How to deal with the alternator?!

[s/v Jedi]

Originally Posted by Pitchondesign

The ultra capacitor eliminates the need for the dc-dc charger. Other than that, no advantage. I was thinking in terms of a 12v lithium only system, where start and house banks are lithium. In such a system a small ultra cap battery would provide better protection than a zap stop diode or the Sterling system, both of which can be blown without any indication.

Okay I agree... but

why lithium start batteries? Just to eliminate the dc-dc charger? But that means you need a new alternator and/or regulator that can charge lithium instead of lead acid.

For operational use, I see very few disadvantages of an AGM start battery vs lithium start battery.

[Pitchondesign]

I agree. AGMs for start are fine, even with the dc-dc charger. I was thinking in terms of the Ultra Cap battery instead of zap stops and the Sterling device to prevent transients.

Originally Posted by s/v Jedi

Okay I agree... but [emoji3]

why lithium start batteries? Just to eliminate the dc-dc charger? But that means you need a new alternator and/or regulator that can charge lithium instead of lead acid.

For operational use, I see very few disadvantages of an AGM start battery vs lithium start battery.

[tanglewood]

Originally Posted by Pitchondesign

I agree. AGMs for start are fine, even with the dc-dc charger. I was thinking in terms of the Ultra Cap battery instead of zap stops and the Sterling device to prevent transients.

I think it would probably work. But to me, the first choice is to cut the field before a disconnect.


And keep in mind that a disconnect is a fault condition, and should never happen in a properly operating power system. That may guide how you approach alternator control.

[s/v Jedi]

Originally Posted by Pitchondesign

I agree. AGMs for start are fine, even with the dc-dc charger. I was thinking in terms of the Ultra Cap battery instead of zap stops and the Sterling device to prevent transients.

Oh yes, no such devices for me either. It appears the zap stops are not sufficient and the Sterling devices have yet to be proven to be effective in real world use... I have not heard any recommendations from users who have seen it being effective during disconnect events.

[NPCampbell]

Originally Posted by s/v Jedi

Okay I agree... but

why lithium start batteries? Just to eliminate the dc-dc charger? But that means you need a new alternator and/or regulator that can charge lithium instead of lead acid.

For operational use, I see very few disadvantages of an AGM start battery vs lithium start battery.

The pros on the LFPs for starting batteries are the typical ones everyone knows about (I think).

Pro's of LFPs:

• They don't outgas hydrogen during charging
• They're lighter
• They charge quicker because they can handle higher current
• They handle around 4 times the cycles of an AGM
• At full charge, the charger shuts off eliminating electrical parasitic load and that reduces the corresponding mechanical load on the engine
• They have a 5-10% higher charge efficiency than AGM so they generate less mechanical load on the alternator and the engine
• Since they have higher charge efficiency they also generate less heat during an equivalent charge cycle than AGM
• They have higher depth of discharge than AGM(at the cost of battery life)

Cons

• They cost more
• The chargers cost more and are more complex (balancing, etc)
• The batteries require a protection circuit to prevent overcharge, etc.
• They have poorer cold weather performance than AGM
• The BMS disconnect at full charge can roast the alternator without an APD
• An LFP charger can present too much load to an alternator when the engine is running at low RPMs. This can overwhelm the mechanical fan on the alternator without taking temperature or charge precautions.

[s/v Jedi]

Originally Posted by NPCampbell

The pros on the LFPs for starting batteries are the typical ones everyone knows about (I think).

Pro's of LFPs:

• They don't outgas hydrogen during charging
• They're lighter
• They charge quicker because they can handle higher current
• They handle around 4 times the cycles of an AGM
• At full charge, the charger shuts off eliminating electrical parasitic load and that reduces the corresponding mechanical load on the engine
• They have a 5-10% higher charge efficiency than AGM so they generate less mechanical load on the alternator and the engine
• Since they have higher charge efficiency they also generate less heat during an equivalent charge cycle than AGM
• They have higher depth of discharge than AGM(at the cost of battery life)

Cons

• They cost more
• The chargers cost more and are more complex (balancing, etc)
• The batteries require a protection circuit to prevent overcharge, etc.
• They have poorer cold weather performance than AGM
• The BMS disconnect at full charge can roast the alternator without an APD
• An LFP charger can present too much load to an alternator when the engine is running at low RPMs. This can overwhelm the mechanical fan on the alternator without taking temperature or charge precautions.

