charging lithium batteries with high amp marine alternator

Barold said:

As I learn more about this I am now considering shelving my victron 100/20 that I purchased with my solar panels and purchasing the Renogy MPPT DC to DC charger as a all-in-one solution to alternator charging AND solar. I like the victron app for configuration and that it would tie into the BMV for temperature monitoring, but I am worried about the alternator and the DC system in the event the LFP BMS cuts off. I am going to maintain a separate lead acid (existing is an AGM) start battery and my plan before considering the MPPT DC to DC charger was to separate the banks, leave the alternator connected to the Start and buy a DC to DC Charger. The Orion TR Smart Charger is about $350CAD so about the same price (if not a little more) as the Renogy.

What would you do? (Space is at a premium but I also want a safe system...

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Neither of those DC-DC chargers will boost the voltage from your 12v system to the 24v tesla battery. You'd need a boost charger like these. I have no experience with either, and you'll have to make sure the output can be configured to work with a Tesla pack's voltage range.



EDIT: Oops...you weren't the one with the Tesla battery. If your's is a 12v battery either of the chargers in your post would work.

Sorry. I should have flagged that I was adding my question to the existing conversation than starting a new thread. @mods if that is preferable I can do that.

Responding to OPs original question as being in the same boat... Balmar alternator and 614 regulator is the expensive and best solution since it monitors the alternator temperature and compensates and allows for charging voltage adjustment.
Cheaper solution is a balmar regulator itself (300$) which can fit to your existing alternator, but the alternator must be modified by you or an alternator shop.
This is what I’m doing, planning to drop the alternator off at a shop in a week when my boat is hauled, unless I can find a good tutorial on doing it online, which I can’t.

bostonbuzz said:

Responding to OPs original question as being in the same boat... Balmar alternator and 614 regulator is the expensive and best solution since it monitors the alternator temperature and compensates and allows for charging voltage adjustment.
Cheaper solution is a balmar regulator itself (300$) which can fit to your existing alternator, but the alternator must be modified by you or an alternator shop.
This is what I’m doing, planning to drop the alternator off at a shop in a week when my boat is hauled, unless I can find a good tutorial on doing it online, which I can’t.

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If you have a recent model Yanmar, Balmar makes a retrofit kit that add's smart regulation capability to the stock valeo alternator. As you stated, it's not cheap - and would require the 614 (or other) regulator to be added.

I have a situation where my alternator is more powerful than the max current I want the lithium bank in my hybrid setup (yes there are good reasons for this) to take. It’s max voltage however is ideal for lithium. Now I could build a current regulator pretty easily or I could fork out for an expensive blue one but this all seems a bit silly when there is one bit of kit that is maintenance free, no electronics, no setup, we are all familiar with it and fight it all the time, it’s called a resistor! Simply work out the current you want, let’s say 50A, the difference between 13.7v, which is an easily achievable charge voltage at fairly low current or whatever takes your fancy, and alternator voltage, say 14.5, so 0.8v R=V/I so 0.055Ω that would give a dissipation of 137W in reality cable and connection resistance will reduce the value needed but 100W dissipation low ohm resistors are £0.99 on ebay. Once battery voltage reaches either alternator voltage or your cutoff voltage get your BMS to switch it off. You will be relatively safe with standard alternator voltages as they won’t push the lithium over 2.65v per cell but I actually switch off at 12.4v which is into the base of the “knee” in the charge curve and avoids the stress of full charge. I have an active balancer simply because I don’t push the battery into the saturated region that resistive ones tend to work in. I find with efficiency set at 96% that the batteries daily reach the 100% voltage I set within 0.5Ah or less of the amp hour count.

Loyalist said:

I currently charge FLA with my 400 watt solar and 100 amp marine alternator. I have not seen any ideas on charging 12 volt lithium with a high amp charging system. If anyone has ideas on this, I would like to hear them. Faster charge acceptance, lower weight, and using a lower state of charge to eliminate two batteries has appeal to this sailor.

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This is a big issue since a BMS can suddenly disconnect the charge device causing the alternator coil to generate a large voltage spike and possibly destroying the alternator diodes. Why don’t 4S BMS’s have an output line that could signal the alternator regulator to shut down before the BMS disconnects the battery? It only requires one output line. Very easy. I wish someone would convince a BMS manufacture to add this. A BMS for less than $100 with this would be a big competitive advantage. Then we could make our own batteries that are safe to charge with an alternator. Will’s current BMS recommendation is $89. Adding a disconnect output line would make it perfect for 4S 100AH batteries.

Pmummah said:

This is a big issue since a BMS can suddenly disconnect the charge device causing the alternator coil to generate a large voltage spike and possibly destroying the alternator diodes. Why don’t 4S BMS’s have an output line that could signal the alternator regulator to shut down before the BMS disconnects the battery? It only requires one output line. Very easy. I wish someone would convince a BMS manufacture to add this. A BMS for less than $100 with this would be a big competitive advantage. Then we could make our own batteries that are safe to charge with an alternator. Will’s current BMS recommendation is $89. Adding a disconnect output line would make it perfect for 4S 100AH batteries.

