Meaningful difference between Blue Seas ML-ACR and SI-ACR?

[abiker]

Working on a system for my truck (100A rated alternator), which I'll copy over to a few other vehicles - girlfriend's and friends' once it really works. I just read the Overland Journal review of the ML-ACR (500A, $260+hardware), seems like the choice for me. However, why not go to the SI-ACR (120A, $120+hardware), and save money? Yes, it's not a lot, but for a budget build, wouldn't I rather spend the cash on bigger cables than an overkill ACR?

I have some electrical know-how from wiring trailers, but fancy electron mazes are still a little magic to me.

Links for reference:

https://www.bluesea.com/products/7610/SI-ACR_Automatic_Charging_Relay_-_12_24V_DC_120A

https://www.bluesea.com/products/7620/ML-ACR_Automatic_Charging_Relay_-_12V_DC_500A

TIA!

 

[snare]

Another dual sensing automatic charging relay option is the Samlex 160.

http://www.samlexamerica.com/products/ProductDetail.aspx?pid=478

This has the option of a manual switch (user supplied, $5 + some wire) control.

I even found mine on an Amazon Warehouse open box deal. Been running it since September with zero issues.

https://www.amazon.com/Samlex-America-ACR-160-Automatic-Isolator/dp/B00HHRVMII

 

[DaveInDenver]

low current whilst combined self consumption

This is the main meaningful difference.

The ML part of ML-ACR means magnetic latching, which means the controller switches the relay closed and it stays closed until the controller switches it open and it stays open. During those transitions the ML-ACR is drawing some current, about 40mA, but the rest of the time in one of the bi-stable states the current consumption is small, about 10mA.

The SI-ACR is a traditional relay, when it's open (e.g. isolating) there's minimal current, about 15mA for the monitoring circuit. When the relay is closed (e.g. combined) it takes a lot of current to hold in, about 175mA. This is not a huge amount of current since presumably your engine is running but it would be true also while on solar or shore supply. Again, not a tremendous amount but something to note if you're generating 2 or 3 amps with a 50W panel perhaps.

In terms of function, they are basically similar, combining when voltage is high enough, isolating when it drops. I will mention one thing about the 500A rating of the ML-ACR, this may come into play during a self jump or winch operation even if your alternator is less than the capacity. IOW, if you want both batteries in the circuit for very high current use you have no choice but to use the ML-ACR or something similar.

 

[abiker]

Okay - let me repeat it the way I understand - for overland vehicle use, the SI-ACR would work for simple things, like just getting a dual battery to run a fridge and some lights. However, if you add another way to charge, like solar or shore supply, OR if you are self-jumping/running extremely high current (winch/inverter/etc) then the ML-ACR is required. Is that about right?

 

[DaveInDenver]

Okay - let me repeat it the way I understand - for overland vehicle use, the SI-ACR would work for simple things, like just getting a dual battery to run a fridge and some lights. However, if you add another way to charge, like solar or shore supply, OR if you are self-jumping/running extremely high current (winch/inverter/etc) then the ML-ACR is required. Is that about right?

Mostly, yes. If all you need is to combine during charging with a ~100A alternator then the SI-ACR will work fine. The main case that requires the ML-ACR is a high current parallel batteries. The 175mA holding current isn't high enough to really worry unless you're on a trickle charger/maintainer, perhaps like a 1A sized Battery Tender. But it's something to be aware of. The ML-ACR consumes the same amount open or closed.

 

[DaveInDenver]

I have a ML-ACR but never have used an SI-ACR. I'll have to grab the high speed probe and check sometime, 7A strikes me as the peak inrush number. The quiescent current is low as near as I can tell but my current probe is a 1000A/50KHz so a 100mA minimum and 1mV/A doesn't help with a meaningful measurement here (if asked right now I'd have to admit mine draws essentially nothing!).

 

[rayra]

Not sure if I'm reading it wrong or of they have the product listing wrong, but this appears to be the ML-ACR for $176 Amazon Prime, ~$80 less than mentioned above for the 500A. It's multiple products in a variable page so the description text doesn't seem to align with the model number.

https://www.amazon.com/Blue-Sea-Sys...14871892&sr=8-1&keywords=blue+sea+ML-ACR&th=1

 

[snare]

Not sure if I'm reading it wrong or of they have the product listing wrong, but this appears to be the ML-ACR for $176 Amazon Prime, ~$80 less than mentioned above for the 500A. It's multiple products in a variable page so the description text doesn't seem to align with the model number.

https://www.amazon.com/Blue-Sea-Sys...14871892&sr=8-1&keywords=blue+sea+ML-ACR&th=1

No, you didnt read it wrong. that is the correct product. There is also the listing for the one with the manual control for $191. I have noticed some people dont shop.

 

[DaveInDenver]

Forget the probe. Measure current on its negative lead.
Everybody has ampmeter what will read that low...

Exactly, I have tried using a resistor in the return but for some reason I never catch a transient anywhere near 7A. It makes no sense, there can't be that much damping and my ACR seems to work fine. I've only ever measured ~35mA quiescent with peaks around 60mA. That's why I want to borrow the stuff from work one day. I don't trust my ancient scope anymore, the vertical amp has been flaky for a few years but even so catching transient signals with a 2235 isn't ideal. LOL, there's the right way and there's my way.

No, you didnt read it wrong. that is the correct product. There is also the listing for the one with the manual control for $191. I have noticed some people dont shop.

You also have to watch Amazon, they're not always the cheapest.

I got my 7622 (ML-ACR with manual override) for $183.86 with free shipping.

http://www.imarineusa.com/bluesea7622mlseriesheavydutychargingrelaywmanctr.aspx

 

[rayra]

I'm slow as a glacier on some projects. One of my long term tricks is putting a lot of stuff on my Amazon Wish list. Periodically, Amazon will geek and cut prices on those items by 5%, 11%, 25%, trying to induce a purchase. Sometimes I notice, sometimes I notice AND have the available money to act on the reduced prices. But I've certainly noticed the pattern and sometimes take advantage of it.

Before I went for the Prime deal, I used to keep a lot of low priced items on that list, for whenever I wanted a single item and it didn't exceed their free shipping limits. Then I'd just 'pad' my order with whatever small item (which I already wanted) that it took to exceed that draw.


ON-topic, that ML-ACR is probably the solution to my self-induced problem in my other recent topic in this subforum. We shall see, after I finish my rooftop solar integration and re-wire my PowerPorts to my Aux / House side. Even 'saving' $80 with the Amazon pricing, I'd prefer not to spend the lower $180, either, if I don't have to.

 

[snare]

Exactly, I have tried using a resistor in the return but for some reason I never catch a transient anywhere near 7A. It makes no sense, there can't be that much damping and my ACR seems to work fine. I've only ever measured ~35mA quiescent with peaks around 60mA. That's why I want to borrow the stuff from work one day. I don't trust my ancient scope anymore, the vertical amp has been flaky for a few years but even so catching transient signals with a 2235 isn't ideal. LOL, there's the right way and there's my way.


You also have to watch Amazon, they're not always the cheapest.

I got my 7622 (ML-ACR with manual override) for $183.86 with free shipping.

http://www.imarineusa.com/bluesea7622mlseriesheavydutychargingrelaywmanctr.aspx

Yes, shopping includes looking beyond one source.