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Go Back   SailNet Community > On Board > Gear & Maintenance
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  #11  
Old 11-27-2006
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Frank,

First of all, if you have a wet cell then it is not maintenance free. If it is maintenance free, it is a AGM or Gel cell.

If you are charging the battery types in parallel, be sure they take the same charge voltage, it may be on the battery itself or you may have to look it up online. If they take the same voltage, and the same temperature compensation slope, you can charge them in parallel, if not, then you are probably doing damage. You may be overcharging one type and causing it to vent and dry out, or undercharging one type causing excess sulfation, or both.

Re Cruisingdads comments, if you are using a portable charger, i.e. Wallyworld special for automotive use, STOP. They are OK for starting batteries only. You need to get a good quality constant voltage type charger.

SOC and voltage measurements are very dependent on temperature, and not that accurate anyway. A fully charged battery may have a open cell voltage of 2.5 volts if cold enough. The best way to determine state of charger (SOC) is to monitor the charge current into a battery. When it has leveled off to a few 100s milliamps, depending on the capacity of the battery bank, and unchanging, then you can say it is fully charged. Monitoring amp-hours out vs. amp-hours in (multiplied by the efficiency, about 95%) is another good way, Iíve seen some marine chargers that do it this way.
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Old 11-27-2006
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Frank... I think Dave will verify that ..yes you are causing damage. You say you have a link 10 charger but that is only a readout instrument and I assume you mean that you have a Xantrex charger/inverter with a link readout. The Xantrex chargers have a different setting for Gel and for Wet cells. If you are on the Gel setting...you are undercharging your wet cells and will shorten their life. If you haveit on the wet cell setting you are overcharging your gels. Battery capacity does not matter in charging but battery type does. Since the gels are more expensive and you have 2 of them, I would suggest gtting a gel starter battery and setting the system for gels, assuming the gels are still performing decently.
Dave...I've seen a lot of "maintenance free" batteries that are described as wet cells with vents advertised for automotive use. Are you saying that these are really gels?

Last edited by camaraderie; 11-27-2006 at 02:19 PM.
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camaraderie, I second that, well said.
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Cruisingdad, thanks for your reply. I have set the charger/inverter specifications for the gel cell specifications, as I understand they are a bit more sensitive than the wet cell, including no equalization charge.
As I am often away from the boat for weeks at a time, and I want to ensure that both house batteries and the charger remain as fully charged as possible, I put the charge switch on "both". Short of buying an additional charger, I'm not sure how to keep them all charged, without damage.
Thanks again.
Frank.
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Frank,

Not to worry, at least not too much. Wet cells are much more forgiving then their maintenance free brethren. Charging at the Gel settings will do less damage to the wet cells then the other way around.

If you equalize your wet cells every two months or so it will help reverse the sulfation that will occur with the undercharge. You will need a separate charger for that, maybe even one of those (dare I say it) portable cheepies from Wallyworld. As long as it will bring the wet cells up to their equalize voltage that should be good enough. Be sure to disconnect the wet cells from the Gel when doing this.
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Old 11-27-2006
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Frank,

The only time I ever lost my batteries was when the charger got stuck on bulk and took the batts with them.

I put in a seperate charger for my starter. I did wire it into the system so that I can pull the starter batterty into and out of the house sytem for starting or whatever... though I never use it for house (or the house for start) at least I have it as such. Thus, with such a small wet batt, you could easily buy a cheap Xantrex charger and wire it independently for the starter and have a great redundant system. They install very easily. Now the Prosine 2.0 charger/inverter... that is another story. Thus,

DAVE.VERRY, if you are reading this, can I plese ask you a question that has been plaguing me for two weeks and several busted knuckles:

WHY DO I HAVE TO RUN A MINIMUM (MINIMUM) 4/0 OR LARGER CABLE WITH A PROSINE 2.0????????!!!!!!!! The charger was cheap compared to the cost of that freaking cable and lugs, trips to the hospital, a month in confession... etc.
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Quote:
Originally Posted by Cruisingdad
Frank,

DAVE.VERRY, if you are reading this, can I plese ask you a question that has been plaguing me for two weeks and several busted knuckles:

WHY DO I HAVE TO RUN A MINIMUM (MINIMUM) 4/0 OR LARGER CABLE WITH A PROSINE 2.0????????!!!!!!!! The charger was cheap compared to the cost of that freaking cable and lugs, trips to the hospital, a month in confession... etc.
The only reason I can think of would be voltage drop during startup inrush current. Remember, all wire and connections are resistors, with very small values. If the inverter takes a large amount of current to start, the voltage drop in a smaller wire may drag the voltage on the inverter input connections below a critical value, possibly causing it to oscillate on and off during startup. I am not familiar with this particular inverter so canít say for sure. A quick call or email to the manufacturer may be able to answer the question.

I feel for you, many a time Iíve scraped my knuckles on large cable crimps. 4/0 does seem a little excessive.
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Dave,

Yep, I called them, more than once, for an explanation on just that thing.

The first "gentleman" I spoke to gasped over the phone with frustration when I explained to him that there was a missprint in his manual (ie, 4/0 wire). He told me that 4/0 was the absolute minimum and I should consider larger. I explained to him that I did not know there was such a thing as larger wire and how was I suppose to run larger wire on a sailboat?? He seemed to infer some comment about putting my big girl pantys on and dealing with it. I told him I did wear big girl pantys but my wallet was on training pants and hung up on him. I then called back and spoke to the next techinical engineer that something about the, "...phase of the joobah, hooking into the jewah, causes a voltage drop in the wah-wah, and 4/0 this and that... now give me your credit card number..."

His comments were very helpful too so I hung up on him.

SO I am faced with a cable that is as big around as my leg, bends like a telephone pole, and costs more than my boat did. All of this so I can have a cup of coffee without turning on the generator. Ain't wives great!!
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4/0 cable

Dad,

I took a look at the specs for the Prosine 2.0. With a surge capability of 4500 watts, at a low battery voltage of 10.5 volts the surge current into the inverter, assuming 90% efficiency (probably less), will be 475 amps, more then justifying the 4/0 cable. My chart says 4/0 is good for 335A continuous. Since the inverter is rated at 4500 watts they are obligated by the safety agencies (read UL) to specify a cable at least that size, probably more like 350 MCM.

With a 2000 watt rating, the minimum wire size should be at least 2/0 (211 amps). This is for safety to keep the wire temperature to a safe level to prevent fire and contact burns. I would not wire with anything less, and think their recommendation for 4/0 is prudent. I know it’s a pain, but better safe then sorry.

They should have taken the time to explain this to you. It’s incorrigible that they would leave you with the impression they did. The large wire size is to keep the wire temperature to a safe level (so your boat doesn’t go up in flames) if there is a problem with the inverter or with a load the inverter is powering. Current = heat in wiring, the trick is to keep the heat to the minimum possible.
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I may be old fashioned, but I don't parallel my two batteries. Perhaps in really urgent circumstances, but that hasn't happened yet.

I do switch batteries after running the engine or charger to bring the duty battery up to charge.

Odd days I use #1, even days #2.

Fully charge the duty battery before switching it to reserve. Its charge will be your "Plan B" when needed.
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