Charging lipo with AGM settings

[SVSeaHawk]

With lipo4 prices plummeting like a Coney Island roller coaster, my 2yo ~1000ah AGM house bank could be replaced for around $3K with lithium batteries reviewers (Will Prowse) seem to like (Redodo 12V 100Ah LiFePO4 w/ 100A BMS) for about $269.99 -10% on Amazon.

Double usable amp hours, better charging rate, longer life, takes less space - a great deal IF I don’t need to upgrade my older charger/inverter when I make the switch.

I have a Mastervolt Mass Combi 12/2500-100 which does not have a separate lipo charge setting. I have heard people saying the AGM charge settings are fine but I find this doubtful.

The Mastervolt AGM charge setting I’m using now
Bulk 14.4/ Absorb 14.25/ Float 13.8

The newer master volt unit (12/3000 - 160) charges lipo at
Bulk 14.25 / Absorb 14.25 / Float 13.5

My question is would the higher bulk and lower float settings damage new lipo batteries?

The Redodo batteries call for Charge Voltage: 14.4V±0.2V so I don’t see that as an issue.

I don’t know what a lower float number means in practical terms. It would seem if the battery never comes to absolute full charge, that could be a problem or a benefit in terms of longevity.

There are other things to consider of course, wind gen. / alternator, but right now I’m focusing on the inverter/charger and if I need to replace it or not. Anyone with thoughts to offer?

[sailingharry]

Those bulk/charge numbers should work great. The battery specs seem to be tolerant of 14.6, so your 14.4 should not be a problem.

Float should actually be pretty good. Eventually, your charge level will go down some, but LFP like that. I have not yet gone to lithium, but I suspect that if I do I will set all of my high power charge sources (alternator and shore charger) at a slightly lower voltage than full. This will allow the solar to bring them up to full and hold them there during the day, and then allow them to drift down overnight even when on shore power. You haven't mentioned your solar, but if at least one of your solar chargers is adjustable, you can make that the one that gives you a periodic full charge.

[SV Confianza]

The problem is usually that the LFP will charge very slowly, since the charge current dramatically decreases when it goes into absorption. The manual for your charger says that it goes into absorption once it sees 14.4v.

Now, I'm going to do some guessing, but with 1000ah of lithium, and if you have your batteries in parallel with bus bars (all cables the same length as well) rather than just daisy chained, the charger amps won't have such a huge influence on the bus voltage, compared to, say, only 200ah. That means you'll likely get a pretty good charge before it hits absorption.

It's a bit of a guess though without testing it in real life.

My victron is set to charge at 14.6 with basically no absorption or float, for comparison.

If it doesn't really matter if your batteries take long to charge (e.g. sitting at a dock for long periods), then who cares. The float voltage is a bit high, though. Should be 13.6 likely. That *could* lessen the life of the batteries. But, there's probably a lot of folks that will debate. I tend to lean towards recommendations from the likes of battle born and other top quality battery manufacturers, which is 13.6 max.

The batteries at this point are getting cheap enough that it might be time to stop worrying about lessening the life span. Sure they could continue to lose capacity, but 7 or 8 years from now when that's a concern, we'll probably all be switching to kryptonite batteries or something.

[CarlF]

Unlike AGM’s, LFP batteries last longer if not charged to 100%. Can you set custom settings? Or maybe use the Gel settings?

The 13.8 float is likely to reduce the battery life at least some. .

On my boat I have the inverter/charger and alternator set to 14.0V (about 95% charged) and have only the solar controller set to my battery spec of 14.2v. The reason is that most BMS do their battery cell balancing only when above 14.0v. So getting above 14.0 once in a while is a good idea.

You also care about the absorption time. For AGM’s absorption time is hours. For LFE it can be as little as 2 minutes. If you can’t set the absorption time shown in the battery spec, use a lower absorption voltage to put less strain on the battery during the lengthy time at absorption voltage.

[CaptainRivet]

Very simple, instead 10x 100AH drop ins with shitty 5$ BMS get 12x 304AH EVE cells and run them 3p4s with a Electrodacus or REC BMS. The BMS controlls the charge then and simply switch of the mastervolt when your end of charge is reached 3,55V i recommend. Needs less space and these BMS are lightyears better then the deop in ones.

[SVSeaHawk]

Originally Posted by sailingharry

Those bulk/charge numbers should work great. The battery specs seem to be tolerant of 14.6, so your 14.4 should not be a problem.

Float should actually be pretty good. Eventually, your charge level will go down some, but LFP like that. I have not yet gone to lithium, but I suspect that if I do I will set all of my high power charge sources (alternator and shore charger) at a slightly lower voltage than full. This will allow the solar to bring them up to full and hold them there during the day, and then allow them to drift down overnight even when on shore power. You haven't mentioned your solar, but if at least one of your solar chargers is adjustable, you can make that the one that gives you a periodic full charge.

I do not have solar (insert sad face emoji). Alt, shore and 5kw Onan generator.

I can fiddle with those other charge sources and see if I can't set a higher threshold for one so I can punch it up to full every now and then. A very good idea.

