House Battery

[kennneee]

Which Wallas heater do you have?

[Dan Boccia]

Good discussion!
The best reference by far for all of this is Nigel Calder's book. His thesis on batteries, chargers, etc. is the gold standard.
It sounds like some good decisions are being made.

One thing that is often misunderstood is how different batteries recharge - with lithium, you can charge them at VERY high amperage all the way up to about 85%. With Firefly and other AGM, you have to be more careful. This gives lithium one of its biggest advantages compared to AGM. You also should size your charger and wiring from outboard to the battery to allow the maximum amperage charge your battery will allow. This is key when you're cruising and want to stay somewhere for a couple days - you can motor around for an hour and get a LOT of charge if you have a robust charging system and your battery can handle it - otherwise you have to putt around for a few hours to get enough charge or run a generator, which is humbug for our smaller boats. With lithium batteries, I'm not convinced a fancy battery charger like the Sterling Bat-Bat charger is required - look at the charging curve for your lithium battery and you may find you don't need that extra complexity. Also, the Sterling units are NOT explosion-proof so you should NOT install them in the bilge or anywhere else where fuel vapors may collect.

My pot puller and big anchor winch have not been a big issue on house battery because I run the engine while I'm pulling. The one problem with this is that I bought the 30A Sterling Bat to Bat charger, and I wish I had the 60A so I could get full alternator amperage to the winch/puller. That's an oversight I hope you all avoid! Rather than upgrade to the 60A charger, I'm going to investigate lithium batteries. Half the weight and more Amp-hours than my AGM, plus maybe no need for the charger - that's a win!

Solar is super helpful - I have 200 watts of solar feeding my house battery so in the long days of summer that adds up.

Regarding useful range of battery drawdown, few of us are going on year-long cruises where battery life is paramount. How many days will you ACTUALLY use the boat, and how many battery cycles does that really represent? Being realistic about this, I'm happy discharging my Full River AGM battery to 30%, giving me an easy 55% useful range. When I get home I put it on a smart charger and get it to 100% for the next trip. The battery will still last years with my intermittent use.

[Todd j]

Dan, do you know the title to the book your reference or which issue?   At a glance it looks like there may be more than mechanical and electrical book. Tia

[tom e]

Todd j --

He's most likely referring to Boatowner's Mechanical anad Electrical Manual  by Nigel Calder.  Probably his latest, the forth edition.  $45 +/-

te

[Todd j]

Groovy, thanks Tom

[Rbob]

It will take a lot of homework for me to decide on which Lifepo4, some you can combine, some you cannot. Some even have emergency start button if your battery gets to low.

Most have battery management system on board and will drop out if overcharge, low voltage, direct short, etc.  A alternator protection device is probably a must add if you do not want to blow up your alternator or maybe there is a way to wire it so no load dump happens to the alternator.

Just looked at my "Boatowner's Mechanical and Electrical Manual (Nigel Calder), its the second edition and no info on Lifepo4...

[Dan Boccia]

Yes, that's the book I'm talking about, referenced above.
Another excellent reference is Jeff Cote's videos on Youtube - look up Pacific Yacht Systems and do a search for batteries, etc.

I agree it's important to research the various battery management systems (BMS) included with many lithium batteries, and how they may interact with the relatively low-tech voltage regulator on the outboard, and whether or not you need some sort of charge control.

With good quality AGM batteries, the science is pretty well established on how to hook them up properly. With lithium, it's still the wild west and you're on your own to some extent, unfortunately. That said, I'm sure a rep from one of the good lithium battery companies would be happy to help you set up a good system, and in the end the advantages are well worth it I think. Good luck!

[Todd j]

Dakota batteries has some interesting kits for sale.  They also have a 200 AH battery that is a 1 piece unit.  The kits they offer come with all kinds of goodies up to including solar panels.  Looks like all their batteries come with a charger too. 11 year warrantee
 

[Dan Boccia]

These Dakota battery kits look interesting, AND point out **exactly** what I warned about regarding charging!!

They state the batteries can take up to 50 amps of charging current. However, they're only supplied with a DC to DC charger that is capable of 19A of charging current. I would buy separate components and upgrade to a charger that is capable of the maximum amperage the battery can accept. This will reduce your charging time by 2.5X, which can make a huge impact when you're out cruising around/camping, etc.

I would also read the battery manufacturer's owner's guide, which usually has a blurb about optimal charging voltage and current. Compare companies to get the battery that can charge the fastest.

[Todd j]

thanks for the heads up.  Im not quite there yet, but im still at the point in my build where im not trying to save money, yet...  I dont even know where the batteries are going to go yet.  I have had terrible luck with all things battery for some time now.  For me the no hassle after install for the LI batteries sounds like a win.

[Rbob]

One suggestion / concern I have is the "alternator output"  Even though in my case it is 85amps.  I would not want my alternator being worked to "death".

Alternators are rated at their max output which is at 6,000 rpm's. I could be off on that but I was checking into it a couple days ago.

I will probably go with the 30amp b2b setup, although the 60amp b2b would probably work fine.  Lots of question for the suppliers to answer.

Troublesome for me is Sterlings B2B charger says to install in cool, dry and well ventilated space.

REDARC (Australian made) makes one, that is waterproof and heatproof and does not have a fan like Sterling's.

Found info on REDARC at Lifeline Batteries:
https://lifelinebatteries.com/2021/01/redarc-dc-dc-in-vehicle-battery-chargers-recommended-to-charge-lifepo4-rv-house-batteries/   

[Dan Boccia]

That REDARD Bat to Bat charger looks really good, thanks!

However, please read the installation manual!! At the bottom of page 3 it recommends against a Lithium charging profile in spaces that will have poor ventilation...ie engine room...bummer. BUT, since this unit is sealed, I'd have no problem putting it under the gunnel just aft of the cabin, right above my battery box, with the wire splices inside a cabinet just adjacent to the mounting position.....

Plus I love that you have a solar charge controller built-in, so one of your solar panels could hook right into this.
Pricey, but looks convenient.

[Rbob]

You can tell I have glasses and do not always spell check what I wrote !

REDARC....

[kennneee]

Check out the Victron components. They make some high quality stuff. If you have mixed chemistries like an AGM start and a Lithium house it is wise to isolate them as they have slightly different resting voltages. It doesn’t harm them but one will always want to discharge into the other to equalize voltages. I was using a Blueseas Add a Battery plus when my system was pure AGM and BlueSeas advised against using it in my new application. I still use the charger to top off my start battery at the dock. The Victron dc-dc charger allows the house battery to be charged indirectly from the start battery once the start is fully charged always giving priority to the start battery. The Victron has several pre set charging curves and it also allows for custom settings. My solar panel will be hooked to a Victorn Smart Solar controller which will charge the Lithium house battery. I left the old battery switch in place which allows for paralleling the batteries if I need the house battery to start the motor. Hope that makes sense. Ken

[Rbob]

After more research on the b2b charger I have went with the Renogy, it is a very simple install and have more capacity for Solar charge, maybe later I will add solar.


Check it out:

https://www.youtube.com/watch?v=PeATWMksWLA