Charging LiFoPO4 without DC-DC charger

[RedRascal]

Looking at a possible simple charging setup that goes from an 160amp alternator to a LifePO4 house bank without killing the alternator. Here's the current setup that is on a single 120 Lehman:
-Stock alternator charging the starting bank, no changes here
-160 amp alternator with Sterling ProD external regulator, regulator just manipulates voltage over time and adjusts voltage for alt temp, no current management, this charges lead acid house bank of 6 golf cart batteries
-ACR from house bank connected to 2 group 24 AGM batteries for bow thruster

Looking to switch the house bank to LiFoPO4 and ditch golf cart batteries with this setup:
-House bank equals 2 Eco Worthy 150ah LiFoPO4 batteries with 120amp BMS($170 on Ebay right now) so 300 amps total when new
-160 amp alternator to an 200amp 2 battery Victron Argofet isolator(victron claims only .1 voltage drop)
-1 output from the victron isolator goes to the house bank
-2nd output from the victron isolator goes to the agm bow thruster batteries
-Set Sterling regulator to 14.1 or maybe 14.4 volts so both the LiFePO4 and AGMs will be happy enough when motoring
-Windlass draws 50 amps from house bank so looking to size wires from isolator to house bank for about 100amps. Enough to cover windlass draw without cooking the wires from the alternator to the house bank. Also using wire size to limit current from alternator to house bank to lower the charge rate on the LiFoPO4, this may or may not be a flaw.

Not looking a perfect .2C charging curve or maximum battery life. The reality for me when cruising is I'll either be making a 1-2 hour hops between anchorages or longer transit days for 4-6 hours of running. The LiFoPO4s may only see 120 cycles in a season so not worried about trying to get 4,000 cycles out of them. I'd be tickled to throw 100amps into them in an hour.

Yes I know I could go 160amp alternator to lead acid then DC-DC to LiFoPO4. However I'd need to use two DC-DC chargers to take advantage of 160amp alternator.

Any suggests for making this work without breaking out another thousand???

 

[Graeme Walker]

DC-DC charges are relatively cheap, start with one and see how it goes. Simple and easy.
Not familiar with Eco Worthy batteries, don't they already have an internal BMS?

 

[RedRascal]

The Eco Worthy batteries do have an internal BMS.

 

[psneeld]

This is what my RV has and it works great.

https://www.amazon.com/dp/B07DY8S815?ref_=ppx_hzod_title_dt_b_fed_asin_title_0_0

 

[Mambo42]

The LiFePO4's can handle a full charge until 100 % and after that it is abruptly back to zero. AGM on the other hand cannot handle a max charge to 100 %.
I understand you would like to use the 160 A alternator to its fullest and directly into the LiFePO4 would make most sense. Going via a DC-DC charger does not really make any sense at all.
To me the best solution would be to add a Wakespeed controller to your alternator. That controller is made for LiFePO4 batteries and it keeps the charge at 100 % (or lower if you so desire) until 100 % battery charge and then it switches off the alternator. They are not cheap, that is for sure, but they do the job and that will enable you to use the LiFePO4 batteries to their full potential.
Other option would be to add a few solar panels, but the total cost of solar panels, MPPT controllers etc is about the same as that of a Wakespeed controller.

 

[RobertLeatch]

Also using wire size to limit current from alternator to house bank to lower the charge rate on the LiFoPO4, this may or may not be a flaw.

Not sure how this works in practice. Are you reducing the wire cross sectional area (undersizing it) or increasing the length (to cause excessive voltage drop)?

 

[RedRascal]

This is what my RV has and it works great.

https://www.amazon.com/dp/B07DY8S815?ref_=ppx_hzod_title_dt_b_fed_asin_title_0_0

Thanks for the link, I'll study it.

 

[RedRascal]

The LiFePO4's can handle a full charge until 100 % and after that it is abruptly back to zero. AGM on the other hand cannot handle a max charge to 100 %.
I understand you would like to use the 160 A alternator to its fullest and directly into the LiFePO4 would make most sense. Going via a DC-DC charger does not really make any sense at all.
To me the best solution would be to add a Wakespeed controller to your alternator. That controller is made for LiFePO4 batteries and it keeps the charge at 100 % (or lower if you so desire) until 100 % battery charge and then it switches off the alternator. They are not cheap, that is for sure, but they do the job and that will enable you to use the LiFePO4 batteries to their full potential.
Other option would be to add a few solar panels, but the total cost of solar panels, MPPT controllers etc is about the same as that of a Wakespeed controller.

