Charge regulator and 2nd battery bank. (1 Viewer)

[Snowbird]

I have recently upgraded the batteries on my fifth wheel. Replacing the single Banner battery with 2 larger capacity batteries. I have checked the Banner battery and it is still good, so have set up a second battery bank using the Banner battery. This second battery bank I have connected a 4000 watt inverter for occasional use, ie, cooks hair dryer. This is completely separate from the main battery bank, so will not deplete that. Now, the main batteries are connected to the solar regulator via the battery output on the regulator. My question is, can I connect the Banner battery to the now empty load connections on the regulator, so as to charge the Banner battery from the solar panels.

 

[HandyAndy]

Not tested this theory at ALL but in my brain the "Load" output will be a regulated 12v supply, not a charging source.
A charging source would need to be quite a bit above 12.6v for any electrons to flow
Plus the fact the load wattage rating maybe tiny (depends on make)
I could test this of course (on a EP Tracer) in about ten minutes once I have drunk coffee and got some trainers on.

 

[Snowbird]

Not tested this theory at ALL but in my brain the "Load" output will be a regulated 12v supply, not a charging source.
A charging source would need to be quite a bit above 12.6v for any electrons to flow
Plus the fact the load wattage rating maybe tiny (depends on make)
I could test this of course (on a EP Tracer) in about ten minutes once I have drunk coffee and got some trainers on.

If there is any way you could test this theory for me I would be very grateful. I could of course disconnect the load from the battery bank and attach to the load terminals on the regulator, this would then in effect free up the battery terminals for the second battery bank. The down side to this is that American RVs are very battery hungry with 3 slideouts electric landing legs and electric awning, before getting down to the internals like 12volt fan heater etc.

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[HandyAndy]

Looks like I was incorrect
Load output terminals match and connect to the battery (bank 1) terminals so whatever the Battery bank 1 is, then the load output equals this.
Therefore if the solar is charging Bank 1 it is therefore "charging" the load output.
The only issue you'll have is if you pull a load at battery bank 2, the controller circuitry by it's connected nature will try to "share" battery bank 1's power to support the load you put on bank 2 equally.
So if you want 4000w (you wont be able to anyway) then it will try to put 2000 of that through the charge controller and back up the charging wires connected from the charge controller to bank 1...
Does anyone smell smoke

If you have a really decent controller it will have internal circuitry that will disconnect the output so an overload can't happen.
If you have a half decent controller it will have soldered fuses that will pop to prevent any magic smoke from escaping.
If you have a cheap chinese controller... have a fire extinguisher ready

 

[HandyAndy]

Some pics. ?
As you can see on the cheap chinese tat the positive of solar panels battery bank and load input are directly connected so if you have one of these you better be sure that second battery has an exactly equal charge to your main bank when you connect it as a single battery inrush current is as good as unlimited and will pop that little strip of solder quicker than you can blink and recoil ??

 

[Snowbird]

Looks like I was incorrect
Load output terminals match and connect to the battery (bank 1) terminals so whatever the Battery bank 1 is, then the load output equals this.
Therefore if the solar is charging Bank 1 it is therefore "charging" the load output.
The only issue you'll have is if you pull a load at battery bank 2, the controller circuitry by it's connected nature will try to "share" battery bank 1's power to support the load you put on bank 2 equally.
So if you want 4000w (you wont be able to anyway) then it will try to put 2000 of that through the charge controller and back up the charging wires connected from the charge controller to bank 1...
Does anyone smell smoke

If you have a really decent controller it will have internal circuitry that will disconnect the output so an overload can't happen.
If you have a half decent controller it will have soldered fuses that will pop to prevent any magic smoke from escaping.
If you have a cheap chinese controller... have a fire extinguisher ready

Ah, good man. I think the best way to try this is plug the hair dryer directly into the inverter and see what happens. Luckily the batteries, charge controller, and inverter are all together in the same locker. Many thanks Andy.

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[HandyAndy]

No problem..
If you have a half decent controller like my EP Solar 1215 then the output will be MOSFET controlled and the until "should" cut the power to the load socket to prevent damage.
Had a little looksee inside mine for confirmation and yep. Just a 30 amp fuse on the input, mosfet on the output.

 

[Snowbird]

No problem..
If you have a half decent controller like my EP Solar 1215 then the output will be MOSFET controlled and the until "should" cut the power to the load socket to prevent damage.
Had a little looksee inside mine for confirmation and yep. Just a 30 amp fuse on the input, mosfet on the output.
View attachment 346317View attachment 346318

So, in conclusion, we think this COULD work. Do you think there would be anything to gain by wiring the trailer load into the load terminals of the controller instead of direct to battery 1, and wiring battery 2 with the inverter into the battery terminals of the controller. Sorry for all the questions, but as its something I have not tried before am doing my best to get the best from what I have.
I will not be using the inverter very often, but I already have it so may as well use it.
I already have a 250 watt solar panel on the roof, which should more than feed my 250 amp main battery bank, so fitting a second battery with inverter was the obvious solution to any excess sun power I produce.
I am also in the process of fitting a diesel heater into the trailer and would like to wire that to battery 2. This would also alleviate the problem of my main bank being depleted. Diesel heaters will switch off if the battery level drops too low, so that should not be a problem.

