Hey Guys,
I did a little boning up on FLA vs. AGM charging. Looks like their charging requirements are fairly similar, and I think those Guest chargers will work fine with AGMs. The bulk mode voltage is lower than recommended by Lifeline, but this is a current-controlled mode so I don't think the voltage matters much. Absorption mode voltage is a bit lower, but close. The float mode is right in the ballpark.
I wanted to compare them to the Dual Pros, but couldn't find the specs listed on their site. I did find some nice tutorials here though:
http://www.chargingchargers.com/tutorials.html
I'm on the fence regarding parallel vs. isolated strings, at least in lower powered systems. There are arguments to be made for both. Above a certain power level, the balance definitely tips in favor of parallel due to peukert effect. Not sure what that level is for a 100AH AGM, but if I were to take a wild guess I'd say if you're going to run more than 40 or 50A continuous it might be better to go parallel.
Maybe someone with real AGM expertise can weigh in on this.
I think I would consider wiring in a 1/2/both switch to have all the options available. You'd need to be careful how you manage the switching though.
On the wire-length balance question, I can see how this would be important, but I don't think I'd be too hung up on precise lengths. There are a number of other sources of resistance in the wiring system (terminals, switches, fuses, shunts, batteries) that will all contribute to the total, and some will vary over time depending on maintenance and aging and such. Putting an ammeter in each string would allow you to monitor the balance. Then you'd need to decide how close is "close enough".
This is a great area of discussion, and I'm looking forward to hearing others' take on it.
Regards,
Jim
--- In electricboats@yahoogroups.com, "acsarfkram" <acsarfkram@...> wrote:
>
> Hi Richard,
>
> That sounds like a good way to go if you can keep the batteries in the same area. In my Ericson 27 I have the batteries under the port and starboard settee's. To connect them in parallel would take a lot of really heavy gauge ($) wire. Make sure you can isolate the banks from each other if you have a problem in one of the banks. I'm thinking you would have to use all the same batteries.
>
> I do like the separate bank concept for other reasons. If using a portable generator to extend range you can charge one bank while using the other. It keeps the set-up simple (same as shore power) and while I have no technical reasoning to back this, it seems that the charging bank will be easier to charge fully if it is not being used for propulsion. Ideally, you should bring the bank to a fully charged state before using it for propulsion. My guess is a smaller bank is easier to charge? Again this is just my intuition :-).
>
> I look forward to more informed input to my ramblings!
>
> Mark
> Santa Cruz
>
> --- In electricboats@yahoogroups.com, Richard Mair <fullkeel2000@> wrote:
> >
> > I am actually installing the same system and using 2 banks as well.. The advice I received from a good source is to make two separate banks and then hook them in parallel.
> > Â To get the batteries to discharge evenly you need to use the same length of wire between the batteries.
> > Â The runs that connect the batteries to the switch and the motor also have to be identical lengths on both banks..
> >  What you are looking for is equal resistance so it could actually be done with different sizes of wire but that would require a lot of calculation to get the resistances of the wires right its way easier to just use length and go up a wire size if yo u are worried about the overall resistance
> > Richard
> >
> > --- On Sat, 2/26/11, m8trixman <pb@> wrote:
> >
> > From: m8trixman <pb@>
> > Subject: [Electric Boats] Schematic or diagram of system help
> > To: electricboats@yahoogroups.com
> > Received: Saturday, February 26, 2011, 9:55 AM
> >
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> > Â
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> > Chaplain on Deck:
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> > I am new to this forum and am converting my 1974 Cal-29 to electric. I just purchased the 100ibl motor through electric yachts. I am getting 8 US AGM 31 batteries to power the system and have a question. Should I make two banks of four or connect the two banks in parallel? If anyone has a schematic or diagram on how to hook up the system â€" your input would be wonderful!
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> > Also, if you have any advise - so far we have decomissioned the diesel engine and fuel tank, and have cleaned and painted the engine space. What should we do next?
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> > I will post some photos...
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> > BTW â€" Mike at www.electricyachtssocal.com has been GREAT, as well as Scott at www.electricyacht.com/
> >
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> > ~~(\_~~~~~(\_~~~
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> > ~~~~(\_~~~~(\_~~~
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