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Old 15-12-2019, 15:11   #1
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solar and a vsr

Hi all, just, I hope, a quick query, just cant get answer sraight in my head. I have 2x6 volt trojans wired in series charged purely by 200 watts of solar. I also have 90ah starting battery (lead acid) and 130 ah domestic agm battery which are charged/ maintained by the engine thru 1,2 both switch and small solar panels, one for each. The 200 watt solar system is purely to run my 12 volt fridge, and does this thru an mppt controller with lcd display, by lunchtime the batteries are fully charged and only minimum amps appear to be going into the batteries, unless the fridge cycles on. The excess being "dumped" I presume. I have thought of installing a vsr so that the excess amps can be funneled to the domestic battery. Where in the system would i install the vsr ?. I believe it should be between the solar batts and the mppt controller. thus when solar charged batts get to (say) 13.5 vollts the vsr energises and directs excess amps to the domestic battery. I can then use the larger of the two other small solar panels I think its only 50 watts to maintain the starter battery and use the tiny maintence solar charger on my touring kayak/Car etc. Would this set up damage the mppt controller in any way ? When the fridge cycles on and drops the the trojan voltage I assume the vsr will switch the system back so that the trojans again receive power from the solar panels. Thanks in advance Peter.
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Old 15-12-2019, 15:38   #2
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Re: solar and a vsr

Why do you have 2 different domestic batteries banks? How do you chsrge the golf carts from the engine ? Sounds like you can’t. And 3 different Panel systems??

Remove the 130ah battery and connect the wires to the golf carts. Connect all solar to golf carts.

Add vsr / acr. Between single house bank and engine bank. Pos post to post post. So the house will chstge from engine. And so the solar can make rain the engine. Though this should not be needed.
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Old 15-12-2019, 16:09   #3
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Re: solar and a vsr

I want the " golf carts" to remain separate and only charge from solar. With the Australian sun I have only needed to use the 12volt/240v adaptor twice in the past 5 years to run the fridge. It only draws 4-5 amps but cycles once per hour for 10 to 15 mins even on the height of summer. Just want to find a use for the excess power generation. I'm completely happy with current set up apart from the lead acid battery, its days are numbered and will be replaced with an agm once it's kaput. I
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Old 15-12-2019, 17:35   #4
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Re: solar and a vsr

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Originally Posted by Elevation View Post
I want the " golf carts" to remain separate and only charge from solar. With the Australian sun I have only needed to use the 12volt/240v adaptor twice in the past 5 years to run the fridge. It only draws 4-5 amps but cycles once per hour for 10 to 15 mins even on the height of summer. Just want to find a use for the excess power generation. I'm completely happy with current set up apart from the lead acid battery, its days are numbered and will be replaced with an agm once it's kaput. I
You can do whatever you want on your boat, but the current set-up is technically sub-optimal.

When the house bank is split, you are affected more by Peukert’s Law, which basically states the greater the load with respect to capacity, the less energy can be discharged.

The other issue is that one bank can be discharged, requiring the charger to be turned on, while the other bank is sitting idle, fully charged.

Lastly, when using 2 x 6Vdc batteries in series, if one goes bad, and you isolate it, you can’t use the other. Whereas if you had 2 x Grp 27 in parallel, under same conditions, you would still have a useable 12 Vdc bank.

So my recommendation would be to use 3 x 12 Vdc grp 27 in parallel, or if you had room for another battery, 4 x 6Vdc batteries, wired 2S2P.

Now, in response to your question, the best thing to do with excess energy production, is to store it (in a bigger bank) for the times you need it. If you never need your current total energy production, then you can add discretionary loads to utilize it. Many use excess solar, when available, to heat their water.

It is very tricky to automate a system to do this in ones absence, unless you have a battery monitor capable of switching on the water heater after the batteries are truly full, and switching off the heater, as soon as the solar can no longer meet the fridge demand.
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Old 15-12-2019, 19:22   #5
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Re: solar and a vsr

Yes the basic system design is flawed.

