Batteries nolonger fully charging

[MikeA]

I am very new to solar and still trying to figure it all out. I set up a small system on my shed for power to the shed as well as back up power. It is only maybe a year old and my GC2 batteries no longer seem like they want to charge fully and they drain when not receiving a charge. This just recently started happening. I got a small refrigerator that is only pulling 55 watts and it can't seem to handle it. I plugged the refrigerator in and it worked, but the battery got down to about 25% so I unplugged it. It has been unplugged for about a week now with no draw on the batteries, but it still won't get up to a full charge. I only have 2 GC2 batteries wired up to make 1 12 volt. They are rated for 105 minutes at 75 amps. I'm not sure how that equates to watts. All of the math conversions confuse me. I have 2 panels producing 175 watts each going into an mppt charge controller and a 45 watt harbor freight kit both charging those batteries. I also have a 2000/4000 watt inverter. Any help you all can give me is greatly appreciated!

[Mike90250]

To quote another "Oh Dear". Headline: Batteries murdered again.

You don't have nearly enough solar PV to recharge the batteries in the short winter days. With weeks of deficit charging, the batteries have gotten sulfated, finally now to the point they are useless.

Fridge 55W x 24 hr =1320 wh
350w PV x 3 hr sun = 1050wh x.75% eff = 787Wh harvested
HF panels =0
2000w inverter idle loss 20w x24 = 480wh
and a bunch of other losses

you are consuming 2x as much as your harvest. Sorry, turn the fridge off, and after a week of sunny days, your batteries may finally charge enough to test them with a load tester.

[MikeA]

To quote another "Oh Dear". Headline: Batteries murdered again.

You don't have nearly enough solar PV to recharge the batteries in the short winter days. With weeks of deficit charging, the batteries have gotten sulfated, finally now to the point they are useless.

Fridge 55W x 24 hr =1320 wh
350w PV x 3 hr sun = 1050wh x.75% eff = 787Wh harvested
HF panels =0
2000w inverter idle loss 20w x24 = 480wh
and a bunch of other losses

you are consuming 2x as much as your harvest. Sorry, turn the fridge off, and after a week of sunny days, your batteries may finally charge enough to test them with a load tester.

I have had the refrigerator and inverter unplugged now for a week. What else could be causing the battery to lose power? Why don't the HF panels contribute any power? Should I disconnect the batteries from PV and try to charge them with a battery charger to see if they will charge fully? It got up to 76% yesterday, reading 14.1 volts on the battery, but dropped down to 43% fairly rapidly once the sun started to go down. Again, this was with nothing running so I'm pretty confused as to what is causing the drain. Thank you for your feedback.

[Sunking]

I have had the refrigerator and inverter unplugged now for a week. What else could be causing the battery to lose power?

Because they have sulfated from abuse or deficit charging. In other words your batteries are toast and need replaced. They are not loosing power because they are already dead and cannot store any energy. Classic symptom of a sulfated battery is you put them on a charger, and charge shuts off because they are fooled into thinking the battery is charged up. Put a load on the battery and the voltage crashes immediately. Sound familiar? There is no fixing a dead sulfated battery.

[MikeA]

Because they have sulfated from abuse or deficit charging. In other words your batteries are toast and need replaced. They are not loosing power because they are already dead and cannot store any energy. Classic symptom of a sulfated battery is you put them on a charger, and charge shuts off because they are fooled into thinking the battery is charged up. Put a load on the battery and the voltage crashes immediately. Sound familiar? There is no fixing a dead sulfated battery.

Ok. So how did that happen? I definitely don't want this to happen to my next batteries. Is it from overcharging? I rarely ever have a load on the batteries. I only had the refrigerator plugged in for 2 days. If so, shouldn't the charge controller prevent that?

[russ]

From what Mike90250 posted - "you are consuming 2x as much as your harvest. Sorry, turn the fridge off, and after a week of sunny days, your batteries may finally charge enough to test them with a load tester."

[SunEagle]

Ok. So how did that happen? I definitely don't want this to happen to my next batteries. Is it from overcharging? I rarely ever have a load on the batteries. I only had the refrigerator plugged in for 2 days. If so, shouldn't the charge controller prevent that?

The charge controller only prevents you from over charging your batteries it does not prevent you from over discharging them.

You mention that your batteries are rated for 75amps at 105minutes but not the AH rating. Most deep cycle batteries have an Amp Hour rating for 20 hours. With that 55watt frig and that 2000watt inverter your batteries should have a rating greater than 500Ah. I would suspect your batteries are much smaller in size and easily got drained by that refrigerator.