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Marine BMS sales are such a small portion of the market that I would not expect anything like that soon.

That is why one of the best solutions is the Balmar 614 regulator. You can adjust the voltage down to the point where the charge will taper off without completely topping off the battery.

It can also be adjusted to slowly add load to the alternator so you wont end up burning up belts.

You can add a temperature sensor to monitor the alternator, which is a really good idea since many small frame alternators rated for 100 amps do not really like to push 100 amps for a long time.

Opie91 said:

Marine BMS sales are such a small portion of the market that I would not expect anything like that soon.

That is why one of the best solutions is the Balmar 614 regulator. You can adjust the voltage down to the point where the charge will taper off without completely topping off the battery.

It can also be adjusted to slowly add load to the alternator so you wont end up burning up belts.

You can add a temperature sensor to monitor the alternator, which is a really good idea since many small frame alternators rated for 100 amps do not really like to push 100 amps for a long time.

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Hi and thank you but there is a flaw in your technique. If one cell starts to fail it loose capacity the BMS may disconnect the battery before full voltage of the series cells is reached. Any rotating charge source, wind, water or engine alternator need this protection. I like the 614 but I would like an output from a BMS (not CAN bus) to protect a battery.

Pmummah said:

Hi and thank you but there is a flaw in your technique. If one cell starts to fail it loose capacity the BMS may disconnect the battery before full voltage of the series cells is reached. Any rotating charge source, wind, water or engine alternator need this protection. I like the 614 but I would like an output from a BMS (not CAN bus) to protect a battery.

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That is an unlikely failure and exactly what a Sterling Alternator Protection Device is for.

Opie91 said:

That is an unlikely failure and exactly what a Sterling Alternator Protection Device is for.

Sterling Power USA

dc input charger, alternator to battery charger, marine battery charger dc power, sterling power, on the go charging, turn your alternator into smart, charging of your auxiliary batteries while underway mix on board battery types, battery to battery chargers, battery to battery charging. on the...

www.sterling-power-usa.com

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While I agree the failure I described does not happen often, it, and other failure do happen. So you loose an alternator occasionally? Assuming the charge voltage is below the cut off voltage works almost all the time. A BMS that outputs that it will disconnect is much safer. That said, thank you for the link to the sterling device. Appreciate it. I will order and test for our customers.

Barold said:

If you have a recent model Yanmar, Balmar makes a retrofit kit that add's smart regulation capability to the stock valeo alternator. As you stated, it's not cheap - and would require the 614 (or other) regulator to be added.

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id like to retrofit my Yanmar/valeo alternator, but avoid the the cost of the Balmar retrofit kit. I started a new thread for that here.

Pmummah said:

While I agree the failure I described does not happen often, it, and other failure do happen. So you loose an alternator occasionally? Assuming the charge voltage is below the cut off voltage works almost all the time. A BMS that outputs that it will disconnect is much safer. That said, thank you for the link to the sterling device. Appreciate it. I will order and test for our customers.

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An alternative arrangement is to keep an AGM engine start battery and charge both the AGM and lifepo4 through an isolator as described here:
http://nordkyndesign.com/electrical-design-for-a-marine-lithium-battery-bank/ (see "Alternative 2 – Split Charging").

There are BMSs that provide provide output signals that you can then do whatever you want with them - say to turn the alternator regulator off, or turn the shore power charger off, or turn the inverter off. See Chargery and ElectroDacus. However, if you are also having this BMS activate a relay to take the battery offline (as well as shutting the regulator down), then you have a race condition where I suspect the alternator is still going to lose. The alternator will probably not shutdown fast enough - before the battery goes offline - and thus you'd still see a voltage spike and fry the alternator output diodes. Maybe you could put a delay on the signal to the relay that takes the battery offline...

jaffadog said:

An alternative arrangement is to keep an AGM engine start battery and charge both the AGM and lifepo4 through an isolator as described here:
http://nordkyndesign.com/electrical-design-for-a-marine-lithium-battery-bank/ (see "Alternative 2 – Split Charging").

There are BMSs that provide provide output signals that you can then do whatever you want with them - say to turn the alternator regulator off, or turn the shore power charger off, or turn the inverter off. See Chargery and ElectroDacus. However, if you are also having this BMS activate a relay to take the battery offline (as well as shutting the regulator down), then you have a race condition where I suspect the alternator is still going to lose. The alternator will probably not shutdown fast enough - before the battery goes offline - and thus you'd still see a voltage spike and fry the alternator output diodes. Maybe you could put a delay on the signal to the relay that takes the battery offline...

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Parallel a small Lead acid battery in and but sterling Alernator disconnect protection device...problem solved

lolailando said:

I also wonder why noone has tried to swatch off the alternator field current on command from the BMS....just wire the bms to the B+ instead of switching of the charge to the battery (or and switch off the LFP battery through a delayed relay)....what am I missing? The lead/starter/dump battery for all of us in trucks and vans is a no brainer to keep it.

