Batteries dont reach 100% charge

[j04n]

Hi all, I'm getting bored with props so was wondering if you could help me with an electrical matter?

 

I recently changed every battery on the boat and tidied up the wiring as there were positive and negative cables coming off different batteries within the domestic bank. Just out of interest I have 6 110Ah wet maintenance free Numax leisure batteries. Yes, Ive gone cheap and chearful! They are charged via a fairly significant 160 amp alternator and I also have an electrolux 3.5kw travel pack which supplies 240v ac to a Mastervolt 100/2000 Inverter/ Charger with MICC remote controller.

 

All works well from a supply point of view but after using the inverter off grid I can never get the MICC to display 100% charge even after going back on grid without manually resetting the amps. The closest I have managed to get is 94% but that is playing with the settings and including 100% charging efficiency which we know is not possible. The more charge/ discharge cycles I do before going back on grid the further out of sync the MICC seems to be. I am confident the batteries are being fully charged, once back on grid, but the MICC doesnt seem to be counting all the amps which are going back into the batteries leaving the MICC percentage display short and minus some amps.

 

As a side I have never been totally sure whether the charger should be on whilst using travel power or not. Of course the Mastervolt has to be on but I am talking specifically about the charger part of it. It doesnt seem to matter either way but I have decided to leave it off as the alternator does charge the batteries directly anyway as this can be seen from the display on the MICC, amps going in.

 

When I bought the boat nobody was able to offer advise on how the system should work.

 

Any advise would be much appreciated.

 

ps. apologies if the title is misleading. I believe the batteries do achieve 100% charge but the MICC controller displays something less.

Edited September 27, 2016 by j04n

[dor]

It won't take too long for your 160A alternator to only be putting in about 30 or 40 amps anyway, so no point using the Travelpower as well. The charging current is determined by the batteries, not the source of the charging unless you increase the voltage.

[RLWP]

The charging current is determined by the batteries,

 

And you have a lot of batteries

 

Richard

[cuthound]

With my Victron Combi, I have to periodically reset the SoC percentage meter to keep it in sync with actual battery SoC when I know the batteries are fully charged, as indicated by the tail current being <1%.

 

I assume the Mastervolt will have the same facility. Check in your manual.

[BruceinSanity]

Please don't tell us that you've rewired the bank so that the pos and neg are now on the same battery...

 

As a minimum, they should be from opposite corners. With a big bank, more complex connections work even better.

 

See this web page: http://www.smartgauge.co.uk/batt_con.html

[nicknorman]

If the MICC of way short of 100% when the charge current has fallen to say 1% (6A or so) and if this only happens when charging via the alternator, then chances are the MICC's shunt is wired incorrectly. Probably the domestic battery -ve is connected directly to the engine battery -ve whereas it should not be - the engine battery -ve should be connected to the other side of the shunt. NOTHING should be connected to the domestic batteries -ve except the shunt.

 

This seems to be a common installation error by boatyards who don't really know what they're doing.

Edited September 27, 2016 by nicknorman

[WotEver]

Any Ah counter like the MICC will always tell lies about the SoC. The way to determine 100% charge (or thereabouts) will be to see when your 6 x 110Ah batteries are only taking around 13A charging current or when the charging current hasn't dropped over a period of 45 minutes or so.

 

A SmartGauge will track the true SoC during discharge if you wish to do so.

[j04n]

With my Victron Combi, I have to periodically reset the SoC percentage meter to keep it in sync with actual battery SoC when I know the batteries are fully charged, as indicated by the tail current being <1%.

 

I assume the Mastervolt will have the same facility. Check in your manual.

Yes, I do reset manually was just hoping to avoid.

Please don't tell us that you've rewired the bank so that the pos and neg are now on the same battery...

 

As a minimum, they should be from opposite corners. With a big bank, more complex connections work even better.

 

See this web page: http://www.smartgauge.co.uk/batt_con.html

I've seen that thanks and wired according to the last one. Looks a bit of a rats nest but i understand the theory.

If the MICC of way short of 100% when the charge current has fallen to say 1% (6A or so) and if this only happens when charging via the alternator, then chances are the MICC's shunt is wired incorrectly. Probably the domestic battery -ve is connected directly to the engine battery -ve whereas it should not be - the engine battery -ve should be connected to the other side of the shunt. NOTHING should be connected to the domestic batteries -ve except the shunt.

 

This seems to be a common installation error by boatyards who don't really know what they're doing.

I'll check that out thanks. I know they not connected directly to each other but not sure which side of the shunt they connected.

Any Ah counter like the MICC will always tell lies about the SoC. The way to determine 100% charge (or thereabouts) will be to see when your 6 x 110Ah batteries are only taking around 13A charging current or when the charging current hasn't dropped over a period of 45 minutes or so.

