Stuck at first-time 2000W solar setup on boat

horstenegger said:

Is there really a difference in viewpoint on boats vs non-boat? Power is power, right? Except for the fact that boats use more DC power than RVs (or homes for that matter), but I don't see that fact being linked to this equation.

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Yes, that's it. There are a few 12VDC loads on a sailboat that are bigger than what you will likely see anywhere else. The bow thruster on the boat I was helping to upgrade draws just under 500A. I'm not sure why everything has stayed at 12V for all these years, but it seems like that is what people stick with.

horstenegger said:

the windlass is on the front of the boat, and the batteries in the stern

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So what does it run off now? A separate battery at the bow?

horstenegger said:

Most catamaran owners don't actually run both engines together if it's not really necessary.

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All the ones I know do :·)
It never occurred to me to run only one engine (I've captained a few), but I guess it makes sense.
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horstenegger said:

Wow, this is quite the plot twist! I have literally never heard of this concept. Thanks for the clarification @Rocketman and thanks for the further dissection @Horsefly.

2 things that come to mind directly when I'm reading this:

1. Is there really a difference in viewpoint on boats vs non-boat? Power is power, right? Except for the fact that boats use more DC power than RVs (or homes for that matter), but I don't see that fact being linked to this equation.
2. I don't have the REC BMS. I have the Overkill aka JBD BMS. How much does the suggestion / option of going the supercell route apply to my setup?

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using supercells does not matter to the bms - it just sees a cell. So it you made a 2p supercell - that’s just like buying a 200ah cell instead of a 100ah cell. It’s one way to cut down on the bms costs.

You can make supercells with an Overkill battery. I wanted a 50ah portable 12v battery the cells that fit the box I wanted to use were 25ah fortune cells. I got eight of them put two cells into a supercell (super mini cell?) then 4 in series so 2p4s - attached the Overkill 12v bms and finished it. It works great!

The items you lose with supercells is the bms still balances with the same voltage- so it can take 2x as long. Also you are monitoring the average of the two cells - but they should be exactly the same. If one cell dies it can pull down the partner’s voltage- so the bms will notice there is a problem- but you will not know which cell until you test it.

Don B. Cilly said:

So what does it run off now? A separate battery at the bow?

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I'd have to check, but I believe it's now setup to be connected to the LFP bank. Either that or to the starter battery. Definitely no separate battery though (there is none).

Rocketman said:

using supercells does not matter to the bms - it just sees a cell. So it you made a 2p supercell - that’s just like buying a 200ah cell instead of a 100ah cell. It’s one way to cut down on the bms costs.

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Makes sense indeed, although if I understand correctly, this will eliminate the option of monitoring every individual cell, right? How much of a disadvantage should that be considered?

Rocketman said:

You can make supercells with an Overkill battery. I wanted a 50ah portable 12v battery the cells that fit the box I wanted to use were 25ah fortune cells. I got eight of them put two cells into a supercell (super mini cell?) then 4 in series so 2p4s - attached the Overkill 12v bms and finished it. It works great!

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Just to clarify - I don't have Overkill batteries, I have Fortune cells. Only the BMS is JBD (aka Overkill).

Rocketman said:

The items you lose with supercells is the bms still balances with the same voltage- so it can take 2x as long. Also you are monitoring the average of the two cells - but they should be exactly the same. If one cell dies it can pull down the partner’s voltage- so the bms will notice there is a problem- but you will not know which cell until you test it.

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Right, this answers / confirms my first question. I'll have to think about what route I'll be taking. Tradeoff vs Tradeoff ¯\_(ツ)_/¯


Meanwhile I can confirm that my (stock?) Mitsubishi alternators are indeed 115A each. Am I right to assume that those should be big / powerful enough to charge the LFP bank without adding too many complex safety measures? Currently, the engines have two alternators attached to them. One for the starter battery and one for the previous AGM service batteries. I'm considering ditching the one and just the keep the 115A ones, connect those to the starter batteries and then connect those to the MultiPlus. What do you think?

horstenegger said:

Just to clarify - I don't have Overkill batteries, I have Fortune cells. Only the BMS is JBD (aka Overkill).

