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Amp hours and voltage

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Black Diamond View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Black Diamond Quote  Post ReplyReply Direct Link To This Post Posted: 18 July 2018 at 12:29
Usually there is "Peukerts Exponent" (or whatever its called) to be set as a variable to the charger/monitor which affects the way it charges and / or counts amps.   Have you looked at the manual for proper setup of the variables for your batteries and charging system?

Rick
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Hanse 575 Build #192, Hull# 161
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Rubato View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rubato Quote  Post ReplyReply Direct Link To This Post Posted: 18 July 2018 at 20:57
Originally posted by Black Diamond Black Diamond wrote:

Usually there is "Peukerts Exponent" (or whatever its called) to be set as a variable to the charger/monitor which affects the way it charges and / or counts amps.   Have you looked at the manual for proper setup of the variables for your batteries and charging system?


Peukert's can be input on some battery monitors but it has no affect on charging.
Steve

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StavrosNZ View Drop Down
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Post Options Post Options   Thanks (1) Thanks(1)   Quote StavrosNZ Quote  Post ReplyReply Direct Link To This Post Posted: 18 July 2018 at 23:03
Jeremy, i did a post on the upgrade as follows:

http://www.myhanse.com/alternator-upgrade_topic10185.html

Stephen
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Post Options Post Options   Thanks (0) Thanks(0)   Quote StavrosNZ Quote  Post ReplyReply Direct Link To This Post Posted: 18 July 2018 at 23:24
stereo has permanent power to retain stations, bilge pump, one overhead light normally and alternator smart regulator likely to have permanent supply as well.

Solar properly regulated will keep these looses accounted for and batteries topped up but an efficient alternator/regulator remains best most efficient way to keep your charging up.

Don't leave shore power on permanently either in my experience this reduces battery life and increases risk of other issues (electrolysis etc).
Stephen
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike2145 Quote  Post ReplyReply Direct Link To This Post Posted: 19 July 2018 at 09:31
Originally posted by Jeremy Jeremy wrote:

Thanks Stephen. Ive just replaced the batteries. Gone to 444 amp hours. One of the old batteries had a capacity of 35ah and the other 41ah, so they were well gone. Still not sure why. I checked the charger. Its set to AGM. For now I've disconnected the solar panels. Yes I guess your right. 20min of diesel is nothing for a full charge! Did you have to change belts / pulleys? Why couldn't you just bolt on a bigger alternator? Where did you get it?
I had a phantom amp draw too of around 0.3a +. Ive determined the cause of most of that, just 0.12 amps unaccounted for.


Remember adding a high capacity alternator on its own will have little or no advantage. It need to be coupled with. Charger and battery bank that can make use of the available power. Most smart chargers can do this but do check. Iíve seen many high output alternators fitted without updating the downstream components. And itís made no difference. The rating is the maximum it Ďcaní produce not what it will. It is the charger and battery pack that determines what will be generated by the alternator the alternator can only do what itís asked to do up to itís rated ability. Matching what the battery bank can accept at a maximum charge rate controlled by the charger (plus other ancillaries) with what the the rated output of the alternator is the key (plus a bit to keep the stess down on the system) is the key.
Have a look at other threads on the subject there is a lot of information on this and other forums.

Ignore me if you already know all this stuff!

Mike
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StavrosNZ View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote StavrosNZ Quote  Post ReplyReply Direct Link To This Post Posted: 19 July 2018 at 21:36
agreed Mike, smart regulator and cable sized for higher output and battery bank accordingly. Also replaced shore power charger at the same time with new Pro Mariner Pro Nautic charger that also has ability to act as power supply to the boat sockets without charging as setting.
Stephen
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rubato Quote  Post ReplyReply Direct Link To This Post Posted: 20 July 2018 at 17:32
Originally posted by StavrosNZ StavrosNZ wrote:


Don't leave shore power on permanently either in my experience this reduces battery life and increases risk of other issues (electrolysis etc).

If you don't keep shore power attached to trickle charge your batteries, the trickle charge needs to come from somewhere else (possibly solar as you mentioned above). Lead acid batteries in particular have a fairly high rate of self discharge which can also destroy battery life. 
Steve

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jeremy Quote  Post ReplyReply Direct Link To This Post Posted: 21 July 2018 at 21:18
Hi,
Yes Ive inputted the correct perkets number. This seems to have improved ah accuracy. I took the new batteries for a test run last night. Seems we use about 50ah over night and in the morning were on about 12.7V to 12.8V. This was verified by the multi meter.

Thanks!!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jeremy Quote  Post ReplyReply Direct Link To This Post Posted: 21 July 2018 at 21:21
Yes thanks for that. Im not going to track down the last 0.1A of loss. Just put it down to those items. It seems everything is functioning properly again now with new batteries and property set up monitor.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike2145 Quote  Post ReplyReply Direct Link To This Post Posted: 06 September 2018 at 09:52
Originally posted by Jeremy Jeremy wrote:

Hi Guys,
I have the standard 415 battery setup (2 x 165ah batteries so 330ah) and Ive recently installed a BEP battery monitor. 
Over winter Ive found we are drawing a lot more power over night with fewer day light hours and less effectiveness in solar charging. By morning we are getting very low on power, the displays are showing approx 11.9V in the house system. But here's the issue. The BEP monitor is showing we are down to 11.9V but also saying that we have 300ah remaining. Thats 90% charged! Ive heard these AGM batteries are good till about 50% charge. So im rushing to get the motor started because im seeing 11.9V.
Im not sure of the relationship between V and Ah, who should I trust? My batteries are the original ones (2014) Maybe they're nearing their use by date?

Thanks heaps!

Just to answer the original question of the relationship between V and Ah.  The short answer is none directly, its a % of the total so  unless you know the total available Ah of the battery you cant say what % in Ah remains or has been used.  The voltage drops at a predictable rate (for a battery in reasonable condition) and therefore at certain voltages we can say that the battery is at x% charge.  The list below is a reasonable, if a bit pessimistic, set of numbers to work from. So we can say that when the battery is at 12.6v its about 50% discharged.  So in your case the 330Ah total has used 115Ah. (the 330 would be very optimistic even for a new battery) NOTE:  These voltage readings should be taken off load and after the battery has rested.  The voltage will reduce when on load giving  false reading.  So measure when there is no or minimal load to get a rough idea of the state of charge. 
If the battery is showing 11.9 with minimal or no load then they are flat.  Ignore the battery monitor.

The advantage of a good  (expensive!!) monitor is that it will be able to do some cleaver maths, using a set of numbers similar to below, to start to work out what the actual capacity of the battery bank given charge/discharge amps is and give a readout of available capacity and state of discharge in a Ah or % display as long as the thing is set up correctly. However,for that money I can do the maths myself!


Hope that helps?



Image result for agm voltage verses capacity chart
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