Lithium battery conversion

[vas]

My recent Lithium installation is hybrid. I have 2 x 60a @24v alternators (twin engine mobo) and don't feel inclined to spend close to £200 for a Victron DC-DC charger with just a 17a output. Also not inclined to spend the excessive cost of high output alternators.

So far, it's looking good, not seen the alternators putting out more than 30a each. Just connected the Victron system to the N2K network, so i'll be able to monitor everything from the flybridge next time we're out.

Paul, I'm a bit confused on how your hybrid vs what SeaChange in #4 describes compare.

I do run a what I'd call full hybrid system in that MPPT, Multi-II and 60A port engine alternator (via a Stirling regulator) all go to a 4XTrojan T105RE bank which runs permanently linked to a 8 cell 304Ah EVE cell LiFePO4 bank. LiFePO4 has a 500A BlueSea relay disconnect (wired to the bms) and a T-class fuse.
diyBMS (its a brand of open source bms, with 1A passive ballance per cell, google it) is not a solidstate job like the ones you all seem to be using, so I can go 2C+ charge or discharge or whatever I want on the bank without issues as loads go straight to the battery terminals. Realistically I typically go 0.5C-0.8C if I run watermaker and a few other loads in the evening (which I avoid but it's beyond the point) so I'm not really taking full advantage of not having a solid state system, which I guess would be more interesting to the 12V wired boats.

So having both banks linked means that if the bms is not happy (battery fully charged and alternator still pumping 20-30A due to extensive motoring) or battery is lower than 15%SoC, then bms instructs the BlueSea to take the LiFePO4 bank off line leaving the T105 to take care of the situation. No spikes and burning the alternator this way.

V.

 

[Bobc]

Hi chaps. I'm following this with interest, as I'm going to move to lithium in the spring, and have a couple of questions:-

1./ A grade cells vs B grade cells.
It has been suggested here that you MUST have A grade cells on a boat. Can I ask why? What are the differences between A grade and B grade? If B grade are no good for a boat, what are they used for (on the basis that boats are not big users of amps).

2./ BMS choice.
It has also been suggested that you MUST have a BMS with bluetooth. Can I ask why? My understanding of a BMS is that it monitors and manages the cells to make sure that they are balanced, do not get over-charged, and protect the cells for being over/under charged or having too much draw on them. If so, why do I need to be able to monitor them myself with bluetooth. Won't using a Victron Smart Shunt do the job?

There seems to be some "religion" around this subject, a bit like you get with anchors. Is it really the case?

 

[Sea Change]

Paul, I'm a bit confused on how your hybrid vs what SeaChange in #4 describes compare.

My system isn't hybrid, it's two independent systems. I don't have the facility to put them in parallel.

 

[Sea Change]

Hi chaps. I'm following this with interest, as I'm going to move to lithium in the spring, and have a couple of questions:-

1./ A grade cells vs B grade cells.
It has been suggested here that you MUST have A grade cells on a boat. Can I ask why? What are the differences between A grade and B grade? If B grade are no good for a boat, what are they used for (on the basis that boats are not big users of amps).

Some of us are drawing big currents. When I'm cooking, I'll be drawing over 200A for up to an hour.
I don't think the difference between A and B grade adds up to all that much in the scheme of things.

2./ BMS choice.
It has also been suggested that you MUST have a BMS with bluetooth. Can I ask why? My understanding of a BMS is that it monitors and manages the cells to make sure that they are balanced, do not get over-charged, and protect the cells for being over/under charged or having too much draw on them. If so, why do I need to be able to monitor them myself with bluetooth. Won't using a Victron Smart Shunt do the job?

There seems to be some "religion" around this subject, a bit like you get with anchors. Is it really the case?

A Bluetooth BMS allows you to set your own parameters. Without it, you just have a black box and no idea of what's going on inside. Your cells could be massively out of balance, your disconnect settings could be preset to favour available capacity over lifespan.

Once it's all set up, you won't really need to use the Bluetooth function very often, but it's really good to be able to keep an eye on what's going on inside the box. Most people think it's worth the extra cost.

 

[PaulRainbow]

Paul, I'm a bit confused on how your hybrid vs what SeaChange in #4 describes compare.

In post #4 he says "A hybrid system where lithium and lead acid batteries are permanently in parallel is another way, but I'm not sure if anybody on this forum has tried it."

That is what i have (he doesn't). It looks like you and i both run essentially the same type of system.

I have an 8 cell 280ah EVE LifeP04 bank and a pair of SLA batteries in series (these were 2 of the previous batteries). Each bank has its own fuse and isolator and are then connected in parallel to the positive busbar. The LifeP04 bank is connected to a JK BMS.