This is where I am fuzzy, LiFePO4 says give me lots of current and bow thruster AGMs are topped up so they just want a trickle of current. I don't understand what the AGMs will do in this case. The prior owner cruised the boat for 9 years in the current config of AGMs hooked to lead acid house via ACR. So the AGMs have lived through the lead acid taking a bunch current from the alternator after sitting on anchor for a few days. Agree the Wakespeed would be a good option.

 

[RedRascal]

Not sure how this works in practice. Are you reducing the wire cross sectional area (undersizing it) or increasing the length (to cause excessive voltage drop)?

I guess it would be called undersized if I size to 100amps. Technically I could push the BMS max of 240amps but the alternator can't push that much.

 

[RedRascal]

I just realized I should be able to test max current levels with the existing setup. All I need to do is drain the 600 amp lead acid house bank down and leave the AGMs topped up. The alternator should throw a bunch of amps at the house bank and I can measure how much current is going through the existing wiring to the lead acid house and bow thruster AGMs.

 

[READY]

Using wiring to limit voltage means you are dropping voltage due to wire resistance. This creates heat and is a very bad idea.
I doubt the alternator can sustain 170 amps without potential damage from heat. Maybe add a shunt and 2 DC to DC would be the simple solution. Configure them to regulate max current to avoid overload on wires and alternator. Plus of course proper fusing.

 

[more]

simply sell your alternator ,regulator and buy like this alternator and plug to lifepo4 battery .https://www.ebay.com/itm/306261100942?_skw=water+cooled+alternator&itmmeta=01JVKZDM6V0WJNZ2S3PEYM1VAG&hash=item474e95898e:g:kyQAAOSwJypoBgn5&itmprp=enc%3AAQAKAAAA8FkggFvd1GGDu0w3yXCmi1dw%2B8mQj9DUFjstHXUs%2B8FROgwo16TL6XbluOZBn%2FMOoXPAy5a549CYHP7YZ03SUlzaLYoPBrB%2BY7E6g3OWNk1OPXz6JhgGosKTz9aL5gVx%2F6Fo9FJ1iUuhhEldjwFwsBRcjqoCbbWPo3ztrg8zAO987UM7UXH68Sgi887udfgltc0YGVStBApr49nOsm5fXw0u3y%2FVfYH7xdsGL5BnCKUm5VW4gImt0%2BW0Wfd%2FnSFWPwJOIEJ2aes88NL2%2BVAzoFoYcOwUbkNuJd4x%2FmqOBGaVK6%2F3LY%2FRUPw3LbHqsB29uA%3D%3D%7Ctkp%3ABFBMyMO2_9xl

hi happy work on 95-120°C full power

 

[SteveK]

The PO had both ALT rebuilt so I will wait for a failure before replacement with an external regulator. Meanwhile 100A DC>DC adds about 75A~ to the house battery while supporting ongoing demand with 25A~

 

[luna]

If your existing Sterling regulator cannot shut the alternator off completely and it does not have the ability for the user to set a field current limit and the charge voltages, then I think you should not use it to charge the new LiFePo4 house bank.

You may want to consider doing something like this.

The stock alternator continues to charge the start battery which will typically take less than 10 minutes if things are working right.
Using the existing ACR, connect the bow thruster bank to the start battery. In addition, provided the charge voltages are the same, wire the windlass through a fuse to the bow thruster bank, not the new house bank.
At this point all of the lead batteries are charged by the stock alternator, which is likely just fine as the amount of energy removed from these batteries in normal use is quite small.
Hopefully the are all the same chemistry.

Then to have the 160 A alternator charge the new house bank you will need a new regulator.
Lots of good choices (Wakespeed, Balmar, Zeus) but in keeping with your "without breaking out another thousand" edict, Fisheries has the Balmar MC-618 on for $310.00. You will have to remove or bypass the existing alternator's internal regulator and build your own wiring harness but that is generally easy to do.

Get the Alternator Temp Sensor ($50 +/-) and set it up as a last resort alternator overtemp shut off. I'm a fan of running the alternator at a temperature where it will not repeatedly run up against the overtemp sensor that cuts output. This is done by carefully setting the max. field current in a manner that will allow the alternator to run without overheating, even on a long run on the hottest day of the year.
If you want to run the alternator at a higher output force feed it cool air.

The BMS in the new Eco-Worthy batteries undoubtedly has a high voltage disconnect that will save the battery once it's fully charged by the alternator, but the disconnect act itself by way of the resulting voltage spike will cook the 160 A alternator and maybe other expensive things.
You need a method to safely turn the alternator off before the high voltage disconnect occurs.

