Battery combiner not working with low voltages

[simonpickard]

Originally Posted by Jd1

This is actually exactly how it is supposed to work. Your first battery gets charged until the threshold voltage is reached and then the second bank is connected to the system.
Just because you turn on the engine, there is nothing saying that you will magically see over 13V at the battery. The state of charge of the battery determines that voltage. If the battery is discharged enough and the alternator is small(ish) then the battery will simply suck down the voltage supplied by the alternator. The length of time the voltage stays below the 'combine' threshold is determined by the battery state of charge, the battery condition, the battery capacity and the capacity of the alternator.
The function of the automatic combiner is to charge both batteries and I would expect that if you run your engine long enough that is exactly what happens (primary battery first and when sufficiently full the secondary battery gets switched into the circuit)

How long should this take though? I've ran the engine for hours and if the house bank is low it never seems to kick over to it. I go back on shore power and then it will work fine again once the house bank is back above a certain level.



Please visit my blog:
www.sailing-interlude.com

[transmitterdan]

It sounds like you have the house bank charged from the shore power charger. And the combining relay is sensing the house bank and when it gets up to a certain voltage then it combines. But the alternator is connected to the start battery.

For this to work the shore charger and the alternator need to be connected to the same bank (either house or start is up to you). The sense wire for the combining relay goes to whatever bank has the charging source.

[Maine Sail]

Guys,

The Cyrix is a bi-sensing device so will sense voltage on either bank.

My guess is this is possibly another situation of relay cycling due to Victron giving instructions for installation which suggests connecting all charge sources to the start battery... I fix these situations with a fair bit of regularity..

Connecting to start first is bass ackwards on vessels with large house banks that routinely get deeply cycled. This can cause the relays to cut in and out, in sand out until house bank voltage is finally high enough to remain latched.

This whole fear mongering campaign started with Charles Stirling scaring everyone into believing you "must" charge the start battery first... He did this because he had a product to market... Course this is an entire topic unto its own..

The only other issue could be in the neg for the relay or a fuse in one of the pos leads.. Be sure the neg is connected to the 86 terminal and has continuity to battery negs...

Yandina and Blue Sea ACR's are perhaps the most reliable pieces of electrical gear I install. The Cyrix never wowed me much but they are simple devices with most issues related to installation.....

[simonpickard]

So if I get into this situation how do I get out of it?
I was thinking of installing a bypass switch which effectively misses out the combiner. Let both house and starter charge then turn the bypass back off.

I got the boat new so would like to think it wasn't an install issue.
I'm not sure how else it would be wired?

[transmitterdan]

Simon,

I suspect that when the house bank is low (12.1V) and the Cyrix relay senses the starter battery coming up it connects. Then the voltage drops suddenly because the house bank can't come up that quickly. Then the Cyrix drops out. It has a time delay as well as rate of change in voltage as part of it's decision making. Maybe it is too smart for its own good and doesn't ever get convinced it should combine.

The manual says you can install a switch that will "force" it to combine. Connect a switch between terminal 85 and the house bank (with a really tiny 0.1A fuse close to the house bank). Such a switch may be already there if you look for it. It may be just a pushbutton switch. But you can put a toggle switch across the pushbutton and the combiner will stay on as long as you have the toggle switch closed.

[simonpickard]

I had this switch installed. As far as I can tell though it is only to allow charge from the house to be linked to the starter so one way. When I had the issue I tried this switch and still got no charge into the house. I think this is why I will install another switch that bypasses the combiner completely.

I have no idea why it is designed this way. It's a huge safety fault if at the very time you really need charge that these combiners won't allow it.

[transmitterdan]

Simon,

If you force the combiner on then charge should always flow from the charged battery to the other side. It is just a relay and can't control the direction of current flow.

You might try something. When the engine is running turn on the manual forcing switch and measure the voltage across the 2 big terminals on the relay. Put the red meter wire on the battery terminal and the black meter wire on the house terminal. The voltage should be very nearly zero.

[simonpickard]

I will try that. I didn't see any charge going into the house bank though when I flipped this switch.

It only stays open for 30secs also.

[siboneysail]

As mentioned before, your system is wired backwards. A starting battery rarely gets discharged from cranking the engine. Boat builders get lazy since the engine comes prewired with the alternator connected to the starter and the starting battery. The safety aspect is BS. The alternator should be connected to the house bank directly, and the combiner can the be wired from the house bank to the starting battery. The best way to do this is to use a diode(schotky diode for low voltage drop) in series with a 30A breaker. This way If/when the starting battery fails, it will trip the breaker and not destroy the diode. If you see a tripped breaker you switch over and start from the house bank. It is usually a bad idea to parallel a small starting battery with a large house bank. If the starting battery is shorted, the energy stored in a large house bank might make the shorted battery vent violently( explode).

[transmitterdan]

Originally Posted by simonpickard

I will try that. I didn't see any charge going into the house bank though when I flipped this switch.

It only stays open for 30secs also.

Simon, so long as the small switch is on the relay should stay closed and keep the batteries connected. The 30 second timeout is only when the switch is pressed momentarily.

How do you know there is no charge going to the house bank?

[simonpickard]

The battery monitor I have shows no amps going in.

[smac999]

sounds like you have an internal reg alt. and wired straight to engine battery. probably though starter post if all stock. no issue with this. if a small alt, under 80a I would leave it this way.


If your alt is not brining your engine battery up over 13v you have a problem with the alternator or wiring.


10min delay is crazy. the blue sea acr is 30 secs. but also needs over 13v as well.


you should be over 14v on the engine battery with engine running. that'll probably drop once the acr kicks in depending on size of house bank. it may even contine to click on and off if the house bank is really big and your alt is small.


I would get your alt looked at. but first confirm with a multimeter the actuall voltage at engine battery and alternator output post.

[smac999]

Originally Posted by simonpickard

How long should this take though? I've ran the engine for hours and if the house bank is low it never seems to kick over to it. I go back on shore power and then it will work fine again once the house bank is back above a certain level.



Please visit my blog:
www.sailing-interlude.com

where is your shore charger connected too? probably both banks. if so no way to know if the combiner is working or not. as both would get charged either way.

if it's only connected to house. then your combiner might be one directional. some of the bep's are.

if the charger is connected to the start battery only. and the combiner works and charges your house. then see above. bad alt.

[simonpickard]

Originally Posted by smac999

sounds like you have an internal reg alt. and wired straight to engine battery. probably though starter post if all stock. no issue with this. if a small alt, under 80a I would leave it this way.


If your alt is not brining your engine battery up over 13v you have a problem with the alternator or wiring.


10min delay is crazy. the blue sea acr is 30 secs. but also needs over 13v as well.


you should be over 14v on the engine battery with engine running. that'll probably drop once the acr kicks in depending on size of house bank. it may even contine to click on and off if the house bank is really big and your alt is small.


I would get your alt looked at. but first confirm with a multimeter the actuall voltage at engine battery and alternator output post.

I can always see over 14v on the starter. That has never been an issue so I don't think it's the alt.



Please visit my blog:
www.sailing-interlude.com

[simonpickard]

Originally Posted by smac999

where is your shore charger connected too? probably both banks. if so no way to know if the combiner is working or not. as both would get charged either way.

When on shore power I see a charge rise on both starter and house.



Please visit my blog:
www.sailing-interlude.com