Solar regulator not temperature sensing the battery (1 Viewer)

[sallylillian]

I have an interesting situation which I am trying to get my head around. I have a CBE PRS240 regulator which is set at 13.8 for float. I have a Victron Multiplus which is set at the same float voltage but adjusted for temperature through the temp sensor connected to the hab battery bank. Now in Spain we have temps in the high 20's during the day. My Victron is sensing the temp and adjusting the float voltage down to nearer 13.3-4. The Victron control panel shows it is on float not absorption mode, which is correct. BUT the CBE because it is not battery temp sensing so sticks with its hell or high water 13.8 requirement. The battery is low as far as it is concerned and continues at its absorption voltage 14.3. I have not seen it move to float. Any thoughts on what seems on the face of it to be a flaw in the system setup?

 

[dave newell]

Yes it is a flaw in your system setup, running two separate solar regs to the same battery bank is always going to lead to conflict between them. The CBE unit is working as designed as it is not temperature adjusted. Can I ask why you have two separate solar regs?

D.

 

[funflair]

Hi Dave

I think the Victron multi plus is mains battery charger and inverter unit so not actually handling the solar.

Martin

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[funflair]

I imagine there will always be conflict when one charger is temperature sensing and one is not, as the battery temperature increases the sensing charger will cut back the voltage and effectively just shut down and leave the work to the non sensing one, I have two solar regulators feeding one battery bank and one is always more dominant causing the other one to cut back on the amps that it passes to the battery bank. Of course we also have a mains operated battery charger but that is switched off most of the year as the solar can keep up with our demands.

Whether or not the CBE is working correctly is possibly another question.

Martin

 

[dave newell]

Hi Dave

I think the Victron multi plus is mains battery charger and inverter unit so not actually handling the solar.

Martin

Aah I hadn't realised that. It is still obvious that if the one charger is temperature compensated and the other isn't then the one that isn't will continue to charge up to the higher voltage.

D.

 

[sallylillian]

Thank you Martin and Dave. Martin has it right on the role of each piece of kit. My concern is the voltage rather than the amps. Excessive absorption voltage (14.4) when it should be float is worrying from a battery longevity point. Is it possible to temperature sense the CBE solar regulator? I cannot see any reference in the manual, if not are there regulators that do?

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[funflair]

Hi Michael

I have been searching the net and cant find any reference to adding temperature sensing to the PRS 240 so I think that is a NO.

Is it that the solar regulator is not getting the batteries to a high enough voltage to go into float charge or is the regulator lighting up to indicate "float" but still putting out 14.4v. What battery capacity and solar capacity do you have.

Martin

 

[EssexBoy]

Or could it simply be that the heat generated by the working charger has fooled the temp sensing one into switching off prematurely?

 

[sallylillian]

Hi Michael

I have been searching the net and cant find any reference to adding temperature sensing to the PRS 240 so I think that is a NO.

Is it that the solar regulator is not getting the batteries to a high enough voltage to go into float charge or is the regulator lighting up to indicate "float" but still putting out 14.4v. What battery capacity and solar capacity do you have.

Martin

Martin,
The batteries are Varta and I have 495 amps. The regulator has never shown the green float light, always the charge yellow light. The Victron panel is showing float charge light. The CBE main panel has the voltage rising as the sun has got up. Early this morning 13.3 volts now at 14 volts, been rising with the sun. This suggests that the solar thinks the batteries are not fully charged?
The Victron has an absorption voltage of 14.6 set, but Varta spec is 14.8. I spoke with Varta about this anomaly and they said not a problem just will take longer?? I am wondering if the batteries are not getting full enough, and the solar is sensing this? Any thoughts?

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[funflair]

495 is a lot of battery, the Victron will essentially be off when it sees the voltage from the solar,what does the Victron do at night.

Martin

 

[TheCaller]

My take on it is that the Victron is seeing the output of the CBE & is being fooled into thinking that the batteries are fully charged. This is happening at a lower voltage on a hot day because of the temperature compensation.

