How do I charge Lifepo4 with normal alternator?

LinusR

New Member
Joined
May 30, 2022
Messages
3
This has probably been discussed already here, but I have a hard time finding it...

I´m building my first ever Lifepo4 batteries I´m going to use them in my boat, I ordered 16cells 320ah and I´m building 2x24v batteries, and paralell connect them.
but how can I charge them with my normal engine alternators? I have friend how built one 24v 280ah battery using Daly BMS 120A and he has been running his system for a year now without any problems but he did not do any modifications he only replaced his old AGM batteries with this lifepo4 and Daly BMS...

From what I understan the alternator should burn up if doing like that?

I also have shore power and I have a mastervolt mass 24/100c charger connected to that, can I use that same charger to charge these Lifepo4 batteries?
I will be adding solar panels later to this same system.
 
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LinusR

New Member
Joined
May 30, 2022
Messages
3
So if I need to get a Dc/dc charger how many amps should I go for? How long would it take to charge my Lifepo4 batteries?

2 x 320ah lifepo4 is alot of power, and I'm using a 2500w inverter for making coffee a few times per day and a toaster, I might some days use a Kettle. Other than that it's mostly the 24volt refridgerator that wil be running 24/7 some Led lights will be uset when dark outside.

So I'm thinking maby a victron energy 24/24-17amp would be enough? That way I could charge at least a little without frying the alternator, driving back home after a few days at anchor...
And then charge up at dock with shore power?

Would my Mastervolt MASS 24/100-C work?
Can't find anything about it in users manual?
 

jberger

Solar Addict
Joined
Jun 1, 2021
Messages
303
FWIW, I charge a 12V, 1200ah pack from an alternator without any issues, so it's not a problem as long as you take some time to set it up.

Do you already have alternator control on your setup? (Balmar, Wakespeed, etc)

The alternator charging issues can be solved, it's really 3 main issues to watch for
1) You need some form of alternator protection to keep a sudden BMS trip (power off) from causing a destructive surge on the alternator.
You can use a simple protector like the Balmar AMP-12, to protect the alternator side. https://balmar.net/balmar-releases-new-alternator-protection-module/

2) You need to be able to control the charging rate going into the pack so you don't exceed the C rate of the pack when charging.
You can do this by building a pack who's C rate matches your typical alternator output, regulate the alternator output using a controller (Balmar, Wakespeed, etc), install a DC/DC charger that will ensure the alternator's output is regulated to match the pack.
In most marine applications, the controller makes sense as you already need to adjust for belt wear, temps, etc. And a modern controller will include all of the needed controls plus protect the alternator from rapid disconnect in #1

3) The alternator itself needs to be rated for continuous output.
Lots of marine engines already use a rewound small frame alternator that can handle continuous output, so this isn't a problem. But if your setup uses a small frame that is only built for automotive use, you can burn it up when charging large banks, regardless if they are lead acid or LFP.
Small case units are really built to quickly replace the energy lost in cranking and then provide additional current for lights, etc. So if you throw a full load on that small case and run it for hours, it will simply overheat, melt the insulators and burn up. Make sure it's rated for your use, and Balmar, etc have those marine grade units if you decide to replace.

You will also need to raise your alternator's output to match the charging voltage of the new pack, usually done on the regulator or controller.
You might also want to check out cruisers forum, they have a good amount of marine users who are doing this stuff and have it all worked out.
 

LinusR

New Member
Joined
May 30, 2022
Messages
3
FWIW, I charge a 12V, 1200ah pack from an alternator without any issues, so it's not a problem as long as you take some time to set it up.

Do you already have alternator control on your setup? (Balmar, Wakespeed, etc)

The alternator charging issues can be solved, it's really 3 main issues to watch for
1) You need some form of alternator protection to keep a sudden BMS trip (power off) from causing a destructive surge on the alternator.
You can use a simple protector like the Balmar AMP-12, to protect the alternator side. https://balmar.net/balmar-releases-new-alternator-protection-module/

2) You need to be able to control the charging rate going into the pack so you don't exceed the C rate of the pack when charging.
You can do this by building a pack who's C rate matches your typical alternator output, regulate the alternator output using a controller (Balmar, Wakespeed, etc), install a DC/DC charger that will ensure the alternator's output is regulated to match the pack.
In most marine applications, the controller makes sense as you already need to adjust for belt wear, temps, etc. And a modern controller will include all of the needed controls plus protect the alternator from rapid disconnect in #1

3) The alternator itself needs to be rated for continuous output.
Lots of marine engines already use a rewound small frame alternator that can handle continuous output, so this isn't a problem. But if your setup uses a small frame that is only built for automotive use, you can burn it up when charging large banks, regardless if they are lead acid or LFP.
Small case units are really built to quickly replace the energy lost in cranking and then provide additional current for lights, etc. So if you throw a full load on that small case and run it for hours, it will simply overheat, melt the insulators and burn up. Make sure it's rated for your use, and Balmar, etc have those marine grade units if you decide to replace.

You will also need to raise your alternator's output to match the charging voltage of the new pack, usually done on the regulator or controller.
You might also want to check out cruisers forum, they have a good amount of marine users who are doing this stuff and have it all worked out.
Thank you, I have to check that, I do not know what I have, I know I have 2 marine diesels they are Volvo Penta TAMD60B and the OEM alternators should be 60A each.... I did notice that they are both alternator same looking but on the other one there is a smal "black box" that the other one don't have
 
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