Battery question..

[casper ghost]

Hi, Took my 2 domestic batteries home to charge. One went on charge but the charger says it is fully charged, whilst the other has been on charge for a few hours and is still charging.. Not sure how this works, but as they were joined together, why would one be lower than the other. They are both the same age and type.. ?

The one that is charged has the solar panel going to it, but it's connected anyway to the other battery. The power lead comes off the battery that is still charging..

Casp'

[matty40s]

It could be that a cell has gone in one of the batteries - could well be the one that has the power cord has died..

It is always advisable to put the positive to one battery and the negative to the other in a 2 battery bank.

[casper ghost]

Hi. Yeah the positive and negative came off different batteries. These batteries were new in January this year..

Casp'

[sashastedman]

Hi

Hoping that Casper gets his answer too but wanted to ask along similar lines..

Batteries will charge from shoreline very well and hold it for some time. When relying on charge from engine, no problem starting engine but very little charge will build and hold in the three 110a domestic batteries. Could it be to do with the batteries or the alternator?

Many thanks and please redirect if suitable. This was the top post from my search.

[Grace and Favour]

Hi

Hoping that Casper gets his answer too but wanted to ask along similar lines..

Batteries will charge from shoreline very well and hold it for some time. When relying on charge from engine, no problem starting engine but very little charge will build and hold in the three 110a domestic batteries. Could it be to do with the batteries or the alternator?

Many thanks and please redirect if suitable. This was the top post from my search.

What is the rating of your alternator, (how many Amps output), and how long are you running the engine to charge the batteries when they suffer from "little charge will build and hold in the three 110a domestic batteries"?

 

It may be a faulty alternator, )one of a number of faults)

Or your Alternator belt may be too slack

Or there may simply be too little charge being created (too short a charging time)

[Tony Brooks]

Hi

Hoping that Casper gets his answer too but wanted to ask along similar lines..

Batteries will charge from shoreline very well and hold it for some time. When relying on charge from engine, no problem starting engine but very little charge will build and hold in the three 110a domestic batteries. Could it be to do with the batteries or the alternator?

Many thanks and please redirect if suitable. This was the top post from my search.

 

 

One or two alternators?

 

If its one then I would suspect excess voltdrop on the charging circuit, especially whatever is being used to split the charge.

 

To test for voltdrop:

 

Set a meter for 20V DC or 200V DC for a 24 volt boat.

 

With discharged batteries - e.g. first thing in the morning:

 

Connect the meter between the main alternator output terminal and the domestic bank positive (or any other part of the positive circuit you wish to check).

 

Start & rev the engine, note the voltage reading. More than about 0.5 absolute maximum and you have excess voltdrop on the positive. I would try to get it down to 0.25 volt though.

 

Repeat but for the negative. Your alternator may have a proper negative terminal but if not use the case. Go for the readings above BUT if you have 0.5V on both pos and neg then things bare very wrong. Ideally the negative would read almost zero.