LIFPO4 batteries

[Cerebus]

Tell me to go Google if you like and don’t have time to reply.

I know open lead acid, sealed, Matt, and gel and lithium ion but little of the ones in the title except they used to be really expensive and charge up more quickly perhaps? Do they have s longer longevity? Heavier? Smaller in size?

Anyone care to explain or point me to a good website to read and learn from?

Thank you

 

[geem]

Lighter for the same Ah, smaller, better charge acceptance than lead. Don't need a long absorption time. Don't need to be got to 100% charged on a regular basis, will do thousands of cycles instead of hundreds, without loss of performance. Can be discharged to 20% every time with no ill effects. Better in every way and cheaper than lead for the same usable capacity. Will take huge charge and discharge if installed correctly. I could go on

 

[Cerebus]

Lighter for the same Ah, smaller, better charge acceptance than lead. Don't need a long absorption time. Don't need to be got to 100% charged on a regular basis, will do thousands of cycles instead of hundreds, without loss of performance. Can be discharged to 20% every time with no ill effects. Better in every way and cheaper than lead for the same usable capacity. Will take huge charge and discharge if installed correctly. I could go on

Thanks. They sound super.

Will have to Google.

I know they used to cost €thousands

 

[yoda]

Thanks. They sound super.

Will have to Google.

I know they used to cost €thousands

Look at Fogstar Batteries but then thoroughly investigate how to fit and the system changes required.

 

[Sea Change]

LiFePO4 are a variant of lithium ion. A somewhat lower energy density and much, much safer variant. You'll hear horror stories about fires etc and these always turn out to be one of the more high energy types, which we use every day without thinking about it in phones, laptops, power tools, scooters, even toothbrushes.
So don't let the safety side of things put you off, there's a lot of misinformed people out there.

Having said that, despite being a very safe type of battery, LiFePO4 is still a massive store of energy and needs to be treated with appropriate caution. If you've ever experienced a dead short in a lead acid battery, you'll have an inkling of what can happen. LiFePO4 can deliver much more power than that- thousands of amps. It's like a welding spark. So you need your cables, crimps, fuses, etc to be up to scratch.

Having possibly scared you with that, I will also add that in practice you can't really short out a standard marine lithium battery , because it has a BMS built in to it, which will shut it off if you abuse it in any way- short circuit, reverse polarity, over or under charge, etc etc. It's really quite hard to do them any damage, unless the BMS itself fails, which is a possibility that you have to plan for, hence the correct fuse etc.

Geem has already explained all the benefits of LFP. For anybody who uses their boat a lot, it's really a no brainer. The life cycle cost is far lower than lead acid, and they are much easier to live with.

If you don't use your boat very often, and you plug in to shore power and/or motor a lot, then basic lead acids will probably last you the best part of a decade and it's hard to justify the switch to LFP. It's also, IMHO, not worth switching away from lead acid for anything that only needs a burst of high current output- engine starter, windlass, bow thruster.

There are a few things to bear in mind when switching to LFP, but there's plenty of experience on the forum to help you

 

[Chris_Robb]

Lead acid is slow to charge, and as it gets full it gets even slower.
LiFePO4 is almost the opposite. Its a bit like a dog - It will eat all it can get.

There is therefore a bit of a dilemma when it comes to charging. If you have a nice automotive 110 amp charger, when you start the engine - it may well deliver 110 amps until full - thanks will very quickly melt the starter motor. You have to consider how your are going to charge the batteries as with standard Automotive alternators you will have to keep the output down so that the alternator can keep going. Also you may need to ventilate the alternator as in the Med it can get very hot in an engine room. So if you are looking for more amps to use, just remember you have to have a method to get it in..

The main basis for charging is of course Solar -

So don't think its just lead acid on steroids... I have now left the world of sailing in Greece so have not advanced my knowledge on this matter further.

Remember that the first part of a new system design is how you are going to conserve and not waste energy. I had a Westerly Oceanlord with a highly inefficient insulation. I ripped it out and installed my own 100 ltr fridge design with 4 -to 5 inches of insulation all round and an efficient keel cooler. With 2 x 86 watt output - I never needed to run the engine to keep the batteries up. I therefore didn't need to go the Lithium root.... and we were not Marina based so no shore power.

