Ideal Drop-in Lifepo4 Battery Purchase Strategy

[SOLAR SUPPORT]

It is important to know the answer to the question of what is the battery capacity needed in an average boat. If you know the LA battery capacity that met your needs in the past, it's a little easy. The Lifepo4 battery with the same capacity will provide you with at least twice the energy capacity.

An other question is: what kind of battery string can be preferred? For example, if there is a need for 400Ah Lifepo4 battery capacity, is it 4X100Ah string or 2x200Ah string or a single 400Ah battery should be preferred?

Lifepo4 batteries sold in the market with prismatic cells have the same dimensions as standard LA batteries and are produced and sold with the same AH capacity. I think this approach is not very good for valuable and limited inner storage capacity on boats.

However, it is especially important for boat owners to take advantage of the low cell volume / energy density advantage that comes with Lithium Technology. Why fill a valuable space with a lower battery capacity while you can store double Lifepo4 cell capacity in the same box?

[Pete7]

Rubbish. A 100Ah lead acid battery holds about 1.2kWh of energy, so does a 100Ah LifePO4 battery.

If a yacht already has battery boxes for a standard form factor, then there is no problem fitting different batteries of any chemistry if they are the same size. In fact far from your statement saying "not very good value" I think its super value being able to replace batteries with another identical size.

What was the real reason for your post? to advertise your business perhaps? If its to help educate the forum members, you are about a decade to late.

Pete

[SOLAR SUPPORT]

Your anger has gone beyond your knowledge. Why are you so angry?

You can use only 0.6 kWh of energy from an average quality LA battery with a capacity of 100 Ah. If you go above this, you will doom your LA battery to die in a short time.

If you had claimed that 1.2kWh energy could be used for the Lifepo4 battery with a capacity of 100 Ah, it could be said to be true.

[Pete7]

Originally Posted by SOLAR SUPPORT

You can use only 0.6 kWh of energy from an average quality LA battery with a capacity of 100 Ah. If you go above this, you will doom your LA battery to die in a short time.

That is an advisory, not a rule which we have discussed in detail before. If you do a search you will find it and benefit by knowing its not a cliff edge and can be exceeded.

Originally Posted by SOLAR SUPPORT

If you had claimed that 1.2kWh energy could be used for the Lifepo4 battery with a capacity of 100 Ah, it could be said to be true.

You haven't made that clear, but I accept you may be writing in a second language so happy to ask for clarification. However, what makes you think there isn't 1.2kWh in a 100Ah LifePO4 battery?

Pete

[SOLAR SUPPORT]

Your claim that "100 Ah LA and 100Ah LifePO4 batteries store the same amount of energy" is ridiculous.

Because if your claim was true, many people would not want to switch to Lifepo4 batteries from LA batteries, which they are not satisfied with. I think you are deviating from the topic in the forum thread by creating an unnecessary discussion. It is useless to store energy that you cannot use.

[Chotu]

What I can tell you is don’t try to market a single battery.

if you need 400 amp hours of power, you don’t want that in one battery in case there is a failure in that battery.

you need to separate it into at least two batteries.

[SOLAR SUPPORT]

Originally Posted by Chotu

What I can tell you is don’t try to market a single battery.

if you need 400 amp hours of power, you don’t want that in one battery in case there is a failure in that battery.

you need to separate it into at least two batteries.

Where did you get that I'm selling 400 Ah batteries? I am not doing a business related with batteries by the way. Opinions are exchanged on the subject, this does not mean that you buy this battery or do not buy this battery. I think that the concern of the people who do this job should not prevent the boat owners from making the right choice.

[s/v Jedi]

I recommend at least two independent batteries, plus a capacity where just one of the two will just be able to keep you going.

Going from 12V 400Ah lead acid to LFP then two 12V batteries of each 200Ah should be good but only if nothing else changes.

If you add solar, switch from cooking with propane to induction etc. you make changes that probably require more battery capacity.

In this 400Ah example and looking at the market for cells, I would then recommend two batteries of each 280Ah using four of the popular 280Ah prismatic cells for each battery.

Last but not least: let go of the Ah value for capacity and switch to kWh which makes much more sense and isn’t affected by choosen voltage. For LFP you calculate capacity as 3.2V per cell times the Ah rating, so for the 12V 280Ah battery it is 4 x 3.2 x 280 = 3.6kWh.

[Chotu]

Originally Posted by SOLAR SUPPORT

Where did you get that I'm selling 400 Ah batteries? I am not doing a business related with batteries by the way. Opinions are exchanged on the subject, this does not mean that you buy this battery or do not buy this battery. I think that the concern of the people who do this job should not prevent the boat owners from making the right choice.

I thought I was answering the question you asked.

[SOLAR SUPPORT]

Originally Posted by Chotu

I thought I was answering the question you asked.

Well, putting all the eggs in one basket is risky, I agree with you.

I think the total Bms capacity is important. In particular, it is necessary to know the electrical power values ​​of devices such as windlass, inverter, bow thruster, electric winch used in the boat. It is necessary to calculate the maximum current that these devices will draw from Lifepo4 batteries and to establish the total bms capacity that can meet this.

I think the total Bms capacity should be at least twice the device requiring the largest current and the Lifepo4 bank should consist of at least two identical batteries connected in parallel.

[sailorboy1]

whats the topic?

For me the ideal drop in purchase startegy was that I had space for 4 G31 batteries so got 4 100ah drop ins

simple!

[Pete7]

Originally Posted by SOLAR SUPPORT

Your claim that "100 Ah LA and 100Ah LifePO4 batteries store the same amount of energy" is ridiculous.

Because if your claim was true, many people would not want to switch to Lifepo4 batteries from LA batteries, which they are not satisfied with.

Your claim that two identical sized batteries don't contain the same amount energy is wrong.

I would suggest that the majority of people using lead acid batteries around the globe are quite happy with their batteries. There are a few other advantages to LFP rather than capacity. If you research the forum you will see what they are using them for.

Pete

[Baronkrak]

So what is the purchase strategy?

[pcmm]

Originally Posted by Pete7

Rubbish. A 100Ah lead acid battery holds about 1.2kWh of energy, so does a 100Ah LifePO4 battery.

If a yacht already has battery boxes for a standard form factor, then there is no problem fitting different batteries of any chemistry if they are the same size. In fact far from your statement saying "not very good value" I think its super value being able to replace batteries with another identical size.

What was the real reason for your post? to advertise your business perhaps? If its to help educate the forum members, you are about a decade to late.

Pete

This is of course incorrect. a 100ah FLA battery can safely only provide at max 50ah. You can actually get 100ah out of a typical LifePO4 battery ( though its really best to take 80-90ah out of it. Regularly getting 100ah out of a FLA is how you end up with users complaining their FLA's only last them a couple of seasons.

The big disadvantage I see with some of the dropin LifePO4 batteries is the BMS's. The cheaper ones often have charging limits half of their discharge. Often you will see a 100amp BMS only having recharge of 50amps. that's not much in a 400ah pack. Plus I think 100Amps is pretty low for most cruisers. Just running your windlass can easily pull 100amps when its working hard.

What is really to be determined is if these LifePO4's really last as long as they say. Which you need in order to get the value out of them for the price.

[Baronkrak]

Originally Posted by pcmm

a 100ah FLA battery can safely only provide at max 50ah.

Originally Posted by Pete7

Rubbish.
Pete

Or in my word, non-sense.