Lithium Batteries 2 - The Drifted Thread!

[PCUK]

Apologies to Duncan for partially sidetracking his post. After all the advice from all the different sources I have come to the conclusion that I should stick to what I know and use Lead Acid for the starter battery. Say 105ah plus two Lead Acid (leisure) batteries about the same for the house and another separate smaller Lead Acid battery for the fridge. All separated using VSRs and a 1-2-Both switch for selecting the house battery in use. Then just change them every couple of years as they die!

The boat is a restored beyond new Reinell V-204 at 26 ft originally (now 28ft with the extended hull bathing platform that I built on). Originally a 1978 boat now totally restored and ready for relaunching next spring. Everything is new including the engine and drive and 150 amp alternator (not smart). Let's not mention the lack of economic sense - I did it cos' I wanted to! It will be based somewhere on the Bristol Channel. Currently hoping to get a pontoon mooring in the not too distant future at Burnham-on-Sea Motor Boat and Yacht Club or as a second choice Watchet. The boat will mainly be used at weekends and odd days hopefully with much of that time at anchor and occasional long cruises to the South Coast, Ireland and West Wales.

All opinions on the proposed set-up gratefully received. Peter

 

[dankilb]

Cool boat! Congrats on the refit.

My first question would be - why the separate fridge battery? That’s not something I’ve come across before.

The separating of house batteries was something I was struggling to get my head around in the previous thread.

 

[PaulRainbow]

From the above, Lithium makes no sense for you.

As mentioned in the other thread, it's not a good idea to separate the house batteries, neither is it a good idea to have a separate fridge battery. Firstly, using one battery at a time will mean that the single battery will get cycled more and die sooner. Secondly, charging one battery at a time will make very poor use of the 150a alternator.

In my opinion, your system needs to be a nice, simple one. A single battery for engine starting and 3 leisure batteries for domestic use. Both banks kept separate from each other, with a 3rd switch for emergency starting. Alternator connected to the engine battery, other charging connected to the domestic bank, with a VSR between the two banks.

Fit a decent battery monitor to keep an eye on things and don't discharge the domestics past 50%

The following schematic should suit you well, just ignore one of the domestic batteries.

 

[PCUK]

The fridge battery is just there to reduce the drain on the main house batteries. Just something I've always done.
Same here as to the battery separation with anything other than lead acid. Another reason to stick with what I know, especially as I probably don't need anything higher tech'.

 

[penfold]

A separate fridge battery is a weird idea, as though one particular hotel load is different from all the others. KISS

 

[PCUK]

Thanks Paul, the 1-2-both switch won't be used for selecting the battery to be charged, only for house use selection. I can't see how keeping the batteries separated will affect charging when using VSRs. In fact I'll probably go back to Adverc battery sensing and then use diodes for separation. Your biggest help to me has been to confirm that I don't need a highly complex/expensive system and I accept that discharging the lead acid batteries separately won't please them!

 

[PCUK]

A separate fridge battery is a weird idea, as though one particular hotel load is different from all the others. KISS

Always worked well for me and many colleagues over many years.

 

[dankilb]

If the fridge load is a battery killer, then it’s the system that needs looking at - it doesn’t make sense just to let it run of it’s own battery, for the reasons Paul explain.

There’s no reason the fridge can’t run quite happily within the realms of your specs above.

A small solar charge input could help offset the fridge load anyway.

But you need to combine the house batteries. A bank is better than manual switching. It’s an unnecessary complexity and likely to do more harm than good.

 

[PaulRainbow]

Thanks Paul, the 1-2-both switch won't be used for selecting the battery to be charged, only for house use selection. I can't see how keeping the batteries separated will affect charging when using VSRs.

If you separate the batteries and connect them all to VSRs, they will effectively be a single bank whilst they are on charge.

In fact I'll probably go back to Adverc battery sensing and then use diodes for separation. Your biggest help to me has been to confirm that I don't need a highly complex/expensive system and I accept that discharging the lead acid batteries separately won't please them!

An Adverc, with your new alternator, will off nothing of benefit. Going back to diodes is a bad idea, as they impose a voltage drop of around .7v, the VSR has no voltage drop.

The schematic i posted is about as simple as it can get and allows for multiple charge sources (should they exist) without any additional hardware.

 

[geem]

The fridge battery is just there to reduce the drain on the main house batteries. Just something I've always done.
Same here as to the battery separation with anything other than lead acid. Another reason to stick with what I know, especially as I probably don't need anything higher tech'.

Separating the fridge load onto its own battery is not a good idea. The main load on the house bank is the fridge. Everything else combined is likely to impose a small load than the fridge. Put every domestic load on one domestic bank and your batteries will last longer.
As I said previously, we had Numax leisure batteries for 8 years. Fridge/freezer load and everything but the engine were on a single bank of 3x100Ah batteries. No shore power. Only ever solar charging with the occasional top up from engine whilst motoring. Keep the batteries away from the heat of the engine.

 

[PCUK]

I haven't even thought about adding solar yet. I think that's a job for a fresh thread!

 

[PaulRainbow]

I haven't even thought about adding solar yet. I think that's a job for a fresh thread!

