Battery charger voltage

[JeremyF]

Ive been having to top up the domestic 140aH battery with water every 4 weeks, and I've measured the charge voltage from the charger. The engine battery seems to stick at 12.9v, but the domestic battery is being charged at 13.3v, even when fully charged. Can anyone confirm whether this is too high?

The charger is the stardard Bavaria fit Calira Sealine 27A. The is no sign of a switch to change between lead acid and gel, but it claims to be suitable for all types.I 'd appreciate if another Bav owner would check to see what the charge rate is for their domestic battery. Also, as all the labelling is in German, can someone confirm that the socket marked D+ should be left without a wire to it, but the adjacent B+ should be connected.

Many thanks

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[steve6367]

13.3 is a float charge and not too high. You would expect to see around 14.2 when charging and 13.3 when fully charged and just maintaining the battery. 12.9 sounds like its not on change at all.

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[davidwf]

Generally the more sophisticated chargers supply less current to the engine battery, as its normally the domestic that needs recharging the most. Normally you see a lower voltage on the engine battery during the bulk and absorbtion phase ie less current, once on float my charger tends to have the same voltage on both. May just be your charger works slightly differently and keeps the voltage down on the engine batt during float.

Try mailing info@calira.de their website is in German but they may be able to answer your questions.

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[bpb]

Jeremy,
The nominal voltage for a fully charged cell on a lead acid battery is 2.2, so a 12 volt (six cell) battery will measure up to 13.2v. A charging voltage of 13.3 is therefore ok. The charging current should be very small when the battery is fully charged.
I would not expect to have to top up so often, although you have not stated by how much the electrolyte level has dropped. Overcharging will cause the level to drop quickly and if you have to top up a significant amount each time it may be worth getting the regulator checked.
The variation between batteries could be because the engine battery is a different type or possibly older, as batteries age the voltage does drop because of chemical changes within the battery, sulphation etc.

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[davidwf]

Just struck me that maybe the Engine battery isn't charged at all by the charger, my Dufour 32 was like that. Worth checking to see if thats the case and it would explain the spare terminal on the charger.

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[gtmoore]

Yes, my friends Morgan was like this - only the service bank was wired to the charger until he had it changed.

<hr width=100% size=1><font color=blue>Gavin </font color=blue>

 

[JeremyF]

Interesting points, Thanks.

I reckon about 5mm per month of water per cell is the typical amount.

The start battery is brand new - the old one suddenly died at 3 years. Suspicious?

When charging by the altenator, the start battery was getting 14.15v and the domestic 14.05v. Am planning to get an Adverc at SBS for better regulation from the altenator.

So if 13.3v to the domestic is a good float voltage from the charger, wonder why the start battery only took 12.9v, yet takes slightly higher volts from the altenator?

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[JeremyF]

Hmm, that sounds logical - why bother to shore-power tyhe start battery, as it gets plenty of power from the engine after its been used.

Think I should ask Opal

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[gtmoore]

I guess but if you have an intelligent charger that can deal with multiple banks, why not keep it topped up?


<hr width=100% size=1><font color=blue>Gavin </font color=blue>

 

[silverseal]

Just a thought, are both batteries the same type? The engine battery should be "automotive" meaning that it delivers a big punch for a limited length of time, whilst the service battery should be of the deep discharge type, allowing it to provide, a regular wattage over a comparative long period. Maybe the charging characteristics are different? I have two engine batteries which usually are over 13 volts (24 volt system) and the service battery varies between 12.5 and 13 volts, topped up by a solar panel. I suspect that your batteries are gassing for the levels to fall so quickly, and so overcharging should be investigated

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[jackho]

You might consider asking the forum www.bavariaowners.org.uk The site is fairly new and needs some more input to liven it up.

Regards from fellow Bav 34 owner.

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[halcyon]

Have you had the battery out? had a similar problem in Falmouth, removing the battery exposed a screw, put small hole in battery, just a thought.
!3.3volt is totally to low for charging and to low for float charge, a flat battery on charge starts at 13.0 volt and will rise to 15.6volt or there abouts when fully charged. The terminal D+ may be a sensing terminal to allow for blocking diodes, 13.3 volt is a safe running voltage if there is no voltage on D+.
The engine at 12.9 volt would be a new battery not on charge, but near fully charged. If the engine battery is not charged of the shore, the alternator is running a little low, but adiquatley charging the engine battery.
You need to check voltages at the two batteries when you turn the mains charger on, this will tell what is connected.


