Domestic batteries replacement

[PaulRainbow]

Maybe....but not necessarily. I did drop in lithium , watched it carefully and turns out I did not need to buy anything else.

I suspect the same would be true for many small boat systems adding Lithium - certainly not all but many will work well without any additional kit.

So, you have just dropped Lithium in, in place of lead acid, without adding anything else, or making any other changes "apart from some charger settings " ?

No BMS ?
Nothing to protect the alternator ?
Nothing to protect the batteries form extremes of temperature ?
Nothing to protect the batteries from over charge ?
Nothing to protect the batteries from under charge ?

Etc, etc

 

[geem]

Maybe....but not necessarily. I did drop in lithium , watched it carefully and turns out I did not need to buy anything else.

I suspect the same would be true for many small boat systems adding Lithium - certainly not all but many will work well without any additional kit.

Would you care to elaborate? Do you have an alternator? Did you install correct fusing?

 

[Poey50]

Maybe....but not necessarily. I did drop in lithium , watched it carefully and turns out I did not need to buy anything else.

I suspect the same would be true for many small boat systems adding Lithium - certainly not all but many will work well without any additional kit.

It's rarely the case that a drop-in doesn't work. The question is whether you have constructed a safe and seaworthy system that lasts long enough to justify the upfront expense. A regular complaint on forums is of drop-ins that quickly lose capacity, usually a sign of charging errors.

 

[ckris]

So, you have just dropped Lithium in, in place of lead acid, without adding anything else, or making any other changes "apart from some charger settings " ?

No BMS ?
Nothing to protect the alternator ?
Nothing to protect the batteries form extremes of temperature ?
Nothing to protect the batteries from over charge ?
Nothing to protect the batteries from under charge ?

Etc, etc

Drop in lithium I used included a configurable BMS with Bluetooth. Supplier also set BMS parameters specifically for hybrid.

I carefully checked the alternator charge current and happily was well within capacity. If bms disconnects the battery any surge is absorbed by conventional lead acid.

Lithium battery has temperature protection.

BMS parameters are set conservatively to protect from over/under charge.

It just works....astonishingly well.

 

[ckris]

Would you care to elaborate? Do you have an alternator? Did you install correct fusing?

Yes, have alternator.

Define correct fusing? I understand the debate about t class fuses but they are hard to get, there is already a degree of protection in the bms so have kept existing fuse.

 

[PaulRainbow]

Drop in lithium I used included a configurable BMS with Bluetooth. Supplier also set BMS parameters specifically for hybrid.

I carefully checked the alternator charge current and happily was well within capacity. If bms disconnects the battery any surge is absorbed by conventional lead acid.

Lithium battery has temperature protection.

BMS parameters are set conservatively to protect from over/under charge.

It just works....astonishingly well.

So you didn't just install a Lithium battery.

 

[geem]

Yes, have alternator.

Define correct fusing? I understand the debate about t class fuses but they are hard to get, there is already a degree of protection in the bms so have kept existing fuse.

So how do you charge the lithium? B2B? Or direct from alternator?
Class T should be considered a minimum standard for lithium not an option. A direct short of your cables down stream from the lithium battery will only be dealt with by a class T or equivalent fuse. It should be mounted no more than 7" from the lithium battery ideally

 

[ckris]

It's rarely the case that a drop-in doesn't work. The question is whether you have constructed a safe and seaworthy system that lasts long enough to justify the upfront expense. A regular complaint on forums is of drop-ins that quickly lose capacity, usually a sign of charging errors.

Yes, agree you need to pay attention as lithium is different.......but quite possible to do and much easier than is sometimes portrayed.

I will keep an eye on capacity over the years to come but find it hard to believe it will not be a huge improvement on agm capacity degradation.

 

[ckris]

So you didn't just install a Lithium battery.

Drop in lifepo4. Bms included in the box. I did spend 4 years reading as much as I could about it and being scared off by the possible downsides that have largely not materialised.

 

[ckris]

So how do you charge the lithium? B2B? Or direct from alternator?
Class T should be considered a minimum standard for lithium not an option. A direct short of your cables down stream from the lithium battery will only be dealt with by a class T or equivalent fuse. It should be mounted no more than 7" from the lithium battery ideally

Direct from alternator.

Agree class T would be ideal, but not that it should be considered a minimum. I do not see it as that black and white.

 

[PaulRainbow]

Direct from alternator.

Agree class T would be ideal, but not that it should be considered a minimum. I do not see it as that black and white.

Seriously ?

No wonder insurance companies are starting to insist that Lithium installations are carried out by competent professionals.

So what fuse do you have at the Lithium battery ?

What steps have you taken to protect the alternator from burning out if you start the engine with a heavily depleted Lithium battery ?

 

[Poey50]

Drop in lithium I used included a configurable BMS with Bluetooth. Supplier also set BMS parameters specifically for hybrid.

I carefully checked the alternator charge current and happily was well within capacity. If bms disconnects the battery any surge is absorbed by conventional lead acid.

Lithium battery has temperature protection.

BMS parameters are set conservatively to protect from over/under charge.

It just works....astonishingly well.

