Solar Overcharging Normal Lead Acid Battery Bank - Asking for a friend...

[alan_fincher]

This is not my issue, but relates to a live aboard friend.

 

Initially he reported CO detector going off with no obvious source, so we suggested gassing batteries, which indeed seems to be the cause.

Whilst I have not teased out all the detail of his set up yet, he appears to have a bank of three domestic lead acid batteries (not sealed type), two of which he has recently had replaced under warranty, the other not replaced and 18 months old.  These are showing voltages of 13.95 on the new and 13.1 on the old if solar is disconnected, and this is falling to between 12.8 and 13.3 after "resting them", (I've not explored what that means exactly), so no obvious bad cells and none getting noticeably hot.

My friend reports the "fizzing" is only when charging on solar, but says the battery monitor (type not yet identified) is showing 15.5V when solar is connected.  I've asked what type of monitor, and whether a meter across the bank confirms the 15.5V figure, (answer awaited).

I'm not very familiar with solar, but 15.5V, if correct sounds too high to me, and I'm not surprised the batteries are gassing.  I'm wondering if this is related to replacement of batteries under warranty?

Could those who are familiar with solar please comment, and in particular say what they would expect the highest voltage at the battery bank to actually be.

Thank you.

[Rooster73]

Ive fitted virious solor panel regulators and they seem to charge up to 14.2 volts,  over 15v i would suspect a faulty regulator

[Tracy D'arth]

If his charging voltage is over 14.8V whatever is supposed to regulate it is not working. If he has only the PV panels connected, then that controller is duff.

[Dav and Pen]

The regulator on my solar set up had adjustable limits and I would think most have. Mine was a 24 volt system and it was set to stop charging at 27.5 volts which I thought would be safe as the barge was left for months over the winter. I think 15 volts for a 12 volt system is to high and has caused the problem.

[nicknorman]

14 minutes ago, alan_fincher said:

This is not my issue, but relates to a live aboard friend.

 

Initially he reported CO detector going off with no obvious source, so we suggested gassing batteries, which indeed seems to be the cause.

Whilst I have not teased out all the detail of his set up yet, he appears to have a bank of three domestic lead acid batteries (not sealed type), two of which he has recently had replaced under warranty, the other not replaced and 18 months old.  These are showing voltages of 13.95 on the new and 13.1 on the old if solar is disconnected, and this is falling to between 12.8 and 13.3 after "resting them", (I've not explored what that means exactly), so no obvious bad cells and none getting noticeably hot.

My friend reports the "fizzing" is only when charging on solar, but says the battery monitor (type not yet identified) is showing 15.5V when solar is connected.  I've asked what type of monitor, and whether a meter across the bank confirms the 15.5V figure, (answer awaited).

I'm not very familiar with solar, but 15.5V, if correct sounds too high to me, and I'm not surprised the batteries are gassing.  I'm wondering if this is related to replacement of batteries under warranty?

Could those who are familiar with solar please comment, and in particular say what they would expect the highest voltage at the battery bank to actually be.

Thank you.

Solar controllers are normally configurable to select battery type, or a “user” type in which settings can customised. Presuming he hasn’t deliberately change the bulk voltage to 15.5, I suspect the controller is faulty and just passing the solar panel voltage straight through.

 

Some controllers won’t tolerate disconnecting the batteries whilst the panels are producing power. Perhaps he did this when changing the batteries, and blew the controller?

[eid]

Could the regulator be doing an equalisation charge at the time 15.5v was measured? My old one would do this with no way to turn it off.

Edited April 16, 2020 by eid

[Alan de Enfield]

10 minutes ago, eid said:

Could the regulator be doing an equalisation charge at the time 15.5v was measured? My old one would do this with no way to turn it off.

 

I was going to suggest the same - my solar does an equalisation charge (I think) every 28 days.

[WotEver]

1. Yes, 15.5V is too high so either...

2. He has set the voltage too high or...

3. The controller is faulty or...

4. The controller is performing an unwanted and unnecessary equalisation charge, which is really the same as 3.
 

5. Yes, if the controller has been doing it for a while then it could indeed be why he suffered premature failure of his previous batteries. 

We need to know the make and model of the controller 

[eid]

1 minute ago, Alan de Enfield said:

 

I was going to suggest the same - my solar does an equalisation charge (I think) every 28 days.

Mine did it every day on the charger battery (it being full already at the start of that days charge). Hopefully it didn't do too much damage!

[WotEver]

Just now, eid said:

Mine did it every day on the charger battery (it being full already at the start of that days charge). Hopefully it didn't do too much damage!

It will damage the battery for sure. All it will achieve on a non-sulphated battery is excessive corrosion of the plates. 

[eid]

Just now, WotEver said:

It will damage the battery for sure. All it will achieve on a non-sulphated battery is excessive corrosion of the plates. 

 

Yikes now I'll never sell the damn thing ?

[Alan de Enfield]

3 minutes ago, eid said:

 

Yikes now I'll never sell the damn thing ?

I'm sure you will - many 'scrappies' will take batteries whatever their condition.

[Phil.]

I would suggest it depends on the type of battery and the settings of the charge controller. Mine is set to absorbing charge at 14.8 v but in bright solar conditions when temperatures are low, the charging voltage can go as high as 15.5 but more normally around 15.3.

[alan_fincher]

Thanks all....

 

Much what I was expecting people to say, but with no solar ourselves, I thought I would check.

If I find out more information , I'll post it here.

