Trojan Boat Forum

Correct. The VR will keep the alternator in check, and the DC/DC charger will act as a check on alternator over charging the LFP house bank by reducing excess amps off the engine bank, while underway, to no more that 30. BMS (Battery Management System) in the LFPs will also regulate charging to prohibit over voltage and amps. Thanks for the observations. Now I just gotta wait out the usual snow and ice up here. There’s always skiing to look forward to.

Thanks, the reason I asked is that I was told you can't charge two batteries off one alternator, because if only one battery is discharged and one full the alternator/voltage regulator is charging both and you need a split charging system. I thought there might be a similarity when the system was drawing power off the common alternator line with the engine battery bank. Keep us advised how you make out, I have thought about charging my inverter bank from the engine.

We have the same wait for spring on here on Grand Island.

Happy Thanksgiving,
Rich

Many of my components (solar controller, DC/DC charger, battery monitor, etc) are from Victron Energy and are”smart” in that they can be controlled with an android or iOS Bluetooth enabled device (phone, tablet or even laptop). They can be configured to turn on and turn off, based on preset algorithms or parameters that you can enter from your device. My setup still uses a 1-2-All-Off switch and I’ll use “1” when the engine is running so the alternator will be charging the “1” or engine battery (12V/100AH deep cycle FLA battery). The DC/DC charger is hooked up so that the input of the charger comes off the positive of the engine battery an the output of the charger goes to the positive bus bar of the new lithium (2 Battle Born LFP 100 AHs wired in parallel for 200AH or 160AH useable before the BMS cuts off any more drain).

My alternator only puts out 70A at 3000 rpm and less at comfortable cruising speeds around 1800 RPM, so I’m not counting on that single alternator to do much more than keep the engine battery charged up. The solar panels top out at around 300W in full sun and supply up to around 18A out of the solar controller. This is enough to keep the LFP bank charged up during the day when I’m not using shore power (which is also dedicated to the LFP house bank). My max amp hog is the Norcold AC/DC fridge at 4A and can use up 35-40AHs at night (I’m being very liberal here). But, again, this demand is coming out of the house bank, which will be replenished on a sunny day at 18A, which means it will take 2-3 hours of sun to bring the house bank up to at least 80% SOC.

I am hoping to continue to use my ACR to keep both battery banks in balance and not drain either one into the other. I’ll use “1” on the switch only underway and then go to “2” on the hook or away from my dock and shore power.

I’m probably being a little more paranoid and overly cautious with the LFP batteries, but I want these to last at least 10 years.

paskyhawk wrote: ↑Mon Nov 23, 2020 12:33 pm Thanks, the reason I asked is that I was told you can't charge two batteries off one alternator, because if only one battery is discharged and one full the alternator/voltage regulator is charging both and you need a split charging system.

You can do this using an ACR: https://www.bluesea.com/support/article ... _Explained

I just got an email from Blue Sea telling me their ACRs are not suitable for LiFePO4 batteries because the set points for combine/isolate are not adjustable. I have an older model Blue Sea ACR, the 7600, which does allow me to set these voltages. BUT the 7600 is 12 years old, and although it may last longer than me, I’m thinking about adding a Victron combiner that’s specifically designed to go between FLA, SLA, AGM starter batteries and Lithium house banks. I will hook this up to the com port on the back of the Victron BMV712 battery monitor, which allows me to monitor both banks (Volts, Amps, AH, temp SOC etc) and set the combine/isolate points - all via my iPhone and iPad, or any Bluetooth enabled device. Verrrrrrry slick, IMO.

Blue Sea didn’t give me any warm and fuzzies about the 7600, as they never ran it with a Lithium bank. Probably would be fine, but for $70 for the Victron combiner I think I’ll go that route..

I’m not plugging any of these products, just sharing what I’m using for my boat and system. I Ike using proven, tested reliable products like Ancor, Blue Sea, Victron, Battle Born, etc.

Hi Boppy ,

yes I am in Croatia / Split to be precise
Sorry for late reply , but being very busy and not looking here every day
Are you planning to visit my pace again sometimes ?

Look like we gone have very similar setup ( except batteries )
Well you want to be independent all day at sea , and I like to be totally independent of electric energy
Actually I don't hook shore socket at all, even at my marina in front of my boat

I install 800W 2X400 panels , may house battery are full in the morning till I drink coffee
Now someone will say not necessary , but very soon I am installing water maker ( 30l /h )
This one I will run every day for two hours ( 60l water )
And summertime extra portable freezer is also running

That way I can be on water for week and more
Actually limiting factor will be how much beer I have before I go for shore

Happy thanksgiving

Happy Thanksgiving, Goran. You live and boat in a beautiful part of the world!

OK, I’m back again, with yet another thought about my wonderful lithium battery bank and its ability (or not)to act as a back up to start the engine. I’ll have a new 100AH 850CCA lead acid battery for the engine, but was thinking my lithium bank would not have enough surge to do the same thing, in the event the engine battery goes dead. I’ve been looking over the original owner info that came with the boat including wiring schematics but don’t have any information on what amperage is needed to crank up the starter. I’m dealing with a single 1977 Chrysler Marine 318. Anybody out there to help cool my fevered brain? Many thanks in advance!

Well, I think a portable jump pack (they’re all lithium) would be perfect for an emergency start situation. No issue starting a small V8 or even a big block for that matter (depending on the model). Check out the Noco GB70 as an example. I have the 40a model for my cars.