[SVSeaHawk]

Originally Posted by SV Confianza

The problem is usually that the LFP will charge very slowly, since the charge current dramatically decreases when it goes into absorption. The manual for your charger says that it goes into absorption once it sees 14.4v.

Now, I'm going to do some guessing, but with 1000ah of lithium, and if you have your batteries in parallel with bus bars (all cables the same length as well) rather than just daisy chained, the charger amps won't have such a huge influence on the bus voltage, compared to, say, only 200ah. That means you'll likely get a pretty good charge before it hits absorption.

It's a bit of a guess though without testing it in real life.

My victron is set to charge at 14.6 with basically no absorption or float, for comparison.

If it doesn't really matter if your batteries take long to charge (e.g. sitting at a dock for long periods), then who cares. The float voltage is a bit high, though. Should be 13.6 likely. That *could* lessen the life of the batteries. But, there's probably a lot of folks that will debate. I tend to lean towards recommendations from the likes of battle born and other top quality battery manufacturers, which is 13.6 max.

The batteries at this point are getting cheap enough that it might be time to stop worrying about lessening the life span. Sure they could continue to lose capacity, but 7 or 8 years from now when that's a concern, we'll probably all be switching to kryptonite batteries or something.

Faster charging is one of the big selling points for the switch to lithium. So if I understand what you're saying, the charge currant will drop when it goes into absorb and then i'll be waiting forever to get the last percentage points of charge into the batteries, whatever percent that may be.


This concerns me. More if it's like 10% of the battery's capacity, less if it's more like 2%. Sailingharry recommended setting another charge source to a higher bulk setting so they will reach closer to 100% when that source is working. This seems very logical to me. We'll see if I have that ability when I begin digging into the windgen and alternator literature (which is on the boat).


Also please send link to krytonite options as well any cold fusion devices you like.

[SVSeaHawk]

Originally Posted by CarlF

Unlike AGM’s, LFP batteries last longer if not charged to 100%. Can you set custom settings? Or maybe use the Gel settings?

The 13.8 float is likely to reduce the battery life at least some. .

On my boat I have the inverter/charger and alternator set to 14.0V (about 95% charged) and have only the solar controller set to my battery spec of 14.2v. The reason is that most BMS do their battery cell balancing only when above 14.0v. So getting above 14.0 once in a while is a good idea.

You also care about the absorption time. For AGM’s absorption time is hours. For LFE it can be as little as 2 minutes. If you can’t set the absorption time shown in the battery spec, use a lower absorption voltage to put less strain on the battery during the lengthy time at absorption voltage.

The AGM and Gel settings are the same.

There is a "traction" setting that goes ... Bulk 14.6/abs 14.45/float13.25
I don't know what traction means, so feel less confident using it. It extends the time at bulk and absorb by 120min. which i dont understand either as I thought the device moved between those settings based on voltge.

[Rohan]

Originally Posted by SVSeaHawk

The AGM and Gel settings are the same.

Not on my boat, with a Protech-4 charger, which is a fairly common one.

For 12v,

AGM
14.7 Absorption,
13.5 Float

Gel
14.1 Absorption,
13.5 Float

14.7 is a little hot for LiFeP0s, so I use the gel setting and its working fine so far.

To the OP, I asked a similar question back in July. You can find more information here:

https://www.cruisersforum.com/forums...es-278038.html

[SVSeaHawk]

Originally Posted by CaptainRivet

Very simple, instead 10x 100AH drop ins with shitty 5$ BMS get 12x 304AH EVE cells and run them 3p4s with a Electrodacus or REC BMS. The BMS controlls the charge then and simply switch of the mastervolt when your end of charge is reached 3,55V i recommend. Needs less space and these BMS are lightyears better then the deop in ones.

I like this option. I could fit 1200ah in the space i currently have 800ah. And the BMS you recommended is very nice indeed.


I was not going to buy 10x100ah batteries. The same company has a 400ah version and I was going to get three of those. This does not solve the quality of the BMS issue (just lowers the number of crappy BMSs from ten to three.



Ultimately though, the sealed battery option is more appealing given the wet marine environment not friendly to exposed wiring generally and the location of the batteries specifically. Also there is some squishing needed i understand with these batteries. Also I'm not excited about babysitting the charge cycles and shutting off the mastervolt manually when the batteries reach 3.55v.


Certainly the next boat (which will definitely be my last, for sure) I will create a system very much like you describe.

[__fdom__]

This concerns me. More if it's like 10% of the battery's capacity, less if it's more like 2%. Sailingharry recommended setting another charge source to a higher bulk setting so they will reach closer to 100% when that source is working. This seems very logical to me. We'll see if I have that ability when I begin digging into the windgen and alternator literature (which is on the boat).


Also please send link to krytonite options as well any cold fusion devices you like.[/QUOTE]

The real working voltage range is between 3.0 and 3.4 V. That is were you get the vast majority of your amp hours from. I would expect you miss something in between 1% and 3% of your capacity at most.

[sailorboy1]

I don't really understand the fear. If the voltage is in the battery range it is fine. I use a "gel" sitting on my charger for my LFP batteries, but have used one of the AGM settings in the past before I decided 98% charged was enough.