PaulRainbow
Well-Known Member
Where are the Victron dual battery mppt controllers
Could we have some links please ?
Basic Solar Charging Questions?
- Thread starter Dougal
- Start date
Could we have some links please ?
VicS
Well-Known Member
Dougal
Well-Known Member
They look like just what I need to charge my batts
PaulRainbow
Well-Known Member
LadyInBed
Well-Known Member
My boat stays in all year and I control my 2x80w solar with a [h=2]20A DUAL BATTERY SOLAR CHARGE CONTROLLER / REGULATOR FOR 12V / 24V BATTERIES[/h]Works well, it took me a couple of weeks whilst cruising last summer to realise that my 12v alternator had failed!
Dougal
Well-Known Member
Thanks. Is it an MPPT controller? If so, what make and model?
VicS
Well-Known Member
If you click on the bold uppercase phrase you will discover that it's a Photonic Universe PWM controller
matthewriches
Well-Known Member
These are the MPPT variants http://www.photonicuniverse.com/en/catalog/list/category/DBMPPTcontrollers
vyv_cox
Well-Known Member
I use a PWM dual output controller with 125 watts of solar. I am perfectly happy with it after many years of use. An MPPT might possibly give some small advantage but my batteries cope well with all my loads including fridge 24/ in ambient temperatures in the 30s.
Dougal
Well-Known Member
I guess if we had the space to add another panel, we'd be the same, our 100w output (which we never get lol) just doesn't quite 'hack it'. So I'm hoping the little extra supplied from MPPT will make the difference. I could of course, just buy a newer fridge and heave our old one over the side. Hey, then I could dive on it to see how it's holding
VicS
Well-Known Member
But they only trickle charge, max 1 amp, the second battery
PaulRainbow
Well-Known Member
But they are not dual MPPT controllers. They are single output MPPT with a trickle charge for the engine battery. It is not technically possible to simultaneously charge two separate banks with a single controller using MPPT. The controller can't match MPPT to both banks at the same time, as they will have differing SOC.
Why do you suppose the like of Victron don't make a dual MPPT controller ?
matthewriches
Well-Known Member
Correct, Victron don’t make a dual output MPPT. If the OP wishes to charge his leisure batteries and maintain his engine start battery, the device mentioned will work very well for him.... with his dreaded 1-2-b-o switch and will not require fitment of a VSR in that case for his solar to charge both banks.
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PaulRainbow
Well-Known Member
it will indeed maintain his engine battery if it's left unattended for a time. It won't put any meaningful charge into the engine battery while he's on the boat, which is not usually an issue, but could be in the case of a problem that requires using a lot of power to start the engine, or repeatedly start it (fuel problems etc ?
Not the end of the World, he can leave the engine running. Oh, wait, he'll have to switch the 1-2-B to the engine battery, or both. In fact, he'll have to do that anytime the engine is running, due to the presence of the 1-2-B and the absence of a split charge system.
He's also said he'll likely change the switch sometime soon, at which point he'll need to buy a VSR, ArgoFET or similar.
I'm sure there will be cases where this controller would be a decent buy, if the boat already has a split charge system (not a VSR) and there is no requirement for the display, it would work fine using the solar to keep everything charged up.
But as the OP would need to buy the controller, a split charge device and then another £79.99 for the display, i don't think it's the best solution for him.
lw395
Well-Known Member
That's incorrect.
MPPT is a method of extracting maximum power from a solar panel. (or other power source of variable impedance)
It is perfectly possible to take that power and regulate two outputs from it.
But with a limited amout of power available, you have to prioritise one output, or decide what you want to happen when there's insufficient sunlight to put as much charge as you'd like into both banks.
I would expect Victron make what they perceive there is a market for. They have a huge market in solar power for signs, lights etc where there is only one bank. Boats are a sideline for them.
PaulRainbow
Well-Known Member
No it isn't
The controller is designed to get the most current into the batteries. It senses the voltage at the batteries to be able to apply the best voltage for the batteries. It is, in essence, a DC-DC converter, it cannot apply different charging voltages to two banks at the same time.
VicS
Well-Known Member
Surely the whole point of a MPPT controller is to do what its name suggests. To control the current drawn from the solar panel so that it operates at its maximum power output point
LadyInBed
Well-Known Member
FYO, my dual controller was holding both banks at 14.1v today. Probably not much current flowing, as they weren't on load but 13.7v is the norm when on load.
PaulRainbow
Well-Known Member
Of course it is, that's how it gets the most current into the batteries. The MPPT is based on the output of the panels and the load to which the current is going (the batteries in our case). So it obviously needs to monitor the panel voltage and the battery voltage. It's easy enough to monitor the voltage of two battery banks, but how does the controller decide which one to use when calculating the MPPT ?
The controller will also instantly adjust its output to keep pace with loads on the battery (providing there is more current available than the battery is taking). So if you tried to make a dual output controller, logic dictates that the controller must monitor the domestic bank, to keep up with the changing loads. The controller must also makes it's adjustments based on that monitoring, so it's output would be geared for the domestic bank. The engine battery would get the same charge voltage as the domestic bank.
So what's the point of making a dual output MPPT controller, If it can only monitor the domestic bank and charge both banks based on that ? May just as well fit a single controller and your choice of split charging device, if needed.
No doubt every manufacturer of MPPT controllers in the known Galaxy thought similar, that's why none of them make such a device (as far as i can see).
noelex
Well-Known Member
The MPP (maximum power point) is a property of the solar panel. It will vary with the luminance, temperature etc, but it has nothing to do with the battery voltage. Tracking this voltage (the T in MPPT) is just modifying the input voltage so the solar panel maintains the MPP. Once again this has nothing to do with the battery voltage. The controller does not have to decide which battery voltage to use, because the battery voltage does not alter the solar panels MPP.
A dual output MPPT controller could be manufactured, but it would be complex because the voltage conversion and voltage monitoring would need to be doubled. The controller (ideally) needs to alter both output voltages based on the needs of each battery. This would make the unit expensive and increase the self consumption, reducing efficiency .
It is unlikely it would be a commercial success as a simpler VSR would be a better solution for most installations.
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