Backup Lithium Solution

[goeasy123]

Does this power station provide a 240v supply? In which case you could use something like a Victorian IP22 charger set to PSU mode to supply 12v for the boat. But it's an expensive and inefficient method.

Yes. That idea is going in the right direction. Something I can connect across the 12v system with the LA disconnected would work, but I might need more current carrying capacity than the V IP22.

Powerstations have 240VAC consumer sockets on them. You can connect them to the boat system just by plugging them into the shore power supply, but that doesn't solve the current bottle neck through the inverter/charger on the boat. The limitation of a powerstation is that they don't have a high current 12vdc out.... just car cigarette lighter capacity.

I was thinking for building my own powerstation a la Will Prowse, which gives me direct out from the battery. See here

 

[KompetentKrew]

I am reluctant to fit lithium to my boat as I think it would require an immense amount of rewiring to replace my current AGM system with lithium.

Once when these kinds of large lithium packs were mentioned before I thought it handy to have one as a lithium "expansion" similarly to how you suggest - by plugging it into the boat's shore power so the battery pack recharges the main bank or keeps it topped up. A hybrid-but-not-hybrid system, if you see what I mean.

Connecting the Ecoflow or Anker 767 to the boat's shore power would be a bit inefficient because it would be using the built in inverter to supply 220V to the shore power, and then the boat's own charger would be bringing it down again to about 13v to perform the 3-stage charging.

I see the Anker 767 has a 12v car socket on the side, which is rated at 10A so it occurs to me you could use a DC-DC charger plugged into this to charge your boats battery. The smallest DC-DC chargers I'm finding are about 18A or 20A though - the Sterling 'Wildside' caravan battery-to-battery charger, Victron Orion-Tr or Sargent DX320 - so you'd need to be using both of the Anker's 12v sockets in parallel to power the B2B charger, and you'd need to ensure both leads were separately fused in case you accidentally connected only one of them before switching on the supply to the charger. I'm not sure if I'd be conformable with this, as you might be using both 12v sockets at close to their maximum capacity for an extended period.

 

[KompetentKrew]

Powerstations have 240VAC consumer sockets on them. You can connect them to the boat system just by plugging them into the shore power supply, but that doesn't solve the current bottle neck through the inverter/charger on the boat. The limitation of a powerstation is that they don't have a high current 12vdc out.... just car cigarette lighter capacity.

I don't think the boat's charger is the bottleneck, so much as the absorption rate of the boat's lead-acid or AGM batteries.

AGMs are often touted (or used to be, before lithium came on the scene) as having a higher charge acceptance rate than lead acid batteries - they're ideally charged at 0.4c (i.e. with a current equivalent to 40% of their capacity), but they can only absorb this for about an hour or so, and only if they're fairly deeply discharged. 0.2c is more commonly quoted - i.e. it'll take about 3 hours to charge to about 60% full, and then it'll slow down after that.

This is why most battery chargers seem so "puny" - because the batteries' absorption rate makes more powerful ones redundant. My boat came with a 330Ah AGM bank (2x 165Ah Victrons) and I think the charger was about 40A. When the charger died last year I spent nearly £1000 replacing it with a meaty 70A charger before realising this (it was so expensive because it's a combi inverter-charger). The 330Ah battery could accept 130A for an hour (0.4c, 0.4 * 330), but its acceptance rate would soon drop as it became more fully charged. I realised that it doesn't really matter how powerful your battery charger is - almost no-one charges at 0.4c because such a big charger would be excessively expensive, and it'd only be operating at full capacity for an hour or so; a 40A (0.12c) or 70A (0.21c) battery charger (or even a 130A one, if I could afford it) makes no difference, because the charger operates in bulk charging mode for only a couple of hours, and you have to leave the boat plugged in overnight to get through the absorption and float charging stages so that the big bank is fully charged.

• What are the 3 Stages of Smart Chargers?
• How Fast Can an AGM Battery be Charged? - Marine How To

You opened this thread by saying you wanted to use the Ecoflow or Anker 767 because you don't want a hybrid system but I think, the way you're talking about charging, it would require a hybrid system. I think that you're going to have to accept the need to leave the large portable lithium power bank plugged in for several hours if you want to use it to charge your boat's battery. (Or to provide any signifiant charge, at least.)

