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noelex 77 14-11-2019 05:21

Re: Troubleshooting Drained batteries and Dead Charger.

Originally Posted by GordMay (Post 3015489)
The coulometric charging efficiency of flooded lead acid batteries is typically about 70%, meaning that you must put 142 amp hours into the battery for every 100 amp hours you get out. This varies somewhat depending on the temperature, speed of charge, and battery type.

Not in this case.

The calculations were for the situation when the shore charger is on 24/7. The charger will therefore be supplying nearly all the power (only when the load is above 6A does this not apply) so the coulometric charging efficiency will rarely come into play. The majority of the energy is not charged and then extracted from the battery.

There will be some energy consumed by the battery (and converted to heat) maintaining the float voltage, especially if this cannot be lowered to the more appropriate storage voltage. This is quite different to the coulometric charging efficiency. The current will only be small for a healthy battery.

The largest unknown is if the battery charger can supply its 6A rated output on a continuous basis. Some can (so there are honest manufacturers out there:)), but many cannot and the shortfall can be significant.

Stu Jackson 14-11-2019 10:44

Re: Troubleshooting Drained batteries and Dead Charger.

This ^^^ is a very good boat electrical book.

You could also Google "How to use a multi-meter."

Good luck, keep at it.

boatpoker 14-11-2019 10:49

Re: Troubleshooting Drained batteries and Dead Charger.

Originally Posted by Santiano (Post 3015317)

I've just been reading up on the "marine surveyor" link,

Which "marine surveyor" link ?

skenn_ie 22-11-2019 07:56

Re: Troubleshooting Drained batteries and Dead Charger.

Originally Posted by smac999 (Post 3011518)
A 6 a charger is way to small to keep a battery charged while on the boat.

That was my first thought.

OleBird 22-11-2019 09:37

Re: Troubleshooting Drained batteries and Dead Charger.
Here's a trick that might recover your battery if its not damaged.

Connect a similar battery in parallel, + to +, - to -, then connect and turn on your charger. Let it charge for 12 to 15 hrs - monitor the batteries to make sure they are not running hot - charger too. This will "fool" the charger and let it try to charge both batteries. If the original battery is not damaged (warped and shorted plates) it should recharge. I've only done this successfully with flooded lead acid batteries. AGM's are a little different animal.

Always, always disconnect the charger, the negative side of your battery first - then the positive - and never work on the dc system with the battery connected. In addition to a hydrogen gas hazard, a 12 volt battery can easily melt a cresent wrench in your hand resulting is serious burn that can be very hard to heal. Never wear rings or other jewelry when working on DC - or AC powered systems.

It's not black magic, but some knowledge of basic electricity will help and keep you out of trouble. READ UP!:wink:

Cheechako 22-11-2019 09:55

Re: Troubleshooting Drained batteries and Dead Charger.
1) Check the water in the batteries. If low fill and recharge.
2)Charge the batteries a good long time. Then disconnect the + cables to the batteries. Check each battery voltage after it sits overnight or a few hours. They should be about the same. Maybe 12.4 volts. If one is quite low you have a shorted battery which has been draining the rest down.

# 2 is fairly common. The shorted battery will be quite warm while/immediately after charging.

Ionlydream 22-11-2019 12:21

Re: Troubleshooting Drained batteries and Dead Charger.
I don't think that most people have not really touched on your problem. I think that your charger is dead! With a dead charger it does not matter what shape your battery is in or what you use....

Get a new charger! Before replacing the old charge (and someone did mention this) ensure that your system does not have a short circuit. Get, borrow, (temporarily steal from your car) a battery that you know is charged. Disconnect the battery in the boat, turn off all electrical and electronics on the boat. Using a set of jumpers connect the known good battery, if there is a spark you need to look for crossed wiring or a short circuit somewhere. This needs to be dealt with before doing anything else.

If there is not spark, start turning on devices 1 at a time, only every having 1 device on. If they all work then you should be okay replacing the charger and once the battery has charged (let it fully charge) you can then start using the devices again.

As long as you have the boat battery disconnected it might not hurt to take it to a garage or a store that does batteries and have them test it to ensure it's is working well.

Good Luck

Disailor 24-11-2019 21:57

Re: Troubleshooting Drained batteries and Dead Charger.
My grp27 batts are under the 1/4 berth mattress - pain to get to. Solution was a piece of almost mattress sized plywood that is hinged at the outboard edge & fitted with a ratcheting block/tackle. Pull a rope & batts are exposed! Oh yeah, to fill them I use an enema bag with the squeeze shut-off. One hand has flashlight the other to water filling tube. A delight to use!

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