Jeff,
You don't have to isolate the batteries to charge them with individual chargers.
Just be sure to check your chargers to ensure that the negative output of the charger isn't tied to any kind of common ground!!
There are a couple of advantages to using 4 single 12V chargers. Assuming you're using trickle chargers, they're cheap and easy to replace if one goes bad, instead of having a single very expensive charger.
Second, you can watch each battery individually, instead of relying on the string to self-balance as they charge.
The advantage of a single 48V charger is that it is a LOT less wiring, and fewer components to fail. I've tried both. Keeping up with 8 individual chargers is a pain.
AGM batteries might be a good alternative to golf cart batteries. I have a set of 4 Deka 8A31 (?) batteries. They're 70 pounds each. Group 31 size (maybe just slightly bigger than a group 27 - but they fit in the standard large battery boxes). I believe they're rated for around 100AH. They are completely sealed (no watering), and theoretically can be mounted in any position.
They're a little more expensive than flooded batteries, but hold up better.
Good luck!
John
From: "Jeffrey Griglack griglack@yahoo.com [electricboats]" <electricboats@yahoogroups.com>
To: "electricboats@yahoogroups.com" <electricboats@yahoogroups.com>
Sent: Friday, October 14, 2016 9:35 AM
Subject: Re: [Electric Boats] newbie charging question
king_of_neworleans,
I had not thought about mounting the batteries athwartship. In fact, currently, my batteries are mounted fore and aft. I had never heard, before, that the batteries should be mounted like this, and I will consider it.
The golf cart batteries are tempting. If I get them, I would probably keep the group 27s as well, and would probably want to install a watering system for the batteries that are hard to reach. I'll have to look into that.
As far as leaving the batteries on for the winter, I suspect, from your name, that you are in the New Orleans area where the winters are pretty mild. I am quite a bit farther north than that (New England) where it gets a little colder in the winter. I have left my house battery (a deep cycle group 27) on the boat for the past 3 years, all winter, but I have less invested in that one battery than I do in the 4. I can replace one battery without a big hit to my wallet, but I shouldn't really replace one battery in a 4 (or 8) battery bank. There are parts of my house where it does not get too hot in the winter, but stays above freezing. The boat will go below freezing, possibly into the negative degrees F.
Charging the batteries independently to keep them balanced seems counterintuitive (which doesn't mean that it's wrong). I will look into this. If I were to do this, wouldn't I have to isolate the batteries (which are wired in series) during charging?
Thanks for the input,
Jeff
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| Jeff Griglack "Blithe Spirit" P-30 #182
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| "Don't take life so serious, son, it ain't nohow permanent"
| - Walt Kelly
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On Wednesday, October 12, 2016 11:47 PM, king_of_neworleans <no_reply@yahoogroups.com> wrote:
I have a somewhat smaller boat, a Cal 2-27, and I had I think the same prop, originally turned by an Atomic 4. I repowered with the boat in the water and did not change props right away. This spring I did a haulout and took the opportunity to do a prop change. I had been given a pair of 14x10 RH 3 blade props, and I put the better one on the shaft, and had the more beat up one refurbished at a local prop shop for a spare. The difference in performance is significant. I am currently running a ME0201014201 5kw motor, 48v bank of 6v GC2 golf cart batteries, (FLA) and a 2:1 reduction enclosed gearbox. I may try a 3:1 gearbox this winter. Anyway, folding props are designed with significant compromises in efficiency in order to make them more streamlined for sailing. If you seldom motor, keep the folder, or go with a bigger folder. If you motor a lot, go with a fixed 3 blade prop, as big as you can swing under the boat, is my suggestion. Adjust reduction ratio as needed.
I will admit to having very little experience with AGM batts, and less with Lithiums. My flooded lead acid bank has served me well for going on 3 years now with no signs of imminent failure. The drawbacks are for me a reasonable tradeoff for the low price I paid at Sams Club for them. AGM are a little touchy when it comes to overcharging, etc. True, they offer a lot of advantages in installation orientation, and less maintenance, but if I were shopping for a battery with those advantages and willing to pay more, I think I would go the whole enchilada and get LiFePO4 batts. Deeper discharge, longer life, lighter weight. If cost is a significant factor, go with the golf cart batts. They are rockin for me. About as bulletproof as a battery can get. If they boil off a bit, no biggie. I got plenty of distilled water on hand and don't mind checking the electrolyte levels after every heavy charge cycle. Just be sure to mount them SIDEWAYS in a sailboat. IOW, ends pointing port/starboard, not fore/aft. Fore and aft mounting is incorrect when heeling is expected, because of the orientation of the cells. Remember, electrolyte does not just slosh from end to end within the battery. The cells are whole separate ecosystems, rectangular shaped, flat sides facing the ends of the battery casing.
Since your gp 27's still have some life left in them, why not move them back aft where you were going to put the second bank of AGM, as a reserve bank, and install the golf cart batts too? That would give you some pretty decent range on electric.
I am currently using a gang charger from West Marine, and each 12v cable pair is charging two of my golf cart batteries. Works fine for me. Honestly, I would actually rather have independent charge circuits for each of my 6v batteries. This would help keep them balanced, I believe. And a fault light or taking a longer time to charge one than the rest will tell me when one battery is underperforming, at a glance. I was using a 15a 48v single bank charger and it was not really doing the job, I don't think.
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Posted by: oak <oak_box@yahoo.com>
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