DIY LiFePo4 installation - Don't do what I did (maybe) . . .

[rotrax]

Was in a hurry, so i forgot to do the sums from the panel voltage to the reduction to charging voltage. Needs 14V+ to charge (not 12V) (slightly picky, i know). So, a 150W would be max for the 10A current, yet Bluetti state 500W max ???? Maybe they forgot do do the sums too

I think the 500W might be of the 'Turbo Boost' 220V input. That is quick, but noisy with the fan running.

 

[PaulRainbow]

I think the 500W might be of the 'Turbo Boost' 220V input. That is quick, but noisy with the fan running.

No, spec says 500W Max., VOC 12-60VDC, 10A

So you could fit (for instance) 2 x 150W panels in series, max 38V (fitting 3 would be too close to the 60V limit, see warning below). That gives you 8.6A max @ 38V max. If it's charging at 14V you should be getting about 23A.

You just need to find the best combination that will not exceed 500W, 60V or 10A.

Warning: The open circuit voltage of solar panels cannot exceed 60V, otherwise it will
damage the device(Note:It’s not covered in the warranty

 

[Sea Change]

I wonder if there's a common component limiting all charge sources to 10A?
Does it say anything about charging from different sources simultaneously?

 

[lustyd]

If it's charging at 14V

We did decide the batteries were about 30V though, based on the spec sheet so perhaps it does all make sense behind the scenes.

 

[PaulRainbow]

I wonder if there's a common component limiting all charge sources to 10A?
Does it say anything about charging from different sources simultaneously?

Just checked, can't simultaneously charge with solar and DC, they use the same input port. Can use one or the other, plus AC. So as i mentioned earlier, it's suggested (on forums) to use an inverter to charge from onboard DC if you want to use both.

 

[PaulRainbow]

We did decide the batteries were about 30V though, based on the spec sheet so perhaps it does all make sense behind the scenes.

I think it was guessed that might be the case, but it also might be an error in their specs. Charging a 30V battery with a 12V solar panel is going to be a bit feeble.

 

[RunAgroundHard]

... My guess here is that insurance companies don't know (or probably care so much) about the technical details. Their reason for wanting a professional installation is that a professional installer is someone for the boat insurer to go after to recover any losses ...

I assume that is not the case and they do know to a degree, hence apply a control, professional installation. Insurance companies do not want to be too prescriptive around standards and chasing their tails all the time rewording policies because standards change i.e. they don't specify the material; standard for rigging wire. It is more efficient for them to be less prescriptive. Asking for professional modification to the boat in an area that they think is high risk is simply a risk reduction requirement by them. Perhaps one day, when "lithium" becomes routine and normalised, such restrictions as professional installation will no longer feature and that lithium iron phosphate (LiFePO4) will be accepted as a low risk.

 

[Sea Change]

Just checked, can't simultaneously charge with solar and DC, they use the same input port. Can use one or the other, plus AC. So as i mentioned earlier, it's suggested (on forums) to use an inverter to charge from onboard DC if you want to use both.

I guess it's got some sort of combined MPPT/DC-DC charger inside. I know Renogy sell those as standalone units. Makes sense in some respects as you're reusing the same transformers. But also rather limiting in how you can use it.

At £6/Ah (vs the £1.30/Ah my DIY batteries cost me four years ago) you'd better be very happy that the extra gizmos in the box are going to do what you need.

 

[migs]

I agree with the comments in this thread about insurers not caring about technical details, and that is because they shouldn’t have to. Insurers are used to dealing with highly professional industries such as medical and aviation, where rigorous training, specific qualifications / certification and tightly specified standards are a given. They are simply not used to dealing with unregulated businesses such as small boat repair shops…

As for standards, my understanding is that PD CEN ISO/TS 23625:2025 makes no reference to LiFePO₄ batteries at all... If UK official boat standards bodies can’t, or won’t spell out best practice, I dread to think what insurers think of the leisure craft industry.

 

[migs]

The Bluetti charging circuit sounds similar to Torqueedo’s; this accepts up to 24V and 4A, so I use a cheap 12V/24V converter to double the charge speed compared with 12V.

You could use a 12V/48V converter to charge the Bluetti at 480W. It would draw 40A from the boat, so you'll need something like an Anderson connector to handle the current.

Or you could simply use your inverter...

 

[rotrax]

I guess it's got some sort of combined MPPT/DC-DC charger inside. I know Renogy sell those as standalone units. Makes sense in some respects as you're reusing the same transformers. But also rather limiting in how you can use it.

At £6/Ah (vs the £1.30/Ah my DIY batteries cost me four years ago) you'd better be very happy that the extra gizmos in the box are going to do what you need.

But you cant take yours to your sons detached garage without power and drill large holes in thick concrete to fit security for his motorbikes, or stick it and the Dometic fridge in the car on a hot day so you have cold drinks.

As we have agreed, it is very flexible.

It was worth a punt, I shant lose much if it turns out to be NBG on the boat, I shall stick it on ebay!

As I said earlier, I cant be arsed to make one. If I did, it would not compare in size, weight and no doubt ease of use and simple digital readout showing status.

I am impressed so far with its quality.

