Can an MPPT solar regulator have a battery between the solar and the regulator

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T1 Terry
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Can an MPPT solar regulator have a battery between the solar and the regulator

Post by T1 Terry »

I've been thinking along the lines of adding a battery in parallel with the solar feed cables so when the regulator deems the incoming current is too high compared to the load on the output side, it limits the input current causing the solar voltage to rise.

My reasoning behind this is that the wasted solar energy could be stored and used when the solar drops back in the evening or if a cloud drifts across the sun.
If the upper limit of the solar open circuit voltage is matched to fully charge battery voltage, the current should drop back to zero once the inline battery is fully charged.
It would require a diode on the solar side to stop any current back flow turning the panels into heaters, although it would be interesting to have a switchable limited current flow back to the panels to dry them off or if in a snowy region, melt the snow and ice so it will slide off.

Any thoughts on this idea?

T1 Terry
Green but want to learn
antiscab
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Re: Can an MPPT solar regulator have a battery between the solar and the regulator

Post by antiscab »

Goodwe make a 2.5kw dc-dc that does what you're after. It's a bit on the pricey side and only supports a 48v battery, though the efficiency is pretty good
Matt
2023 BYD Atto 3 - 21k km
2017 Renault zoe - 147'000km
2012 Leaf - 101'000km - soon to be trialing a booster battery
2007 Vectrix - 197'000km (retired)
2007 Vectrix - 50k km
antiscab
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Re: Can an MPPT solar regulator have a battery between the solar and the regulator

Post by antiscab »

You could direct connect the battery, however, even with a blocking diode present, the inverter loses its ability to maximum power point track.

Not so much of an issue if you're export limited. If you have an inverter with a contactor output for a diversion load, you could have the battery only connected when the inverter isn't seeking maximum power point anyway
Matt
2023 BYD Atto 3 - 21k km
2017 Renault zoe - 147'000km
2012 Leaf - 101'000km - soon to be trialing a booster battery
2007 Vectrix - 197'000km (retired)
2007 Vectrix - 50k km
T1 Terry
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Real Name: Terry Covill
Location: Mannum SA

Re: Can an MPPT solar regulator have a battery between the solar and the regulator

Post by T1 Terry »

The idea I was looking at, was plugging the DIY EV with a battery voltage of under 250vdc fully charged. The EV could be pulled in to store the excess solar generation and still be able to provide power to the solar regulator even past sun down. I wasn't looking at exporting this power back to the grid, they don't pay enough for it compared to what they want to sell it back to you during the peak load period where the roof top solar wouldn't be assisting with powering the house load.

T1 Terry
Green but want to learn
antiscab
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Re: Can an MPPT solar regulator have a battery between the solar and the regulator

Post by antiscab »

do you have an inverter that supports export limiting (in this case to 0)?

that'd be the only way it would work effectively

I've tried it with standard grid tie inverters, but they just push power at their power limit until the battery is depleted, which wasn't as useful as I had hoped
Matt
2023 BYD Atto 3 - 21k km
2017 Renault zoe - 147'000km
2012 Leaf - 101'000km - soon to be trialing a booster battery
2007 Vectrix - 197'000km (retired)
2007 Vectrix - 50k km
T1 Terry
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Posts: 1952
Joined: Thu, 30 Sep 2010, 20:11
Real Name: Terry Covill
Location: Mannum SA

Re: Can an MPPT solar regulator have a battery between the solar and the regulator

Post by T1 Terry »

Hi Matt, I don't have a grid tie inverter at all and have no plans in the near future to give away my solar generated power, let them buy it at the proper price from the commercial arrays, they at least have negotiating power that the household solar generator doesn't.
The house is at the end of a 2wire SWER feed so any household feeding in between us and the main distribution station (around 2.5km) gets priority so we have a voltage variation from between 150vac and 265vac. At least it's better than it was, sometimes on a cold winters morning, we were lucky to get a single wire filament globe to give a brown glow, a quick scramble to turn the fridges and freezers off to save the motors and simply forget about breakfast and head up to the workshop where the power was better.

T1 Terry
Green but want to learn
paulvk
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Re: Can an MPPT solar regulator have a battery between the solar and the regulator

Post by paulvk »

You would be better off with what I have an OFF Grid inverter with batteries it will go to battery when the mains
voltage gets below a set value and run from solar when there is enough power from the panels this will protect
your fridge's , give you proper lights and depending on the size of the battery some mains fail backup.

In my systems one has two 4kW inverters and 225Ah flooded lead acid battery running at 48V which has
no problems running the fridges , lights , TV for extended periods of time. You might think why not use lithium
battery, problem is 90% of inverter chargers are only set up for lead acid the ones that are set up for lithium are
3 to 4 times the price which means you could buy two or three more sets of batteries so could have twenty to
twenty five years of lead acid and then there is the need for a management system for lithium that has to control the
inverter charger.
T1 Terry
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Posts: 1952
Joined: Thu, 30 Sep 2010, 20:11
Real Name: Terry Covill
Location: Mannum SA

Re: Can an MPPT solar regulator have a battery between the solar and the regulator

Post by T1 Terry »

The idea was to cut out the middleman :lol: Solar at 250dc open circuit with an EV battery fully charged at 250vdc, the solar coming in at 10 amps or so would recharge a 12kWh EV battery is around 4 hrs and supply that much extra energy to the house system via the solar regulator, well after the sun has gone down. Unless the EV is used close to sunrise, there is that period in the morning to recharge before it is unplugged from the system but the system can continue to operate as normal without the EV battery in part of the system.

As an example, mum takes the kids to school and comes home, plugs in. Goes shopping and either plugs in at the free charging at the local shopping centre or just returns home and plugs in again. Picks the kids up after school, does all the sports training or what ever deliveries and returns home and plugs in. Picks up the kids and returns home, plugs in and what ever is left in the battery is a back up for the peak load cooking the evening meal etc.

T1 Terry
Green but want to learn
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