Do you have an existing Battery monitor? If so, does it have in it, a programmable relay?

If not, the Victron BMV-712 does, and you could wire the output of the Victron 712's programmable relay to the coil of a larger relay and have the power (red) wire to the regulator connected to the larger relay's controlled NC contacts.
If you then set the Victron programmable relay to change state at say 0.2 Volt below the battery's bms high voltage disconnect voltage, the Battery monitor opens the contacts thereby shutting the alternator off before the bms disconnects.

The BMV-712, the larger relay, a fuse and a disconnect switch should cost you less than $350.

Use the remaining $300 to buy the biggest wire possible to connect the 160 A alternator to the new LiFePO4 battery.

Installation is not included but easily done in a weekend or so.

 

[CharlieJ]

Throttling the current by decreasing the wire size is not good and could be dangerous.

The pros of a DC-DC charger is that it can be adjusted to ease the load on the alternator via the AGM start battery. Conversely, the ACR will pass as much current from the start battery to the LFP bank as it is rated for which does not help the longevity of your alternator.

 

[Barking Sands]

Throttling the current by decreasing the wire size is not good and could be dangerous.

The pros of a DC-DC charger is that it can be adjusted to ease the load on the alternator via the AGM start battery. Conversely, the ACR will pass as much current from the start battery to the LFP bank as it is rated for which does not help the longevity of your alternator.

In addition, the DC2DC provides a complete and proper charge profile with the right absorption voltage, absorption time and then float voltage. A DC2DC IMO is the most perfect solution, with the exception of amp ratings for larger alternators. But even a pair of 50 amp Orions at around $680 for 100 amps of perfect control via super simple install/programming IMO is a bargain. And this would probably suffice most alternators up to 175-200 amps

 

[Don L]

I always get amazed people don't seem to want to protect their alternators. Rebuilt/replacing one is going to be more $$$$ than protection.

 

[RedRascal]

This got too complicate to tackle with all my other projects that need to happen before our summer cruise that starts at the end of June. So it's on pause for now. To be able to use the full potential of my 160 amp alternator the best path looks like Wakespeed or something similar. This will most likely cost less than 2 DC-DC chargers. The Li-BIM could be a solution and seems to be used in the RV world according to YouTube. The combination of lead, agm and Lifo chemistries complicates my situation so this project slides into the off season since my lead and agm batteries can get the job done this summer.

Thanks for all the comments.

 

[HeadedToTexas]

I'm not sure about the Wakespeed, but my Balmar MC-614 has a less informative interface even than my Xantrex Freedom 3012. The new breed of DC-DC chargers would at least let you know what's going on. The new LFP batteries will help too.

 

[twistedtree]

If your existing Sterling regulator cannot shut the alternator off completely and it does not have the ability for the user to set a field current limit and the charge voltages, then I think you should not use it to charge the new LiFePo4 house bank.

You may want to consider doing something like this.

The stock alternator continues to charge the start battery which will typically take less than 10 minutes if things are working right.
Using the existing ACR, connect the bow thruster bank to the start battery. In addition, provided the charge voltages are the same, wire the windlass through a fuse to the bow thruster bank, not the new house bank.
At this point all of the lead batteries are charged by the stock alternator, which is likely just fine as the amount of energy removed from these batteries in normal use is quite small.
Hopefully the are all the same chemistry.

Then to have the 160 A alternator charge the new house bank you will need a new regulator.
Lots of good choices (Wakespeed, Balmar, Zeus) but in keeping with your "without breaking out another thousand" edict, Fisheries has the Balmar MC-618 on for $310.00. You will have to remove or bypass the existing alternator's internal regulator and build your own wiring harness but that is generally easy to do.

Get the Alternator Temp Sensor ($50 +/-) and set it up as a last resort alternator overtemp shut off. I'm a fan of running the alternator at a temperature where it will not repeatedly run up against the overtemp sensor that cuts output. This is done by carefully setting the max. field current in a manner that will allow the alternator to run without overheating, even on a long run on the hottest day of the year.
If you want to run the alternator at a higher output force feed it cool air.

The BMS in the new Eco-Worthy batteries undoubtedly has a high voltage disconnect that will save the battery once it's fully charged by the alternator, but the disconnect act itself by way of the resulting voltage spike will cook the 160 A alternator and maybe other expensive things.
You need a method to safely turn the alternator off before the high voltage disconnect occurs.

