Using both a DC/DC and a MPPT Charger

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adric asked Apr 6, '20

Using both a DC/DC and a MPPT Charger

Hi,

I am planning on using the Victron Orion TR-Smart 12 12 30 Isolated to charge a LiFeP04 House Battery from the Start Battery of an outboard Alternator.

However, I am also planning on adding solar, to top up the house battery when we are not running the outboard. For this purpose, I am considering the Victron SmartSolar MPPT 100/30, but I am now wondering how the charging would switch between the two systems? Does Victron have a Smart integrated MPPT/DC2DC Charger? Or can it be achieved differently with Victron devices? I know of other branded products that do this.

Can I connect simultaneously both Victron units to the House battery?

Thanks,

Adri

Orion DC-DC Converters not smart mppt charging

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Answer 1 · 2020-04-06T05:14:49Z

JohnC answered · Apr 06, 2020 at 05:14 AM

Hi @adric

Yes, you can do that. They won't 'switch' as such, but will work concurrently, both charging to their own targets. They'll interact via V to some extent, and you can dabble with settings to prioritize one over the other in some circumstances.

Victron don't make combo units in this form, you choose your components from a wide range.

So you'll then have (potentially) 60A of charge capacity. Just check that your batts can handle that. Also, your Orion will/can use the full 30A, and your outboard's alternator (or stator) will need the capacity to handle that plus charge the start batt. Most outboard alts are fairly highly rated, but may be of concern if you're poking around at low rpm. They can get hot, even fail, from inadequate ventilation.

But I don't mean to concern you. Just that awareness is always a good quality to maintain.

Happy boating..

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daineric commented · Feb 09, 2021 at 12:23 AM

I'm doing the same thing on my truck and camper. A Victron BLueSolar MPPT and a Victron Smart DC Charger 12/12 18A off the alternator. I'm curious about the "dabbling with the settings" you recommend, because I'm concerned that when I'm driving in the daylight, the DC charger will sense the voltage coming off the solar panel and think the battery is full when it's not. I want to prioritize the DC charger when I'm driving, so would that mean setting the voltage cut-offs slightly higher for the DC charger and lower for the MPPT? I've currently got them set exactly the same.

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JohnC ♦ daineric commented · Feb 09, 2021 at 07:41 AM

Hi @DainEric

Yeh, that's what I meant. The 'dabbling' comes into it once you realize that the V settings of chargers may also be temp-compensated, so you have to allow for that. Also you need to look at whether you want to double-up on a full Absorption cycle from 2x chargers (if available), and how to manage that. At the end of the day you want the batts treated as if a baby with one mother, not two.

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adric daineric commented · Mar 03, 2021 at 09:23 AM

DainEric, how are things working for you with this setup? And if you are happy with it, would you mind sharing your settings? Thanks, Adri

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daineric adric commented · Mar 03, 2021 at 08:54 PM

I got it all installed, but haven't used the camper enough since then to gauge. My battery calls for 14.2-14.4 absorption and 13.2-13.4 float, so I plan on setting the DC-DC to 14.4/13.4 and the MPPT to 14.2/13.2 so hopefully that'll prioritize the DC-DC when the truck is running.

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tdsmith541 daineric commented · Nov 11, 2021 at 09:23 PM

Daineric, how did this work for you? I have a very similar setup, the only difference being the recommended float/absorption on the battery, and was planning on basing my settings on your recommendation. This approach makes sense to me.

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Answer 2 · 2020-04-06T05:54:15Z

adric answered · Apr 06, 2020 at 05:54 AM

Thanks John for your detailed reply.

Your comment about the Alternator worries me. This overheating issue at low RPM when using a LiFeP04 house battery was the exact reason why I am considering getting a Orion. But what you are now saying seems to defeat this purpose. I thought that by using the DC/DC charger I would resolve that. Are you suggesting that perhaps I should buy the smaller version? The 12 12 18. Would this impose a smaller load on the Alternator?

I have currently being using a simple Voltage Sensing Relay and my house battery is a AGM style and never had any issues. As I am considering replacing the AGM with a LiFeP04, I have read the the issue of the load on the Alternator that these batteries can cause and a distributor here recommended the use of the Orion to resolve this issue. However you know seem to be saying that the Orion does not fix this issue. Can you please let me know if

1) the Orion is the way to go

2) or if I should stay away from LiFeP04 and remain with an AGM and possibly simply doubling its capacity

3) use a multi-stage voltage regulator, like the Balmar

I would appreciate your feedback and thank you in advance.

Regards,

Adri

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JohnC ♦ commented · Apr 06, 2020 at 07:42 AM

@adric

I did say I didn't mean to concern you. Mostly because I've no idea of the size kit you're talking. But it's great you've done your homework and already well aware.

1) I'd go it. Even with pb's, and with Li's it's essential to have good charge control with V for starters.

2) My next batts will be Li's. I'll work out how to deal with them. So I can't tell you to do otherwise, hey?.

3) I don't know. I'd try to avoid anything like that myself.

You could go the smaller Orion, but we can't judge that for you. You may have an 80A alt, and 30A seconded off to a house batt shouldn't be an issue.

And we're all different. Eg I run twin 30hp with stators, not alternators. Driving into 900Ah @12V. And I don't know nor even care if they're still working (alternative charge sources, incl 48V house bank).

If you want to post up more specific info we could try, but it'll be an opinion, not necessarily gospel, from whoever might provide it.

But keep asking if you need.. :)

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Answer 3 · 2020-04-06T08:37:48Z

adric answered · Apr 06, 2020 at 08:37 AM

Thanks again John for your feedback.

I have two four stroke outboards, 150HP Mercury, but only one of these is connected to the House Battery, which currently is a 105Ah Deep Cycle AGM. I was thinking to get a 100Ah LiFeP04, with internal BMS and temperature control.

Here is the data on my Outboard Alternator/Charging system.

Any further feedback will be greatly appreciated.

Regards,

Adri

alternator.jpg (200.1 KiB)

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JohnC ♦ commented · Apr 06, 2020 at 11:54 AM

Yeh, biguns, good. Even though you're only using one.

I very much doubt you have an issue. Mercury won't be overstating the capability of their kit, and maybe even have a little up the sleeve.

Time under excess alt load and low revs may be the teller, and you could even talk to your Mercury man about that to check their experiences. You won't be the first to have done this (or worse)..

Me (yep, opinion), I'd roll with the 30A Orion, comforted that I still have another alt aboard.

Poor answer? Yeh, I'll wear that. But sometimes things get so grey that it's hard to choose. You get to do that. And I wish you well with that choice.

And then, maybe even a Cyrix combiner to join both engine batts?

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adric JohnC ♦ commented · Apr 06, 2020 at 12:32 PM

Thanks again John. I thought that if I use the Isolated version of the Orion, I would not need the Cyrix combiner, as the Orion would simply stop charging once the engine is switched off. Am I wrong in this assumption? Can the Starter battery be drained by the Orion once the engine is switched off?

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JohnC ♦ adric commented · Apr 06, 2020 at 01:06 PM

You're quite right if it's ignition prompted. And it really must be in that application.

My Cyrix comment for you to ponder using both engines to feed the batt supplying the Orion. Haven't done it myself.. just for pondering.. :)

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