Smartbank w/ Smartgauge - contactor becomes very hot

[bikesherpa]

On my boat, I installed two years ago a Smartbank split-charge system (including its Smartgauge display) that connects the service and engine battery banks (100Ah and 300Ah respectively) via a contactor.

I initially used the original manufacturer-supplied contactor (on which no brand is shown). When energized for a long time, the contactor always became very hot. I did not measure the temperature, but you could only touch it for a few seconds, so I guess >50-60C

As a precaution, I therefore decided to change the contactor with a branded Albright SW80-435P.
However, the new Albright contactor becomes very hot when energized too. At some point this summer, I noticed that it was so hot that it failed to operate (connect the two banks). After cooling down, it started operating normally again.
To be noted that the contactor might be required to stay energized for days. I am very often connected to the marina 220v main (with battery charger ON in "mantain" mode), and have solar panels. My battery banks may stay >13V for days.

I therefore supposed that the overheating could be caused by: 1) too much current flowing through the contactor or 2) the power-saving "intermittent" feature of Smartbank to energize the coil could actually generate more heat.
I then tested (energized) both contactors (original and Albright) with a lab DC power supply and no load and they got still very hot.

Based on the above, I have now doubt that these types of contactors are suitable for this split-charge application, where the coil is almost always energized.
Even if they operated correctly when hot (spec. operating temp is only 60C), they would still dissipate a lot of energy - a few dozens watts.
With a 100W nominal solar panel, in reality I get only 50-60W during daylight and the contact eats them up.

Are there better contactor alternatives ? Maybe designed for continuous/always ON applications, or bistable contactors with some electronic control on board to be interfaced to the Smartbank ?

[john61ct]

This may be overkill, certainly as reliable as it gets

https://www.bluesea.com/products/770...enoid_-_12V_DC

Also with manual switch
​ https://www.bluesea.com/products/770..._-_12V_DC_500A

[bikesherpa]

Originally Posted by john61ct

This may be overkill, certainly as reliable as it gets

https://www.bluesea.com/products/770...enoid_-_12V_DC

Also with manual switch
​ https://www.bluesea.com/products/770..._-_12V_DC_500A

Yes, this could be a good solution.
I can put some electronic control between the Smartbank controller and the Bluesea latching solenoid to transform the ON-OFF continuous voltage of Smartbank to a momentary ON-OFF impulse required by the latching solenoid. I could do that with an arduino board maybe.

[Colin A]

You can check what voltage the contactor is seeing at the coil. That can cause an issue. As said a latching one may work. You may want to contact Albright as well. I have noticed their catalog lists different coil duty cycles but not sure how that works out in the part#.

[john61ct]

Originally Posted by bikesherpa

Yes, this could be a good solution.
I can put some electronic control between the Smartbank controller and the Bluesea latching solenoid to transform the ON-OFF continuous voltage of Smartbank to a momentary ON-OFF impulse required by the latching solenoid. I could do that with an arduino board maybe.

Would this be simpler?

http://www.ebay.com/itm/192279230122

Can be repurposed different ways

[bikesherpa]

Originally Posted by john61ct

Would this be simpler?

Low / Over voltage Cut-Off 6-32V 40-240A | eBay

Can be repurposed different ways

It seems a very neat device and costs less than the Blue System latching relay. Voltage connect/disconnect levels and timings can be easily programmed, so it could potentially replace the whole Smartbank control.

[john61ct]

I really like the idea of relays under control of a good SoC meter.

BMV-702 can trigger off mid-bank imbalance if a cell goes bad.

But yes has potential as standalone, for example LVD/OVD DIY BMS-style protection, expensive LFP bank want belt & suspenders both.

[smac999]

Just replace The whole system with an Bluesea acr.

