitter don't have a fixed voltage drop. Here's a sample diagram of a typical 80A-rated power diode, which is likely something similar to what is in the OP's high power splitter:
Click image for larger version

Name:	Diode Drop.PNG
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ID:	224191

At the maximum output (9A) of the controller/panel configuration proposed the typical drop is in the range of 0.3V rather than 0.7V. That's about 2% loss through the diode. Not great, but also not a deal breaker. Even with an alternator charging as the battery approaches full the voltage drop will fall as the current falls and it becomes possible to reach the desired charging voltage at the battery terminals by setting the charge source to compensate (or use a sense wire to the battery if so equipped).

I wouldn't put a diode isolator/splitter in a new system I was building, but where one exists I don't see it as a reason to run off to the store as long as you understand the ramifications. The OP's existing solar controller has settings that allow a bulk/absorption voltage as high as 14.8V, so if he has batteries that require 14.4V it is easy enough to adjust for the existing solar controller through the existing diode without having to break the bank. Only if the batteries (not specified by the OP) require a charging voltage at the higher end will he not be able to compensate.
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Old 25-09-2020, 15:52   #10
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Re: Splitting solar power to 2 battery banks

Quote:
Originally Posted by Dsanduril View Post
This is an often cited item about diode splitters that isn't complete. Power diodes like those used in a splitter don't have a fixed voltage drop. Here's a sample diagram of a typical 80A-rated power diode, which is likely something similar to what is in the OP's high power splitter:
Attachment 224191

At the maximum output (9A) of the controller/panel configuration proposed the typical drop is in the range of 0.3V rather than 0.7V. That's about 2% loss through the diode. Not great, but also not a deal breaker. Even with an alternator charging as the battery approaches full the voltage drop will fall as the current falls and it becomes possible to reach the desired charging voltage at the battery terminals by setting the charge source to compensate (or use a sense wire to the battery if so equipped).

I wouldn't put a diode isolator/splitter in a new system I was building, but where one exists I don't see it as a reason to run off to the store as long as you understand the ramifications. The OP's existing solar controller has settings that allow a bulk/absorption voltage as high as 14.8V, so if he has batteries that require 14.4V it is easy enough to adjust for the existing solar controller through the existing diode without having to break the bank. Only if the batteries (not specified by the OP) require a charging voltage at the higher end will he not be able to compensate.
The link the op provided for the diode splitter states it is lossless actually. We know there is loss whatever amount. With specs like that I wouldn't trust it.
I would replace it with a Victron 120 amp Cyrix which retails for $70 Cdn. A small price to pay for ensuring good battery charging.
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Old 26-09-2020, 02:44   #11
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Re: Splitting solar power to 2 battery banks

The start battery is a 65 amp starter battery & the house batteries are 2x 180 amp leisure batteries, all are normal sealed lead acid batteries, & not the gel type.


The diode 'no loss' splitter see diagram below
Attached Thumbnails
Click image for larger version

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ID:	224210   Click image for larger version

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ID:	224213  

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