charging lithium batteries with high amp marine alternator

[jaffadog]

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.

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.

 

[jaffadog]

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.

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...

 

[mndare]

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...

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

 

[SolarMuppet]

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.

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.

 

[gelmjw]

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

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.

 

[wholybee]

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.

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.

 

[SolarMuppet]

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.

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

 

[wholybee]

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.

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.

Balmar Multi-Stage Voltage Regulator

The ARS-5 Multi-Stage Voltage Regulator features the latest multi-stage control for multiple battery types, along with an easy, basic method of programming. Once the appropriate battery type is selected, the regulator enables you to select the proper powe

www.defender.com

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.

 

[SolarMuppet]

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.

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.