Do you have an existing Battery monitor? If so, does it have in it, a programmable relay?

If not, the Victron BMV-712 does, and you could wire the output of the Victron 712's programmable relay to the coil of a larger relay and have the power (red) wire to the regulator connected to the larger relay's controlled NC contacts.
If you then set the Victron programmable relay to change state at say 0.2 Volt below the battery's bms high voltage disconnect voltage, the Battery monitor opens the contacts thereby shutting the alternator off before the bms disconnects.

The BMV-712, the larger relay, a fuse and a disconnect switch should cost you less than $350.

Use the remaining $300 to buy the biggest wire possible to connect the 160 A alternator to the new LiFePO4 battery.

Installation is not included but easily done in a weekend or so.

This is more or less what I was going to suggest. Connect the alternator directly to the LFP bank and get a good alternator regulator. Then repurpose the ACR to tie the start and thruster bank together such that both get charged off the stock engine alternator.

The loophole that still exists, even with some sort of high voltage shutdown of the alternator, is when there is a cell voltage mismatch inside a battery. Only the BMS can see that happening, while the external voltage looks just fine so the external voltage sense will not detect it.

The solution to this is an "allow to charge" signal from the battery, but very few have it. I consider this a defect in most batteries, and it's what forces people to hack together all these Rube Goldberg systems. It's the only reason to use DC/DC converters instead of directly connecting the alternator to the batteries and using a good regulator. DC/DC converters are just more stuff to break, more stuff to buy, more wasted power, and an artificial limit on alternator output. It's all so simple if you just have an Allow To Charge signal from the BMS. You just wire it to the alternator regulator to switch it on/off. One wire, problem solved. But instead everyone continues to do back-flips to preserve the illusion of a "drop-in" battery, rather than press battery makers to provide a simple Allow To Charge signal.

 

[HeadedToTexas]

The solution to this is an "allow to charge" signal from the battery, but very few have it.

Very interesting. Got some examples of batteries with the Allow To Charge signal?

 

[tpbrady]

On caution on the Wakespeed, while not in the tech data, their tech support said not to use a battery isolator like the Victron Argofet and weren’t sure what an ACR would do. Also, while it can be configured without a shunt, they really say it is much better with a shunt, and the Victron Smart Shunt is not suitable as it doesn’t have small accessory terminals on the in and out sides to connect the sense wires.

I’m still learning how it works.

Tom

 

[DDW]

I can't imagine why a Wakespeed would have a problem with an Argofet, and I know for a fact it doesn't have a problem with an ACR. The Wakespeed gives far more visibility into operation than any other available regulator, all parameters can be viewed in real time.

It seems to me the simplest solution to this is to charge through an Argofet or an ACR, retaining an AGM battery for engine start (and to run engine electronics). This way, a disconnect of the LFP causes no immediate problems. Alternator is fine, engine continues to run. I'd put navigation electronics on the AGM side too. I can't see why a DC-DC is useful in this situation. AGM will be perfectly happy with LFP charge settings.

One issue with ACRs is they tend to be set too low for LFP and even AGM. The Blue Sea for example connects at 13V and doesn't open until 12.75. It will stay connected on an at rest LFP and even on a good fully charged AGM.

It would be quite easy to drill and tap a Victron Smart Shunt for the needed connections, at most 10 minutes work.

 

[SteveK]

"allow to charge".
I have wondered why a regular internal regulated ALT knows when to stop charging a FLA battery but not a LFP at 14.4V.

Then my Magnum inverter/charger setting for LFP has Float managed by Battery BMS with only the main +/- cables connected. Yet in fact it works that way. When SOC measured by a shunt and BMS approach 100% the charge voltage drops to 13.5V and zero current unless say the fridge turns on. And only that current being used is output from the charger. The charger maintains load and does not overcharge.

 

[twistedtree]

Very interesting. Got some examples of batteries with the Allow To Charge signal?

MG Energy, many of the Victron BMSes, some Lithionics. I think Mastervolt too. So far I have not seen it in any self-contained "drop-in" batteries, only systems with separate battery packs and BMS. You can pull it out of the DVCC or RV-C canbus data if the battery supports that, and fully functional canbus devices will monitor and respect the ATC "signal" in the canbus messages. But it requires full function canbus controlled chargers. If it were just a set of wires that are on or off, then you could interface it to literally anything.