 

[Beneteau381]

I don't think the boat's charger is the bottleneck, so much as the absorption rate of the boat's lead-acid or AGM batteries.

AGMs are often touted (or used to be, before lithium came on the scene) as having a higher charge acceptance rate than lead acid batteries - they're ideally charged at 0.4c (i.e. with a current equivalent to 40% of their capacity), but they can only absorb this for about an hour or so, and only if they're fairly deeply discharged. 0.2c is more commonly quoted - i.e. it'll take about 3 hours to charge to about 60% full, and then it'll slow down after that.

This is why most battery chargers seem so "puny" - because the batteries' absorption rate makes more powerful ones redundant. My boat came with a 330Ah AGM bank (2x 165Ah Victrons) and I think the charger was about 40A. When the charger died last year I spent nearly £1000 replacing it with a meaty 70A charger before realising this (it was so expensive because it's a combi inverter-charger). The 330Ah battery could accept 130A for an hour (0.4c, 0.4 * 330), but its acceptance rate would soon drop as it became more fully charged. I realised that it doesn't really matter how powerful your battery charger is - almost no-one charges at 0.4c because such a big charger would be excessively expensive, and it'd only be operating at full capacity for an hour or so; a 40A (0.12c) or 70A (0.21c) battery charger (or even a 130A one, if I could afford it) makes no difference, because the charger operates in bulk charging mode for only a couple of hours, and you have to leave the boat plugged in overnight to get through the absorption and float charging stages so that the big bank is fully charged.

• What are the 3 Stages of Smart Chargers?
• How Fast Can an AGM Battery be Charged? - Marine How To

You opened this thread by saying you wanted to use the Ecoflow or Anker 767 because you don't want a hybrid system but I think, the way you're talking about charging, it would require a hybrid system. I think that you're going to have to accept the need to leave the large portable lithium power bank plugged in for several hours if you want to use it to charge your boat's battery. (Or to provide any signifiant charge, at least.)

You nailed it with the size of the charger, good points. Ive always been amazed when I see people putting uprated alternators in to the system. Fir the reasins you have mentioned, their full capacity is never used.

 

[goeasy123]

I am reluctant to fit lithium to my boat as I think it would require an immense amount of rewiring to replace my current AGM system with lithium.

...and that rewiring introduces risk. Now we're getting somewhere!. Thanks.

It makes no sense to compromise an existing AGM system if it has worked for a particular usage scenario for many years. Any of the conventional ways for introducing Lithium are risky, expensive, and in my case defeat the 2 benefit of:

1. Being able to take power off the boat for 'off boat' purposes.
2. Reducing overall risk. For example, having a back up on long passages or in remote places if the inverter, charge sources or AGM's go down. I note in all the usual web discussions the fanboys of Lithium ignore that fact that the configurations they advocate introduce multiple function point, any one of which would fail the whole system.

It would be handy if powerstations had access to internal 12v battery terminals. but they don't. I think the pack inside is probably 48V.

An option is to build a portable system with a 12v Lithium rack battery and something like a SignatureSolar EG4 (which is 48v). Maybe that's my next question!!

 

[stephen_h]

£450 for 25.6 ah of extra capacity? Wow. The raw cells inside the plastic covering would cost 1/10 of that on the open market.

I can quite understand though that these could increase your lead acid longevity to up to 10 years. The reason for this is that the LFP will keep the lead acid on float the entire time. It will be the LFP that will be discharged and charged preferentially. So essentially the lead acid is there as an emergency back-up. If you keep a lead acid fully charged then - yes - a long life is to be expected. However if you decide to discharge deeply into your lead acid then you are likely to struggle to get it back to full because of the preferential charging of the LFP as said, and the long charging tail to get lead acid to 100% to avoid sulfation. So depending on usage these very expensive add-ons may give you a long lead acid life or an exceptionally short one.

