Battery Lost Power too quickly

[Koreypre]

I have a new shed solar system I set up in the last 90 days. I have a Grape Solar 200-Watt solar panel, a 40 AMP Grape Solar charge controller, a 3000 W Renogy inverter (upgraded from my original 1000 W) and a Renogy battery monitor. The battery is a 12V Renogy 100AH gel battery. I have a new LED motion sensor light on the interior that only comes on when I go inside and an LED lamp on the exterior which goes on at dark and off at dawn. I also have a power strip plugged in inside the shed with a router plugged in. I don't think i am using my power at all. The system worked great for 60+ days. A week or so ago i went into the shed and the battery monitor was showing no charge left. Previously this thing would always show 99-100% charge any time i would go in there. It would then drop only if i was in the shed for an extended period of time and the light was on - but it would barely drop. Any idea as to why the battery would suddenly dissipate all of the sudden? The cables all seem tight and the controller shows it's getting power from the panel. All parts were new upon install including the battery.

I am racking my brain to figure it out. It's frustrating when it works for a period and suddenly is acting weird after a short period. Here are a few things which may or may not have impacted the situation:

1) I replaced the inverter from a 1K W to 3K - same brand of Renogy but basically a swap out. Prior to to swapping i tried plugging in a saw that clearly needed more power than my 1K inverter could supply - hence the swap out. That was the only time I tried running that saw and then i swapped out the inverters. I guess this could've caused some issue but i swapped the inverters and everything seemed fine. That was maybe 3-4 weeks ago and about 2-3 weeks after that is when i started having battery issues.

2) I read that the Renogy Battery i have has a max charge current of 30A. The charge controller is a 40A charge controller. I am not sure if that impacts anything over time? The charge controller correctly detected the battery type as gel. I don't think i needed to change any other settings as i believed they were all accurate.

3) It is going into summer time and the shed is heating up during the day. I read that heat can impact batteries but frankly it hasn't been that hot and the battery went from being fine to not fine in a week or so which leads me to believe it's something other than the temp affecting the battery.

I have provided a few pics of my setup below. Any help or ideas would be greatly appreciated. Thank you!

 

[time2roll]

Has the function of the monitor been verified? What is the actual battery voltage?

 

[Koreypre]

Has the function of the monitor been verified? What is the actual battery voltage?

Monitor seemed to be fine when set up. I tested the battery today and it was a12.2- the same as showed up on the charge controller. As soon as I plug in my LED light it drops to like 12 or 12.1V

 

[mikefitz]

Comments.
Your battery cannot supply enough current for your 3000 watt inverter if you have significant loads
The 200 watt panel will deliver a maximum current under ideal conditions around 16 amps.
The Renogy inverter has a static current drain of 1.5 amps, 36 watt hours per day.
Although you have a 100 Ah gel battery it's usable capacity will be less.
A Gell battery cannot supply high currents for long periods.
A GEL battery has long recharge times.
Your panel seems to be in the shade, may just be the picture.

I suspect the the battery is not being fully charged and the inverter load is draining the battery.

Advise disconnecting the inverter and allowing the battery to fully charge. The battery needs to see a charge voltage reaching around 14 volts, and being held in the absorbtion , constant voltage, stage for several hours.
Once charged, with no load or charge, after a resting period should read around 13 volts.

Mike

 

[Koreypre]

Comments.
Your battery cannot supply enough current for your 3000 watt inverter if you have significant loads
The 200 watt panel will deliver a maximum current under ideal conditions around 16 amps.
The Renogy inverter has a static current drain of 1.5 amps, 36 watt hours per day.
Although you have a 100 Ah gel battery it's usable capacity will be less.
A Gell battery cannot supply high currents for long periods.
A GEL battery has long recharge times.
Your panel seems to be in the shade, may just be the picture.

I suspect the the battery is not being fully charged and the inverter load is draining the battery.

Advise disconnecting the inverter and allowing the battery to fully charge. The battery needs to see a charge voltage reaching around 14 volts, and being held in the absorbtion , constant voltage, stage for several hours.
Once charged, with no load or charge, after a resting period should read around 13 volts.

Mike

Thanks for the response Mike. The panel is in full sun for 6+ hours a day so I don’t think that’s the issue. The pic was from later in the day. I haven’t put any load on the battery other than one LED light, the inverter, and a Wi-Fi booster. I did plug in a saw and turned on briefly but I didn’t even cut anything. It was always running full at 13 or so volts. I shut off the inverter a few hours ago and the voltage has basically been at 12.2V with no bump up. As soon as I turn the inverter on it knocks the battery to 11.9-12 which seems strange to me. It seems like a big drop.