My 2 x 60a @24v alternators are both fitted with diode packs to allow them to charge the engine and domestic batteries, this is how the boat was built. Both alternators are connected to the SLA batteries, which in turn charge the LifeP04 bank.

I do run a what I'd call full hybrid system in that MPPT, Multi-II and 60A port engine alternator (via a Stirling regulator) all go to a 4XTrojan T105RE bank which runs permanently linked to a 8 cell 304Ah EVE cell LiFePO4 bank. LiFePO4 has a 500A BlueSea relay disconnect (wired to the bms) and a T-class fuse.
diyBMS (its a brand of open source bms, with 1A passive ballance per cell, google it) is not a solidstate job like the ones you all seem to be using, so I can go 2C+ charge or discharge or whatever I want on the bank without issues as loads go straight to the battery terminals. Realistically I typically go 0.5C-0.8C if I run watermaker and a few other loads in the evening (which I avoid but it's beyond the point) so I'm not really taking full advantage of not having a solid state system, which I guess would be more interesting to the 12V wired boats.

So having both banks linked means that if the bms is not happy (battery fully charged and alternator still pumping 20-30A due to extensive motoring) or battery is lower than 15%SoC, then bms instructs the BlueSea to take the LiFePO4 bank off line leaving the T105 to take care of the situation. No spikes and burning the alternator this way.

V.

Generally speaking, we have the same system. One difference, which could be very useful, is that my BMS will shut down charging and loads independently, can you not get yours to do that ? So it can shut down the charging, as you describe, but leave the loads connected.

 

[Trident]

Depends on what it's used for.
I set my boat up so that the lithium was only powering domestic systems, and I kept my old lead acid bank to do navigation gear, a handful of interior lights, and one heads.
Funnily enough, the only time this redundancy was needed was when the lead acid system failed, due to corrosion in an isolator.

That's a fairly unique set up - the point is surely that people need to understand that its not simply inconvenient if batteries fail on boats it can be deadly and thus risk taking is a bad idea. In my case all the nav lights etc run off Lithium but I have three separate packs that would all have to fail and even then there is a remote battery with a quick Anderson connector that I can plug in in seconds to power everything if all failed - though that's much less likely with lithium done right than with lead acid

 

[Trident]

Hi chaps. I'm following this with interest, as I'm going to move to lithium in the spring, and have a couple of questions:-

1./ A grade cells vs B grade cells.
It has been suggested here that you MUST have A grade cells on a boat. Can I ask why? What are the differences between A grade and B grade? If B grade are no good for a boat, what are they used for (on the basis that boats are not big users of amps).

2./ BMS choice.
It has also been suggested that you MUST have a BMS with bluetooth. Can I ask why? My understanding of a BMS is that it monitors and manages the cells to make sure that they are balanced, do not get over-charged, and protect the cells for being over/under charged or having too much draw on them. If so, why do I need to be able to monitor them myself with bluetooth. Won't using a Victron Smart Shunt do the job?

There seems to be some "religion" around this subject, a bit like you get with anchors. Is it really the case?

I think those have been addressed above but - Geem has used B grade with no issues so far (short test) so its not essential to go grade A but why wouldn't you? The cost difference is maybe £10 a cell and if you go to a good supplier they give full documentation with A grade and match batches and charge state etc so you know what you are starting with.

As sea change says being able to set the parameters is important and thats normally by BT.

Again I noted above that good monitoring system hardwired is perfectly safe and I've installed systems that way on dozens of boats. I've also found the BT on many batteries - even the Renogy stuff, to be poor and cut in and out etc. What's also essential is that you can monitor fully the batteries including the cells individually to ensure that they are not problematic and right now the best and easiest way to do that is a with a separate BMS with blue tooth . You can of course trust the BMS to do everything for you and accept that it may come as a shock if it doesn't but it makes sense to be able to check things yourself.

The smart shunt will give you charge value, state of charge , discharge value etc but doesn't monitor individual cells in a pack and the most common failure in LiFePo4 is a single cell getting out of balance or failing which then means the whole lot fails. Being able to see what happens on the cell level is important . I have BT BMS and the Smart shunt because the shunt gives quick and easy checking on SOC and what the solar etc are doing and gives a steady battery state for the MPPT and inverter etc to read rather than all using their own different ones depending on wire length etc . I can look at the shunt app regularly and then check the BMS maybe each day or every other day to be sure the cell health is good and so on

 

[Sea Change]

That's a fairly unique set up - the point is surely that people need to understand that its not simply inconvenient if batteries fail on boats it can be deadly and thus risk taking is a bad idea. In my case all the nav lights etc run off Lithium but I have three separate packs that would all have to fail and even then there is a remote battery with a quick Anderson connector that I can plug in in seconds to power everything if all failed - though that's much less likely with lithium done right than with lead acid

Maybe it is unusual. My boat already had a perfectly good lead acid system and I just left that alone. I added new solar, lighting, a large inverter, and electric galley equipment as an entirely new system. I later transferred some of the cabin lights and the existing 12v fridge across.

