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Old 05-04-2010, 04:23   #1
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Over-Voltage

Hi to the electrical experts - which we most definitely are not. Thanks in advance for advice, particularly the words in simple English for confused non-techies.

We are constantly experiencing a high-voltage problem (from 14.5 to 15.6v) which shows up as problems with our 12v microwave (bleeping and showing a high voltage sign), our fridge pump (overrunning) and our alpenglow lights which are very unhappy with too much power.

To describe this very specifically - the fridge (12v, watercooled with a pump) works very much as expected when not plugged in. When we are on shore power, it kicks in as required by the thermostat, and pulls power from the battery; the charger starts pulling in shore power, which then gets dumped to the fridge which then powers its pump much harder than needed or good for the pump.

The boat was mostly rewired in 2003, and we have a 2x 220aH domestic bank of AGM batteries. We use a victron multiplus charger/inverter (installed 2007) and have both a 240v system (only used when we have shore power) that does not run through the batteries, and a 12v system for everything else. A Balmar max charger is the regulator for the alternator

When away from the shore (most of the summer) we use solar, wind and a second alternator on the engine.

The battery voltage is at 13.2 to 13.3v when not attached to shore power but fully charged. The generators are all doing their jobs nicely. The problem is with the amount of voltage hitting the actual appliances.

This may be a really stupid question, but we cannot work out how to moderate this, so the appliances are not being damaged. Everything we have tried manages either the voltage in the batteries, or the impact of limited shoreside power, not our particular problem.

This system was professionally installed (in the UK) and has been reviewed twice since then by further professionals. It's not just us!

Any thoughts on this would be very much appreciated.
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Old 05-04-2010, 04:59   #2
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Hi Sarah and Pip,

It was not totally clear to me but I think you are saying that you only see the high DC voltage when you are plugged in to shore power? Do I understand correctly?

If that is the case and the voltage is OK otherwise then the problem must be with the battery charger.

If I misunderstand your problem could you clarify for me when you see the high voltage. Is it all the time, only when charging the batteries, what charging source is active when the voltage is high.

Unless you have a DC to DC voltage converter that raises the battery voltage it is impossible for the batteries alone to produce voltage that high so it must be coming from a charging source.

Skip
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Old 05-04-2010, 12:06   #3
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Hi Skip - thanks for your reply.

Yes, we only get the fast running pump etc when plugged in. And it seems to have gradually got worse. What really started this off was realising that our alpenglow lights were getting dimmer and dimmer. When we started investigating this we found that if we had more than 2 on at once there is the most enormous current drain. We are now thinking of changing all the wiring to the alpenglows. However, that made us see that we have a number of items suffering from this high voltage, and we think that is what has damaged the lights and is causing the problem with them ...

So - it may well be the charger/inverter which has caused the problem, and the lights are a major symptom!
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Old 05-04-2010, 12:20   #4
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What kind of a battery charger is it? It's possible you just need to configure appropriate voltages in the setup/settings for the charger - but maybe the charger is broken...
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Old 05-04-2010, 12:39   #5
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When being charged, lead-acid batteries should be around 14V. 15.6V is too high, and indicates your battery charger is too enthusiastic. This is your main problem, this charger needs to be set to 14.2V open circuit, or whatever the manual says for the batteries you are using.

It would be normal for the compressor to run faster when the voltage is higher, and this is not a problem. The compressor is likely to be damaged if the voltage is too low, as the motor not turning so fast draws more current and overheats.

You seem to have issues with too much current draw one one circuit too, which is why the lights are dimming. Not sure what to suggest here, putting the lights on another circuit is probably a major job. LED lamps often include a regulator, and don't mind if the voltage drops a bit.

Here's a good link to charging batteries Charging the lead-acid battery

You need to fix the charger before it ruins your batteries though.

Bill
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Old 05-04-2010, 12:56   #6
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Hi Sarah and Pip,

OK, if it only happens when plugged into shore power and the battery charger operating then that must be the culprit.

