Understanding Solar Controller

[Ktholin]

I recently upgraded my solar system by adding two more panels (now totaling 340 watts) and a Victron MPPT controller. I have a Bogart Engineering TM 2025 battery monitor and two Trojan T-125 6 volt batteries which are about 3 years old.

This morning my batteries were down to 46% (we use a lot of power running TV, furnace and fans). It has been clear and sunny all day. After 5 hours my batteries are only up to 52%. The victron controller is showing battery voltage of 13.88 V and a float charge (which I understand is a maintenance mode after the batteries have reached a full charge). My question is: why would the solar system be in a float mode when the batteries are so depleted? Why is there a discrepancy between the Victron voltage and the battery SOC? I checked the specific gravity of batteries which conforms the SOC.

Any thoughts on what, if anything, could be going on? I’m not happy with the performance of my system.

[pcskier]

1. The hydrometer test confirmed the 52% SOC?
2. What is the voltage of the batteries when fully charged and then rested for 20 or 30 minutes with no big loads on, and panels turned off if you have a switch (or wait till dark) to stop any charging. Should be around 12.7x volts, though at three years old, yours might be getting tired and not hold that voltage for very long.
3. Have you programmed the correct charge profile into your Victron charge controller for your specific batteries.
4. Yes, float mode is when the charge controller *thinks* the batteries are fully charged. Before getting there, they should show absorption and/or bulk charging of 14.x volts, before dropping into absorption.

It is possible that your batteries are worn out and simply not able to take a full charge any more. Three years is a decent service life for flooded cells.

With my Victron controller and BMV-712 monitor, both are programmed and synched to my specific battery specs, including synching the meter to 100% after I know the batteries are fully charged. But even then these monitors do a lot of 'guessing' on what 'percentage' the SOC is. Does the bogart monitor have the capability for you to input your battery specs in to it?

I focus on voltage, and actual ah used since the last charge, to get a sense of where the SOC of my batteries is.

[AirMiles]

Click on the "History" tab on the live Victron screen from the picture you posted. It will show what happened throughout the day and last several days. If you then click on that plus-like symbol on the top-left of the screen, you will see 30 days of history. This screen graphically displays the total watt-hours produced each day and the time spent in bulk mode, absorption mode, and float mode. I've attached a 30-day version of the history screen from my Victron solar controller. If you click on an individual day on the history screen, it will display how many minutes were spent in each mode. This will give you a better idea of what your solar controller is doing throughout each day rather than the real-time status screen that you posted that just tells the current mode, current solar production and current battery voltage.

[GMFL]

What size Victron MPPT do you have installed. What’s your programmed charge profile setting.

The Victron “thinks” the batteries are at 13.88 volt.... What is the voltage of the batteries.
How is the controller wired into the system. Straight to the batteries? Through the shunt? Through the DC distribution bar?
These answers will help.

[Ktholin]

Originally Posted by pcskier

1. The hydrometer test confirmed the 52% SOC?
2. What is the voltage of the batteries when fully charged and then rested for 20 or 30 minutes with no big loads on, and panels turned off if you have a switch (or wait till dark) to stop any charging. Should be around 12.7x volts, though at three years old, yours might be getting tired and not hold that voltage for very long.
3. Have you programmed the correct charge profile into your Victron charge controller for your specific batteries.
4. Yes, float mode is when the charge controller *thinks* the batteries are fully charged. Before getting there, they should show absorption and/or bulk charging of 14.x volts, before dropping into absorption.

It is possible that your batteries are worn out and simply not able to take a full charge any more. Three years is a decent service life for flooded cells.

With my Victron controller and BMV-712 monitor, both are programmed and synched to my specific battery specs, including synching the meter to 100% after I know the batteries are fully charged. But even then these monitors do a lot of 'guessing' on what 'percentage' the SOC is. Does the bogart monitor have the capability for you to input your battery specs in to it?

I focus on voltage, and actual ah used since the last charge, to get a sense of where the SOC of my batteries is.

Thanks for your response.

1. Yes the hydrometer indicated about a 52% SOC. Also my battery monitor indicated this level.

2. I’ll try to measure the voltage after the conditions you recommend. However, it may take me a day or so to get to this.

3. I am using the #2 preset on the controller which was recommended.

4. Initially the controller indicated a bulk charge. I believe it was 14.4 V. After a couple of hours it went into float mode.

Also, the Bogart monitor does allow one to program in the battery specs.

I’m wondering now about the batteries. I had the solar running for 4 hours this morning and brought the batteries from 46 to 52%. I then switched to my generator which has now been running for 4.5 hours and the battery is only up to 64%. Seems to me it should be more charged after all that.