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I think what @Rocketman is referring to is a battery monitored by an Overkill BMS.

horstenegger said:

Meanwhile I can confirm that my (stock?) Mitsubishi alternators are indeed 115A each. Am I right to assume that those should be big / powerful enough to charge the LFP bank without adding too many complex safety measures? Currently, the engines have two alternators attached to them. One for the starter battery and one for the previous AGM service batteries. I'm considering ditching the one and just the keep the 115A ones, connect those to the starter batteries and then connect those to the MultiPlus. What do you think?

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I'm pretty confused by this. You are talking about charging the LFP bank from the alternator, but you are talking about hooking the alternators to the starter battery. So is the alternator going to charge the starter battery, or the house battery? Also, you don't want your starter batteries connected to the Multiplus, unless you are doing something completely different than I can picture.

As for "complex safety measures" the main thing you need to be aware of is that directly charging LFP from an alternator presents some serious risks:

1. If the BMS does an over-voltage disconnect while the alternator is charging, the alternator will suddenly have no load, which can cause it to burn out in a matter of seconds.
2. A stock alternator may have a good voltage for AGMs, but not so much for LFP. What harm this may cause depends on how much different it is from what the LFP needs.

The answer to these problems is a good regulator attached to your alternator. There are several out there. My limited experience is with a Balmar regulator, and the Wakespeed WS500 regulator. As far as I know the Balmar doesn't speak LFP (and it is a real pain to program), but the Wakespeed WS500 is pretty awesome. It can manage a charge profile for your batteries, just like your SCCs and your Multiplus.

My idea was that the alternators charge the starter batteries, and when those are full, the charge continues to the house bank, which would also make the starter batteries work as a buffer to soften the sudden BMS cut-off.

As an alternative, instead of buying 2 Wakespeeds, I would probably go for the well respected Nordkyn VRC-200, because on its product page, it says:

"For the owners of Volvo Penta D-Series engines, it is a highly effective plug-in upgrade for improving the charging characteristics of the excellent stock 14V/115A Mitsubishi A003TR0091ZT and A003TR0093ZT alternators."

The one in bold is the exact model we have...

horstenegger said:

My idea was that the alternators charge the starter batteries, and when those are full, the charge continues to the house bank, which would also make the starter batteries work as a buffer to soften the sudden BMS cut-off.

As an alternative, instead of buying 2 Wakespeeds, I would probably go for the well respected Nordkyn VRC-200, because on its product page, it says:

"For the owners of Volvo Penta D-Series engines, it is a highly effective plug-in upgrade for improving the charging characteristics of the excellent stock 14V/115A Mitsubishi A003TR0091ZT and A003TR0093ZT alternators."

The one in bold is the exact model we have...

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If you want to charge the LFP from AGM start batteries, add a good Victron DC-to-DC charger to your list, rather than just hooking the two together.

I don't know anything about the VRC-200, but skimming the product page they have a bolded statement that it is not a replacement for the regulator, but rather works with the existing regulator from Balmar or Mastervolt or whatever. I don't know exactly what that means, but you should make sure before you commit. Maybe someone here has used the VRC-200 with LFP.

Horsefly said:

If you want to charge the LFP from AGM start batteries, add a good Victron DC-to-DC charger to your list, rather than just hooking the two together.

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Yes I forgot to mention that rather important little detail, lol.

Horsefly said:

I don't know anything about the VRC-200, but skimming the product page they have a bolded statement that it is not a replacement for the regulator, but rather works with the existing regulator from Balmar or Mastervolt or whatever. I don't know exactly what that means, but you should make sure before you commit. Maybe someone here has used the VRC-200 with LFP.

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Yeah it's a bit vague, but I'm reading nothing but good feedback from users on it. From what I understand, it's initially designed for alternators with built-in regulators, which our alternators do have (although they only regulate down to 14V). Anyway, will contact them for further clarification. Thanks!

If you are only hooking the alternator to your AGM start battery, you may not need the addition of the VRC-200, as the existing regulator may already be fine for AGM. I was mentioning the Wakespeed because I figured you would want to use the 100+ Amps available to charge your house battery.

I don't know what I want because I don't know what I'm talking about ?

