LIfePo4 charging?
- Thread starter wandererr
- Start date
jonyjoe101
Adventurer
you should, you just need to check how much charge rate it can handle, the high end batteries can be charged at up to 100 amps. If the battery is too far from the alternator or the gauge of the wire is too thin your never going to get high amps to the battery. As long as the alternator output stays at 14.4 volts your good to go, lifepo4 can max out at 14.6 volts.
Also some alternators on newer cars as soon as the it starts up reduce voltage to 13.8 volts instead of staying at 14.4 volts. At 13.8 volts the battery will never fully charge.
I have a 220ah lifepo4, one time I decided to try and charge it from the cigarette plug with the van running. I was hoping to at least see 15 amps charge rate, but the most I saw was about 4 amps. 4 amps is insignificant for 220ah battery. I was using a dc wattmeter to measure the amps.
Also if you don't have a coulombmeter, get one, thats the only way you know for sure what the SOC of the battery is. That way you only have to charge it as needed. The coulombmeter counts amps in/out of the battery, with it you can actually see how many amps the alternator is actually charging at. You can find meters that can measure up to 300 amps for less then 50 dollars. Highly recommend you get one like the tk15.
Also some alternators on newer cars as soon as the it starts up reduce voltage to 13.8 volts instead of staying at 14.4 volts. At 13.8 volts the battery will never fully charge.
I have a 220ah lifepo4, one time I decided to try and charge it from the cigarette plug with the van running. I was hoping to at least see 15 amps charge rate, but the most I saw was about 4 amps. 4 amps is insignificant for 220ah battery. I was using a dc wattmeter to measure the amps.
Also if you don't have a coulombmeter, get one, thats the only way you know for sure what the SOC of the battery is. That way you only have to charge it as needed. The coulombmeter counts amps in/out of the battery, with it you can actually see how many amps the alternator is actually charging at. You can find meters that can measure up to 300 amps for less then 50 dollars. Highly recommend you get one like the tk15.
SailRedemption
Member
We charged our lifepo4 batteries on our sailboat with a 250a large frame alternator. We had 540ah of previously used EV CALB 180ah cells so we probably had a little less than 100% capacity. We had a Balmar alternator charge controller to control the volts. For this chemistry you need only regulate the volts. We would charge at 220a at 13.8v and cut off the alternator with a switch once the amps started dropping down to about 30a at 13.8v. We wouldn't charge again until the batteries hit 11.8v, if I remember correctly. We could get roughly 65-70% depth of discharge from our bank.
We had a external BMS but it only balanced at the cell level and only very, very slowly. we had it wired for low voltage cutoff only but it could also cutoff for high voltage as well(in the case of a failed charge controller or charger). I wouldn't totally rely on the internal BMS, I would consider it the failsafe.
I would also agree with john61ct(who if is the same person, he's over on a cruising forum in the LifePo4 thread, which is an excellent but long read if you want to know more about the chemistry for off-grid use) about getting a dc-dc charger and would also recommend Victron or Sterling. Both are excellent brands had one of each battery charger on our sailboat. You need this because if you hook your battery up directly to your alternator it will ask EVERYTHING from your alternator. If it's rated for 100a, that battery will take all 100 until it's charged. It's one of the joys of lithium. This will lead to early failure of your alternator because it's not designed or rated for that kind of continuous output.
I have the exact setup in our truck, albeit with a sealed AGM instead, for our fridge in the back. We have an automatic charge relay that opens when the alternator isn't charging/truck is off.
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We had a external BMS but it only balanced at the cell level and only very, very slowly. we had it wired for low voltage cutoff only but it could also cutoff for high voltage as well(in the case of a failed charge controller or charger). I wouldn't totally rely on the internal BMS, I would consider it the failsafe.
I would also agree with john61ct(who if is the same person, he's over on a cruising forum in the LifePo4 thread, which is an excellent but long read if you want to know more about the chemistry for off-grid use) about getting a dc-dc charger and would also recommend Victron or Sterling. Both are excellent brands had one of each battery charger on our sailboat. You need this because if you hook your battery up directly to your alternator it will ask EVERYTHING from your alternator. If it's rated for 100a, that battery will take all 100 until it's charged. It's one of the joys of lithium. This will lead to early failure of your alternator because it's not designed or rated for that kind of continuous output.