[Ktholin]

Originally Posted by AirMiles

Click on the "History" tab on the live Victron screen from the picture you posted. It will show what happened throughout the day and last several days. If you then click on that plus-like symbol on the top-left of the screen, you will see 30 days of history. This screen graphically displays the total watt-hours produced each day and the time spent in bulk mode, absorption mode, and float mode. I've attached a 30-day version of the history screen from my Victron solar controller. If you click on an individual day on the history screen, it will display how many minutes were spent in each mode. This will give you a better idea of what your solar controller is doing throughout each day rather than the real-time status screen that you posted that just tells the current mode, current solar production and current battery voltage.

Thanks for that. I have attached a 30 day chart as you suggest. We have been camping for 4 days. Seems to me it’s been in a float mode for a long time despite the batteries not being close to fully charged. Note that I switched to my generator each day around noon because of the slow charging progress which may confound things.

[Ktholin]

Originally Posted by GMFL

What size Victron MPPT do you have installed. What’s your programmed charge profile setting.

The Victron “thinks” the batteries are at 13.88 volt.... What is the voltage of the batteries.
How is the controller wired into the system. Straight to the batteries? Through the shunt? Through the DC distribution bar?
These answers will help.

I have a 100/30 controller using the #2 preset.

The controller is not wired directly to the batteries. I’m not 100% sure if it is through the shunt or DC distribution bar. I’ll check in the morning.

[AirMiles]

Originally Posted by Ktholin

Thanks for your response.

1. Yes the hydrometer indicated about a 52% SOC. Also my battery monitor indicated this level.

2. I’ll try to measure the voltage after the conditions you recommend. However, it may take me a day or so to get to this.

3. I am using the #2 preset on the controller which was recommended.

4. Initially the controller indicated a bulk charge. I believe it was 14.4 V. After a couple of hours it went into float mode.

Also, the Bogart monitor does allow one to program in the battery specs.

I’m wondering now about the batteries. I had the solar running for 4 hours this morning and brought the batteries from 46 to 52%. I then switched to my generator which has now been running for 4.5 hours and the battery is only up to 64%. Seems to me it should be more charged after all that.

I don't like #2 preset for your batteries because its really configured for AGM batteries. It only charges at 14.4V but Trojan recommends 14.82V. Preset #2 float mode is 13.8V but Trojan recommends 13.5V. Source: https://www.trojanbattery.com/pdf/da...ata_Sheets.pdf and https://www.victronenergy.com/upload...R-DE-ES-SE.pdf . I would create a custom program that matches the recommended charging specifications for your Trojans. Trojan recommends a maximum absorption time of four hours which matches #2 Preset.

I actually was surprised by Trojan's recommended charging parameters. My Duracell EGC2 6V golf cart batteries use way higher voltage recommendations and longer absorption time. So I definitely needed a custom program. I thought your Trojans would have been similar. Better to go look up the specs than assume anything. My batteries have a 12 hour maximum absorption time, so as you can see my absorption times are much longer than yours. My batteries use a 14.95V absorption level, if I recall correctly, so my bulk stage lasts much longer. My float mode is 13.95V so Preset #2 would not work at all with my batteries.

After looking at your history chart, it appears to me that the 14.4V Preset #2 is the problem. Your batteries are only getting to 50% charged with that too low 14.4V bulk stage and absorption voltage. Then absorption mode is being limited to a few hours which isn't long enough to add much more charge, and then it goes into float mode for the rest of the day with the batteries at 60% state of charge. This is similar to how the Airstream factory shore power converter charges batteries and why I believe there are so many premature battery failures with the factory shore power converter.

I should add, then you are using that lousy shore power converter which charges similarly to your solar charger on preset #2 so you aren't getting your batteries past 60%. The factory shore power converter charges at 13.8V. It would take days and days to get your batteries fully charged at that voltage. Mine with a 13.95V float would never get fully charged!

[pcskier]

Originally Posted by Ktholin

Thanks for your response.
I’m wondering now about the batteries. I had the solar running for 4 hours this morning and brought the batteries from 46 to 52%. I then switched to my generator which has now been running for 4.5 hours and the battery is only up to 64%. Seems to me it should be more charged after all that.

Originally Posted by Ktholin

Thanks for that. I have attached a 30 day chart as you suggest. We have been camping for 4 days. Seems to me it’s been in a float mode for a long time despite the batteries not being close to fully charged. Note that I switched to my generator each day around noon because of the slow charging progress which may confound things.