 

[dutch-barge]

Victron has the perfect DC-DC Charger. for your LI batteries.. luckily my 90 amp 24V alternator does nto gop over 70C even when loading for 2- 3 hours around 60-80 amps, so I did not needed one

 

[richardshulman]

Looking at a possible simple charging setup that goes from an 160amp alternator to a LifePO4 house bank without killing the alternator. Here's the current setup that is on a single 120 Lehman:
-Stock alternator charging the starting bank, no changes here
-160 amp alternator with Sterling ProD external regulator, regulator just manipulates voltage over time and adjusts voltage for alt temp, no current management, this charges lead acid house bank of 6 golf cart batteries
-ACR from house bank connected to 2 group 24 AGM batteries for bow thruster

Looking to switch the house bank to LiFoPO4 and ditch golf cart batteries with this setup:
-House bank equals 2 Eco Worthy 150ah LiFoPO4 batteries with 120amp BMS($170 on Ebay right now) so 300 amps total when new
-160 amp alternator to an 200amp 2 battery Victron Argofet isolator(victron claims only .1 voltage drop)
-1 output from the victron isolator goes to the house bank
-2nd output from the victron isolator goes to the agm bow thruster batteries
-Set Sterling regulator to 14.1 or maybe 14.4 volts so both the LiFePO4 and AGMs will be happy enough when motoring
-Windlass draws 50 amps from house bank so looking to size wires from isolator to house bank for about 100amps. Enough to cover windlass draw without cooking the wires from the alternator to the house bank. Also using wire size to limit current from alternator to house bank to lower the charge rate on the LiFoPO4, this may or may not be a flaw.

Not looking a perfect .2C charging curve or maximum battery life. The reality for me when cruising is I'll either be making a 1-2 hour hops between anchorages or longer transit days for 4-6 hours of running. The LiFoPO4s may only see 120 cycles in a season so not worried about trying to get 4,000 cycles out of them. I'd be tickled to throw 100amps into them in an hour.

Yes I know I could go 160amp alternator to lead acid then DC-DC to LiFoPO4. However I'd need to use two DC-DC chargers to take advantage of 160amp alternator.

Any suggests for making this work without breaking out another thousand???

Take a look at the "Battery Bank manager" Lots of good info on site. I installed Clark's system last year it is excellent

 

[tpbrady]

DDW,

The Wakespeed alternator voltage readings become wildly in accurate when connected to the ArgoFET. They read anywhere from 1 to more than 2 volts high than the actual VOM reading. So the way I found to provide a lead acid battery connection to an alternator in the event of a ruthless disconnect of the LFP bank won’t work with a Wakespeed regulator. As I said earlier, they need to put that in their sales literature and specification sheets. In addition, it appears to be somewhat limited and sometimes confused without an input from a shunt. In summary, it’s too sophisticated for what should be much simpler.

Next week I am switching to a Balmar MC-618. It seems to be less picky, but has some contradictory instructions when a diode based isolator is involved.

Tom

 

[HeadedToTexas]

If you add an external regulator like the Balmar or Wakespeed and use your alternator to charge the new LFP house bank, how will you charge your AGM thruster and start batteries? Either way, a DC-DC charger is a simple and cost effective solution.

The exception might be tweaking the charge profiles to keep both happy. There are several here who thoroughly understand how one profile can keep different battery types happy.

 

[DDW]

DDW,

The Wakespeed alternator voltage readings become wildly in accurate when connected to the ArgoFET. They read anywhere from 1 to more than 2 volts high than the actual VOM reading. So the way I found to provide a lead acid battery connection to an alternator in the event of a ruthless disconnect of the LFP bank won’t work with a Wakespeed regulator. As I said earlier, they need to put that in their sales literature and specification sheets. In addition, it appears to be somewhat limited and sometimes confused without an input from a shunt. In summary, it’s too sophisticated for what should be much simpler.

Next week I am switching to a Balmar MC-618. It seems to be less picky, but has some contradictory instructions when a diode based isolator is involved.

Tom

Can you add some detail on that? Is this the Wakespeed Pro with the BLE interface, or were you logging data on serial or CAN? How was the alternator voltage reading determined? Was there no shunt connected to the Wakespeed at all? Where was the remote sense line for the Wakespeed connected?

I'm about to do this on a new-to-me boat, and would like to understand it in some detail so I don't have the same problems. In fact I might be a ready market for your slightly used Wakespeed .

Some of the Wakespeed sophistication is specific to lead chemistry, in many respects LFP charge profiles are simpler. But I worry that the Balmar, which can't determine when to switch to float, would keep LFP too high most of the time.