No doubt all these issue have been sorted with electronics - but that will not solve the continuous output problems you will have getting the output need to charge a very large capacity battery.....

 

[geem]

Lead acid is slow to charge, and as it gets full it gets even slower.
LiFePO4 is almost the opposite. Its a bit like a dog - It will eat all it can get.

There is therefore a bit of a dilemma when it comes to charging. If you have a nice automotive 110 amp charger, when you start the engine - it may well deliver 110 amps until full - thanks will very quickly melt the starter motor. You have to consider how your are going to charge the batteries as with standard Automotive alternators you will have to keep the output down so that the alternator can keep going. Also you may need to ventilate the alternator as in the Med it can get very hot in an engine room. So if you are looking for more amps to use, just remember you have to have a method to get it in..

The main basis for charging is of course Solar -

So don't think its just lead acid on steroids... I have now left the world of sailing in Greece so have not advanced my knowledge on this matter further.

Remember that the first part of a new system design is how you are going to conserve and not waste energy. I had a Westerly Oceanlord with a highly inefficient insulation. I ripped it out and installed my own 100 ltr fridge design with 4 -to 5 inches of insulation all round and an efficient keel cooler. With 2 x 86 watt output - I never needed to run the engine to keep the batteries up. I therefore didn't need to go the Lithium root.... and we were not Marina based so no shore power.

No doubt all these issue have been sorted with electronics - but that will not solve the continuous output problems you will have getting the output need to charge a very large capacity battery.....

Solar panels have improved in efficiency. I just removed 4x180w p-type solar panels and replaced them with 4x250w n-type bifacial panels. The newer panels are only marginally larger than my 7 year old 180w panels. The performance differences is very noticeable. With the addition of 3x100w 24v panels, we are seeing over 65A @12v peak output in the weak UK sunshine. Yesterday we harvested over 5kWh.
The difference with lithium is that you can have full output of your solar all day. How many times have a heard people say'my lead batteries are on float by lunchtime'. Well if you had lithium batteries, you could be harvesting solar power for the other half of the day as well. This gives you the opportunity to run electrical appliances you could previously only dream of.

 

[Chris_Robb]

Solar panels have improved in efficiency. I just removed 4x180w p-type solar panels and replaced them with 4x250w n-type bifacial panels. The newer panels are only marginally larger than my 7 year old 180w panels. The performance differences is very noticeable. With the addition of 3x100w 24v panels, we are seeing over 65A @12v peak output in the weak UK sunshine. Yesterday we harvested over 5kWh.
The difference with lithium is that you can have full output of your solar all day. How many times have a heard people say'my lead batteries are on float by lunchtime'. Well if you had lithium batteries, you could be harvesting solar power for the other half of the day as well. This gives you the opportunity to run electrical appliances you could previously only dream of.

Our panels were 2008 vintage - and gave tops of 9amps at 14 volts. I take it that people do NOT try to get significant charge from their engine? ie you have to route it through a good old lead acid to avoid the over use of the alternator?
Some post just refer to Lithium batteries - I really hope no one is using them!

 

[chris-s]

Our panels were 2008 vintage - and gave tops of 9amps at 14 volts. I take it that people do NOT try to get significant charge from their engine? ie you have to route it through a good old lead acid to avoid the over use of the alternator?
Some post just refer to Lithium batteries - I really hope no one is using them!

Typically a dc-dc charger off the alternator/lead acid battery in one form or another’s But, as you allude to, I have seen more than a few posts on FB suggesting it is absolutely fine to just drop in a lithium and rely on the bms to look after things. Quite how that ‘looks after’ the alternator I’m not sure.

 

[geem]

Our panels were 2008 vintage - and gave tops of 9amps at 14 volts. I take it that people do NOT try to get significant charge from their engine? ie you have to route it through a good old lead acid to avoid the over use of the alternator?
Some post just refer to Lithium batteries - I really hope no one is using them!