Brian

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[JeremyF]

That was my next plan. Ive unplugged the charger, and will check the voltages on both batteries. Then, I'll turn on the charger, and see what reading I get.

I've e-mailed the German charger manufacturer, but doubt I'll get a reponse. Plan to phone Opal tomorrow, and see whether standard fit-out is for both batteries to be charged by the charger, as per the altenator.

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Dawn Chorus</font color=red>

 

[Oldhand]

I wouldn't agree that 5mm of water a month is typical. With extensive charging from both engine and shore power, my batteries may just about drop that amount in a whole season. The only reason I can think yours use so much in all cells is that they are getting too hot, are they mounted near the engine?

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[extravert]

I thought that too, 5mm a month seems a lot. My batteries get topped up annually, and never need much even after that time. My distilled water bottle is well past its 'best before' date.

<hr width=100% size=1>Summer is what you expect - rain is what you get.

 

[JeremyF]

Hmm, gets even more mysterious.

The batteries are under a saloon berth, not near the engine, so not unduly warm (but I do leave a dehumidifier going)

So, I'm using more water than normal, but have a float charge of 13.3v on one, 12.9v on another, and an altenator charge under the optimal 14.2v. I'm not exactly cooking the batteries with excess volts.

What I have done this weekend was to disconnect the charger, and see what volts I have in each battery next weekend. Then I shall reconnect the charger, and measure again. Both tests done with no load on the batteries.

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[MainlySteam]

A charged lead acid battery should give 2.1 v per cell ie 12.6 v when at rest and any excess surface charge knocked off the plates after charging.

Many boat owners find that they do not have to add much water (if any) to their batteries because their batteries are never fully charged, either because they do not have a multistep regulator or it is incorrectly setup/installed. A battery will gas as it approaches full charge and the number of times one charges it through that gassing state will determine to a large extent the amount of water that needs to be added. The amount the battery gasses is dependant upon the battery construction as well as the charge voltage - some batteries gas very heavily.

5 mm a month may seem alot for a small battery and assuming the voltages you quote are correct could indicate a failing battery. Or as Brian has said, a leak. But it is hard to say without knowledge of the battery case/plate geometry, the charging characteristics of the battery make, and the number of times it is taken through gassing.

As one indication for 520 AHr of high quality deep cycle batteries we put in about 2 -3 litres of water on average around every 4 months or so (so equating that to your battery is around 150 ml per month assuming similar battery construction and charge frequency) and have done so since they were new. They are solar trickle charged, holding them around 12.6 v, and then boosted through part only of the gassing state about once weekly, and typically for 9-10 weeks of the year, while cruising, twice daily through all of the gassing stage when more of the water use occurs putting the average up to what I quoted. So, quite alot of water.

If your battery takes a full charge, the charge voltages you quoted are accurate, the battery is taken from part discharged to fully charged frequently, and there are no fluid leaks then I suspect you have not got alot to worry about.

Trust that is of some help

John

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[JeremyF]

Thanks John. If I were to summarise your helpful explanation, it would be that a battery taken through a fully charging cycle regularly will consume the amount of water I'm getting through. My domestic battery is not using any more water now than 3 years ago, so hopefully thats not a sign of it being on the way out.

That simply leaves the issue 'why is one battery getting 13.3v and the other 12.9v on float charge' Ive put a call into Opal to see if Bav's charger only does the domestic one (which I doubt). Otherwise, its going to be a case of doing more tests after a week of no charging.

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[JeremyF]

Mystery solved

The reason for the large difference in volts when being charged is that Bavaria shore-power chargers are factory fitted only to charge the domestic battery! Units retrofitted by Opal in UK are wired up for both.

Thanks to the comments on this link, I've also learnt that 13.3v is a safe float charge level, and using a bit of water is a sign of a battery being fully charged.

Many thanks to all. Hopefully this has been of use to other people and not just me!

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[markdj]

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MDJ

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