 

[HandyAndy]

I'm still researching it actually as it looks like even the cheapo chinese controller is mosfet (or at least IGBT) controlled on the negative side

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[andy63]

My question is, can I connect the Banner battery to the now empty load connections on the regulator, so as to charge the Banner battery from the solar panels.

Ill add my two penneth lol..
Not a good idea IMO.. Its not what its designed for.. Its just like linking two batteries at different states of charge.. If you have been using an inverter off one of the banks its likely as pointed out to try and draw way more than it can supply.. Asking for trouble IMO..
Is your second battery bank just the single banner battery or have you added to it... Because a large inverter running of a single battery is also not good..
I'd look to make sure the inverter has a decent battery bank capacity to run it and a dedicated charging set up...
Just my thoughts..
andy...

 

[Snowbird]

Ill add my two penneth lol..
Not a good idea IMO.. Its not what its designed for.. Its just like linking two batteries at different states of charge.. If you have been using an inverter off one of the banks its likely as pointed out to try and draw way more than it can supply.. Asking for trouble IMO..
Is your second battery bank just the single banner battery or have you added to it... Because a large inverter running of a single battery is also not good..
I'd look to make sure the inverter has a decent battery bank capacity to run it and a dedicated charging set up...
Just my thoughts..
andy...

The Banner battery is a stand alone, not in any way connected to the house battery bank, (except by the controller). I will only ever be using the inverter for occasional use. I may connect the diesel heater to the stand alone Banner battery to conserve power to my main 250amp battery bank.
My thinking behind the two battery system is that my main battery bank will only be used for slideouts, TV, lights, gas blown heating and water pump.

 

[HandyAndy]

but the controller IS effectively connecting the two battery banks together, so assuming you have both banks at equal charge and you connect the inverter up to whichever battery bank and turn it on it will try to draw equal energy from both banks but the controller circuitry will have a hissy fit...

Dark now and I have found my buck boost converter so I should be able to simulate battery voltage but at low amps to see what happens.... tomorrow.
I got side tracked by a mouse chewing my MH matress when I was out there hunting for the buck booster so al I have since done is clear everything that can be nibbled out of the MH and swapped portable solar chargers to another vehicle as that was getting low..
I have a spare cheap chinese PWM controller so I don't mind setting fire to that for the sake of science tomorrow

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[Snowbird]

but the controller IS effectively connecting the two battery banks together, so assuming you have both banks at equal charge and you connect the inverter up to whichever battery bank and turn it on it will try to draw equal energy from both banks but the controller circuitry will have a hissy fit...

Dark now and I have found my buck boost converter so I should be able to simulate battery voltage but at low amps to see what happens.... tomorrow.
I got side tracked by a mouse chewing my MH matress when I was out there hunting for the buck booster so al I have since done is clear everything that can be nibbled out of the MH and swapped portable solar chargers to another vehicle as that was getting low..
I have a spare cheap chinese PWM controller so I don't mind setting fire to that for the sake of science tomorrow

Once again, many thanks Andy. I just remembered I once had a little gizmo made by I think CE that allowed any extra charge to be sent to a second battery bank, but for the life of me I cannot find any info on the net about it now. Maybe they have stopped producing it. This is why I thought I could charge my second battery from the load terminals of the controller. Its my own fault for thinking these crackpot ideas may work, as I have too much time on my hands. Or so cook keeps telling me.

 

[Sheddy]

That's what you are looking for Dave.
Cheers
Ed

 

[Robert Clark]

I have two sets of leisure batteries.
One set (lithium) supply an inverter/charger and are connected to our solar controller.

The second set is the factory fitted leisure battery which supplies all 12v requirements.

I have fitted a Sterling battery master between the two sets of batteries which passes up to 3A from the lithium batteries to the leisure batteries when the lithium’s have sufficient charge from the solar controller.

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[autorouter]

I presume you don't intend to take the full 4000 watts from your inverter - 4000 watts will pull 4000/12 = 333 amps from the battery.

If you take 1200 watts from the inverter, that will draw 1200/12 = 100 amps from the battery. A 100Ah leisure battery is supposed to take up to C/5 amps, where C is the Ah capacity. So that's 100/5 = 20 amps. So you'd need five of these batteries to supply 100 amps.

If you're only using it occasionally for a short time, you could probably get away with three or even two batteries. But one single leisure battery is pushing your luck.