[bikesherpa]

Thanks for all suggestions.
I basically have 3 options :
1. Replace the existing contactor with a SSD one (e.g. the mosfet battery protector by Bed Electronics for about EUR 115 shipped)
2. Install a purpose-built, low operating power, ACR and discard the smartbank (e.g. BS ACR 7610 for about EUR 70 shipped)
3. A MOSFET battery isolator (e.g. ECS by Quick with 0,05-0,2 VDC loss, for about €130)
Has anyone any experience with MOSFET isolators/separators ? Are they reliable?

[john61ct]

As general technology they're great, but I'm sure the specific units vary. Don't undersize wrt current.

Blue Sea has their ArgoFET line.

Let me know if you're getting rid of the SmartBank.

[sailcrazy]

Based on advise from a professional, certified marine electrician, we bought and installed a Balmar Duo-Charge between our house bank and start battery. Essentially, it's a 1-way check valve, that allows the house to recharge the start battery up to its (the house bank)voltage level, but not the other way. It's totally automatic, and has worked flawlessly for us since I installed it in 2013. I still monitor the start battery via 1 side of our Link 20 Battery Monitor, but have done nothing to control the charging of the start batt since installation.

[hellosailor]

You might want to contact Albright to ask their thoughts. That contactor (in the US, we'd call it a relay) seems to be rated very 100% continuous duty in 100A applications.

Which of course makes me ask a question about something you may have omitted. If you put an ammeter on the power line that is being controlled by the contactor, what is the actual amperage going through it? "Obviously" the problem could be excessive amperage due to some other fault, and this component is simply overheating because of that.

FETs have obsoleted relays in many power handling applications, but some of us still think a relay is robust enough, resists some types of damage better, and of course, it is easier to see and hear if it is actually working. But either one will fail if there's a more basic problem, either from the amount of amperage, or something else not right.

[bikesherpa]

Originally Posted by hellosailor

You might want to contact Albright to ask their thoughts. That contactor (in the US, we'd call it a relay) seems to be rated very 100% continuous duty in 100A applications.

Which of course makes me ask a question about something you may have omitted. If you put an ammeter on the power line that is being controlled by the contactor, what is the actual amperage going through it? "Obviously" the problem could be excessive amperage due to some other fault, and this component is simply overheating because of that.

FETs have obsoleted relays in many power handling applications, but some of us still think a relay is robust enough, resists some types of damage better, and of course, it is easier to see and hear if it is actually working. But either one will fail if there's a more basic problem, either from the amount of amperage, or something else not right.

The relay gets hot even if no current flows through it (disconnected batteries from the terminals).
I think the problem is that the relay coil is likely not rated for always ON usage.
I found on the Albright site that they can provide the coil for various usages:

COIL POWER DISSIPATION
Highly Intermittent Rated Types
20 - 30 Watts
Intermittently Rated types
15 - 20 Watts
Prolonged Rated Types
13 - 15 Watts
Continuously Rated Types
7 - 13 Watts

I assume the above coil power consumption is at 20C. In a hot Med summer, within my battery compartment the temperature can easily reach 35-40C, so the worst case scenario is that the coil has to dissipate maybe 50W of power and therefore eating up most of my solar power.
I will give Albright a call and see what they recommend. Anyway, I am now inclined to go for a MOSFET-based solution, due to its lower power consumption which is critical with a low-power solar source.

[hellosailor]

It will be interesting to hear what they say. Since they suggest this part can be used for power control on electric trucks, I would expect that to mean continuous duty. And even for a large relay, there's no reason why the coil should be carrying a lot of wattage. If the coil pulled a whole amp--which would be a lot--at 14.4 volts, that would still be less than 15 watts. Again, it could also be worth verifying how many amps the coil is consuming before you call them. Although if two different contactors were showing the same type of fault, that could point to something be wrong (or mismatched, or set wrong) on the controller or the overall configuration.
So a call to Smartbank might also be useful. This sounds a lot like one of those "it's something really simple we're just not seeing" problems.

[john61ct]

Originally Posted by bikesherpa

I am now inclined to go for a MOSFET-based solution, due to its lower power consumption which is critical with a low-power solar source.

Note the ML style relays like the Blue Sea units above, consume zero power except when changing state.