 

[time2roll]

I shut off the inverter a few hours ago and the voltage has basically been at 12.2V with no bump up.

That statement indicates no solar is getting to the battery. Does the meter show amps going into the battery?

 

[Koreypre]

That statement indicates no solar is getting to the battery. Does the meter show amps going into the battery?

The charge controller shows the arrow as if power is coming in however the battery monitor shows a 0% charge and doesn’t seem to move off that.

 

[Koreypre]

The charge controller shows the arrow as if power is coming in however the battery monitor shows a 0% charge and doesn’t seem to move off that.

However My battery monitor does show + low level amps coming in +.5 or so - probably more in full sun

 

[time2roll]

Need to keep the inverter off until the battery is charged. 200w solar should produce 10 amps in good conditions. Half amp is not working.

 

[Koreypre]

Need to keep the inverter off until the battery is charged. 200w solar should produce 10 amps in good conditions. Half amp is not working.

Ok, thanks Tim. I’ll give that a try and monitor how many amps are coming in at full sun. The half amp was in full shade. I appreciate your input.

 

[Tim Tim]

Your 100Ah battery has approximately 50Ah capacity so if your inverter remained switched on and as Mike says uses 1.5A per hour then in 24 hours that is 36Ah. That is what you need to replace each day plus any additional power you use. Although your panel can produce 16A under ideal conditions the reality is that you may not even get close to that. It may be that you have actually gradually depleted the battery over a period of time.

Did you disconnect your solar controller to connect your new inverter? Generally the battery has to be connected to the solar controller first and then the panel. Try disconnecting and reconnecting the solar controller to the battery and then connect the panels.

When a load is applied to your battery you will see a voltage drop and this is normal, this is the terminal voltage. If you turn the load off and wait you will see the voltage climb after resting. Similarly if you charge a battery up and take a reading right away then take a reading a while later you will see the voltage has dropped.

In response to your question.
(1). Try disconnecting the solar controller and panels and reconnect battery first and then solar panel.
(2). You are not exceeding the charging current of 30A to your battery so you are ok there and you are not exceeding the 40A current which your controller can handle so you are ok there as well.
(3). From our photos you appear to have plenty of ventilation to your battery so no issues there. However, your inverter cables look a little thin. What gauge are they?

If you are running a power saw which may be 2400W that equates to approximately 240A @ 12V allowing for inefficiencies. Therefore for each minute you run it you will be taking approximately 4Ah of your battery capacity.

 

[sunshine]

I have a new shed solar system I set up in the last 90 days.

90 days ago....12 March..... Maybe those branches shading the panels in the photo had less leaves back in March?

The fact that there is a rather discharged 100ahr battery at the beginning of each day makes it rather impossible for the panel to reach anywhere near it's true capacity so all the above adverse figures should be even worse.
I guess there is a need to match panels with batteries in regard to resistance even when a mppt cc is used when such a mismatch is present.

Solution....add another panel!

 

[mikefitz]

You need more battery and more solar if you want to run a 3000 watt inverter. Fuses at the battery bank for safety and heavy duty cables for the inverter.
It's not practical to expect a 100 Ah GEL battery to power a 3000 watt inverter.

At least 4 off 100Ah GEL batteries in parallel, and lots more solar will be needed to run power tools.

Mike

 

[Koreypre]

You need more battery and more solar if you want to run a 3000 watt inverter. Fuses at the battery bank for safety and heavy duty cables for the inverter.
It's not practical to expect a 100 Ah GEL battery to power a 3000 watt inverter.

At least 4 off 100Ah GEL batteries in parallel, and lots more solar will be needed to run power tools.

Mike

Thanks Mike - good intel. I did just purchase a second 100 AH Gel battery. Hoping to maybe connect these 2 in parallel this weekend. So the cables I have are 10AWG. Are you thinking I need something heavier gauge? If so, what would you suggest?

I do have one Grape Solar 20A MC4 inline fuse (not pictured) as part of my system. Do you think this is sufficient? If not, what are you suggesting?

I guess I was hopeful that the 3000W inverter would give me the option to run the occasional power tool or other heavier application for when I may need some brief extra power when the power goes out but I didn’t realize it sucked a lot more power to keep on than my original 1000W. Probably the 1000W is sufficient 99% of the time.