You also mentioned you have two solar pv systems. The 350watt with MPPT charger and that HF 45watt system both connected to the same battery system. The HF system is not doing much of anything and may even be interfering with your larger wattage pv system. You also did not mention what model MPPT charger you have and while it might say MPPT it might really be a PWM type.

The biggest issue is that you are using way more watt hours than you are generating. Having a little charging and a small AH battery bank with the refrigerators daily watt hour load is probably a good reason the batteries have been over discharged and did not getting enough charge from the pv system.

You can try what the others have suggested and try charging you batteries without the refrigerator plugged in and with only the 350 watt system. Or maybe use a good battery charger to see if you can EQ them and get them working again.

My guess is that they have been sulfated and will not hold enough charge for even a small wattage load.

[Sunking]

Ok. So how did that happen?

Already told you why: "Deficit Charging". Like money if it cost you $10 a day to live and you only make $5 per day you are done. You do not have enough panel wattage to support the load and your battery. You have golf cart batteries which tells us they are 6 volt 220 AH batteries. With 2 in series makes 12 volts. You made several mistakes and it started when you bought your first peice of equipment and did not match anything you intended to do.

Fist step is determine your daily watt hour usage. You did not do that.
Next is location to determine Solar Insolation in Sun Hours so you can determine what wattage the power is required under worse case of winter.
Next is determine battery capacity based on a 5 day running load.
Next determine maximum connected load to find right inverter size.

Then it is time to buy equipment to work with each other. Here is an example for you. Let's say you want to run a fridge year round in Kansas City. The refrigerator like yours consumes 55 watts x 24 hours = 1320 Amp Hours. You now have all the information to design a system.

For a solar panel to generate 1320 wh per day means the panels must produce 1980 wh if using a MPPT charge controller, or 2640 wh if using PWM like you have. So lets's use PWM. In KCY during the months of Dec/Jan you receive 3 Sun hours. So panel wattage = [Daily Watt Hours x 2] / Sun Hours = 2640 watt hours / 3 hours = 880 watts. FWIW if using MPPT you would need 660 watts.

At 880 watts you can run either 12 or 24 volt battery. 24 volt is less expensive. To find battery capacity you need 5 day reserve or 5 x 1320 wh = 660 watt hours. To find battery amp hour capacity = Watt Hours / Battery Voltage. So if you select 24 volts you would need 6600 wh / 12 volts = 550 AH, or 225 AH if using 24 volt battery. You only only have half that much capacity.

Next is charge controller size. If you use PWM you have to use expensive battery panels operating at 17 volts and all in parallel. 880 watts @ 17 volts = 52 amps. If you use a MPPT controller you can use inexpensive Grid Tied panel wire in series and with 660 watts generates the same 52 amps.

Lastly is inverter size. As a general rule inverter size should be no larger than panel wattage, but that does not mean you go off and buy the largest inverter you can because inverters are not 100 efficient. Inverters run at max efficiency at or near their full power rating. You only have a 55 watt load, so you would be looking for around 100 to 200 watts. You did not do that. You bought a 2000 watt inverter and that inverter just sitting there with nothing connected can use up to 100 watts doing nothing. No you turn on your fridge and at 55 watts the inverter efficiency is very low like 50%. So you end up taking 200 watts off the batteries to only be utilizing 55 watts, You are using 4 times more power than you think which ate your battery alive.

So as you can see, you have to start all over with all new stuff. You might be able to reuse a panel, but everything else needs replaced and upgraded.

Read this thread as it will walk you through the process step by step. When you are donne with that read these threads:

Battery to Inverter Sizing
So You Want To Go Off-Grid
How Many Batteries

Once you have read all 4 you will then be able to determine what you need and if you really want to do this or not. My guess in NOT.

[MikeA]

Already told you why: "Deficit Charging". Like money if it cost you $10 a day to live and you only make $5 per day you are done. You do not have enough panel wattage to support the load and your battery.

I understand the deficit charging explanation. I only had the refrigerator plugged in for 2 days though. I just bought it. Before that, I didn't really run anything off the system. Could running it low 1 time destroy the batteries? That's what I'm having a hard time believing. Up until tried using the refrigerator, the batteries never got drained down low at all.

[MikeA]

The charge controller only prevents you from over charging your batteries it does not prevent you from over discharging them.