The lead acid gets charged first and then the LFP so will extend the life of the LA. You are right, it is expensive, but I have very good LA and charging so this gives me extra storage power and light weight. No good if you want a complete new system.

 

[Poey50]

The lead acid gets charged first and then the LFP so will extend the life of the LA. You are right, it is expensive, but I have very good LA and charging so this gives me extra storage power and light weight. No good if you want a complete new system.

If the LFP is in parallel connection with the lead acid then I'm not sure how the lead acid takes priority in charging. Are you able to explain how that works?

 

[goeasy123]

If the LFP is in parallel connection with the lead acid then I'm not sure how the lead acid takes priority in charging. Are you able to explain how that works?

Maybe the LA does not take priority. I think the BOS LE is sold as a LA life extender and a little bit extra charge at the end of the solar day, and not a supply in itself.

It could be that the BOS LE and LA in parallel take charge together. The BOS LE, because it's small finished charging and the LA continues to take charge until there's no input from the charging sources (engine off, sun goes down etc.) then the BOS LE back fills the LA up to float at the slow rate LA can accept the final charge. ??

 

[Poey50]

Maybe the LA does not take priority. I think the BOS LE is sold as a LA life extender and a little bit extra charge at the end of the solar day, and not a supply in itself.

It could be that the BOS LE and LA in parallel take charge together. The BOS LE, because it's small finished charging and the LA continues to take charge until there's no input from the charging sources (engine off, sun goes down etc.) then the BOS LE back fills the LA up to float at the slow rate LA can accept the final charge. ??

If LFP is connected in parallel to lead acid and both are charged together then, because of their different characteristics, LFP will inevitably charge first. Any voltage above 13.6 volts will charge LFP to full (and beyond unless a high voltage event stops it). For any charging voltage this will be much more rapid than lead acid because of the way resistance ramps up with charge in lead acid. Once charged LFP sits at a higher voltage than lead acid - at 13 volts or above until about 80% discharged. A full lead acid, once the surface charge has gone, will sit at around 12.7 volts. So on discharge LFP will go first.

As I said in an earlier post the LFP will indeed extend the life of lead acid in one circumstance which is that you don't routinely use too much capacity of the lead acid. If you have enough of those LFP add-ons and only lightly use the lead acid then all will be well (except your bank balance since those units are incredibly costly) since the LFP will over time bring the lead acid back for that final difficult 20% (i.e. from 80% to 100% state of charge) and this is lead acid heaven. If however you do want to make full use of your lead acid then you will struggle to bring them back to full charge since the LFP will preferentially take the charge and then you still have to find enough absorption time to get the lead acid back up to 100% to avoid sulfation. This is why paralleling lead acid and LFP doesn't work unless there is some form of intervention where they can be charged and discharged separately for some of the time.

Eric Bretscher of Nordkyn design (one of the best sources of information for LFP on boats) covers this. As he says the only advantage of paralleling lead acid is with a small lead acid battery with the sole function of keeping a battery in the system to avoid the inevitable load dump if and when the BMS shuts the LFP down for one of several possible reasons. Scroll down on the link below to find the sub-heading "Alternative 1. Lead-Lithium Hybrid Bank" for further information.

Electrical Design For a Marine Lithium Battery Bank | Nordkyn Design

 

[jaminb]

I am with goeasy on seeing the advantage of having a flying lithium battery that can be used to top up the in built batteries in my case 3 + 1 lead acids for a long sail or a weekend on anchor. The main advantage being leaving the perfectly good system for most of my current sailing untouched.

I asked on another thread if i could connect the lithium to the lead acids with jump leads to top up the system - it was obviously such a stupid question I didn't get a response!

 

[Poey50]

I am with goeasy on seeing the advantage of having a flying lithium battery that can be used to top up the in built batteries in my case 3 + 1 lead acids for a long sail or a weekend on anchor. The main advantage being leaving the perfectly good system for most of my current sailing untouched.

I asked on another thread if i could connect the lithium to the lead acids with jump leads to top up the system - it was obviously such a stupid question I didn't get a response!