Thus the only charging source during daylight hours is the CBE. Depending on the size of the solar panel array, it probably never does get the battery bank fully charged so it quite rightly stays in the absorption phase.

As Martin has just this second asked - does the Victron kick back in once the sun goes down?

 

[sallylillian]

OK, forgot to answer Martin, I have 240 watts of solar, the hab battery bank is 3 AGM's at 165 each. Caller & Martin, I will look tonight and see what happens. To confuse things a little for you I have 11 amps EHU here (odd number I know) and the Victron is set to that with power assist. Thanks for the feedback everyone.

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[funflair]

Pretty much as @TheCaller suggest, 240 watts of solar is going to make 15 amps max I guess so I would not think they will worry the 495ah of battery bank even without any temperature compensation, see what amps the Victron puts in once the CBE goes to bed.

Does the CBE have AGM setting?

Martin

 

[sallylillian]

Martin, unfortunately the CBE does not have an AGM setting just a gel or lead acid and it is set to gel but that has absorption at 14.3 which is too low, should be 14.8, which maybe another issue? In fact the whole set up had me complaining to N+B. In principle they have a good installation but are hampered by the fact that they have a customised CBE main panel and the regulator has to match to feed data in. But the regulator is a cheap one, they offer 3 x 80 watts of solar which I optioned to find that the regulator was maxed at that. Also when at the factory they were fitting Victron AGM's which they told me were now standard. I get Varta, half the cost. Another item on the list. But its annoying because we have had nearly 2 months in the van now and love it, much of the execution is exemplary but just some odd things which I find incomprehensible. It is so easy to get about compared to the RV and I do not have to check I can get in, just bowl up and "gis a pitch guv"
I have been out cycling and and considering the point about the Victron "seeing" the charge from the solar and therefore not charging and that is very logical. I will watch all day and see if the CBE goes over to float light.
Thanks for the help.

 

[sallylillian]

So we have been very limited on the use of power and the sun has been full on all day. After 5 hours, and for the first time, the CBE is showing a green light on float!! 13.8 volts which is the CBE gel float voltage which it is set at.
So my take based on all the good feedback is that overnight the Victron manages the float at a temperature compensated circa 13.4 or so whilst the solar sleeps.
In the morning as the solar wakes it says batteries down at 13.4, so goes to absorption taking it up to 14.3, takes an age to top off to 13.8 which is the uncompensated float that it wants to see. In the meantime the Victron thinks all is great so does nothing on the charging front. When I look at the CBE in the morning as the sun rises it will not show green because the Victron has allowed the batteries to bleed down to 13.4.
The way to check I suppose is to disconnect the temp sensor on the Victron.
So fundamentally all is well in principle, except the CBE unit does not have temperature compensating charging, and has an absorption voltage of only 14.3 max (no AGM setting) which is 0.5 volt down from the battery spec.

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[TheCaller]

I think you have it sussed.

If you are on site with an unmetered EHU, it may be best to pull the fuse between the solar panel & the CBE controller. That way the Victron will keep working. It has the more suitable voltages for both absorption & float & a higher charging capacity than the solar panels. It sounds as if the panels have been struggling to keep the batteries topped up during the day on their own.

Ok so long as you remember to replace the fuse when you unplug the EHU! Or you could fit a
relay to automate the task.

 

[sallylillian]

7kwh per day allowance so I'll keep useing the sun. Good to get to this point. Just emailed CBE and asked for a temp compensated, AGM setting, regulator, but wont hold my breath.

 

[TheCaller]

7kwh per day allowance so I'll keep using the sun.

In that case the fact that the CBE controller shuts down the Victron is no bad thing. It ensures that you extract the maximum energy from the sun while it is available. If there is any shortfall, the Victron will then make it up overnight.

Now that you know the CBE does switch to it's float phase once the battery bank is fully charged, there is little danger of overcharging. Even if it's float voltage is slightly higher than ideal, it will only be in that state for a short time & only on a day when you use minimal power.

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