I've heard of suppliers adjusting the high and low voltage disconnect for parallel hybrid use. I'd be interested to know the figures used and supplier. If done correctly that can protect the LFP and, with the lead acid left in the system, the alternator is protected from any high voltage disconnect. It is a simple but misleadingly attractive system. Because, less well known is that it can cause problems of undercharging of the lead acid if there is anything more that relatively shallow use of the lead acid. Also there might be insurance concerns as the ISO does not support mixing of lead acid and LFP chemistries in parallel or series. The two main popularisers of the method (Zwerfcat and Emily and Clarke) eventually designed a special BMS to get round the lead acid under-charging issue.

I agree with others on Class-T fusing. For a very small pack an MRBF might be sufficient but anything less would be vulnerable to arcing. The amperage flowing into a dead short is massively larger than lead acid.

 

[geem]

Direct from alternator.

Agree class T would be ideal, but not that it should be considered a minimum. I do not see it as that black and white.

Direct from alternator.

Agree class T would be ideal, but not that it should be considered a minimum. I do not see it as that black and white.

Rod Collins wrote the whitepaper that will become the ABYC standard for lithium. He put in writing that class T should be considered the minimum standard.

 

[geem]

I've heard of suppliers adjusting the high and low voltage disconnect for parallel hybrid use. I'd be interested to know the figures used and supplier. If done correctly that can protect the LFP and, with the lead acid left in the system, the alternator is protected from any high voltage disconnect. It is a simple but misleadingly attractive system. Because, less well known is that it can cause problems of undercharging of the lead acid if there is anything more that relatively shallow use of the lead acid. Also there might be insurance concerns as the ISO does not support mixing of lead acid and LFP chemistries in parallel or series. The two main popularisers of the method (Zwerfcat and Emily and Clarke) eventually designed a special BMS to get round the lead acid under-charging issue.

I agree with others on Class-T fusing. For a very small pack an MRBF might be sufficient but anything less would be vulnerable to arcing. The amperage flowing into a dead short is massively larger than lead acid.

I looked at the hybrid option. I couldn't see a way around the undercharged lead battery problem. In addition, what happens when the under charged lead battery fails? How much protection do you have for the lithium in this scenario? If the lead battery has a cell failure and boils off the electrolyte in the remaining cells and you get a lead battery short you really need that class T fuse desperately

 

[Poey50]

I looked at the hybrid option. I couldn't see a way around the undercharged lead battery problem. In addition, what happens when the under charged lead battery fails? How much protection do you have for the lithium in this scenario? If the lead battery has a cell failure and boils off the electrolyte in the remaining cells and you get a lead battery short you really need that class T fuse desperately

Exactly. If simple parallel-hybrid was that good why on earth would anyone use any other kind of set-up? It certainly finds no favours among LFP experts judging by the periodic discussions on the Lithium Batteries on a Boat Facebook Group.

 

[ckris]

Seriously ?

No wonder insurance companies are starting to insist that Lithium installations are carried out by competent professionals.

So what fuse do you have at the Lithium battery ?

What steps have you taken to protect the alternator from burning out if you start the engine with a heavily depleted Lithium battery ?

When I bought my boat there was no fuse at either battery. This was standard from the builder and had been like that for 20 years. My point is there are plenty of imperfect installs of la systems.

I added a mega fuse next to the house battery with minimal cable length, and have not changed that after adding lifep04....yet. Partly because when I looked it was hard to find t class fuse supplier....I may yet change this.

What is the short circuit current of a 100ah agm? How much extra risk am I taking on with a 100ah lifepo4?

The bms has discharge overcurrent protection of 110a. I know you will say this should not be relied upon bit it is better than agm!

I do not think this is greater risk than the agm set up, but having said that do recognise t class is the gold standard and interested in your view. As said, I may well upgrade when I can.

 

[ckris]

I looked at the hybrid option. I couldn't see a way around the undercharged lead battery problem. In addition, what happens when the under charged lead battery fails? How much protection do you have for the lithium in this scenario? If the lead battery has a cell failure and boils off the electrolyte in the remaining cells and you get a lead battery short you really need that class T fuse desperately

In practice you rarely if ever cycle the agm. If you do the alternator charges it as before, just the lifepo4 will have quietly switched itself off when it reaches the pack voltage protection leaving you in the same position as having a pure la set up.

I do not see any greater risk with la failure as when having 2 agm in parallel. The bms has discharge overcurrent protection.

 

[ckris]

Exactly. If simple parallel-hybrid was that good why on earth would anyone use any other kind of set-up? It certainly finds no favours among LFP experts judging by the periodic discussions on the Lithium Batteries on a Boat Facebook Group.

Try 12 volt boating Facebook group, there are plenty of people concluding the opposite.

 

[Poey50]

Try 12 volt boating Facebook group, there are plenty of people concluding the opposite.

Yes, I'm aware of that group. It seems to be primarily for motorboats and narrowboats. These have plenty of power available, therefore lengthy charging times are not generally an issue. Shallow use of the lead acid after the LFP is heavily discharged isn't a problem since the LFP will keep the lead acid trickle charged.

 

[ckris]

What steps have you taken to protect the alternator from burning out if you start the engine with a heavily depleted Lithium battery ?

None, when deeply discharged the lifepo4 takes 50 amps from a 115a alternator. Well within capacity.