The amount of current that will flow if you accidentally short the jump leads will far exceed lead acid. Jump leads wouldn't therefore be a good idea. It would also take a very long time to bring your lead acids up to full charge for the final 20%. It can take an age with a 14.4 volt charger - consider how much longer it would take at around 13 volts. I don't think it's a practical solution.

 

[Pete7]

I am with goeasy on seeing the advantage of having a flying lithium battery that can be used to top up the in built batteries in my case 3 + 1 lead acids for a long sail or a weekend on anchor. The main advantage being leaving the perfectly good system for most of my current sailing untouched.

I asked on another thread if i could connect the lithium to the lead acids with jump leads to top up the system - it was obviously such a stupid question I didn't get a response!

Well you could, but if you are going to do this regularly perhaps use Anderson connectors instead.

 

[Poey50]

Well you could, but if you are going to do this regularly perhaps use Anderson connectors instead.

That helps with the connection problem but not with the massive absorption time problem.

 

[goeasy123]

I am with goeasy on seeing the advantage of having a flying lithium battery that can be used to top up the in built batteries in my case 3 + 1 lead acids for a long sail or a weekend on anchor. The main advantage being leaving the perfectly good system for most of my current sailing untouched.

I asked on another thread if i could connect the lithium to the lead acids with jump leads to top up the system - it was obviously such a stupid question I didn't get a response!

Spot on. To reiterate the requirements, and I think there are a lot of people in this situation. I'm resolved that none of the available powerstations will do it. They do not have a high current 12vdc out. I'd have to build DIY a solution, of which there a many examples on YouTube.

Ideally, I do not want Lithium on the exiting LA load buss. I want a way to charge a small Lithium battery for off-boat purposes.

Optionally, it would be nice to be able to use the Lithium in an emergency if the LA went down. You might have an Anderson connection in the boats buss with an either/or switch so that the LA's and Lithium's (Potential Difference) PD's would never meet each other.

Optionally, it would be nice to be able to charge the LA from the Lithium on the very odd occasion when the other charging sources run out. You could do this with a DC-DC converter on a different high current plug/socket arrangement. Different, so you don't accidentally make the wrong connection.

To charge the Lithium it could sit on the LA buss through a voltage sensitive relay and charge only when the LA was also being charged. It might need a step up of the voltage to get sufficient PD. I think there are MPPT chargers that would do this. You could also size the MPPT to use the boats main PV of have a small dedicated panel.

So the DIY powerstation might be a 100Ah battery with built in BMS, a 3000W/230VAC inverter and an MPPT controller...+ fuses, switches etc. and maybe a few USB outs.

The DC-DC converter and VSR would be wired-in on the boat in convenient places.

What do we think?.... appreciated.

 

[stephen_h]

If the LFP is in parallel connection with the lead acid then I'm not sure how the lead acid takes priority in charging. Are you able to explain how that works?

It is explained here

Charging & Discharging Cycle
With the LE300 hook up, the lead-acid battery is kept fully charged, while the cycle-resistant lithium battery takes on most charging cycles and is preferentially discharged under load. The capacity and the performance of both batteries are used optimally, so you can look forward to a better performance and a longer life span of your batteries.


Longer Battery Lifetime. At Low Costs
The lithium battery takes most of the charging cycles while the lead-acid battery provides inexpensive backup capacity. The lead-acid battery is charged with higher priority, while the lithium battery takes all surplus energy. This process helps to increase the lead-acid battery lifetime to up to ten years.

I don't confess to know HOW it works but that's what they say

 

[Poey50]

It is explained here

Charging & Discharging Cycle
With the LE300 hook up, the lead-acid battery is kept fully charged, while the cycle-resistant lithium battery takes on most charging cycles and is preferentially discharged under load. The capacity and the performance of both batteries are used optimally, so you can look forward to a better performance and a longer life span of your batteries.


Longer Battery Lifetime. At Low Costs
The lithium battery takes most of the charging cycles while the lead-acid battery provides inexpensive backup capacity. The lead-acid battery is charged with higher priority, while the lithium battery takes all surplus energy. This process helps to increase the lead-acid battery lifetime to up to ten years.