I agree with this list in the context of a house battery, but not for a starter battery. Not that these points aren’t true; it’s just that they aren’t applicable for starting service.

- outgas hydrogen: neither does AGM
- lighter: no factor for just one starting battery
- charge quicker: starting batteries are always full
- cycle life: starting batteries don’t cycle
- charger shut-off instead of float: so you hope... most alternator regulators do float
- less mechanical load: no, more load. So much more that belt-saver routines are used to reduce it.
- less heat: no, more heat. Most burned up alternators are from lithium charging. It is less total heat energy but it is concentrated in a much shorter time, with the alternator unable to dissipate it
- higher depth of discharge: starter batteries don’t discharge at all,let alone “deep”.

[NPCampbell]

Originally Posted by s/v Jedi

I agree with this list in the context of a house battery, but not for a starter battery. Not that these points aren’t true; it’s just that they aren’t applicable for starting service.

Most of the time this is absolutely correct. However ...

Originally Posted by s/v Jedi

- outgas hydrogen: neither does AGM

All lead acid batteries generate hydrogen (and oxygen) as a byproduct of charging, even AGM and gel. Under "normal" situations, AGM and gel re-absorb the gases that are generated. However, an AGM battery is still required to be valve regulated because "normal" conditions don't always apply. An errant charger or an overly hot battery will cause an AGM battery to outgas. I believe the ABYC still recommends that AGMs are installed with the same precautions as FLA for this reason.

Originally Posted by s/v Jedi

- lighter: no factor for just one starting battery
- charge quicker: starting batteries are always full
- cycle life: starting batteries don’t cycle
- charger shut-off instead of float: so you hope... most alternator regulators do float

Lead acid batteries should be floated to achieve a full saturation charge to reduce sulfation. LFP shouldn't. This is why I listed a "con" that LFP require more complex chargers. If you try to float an LFP without going through an LFP specific charger then you are reducing the life of your battery. An LFP specific charger should completely shutoff (hence the BMS disconnect problem) when the battery is full.

Originally Posted by s/v Jedi

- less mechanical load: no, more load. So much more that belt-saver routines are used to reduce it.

I'm not familiar with the belt saver routines. However, if these are required due to the higher load that an LFP charger can present to the alternator, then yes, this is why I listed as a "con" that LFP require more complex chargers to limit their load and to take into account other factors like alternator temperature, etc.

However, given an AGM battery depleted by 100AH and an LFP with the correct charger, depleted by 100 AH, the AGM will require more mechanical load on the engine to charge to full over the LFP due to the AGMs lower charge efficiency and the requirement to float the AGM battery.

I am also ignoring the fact that even though the float charge takes minimal current, if you don't have another method of charging your battery for 10+ hours to saturation then you will be degrading your AGM due to sulfation unless you want to run your engine for that long.

Originally Posted by s/v Jedi

- less heat: no, more heat. Most burned up alternators are from lithium charging. It is less total heat energy but it is concentrated in a much shorter time, with the alternator unable to dissipate it

Correct. Once again, this is why you need more complex chargers to take load and temperature into account. However, just as above, due to AGMs lower charge efficiency and floating, an AGM will generate more heat during charging than an equivalent LFP battery.

Originally Posted by s/v Jedi

- higher depth of discharge: starter batteries don’t discharge at all,let alone “deep”.

I agree. The only time it would matter would be if it sat for a long off season or you had engine trouble and repeatedly needed to crank the engine and even then it would take a lot of cranks.

[s/v Jedi]

Originally Posted by NPCampbell

Most of the time this is absolutely correct. However ...

All lead acid batteries generate hydrogen (and oxygen) as a byproduct of charging, even AGM and gel. Under "normal" situations, AGM and gel re-absorb the gases that are generated. However, an AGM battery is still required to be valve regulated because "normal" conditions don't always apply. An errant charger or an overly hot battery will cause an AGM battery to outgas. I believe the ABYC still recommends that AGMs are installed with the same precautions as FLA for this reason.

The over pressure valve is present on LiFePO4 as well. Under normal circumstances, which should be 100% of the time of use aboard our boats, neither one should vent to the atmosphere.

It’s clear we agree on all points

[NPCampbell]

Originally Posted by s/v Jedi

The over pressure valve is present on LiFePO4 as well. Under normal circumstances, which should be 100% of the time of use aboard our boats, neither one should vent to the atmosphere.