 

59 minutes ago, nicknorman said:

Some controllers won’t tolerate disconnecting the batteries whilst the panels are producing power. Perhaps he did this when changing the batteries, and blew the controller?

 

Yes, this thought had crossed my mind.  Last summer when I had a borrowed panel lashed up to our battery bank, we were always meticulous to disconnect the panel from the controller if we were going to disconnect the controller from the bank.  I'm wondering like you if the conroller has been left with no load with the panels still generating a good output.

I will ask!

[Onewheeler]

Is there a controller in use?

[MtB]

52 minutes ago, Onewheeler said:

Is there a controller in use?

 

This was my thought too.

 

Panel connected straight to battery could easily cause the symptoms described, and Alan makes no mention of a controller on the OP's boat. 

 

 

[alan_fincher]

I've now been told the controller is a Victron BlueSolar MPPT 75/15.

 

Additionally I asked whether the load has been disconnected without disconnecting the panel first, and am told this was once done accidentally about 2 years ago, but he has been rigorous since not to.

I have now asked if the overcharging problem is recent, or if it could have been going on a long while...

Watch this space!

[Rooster73]

Depending on the battery temperature, lead acid batteries can gas around 14.4v in summer, i would only recommend a charge over this voltage for a short period

[cuthound]

30 minutes ago, Rooster73 said:

Depending on the battery temperature, lead acid batteries can gas around 14.4v in summer, i would only recommend a charge over this voltage for a short period

 

Lead acid batteries begin to gas at 2.25 -2.27 volts per cell (13.5-13.62 volts for as 12 volt battery), irrespective of temperature. Hence a slightly lower voltage than this is usually used for "float" charging.

 

I agree that holding a battery at voltages above this for significantly long periods of time will significantly shorten their lives.

Edited April 16, 2020 by cuthound

[Bod]

With our solar set up, I found the batteries were using much more water than previously, with a shore line charger.

The Epever MPPT controller, has setting for various battery types, I had set it by the instructions for flooded lead acid, however reading the instructions, it was found the settings for sealed batteries, had a slightly lower voltage, which I have now used.  Water use has dropped to previous levels.

Once we can return to the boat, I expect the water level still to be ok....

 

Bod.

[Tony Brooks]

I would suggest as a quick and cost free test that you disconnect the controller from the panel and then the batteries leave it like that for half an hour or so and then reconnect, batteries first, to see if the problem has gone away. Just in case the controller thinks its on a 24 volts bank.

[alan_fincher]

53 minutes ago, Tony Brooks said:

I would suggest as a quick and cost free test that you disconnect the controller from the panel and then the batteries leave it like that for half an hour or so and then reconnect, batteries first, to see if the problem has gone away. Just in case the controller thinks its on a 24 volts bank.

Funnily enough Tony, after spending some time studying materials on some kind of Victron user community group (I don't know details), our friend did more or less this, as it is apparently something that can occur.

He reported success initially, with charging down at 14.1 volts.  However this was short lived, and it now back charging at 15.7 volts apparently.  I'm wondering if it is managing to sort itself out for a while, but for some reason then going back to wrongly interpreting what it is connected to.

 

These MPPT controllers seem to be about £80 or perhaps a bit more.  If it were cheaper I'd suggest swapping for a replacement to rule it out, but that's a bit steep if it fails to fix it.

On the other hand, if it can be prevented from trashing battery banks at about £200 a time, maybe it could be 80 quid well spent?

[Onewheeler]

2 hours ago, cuthound said:

 

Lead acid batteries begin to gas at 2.25 -2.27 volts per cell (13.5-13.62 volts for as 12 volt battery), irrespective of temperature. Hence a slightly lower voltage than this is usually used for "float" charging.

 

The data I have suggests that the gassing voltage varies (roughly linearly) from 2.30 V per cell at 50 C to 2.97 Vpc at -20 C. That came from here, and remember saving a similar table from Trojan which I can't locate at the moment. Best to keep inside those parameters.

[Phil.]

49 minutes ago, alan_fincher said:

Funnily enough Tony, after spending some time studying materials on some kind of Victron user community group (I don't know details), our friend did more or less this, as it is apparently something that can occur.

He reported success initially, with charging down at 14.1 volts.  However this was short lived, and it now back charging at 15.7 volts apparently.  I'm wondering if it is managing to sort itself out for a while, but for some reason then going back to wrongly interpreting what it is connected to.

 

These MPPT controllers seem to be about £80 or perhaps a bit more.  If it were cheaper I'd suggest swapping for a replacement to rule it out, but that's a bit steep if it fails to fix it.

On the other hand, if it can be prevented from trashing battery banks at about £200 a time, maybe it could be 80 quid well spent?

Just having a quick look at the manual, and the fact you now state voltage is 15.7 this may indicate that the charge controller, has been programmed to perform an equalisation charge. Although not required, this can be programmed to occur daily. If so it will attempt to raise the voltage up to 16.2. The caveat, I did not read the manual in detail it was a brief glimpse, but may point you in the right direction.

[cuthound]

16 minutes ago, Onewheeler said:

The data I have suggests that the gassing voltage varies (roughly linearly) from 2.30 V per cell at 50 C to 2.97 Vpc at -20 C. That came from here, and remember saving a similar table from Trojan which I can't locate at the moment. Best to keep inside those parameters.

 

Interesting, however they are both pretty extreme temperatures for a lead acid battery.

 

I have worked with lead acid batteries for most of a 40 year career but in the temperature range of 0°C to 30°C. Within that range I have never seen a significant change in gassing voltage with temperature.