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diy solar

Load shedding back up system

Komsolar

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Joined
Jan 16, 2023
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5
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Kommetjie South Africa
Hi, I have put together system where I have two 100w 18v poly panels joined together in parallel, which is being controlled by a PMW 30 amp solar charger, feed into a 12v 105ah lead acid deep cycle battery. Hooked up to the battery I have a 1000w modified sine wave inverter. Plugged into the inverter I have a switch that switches from house ( grid) power 220v to inverter power ( 223v) when the house power cuts out in 0.20ms, (usually around 2.5 hours a time at least 3 times a day, some times its 4 hours long. In South Africa this is called load shedding and the government owned utility does this to prevent complete grid collapse, when they lose generating power capability due to generator failure due to poor maintenance of the grid and generators over the last 25 years). I'm running around 120 - 350 watts of alliances, (TV, Sound Bar, Android media box, router, fibre box and two 6w leds lights)off of the inverter. Generally the panels do a pretty good job at keeping the battery charged and can charge t fully in around 7 hours of sunlight, when we have around 2.5 hours power outage per day, but any more than that there is an issue. I put the transfer switch in to ensure that we ran off the inverter only during time of no grid power. Recently the inverter input voltage alarm is sounding (typically when the battery is near full charge), indicating voltage form the battery is above 15v and the inverter shuts down until the voltage from the battery comes under 15v.Surely the charge controller should not allow the battery to change above 14v? So gut feel is that there is a problem with the solar charge controller putting too high a voltage to the battery? does this sound right? I have ordered a Victron 75/15 bluetooth enabled solar charger which will come tomorrow. since the one I have his a cheap PWM 30 AMP one. Should I be leaving the system running permanently off the inverter and never on house power, as when I do this there is never the issue of over voltage coming frmm the battery? does anyone have any idea what the problem could be, id really appreciate advice . I'm just worried the battery will not fully charge using the PWM charger and that's why I have ordered the MPPT charger albeit its only 15Amp charger. please let me know any advice thanks
 
If the voltage goes above 15v it's possible that you connected the pwm controller to the solar panel before connecting the battery.

That will cause the controller to "think" it's a 24v system.

A victron 75/15 is a great charger though, a step in the right direction in any case, just be sure to connect it to the battery first.
 
If the voltage goes above 15v it's possible that you connected the pwm controller to the solar panel before connecting the battery.

That will cause the controller to "think" it's a 24v system.

A victron 75/15 is a great charger though, a step in the right direction in any case, just be sure to connect it to the battery first.
thanks very much for this. I will be sure to do so
 
Hi, Ive now connected my new Victron Solar charger smart solar 75/15 . I don't see a preset for a lead acid battery, only a gel battery and lithium batteries also PSZ tubular state traction batteries, can anyone let me know what battery preset to select if I have a deep cycle 105ah 12v lead acid battery?
 
If the voltage goes above 15v it's possible that you connected the pwm controller to the solar panel before connecting the battery.

That will cause the controller to "think" it's a 24v system.

A victron 75/15 is a great charger though, a step in the right direction in any case, just be sure to connect it to the battery first.
Hi, Ive now connected my new Victron Solar charger smart solar 75/15 . I don't see a preset for a lead acid battery, only a gel battery and lithium batteries also PSZ tubular state traction batteries, do you happen to know what battery preset to select if I have a deep cycle 105ah 12v lead acid battery?
 
Gel would be closer, but i looked at the 2 documents for that device on Victron's website and it's not obvious what the presets actually do. It looks like absorption and float voltage are adjustable, but not obvious to me if there are any other settings (absorption timers, tail current sensing, etc) so if everything else is fixed, i would just adjust the absorption and float settings to match what you know was working on your last controller. If you never adjusted those at all and just ran it at some default FLA settings, just set it to Gel until you have had time to learn what might be more appropriate. Generally it is better to be a couple tenths lower than ideal on voltage than a couple of tenths higher, and i suspect the gel setting will be a couple tenths low. How far off of ideal it is to run a setting that is a few tenths of a volt low for a few days, is still not as bad for the battery as a few days with no sun..

Do you ever check specific gravity on the battery, or go purely by voltage? Measuring SG would let you home in on the ideal settings for your battery, but it can be sort of a tedious process to collect and digest that information.
 
Gel would be closer, but i looked at the 2 documents for that device on Victron's website and it's not obvious what the presets actually do. It looks like absorption and float voltage are adjustable, but not obvious to me if there are any other settings (absorption timers, tail current sensing, etc) so if everything else is fixed, i would just adjust the absorption and float settings to match what you know was working on your last controller. If you never adjusted those at all and just ran it at some default FLA settings, just set it to Gel until you have had time to learn what might be more appropriate. Generally it is better to be a couple tenths lower than ideal on voltage than a couple of tenths higher, and i suspect the gel setting will be a couple tenths low. How far off of ideal it is to run a setting that is a few tenths of a volt low for a few days, is still not as bad for the battery as a few days with no sun..

Do you ever check specific gravity on the battery, or go purely by voltage? Measuring SG would let you home in on the ideal settings for your battery, but it can be sort of a tedious process to collect and digest that information.
thanks for this, I only went with battery Voltage and have set it to gel for now.
 
The default settings of the victron are fine for an AGM, but you'll also need to get the Victron Battery Sense module to use temperature compensation.
 
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