Attachment 360657

What did the bogart show as the voltage with the generator running (assuming you plugged your genny into the trailer shore power plug and you are charging via the on-board converter-charger.) I am leaning toward failing batteries if they are truly only at 64 percent after five hours of sunshine on solar and 4-5 hours on the generator. (Assuming furnace hasn't been running non-stop or other big loads? Have you been using much power all day while also charging?)

Might be worth getting the batteries load tested at this point and see what their health truly is. When you go to bed tonight and the batteries are rested for a bit (no charging, no big loads) see what the bogart says the voltage and percentage charge is. I'll be curious to correlate the two to see if the meter is reporting the charge accurately. 50 percent state of charge would be down around 12-12.1 volts, give or take, depending on temperature and battery health. Do the same in the morning (without big loads like furnace running). Report back with those numbers.

One other possibility: the bogart was 'synched' to a 100 percent SOC when not in a 'rested' state, but while receiving 13.5 volts from the charge controller, or the charger/converter, when it was set up. Any chance of that? It the batteries were under charge when the synch was done, the bogart might think that whatever that voltage was, is the 100% voltage, say, 13.5V--when in fact the batteries would have shown 12.7 or 12.8 once rested for a half hour or so.

[AirMiles]

I really don't think the batteries are bad. Trojan T125's (or T105's) are really difficult to kill. They can take massive abuse and survive. I know because I once had both of the above in a golf cart that I'd run until it stopped and then recharge consistently. The T105s lasted for twelve years and I sold the golf cart after years of abusing the replacement T125s. The golf cart sat for years uncharged with the T105s before I bought it and started abusing the batteries. Trojan T1xx batteries are not like the typical RV Deep Cycle battery that you kill once and they are done. Duracell EGC2s are built very similarly to the T1xx's so I expect similar performance from mine. I've been abusing my EGC2's for 250 days of use and 500 days of storage so far and they still test and perform as new. From my experience, I'd give the batteries the benefit of the doubt at this point and start with customizing the Victron solar charging parameters to match Trojan's charging specifications. I'll bet those tough-to-kill Trojans and that awesome Victron Solar Controller will start working perfectly!

[sgschwend]

Is not the 30 day graph showing the solar charging per day? If so why is the solar charger results so low? Is it because the solar is offline when the gen set is running?

Sounds like you would use over 1 kWh per day. Do you have a record of you daily load?

tks,

[Ktholin]

Originally Posted by pcskier

What did the bogart show as the voltage with the generator running (assuming you plugged your genny into the trailer shore power plug and you are charging via the on-board converter-charger.) I am leaning toward failing batteries if they are truly only at 64 percent after five hours of sunshine on solar and 4-5 hours on the generator. (Assuming furnace hasn't been running non-stop or other big loads? Have you been using much power all day while also charging?)

Might be worth getting the batteries load tested at this point and see what their health truly is. When you go to bed tonight and the batteries are rested for a bit (no charging, no big loads) see what the bogart says the voltage and percentage charge is. I'll be curious to correlate the two to see if the meter is reporting the charge accurately. 50 percent state of charge would be down around 12-12.1 volts, give or take, depending on temperature and battery health. Do the same in the morning (without big loads like furnace running). Report back with those numbers.

One other possibility: the bogart was 'synched' to a 100 percent SOC when not in a 'rested' state, but while receiving 13.5 volts from the charge controller, or the charger/converter, when it was set up. Any chance of that? It the batteries were under charge when the synch was done, the bogart might think that whatever that voltage was, is the 100% voltage, say, 13.5V--when in fact the batteries would have shown 12.7 or 12.8 once rested for a half hour or so.

I’m leaning toward bad batteries now. In addition to running the solar, I also ran the generator for about 5 hours. There was very little increase in the charge. Battery went from 52 to 64%.

Last night we only ran the heater intermittently. This morning the Victron was showing 11.24 V and the Bogart Trimetric showed 11.9V and 40%. I measured the voltage at the battery at 11.87. So, the batteries were very depleted. I assume a bad battery would be difficult to charge and would deplete quickly which is what mine appear to be doing.

[AirMiles]

The only way to test a battery is to have it fully charged. The parameters on your Victron were not set to fully charge your batteries. Your stock Airstream converter's charging parameters, always 13.8V, are even worse for fully charging your batteries. I would not give up on the batteries until you put the correct charging parameters into the Victron and give it a couple of good sunny days to see what happens. Maybe your batteries are bad. I don't know how long you've been using them in a half-dead state or if they've spent considerable time completely dead. But my experience with abused Trojan's says to give them a couple of days with the correct charging parameters and see what happens.

