Habitation drain? Affecting solar controller charge levels? (1 Viewer)

[Compactliner]

I have a Carthago Compactline i138 and a solar panel of 100w with a dual output PWM controller which is fitted without going through any of the CBE systems.
Although I've never had a problem keeping leisure and vehicle batteries charged while the van is kept on the drive, this winter (we are usually heading for Spain) seems to have been pretty dull and grey and I do check levels every few days.
I did find recently that, following several thick cloudy, rainy days, the leisure batteries were at 12.3v and the cab battery at 12.5v....not tragic but the lowest I can remember.
I put the van on EHU for a day or so and everything back up where they should be.
When the van is on the drive I normally have the control panel turned on and the '12v' systems button on in case I need lights etc.
In the past when I've been checking charging levels I've never seen the controller putting out more than 13v, more usually 12.8 or so...looking at typical charging profiles I thought this was low and should be seeing a float of 13.8v or so.
For some reason, I thought it might help the weak input if I turned off the control panel, in fact I did that and turned off the main habitation systems using the isolation switch.
On checking the controller output I was surprised (and delighted) to see 13.8v going into the hab batteries and 13.2v to the cab battery.
I've left this for a day or two now and batteries are all full even in sporadic winter watery sunshine...although a bright start today.
I know there is a small drain for alarm/immobiliser on the cab battery and I am also guessing that there is a small drain on the hab batteries and removing this (by using the isolation switch) has had an effect on the solar controller.
Obviously any drain is going to offset the benefit of the solar input and here in winter that effect is noticible, but should this be shown in a lower input solar charge level.
I can understand if the solar charge level was at 13.8 but other stuff draining the battery slightly, I couldn't understand why the solar charge would be lower due to a small drain....this is where I am confused. It's like a different controller with the hab systems isolated.
even when in Spain in bright sunshine, I never saw the controller putting in 13.8v to the hab batteries as it is now (always around 13v or so) but the batteries were always charged, obviously despite a small hab drain.
It looks like there is a drain which I will try and investigate.
I will get a clamp meter and measure drain with system as now...isolated...should be zero.
Then I will turn on the isolator to activate 12v but keep the control panel turned off.
Then turn on the panel but leave '12v systems' off
Then turn on '12v systems'
Then I guess it's looking at the various 12v systems by pulling fuses to find any drain.
Any comments on the above.

 

[ramsthom]

The control panel can contribute to a significant drain. On a previous motorhome the Sergeant panel showed a 0.3 amp drain if left on. Due to low solar output during winter its unlikely that would be replaced. I always switched the panel off.

 

[funflair]

Obviously any drain is going to offset the benefit of the solar input and here in winter that effect is noticible, but should this be shown in a lower input solar charge level.
I can understand if the solar charge level was at 13.8 but other stuff draining the battery slightly, I couldn't understand why the solar charge would be lower due to a small drain....this is where I am confused. It's like a different controller with the hab systems isolated.

I have clipped the above from your post , I think you are mistaking a high or low voltage as indicating charge which you should be reading in amps, when the control panel is on and drawing power the limited output from the solar is struggling to raise the battery voltage as the amps are being taken by the control panel drain, when you remove that drain the same amps from the solar controller can concentrate on raising the battery capacity and the volts will rise slightly.

Just my take though and remember that at this time of year the output from solar is minimal.

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[Compactliner]

Thank you both. Yes, I suspected that the control panel would be a small drain which I have now eliminated and the remaining charge from the solar panel (albeit small from a 100w in winter) seems to be doing the job of keeping all batteries where they should be.
Of course, with the hab batteries isolated, there should be no drain and, once fully charged, should stay that way leaving the SP to replace the small amount of loss from the cab battery due to the alarm/immobiliser.
Thanks again.
Chris.

 

[Lenny HB]

With the panel on discharge will probably be between 0.3 to 0.5A, with it off probably around 0.1 to 0.15 A.

Doesn't sound like your solar regulator is doing it's job or there has no been enough solar input due to the lack of sun the last couple of months.
The voltage should rise to 14.2/14.4v then drop to 13,8v float charge, no reason for the engine battery to be at a different voltage it should be the same voltage.
When dealers fit panels they normally charge a fortune and fit cheap & nasty solar regulators, probably worth changing for a decent MPPT like the Votronic.

 

[Compactliner]

I don't think I've ever seen 14.2v-14.4v although, with batteries always being pretty well charged, it may be that it does but for a very short time, then moving to float which is what I see.
I am aware the controller is a cheap one and I have considered the Votronic. One thing might be that the cab battery is lead acid and the hab ones are AGM. How would any controller be able to provide different charge regimes?
Once we get back 'in the van' I shall be giving the off grid capability a bit more testing.
Thanks again.

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[Lenny HB]

I don't think I've ever seen 14.2v-14.4v although, with batteries always being pretty well charged, it may be that it does but for a very short time, then moving to float which is what I see.
I am aware the controller is a cheap one and I have considered the Votronic. One thing might be that the cab battery is lead acid and the hab ones are AGM. How would any controller be able to provide different charge regimes?
Once we get back 'in the van' I shall be giving the off grid capability a bit more testing.
Thanks again.

The cab battery only receives a low current trickle charge so it is not a problem if is a different type.
What made you change the Gel batteries for AGM, AGM's are notoriously unreliable for habitation use.

If you change for a Votronic, the bulk charge will charge to 14.4v (14.7 for AGM) then go to an absorption phase for between 1 & 4 hours dependent on type of battery (4 hours for Gel) this is still at 14.4v but currently limited to around 1 amp and then drop to maintenance charge off 13.8v (actual voltage dependant on type of battery).

 

[Wh05apk]

When dealers fit panels they normally charge a fortune and fit cheap & nasty solar regulators, probably worth changing for a decent MPPT like the Votronic.

Mine seems to be struggling to keep the batteries charged as well, whilst in storage even with 420w of solar, I also have a cheapo pwm regulator and have considered changing to mppt, but realistically will it make much difference this time of year? Is it really worth the cost of changing?

 

[Lenny HB]

Mine seems to be struggling to keep the batteries charged as well, whilst in storage even with 420w of solar, I also have a cheapo pwm regulator and have considered changing to mppt, but realistically will it make much difference this time of year? Is it really worth the cost of changing?

Will give you around 25 to 30% more output, most improvement is at this time of year.
IMO MPPT regulators are well worth the extra cost not only for the better performance in dull contrition but the better ones are much kinder to your batteries being multi stage chargers with the correct profiles for different battery types.

If 420 watts is not keeping your batteries topped up you have either got a current draw from your batteries or there is a fault on the charging side.
I have 300 Watts with 3 x 80 a/h Gel hab batteries, hab and starter batteries are always fully topped up I never bother plugging into EHU.

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[Wh05apk]

If 420 watts is not keeping your batteries topped up you have either got a current draw from your batteries or there is a fault on the charging side.
I have 300 Watts with 3 x 80 a/h Gel hab batteries, hab and starter batteries are always fully topped up I never bother plugging into EHU.

That is my assumption, had it checked out twice and they say its normal, the drain is about 0.5a, which on a 246ah battery is about 5% a day.