It’s clear we agree on all points

We do mostly ... but do vent those batteries. You don't want to lose a boat due to a bad charger or alternator.

Incidentally, I did make the same decision as you in my fishing boat. I wanted to convert the three marine batteries to LFP in my fishing boat to extend my trolling times and reduce the weight but I don't have the ability to regulate my outboards 50AH alternator. I could have gone mix mode between the starter battery and trolling batteries but I'd need dual battery chargers and that would limit my charging options through a 15 amp wall plate. I ended up with 3 lighter weight AGMs for simplicity and cost.

[timohara]

Does anyone think this product from Victron would solve the problem -

Smart BMS CL 12/100
https://www.victronenergy.com/batter...urrent-limiter

It appears to be specifically designed to deal with Lithium charging from Alternators - and the disconnect. I am thinking of installing when I upgrade to Lithium.

Any thoughts ?

[rgleason]

Timohara do not double and triple post and mess up other threads please. It is unnecessary. Be patient!

[NPCampbell]

Originally Posted by timohara

Does anyone think this product from Victron would solve the problem -

Smart BMS CL 12/100
https://www.victronenergy.com/batter...urrent-limiter

It appears to be specifically designed to deal with Lithium charging from Alternators - and the disconnect. I am thinking of installing when I upgrade to Lithium.

Any thoughts ?

This looks like it is a normal BMS. A BMS causes the alternator disconnect problem. It does provide an alarm before disconnect but one toilet trip could toast your alternator depending on the duration of the warning. An "Alternator Protection Device" or APD protects the alternator against a BMS disconnecting.

[rgleason]

Originally Posted by NPCampbell

This looks like it is a normal BMS. A BMS causes the alternator disconnect problem. It does provide an alarm before disconnect but one toilet trip could toast your alternator depending on the duration of the warning. An "Alternator Protection Device" or APD protects the alternator against a BMS disconnecting.

No, I don't believe so, please look at the wiring diagram in the Brochures for both the BMS and Smart BMS!

Alternator is going directly to charge the start battery as I stated in two other threads that this guy posted to.
It depends on wiring it properly the the FLA/AGM Start Bank in accord with the Victron Diagrams to protect the alternator. Even though these BMS state that they will protect the batteries, I think it would be best to have an external regulator that is set up properly in accord with Victron's recommendations, which is perhaps with LiFePo4 parameters, although some installations simply use AGM settings. The LFP parameters will not fully charge the AGM/FLA batteries, but if you have some small amount of solar charging them, they will remain full.

See the wiring diagram here: https://www.victronenergy.com/upload...-12-200-EN.pdf
and here: https://www.victronenergy.com/upload...-12-100-EN.pdf

This is very similar to Zwerfcat's Hybrid Parallel LFP and FLA Installation https://www.zwerfcat.nl/en/lithium-hybrid.html

which has a disconnect relay between the LFP battery and the FLA battery. The Alternator remains connected to the FLA battery so there is little to no damaging spike to the alternator diodes, and the alternator remains protected from damage. See this CF Thread "Discussion of ZwerfCat’s hybrid LI/FLA design" for several good examples of installations... some complicated and others less so, but they all protect both the BMS and the Alternator with different levels of utility in so far as charging. Keep in mind that with a single charge/discharge bus that once disconnected, the house loads are running off the Starter Battery entirely and the LFP are completely isolated. Which I believe is detailed more in Frans Veldmann's ZwerfCat github wiki Open Hybrid BMS

-However with the Victron BMS & Smart BMS there is a separate charge/discharge port which then allows the House loads to remain powered by the LFP provided the battery is ok. Which is quite nice. There are some examples of dual bus setups which are essentially the same as Victron's arrangement. Nordykn and Stan Honey's setup and "Mai Tai Endless Summer" in the ssame thread, are all dual bus which are more versatile.

(Conjecture: I think the difference is that Victron's BMS and SmartBMS have Mosfets rated at 100a inside to disconnect the LFP on HVD, LVD, overcurrent and undercurrent, etc.) Should ask about this.

[Deividas]

Can anyone comment if Victron's BMS is suitable only for Victron batteries? Or it could be used with any cells?

[timohara]

Originally Posted by rgleason

Timohara do not double and triple post and mess up other threads please. It is unnecessary. Be patient!

Hi, Apologies and understood. Was keen to get an answer - you are right - I will be patient. Again - apologies. And thanks for your input in the other thread.