But the way I see it. My 2 most viable / practical options are:

1. Only keep the 115A alternators and remove the other ones, then hook those up to the charger batteries -> DC-DC converter -> MultiPlus
2. Keep both alternators, one connected to the starter batteries and one (the 115A ones) connected to the VRC-200s -> MultiPlus

Makes sense?

horstenegger said:

I don't know what I want because I don't know what I'm talking about ?

But the way I see it. My 2 most viable / practical options are:

1. Only keep the 115A alternators and remove the other ones, then hook those up to the charger batteries -> DC-DC converter -> MultiPlus
2. Keep both alternators, one connected to the starter batteries and one (the 115A ones) connected to the VRC-200s -> MultiPlus

Makes sense?

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I would never intentionally remove a well-working alternator if I were you. Option 2 sounds much better to me.

You may want a DC-to-DC charger between the two banks anyway, as a backup way to make sure both banks are getting charged. I.e., if the starter battery is only getting charged from one of the alternators, you may want a DC-to-DC charger from the house battery to the starter as backup. Since your house battery will be able to charge from multiple sources (shore, solar, alternator), it is less likely to lose all its charging sources.

Horsefly said:

I would never intentionally remove a well-working alternator if I were you. Option 2 sounds much better to me.

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Cool, thanks. I was thinking it may be possible that 2 alternators on one engine puts unnecessary extra strain / resistance on the engine. But if it doesn't, all good.

Horsefly said:

You may want a DC-to-DC charger between the two banks anyway, as a backup way to make sure both banks are getting charged. I.e., if the starter battery is only getting charged from one of the alternators, you may want a DC-to-DC charger from the house battery to the starter as backup. Since your house battery will be able to charge from multiple sources (shore, solar, alternator), it is less likely to lose all its charging sources.

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Right, makes sense. Shore power will be virtually non-existent to us (we aim to anchor 99% of the time), so having at least one back-up method is definitely a good idea.

Earlier, you said a good Victron DC-to-DC converter. What is 'good'?

horstenegger said:

Cool, thanks. I was thinking it may be possible that 2 alternators on one engine puts unnecessary extra strain / resistance on the engine. But if it doesn't, all good.

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I thought you were talking about an alternator on each engine. I guess I don't know what using two alternators on one engine may do, good or bad. So maybe I'm wrong.

horstenegger said:

Earlier, you said a good Victron DC-to-DC converter. What is 'good'?

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What I really meant is a Victron Orion is "good" and there are a number of others that are not so good. It's pretty easy to find a DC-to-DC charger that is "dumb" and not programmable, so you are stuck with whatever the voltage settings it got at the factory. I don't know what all models Victron has, but I know the smart Orion DC-to-DC lets you set the voltages for whatever is right for your batteries. I think they also have a connection for a switch or relay to disable it if for some other reason you don't want to further run down the source battery (house). I'm pretty sure the DC-to-DC doesn't integrate with the Cerbo GX (doesn't provide any data to it), but that is probably OK.

Ah, yes, no, I was indeed talking about 2 alternators per engine. I just did some digging and it indeed doesn't seem to be a problem!

If I go down the DC-DC route I will indeed definitely go with Orions. For now I'll just stick to solar charging (should be fine with the sunny seasons coming up and having 2000W of solar) and add alternator charging as a backup method in a couple of months. It will probably take a while until I receive the VRC-200s anyway as the business owner builds them himself and is in New Zeeland (we're in Europe). In fact, he's currently our sailing, so the lead time will definitely be a couple of months.

Thank you so much for all these insights Horsefly. Orders have been submitted, so as soon as I receive everything I'll start building and report back.

That being said - if anyone has anything else useful to add, please feel more than welcome to do so ?

horstenegger said:

Yes I forgot to mention that rather important little detail, lol.


Yeah it's a bit vague, but I'm reading nothing but good feedback from users on it. From what I understand, it's initially designed for alternators with built-in regulators, which our alternators do have (although they only regulate down to 14V). Anyway, will contact them for further clarification. Thanks!

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Little intermittent update: got word back from the VRC-200's manufacturer:
"You are correct in your interpretation. You can plug a VRC-200 into your Mitsubishi alternator(s), but not into one that was previously fitted with an external field controller because those have no regulator any more."

So, good news for those with anyone who is looking to charge their LFP bank with 115A A003TR0091ZT alternators: it's plug&play!