Electricity seems to rule an ever bigger chunk of my life. Ever since installing the solar panels and house battery at home ( as well as the EV) I am monitoring and tweaking ever more.
I woke this morning to read of my good friend Mandy of NB Don't Panic and her questions to the 12v boating group ( a decent helpful group in the main) around a move to lithium on her boat.
The boaters reading this will be aware of the benefits of Lithium, it is running our cottage at the moment and has been doing so for getting on three years now. It also now propels us across the country in our EV... so why not on our boat?
Space.... Tony built a cruising boat not a liveaboard. The engine battery bank space is well constructed but limiting. Not a problem if you cruise each day as the limited lead acids we got with the boat would get a charge each day to replenish them. I replaced them with initially sealed lead acids for ease of maintenance they last about 5 years which is the 'norm' then AGM's which were bigger in amp hours capacity but had the same 50% use restriction and the same level of slow sulphating and therefore the same expiry time.
Lithium clad boaters know lithium can go to a much lower state of charge and charge much faster. The evangelists and more techy will put in hybrid systems with carefully set BMS parameters and sometimes longer charging leads to control the charge. The hybrid being the partner 'spare' AGM or lead acid that is there to protect the alternator when the lithium's shut off their charge receiving when full... like turning off a switch and the alternator needs to have somewhere to momentarily direct its charge to otherwise it'll kill the regulator/rectifier - my understanding please comment if I have anything here wrong?
Therein has alway been my problem of a hybrid set up - space. A decent sized lithium does not conform to the standard AGM battery sizes so I could not fit in a starter lithium and the hybrid support battery. I did consider using the starter as the hybrid battery but the general consensus was that was not the best idea - I need to understand that more ?
I have of course and still do consider adding in a a larger portable solar battery that I have mentioned in other posts - I use the Ecoflow but like the Aferiey. However £ for £ a 'separates' install is cheaper* especially as I already have the charger and the solar controller so would only need the lithium battery but what I would also need and do not have is space.
So the other option and why Mandy's post was of interest is she is having what I think is referred to as a direct system... no extra hybrid support battery but a DC-DC charge controller. This basically takes the charge the alternator is giving to the starter battery and the dc-dc controller links the starter to the lithium so when the engine is running the starter is getting the charge and the charge controller is charging the lithium.... the charge controller can be adjusted to not overload the alternator - Mandy's got the same size alternator as I have - 70 amps
It would also get rid of a lot of Smart bank Smart gauge wiring as the battery has its own Bluetooth ( and heating) for information on charigng and state of charge etc.
There is a lot to like about the approach Mandy is taking and I will watch with interest her experience which I have no doubt will be a good one.
Right off to deep dive into DC-DC chargers and Lithium batteries I may be a while !
*Plus the separates gives a bugger capacity at lower costs but removes the duel use of the solar battery where we can bring it home and use it in the cottage. My Ecoflows when not on the boat run the pond pump and filters 75 w an hour x 15 = 1125 W/hr's which gives the main hour batteries that much more capacity - as an example of the duel use



































