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dano71 avatar image

How to add a lithium battery to a Boat setup

Hello, I am having some challenges trying to incorporate a LiFePO4 house battery into my boat. I would like to know will I kill my alternator/rectifier or cause other problems ie for MPPT solar controller or LiFePO4 with the setup in the attached diagram?
please not that I do not want to change out anything in that diagram now only add items where necessary

Many thanks for your expertise and suggestions

e315c5a5-022a-4ac9-b420-e38380fbfbcd.jpeg

thanks Dan

Lithium Batterybattery chargingmppt smart solaralternator
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Should I ditch the 4way manual switch in favour of an Orion-Tr Smart DC-DC charger isolated?

I will use also an Orion Smart 12/12 19A Charger for my van Lithium battery. I have done alot of research and this is the safest for the old DC system and the alternator.

Thanks, mine is in and working

3 Answers
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randy-putnam answered ·

74c09ce9-165b-47bc-acb3-8fbd5b5b594e.jpeg

I’m in the process of adding LFP to replace my lead acid house bank, as shown in my diagram. I, too, have the 4 way battery switch and may add the charging sources (Alternator, MPPT, and IP67)to the common of the switch. I am using the Orion Smart 12-12/30A DC-DC charger to act as a buffer between the 70A alternator and the LFP battery bank, connecting the “in” of the Orion to the positive of the lead acid engine battery and the “out” to the LFP bank. I think your plan is fine. BTW I contacted Blue Sea about connecting the charging sources to the switch and they said fine. I am adding the 712 battery monitor as I like having more data than my mind can handle!


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So I have found that if the solar is switched on the voltage is high enough to put the Orion and Chargers into standby, I have ditched the idea of the 1,2,both switch and have the Orion engine detect on its own manual switch so its either on shore power, alternator or solar with two manual switch (plus pulling the 240vAC plug) not looking at ignition relays at the moment, I would need two or three anyway and still want the manual switch to just charge the starter and avoid voltage spikes

Today I also found that the old 80Ah starter battery, which may be on its last legs, pulled the orion into switch-off mode, this was on quite a long run, I will change it out for a newish 60Ah and hopefully that will resolve that issue otherwise I will have trouble charging the house LiFePO4 at night off the alternator if I need to, I would have to run the engine for half an hour just to get the starter battery up to voltage first

dano71 avatar image
dano71 answered ·


this is the setup now

67588a56-80a7-49dc-9ecb-a71a15c4208b.jpeg


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dano71 answered ·

No comments or advice?

oh well I started to wire this up, one observation is the LiFePO4 charger doesnt charge with the solar on, due to the voltage I expect (even in low light)

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Try hooking up the PV panels in series. Parallel panels are probably not reaching the voltage necessary: battery voltage +5 to start, battery voltage +1-2 to keep changing.

Using a switch to combine batteries of different types isn't the best of ideas. Even a LFP that's sold as a drop-in will have different characteristics. The DC-DC charger is a much better approach than a switch but it's one way: either charge house battery from alternator or charge starter battery from solar.

The solar works fine, its just there is no sun