My lithium build

[lustyd]

https://www.fire.tc.faa.gov/pdf/TC-16-17.pdf

You read that report very differently to the rest of us. To me, it says they purposefully tortured the LiFePo4 cells and still didn't manage to get a fire to propagate, or even a temperature higher than a domestic oven. Such tests are all over YouTube and are the reason we're all so confident in the relative safety of these even when compared to LA batteries which can and often do explode and catch fire.

 

[lustyd]

They're for attaching to a spray hood normally so a nice soft bit of canvas in between - though in the last two years I've been using them I've had no problems reported but thanks for the warning

I looked at the link too late, I was wrong and edited my post to reflect that In theory the magnet could still shatter but looks like the steel will protect it nicely.

 

[Poey50]

Slight thread drift here: in the midst of all the myths and apocryphal tales I've heard that it's not a good idea to use a LifePo4 for engine starting. I'm building a B2B with Lead Acid so not planning to do so; but if my LA flattens for some reason would it hurt to start with the LFP and switch back to LA straight away? I assume that the alternator will be ok as it will have something to charge (LA) all the time and the switch away from LFP can be done as the engine fires, so not much charge at that time anyway.

TBH I can't see why the LFP wouldn't be good as a starter; the power draw should be no more than for LA and it's not for that long. Am I missing something (internal resistance etc)? NOT PLANNING ON IT - JUST CURIOUS

You can use LFP to start an engine as long as the BMS can take the current draw. I have a three switch system that allows me to start the engine with the LFP in an emergency. The main points about not using LFP for dedicated engine start (other than the current limitations) is a) that it is a waste of capacity - and therefore money- since only a fraction of an amp-hour is needed and b) the higher reliability of lead acid which is more abuse-tolerant.

 

[geem]

Can you spot when we started using lithium

 

[vas]

Can you spot when we started using lithium

28th
what happened on the 30th? just bad weather?

 

[geem]

28th
what happened on the 30th? just bad weather?

No. I had the solar disconnected whilst I was doing some rewire. Is a pain trying to redesign and rewire whilst you are actually living onboard and running all the systems. I needed quite a bit of temporary wiring whilst I set up the whole system. Adding two more B2Bs and a smart shunt, and relocating the existing MPPTs and battery balancers meant there was still some downtime.
We are now seeing on average, a doubling of our solar harvest on lithium. That bit was a real surprise

 

[noelex]

Before the lithium conversion the lead acid batteries were on float (ie full) for several hours. You must therefore be using more electrical energy (or fewer generator hours) after the conversion and this is reflected in the graph.

The only gain that should be seen is when charging the lead acid batteries during the absorption phase where the higher acceptance rate of lithium is an advantage, but the graph shows this is only a short time (less than an hour ?) in your system).

Lithium batteries are slightly more efficient than lead acid. More of the energy that is put onto the battery can be extracted, but this would result in a lower not a higher solar harvest if the energy consumption was constant.

 

[geem]

Before the lithium conversion the lead acid batteries were on float (ie full) for several hours. You must therefore be using more electrical energy (or fewer generator hours) after the conversion and this is reflected in the graph.

The only gain that should be seen is when charging the lead acid batteries during the absorption phase where the higher acceptance rate of lithium is an advantage, but the graph shows this is only a short time (less than an hour ?) in your system).

Lithium batteries are slightly more efficient than lead acid. More of the energy that is put onto the battery can be extracted, but this would result in a lower not a higher solar harvest if the energy consumption was constant.

We are not having to run the generator to make water. We never ran the watermaker with lead batteries as they don't like the high load. They get hot in the Tropics and it shortens their life.
We are using the induction hob off the lithium. Again, we didn't do this off lead batteries. We are also using the immersion heater to heat hot water. Being able to run high loads from the lithium is the key. We have never used our 3kw inverter so much.
If we used the lead batteries the same way as we are using the lithium, the battery temperatures would sky rocket. Constant charge and discharge would bring the lead battery temperature up in to the mid 30s very quickly. We are not seeing that with the lithium.

It's interesting how hot the mosfets get on the BMS. Continual high loads on drop in replacement batteries would see a hot spot within the battery case with no way of ventilating the sealed box. I don't know if this causes a problem long term. It's just an observation. I am running mechanical ventilation 24/7 with good air flow across the BMS. This isn't causing any heat to the lithium cells

 

[noelex]

We are not having to run the generator to make water. We never ran the watermaker with lead batteries as they don't like the high load. They get hot in the Tropics and it shortens their life.
We are using the induction hob off the lithium. Again, we didn't do this off lead batteries. We are also using the immersion heater to heat hot water. Being able to run high loads from the lithium is the key. We have never used our 3kw inverter so much.
If we used the lead batteries the same way as we are using the lithium, the battery temperatures would sky rocket. Constant charge and discharge would bring the lead battery temperature up in to the mid 30s very quickly. We are not seeing that with the lithium.

The higher consumption explains the higher solar yield.