 

A SmartGauge will track the true SoC during discharge if you wish to do so.

I did wonder if I was just going to accept that I will have to keep resetting it manually. thanks

Edited September 27, 2016 by j04n

[nicknorman]

Just for clarity, the MICC will reset to 100% when all the below are satisfied

 

1/ All the AH taken out have been replenished (the absolute number, not taking into account charge efficiency)

 

2/ The voltage is up at a voltage that means the batteries are being charged

 

3/ The charge current has fallen below the set value

 

4/ The above conditions have been satisfied for a set time.

 

So my suspicion is that you are not satisfying 1/. With the -ve issue I mentioned, the shunt will be registering all the AH taken out, but not registering all the AH being put back in due to the alternative parallel current path via the engine starter battery -ve. Under that circumstance, even when you go back onto shore power, the batteries are already charged and so don't take any significant current and 1/ remains unsatisifed.

[j04n]

Just for clarity, the MICC will reset to 100% when all the below are satisfied

 

1/ All the AH taken out have been replenished (the absolute number, not taking into account charge efficiency)

 

2/ The voltage is up at a voltage that means the batteries are being charged

 

3/ The charge current has fallen below the set value

 

4/ The above conditions have been satisfied for a set time.

 

So my suspicion is that you are not satisfying 1/. With the -ve issue I mentioned, the shunt will be registering all the AH taken out, but not registering all the AH being put back in due to the alternative parallel current path via the engine starter battery -ve. Under that circumstance, even when you go back onto shore power, the batteries are already charged and so don't take any significant current and 1/ remains unsatisifed.

It is 1/ which is not being achieved although the batteries are definitely fully charged as 2/ and 3/ are achieved. I've looked at a photo I took and the starter battery negative goes to a common earth on the hull but the domestic battery bank negative appears to go off else where. I'm away on business so cannot check physically until the weekend.

[MHS]

Hi j04n

 

We have 8 110Ah Numax leisure batteries. They are now 2 years old and still working really well. We have a 175A alternator and 400w solar.

 

I am really pleased with our set up, and hope you will be too.

 

Cheers

 

Mike

[j04n]

Hi j04n

 

We have 8 110Ah Numax leisure batteries. They are now 2 years old and still working really well. We have a 175A alternator and 400w solar.

 

I am really pleased with our set up, and hope you will be too.

 

Cheers

 

Mike

 

 

8?! that must be about the limit is it Mike? ...... how long do they last off grid? I get about 3 days off six in the summer, 4 at a push but I suspect more like 2 in the winter as the diesel central heating pump draws a bit........ so far so good! ........ There were 4 110AGM's in the domestic bank when I bought it, 1 110AGM as a starter battery and 2 110AGM's for the bow thruster. Which I thought was a total waste for the starter and bow thruster applications. Replaced the starter battery with a standard 75Ah starter battery and the 2 bow thruster batteries with 2 75Ah starter batteries and what a difference! Definitely more punch in the bow thrusters despite smaller, cheaper batteries, but better suited to the application. Mind that maybe because the old batteries were past there best. 9 years old and the boat hadnt been used for 2 years so I guess that didnt help.

 

Cheers

 

John

[ditchcrawler]

8?! that must be about the limit is it Mike? ...... how long do they last off grid? I get about 3 days off six in the summer, 4 at a push but I suspect more like 2 in the winter as the diesel central heating pump draws a bit........ so far so good! ........ There were 4 110AGM's in the domestic bank when I bought it, 1 110AGM as a starter battery and 2 110AGM's for the bow thruster. Which I thought was a total waste for the starter and bow thruster applications. Replaced the starter battery with a standard 75Ah starter battery and the 2 bow thruster batteries with 2 75Ah starter batteries and what a difference! Definitely more punch in the bow thrusters despite smaller, cheaper batteries, but better suited to the application. Mind that maybe because the old batteries were past there best. 9 years old and the boat hadnt been used for 2 years so I guess that didnt help.

 

Cheers

 

John

How do they tie into your charging system, could some of your Ah be going that way?

[j04n]

How do they tie into your charging system, could some of your Ah be going that way?

Quite possibly. Something else I need to trace through as the electrical drawings are pretty basic to say the least. There are 3 alternators in the system. I have just added a volt meter to the bow thruster battery circuit because I didnt think they were charging and my fears seem to have been confirmed. I say seem because there was no noticeable voltage increase when I started the engine. The other possibility is too big a voltage drop from the alternator to the bow thruster batteries which are mounted at the front of the boat so a 17 metre run of cable. I need to put a volt meter across the alternator. In addition I am thinking of making use of the 5a trickle charger in the Mastervolt 100/2000 which according to the literature is connected to the starter and bow thruster batteries but from what I can see it isnt. So the starter and bow thruster batteries are currently only charged from the alternators......... sorry! started rambling........ nothing to do with your question or the original post!