Simpler is better, less is more.

One big House bank, VSR goes from there to the Starter, ideally all charge sources go directly to House.

If not, make sure it's two-way, dual sensing type.
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Old 15-12-2019, 20:02   #6
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Re: solar and a vsr

Why is it on these forums no one answers the question as asked. You might think it flawed/ not what you would do, but it has worked faultlessly since installation some 6 years ago Don't know why I bothered asking for advice
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Old 15-12-2019, 20:08   #7
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Re: solar and a vsr

You need a regulator for each bank of different type batteries with the regulators being supplied with current from the panel bus.
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Old 16-12-2019, 01:12   #8
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Re: solar and a vsr

there are regulators on each system fridge batts (mppt) and domestic (pwm) starter batt system doesnt require a reg as output from its solar panel is 1amp max, where do I install the vsr in the fridge system should it be between the batts and the mppt reg, or elsewhere, and will installation harm the mppt.
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Old 16-12-2019, 02:43   #9
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Re: solar and a vsr

Quote:
Originally Posted by Elevation View Post
there are regulators on each system fridge batts (mppt) and domestic (pwm) starter batt system doesnt require a reg as output from its solar panel is 1amp max, where do I install the vsr in the fridge system should it be between the batts and the mppt reg, or elsewhere, and will installation harm the mppt.
Yes, between the fridge batteries and the MPPT.

However, I agree with the other comments and on a 25ft yacht I don't think I would replace the 130Ah battery when it dies. I don't think you need the extra capacity on a small yacht, so save the pennies. Instead use the Trojans as the house bank and in the future direct the VSR to the engine start battery. This is a very common set up on smaller yachts. Also think about the solar controller settings, 6 volt Trojans want and need 14.8v, that is too much for most AGM batteries and will shorten their life. An ordinary flooded lead acid (FLA) will start the engine and be more tolerant of the Trojans charging voltage. Something to think about in the future when the engine start battery needs replacing, but continue to use it for now as you already have it.

All solar goes through the solar controller or controllers to the house.

Then if there is a heavy duty emergency switch between house and engine start,in the event of a Trojan going down you can use the engine start battery to run the house loads on a temporary basis, or use the Trojans to start the engine if the engine battery goes down.

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Old 16-12-2019, 02:51   #10
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Re: solar and a vsr

The vsr goes between the 2 batteries. Pos post to pos post and has nothing to do with the solar controller. . Folliw the instructions. The neg of each battery should already be joined together. If not. It needs to be.
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Old 16-12-2019, 07:01   #11
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Re: solar and a vsr

I rewired my boat using this excellent schematic from Maine Sail. I read his treatise on ACRs and it makes perfect sense. After a season running, I'm totally sold as it has performed superbly.

https://marinehowto.com/automatic-charging-relays/

So in short, I connected a Blue Seas ACR between my house and start banks. When either side of the ACR senses voltage above a certain point (which means it's being charged), it will close the contact and combine the banks. I also added the start isolation circuit that will temporarily disconnect the banks when I engage start button to be sure I'm not trying to start the engine with house bank. When I disengage the starter, it parallels the banks automatically so the alternator is charging both. I have alternator connected to house bus, the start battery is being charged when the ACR parallels the bank.

So in your case, if you place the ACR between the solar bank and the house bank, when the solar bank is being charged from solar, it will close the contacts and also charge the domestic bank. It's early in the morning but I believe if you have your battery switch set to all, then essentially you will be using your 200W solar setup to charge ALL your batteries, in essence 1 large bank.

I only have 2 banks, start and house. If you look at the schematic below, you'll see that every single load (except for the actual engine starter) is connected to house. I run my MPPT to this house bus as well. I only have a 80W panel that I deploy on mooring to keep batteries topped up. Works great and all my batteries are always topped off.
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Old 16-12-2019, 07:12   #12
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Re: solar and a vsr

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Originally Posted by Elevation View Post
Why is it on these forums no one answers the question as asked. You might think it flawed/ not what you would do, but it has worked faultlessly since installation some 6 years ago Don't know why I bothered asking for advice
Well, from my standpoint, your question is akin to asking, “What is the best first aid cream to treat poking myself in the eye with a fork?”

