dead battery(ies)?

[richk]

Went to the boat last night and saw the house battery bank indicated a little over 8v. Turned on charger for a few minutes, it didn't climb much. Started engine, ran a bit, turned off. House bank showed a little over 14v. turned off battery charger and after a bit it went down to 8 again.

Dead battery bank (both AGM 4D's)? Just one? How to tell?

 

[whatfiero]

You have to seperate and charge one at time then volt test 24 hr to check state . if your replacing all in that bank must be same type and age

 

[woodster]

separate them and charge them back up to the proper voltage and then let them sit for a few days and check wit a volt meter and see if you have the proper voltage ...checking a battery that has just been charged off the alt will not tell you much they have to sit at rest to get an accurate reading ...just noticed you have a marlow hunter ...they cant be that old and may still be under full warranty get them replaced asap...then find out what caused them to die in the first place....oh and they may bounce back to life ...but i wonder if YOU can trust them ...some can some can't

 

[Alexander38]

If they have cell compartments, maybe refill those with distilled water?

 

[Don S/V ILLusion]

Let's review - before you run off trying to charge these batteries reading at 8 V, consider what will happen when you try that on a battery with one or more shorted cells.

Bad idea!!!

Before doing anything, explain how you managed to start an engine from a battery bank reading 8V.

Next, what is sp gr of each cell, are they all full, is your charger temp compensated?

Absent knowing these and other unknowns, rushing into blindly to start charging them is not wise.

 

[woodster]

he used his start bank to start the engine....the house bank is agm's no place to put water

 

[richk]

The batteries are all AGMs, 4D's. As stated, I can start the engine with the starting battery. Problem's in house bank.

 

[Stu Jackson]

Separate the two batteries. Check each individually.

 

[richk]

Thanks

 

[Don Lucas]

8V = past dead and decomposing

 

[Don S/V ILLusion]

The batteries are all AGMs, 4D's. As stated, I can start the engine with the starting battery. Problem's in house bank.

Didn't see where you indicated using a start battery for engine but regardless, simply turning on a charger with no mention of consideration of consequence or lack of due diligence can be very dangerous advice.

 

[Bill Roosa]

Probably have a bad cell in the (or one of them if more than one) house bank. Take the terminals off of each battery and measure the voltage. wait 1/2 hour and measure again. if the voltage came up at all the battery is probably OK and you have a drain. If one comes up and the other does not then the one that did not has a bad cell and took his brother with him.