Poor alternator

[marioxp]

I have two batteries 2 x 143AH, the alternator is standard (I think 60ah).  after I start the engine it starts charging with 50A, but it drops very quickly and after a short time it charges with 4A even though the batteries are 70% full.  it seems to me that there is some problem with the alternator, but I don't know what kind. 
Few days ago everything was ok, now I noticed that the batteries are charging poorly.  what's worse, the solar panel has weakened a lot and gives only 16w.

[SYJetzt]

Doesn't look as a faulty generator. I would suspect loose cabling somewhere around the batteries, hence the poor charging of your solar. Check all the connections and terminals in your system.

[Jeffatoms]

Consider changing the regulator to an external regulator.  We just installed a Balmar MC618, multistage regulator.  It is smart, really smart at providing a three stage charge.

[marioxp]

Doesn't look as a faulty generator. I would suspect loose cabling somewhere around the batteries, hence the poor charging of your solar. Check all the connections and terminals in your system.

Dear SYJetz,

You are right, at least as that is not problem with alternator.

We connected to the shore and the charger did a very similar thing as alternator, At the beginning, he charged with 20A, and after a while with only a couple of amperes or less. So the alternator is working fine.

We tested the splitter, (Victron mosfet) When we switch the starter and house batteries, alternator charged the same.

Could it be the batteries? But I find it a little strange that they lost 30% of their capacity almost overnight.

Or just the battery charge indicator (shunt) is disoriented, and it shows 70% (190Ah) but it's actually 100% (280Ah).

We looked at the cable connections and they seem good, no oxidation or loose connections.

[SYJetzt]

Maybe one of your batteries is defect, but i would think there is a contact issue somewhere! You could check the batteries, if you disconnect one plus pole from one battery and look, if somethi g is changing! Always keep loose battery poles well isolated to avoid short circuits! Be cautious!

[Jess21]

Maybe your batteries are not that new anymore. Depending on age, maintenance and numbers of (deep) discharge cycles your batteries deteriorate. And 70% is just the limit that batteries are considered to be replaced by new ones...

[marioxp]

I don't know what happened.

I took the batteries to the service center, they said that the batteries are in good condition, but they are half empty or empty. They recharged them. I put them back on board and reset the battery monitor. Now everything seems OK to me, the alternator is charging them, the shore power charger is charging them. My only explanation is that the battery monitor went wrong.

Only the solar panel works very poorly. On a sunny day, it charges them with max 29W, the power of the solar panel is 150W! It is possible that after only one year the solar panel has degraded.

Thank you all for your help and advice.

[Yngmar]

Coulomb counting battery monitors are notoriously wrong and get out of sync after a while. So anything that shows you a neat little percentage is usually lying, because batteries, especially lead acid ones, aren't as simple as a percent bar.

Always look at the voltage (and the load the batteries are under). Looks like your batteries weren't charging because they were full and everything worked correctly apart from the lying battery monitor

[marioxp]

Looks like the monitor did not record the charging well or counted the discharge too much.

[SYJetzt]

Depending on the type of counter you have, you can modify your settings of the counter to get better results. This needs usually detailed information about your charging system, which you can get from the manuals

[marioxp]

I don't know what type you have, but mine is a basic type, and I can only enter the battery capacity.

https://www.ebay.com.au/itm/143610934768

[SYJetzt]

I'm using a victron BMV 712, which is accurate and has a automatic calibration to 100% depending on voltage and charging current.

[marioxp]

Does anyone of you, use a battery protection device against excessive battery discharge?

[tiger79]

Does anyone of you, use a battery protection device against excessive battery discharge?

I don't.  For many of us, the biggest regular battery load is the fridge, and this automatically shuts off when the voltage drops to around 10.5v.  Most battery protection devices also shut off at 10.5v.

[SYJetzt]

Yes, i protect my lithium bank against deep discharge with a latching relay, switched by the BMS. Before we changed from lead acid to lithium, i switched off the fridge at a SOC of 50% using my victron BMV 712 and a standard relay. To keep lead acid in a good state and avoid premature ageing they should be kept at a SOC above 50%! The usual voltage level , when our fridges stop working (10,5V) is  enough for starting a engine with this discharged battery, but far to low to maintain a longer battery life.