You mention that your batteries are rated for 75amps at 105minutes but not the AH rating. Most deep cycle batteries have an Amp Hour rating for 20 hours. With that 55watt frig and that 2000watt inverter your batteries should have a rating greater than 500Ah. I would suspect your batteries are much smaller in size and easily got drained by that refrigerator.

You also mentioned you have two solar pv systems. The 350watt with MPPT charger and that HF 45watt system both connected to the same battery system. The HF system is not doing much of anything and may even be interfering with your larger wattage pv system. You also did not mention what model MPPT charger you have and while it might say MPPT it might really be a PWM type.

The biggest issue is that you are using way more watt hours than you are generating. Having a little charging and a small AH battery bank with the refrigerators daily watt hour load is probably a good reason the batteries have been over discharged and did not getting enough charge from the pv system.

You can try what the others have suggested and try charging you batteries without the refrigerator plugged in and with only the 350 watt system. Or maybe use a good battery charger to see if you can EQ them and get them working again.

My guess is that they have been sulfated and will not hold enough charge for even a small wattage load.

I will they unplugging the Harbor Freight system to see if that helps. I believe the batteries are 215 or 220 amp hours if i remember correctly. I will look up the charge controller info when I get home. I will definitely not usr the refrigerator out there from now on. I just got it though and only ran the batteries low the one time so I'm hoping they aren't ruined. Thanks for the response.

[Sunking]

I understand the deficit charging explanation. I only had the refrigerator plugged in for 2 days though. I just bought it. Before that, I didn't really run anything off the system. Could running it low 1 time destroy the batteries? That's what I'm having a hard time believing. Up until tried using the refrigerator, the batteries never got drained down low at all.

No you should be OK, but you need to put the batteries on a commercial AC charger ASAP.

[MikeA]

No you should be OK, but you need to put the batteries on a commercial AC charger ASAP.

I will definitely try that then. Thank you!

[Sunking]

You are welcome glad I could help. You could do it with your solar but it would take several days and cannot reverse the damage because the charge current is to low. To dissolve soft sulfate crystals needs to up at least C/12 and preferable C/8, where C = the battery AH capacity. GC2 6 volt batteries are around 220 AH so C/8 = 220 / 8 = 27.5 amps.

That also jives with matching panels and batteries together. Example a 12 volt 220 AH battery needs a minimum C/12 charge current up to C/8 (18 to 28 amps) If using a MPPT controller means a minimum panel wattage of 230 watts and no larger than 360 watts. That is how we can tell real darn quick when there is a mismatch. FWIW if using PWM that goes up to a minimum of 320 watts up to 500 watts. You have PWM right? See a problem yet? I do instantly.

[MikeA]

You are welcome glad I could help. You could do it with your solar but it would take several days and cannot reverse the damage because the charge current is to low. To dissolve soft sulfate crystals needs to up at least C/12 and preferable C/8, where C = the battery AH capacity. GC2 6 volt batteries are around 220 AH so C/8 = 220 / 8 = 27.5 amps.

That also jives with matching panels and batteries together. Example a 12 volt 220 AH battery needs a minimum C/12 charge current up to C/8 (18 to 28 amps) If using a MPPT controller means a minimum panel wattage of 230 watts and no larger than 360 watts. That is how we can tell real darn quick when there is a mismatch. FWIW if using PWM that goes up to a minimum of 320 watts up to 500 watts. You have PWM right? See a problem yet? I do instantly.

I'm not quite sure if I'm understanding your second paragraph. I don't know what FWIW and PWM stand for. I have an MPPT charge controller. It is a tracer 3215rn. So should GC2 batteries be ok with that set up or should I look at possibly doing different batteries when I replace them?

[SunEagle]

I'm not quite sure if I'm understanding your second paragraph. I don't know what FWIW and PWM stand for. I have an MPPT charge controller. It is a tracer 3215rn. So should GC2 batteries be ok with that set up or should I look at possibly doing different batteries when I replace them?

FWIW = "For What It's Worth"

PWM = Pulse Width Modulation (lower efficient charger) It works by using the amount of amps your panels produce and charges the batteries at that amperage. (amps in = amps out)

That Tracer 3215rn is an 30Amp MPPT type charger and uses the total panel wattage divided by your battery voltage to generate charging amps (watts in = watts out). So with 350watts of panels and a 12v battery ( 350w /12v = 29.2amps.)

So that Tracer should work just fine with those 2 x 175 watt panels and is more than enough to charge a 220Ah 12volt battery. If you battery Ah is less than 220 then you might charge them a little too fast but I think the issue is that the batteries have been over discharged and now need to be returned to health.