If you follow the schematic in post #3, it's simply a case of fitting the panel/s, connect them to a controller and connect the controller directly to the domestic bank (with a fuse near the batteries). Solar will then charge all batteries, including the engine battery, without any additional hardware.

 

[PCUK]

Thanks again Paul, that's me sorted.

 

[GHA]

Always worked well for me and many colleagues over many years.

Interesting idea though. For a hybrid system to save splashing out on all lithium. Get a smaller drop in lithium just for the fridge so the main bank cycles much less & lasts longer & replace the fridge one after a load of years when it fails. Lose the benefits of lithium on the main bank but easier to implement. Suspect fair amount of battery damage could come from fridges pulling the main batts too low & it not getting fully charged again for a while.
Numbers might be too hard to crunch to see if it would actually make sense though, so many variables & every boat is different.
Save a few threadson here as well "My fridge turns on and off again". "Voltage is too low" ?

 

[SandyP]

Actually i after with having a separate fridge battery, 30ah
My mate and i have been discussing this at length

But the battery intended is a lithium not lead. This brings all the advantages of lithium, quick charge, robustness, lifetime, size. This greatly reduces the load on an old bank of Trojans, hopefully extending their lifetime (live aboard usage)

I use a small lithium pack solely for heating, worked perfectly now it's 3rd year

 

[Kelpie]

Interesting idea though. For a hybrid system to save splashing out on all lithium. Get a smaller drop in lithium just for the fridge so the main bank cycles much less & lasts longer & replace the fridge one after a load of years when it fails. Lose the benefits of lithium on the main bank but easier to implement. Suspect fair amount of battery damage could come from fridges pulling the main batts too low & it not getting fully charged again for a while.
Numbers might be too hard to crunch to see if it would actually make sense though, so many variables & every boat is different.
Save a few threadson here as well "My fridge turns on and off again". "Voltage is too low" ?

I started thinking about a sort of hybrid system to get the same kind of benefits- my idea was to charge the lithium quickly during the day when the sun is out, then use that to trickle charge the lead acid. Allows you to avoid sulphation or deep discharge of the lead acid, whilst taking advantage of the rapid charging of the lithium.

The reason I never went ahead was that it turned out that LFP cells were not any more expensive than good quality lead acid, so my idea of building a big cheap lead acid bank didn't really make sense.

 

[GHA]

Hi gang, sorry pcuk - don't want to start a new thread so hijacking yours for a moment.
Really can't handle it in these forums any more, the squabbling pensioners just make it too unpleasant & unworkable for most tech threads which turn into a bun fight within a few posts.
But trying to cobble together a home build lifepo4 BMS, might be a dead end but going for it anyway.
DIYsolar seems much better manners & friendly, thread there >
Home build LiFePo4 BMS - what should I be asking?
Putting notes in a blogger, as much for my own place to get at the datasheets as anything>
LiFePo4 batteries - DIY BMS.
And a discord for chatting in , doubt if that will get going but if anyone fancies a chat it's there.
Join the Rasp Pi boat monitoring Discord Server!

so now I log off and delete the password, cos the temptation to naively think some data and evidence will change the mind of some bickering pensioner gets too strong ??
?

Back t the thread....

 

[PaulRainbow]

Hi gang, sorry pcuk - don't want to start a new thread so hijacking yours for a moment.
Really can't handle it in these forums any more, the squabbling pensioners just make it too unpleasant & unworkable for most tech threads which turn into a bun fight within a few posts.
But trying to cobble together a home build lifepo4 BMS, might be a dead end but going for it anyway.
DIYsolar seems much better manners & friendly, thread there >
Home build LiFePo4 BMS - what should I be asking?
Putting notes in a blogger, as much for my own place to get at the datasheets as anything>
LiFePo4 batteries - DIY BMS.
And a discord for chatting in , doubt if that will get going but if anyone fancies a chat it's there.
Join the Rasp Pi boat monitoring Discord Server!

so now I log off and delete the password, cos the temptation to naively think some data and evidence will change the mind of some bickering pensioner gets too strong ??
?

Back t the thread....

Fantastic

 

[Gadget257]

PCUK, I've seen a few adverts for the Aptivolt Battery Management systems | Autonnic on the back of PBO recently and I am considering it as part of rewire on my boat. With its prioritised charging, this solution may meet your requirement for a separate battery for the fridge. Hopefully there is a formite out there who has installed it and can advise.

 

[Tranona]

PCUK, I've seen a few adverts for the Aptivolt Battery Management systems | Autonnic on the back of PBO recently and I am considering it as part of rewire on my boat. With its prioritised charging, this solution may meet your requirement for a separate battery for the fridge. Hopefully there is a formite out there who has installed it and can advise.

That is all too complicated. The OPs requirements are very simple - it is a small boat used for local cruising, not a liveaboard with heavy domestic requirements fed by by multiple sources using large and potentially variable battery banks. Post#3 gives a layout that absolutely no need to complicate it by splitting the batteries in the house bank and adding a separate battery for the fridge - indeed both those actions will lead to shorter battery life. A 2-300AH leisure or AGM house bank will cover all his potential needs and long life if he has a means of keeping the batteries fully charged between usage. Normally shorepower but if that is not available a solar panel feeding the house bank.