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Old 05-02-2007, 06:54 AM   #1
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Recharge Time

Does anyone have a guestamite as to the time it takes to recharge batteries once hooked back to shore power? I have 2 24R Interstate AS issue batteries on a newer AS.
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Old 05-02-2007, 06:59 AM   #2
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At least overnight.
Fully charged would be a specific gravity of 1.275, in order for you to learn how long it would take, you can pick up an inexpensive hydrometer and check the batteries to see how long it takes until they get to the above number.
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Old 05-02-2007, 07:46 AM   #3
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It Depends......

.................on your depth of discharge (Terry's hydrometer suggestion comes in here), the rated amp/hours of the batteries capacity and the output (amps) of your charger (converter).

Typically, if your batteries are down 15% and let's say they are 200 amp/hours each, then you need 60 amp hours to re-charge them. If your converter puts out 30 amps, then it will take about 2 hours. This is not exact, but can be used as a 'rule of thumb'.

Make sense?
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Old 05-02-2007, 07:53 AM   #4
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A few years ago, I made an analogy to a milk jug and a straw.
If you have a 500 ounce (amp) milk jug (battery), and you have a straw (charger) that can fill the milk jug at a rate of 10 ounces (amps) per hour, it would take 50 hours to completely fill the jug.
There is a bit more to it than that, as the more fully charged the battery becomes, the slower the charge rate, but most non-technical people can understand this analogy.
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Old 05-02-2007, 07:54 AM   #5
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Simple is GOOD. Nice analogy!
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Old 05-03-2007, 09:31 PM   #6
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With no resistance from the battery, this is a good rule of thumb. Problem is that the charge rate (Amperage) drops off as the batteries charge because the internal resistance builds in the batteries. The first couple of hours on a discharged battery, you will see virtually all of the rated output of the charger going to the battery (sometimes more). With that logic, you can look at your watch and predict when you will be fully charged. Not quite though.
After a few hours, the rate tapers off and it can take even a couple days to reach full charge, depending on the charger type, Amp hours, etc.
Many of the newer chargers have a bulk or boost mode that raises the voltage (Pressure) to overcome the resistance and continue to deliver higher amperage for a period. This is typically limited to 4 hours or so for a couple of reasons. First, at 14.4 volts, the batteries will gas and gassing causes a loss of electrolyte. This is necessary for a full charge but must be regulated. Also, charging an already fully charged battery at 14.4 might overcharge it and lead to early battery failure if don't too often or for too long.
Most of the manufactures have settled on a max of 4 hours for bulk charging but you could argue for more or less. I argue for less as we get several calls a week from people complaining of sulfur smell, and over charged batteries, mostly from the inteli-power owners that won't leave the charge wizard button alone to do its job. Not you guys of course, SOB owners, haha.
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Old 05-03-2007, 11:50 PM   #7
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I mentioned the lowered rate as the battery charges, I just didn't want to get too technical. We don't know if the person asking is an electrical engineer, or somebody that doesn't know an electrode from an electron.
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Old 05-04-2007, 07:04 AM   #8
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Quote:
Originally Posted by overlander63
We don't know if the person asking is an electrical engineer, or somebody that doesn't know an electrode from an electron.
A which from a what?
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Old 05-04-2007, 07:06 AM   #9
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Quote:
Originally Posted by overlander63
We don't know if the person asking is an electrical engineer, or somebody that doesn't know an electrode from an electron.
Sur are an awful lot of 'Es' running around in this post!!!
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Old 05-04-2007, 07:12 AM   #10
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Originally Posted by lewster
Sur are an awful lot of 'Es' running around in this post!!!
Looks like one less than there should be...
My speel chequer let me know about it when I quoted it, too! Hee hee...
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Old 05-04-2007, 12:06 PM   #11
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Quote:
Originally Posted by overlander63
I mentioned the lowered rate as the battery charges, I just didn't want to get too technical. We don't know if the person asking is an electrical engineer, or somebody that doesn't know an electrode from an electron.
By golly you did say that Terry I know what you mean about those E's Lew. Some double E's call me but don't tell me they are a double E until the end of the conversation.
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Old 05-04-2007, 05:04 PM   #12
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Quote:
Originally Posted by overlander63
I mentioned the lowered rate as the battery charges, I just didn't want to get too technical. We don't know if the person asking is an electrical engineer, or somebody that doesn't know an electrode from an electron.
A preacher I know says that if you speak so the youngsters "get it", then everyone else will too.
I can handle simple.
Dave
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Old 05-05-2007, 07:49 AM   #13
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Quote:
Originally Posted by lewster
.................on your depth of discharge (Terry's hydrometer suggestion comes in here), the rated amp/hours of the batteries capacity and the output (amps) of your charger (converter).

Typically, if your batteries are down 15% and let's say they are 200 amp/hours each, then you need 60 amp hours to re-charge them. If your converter puts out 30 amps, then it will take about 2 hours. This is not exact, but can be used as a 'rule of thumb'.

Make sense?
Henw mentioned he has a newer AS. So I'm assuming he might have something like I have, a Parallax Model 7355, 55A converter charger.

I brought my batteries down to 50%, hooked in an amp meter, and connected to shore power. The meter showed about a 4.5A charge. Now I know putting in that meter does drop the voltage so my real charge rate removing the amp meter might be 5 or 6A (I'm guessing), but still thats a long way off the ideal of a 16A charge for a C/10 rate on my 2 X SRM-24 batteries (82AH each). In order to make charging with a generator more efficient, does this mean the Parallax that comes with the AS isn't the best option for charging?
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Old 05-06-2007, 03:10 PM   #14
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Your 7355 is capable of charging at 55 amps. Whether or not it will is determined by the batteries. 50% discharged, I would have predicted more than 5-6 amps initially but then it will taper off rather quickly with a constant voltage of 13.8. For faster charging, you will need a boost or bulk mode to force the current into the batteries faster.
I don't get too wrapped up about the C/10 ratings anymore with voltage regulated switching converters. Years ago, it was extremely important. Still, the only real concern in charging too fast now is heat and I suppose there is some trade off in recharge cycles but not much. 125 degrees is a common limit for some of the battery manufactures but with healthy batteries, I never see excessive heat build up. One bad cell in the battery bank and all bets are off!
Believe it or not, the 7300 Parallax is a well regarded converter with a low failure rate but it is not known for fast charging and might cause your batteries use excessive water in the summer months at 13.8 volts.
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