Open or sealed batteries

I know certain people will argue about what I say next ... but :

You can get full charge without need for mains - but you need a good alternator and management setup. The problem with alternators charging - is the high amp rate. Every battery format that is rechargeable does not achieve 100% charge if its shoved in at high rate. Second we are using car based alternators on most boats and they are set to obtain in the mid 90's% charge level. Installing a charge management unit can bring that up to the max.

The question then is how much life are you giving up by pushing the batterys to 99 - 100% ?

I like the Stockholm Archipelago ... and that cruise usually runs about 10 days ... with maybe 2 stops where I can charge from shore ... every other night - its tied to trees or at anchor. My engine run for maybe 2hrs each day with a standard 45A alternator. No management system - just a changeover switch. I have 2 starter batterys of about 90 A/HR each.
I have no fridge to run except a Coolbox that can draw up to about 7 - 8A - that only runs when engine is on.
I will have FM radio .. VHF radio ... Plotter ... Tillerpilot .... in use literally continuous

If any day - I find either battery less than about 80% charge - I wonder what's wrong ..

I agree I am not running a Gin Palace or super duper things on board ... but still ...
 
Not being a lover of marina life myself I would e happy with achieving 90% SOC by engine and trying to make up with Solar at anchor especially in these conditions..
The batteries internal resistance for that last 10% would mean far too much engine usage for my liking.
 
wingcommander said:
Most reputable manufacturer rate at C 20 ( 20% of battery amp / hr size load test )
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I had understood C20 to mean "The capacity (Ah) of the battery, if the total stated capacity (e.g. 110Ah) is drawn evenly across 20 hours.

So a C20 rating on a 110Ah battery would be the Ah capacity if current is drawn at 5.5A for 20 hours (and I'm guessing as close to 110Ah is the ideal answer!)

Is that right?
 
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On Solar charging - I presume that being able to push charge into that last 10% is highly dependent on how much the solar controller can chuck out? I guess both the voltage and current it can supply?
 
Re: Would you also expect to get 2A for 25 hours? or does the profile of the current draw impact the capacity it can supply?

Yes, profile of current draw affects capacity. Here’s your answer: Peukert's law - Wikipedia

If you drain your battery at a high rate you get less overall energy out of it than drawing it at a slow rate.

On some battery meters you can program the Peukert value for your model of battery (obtained from the manufacture) so your meter can take everything into account before offering you a capacity figure.
 
MattS said:
I had understood C20 to mean "The capacity (Ah) of the battery, if the total stated capacity (e.g. 110Ah) is drawn evenly across 20 hours.

So a C20 rating on a 110Ah battery would be the Ah capacity if current is drawn at 5.5A for 20 hours (and I'm guessing as close to 110Ah is the ideal answer!)

Is that right?
Click to expand...
 
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MattS said:
I had understood C20 to mean "The capacity (Ah) of the battery, if the total stated capacity (e.g. 110Ah) is drawn evenly across 20 hours.

So a C20 rating on a 110Ah battery would be the Ah capacity if current is drawn at 5.5A for 20 hours (and I'm guessing as close to 110Ah is the ideal answer!)

Is that right?
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The rating is the theoretical capacity if the battery is discharged continuously over 20 hours without dropping below 10.5 volts.

In real life, you wouldn't want to discharge the battery anywhere near that low, so the useful capacity is around 50% or less of the Ah rating.
 
MattS said:
Really appreciate all the comments here - learning lots.

So, with my single 110ah "Leisure" battery, what should I reasonably expect to get out of it, if it was in as new condition?

Would it be reasonable to expect to draw 5A for 10 hours? (50ah so 50% of the stated capacity?)

Would you also expect to get 2A for 25 hours? or does the profile of the current draw impact the capacity it can supply?

Last night, after 2 hours of about 2-3A draw, the voltage was down to 11.9V - that doesn't feel right. Turn everything off, and it popped back up to 12.8V
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Just a thought about the voltage drop. I know that standard Jeanneau fridge wiring isn't great and quite a few people upgrade it because of the voltage drop. I also see a drop of 0.3-0.5V on my boat after living on board for several months and it is due to a dirty connection inside the isolation switches. Many people turn these off every week but I'm there every single day. I find that flicking the handles back and forth rapidly for a minute produces an instant improvement, lasting for several weeks. I'm probably removing some oxide build-up on the contacts.

You could be getting a false voltage reading if you are relying on a standard display installed in the saloon. It is worth checking at the battery posts if you haven't already.
 
Mistroma said:
Just a thought about the voltage drop. I know that standard Jeanneau fridge wiring isn't great and quite a few people upgrade it because of the voltage drop. I also see a drop of 0.3-0.5V on my boat after living on board for several months and it is due to a dirty connection inside the isolation switches. Many people turn these off every week but I'm there every single day. I find that flicking the handles back and forth rapidly for a minute produces an instant improvement, lasting for several weeks. I'm probably removing some oxide build-up on the contacts.

