off grid solar system recommendation

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Re: off grid solar system recommendation

Postby angusjones8 » Thu Dec 15, 2016 8:06 pm

Yeh I looked at EV Works website and ut said back order only. Might give them a call.
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Re: off grid solar system recommendation

Postby APR » Thu Dec 15, 2016 9:50 pm

2 x Goodwe GW5048D-ES Hybrid inverters, 13kW panels, 20kWh LiFePO4
Mk2 PV Router feeding excess solar generation to a 3.6kW 250 ltr HWS
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Re: off grid solar system recommendation

Postby angusjones8 » Sun Jan 22, 2017 7:59 pm

Puzzle pieces coming together!!
So far:

Latronics 7048 inverter
Outback fm80
16x 200ah winston batteries
4x GNE balances
2x cell log 8M monitors
18x 270w csun pannes

Got panels and inverter 2nd hand.

Bought the batteries, balancers and cell logs from Trev at drive by nature, he was very helpful.
He said I won't need a BMS with the balancers and the solar controller will do high and low voltage cut out??
Hope this makes sense to someone cause it's taking a while to sink in at my end!!
Thanks
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Re: off grid solar system recommendation

Postby timbo649 » Mon Jan 23, 2017 7:13 am

He said I won't need a BMS with the balancers and the solar controller will do high and low voltage cut out??


Normally solar controller/charger does cut off - that's right, but what if it does not? Just a bad day or freaky accident. One overcharge might kill your batteries.
I'm not in position to advise anything, I don't know how good or bad selected parts, but I think you might consider a BMS with monitoring/balancing instead of separate balances and monitors. Price of BMS is much lower than price of batteries. You might think about it as an insurance.

Regards, Tim
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Re: off grid solar system recommendation

Postby davidg » Mon Jan 23, 2017 9:15 am

The reason a "BMS" should be installed or more to the point and HVD/LVD is to protect the pack if one cell goes too high or too low in voltage. You can have one cell that goes high or low before the rest if that is allowed unchecked you can have a serious issue and ruin all the cells in the pack over relative short period. Thats the reason for have a "BMS"

The combined total of parts are really a BMS not just one part.
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Re: off grid solar system recommendation

Postby APR » Mon Jan 23, 2017 11:40 am

angusjones8 wrote:He said I won't need a BMS with the balancers and the solar controller will do high and low voltage cut out??
Hope this makes sense to someone cause it's taking a while to sink in at my end!!
Thanks


You are relying on the charge controller not overcharging the batteries. If the charge controller were to spit the dummy you could shag a $6,000 set of batteries.

You are also relying on the inverter to not draw down the batteries past a low voltage set point. This will only happen if your batteries cannot meet your night time energy requirement.

If the above works OK, the only issue you then have to contend with is cell balance. The balancers you are proposing to use work well, however, failure of a balancer cannot be rules out.

Victron make a limited capability BMS that they call the BMV-702. This unit has the ability to control a relay to switch out the battery pack if pack voltage goes over or below configured set voltages. It also has the ability to control a relay to shut down the pack if the voltage of the bottom 8 cells varies from the voltage of the top 8 cells (pack mid-point monitoring) . You can configure the voltage differential between the 2 groups of cells at which the pack will be switched out. If you don't want the pack to switch out unexpectedly, you could use the trigger from the Victron BMV-702 to sound an alarm.

I am using the single balancers from the Electric Car Parts Company with a Victron BMV-600, but am going to upgrade to the BMV-702 specifically for it's mid point monitoring.
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Re: off grid solar system recommendation

Postby Gordon-Loomberah » Mon Jan 23, 2017 12:53 pm

APR wrote:You are also relying on the inverter to not draw down the batteries past a low voltage set point. This will only happen if your batteries cannot meet your night time energy requirement.


Angus might want to consider having the LVD in the LS7048 changed (and get new caps installed while they have it), as the original LVD is a bit too low for 16 LiFePO4s. I had mine raised to 49V, as the highest setting is normally 46V. Depending on the load at the time, that can catch an individual low cell too.

I am using the single balancers from the Electric Car Parts Company with a Victron BMV-600, but am going to upgrade to the BMV-702 specifically for it's mid point monitoring.


I'm using those balancers, but am finding they don't keep the 2 halves of the pack in balance at all- near the end of Absorb when the net charging current is well under 10A, there can be over 0.5V between the 2 halves of the battery.
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Re: off grid solar system recommendation

Postby angusjones8 » Mon Jan 23, 2017 7:30 pm

Some great info here thanks.
I'm happy to buy a BMS if it's going to be better. Any easy to instal ones people recommend?

On the inverter that's a great suggestion to get the LVD adjusted, thanks.

Also what is a recommendation for a charger so I can charge from my generator?

I've spoken to 3-4 local solar people and they all seem scared or sceptical of LiFePo4 batteries so getting info is hard.
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Re: off grid solar system recommendation

Postby davidg » Mon Jan 23, 2017 9:09 pm

APR wrote:has the ability to control a relay to switch out the battery pack if pack voltage goes over or below configured set voltages. It also has the ability to control a relay to shut down the pack if the voltage of the bottom 8 cells varies from the voltage of the top 8 cells (pack mid-point monitoring).


Mid point monitoring is nice but it's absolutely no where good enough for individual cell over/under issues, you need to monitor every cell individually or parallel cells for LVD/HVD, to ensure that potential issue are averted.

Mid-point monitoring, Selectronic have been doing that for years it is STD in all SP-Pro's not an optional extra with all sorts of options.
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AC-Coupled Grid-Connect Inverters,
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Auto Backup Genset
PVOutput Stats

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Re: off grid solar system recommendation

Postby timbo649 » Mon Jan 23, 2017 9:34 pm

angusjones8 wrote:I'm happy to buy a BMS if it's going to be better. Any easy to instal ones people recommend?


I use BMS from this company http://www.ev-power.com.au/-Thundersky- ... stem-.html
Scroll down, they have a model for remote areas. They made a custom configuration for my system. Very easy to install.

However, that was a bit tricky to balance batteries (16 CALBs 400AH) before commissioning the system - something to keep in mind.

angusjones8 wrote:Also what is a recommendation for a charger so I can charge from my generator?

I've spoken to 3-4 local solar people and they all seem scared or sceptical of LiFePo4 batteries so getting info is hard.


I use Victron MultiPlus as inverter and charger, but it is AC coupled system. Australian representative/service guy for Victron was unaware, that Multi can be used in such way. Even when I pointed to their brochure, he insisted that it was impossible. Luckily I got an advice from Netherlands. Everything happened to be easy.
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