I have the exact setup in our truck, albeit with a sealed AGM instead, for our fridge in the back. We have an automatic charge relay that opens when the alternator isn't charging/truck is off.
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Yes of course same human behind this obscure handle
my latest rant on the topic
www.sailnet.com
my latest rant on the topic
LiFePO4 Batteries for The Rest of Us
www.sailnet.com
SailRedemption
Member
Right on! I have some good screenshots of parameters but I'm at work on a ship but I'll get them next week when I get off.. it makes it easy to set up this chemistry. That said I have no idea about these drop in internally regulated batteries they have now. Been out of the loop for a while.Yes of course same human behind this obscure handle
my latest rant on the topic
LiFePO4 Batteries for The Rest of Us
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SailRedemption
Member
Honestly, to the OP, I would get a good quality sealed AGM or gel battery and spend the extra money on a solar controller and panel. Ideally get a panel that will keep up or is double the amps as your fridge and accessories draw.
You'll likely get better results from that than getting 20-30% more ah from a lithium battery. But like I mentioned earlier I have no idea prices or complexity of these new drop in lithium batteries so the cost may not be that much different from a quality deep cycle AGM or gel.
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You'll likely get better results from that than getting 20-30% more ah from a lithium battery. But like I mentioned earlier I have no idea prices or complexity of these new drop in lithium batteries so the cost may not be that much different from a quality deep cycle AGM or gel.
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67cj5
Man On a Mission
Like most of us I think he wants Lithium Tech due to the Charge time,
SailRedemption
Member
I get it for sure, it is game changing.Like most of us I think he wants Lithium Tech due to the Charge time,
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So it worked out pretty well. The battery was behind the isolator and while in the future DC to DC charger might be in my cards, at least one more trip will be setup this way.
Oh yeah, I do have solar and a charge controller for solar, but that doesn't always work out too well due to location of the vehicle (even with a removable panel) due to shade, overcast and weather
Oh yeah, I do have solar and a charge controller for solar, but that doesn't always work out too well due to location of the vehicle (even with a removable panel) due to shade, overcast and weather
SailRedemption
Member
Nice, glad to hear! I didn't see it mentioned, but what size or model battery did you get? I have the same setup as you from what it seems. I put a on/off switch and auto charge relay for the battery in the back. Lithium would be nice when this battery goes in a few years.
Yea, I could probably use a new panel and controller for our truck. I don't think I'm getting what I should be.
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Yea, I could probably use a new panel and controller for our truck. I don't think I'm getting what I should be.
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DiploStrat
Expedition Leader
Glad it worked, but please permit an observation. You are talking about a relatively small battery, 100Ah. Lithium Iron batteries can pull close to their full capacity if deeply discharged. So, in your case, the maximum draw is probably between 50 and 75A, depending on your depth of discharge.
Go to a 200 - 400 Ah bank and your alternator could suddenly be faced with a 200A+ draw. A very different circumstance.
Go to a 200 - 400 Ah bank and your alternator could suddenly be faced with a 200A+ draw. A very different circumstance.
To answer one of the previous questions the battery is 100AH.
The 8 gauge cable is fused at 20Amps. I don't plant to discharge completely, and if I do, it was an emergency. So while my alternator would support this, the fuses would blow (fused on both ends). In a long run, yes - charger is on the 'need to buy list', but funding isn't there at the moment
Also, I do have a solar battery that will help me keep it topped off when the circumstances allow.
The 8 gauge cable is fused at 20Amps. I don't plant to discharge completely, and if I do, it was an emergency
. So while my alternator would support this, the fuses would blow (fused on both ends). In a long run, yes - charger is on the 'need to buy list', but funding isn't there at the moment Also, I do have a solar battery that will help me keep it topped off when the circumstances allow.
"solar battery" is not a thing outside of marketing blurbs, please link.
And explain what you mean exactly, charging one battery from another is very rarely a good idea.
A 100Ah LFP battery can easily pull 400-600A from a higher voltage charge source if there isn't anything limiting the current in between
Many drop-ins and powerpacks do limit charge current, sometimes even lower than 1C