However if the battery is a Banner Running Bull type, it's basically a starter battery, which is made to supply a high current for a short time, so you'll probably be OK as long as you can put the charge back into it fairly quickly.

The proper solution to charging one battery bank from another battery bank is a B2B charger. Connect the input to the solar-charged Bank 1, and the output to the inverter Bank 2. You could wire a switch on the input, so you can control when it gets charged, and can be cut off if you're running low on bank 1.

 

[Snowbird]

That's what you are looking for Dave.
Cheers
Ed

Eureka, thats the thing Eddy. I thought they had stopped making them. I had the same system on my old FFB years ago and it worked exactly the same as I want to do now. I just wondered if I could wire into the charge controller, if not then I can go down this route again.

 

[DBK]

You could connect the Banner battery in parallel with the leisure batteries but using a meaty diode so it gets a charge but doesn't contribute to leisure loads.

However, this means the skipper's hair dryer will drain the leisure batteries. So some sort of isolator would be needed as well. This could be manual or, if you could find a suitable relay, automated. Turn on inverter, relay opens contacts and isolates the Banner.

This should work.

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[HandyAndy]

A simple 4 position battery isolator switch would do it..
Output (inverter) connects to either
Pos 1. Battery bank 1
Pos 2 Battery bank 2
Pos 3. Battery bank 1+2
Pos 4. Disconnect

£16 on ebay

 

[Snowbird]

A simple 4 position battery isolator switch would do it..
Output (inverter) connects to either
Pos 1. Battery bank 1
Pos 2 Battery bank 2
Pos 3. Battery bank 1+2
Pos 4. Disconnect

£16 on ebay

I know this thing works as I have used it in the past for the exact same job as I want to do now. I would just love to know if the load contacts on the controller would do the same job though.

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[HandyAndy]

Yes but with cautions and exceptions..
Yes it would charge the second battery bank
Both banks would need to be at the same charge level on connection and every subsequent connection... and that what I've typed right there should discount the idea..
If both batteries have to be charged to the same level before you can connect the controller to avoid overload then what use is it......
AND
You would (should) disconnect the charge controller via some sort of switch BEFORE switching on any inverter / load or you risk overload in that situation too..

Consider the fact that the fully charged battery will act as a 12v 600 amp (capable) charger when you connect the flat 12v battery to it via the controller.
Now while the flat battery will self regulate it's inrush current, it can and WILL accept circa 70 amps on connection.. Do you think the control circuitry in the charge controller is designed for this.. I do not

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[jollyrodger]

Why not just get a duo solar controller

EPever DuoRacer D1206N-DDS 10A MPPT Solar Dual Battery Controller 12V/24V - MT11 | eBay

Max PV input at 24V: 260W. Max PV input at 12V: 130W. Always happy to help.

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Or similar ?
I have 2 banks of 110A the front 2 feed the aux side of the van .
The rear 2 dedicated to a 1500w inverter(could go bigger but don't need it).
Solar keeps both banks very healthy .
Or am I missing somthing ?

 

[HandyAndy]

Loads of different ways round it I think.. but they all involve spending money and snowbird clearly squeaks when he walks

 

[Snowbird]

Loads of different ways round it I think.. but they all involve spending money and snowbird clearly squeaks when he walks

Money is NOT for spendin, its for makin MORE money.

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[HandyAndy]

???

 

[Snowbird]

OK lads, I have decided to go down the route of the CBE split charge relay in the interests of safety as I know this works from previous experiments. Once again many thanks to Andy for his testing of this new theory for which am very grateful, BUT, I still cannot get my head round the fact that I cannot use the load contacts on the controller to charge a second battery. My thinking behind this is, the second battery would act as a stabilising force for whatever the inverter tried to pull. No different than if the van load was connected to the load contacts and you switched all lights on, water pump for shower and cook was watching Coronation St on TV all at the same time. I am loosing sleep over this problem now, and cannot get it out of my head, but must bow to superior knowledge. Damn, another of my crackpot ideas goes up in smoke.

 

[HandyAndy]

You can use the load contacts to charge both batteries but in connecting it like that it prevents you from putting large loads on EITHER battery bank (through inverter or otherwise) because that energy consumption from will try to pull from BOTH battery banks at the same time.
Its effectively the same as joining two batteries together with a tiny bit of fuse wire then connecting the hair drier to one of them, it will try to take some of that power from the second one and the fuse will let go.

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[Snowbird]

You can use the load contacts to charge both batteries but in connecting it like that it prevents you from putting large loads on EITHER battery bank (through inverter or otherwise) because that energy consumption from will try to pull from BOTH battery banks at the same time.
Its effectively the same as joining two batteries together with a tiny bit of fuse wire then connecting the hair drier to one of them, it will try to take some of that power from the second one and the fuse will let go.

Now its becoming clearer.