Solar Controller for Firefly

[Panope]

Please recommend a small MPPT controller that would be appropriate for charging the following house system:

-Bank will be a single (one) Firefly group 31 battery.
-Solar panel(s) up to 200W.

Also, assuming Firefly batteries require carefully selected charge voltages/profiles, how does one regulate the charging from a standard Yanmar (Hitachi) alternator?

Thanks,

Steve

[RickG]

I use the Victron Smartsolar 100/30 chargers with my Fireflys. With the new software they work nicely. The Bluetooth interface gives you amps and volts for the solar panel and the battery.

Cheers, RickG

[rslifkin]

For the alternator, there are 2 choices: either let it put out constant voltage at just a little above float (to avoid cooking the batteries if motoring for a while after they're full), but that provides slower than optimal charging. Or use a fancier regulator that can deliver a better charge profile.

[a64pilot]

As near as I can tell. There is no significant difference in charging a Firefly than any other AGM battery, for example you charge a Lifeline at 14.3V +or- .1V, a Firefly at 14.4V. You float a Lifeline at 13.3V +or -.1V, Firefly now recommends 13.5V.

The magic if it exists, is in their resistance to sulphation. It didn’t seem that they require anything special charge wise, if anything due to them not being required to be 100% charged each cycle, they require much less care.

With one battery being a bank, I wouldn’t spend the money to install an external regulator and new alternator, and any solar controller ought to be fine, ideal for any lead acid battery is to terminate charging at a trailing charge current and not a timer, but again is it worth it to spend the bucks for a single battery?

[noelex 77]

A fully adjustable solar controller is always a good idea. This can be matched to all available and future battery chemistries.

The Victron range of Smart solar controllers are a good choice.

The standard Yanmar 80A alternator is not a great product. It tends to cut back production due to temperature issues.

The standard alternator regulator is not adjustable, but it is likely in most situations to not deliver enough charging capacity to overcharge the batteries. It can be upgraded with an external regulator that eliminates any possibility of overcharging, but the overall charging rate remains disappointing due to inherent limitations of the alternator, despite its healthy rating. It is also not an easy conversion for this alternator.

Many sell the standard alternator, or keep it as a spare and upgrade to a better model, preferably also installing an external regulator. If well done, this can produce much higher charge rates without any danger of overcharging. This is more expensive, but the DIY alternative of a large frame bus alternator and arranging your own belt system can be quite inexpensive while producing substantial improvements.

This sometimes requires some engineering and DIY skills, but having seen your great results and clever solutions for upgrading your yacht, this would be very easy for someone with your skills.

[Panope]

Originally Posted by RickG

I use the Victron Smartsolar 100/30 chargers with my Fireflys. With the new software they work nicely. The Bluetooth interface gives you amps and volts for the solar panel and the battery.

Cheers, RickG

Thanks Rick,

That look perfect. Price is reasonable also.

[Panope]

Originally Posted by rslifkin

For the alternator, there are 2 choices: either let it put out constant voltage at just a little above float (to avoid cooking the batteries if motoring for a while after they're full), but that provides slower than optimal charging. Or use a fancier regulator that can deliver a better charge profile.

I suppose one other option is to simply disconnect (via a manual battery combine switch) the house bank from the start battery (alternator is wired to the start batt) during the rare lengthy motor passage. Not sure how to remember to do so, however.....

[Panope]

Originally Posted by a64pilot

As near as I can tell. There is no significant difference in charging a Firefly than any other AGM battery, for example you charge a Lifeline at 14.3V +or- .1V, a Firefly at 14.4V. You float a Lifeline at 13.3V +or -.1V, Firefly now recommends 13.5V.

The magic if it exists, is in their resistance to sulphation. It didn’t seem that they require anything special charge wise, if anything due to them not being required to be 100% charged each cycle, they require much less care.

With one battery being a bank, I wouldn’t spend the money to install an external regulator and new alternator, and any solar controller ought to be fine, ideal for any lead acid battery is to terminate charging at a trailing charge current and not a timer, but again is it worth it to spend the bucks for a single battery?

A very good point. Thanks.

[Panope]

Originally Posted by noelex 77

A fully adjustable solar controller is always a good idea. This can be matched to all available and future battery chemistries.

The Victron range of Smart solar controllers are a good choice.

The standard Yanmar 80A alternator is not a great product. It tends to cut back production due to temperature issues.

The standard alternator regulator is not adjustable, but it is likely in most situations to not deliver enough charging capacity to overcharge the batteries. It can be upgraded with an external regulator that eliminates any possibility of overcharging, but the overall charging rate remains disappointing due to inherent limitations of the alternator, despite its healthy rating. It is also not an easy conversion for this alternator.

Many sell the standard alternator, or keep it as a spare and upgrade to a better model, preferably also installing an external regulator. If well done, this can produce much higher charge rates without any danger of overcharging. This is more expensive, but the DIY alternative of a large frame bus alternator and arranging your own belt system can be quite inexpensive while producing substantial improvements.

This sometimes requires some engineering and DIY skills, but having seen your great results and clever solutions for upgrading your yacht, this would be very easy for someone with your skills.

The thing is, my power needs are so low, and I motor frequently enough, that even the rather "dumb" stock alternator produces plenty of power.

In the 8 years I have been gunking around (not liveaboard) with my current power system, I have not once ran the engine just to make electricity.

[a64pilot]

The real advantage of an external voltage regulator and a high dollar alternator is to charge a BIG bank in a relatively short time, a standard alternator isn’t a very good charge source, yes they will eventually get a battery there, but the larger the bank the less likely they will, and being fully charged is good for the lifespan of a regular battery.
However to do the full Monty, alt, reg, and serpentine belt kit is roughly $2,000.

The real advantage of a Firefly is it is OK with PSOC, so getting to absolutely full shouldn’t be as important and I’d therefore assume an expensive alternator kit is less important.

The advantage of a Yanmar stock “dumb” alternator is they don’t require special belt kits and because they cut back as soon as they get hot, they last a really long time.

My belief is most people would be better off putting the BIG alternator money into more Solar, and do the alternator kit if they motor frequently and or the Solar still isn’t enough.
I believe a $1,000 Honda is better than a BIG alternator, and I have a 165 amp Mark Grasser and a Balmar 614, so I’m not anti Alternator and understand them
It really depends on how often you motor I guess.

But a single G31 battery as a bank, I don’t think it’s going to need much charging power, if you can get by overnight off of one battery, you aren’t using much power.

[kmacdonald]

The Victron SmartSolar 75/15 would work fine. The acceptance rate of a single group 31 battery will limit the output of the alternator enough to not worry about burning it up. There is no way to regulate the charging time of the stock alternator but the battery acceptance will be all that's really needed. Cars and trucks don't use three stage regulators and batteries seem to last just fine. I doubt you do much motoring anyway.

[Pegu Club]

We are using two Renergy 100 watt panels with two group 31 fireflys, with Genasun MPPT controllers one for each panel, they have been in constant use for over two years and have worked as advertised as it were. If it makes any difference for your circumstances, we are full time cruisers, and we do rely on them daily. We as well charge while motoring using a 70 amp alternator on our Beta diesel.

Fair winds,

[jhulmer]

This is what I installed and I have only tested it a few times now but I really like the way it works. Turns your alternator into a smart charger you can set for Fireflys. I have 4 each group 31s.
https://www.sterling-power-usa.com/



Cheers Jim

[parado]

Kmac was right. You size the victron by the solar panel size, not battery bank size. I have 3 fireflys and a 160 watt panel and have that charge controller with the dongle, and can see all parameters on my phone, really nice to have