 

[PaulRainbow]

I agree with the comments in this thread about insurers not caring about technical details, and that is because they shouldn’t have to. Insurers are used to dealing with highly professional industries such as medical and aviation, where rigorous training, specific qualifications / certification and tightly specified standards are a given. They are simply not used to dealing with unregulated businesses such as small boat repair shops…

As for standards, my understanding is that PD CEN ISO/TS 23625:2025 makes no reference to LiFePO₄ batteries at all... If UK official boat standards bodies can’t, or won’t spell out best practice, I dread to think what insurers think of the leisure craft industry.

I think you will find that it does.

Edit: It is PD ISO/TS 13297 that currently has no mention of Lithium (LiFePO4 or otherwise). ISO 13297-3 is under development and will cover Lithium-ion

 

[migs]

You are quite correct, I was looking at an older version of the standard.

In the public domain from Google:

'While the standard covers all lithium-ion batteries, it is particularly relevant to LiFePO4 batteries due to their increasing popularity in small craft applications'

'Safety: LiFePO4 batteries are known for their high safety profile'

Yes indeed, LiFePO4 does get a mention; but why don't they say that currently only LiFePO4 batteries are suitable for boat house batteries (until something better comes along).

 

[PaulRainbow]

You are quite correct, I was looking at an older version of the standard.

In the public domain from Google:

'While the standard covers all lithium-ion batteries, it is particularly relevant to LiFePO4 batteries due to their increasing popularity in small craft applications'

'Safety: LiFePO4 batteries are known for their high safety profile'

Yes indeed, LiFePO4 does get a mention; but why don't they say that currently only LiFePO4 batteries are suitable for boat house batteries (until something better comes along).

Not sure if you are mixing standards up (just edited post #152)

PD ISO/TS 13297 that currently has no mention of Lithium (LiFePO4 or otherwise). ISO 13297-3 is under development and will cover Lithium-ion

ISO 23625:2025 is for Small craft — Lithium-ion batteries

ISO 23625:2025 was only published this month.

 

[migs]

Now I am confused. Why are there two different standards (ISO 23625:2025 & ISO 13297-3), both covering the same subject?

 

[lustyd]

I think it was guessed that might be the case, but it also might be an error in their specs. Charging a 30V battery with a 12V solar panel is going to be a bit feeble.

My assumption was that the 500W panels would be higher voltage. All based on their crazy spec sheet and I agree it’s more likely the spec sheet is wrong but in theory higher voltage would allow for the 10A limit if we were really trying to believe their specs

 

[lustyd]

Now I am confused. Why are there two different standards (ISO 23625:2025 & ISO 13297-3), both covering the same subject?

 

[PaulRainbow]

Now I am confused. Why are there two different standards (ISO 23625:2025 & ISO 13297-3), both covering the same subject?

ISO 13297 is titled "Small craft - Electrical systems - Alternating and direct current installations "

"This document specifies the requirements for the design, construction and installation of the following
types of DC and AC electrical systems, installed on small craft either individually or in combination:
a) extra-low-voltage direct current (DC) electrical systems that operate at nominal potentials of
50 V DC or less;
b) single-phase alternating current (AC) systems that operate at a nominal voltage not exceeding
AC 250 V.
This document does not cover the following:
— electrical propulsion systems of direct current less than 1 500 V DC, single-phase alternating
current up to 1 000 V AC, and three-phase alternating current up to 1 00 V AC, which are addressed
by ISO 16315;
— any conductor that is part of an outboard engine assembly and that does not extend beyond the
outboard engine manufacturers supplied cowling;
— three-phase AC installations that operate at a nominal voltage not exceeding 500 V AC, which are
addressed by IEC 60092-507"

There is currently no mention of Lithium batteries in this document. ISO 13297-3 is an amendment, currently in development. Looking at the latest information for this, it seems that it relates to charging batteries on electric propulsion boats, so probably not relevant to this thread.

ISO 23625:2025 is titled "Small craft — Lithium-ion batteries"

"This document provides requirements and recommendations for the selection and installation of
lithium-ion batteries for boats. It applies to lithium-ion batteries and to battery systems with a capacity
greater than 600 Wh, installed on small craft for providing power for general electrical loads and/or to
electric propulsion systems. It is primarily intended for manufacturers and battery installers."

It is rather odd that they put the standards for electric boats in with the general electrical standard, but have a separate standard for LifePO4 in general use. Seems backwards to me.

 

[PaulRainbow]

My assumption was that the 500W panels would be higher voltage. All based on their crazy spec sheet and I agree it’s more likely the spec sheet is wrong but in theory higher voltage would allow for the 10A limit if we were really trying to believe their specs

Yes, higher volts is the answer for better charging, see #142.

As for their specs...........

 

[RogerJolly]

ISO 13297 is titled "Small craft - Electrical systems - Alternating and direct current installations "
...

ISO 23625:2025 is titled "Small craft — Lithium-ion batteries"

Just wondering: Do all new boat designs have to be approved against Recreational Craft Regulations (RCR)? Would that include conforming to these standards?

Are there any boat builders using LifePO4 lithium as standard in new builds?