And if we remove the total narcissism from the equation, we may recognize that perhaps the poster is not the only one reading the answers in a public forum.

So another question, “If to suit the posters sensitivities, the answers must meet some predefined parameters else be considered somehow offensive, why not share those up front, or just refrain from posting in a public forum, where contributors may make the huge mistake of trying to help the OP, and anyone else who may see it?”
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Old 16-12-2019, 08:41   #13
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Re: solar and a vsr

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Originally Posted by ramblinrod View Post
Well, from my standpoint, your question is akin to asking, “What is the best first aid cream to treat poking myself in the eye with a fork?”

And if we remove the total narcissism from the equation, we may recognize that perhaps the poster is not the only one reading the answers in a public forum.

So another question, “If to suit the posters sensitivities, the answers must meet some predefined parameters else be considered somehow offensive, why not share those up front, or just refrain from posting in a public forum, where contributors may make the huge mistake of trying to help the OP, and anyone else who may see it?”
For the benefit of anyone reading this thread, some higher end solar charge controllers (e.g Midnite Express) have a built in “Hot water” excess energy dump function. Those interested in electronic projects can build a discrete controller from readily available parts. Try “Google.”
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Old 16-12-2019, 11:19   #14
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Re: solar and a vsr

Quote:
Originally Posted by Elevation View Post
Why is it on these forums no one answers the question as asked. You might think it flawed/ not what you would do, but it has worked faultlessly since installation some 6 years ago Don't know why I bothered asking for advice
The reason it works is because you are using 200w solar (in Australia) and therefore your battery's are full before noon and all that lovely energy is getting dumped so why have 200w solar

Most boaters I have met . read , and I have, is a simple version like you have been advised by the forum in that one house bank connected too the solar and one starter bank with a VSR system making more of all that free energy , the more wires and batteries you have the more energy that is wasted making everything work that little bit harder and therefore potentially reducing life span of certain elements.
Your system is not flawed just over exaggerated and as we cruisers like to keep weight and tec, to a minimal we go for the simplest easiest solutions , if you got a professional electrician to do this they would also advise you the same.
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Old 16-12-2019, 12:57   #15
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Re: solar and a vsr

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Originally Posted by tarian View Post
The reason it works is because you are using 200w solar (in Australia) and therefore your battery's are full before noon and all that lovely energy is getting dumped so why have 200w solar

Most boaters I have met . read , and I have, is a simple version like you have been advised by the forum in that one house bank connected too the solar and one starter bank with a VSR system making more of all that free energy , the more wires and batteries you have the more energy that is wasted making everything work that little bit harder and therefore potentially reducing life span of certain elements.
Your system is not flawed just over exaggerated and as we cruisers like to keep weight and tec, to a minimal we go for the simplest easiest solutions , if you got a professional electrician to do this they would also advise you the same.
Well, technically it is flawed.

On the occasions he had to hook up a shore power charger, it may not have been required, had the battery capacity been selected and configured properly.

Additionally, the batteries as they are may not live as long, as if selected and configured properly.

The system is “sub-optimal” for the reasons stated. If I recommended a system be configured that way, I would expect a scolding from the forum, as I should know better (as should anyone performing DIY work on a marine battery charging system).

Just because someone hooks something up, and it works (maybe just sorta, and maybe just for now) does not mean it was done right.

So it’s really no big deal, and his system is working (to some extent) for him, but as a professional marine electrician, it could be considered remiss, had I not advised as I did so that they could be remedied when convenient, if desired.

There are all kinds of variables. If the AGM were configured as an “emergency” battery, high in the vessel, to keep nav and comma running if the boat were flooded, I would have stated “bravo” (but you may want to consider an isolated LFP for that function, and I would have still advised the risks of a series house bank, with no remaining capacity, on a single battery failure.
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