You could be getting a false voltage reading if you are relying on a standard display installed in the saloon. It is worth checking at the battery posts if you haven't already.
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Yes . The boat i crewed on has a 1.2.both switch that had not been touched in years ( always left on both) . When we discovered the flat house bank ,yet still had enough charges in the starting battery i thought , must be a wiring enomally. Turned out to be enough verdigris to break the contact and save our start battery. After spinning the switch several times normal service was restored
 
MattS said:
On Solar charging - I presume that being able to push charge into that last 10% is highly dependent on how much the solar controller can chuck out? I guess both the voltage and current it can supply?
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At the moment ....lots. but I find it does drop considerably overnight
 
Tranona said:
The instant voltage after use is of little value. It is the resting voltage after a few hours that gives you the state of charge. Your 12.8v immediately after switching off is a good indication that the battery is fine, but check it again a day later to see if it is holding the charge.
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A 2A load should not pull the terminal voltage down to 11.9V in 2 hours, something is not right.
 
[QUOTE="MattS, post: 7740274, member: 181830"}
I think this was my consideration - is sealed just more appropriate to a boat that's going to be heeling over. The vent on the current Powermax points out sideways, not up, as far as I can see!
[/QUOTE]

I installed a sealed lead acid deep cycle battery after being pooped by a wave that flooded the lazarette and diluted the electrolyte in the open lead acid battery I had at the time. The cockpit drained quickly but the lazarette locker did not. I hope a sealed battery would survive if this sort of flooding were to happen again.
 
MattS said:
On Solar charging - I presume that being able to push charge into that last 10% is highly dependent on how much the solar controller can chuck out? I guess both the voltage and current it can supply?
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No, the internal lead acid battery resistance rises and the battery charges up so progressively accepts less. The LA battery will only take what it wants, not what the controller could supply. Worth noting that whilst charging the battery some power from the charger could be used to supply other domestic items on board like the fridge.
 
MADRIGAL said:
[QUOTE="MattS, post: 7740274, member: 181830"}
I think this was my consideration - is sealed just more appropriate to a boat that's going to be heeling over. The vent on the current Powermax points out sideways, not up, as far as I can see!
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I installed a sealed lead acid deep cycle battery after being pooped by a wave that flooded the lazarette and diluted the electrolyte in the open lead acid battery I had at the time. The cockpit drained quickly but the lazarette locker did not. I hope a sealed battery would survive if this sort of flooding were to happen again.
[/QUOTE]

Given seawater and electrical connections don't live well together ........... sealed or unsealed probably makes no difference whatsoever. The battery will be shorted.
How did you know the electrolyte was diluted ? With Seawater in the locker shorting out the battery - electrolyte density would be way down low on the hydrometer scale ... due to low charge condition.

Sorry to be blunt - but I find it hard to think a battery would get such water in so easy unless the caps were off each cell ... the vent is just too small - the short of battery would be the biggest effect.
 
Refueler said:
I installed a sealed lead acid deep cycle battery after being pooped by a wave that flooded the lazarette and diluted the electrolyte in the open lead acid battery I had at the time. The cockpit drained quickly but the lazarette locker did not. I hope a sealed battery would survive if this sort of flooding were to happen again.
Click to expand...

Given seawater and electrical connections don't live well together ........... sealed or unsealed probably makes no difference whatsoever. The battery will be shorted.
How did you know the electrolyte was diluted ? With Seawater in the locker shorting out the battery - electrolyte density would be way down low on the hydrometer scale ... due to low charge condition.

Sorry to be blunt - but I find it hard to think a battery would get such water in so easy unless the caps were off each cell ... the vent is just too small - the short of battery would be the biggest effect.
[/QUOTE]
That make sense to me (low charge condition), especially as I didn’t discover water in the locker until the next day. When I couldn’t get the battery to hold a charge after hooking up a mains charger, I took it to the technician at our local marina and he said the electrolyte must have been be diluted. Of course it may simply have been time to change batteries anyway, and a deep discharge under water may have finished it off. I don’t know if it makes a difference, but it was fresh water from Lake Huron, not seawater.
 
MADRIGAL said:
That make sense to me (low charge condition), especially as I didn’t discover water in the locker until the next day. When I couldn’t get the battery to hold a charge after hooking up a mains charger, I took it to the technician at our local marina and he said the electrolyte must have been be diluted. Of course it may simply have been time to change batteries anyway, and a deep discharge under water may have finished it off. I don’t know if it makes a difference, but it was fresh water from Lake Huron, not seawater.
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Natural water in lakes / rivers etc. will have enough impurities in it to be conductive - even if only low value. Now that you have mentioned that the battery sat overnight - then if submerged - the vent would allow water in ... but even then - if the battery was with recc'd level electrolyte - you would only have a small amount into each cell. Looks like a combo of reduced density from being shorted under water and possible small amount of dilution.
Anyway - point is - sealed or unsealed - in that situation - you'd be lucky to save any battery.
 
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