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The B+ terminal is not the field terminal as such, it does supply a positive to the field, via the warning light, to initially excite it, after that the alternator supplies the positive to the field and will keep working with the B+ disconnected. You have to go into the alternator and disconnect the opposite brush from the regulator. This is what you have to do to install 3rd party regulators, some work alongside the original and some replace them.

Justin Laureltec said:

.... A Battle Born, for instance, is perfectly happy on an FLA profile if you decrease the absorption time.

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Battleborn, and other lithium packs, tolerates the improper Lead-Acid charging regimen by employing a BMS to protect the cells from such foolishness as temp-comp, bulk, absorption, float, boost, storage, and equalize. I have ordered my first lifepo cells and I will bid good riddance to that LA sort of thinking.

lolailando said:

I also wonder why noone has tried to swatch off the alternator field current on command from the BMS....just wire the bms to the B+ instead of switching of the charge to the battery (or and switch off the LFP battery through a delayed relay)....what am I missing? The lead/starter/dump battery for all of us in trucks and vans is a no brainer to keep it.

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They have. It's only that feature is found on high end regulators and BMS units. The Wakespeed alternator regulator will connect to a BMS via the can bus so the BMS can control it. I believe both the Victron and REC BMS will talk to it.

Cheaper products don't target the special use case, so even though it is relatively easy to implement, they don't bother to add it.

lolailando said:

Thank you, I understand. I have looked at the wakespeed and its awesome, and I would pay that big money if I was on a boat or using it as a business...but for camping here and there I'm trying to find a cheap option that gives 80% of the efficiency and longlife of the wakespeed. There will always be people that like to have the best, use it professionally, or are on boats where you just don't call AAA for a tow, and for those the wakespeed is clearly thousand miles more advance than anything else. I still would like to find out if anyone has diy to try to control the regulator based on some temp control.....I have learnt through other projects that sometimes noone had the interest to do something different, but many time it is for some very good reason that it wouldn't work, or it wouldn't be reliable etc....I rather learn from others mistakes than waste my time. Thank you.

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I actually use a very simple system to regulate my alternator so as not to overheat it when charging Lithium and that is simply to use the resistance of the cables. Because LiFePO4 have such a flat charging curve, with most of it being around 13.8v for a 12v set of 4 cells, you just use a cable that will drop the difference between that and the alternator voltage at the current you decide is safe. If alternator is 14.5v then you need to drop 0.7v at say 50A =0.014 ohms shared between positive and negative. That would dissipate 35W as heat. You would also set your BMS to cut off at 14.4v to avoid low voltage overcharge

lolailando said:

Thank you, I understand. I have looked at the wakespeed and its awesome, and I would pay that big money if I was on a boat or using it as a business...but for camping here and there I'm trying to find a cheap option that gives 80% of the efficiency and longlife of the wakespeed. There will always be people that like to have the best, use it professionally, or are on boats where you just don't call AAA for a tow, and for those the wakespeed is clearly thousand miles more advance than anything else. I still would like to find out if anyone has diy to try to control the regulator based on some temp control.....I have learnt through other projects that sometimes noone had the interest to do something different, but many time it is for some very good reason that it wouldn't work, or it wouldn't be reliable etc....I rather learn from others mistakes than waste my time. Thank you.

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The Balmar ARS-5 is cheaper than the wakespeed but still a great option. Still not cheap though. It has an alternator temp sensor, and while it doesn't directly support Lifepo4, you can manually set the voltages and absorb time to support lifepo4. It also has a "beltsaver" mode to manually derate an alternator and limit current. I think it is limited to 120A alternators, so not for a huge alternator installation.


For a dirt cheap option, I wonder if those kits designed for turning a radiator fan on/off could be rigged to turn an alternator on/off? Or, using a resistor parallel to the temp switch to derate the alternator at the set temperature.

lolailando said:

Thank you so much for your comment SolarMuppet; I read a comment some where else in the forum (probably you) explaining that with some amps example and #1 cables I think.....but then I tried to search for it a few times and could never find it or quite remember how it work, so thanks again. My truck shows 13.8v study at the usb cigarete lighter adapter while driving. I will do a few checks and calculations.
Did you mean: set the BMS at 14.4v to avoid high voltage overcharge? 14.4v doesn't look like low voltage to me but would like to learn.
Do you mind to post how many amps are you able to pump into the LFP? I got a continous duty alternator 215A and the truck takes 45A, so I am wondering if getting 150A is realistic? I won't have my LFP for another 3 months so I can't test lol.
thanks again.

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I would say 130A would be reasonable as things don’t generally like running maxed out. I did mean LOW voltage overcharge. The reason being that many BMS’ cut off at 14.6v (3.65v per cell) if your alternator can’t reach this then the BMS won’t cut out causing low voltage overcharge. The answer is to lower the cutout to below the alternator maximum. You can full charge Lithiums below their max cutout voltage. 14.4v is well into the upper 90% range and into the ‘knee’ of the charge curve. Using resistance to regulate current you get a short taper at the end of charge which effectively gives you a bit of an absorb time at the slightly lower voltage so you end up getting about the same amount of charge by cutout time.