Edited September 27, 2016 by j04n

[j04n]

Sorry for going off piste ......... again! ....... but ive just had a thought. I have read that you must never disconnect your batteries while the alternator is running as you can cause serious damage to the alternator. Not that I can see any reason why anybody would want to but what happens if you blow the thermal trip, like on the bow thruster? Isnt that the same thing?

Edited September 27, 2016 by j04n

[MHS]

8?! that must be about the limit is it Mike? ...... how long do they last off grid? I get about 3 days off six in the summer, 4 at a push but I suspect more like 2 in the winter as the diesel central heating pump draws a bit........ so far so good! ........ There were 4 110AGM's in the domestic bank when I bought it, 1 110AGM as a starter battery and 2 110AGM's for the bow thruster. Which I thought was a total waste for the starter and bow thruster applications. Replaced the starter battery with a standard 75Ah starter battery and the 2 bow thruster batteries with 2 75Ah starter batteries and what a difference! Definitely more punch in the bow thrusters despite smaller, cheaper batteries, but better suited to the application. Mind that maybe because the old batteries were past there best. 9 years old and the boat hadnt been used for 2 years so I guess that didnt help.

 

Cheers

 

John

The 8 are the domestic bank. Will last approx 2 days in winter if solar is really low, though we are quite power hungry with a large TV etc

They charge off the 175A alternator and the separate starter and bow thruster batteries use the 2nd 45A one.

[WotEver]

Sorry for going off piste ......... again! ....... but ive just had a thought. I have read that you must never disconnect your batteries while the alternator is running as you can cause serious damage to the alternator. Not that I can see any reason why anybody would want to but what happens if you blow the thermal trip, like on the bow thruster? Isnt that the same thing?

The trip is on the motor, not the batteries. So if the motor trips the alternator is still attached to the battery.

 

The 'danger' of disconnecting an alternator is mostly relevant when that alternator is working hard into discharged batteries.

[j04n]

The trip is on the motor, not the batteries. So if the motor trips the alternator is still attached to the battery.

 

The 'danger' of disconnecting an alternator is mostly relevant when that alternator is working hard into discharged batteries.

I understand your logic but mine certainly has a trip on the alternator side also. There is no mistaking the diameter of the cable.

[nicknorman]

I understand your logic but mine certainly has a trip on the alternator side also. There is no mistaking the diameter of the cable.

 

Presumably the BT batteries are charged by the same alternator as either the engine or domestic batteries, so that if the BT charging cable trip opens, the alternator remains connected to the other battery. As such it wouldn't be damaged.

 

The BT charging cable will likely be a long run down the boat and the trip is probably to protect against a possible short circuit in the wiring.

[WotEver]

Presumably the BT batteries are charged by the same alternator as either the engine or domestic batteries, so that if the BT charging cable trip opens, the alternator remains connected to the other battery. As such it wouldn't be damaged.

 

The BT charging cable will likely be a long run down the boat and the trip is probably to protect against a possible short circuit in the wiring.

^^^^ this.

 

You wouldn't have a thermal trip on the thruster battery charging cable for any other reason.

 

Tony

Edited September 28, 2016 by WotEver

[j04n]

Presumably the BT batteries are charged by the same alternator as either the engine or domestic batteries, so that if the BT charging cable trip opens, the alternator remains connected to the other battery. As such it wouldn't be damaged.

 

The BT charging cable will likely be a long run down the boat and the trip is probably to protect against a possible short circuit in the wiring.

Good point! Now you mention it the literature did state that BT and starter battery are on the same alternator but as I have 3 alternators I keep assuming 1 - domestic, 1 - starter and 1 - BT. But now youve reminded me it is more likely 1 - travel, 1 - domestic and 1 starter and BT........ then again when the domestic batteries are depleted they do take a charge in excess of 140amps and I only have one alternator capable of that so it is more likely 1 - travel and domestic, 1 - starter and BT and 1 - ????? think I'm going to have to trace it!?

Edited September 28, 2016 by j04n

[nicknorman]

Yes one of the alternators will be the high voltage travelpower one. You can identify it by the silvery braided wiring loom.

Edited September 28, 2016 by nicknorman

[WotEver]

Yes one of the alternators will be the high voltage travelpower one. You can identify it by the silvery braided wiring loom.

And that won't be charging anything - it's purely for 230V.

[nicknorman]

And that won't be charging anything - it's purely for 230V.

... Although it can be used to charge, via the Combi.

[WotEver]

... Although it can be used to charge, via the Combi.

Of course, but I was picking up on OP's conclusions as to which alternator charged which bank. The TP won't be wired to any bank.