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Old 26-11-2012, 18:51   #16
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Re: Low battery voltage ?? E7 problem??

This quote is from the Trojan Battery Co.
Quote:
Correct the charging voltage to compensate for temperatures above and below 80o F. (Add .028 volt per cell for every 10o below 80o F and subtract .028 volt per cell for every 10o above 80o F)
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Old 26-11-2012, 18:54   #17
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Re: Low battery voltage ?? E7 problem??

Quote:
by Dsanduril;
If measuring voltage drop at the battery posts with a bad connection downstream there will still be somewhat more than anticipated because the current will likely go up to compensate for the downstream voltage loss.
I suppose that depends on how much you are anticipating. But I don't believe, even if you knew the good circuit voltage drop, that you could reliably tell the difference.
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Old 26-11-2012, 19:03   #18
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Re: Low battery voltage ?? E7 problem??

Correct, the charging voltage is increased with lower battery temperatures and Charging voltage should decrease with higher battery temperatures. BUT she said...Battery capacity and resting battery voltage is higher with higher temps and lower with lower temps.

Think of it as a cold battery needing additional voltage to get the electrons to flow when colder and needing a lower charge voltage as the batterys warm up.

This is not the same as saying the battery voltage is lower at high temps. Its more that the internal battery resistance is lower at higher temps and higher at lower temps..

See attached...

. Deep Cycle Battery FAQ
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Old 26-11-2012, 21:52   #19
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Re: Low battery voltage ?? E7 problem??

Get a 12 volt 60 watt light bulb with a pig tail socket, connect it to the battery first and have someone energize the bow thruster or winch. If the light dims a lot, it's probably the batteries or battery terminals. If the bulb stays fairly bright, move down the electrical line and hook the bulb near the mid point or pilot house panel and energize the bow thruster again. This is an easy way without proper meters. I would do this without expensive electronics on. I've seen cables with a pin hole that caused the wire to be corroded in the middle of a good looking cable causing very low voltage at the motor. Low voltage will be hard on the winch or bow thruster motor. Another way is to put the negative terminal of a digital meter on battery negative with a long wire without the charger on. Load up the main panel with everything on that is possible, at least 25 amps, check the voltage at the battery, then move along with the meter and follow the positive wire and see if the voltage drops while keeping the load the same. Then swap the long wire to the meter positive and do the same following the negative cable with it loaded. Every electrical connection may drop 1/10 th of a volt, that's normal. Good luck hunting.
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Old 27-11-2012, 10:49   #20
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Re: Low battery voltage ?? E7 problem??

Firstly thanks for all the replies/info.

AGM batteries. Maintained by link2000/Freedom458 when away.
Volts/amps from link and checked by multimeter.

I decided to charge o/night then disconnect batteries and check volts and clean all terminals. Batt No 2 showed 7.7 volts ( so truly u/s). Batt No 1 showed 12.9 v.
I cleaned up the terminals ( not dirty/corroded) and decide to repeat my test on the one "good" battery. Starting with 12.85v

Discharged at 16 amp for 20 mins batt volts 11.95. Discharged a further 30 mins at 30 amp batt volts 10.55 (10.64 by multimeter at post).

removed load and battery recovered to 12.55v in 1-3 mins ( about 85/90 % capacity I think.
Ahrs removed measured as 19Ah
Placed on charger.
Started as 14.2v at 33 amps. After 6 mins dropped to 13.2 at 8 amps and is slowly declining. Is this normal?

Why the big volt drop when under load.....I suspect the battery has seen better days ?

Sidetracked onto Generator battery which is an AGM and charging only from the Gen alternator at 15.7 volts ! I assume this is the voltage regulator which i can easily order.
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Old 27-11-2012, 11:10   #21
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Re: Low battery voltage ?? E7 problem??

If you have the space for it you should put a separate battery in the V of the boat. Partly to isolate from your other draws, but also to make the cable runs short. A bow thruster uses a lot of your power and it makes sense to me that it would reduce voltage enough to trip the electronics. Good Luck!
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Old 27-11-2012, 11:19   #22
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Re: Low battery voltage ?? E7 problem??

Firstly it's not a problem with E7. Those voltages are too low for the E7 to have any any hope of working.

That leaves 3 possibilities.

1. A poor connection
2 . One dead battery
3. Two dead batteries.

If the voltages were measured at the battery terminals. 2 or 3 are the most likely. Connect one battery at a time and see if one battery is fault.

If the voltages were measured elsewhere. Check the voltages at the battery terminals, if these are much better the fault is 1.
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Old 27-11-2012, 11:52   #23
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Re: Low battery voltage ?? E7 problem??

If I run the numbers you just posted I get an internal resistance for the battery of somewhere in the realm of 50-60 mΩ. Typical for a new lead-acid battery is in the range of 5-10 mΩ. Lots of estimating going on, since the load measurement method really requires a short duration high load current and quick measurements, but I think it's in the ballpark. An increase in internal resistance of that much is pretty much a sign of a dead battery. There are a couple of possible causes, but it doesn't really matter which, it's not like you can open them up and repair. It could be sulfation/sulphation and you could try some of the magic remedies, but probably not worth the effort on 5-year-old batteries. Could also be degraded plates, paste, etc. and there is no fix for that.
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Old 27-11-2012, 13:25   #24
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Re: Low battery voltage ?? E7 problem??

Again thanks for the info.
I tried the bowthruster trick again on one battery and tripped the freedom 458.Fortunately I got it back online.

So here I am in Bald Head Island NC with two dead batteries. Any recommendations for 2 off 200Ah AGM batteries ? An online supplier who ships ?
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Old 28-11-2012, 02:07   #25
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Quote:
Originally Posted by djneedham24
Again thanks for the info.
I tried the bowthruster trick again on one battery and tripped the freedom 458.Fortunately I got it back online.

So here I am in Bald Head Island NC with two dead batteries. Any recommendations for 2 off 200Ah AGM batteries ? An online supplier who ships ?
It's not Mail Order, but go to SAMs for AGMs if you can do it. there might be one in Wilmington. They are almost 1/2 of West Marine etc. price.
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