Normally Victrons are quite good, one of the best chargers and charger/inverters on the market. It could be a setting or adjustment but usually if something electronic changes over time it is an indication that something is not right. I would check the manual carefully to see if the charge voltage can be adjusted. Also double check the switches and settings.

As an afterthought I might ask how you know what the voltage is? Are you checking at the electric panel or at the battery with a volt meter to verify the over voltage?
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Old 05-04-2010, 12:59   #7
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Good point, a decent meter is vital, and the one on the panel cannot be relied upon. All digital multimeters are ridiculously accurate, Fluke are great. I use Beckman which are cheaper than fluke but very good.

Bill
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Old 05-04-2010, 14:20   #8
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Did you set the Victron up for AGM batteries? There are a cople of presets and then there is a bunch of user defined settings that can be used. Also the charge current can be set for your AH. I don't know if any of the settings could cause your problem but if you didn't set it up it might be worth looking at.
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Old 05-04-2010, 14:28   #9
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Good point, a decent meter is vital, and the one on the panel cannot be relied upon. All digital multimeters are ridiculously accurate, Fluke are great. I use Beckman which are cheaper than fluke but very good.

Bill
I had a Beckman but it died after only 6 years so I bought a Fluke. It was only 3-4 times more expensive.

Seriously, a good meter is good to have but even an el cheapo model from Radio Snack or Home Depot will work on the boat. Then when it falls overboard you aren't watching $200 sink to the bottom. I also keep an old, cheap analog meter on board. Easier to see the needle bounce when trying to trace an intermittent open or short.
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Old 05-04-2010, 14:33   #10
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G'Day RG,

I'm not specifically familiar with the Victron charger, but many smart chargers have a "sense"wire that connects directly to the battery bank and tells the chargers brain what the battery voltage is. If this wire is accidentally disconnected or if it has a bad connection, the brain thinks that the voltage is too low and cranks up the output voltage to compensate. Sounds possibly like this might be your problem. Check your manual to identify this wire and then trace it out, looking for faults/corrosion/bad connections or gremlins.

Good luck and cheers

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Old 05-04-2010, 15:38   #11
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Good idea on the sense wire!
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Old 05-04-2010, 15:48   #12
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Quote:
What really started this off was realising that our alpenglow lights were getting dimmer and dimmer. When we started investigating this we found that if we had more than 2 on at once there is the most enormous current drain.
You don't explain this very well but I would definitely check this out. Alpenglow lights shouldn't draw much.
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Old 05-04-2010, 15:58   #13
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Yep, the lights cannot be taking that much, I'm thinking they are on the same circuit as the fridge and when the compressor kicks in cable loss causes the drop in the voltage the lights are getting.

Bill
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Old 06-04-2010, 01:54   #14
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Hi and thanks again everyone.. It's now morning here and the sun is shining so we are more optimistic. After some deck work (using said sunshine!) we will both look at the settings and for the sense wire. We had wondered about the settings - we didn't install it and maybe it's not quite right.

The batteries are AGM longlifes. We have both a BEP battery monitor and a handheld ammeter. We have used the latter at a whole range of points and the batteries are fine, but we don't have a current meter that could measure across two points.

So we'll be back to you all shortly.
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Old 06-04-2010, 02:28   #15
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Hi and thanks again everyone.. It's now morning here and the sun is shining so we are more optimistic. After some deck work (using said sunshine!) we will both look at the settings and for the sense wire. We had wondered about the settings - we didn't install it and maybe it's not quite right.

The batteries are AGM longlifes. We have both a BEP battery monitor and a handheld ammeter. We have used the latter at a whole range of points and the batteries are fine, but we don't have a current meter that could measure across two points.

So we'll be back to you all shortly.
Even if you find some simple problem and solve everything in one stroke, be sure to post in detail what you found, what you did, and what effect it had. Others are reading this for their own information too. good luck.
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