You can go for direct charging using Balmar, mastervolt, etc externally regulated alternators. These can potentially put in a lot of current but you are burning fossil fuels to do so. Most people opt for a dc/dc chargers that will put in 50% of the alternator output on a continual basis whilst the engine is running. If you motor for a few hours you are likely going to put in way more amps than you ever did with lead batteries.
Solar is so cheap these days it makes sense to max it out and get free power

 

[Chiara’s slave]

We’d love to do this but are outboard powered. Could we just intercept the outboard start/charge cables, put in a motorbike size lead acid battery and a dc-dc charger? Our solar goes straight to the existing batteries. They weigh nearly 40kg between them. We could lose some weight and have more usable capacity.

 

[Sea Change]

You don't *have* to have alternator charging. We did without it for years, but in a sunny place with a lot of solar. And we could run the vital stuff off the starter battery.

 

[geem]

We’d love to do this but are outboard powered. Could we just intercept the outboard start/charge cables, put in a motorbike size lead acid battery and a dc-dc charger? Our solar goes straight to the existing batteries. They weigh nearly 40kg between them. We could lose some weight and have more usable capacity.

I don't see why that would not work if you outboard motors have enough output. You wouldn't want a DC/DC charger rated higher than your outboard can supply. If it was too big, then DC/DC charger would cycle on and off as the engine battery voltage dropped then climbed

 

[Chiara’s slave]

It’s 150 watts, 12 amps. We don’t do a great deal of motoring, really 15 mins each way in and out of harbour. Having a Code 0 has transformed our light wind sailing, not that it was bad before. We currently have 150 watts of solar, but could probably fit in 4 more 100w panels if we felt the need to be completely OTT. I shall have a poke around the cables. We could fit a 12 amp hour bike battery in a hand locker. And as it’s a 300cc twin, I doubt that it needs more.

 

[geem]

It’s 150 watts, 12 amps. We don’t do a great deal of motoring, really 15 mins each way in and out of harbour. Having a Code 0 has transformed our light wind sailing, not that it was bad before. We currently have 150 watts of solar, but could probably fit in 4 more 100w panels if we felt the need to be completely OTT. I shall have a poke around the cables. We could fit a 12 amp hour bike battery in a hand locker. And as it’s a 300cc twin, I doubt that it needs more.

It's probably not worth charging from the engine for so little output. You may also struggle to find a DC/DC charger smaller than 12A. More solar would probably be the best option. Maybe a couple of 200W bifacial panels would make quite a difference.

 

[Chiara’s slave]

It's probably not worth charging from the engine for so little output. You may also struggle to find a DC/DC charger smaller than 12A. More solar would probably be the best option. Maybe a couple of 200W bifacial panels would make quite a difference.

The space we have for panels is long and narrow. On the amas. But I have a source of 100w panels that fit that space. It’s a question of balancing the battery capacity and solar output, having enough output on uk gloomy days, and enough battery to last the odd day with almost nothing. We have a fridge, 6 amps, and a diesel heater, plus the normal navigation, lighting etc. We’ll never have an induction hob, but never say never to electric propulsion with more batteries

 

[Chris_Robb]

The space we have for panels is long and narrow. On the amas. But I have a source of 100w panels that fit that space. It’s a question of balancing the battery capacity and solar output, having enough output on uk gloomy days, and enough battery to last the odd day with almost nothing. We have a fridge, 6 amps, and a diesel heater, plus the normal navigation, lighting etc. We’ll never have an induction hob, but never say never to electric propulsion with more batteries

What kind of fridge do you have. 6 amps is extortionate for a small compressor fridge, it must be the compressorless type. Portable fridge?

These are just not suited to use off the grid.

 

[Chiara’s slave]

What kind of fridge do you have. 6 amps is extortionate for a small compressor fridge, it must be the compressorless type. Portable fridge?

These are just not suited to use off the grid.

6 amps is startup from ambient. Just as the diesel heater starts up at about 10, max fan, max fuel pump and glo plug. A worst case scenario.