Blue Sea ACR and DC to DC Charger?

[john61ct]

I have yet to learn what BB's BMS balancing setpoints are.

You need to get to - and hold for some time - above the "start balance" voltage.

How long will depend on the "balancing current rate" and just how unbalanced the cells are.

If you just fast-charge to a setpoint and stop every time, the imbalance may only grow.

Holding longer but at a very low current rate would be a decent compromise.

My "bigger picture" point is that IMO the balancing requirements of a cheap BMS should not be driving the charge profile. With a bigger system costing many thousands, it is worth buying top quality cells from known-good makers, and investing in a better set of infrastructure electronics more conducive to optimal longevity.

And yes, I target lifespans much longer than vendor ratings support.

 

[Srpat]

Back to my original post...

I still don't understand why I couldn't run a 2nd DC to DC charger off the alternator to finish the charging of the batteries.

The way I understood it the blue sea acr would charge the bulk of the batteries, but to finish and get a complete charge I would need solar, which would charge at a higher voltage, a shore power charger, or DC to DC.

Even a 20 amp charger seems sufficient when combined with the ACR to get a lot of charge off of my 340 amp dual alternators. Maybe I wasn't clear, but I don't intend on running this inline with the ACR, but in addition to it.

 

[Srpat]

But couldn't I let both run at the same time? The alternators should have no problem with an additional 20 amp load. It certainly would be easiest to have both the charging relay and dc to dc charger run anytime the engine is on.

Nothing wrong with it. Its a sound idea. I think its Ctek has a similar system called "Smart Pass".
To make it to work automatically will require homebrew of voltage & current monitoring and appropriate signaling to switch open the ACR then switch on the DC to DC apparatus.
Or monitor voltage and current yourself, then manually switching over to DC to DC when its time for finish charging.

 

[luthj]

It's not possible to have a relay in parallel with a DCDC charger. It's the same as bypassing the charger... your are fundamentally misunderstanding how these devices work.

An ACR is a SWITCH, not a current or voltage modifying device.

 

[Alloy]

I've been scratching my head on how to charge my batteries in my F550 shuttle bus. Planned set up is 4-600 amp hours of 6v golf cart batteries.

F550 has dual alternators that have the possibility to push a lot of amps, so the only ACR I could find was the ML series from Blue Sea that are good for 500 amps. However, it seems like the ACR will not fully charge batteries because it is not a smart battery charger.

I am considering two options. One, a small solar system that has a smart battery charging profile I like built in to the controller. Or two, an additional 10 or 20 amp dc to dc charger in addition to the ACR. But I can't find anybody that's done that before.

Can you clarify the AH of the battery bank? What is 4-600amp hour of 6V?

 

[john61ct]

Concurrent parallel while an Interesting Question, is not a good idea in any case.

A high current capacity A/B/Off switch - BSS makes good ones - should be used to maximize Bulk stage current amps at whatever voltage.

As the target bank gets to 85-90% Full (SoC meter) then switch over to the DCDC side to get a proper finish, then once Full isolate the bank with the Off choice.

 

[john61ct]

Did you ever tell us what voltage your alternator puts out?

Make sure whatever solution you choose, never allows a load dump conditiin.

 

[john61ct]

Did you ever tell us what voltage your alternator puts out?

Make sure whatever solution you choose, never allows a load dump condition.

 

[shade]

It's not possible to have a relay in parallel with a DCDC charger. It's the same as bypassing the charger... your are fundamentally misunderstanding how these devices work.

An ACR is a SWITCH, not a current or voltage modifying device.

Yep.

Maybe I missed something, but I still haven't seen why the OP wouldn't just charge the lead house bank directly off one of the alternators. An ACR could be integrated if the ability to easily use the large house bank for starting was desired, otherwise, I'd skip it and go direct. I wouldn't bother with a DC-DC charger unless there was evidence of abuse to the alternator.

 

[shade]

I only have a degree in electrical engineering and have never really done a deep dive into batteries. The founder of Battle Born has degrees in Physics (BS Villanova) and Engineering (PhD, Caltech), and is also a professor who teaches at UNR in the Physics department. Absent evidence to the contrary, I'm going to go with his judgment.

It's not that BB doesn't know what they're doing, but their overall goals may not be the same as the end user.

I really think they should add Bluetooth monitoring of the internal BMS, even if they don't allow user programming. Adding that shouldn't cost much, and publishing the information John mentioned would be free. Both would be welcome changes, and help to set BB apart from the market.

 

[john61ct]

I wouldn't bother with a DC-DC charger unless there was evidence of abuse to the alternator.

Not so much the alt with lead, but if it's an expensive bank, and alt only puts out 13.x volts, will quickly murder it.

 

[shade]

Not so much the alt with lead, but if it's an expensive bank, and alt only puts out 13.x volts, will quickly murder it.

Agreed. As you requested, knowing the alternator output voltage is important. I was thinking more about overtaxing the alternator. That probably won't be a problem with a lead bank of that capacity, will it?

 

[john61ct]

No.

Say 150A actual continuous.

FLA with CAR at 0.15C would need to be over ~1000Ah

AGM might get up to even over .5C but it's for such a short time I wouldn't be worried at all until 500Ah.

Plus all you need is a mechanism that de-rates the VR based on overtemp, which many modern rigs do.

In the other direction, lead is basically self-limiting, even if the alt made 500A available the bank won't pull more than it can stand, vendor max amp charge specs are just legal CYA.

But voltage does need to be well regulated.

And GEL may well be an exception there, very sensitive to overcharge in general.

 

[Rbertalotto]

Plan on spending lots of time here if you want to learn all there is about LiPo batteries....None better!

What's new

diysolarforum.com

Here is a great video on the RENOGY DC to DC Charger and how it works.


I recently bought one and tested it on both my 150amp alternator in my Toyota Venza and in my 220amp alternator RAM 2500. Amazing product and the CORRECT way to safely and efficiently charge an auxiliary battery.

 

[shade]

Amazing product and the CORRECT way to safely and efficiently charge an auxiliary battery.

I think you meant "a good way".