I don't confess to know HOW it works but that's what they say

Thank you. The priority of charging and discharging of the the LFP which this mentions is exactly as I described. They furthermore suggest that most cycling is done through the LFP add-ons. Again correct. Then the next section starts by describing the lead acid as an inexpensive back-up! Back-up is true, inexpensive depends on how much you spent on your lead acid bank! Then it says, confusingly, that the lead acid is charged with higher priority having previously correctly said that it is the LFP that is charged first! in reality what would happen is that the lithium would take priority and once full it will have a high voltage disconnect (depending on the disconnect voltage) and the lead acid can then get on with its usual laborious absorption process. It's true that for solar charging the lithium will trickle charge the lead acid overnight but how far this restores the lead acid will depend on the size of the LFP and how deeply discharged the lead acid is. Remember that the solar has preferentially supplied the LFP. As said, imagine how long it would take to trickle charge a 50% discharged lead acid - not too bad to begin with but painfully slow as the voltage difference between the two decreases and the lead acid resistance increases. It would be the same as using a 13 volt charger to bring lead acid to full. The blurb sounds great but I can't imagine they are showing test results. As I've said before, a light use of the lead acid and enough of those pricey LFPs all will be well but this phrase "the capacity and the performance of both batteries are used optimally' is bonkers.

As a rule of thumb, if any company or any individual thinks they have found a brilliant simple solution for using LFP that no-one has thought of before then it's worth asking "am I or they a genius, or am I missing something?"

Edit: I've just read a guide to sizing the pack. It needs to be sized to meet daily power requirements. So it is pretty much doing all the work. The lead acid seems to me to then be mainly acting as a load disconnect buffer and emergency back-up. To optimally use both chemistries they need to be managed separately not connected in parallel.

 

[PaulRainbow]

Thank you. The priority of charging and discharging of the the LFP which this mentions is exactly as I described. They furthermore suggest that most cycling is done through the LFP add-ons. Again correct. Then the next section starts by describing the lead acid as an inexpensive back-up! Back-up is true, inexpensive depends on how much you spent on your lead acid bank! Then it says, confusingly, that the lead acid is charged with higher priority having previously correctly said that it is the LFP that is charged first! in reality what would happen is that the lithium would take priority and once full it will have a high voltage disconnect (depending on the disconnect voltage) and the lead acid can then get on with its usual laborious absorption process. It's true that for solar charging the lithium will trickle charge the lead acid overnight but how far this restores the lead acid will depend on the size of the LFP and how deeply discharged the lead acid is. Remember that the solar has preferentially supplied the LFP. As said, imagine how long it would take to trickle charge a 50% discharged lead acid - not too bad to begin with but painfully slow as the voltage difference between the two decreases and the lead acid resistance increases. It would be the same as using a 13 volt charger to bring lead acid to full. The blurb sounds great but I can't imagine they are showing test results. As I've said before, a light use of the lead acid and enough of those pricey LFPs all will be well but this phrase "the capacity and the performance of both batteries are used optimally' is bonkers.

As a rule of thumb, if any company or any individual thinks they have found a brilliant simple solution for using LFP that no-one has thought of before then it's worth asking "am I or they a genius, or am I missing something?"

Snake oil ?

 

[Poey50]

Snake oil ?

I'd like to see some test results but at £5,200 for 300 ah .... hmm.

 

[goeasy123]

Just a gentle reminder. This thread is about finding a solution that does not integrate Lithium and LA in any form.

Thanks.... still trying to find a solution

 

[PaulRainbow]

Just a gentle reminder. This thread is about finding a solution that does not integrate Lithium and LA in any form.

Thanks.... still trying to find a solution

Looks like you are trying to solve two problems with one solution, which doesn't seem feasible.

You want something like the powerstation for other purposes and as a backup for the boat, i don't see a sensible solution to both with a single device.

If you want more power on the boat, fit another battery, or have an extra, removable battery to take home, or fit some solar etc. Lots of solutions that needn't cost a fortune.

If you want portable power for something else, the powerstation might be the answer, but at a cost. Perhaps if we knew what the other uses might be we could offer more useful suggestions ?