 

[Koreypre]

90 days ago....12 March..... Maybe those branches shading the panels in the photo had less leaves back in March?

The fact that there is a rather discharged 100ahr battery at the beginning of each day makes it rather impossible for the panel to reach anywhere near it's true capacity so all the above adverse figures should be even worse.
I guess there is a need to match panels with batteries in regard to resistance even when a mppt cc is used when such a mismatch is present.

Solution....add another panel!

THanks Sunshine. I am adding a 2nd 100AH Gel in parallel. Hoping to do that this weekend. I guess my new 3000W inverter just pulls a lot more power to keep on than my 1000W and that’s the problem. I wanted the 3000W for the very occasional higher power needs but maybe it’s overkill. Looking to add 2 more 200W panels but they’re currently not in stock at Grape Solar.

 

[Koreypre]

Your 100Ah battery has approximately 50Ah capacity so if your inverter remained switched on and as Mike says uses 1.5A per hour then in 24 hours that is 36Ah. That is what you need to replace each day plus any additional power you use. Although your panel can produce 16A under ideal conditions the reality is that you may not even get close to that. It may be that you have actually gradually depleted the battery over a period of time.

Did you disconnect your solar controller to connect your new inverter? Generally the battery has to be connected to the solar controller first and then the panel. Try disconnecting and reconnecting the solar controller to the battery and then connect the panels.

When a load is applied to your battery you will see a voltage drop and this is normal, this is the terminal voltage. If you turn the load off and wait you will see the voltage climb after resting. Similarly if you charge a battery up and take a reading right away then take a reading a while later you will see the voltage has dropped.

In response to your question.
(1). Try disconnecting the solar controller and panels and reconnect battery first and then solar panel.
(2). You are not exceeding the charging current of 30A to your battery so you are ok there and you are not exceeding the 40A current which your controller can handle so you are ok there as well.
(3). From our photos you appear to have plenty of ventilation to your battery so no issues there. However, your inverter cables look a little thin. What gauge are they?

If you are running a power saw which may be 2400W that equates to approximately 240A @ 12V allowing for inefficiencies. Therefore for each minute you run it you will be taking approximately 4Ah of your battery capacity.

Thanks Tim. This was super helpful. Turning the inverter off had my battery back to full charge in a day or so. I didn’t realize bumping from the 1000W to the the 3000W inverter sucked a lot more power just keeping it in the on position. I was hoping I could upgrade to 3000W for the occasional time I needed a little more power but didn’t think it would affect anything else. I have purchased a 2nd 100AH Gel batter of the same kind and hoping to connect that this weekend. I eventually want to add 2 additional 200W panels but they are currently on back order. My cables are 10AWG. Do I need something greater? If so, what do you recommend? Secondly, someone else mentioned having fuse(s). I have one 20A fuse (not pictured) as part of the system. Will that suffice in your opinion? Are there any specific gauge cables to connect the batteries to each other? I appreciate the help!

PS - I think you were right about the incoming Amps cause it seems I am somewhere around 10 coming in during good conditions.

 

[Koreypre]

If I have a fully charged battery and a charge controller as part of the system, does anyone know if the Renogy battery monitor will only show limited input coming in (1A or so) during full sun because the charge controller is limiting this because the battery is already full? Thanks.

 

[camelCase]

That's right. Otherwise the batteries would be overcharged. A good solar charge controller regulates the current and voltage to avoid overcharging based on the type of battery.

BU-403: Charging Lead Acid

BU meta description needed...

batteryuniversity.com

 

[camelCase]

With a lot of solar systems the problem is under charging lead acid batteries as there is a limited number of sunny hours in a day versus the time it takes to fully charge the battery. Lead acid batteries can take several hours to charge the last 25% or so. The first 75% can actually take less time than the topping charge due to the chemistry of lead acid batteries. It's important to get them up to 100% on a regular basis or they degrade much more quickly.

 

[Koreypre]

With a lot of solar systems the problem is under charging lead acid batteries as there is a limited number of sunny hours in a day versus the time it takes to fully charge the battery. Lead acid batteries can take several hours to charge the last 25% or so. The first 75% can actually take less time than the topping charge due to the chemistry of lead acid batteries. It's important to get them up to 100% on a regular basis or they degrade much more quickly.

Thanks Camel. The whole solar thing is a learning process and it’s great to this forum as a resource. Really appreciate it!