Moving from SLA to Lithium (LFP04) Question re Isolator

[TonyM]

I am changing my House battery set up to Lithium and would appreciate advice. I have a Bavaria 37 Cruiser (2006) which is well stocked with electrical gadgets and comforts (it’s a caravan really)..

Current Set-Up:
   115amp alternator (not smart)
   Sure Power 1202 Isolator
   SLA Engine battery (100ah - 600CCA)
   SLA House Battery (100ah)
Proposed Set-up:
   Alternator and Isolator remain configured as is today
   House Battery replaced with a 200ah Lithium
   40 amp DCtoDC charger
   30 amp ACtoDC charger with Lithium profile

So no, it is not so simple. I understand that I must protect the alternator from overheating by charging the lithium battery through a DCtoDC charger and that I must use a new AC charger with a lithium profile. Both of these units, together with the lithium battery I have purchased and established in a test bed in my shed.

Issues:
   1. Can I leave the Isolator (SP1202) in place as currently configured?
      ○ If I do this I would install the DCtoDC Charger next to the Lithium battery which would then be charged through the DCtoDC charger.
      ○ The DCtoDC charger would also be connected to the SLA Engine battery.
      ○ The DCtoDC charger also has a solar panel feed which I understand will feed into both the engine and house batteries as required.
      ○ The DCtoDC charger has temperature and an ignition sensors which I will connect appropriately.
      ○ I will disconnect the 'Quick' AC charger from the House Battery and install the Lithium profile AC charger alongside the 'Quick'.


    2. My other concern is that the DCtoDC charger will be close to both the House                
and Engine Batteries and downstream of all load and charging. That is the way they were configured by the manufacturer in the original set up, but does introducing the DCtoDC charger alter the perspective?


I'd appreciate any advice on this approach and in particular responses to the two questions under issues.

[SYJetzt]

You should remove the battery isolator, and connect the alternator directly to the starter battery. Connect the voltage sensor of your alternator ( usually a yellow cable) to the battery terminal on the starter battery. Your alternator should be sufficient to feed the dc-dc charger (but 50 A is the most you can get from it long-term!). You need to check your BMS of your Lifepo, what's happening if your battery gets overcharged! If your BMS disconnects the charger for itself, your chargers maybe get damaged ( chargers do not like to be disconnected on their output under load). If your BMS has an overcharge output, you can wire it over a relay to the ignition port of your dc2dc charger or/and to the mains AC input of the AC2DC charger.

[symphony2]

Not sure why you would want to go to all that trouble and expense when you could achieve much the same objective by simply installing 3* 115Ah AGMs for the house bank and a small 70Ah FLA for the engine start. This is a huge jump from your current capacity. No need to change the charging system except just connect the solar to the house bank only.

I appreciate that you have bought the lithium but it really is not necessary to go that route. There is a tendency to jump into technology that offers certain characteristics without first identifying what you actually need to achieve your objective. First thing is to install a battery monitor and measure your daily consumption (you can do this on paper first to get an idea by recording the power consumption of individual items). Then record the daily charging input, in your case probably mainly from solar, but also from running the engine or from shorepower. You may well find that you deficit is small so your storage capacity does not need to be large.

If you only have the typical 12v sailing and domestic consumers then there is probably no advantage in going to lithium. This really comes into its own if you are a liveaboard mostly unconnected to shorepower and particularly if you want to run some domestic loads such as an induction cooker through an inverter.

[TonyM]

Thanks for the responses.
'SYJetzt' - I'll check on the Lithium batteries overcharge protection circuit. My understanding is that it will cease accepting a charge when/if the level is reached. I had not considered what that would do to the charging unit, I'll investigate this further, it is intended for LiFePO4 batteries. The ACtoDC charger is a Victron system suitable for LiFePO4 batteries. When it reaches a full state it goes into storage mode. Thanks for the advice on the Isolator. Removing it shouldn't present a problem. It will mean removing the House Battery connection completely. I may get back to you on this after I've sorted out how to achieve the disconnect.

'symphony2' - Again, thanks for your comments. There are a number of reasons I've chosen this path. I've been carrying 300ah's of deep cycle FLA for the past 10 years, replacing once 5 years ago. The cost of good FLA's or AGM's is about the same (here) for a mid priced lithium battery. But I also have additional motivations, this year my insurance company required a renewed gas certification - fine I thought its properly set up for the stove and oven and properly certified - Unfortunately the rules/requirements have changed in the last 10 years and the gas specialist pointed out the changes I would require. To achieve the new certification was as expensive as removing the gas fittings, installing a small induction stove and a microwave and converting the electrics to Lithium + adding a 3kw inverter (which is more than I need).  This combination of events took me down the Lithium track.

[symphony2]

Ok, that was not clear - my comments were based on you saying your house bank was 100Ah capacity. However suspect you will find you new 200Ah lithium inadequate for your consumption through the inverter for anything more than occasional use.

Interested in your comments about gas standards. In Europe the Bavaria system meets all standards (even though it has rubbish fittings!). What is it that does not meet Oz standards?

[TonyM]

Hi 'symphony2', I intend to do as you suggested and monitor usage over time and I will consider adding a 2nd 200ah battery in the not too distant future.

Re the Gas. The fittings for attaching the gas bottle and the connectors to the oven have updated specifications and needed to change. The main issue was that the fixed line from the solenoid to the cabin was not fully insulated, a requirement of the new standards, this is where most of the expense occurred. He mentioned a few other things like the the oven did not have auto cut off if the flame extinguished - but by this time the dollars had mounted up to a point where I new where I was heading. Remember that the original certification (in Germany) was done in 2006 - much has changed since then, at least here. Also the gas specialist was of the view that it was not a very good job to begin with - which may be true, but it had never given me any problems in the 10 years I've had the boat.
Appreciate the feedback - thanks

[tiger79]

I didn't think that updated gas regulations applied retroactively.