To me it was easier and simpler to create a whole new system. I didn't want to put the lithium batteries in the engine bay where the lead acids live. Simply throwing away the lead acid batteries and installing lithium in their place means you have to carefully consider a whole lot of stuff that was installed already without lithium in mind. That includes all of your wiring, isolators, fuses, chargers, etc.

 

[Trident]

Maybe it is unusual. My boat already had a perfectly good lead acid system and I just left that alone. I added new solar, lighting, a large inverter, and electric galley equipment as an entirely new system. I later transferred some of the cabin lights and the existing 12v fridge across.

To me it was easier and simpler to create a whole new system. I didn't want to put the lithium batteries in the engine bay where the lead acids live. Simply throwing away the lead acid batteries and installing lithium in their place means you have to carefully consider a whole lot of stuff that was installed already without lithium in mind. That includes all of your wiring, isolators, fuses, chargers, etc.

No argument here - it sounds well thought out and obviously works.

 

[vas]

Generally speaking, we have the same system. One difference, which could be very useful, is that my BMS will shut down charging and loads independently, can you not get yours to do that ? So it can shut down the charging, as you describe, but leave the loads connected.

no, cannot differentiate as LiFePO4 bank has the end terminals connected to the BlueSea 500A relay, so if/when the BMS says no, it disconnects both in and out.
tbh, once I figure out how to get the Stirling alternator regulator to turn off when bank is full, I'm done. Seems that it's doable but haven't had the time to investigate, only happened to disconnect once in an 12h motoring day when LiFePO4 was full, balanced and alternator was still pumping 20odd Amps...

forgot to mention that the bms has a victron simulation mode so connects to Cerbo (in my case raspberry running VenusOS) so it can regulate multi charging and discharging as well as MPPT charging (only Stirling is left out). So I have all cell level monitoring and overview in the victron display onboard (and via VRM on my pc at home/work)

 

[geem]

I think those have been addressed above but - Geem has used B grade with no issues so far (short test) so its not essential to go grade A but why wouldn't you? The cost difference is maybe £10 a cell and if you go to a good supplier they give full documentation with A grade and match batches and charge state etc so you know what you are starting with.

As sea change says being able to set the parameters is important and thats normally by BT.

Again I noted above that good monitoring system hardwired is perfectly safe and I've installed systems that way on dozens of boats. I've also found the BT on many batteries - even the Renogy stuff, to be poor and cut in and out etc. What's also essential is that you can monitor fully the batteries including the cells individually to ensure that they are not problematic and right now the best and easiest way to do that is a with a separate BMS with blue tooth . You can of course trust the BMS to do everything for you and accept that it may come as a shock if it doesn't but it makes sense to be able to check things yourself.

The smart shunt will give you charge value, state of charge , discharge value etc but doesn't monitor individual cells in a pack and the most common failure in LiFePo4 is a single cell getting out of balance or failing which then means the whole lot fails. Being able to see what happens on the cell level is important . I have BT BMS and the Smart shunt because the shunt gives quick and easy checking on SOC and what the solar etc are doing and gives a steady battery state for the MPPT and inverter etc to read rather than all using their own different ones depending on wire length etc . I can look at the shunt app regularly and then check the BMS maybe each day or every other day to be sure the cell health is good and so on

The Grade A or B thing is interesting. Everything I can find, research wise, suggests Grade A is only really needed if you are using them for motive power. This application drives cells far harder than a domestic battery set up on a boat. Having matched and balanced cells is important for motive power.
On most boats, the C rating for charge and discharge will be tiny. Once you start using larger loads for electric cooking, bow thrusters, aircon, etc, you may find that Grade B cells go out of balance, but I suspect not beyond the ability of an active balancer to easily fix. When we set of full-time cruising again next summer, we will be running identical 280Ah 24v batteries, one .Grade A cells and one Grade B cells. I should have lots of useful information to report back.

 

[jac]

Going back to the point of emergency engine starting i spotted this 12V 200Ah Pro Deep Cycle Lithium Iron Phosphate Battery w/Bluetooth & Self-heating Function

Bluetooth and the maximum discharge is 270A for 30 secs. Obviously depends on the size of the engine but that should cover most yacht engines surely??