It is great to be able to run the water makers, hot water, electric cooking, washing machine etc from the batteries using solar power. This is possible with lead acid batteries, providing you have a appropriatly sized bank, good quality installation, and are producing enough solar energy, but it is easier with lithium.

 

[vas]

you'll soon realise you hardly need the generator - well, you will for cooking in the long term on bad days, but gen hours will be a small fraction of what they used to be. Hope the inverter is good quality kit cause it will be often used at 2/3 of its full capacity.

 

[Kelpie]

We are not having to run the generator to make water. We never ran the watermaker with lead batteries as they don't like the high load. They get hot in the Tropics and it shortens their life.
We are using the induction hob off the lithium. Again, we didn't do this off lead batteries. We are also using the immersion heater to heat hot water. Being able to run high loads from the lithium is the key. We have never used our 3kw inverter so much.
If we used the lead batteries the same way as we are using the lithium, the battery temperatures would sky rocket. Constant charge and discharge would bring the lead battery temperature up in to the mid 30s very quickly. We are not seeing that with the lithium.

It's interesting how hot the mosfets get on the BMS. Continual high loads on drop in replacement batteries would see a hot spot within the battery case with no way of ventilating the sealed box. I don't know if this causes a problem long term. It's just an observation. I am running mechanical ventilation 24/7 with good air flow across the BMS. This isn't causing any heat to the lithium cells

Great to hear that it's working out so well.
I agree about the heat on the MOSFETs. My first BMS was a 120A JBD. It could get really hot- over 55⁰C. I've swapped it out for a 200A model which has a proper heat sink. Haven't seen over 40⁰, which is much more reasonable.

 

[gregcope]

@Kelpie Which 200A BMS did you go with?

 

[Kelpie]

@Kelpie Which 200A BMS did you go with?

JBD in both cases.
I was originally going to have the inverter bypass the BMS via a relay but in the end just kept it simple.
The design of the 200A unit is significantly more robust than the 120A. A worthwhile upgrade and worth the extra ~£40.

 

[geem]

you'll soon realise you hardly need the generator - well, you will for cooking in the long term on bad days, but gen hours will be a small fraction of what they used to be. Hope the inverter is good quality kit cause it will be often used at 2/3 of its full capacity.

The inverter is a low frequency unit and a knock off of a Sterling unit. 3000w but will take a lot more for short duration. It weighs 26kg. A big transformer in there. 12V solar panels charging kits for caravans, motorhomes, boats, yachts, marine

 

[Trident]

The inverter is a low frequency unit and a knock off of a Sterling unit. 3000w but will take a lot more for short duration. It weighs 26kg. A big transformer in there. 12V solar panels charging kits for caravans, motorhomes, boats, yachts, marine

That's a very good inverter - I had the same one for 4 years of continual use and only changed to a Vicron for ease of repair in far flung places. Not to be too pedantic but I'm pretty sure Sterling originally just rebranded these rather than these being a knock off of Sterling.

 

[geem]

Up date on my lithium build.
Although my lithium battery box is dedicated to the lithium battery with no other battery or anything else in there, I have added some protection again shorts and chafe. The risk of chafe on the battery lead between the positive battery terminal and class T fuse was small. I routed the wire such that there was minimal risk of chafe. However, I have now shortened the wire and sleeved it such that chafe can't happen. This is now fully compliant with ABYC standards. In addition, to reduce the risk of a spanner, etc being dropped across the cell terminals when the perpex battery box lid is off, I have added a second perspex shield to the cells. This sits 30mm above the cells so I still get good ventilation. I also had 5 ring terminals on the positive battery connection. ABYC states no more than 4, so I have rerouted the fused power supply for the ventilation fan to the main Busbar rather than the lithium battery terminal
Edit: I still need to seal the hole up where the battery cables pass through. Need a tube of sealant and I need to wrap the cables before I seal the hole

 

[Poey50]

Up date on my lithium build.
Although my lithium battery box is dedicated to the lithium battery with no other battery or anything else in there, I have added some protection again shorts and chafe. The risk of chafe on the battery lead between the positive battery terminal and class T fuse was small. I routed the wire such that there was minimal risk of chafe. However, I have now shortened the wire and sleeved it such that chafe can't happen. This is now fully compliant with ABYC standards. In addition, to reduce the risk of a spanner, etc being dropped across the cell terminals when the perpex battery box lid is off, I have added a second perspex shield to the cells. This sits 30mm above the cells so I still get good ventilation. I also had 5 ring terminals on the positive battery connection. ABYC states no more than 4, so I have rerouted the fused power supply for the ventilation fan to the main Busbar rather than the lithium battery terminal
Edit: I still need to seal the hole up where the battery cables pass through. Need a tube of sealant and I need to wrap the cables before I seal the hole

View attachment 157623

Good to see high standards being followed. The ABYC and ISO aren't there to make life difficult as some seem to think.

 

[gregcope]

Looks good.

Whats the smaller black connector next to the main negative, top right?

Also, and I might have missed it, but is there a link to the ABC standards?

 

[geem]

The black connector is for the display for the JK BMS
I didn't post the ABYC standard