[Ktholin]

Originally Posted by AirMiles

The only way to test a battery is to have it fully charged. The parameters on your Victron were not set to fully charge your batteries. Your stock Airstream converter's charging parameters, always 13.8V, are even worse for fully charging your batteries. I would not give up on the batteries until you put the correct charging parameters into the Victron and give it a couple of good sunny days to see what happens. Maybe your batteries are bad. I don't know how long you've been using them in a half-dead state or if they've spent considerable time completely dead. But my experience with abused Trojan's says to give them a couple of days with the correct charging parameters and see what happens.

Ok. I’ll let them charge for a few days with the correct parameters and get back. BTW I have upgraded my stock charger/converter to a multistage Progressive Dynamics so that is not the issue.

[Ktholin]

Originally Posted by AirMiles

The only way to test a battery is to have it fully charged. The parameters on your Victron were not set to fully charge your batteries. Your stock Airstream converter's charging parameters, always 13.8V, are even worse for fully charging your batteries. I would not give up on the batteries until you put the correct charging parameters into the Victron and give it a couple of good sunny days to see what happens. Maybe your batteries are bad. I don't know how long you've been using them in a half-dead state or if they've spent considerable time completely dead. But my experience with abused Trojan's says to give them a couple of days with the correct charging parameters and see what happens.

OK, so this morning the controller showed the batteries being charged in the bulk mode at about 145 watts. I didn't take a screen shot. By 10:30 am it was virtually not charging at all and showing float mode. It has stayed like this ever since. Recall I changed the charging parameters. I can't think of anything else but the batteries. I also looked up that they are 4 years old. Here is the screen shot.

[AirMiles]

Originally Posted by Ktholin

OK, so this morning the controller showed the batteries being charged in the bulk mode at about 145 watts. I didn't take a screen shot. By 10:30 am it was virtually not charging at all and showing float mode. It has stayed like this ever since. Recall I changed the charging parameters. I can't think of anything else but the batteries. I also looked up that they are 4 years old. Here is the screen shot.

Attachment 360705

This just doesn't seem right to me. What's the resting voltage of the batteries? Are they really charged? Were you boondocking overnight and using power? Were you connected to shore power overnight? Maybe the batteries are dead, but then I think the solar controller would not get to float so easily.

How were the batteries before you installed the new solar controller? If they worked good before adding the solar controller, I don't think they were damaged in the last several days based on your history screen shot. I'm still not convinced the batteries are bad. The next thing I would do is to connect to shore power for 24 hours to see if your PD4655 will charge the batteries to know for sure its not a problem with the solar controller. But you know the history of your batteries better than we do. Let us know if new batteries solves your problem so we know what to expect when our batteries go bad.

[fran&frank]

I agree with AirMiles, you need to plug in to shore power and attempt to fully charge your batteries with your converter or a battery charger to confirm your batteries are OK. Then, if the batteries behave as expected, you can move on to diagnosing the problem with your solar charging.--Frank

[Ktholin]

Originally Posted by AirMiles

This just doesn't seem right to me. What's the resting voltage of the batteries? Are they really charged? Were you boondocking overnight and using power? Were you connected to shore power overnight? Maybe the batteries are dead, but then I think the solar controller would not get to float so easily.

How were the batteries before you installed the new solar controller? If they worked good before adding the solar controller, I don't think they were damaged in the last several days based on your history screen shot. I'm still not convinced the batteries are bad. The next thing I would do is to connect to shore power for 24 hours to see if your PD4655 will charge the batteries to know for sure its not a problem with the solar controller. But you know the history of your batteries better than we do. Let us know if new batteries solves your problem so we know what to expect when our batteries go bad.

That's a good suggestion to charge with the PD charger for a prolonged period. I will try to do that. Remember, however, that I did run my generator for at least 5 hours and I felt it was not charging as it should. I'll report back when I learn something.

[Ktholin]

OK, so you were right. I removed the batteries and charged them for 24 hours, let them rest and checked voltage and specific gravity. After 24 hours off the charger the voltage is 12.87 and specific gravity 1.275. Batteries are good.

So, now I have to figure out why the controller is switching to the float mode before fully charged. Either the controller is bad or the wiring is wrong. When I replaced the previous controller (which was installed by someone else), i used the existing wiring. The wires to the battery are connected to the DC distribution panel. I'm thinking of connecting the output wires directly to the battery. Any suggestions at this point?

[lsbrodsky]

There really is no need to connect the solar controller directly to the battery. Is yours connected to the distribution panel with the fuses or the DC bus bars? The original Airstream factory solar goes to the DC bus bars but you siad someone else installed your controller. There is probably some voltage drop between the distribution panel and the bus bars, but not much. In any event, the bus bars are a perfectly adequate place for solar output. Make sure your parameters are set properly on the controller and try it all again with healthy batteries. My 5 cents worth.
Larry