 

[PaulRainbow]

Going back to the point of emergency engine starting i spotted this 12V 200Ah Pro Deep Cycle Lithium Iron Phosphate Battery w/Bluetooth & Self-heating Function

Bluetooth and the maximum discharge is 270A for 30 secs. Obviously depends on the size of the engine but that should cover most yacht engines surely??

So would a £80 LA battery

 

[jac]

So would a £80 LA battery

Indeed - but an £80 LA battery wouldn't last long as a domestic battery.

The issue was that a domestic Lithium bank of say 200Ah -300Ah might be the size needed for a typical cruiser that isn't going all electric but wants to upgrade from AGM / FLA for the domestic bank. WIth AGM / LA if the engine start battery fails the standard isolators allow you to start from the domestic.

if the BMS on a lithium wouldn't start the engine in an emergency then it's no good in a marine environment. A Battery such as the oe i linked to should be fine for a domestic bank and in an emergency also start the engine

 

[geem]

Indeed - but an £80 LA battery wouldn't last long as a domestic battery.

The issue was that a domestic Lithium bank of say 200Ah -300Ah might be the size needed for a typical cruiser that isn't going all electric but wants to upgrade from AGM / FLA for the domestic bank. WIth AGM / LA if the engine start battery fails the standard isolators allow you to start from the domestic.

if the BMS on a lithium wouldn't start the engine in an emergency then it's no good in a marine environment. A Battery such as the oe i linked to should be fine for a domestic bank and in an emergency also start the engine

If you build your own lithium batteries, in an emergency, you can bypass the bms and start from the cells.

 

[PaulRainbow]

Indeed - but an £80 LA battery wouldn't last long as a domestic battery.

The issue was that a domestic Lithium bank of say 200Ah -300Ah might be the size needed for a typical cruiser that isn't going all electric but wants to upgrade from AGM / FLA for the domestic bank. WIth AGM / LA if the engine start battery fails the standard isolators allow you to start from the domestic.

if the BMS on a lithium wouldn't start the engine in an emergency then it's no good in a marine environment. A Battery such as the oe i linked to should be fine for a domestic bank and in an emergency also start the engine

No, the battery you linked to won't work as an emergency start battery, unless it's a very small engine, as it's limited to 200a. Plus, it's expensive.

If you fitted one of the LifeP04 packs we are discussing here, with a bog standard LA battery in parallel, you can start the engine from that. Plus. the LA battery protects you from a BMS shutdown for any reason. It also protects your alternator from shutdowns and from the LifeP04 trying to run the alternators at high output for extended time.

There are other ways to achieve the above, of course.

 

[rogerthebodger]

IF you have a lithium with BMS and a separate LA engine start battery, would it be possible to ue the shutdown of the BMS to switch the engine start battery to power the domestic from the engine battery for a short time.

If so, how would this be done

 

[geem]

IF you have a lithium with BMS and a separate LA engine start battery, would it be possible to ue the shutdown of the BMS to switch the engine start battery to power the domestic from the engine battery for a short time.

If so, how would this be done

I have a 24v boat so 24v starting batteries achieved via 2 x100Ah 12v batteries. I have a link switch so that in the unlikely event of both lithium batteries going down, I can insert a key into the link switch and run the full domestic installation from the engine batteries. It's a simple system.

 

[Sea Change]

I have a 24v boat so 24v starting batteries achieved via 2 x100Ah 12v batteries. I have a link switch so that in the unlikely event of both lithium batteries going down, I can insert a key into the link switch and run the full domestic installation from the engine batteries. It's a simple system.

Sounds similar to the system I built. The navigation gear can run off either lead acid or lithium. I didn't want it to be possible to put them in parallel (maybe I was being over cautious there but it didn't seem like a good idea) so I tried to find a high current 1-off-2 switch with no 'both' position. I couldn't find one, so instead I just have two keyed isolators, and one key. You have to turn off one bank, remove the key, and then turn the other one on. The key cannot be removed in the 'on' position. Total cost about £16, and it's foolproof enough for me.

Obviously you do lose everything for a couple of seconds whilst changing over, but I can live with that. Generally I use it to favour one bank or the other depending on whether I'm motoring or not.

 

[gregcope]

I kept my 1-2-both switch and labeled it up as to only use “both” in an emergency.

No. 1 is a Sealed LA AGM start battery which has a victron b2b to no.2 two 300Ah DIY LifePo4.

I can start my engine off either or both.

Beyond forgetting to turn it off from “both” and possibly trashing the alternator I cannot see a downside to keeping the 1-2-Both for emergencies.

Feedback welcome.

In other news I would it again. Now it would be 20% cheaper as prices have dropped. Also quicker and less risk as UK suppliers like Fogstar can sell the boxes and cells as well as a wide choice of BMSes.