DC-DC charger - which direction for Lithium batteries?

[goboatingnow]

Originally Posted by BistroMath

I wouldn't bother trying with the stock alternator. I tried that. Fried both alternators. The stock alternators are not meant to deal with the lack of internal resistance from lithium, they will charge too fast, get too hot, and something will break.



I'm on my third try for alternators (Balmar xt-170 now) and they are...sufficient. I still wish that I went for large case, but at the time it seemed like more trouble than it was worth.

Any stock alternator WITH a proper regulator will charge Li banks. It’s nonsense to suggest otherwise.

we all understand the stock regulator isn’t normally setup to charge to Li profiles. That’s clear. No need to go on about it.

To charge Li you need a new regulator. At a minimum you need field current control.

What ever amps you get from your stock alternator charging SLA you’ll also get from a new regulator charging LI. Typically 50-60 % of plated ratings is achievable. Add extra cooling and sometimes that can be pushed up a little.

[goboatingnow]

Originally Posted by hjohnson

I took the 85A Hitachi I had to my local alternator shop and had them rebuild it, and modify it for external regulation. For $150 CAD, I got new bearings, external regulation, and an up-sized diode pack. I can run it at 60A or so continuously and it never goes above 60C. They also general cleaned it up and repainted it.

Yes indeed , simply making up external diode packs takes a big chunk of heat away. Cheap and well worth doing.

Again some people has this mental block about alternators. All this dc dc stuff to avoid fixing the issue with the alternator on the first place.

[goboatingnow]

Originally Posted by BistroMath

If the 115A alternator is not externally regulated, all of the advice that I've received from installers is that they will not last long. Here's a good excerpt from one of Rod's articles:



"While this alternator temp compensation feature is self protective of the alternator, in theory at least, it is really a very poor regulation choice for an LFP bank. The other conundrum is that the voltages and temp protection features in these internal regulators are based on lead acid voltages, not LFP. With LFP they can literally cut back so much, due to heat, that little to no current can flow into the LFP bank. We have measured Yanmar / Hitachi alternators so hot they have reduced the voltage output to 13.2V. Considering the resting voltage of an LFP bank is higher that, well. This means little to no charging. Discharge the bank deep enough and even these internally temp protected alternators will literally cook themselves. Bottom line? Do it right and include a performance alternator, regulator, temp sensors and pulley kit (for anything over 100A) as part of your “system“.."

This comment makes no sense

An alternator heat production is a function of load. No load no heat.

The alternator has no interest in the type of load whether the given load is Li or SLA is irelevant.


So if your alternator is happy delivering 50 % of rated plate into VRSLA it will CE just as happy delivering 50 % into Li. Yes you need a different regulator because the car regulator is designed as a power supply not a battery charger.

Note that alternator heat protection using stock regulators is based on a “ step back feature “ largely designed to protect the power supply integrity of the car. It’s not a battery charger.

On boats both for SLA and definitely for Li changing the stock regulator for one orientated at charging batteries is money well spent.

[SV Confianza]

Originally Posted by goboatingnow

Yes indeed , simply making up external diode packs takes a big chunk of heat away. Cheap and well worth doing.

Again some people has this mental block about alternators. All this dc dc stuff to avoid fixing the issue with the alternator on the first place.

There are a number of reports on this forum that have made the modification and did not see a noticeable reduction in heat at the alternator. I have not tried it myself.

[SV Confianza]

Originally Posted by goboatingnow

This comment makes no sense

An alternator heat production is a function of load. No load no heat.

The alternator has no interest in the type of load whether the given load is Li or SLA is irelevant.


So if your alternator is happy delivering 50 % of rated plate into VRSLA it will CE just as happy delivering 50 % into Li. Yes you need a different regulator because the car regulator is designed as a power supply not a battery charger.

Note that alternator heat protection using stock regulators is based on a “ step back feature “ largely designed to protect the power supply integrity of the car. It’s not a battery charger.

On boats both for SLA and definitely for Li changing the stock regulator for one orientated at charging batteries is money well spent.

That's not the point. The point is that stock alternators were not designed for ability to load up the alternator for much longer (LFP's low internal resistance is a factor there). They are not continuous duty (nor anywhere close). The alternator is in bulk all the way up and doesn't get a break.

Limiting the alternator to 50% is not a viable charging option for many (like us). Too slow, too much wasted charging time on the engines. We both live/work full time on the boat and have household-like power needs.

I also wanted both alternators charging the LFP bank for redundancy, since no power=no ability to work. Everyone's situation is different, though...

[s/v Jedi]

The comments about stock alternators being incompatible with LFP charging are correct of course. Stock alternators are designed for charging LA start batteries, so a bit of charging after start, then a long time doing very little.

By far the best method to make this suitable for charging LFP is by leaving it all stock including the start battery, and just install a DC-DC charger like the Victron Orion Smart non-isolated 12-12 30A, configure it for alternator detection and a maximum charge current of 50% of the stock alternator. If you have a 60A or better alternator, you can leave the Orion at it’s default 30A, lower it otherwise.

If you need your alternator to be a primary charge source for your LFP battery, then you need to do more: modify or replace the alternator with a model that supports an external regulator and upgrade the pulleys and belt when you go from less than 100A alternator to more than 100A alternator.
Also, you need a regulator that has LiFePO4 charging algorithm as well as a temperature sensor on the alternator to prevent overheating.
For my old Yanmar I replaced the stock Hitachi with a new 170A Balmar, the pulleys and belt with a serpentine version and a Balmar regulator with temperature sensor on the alternator.

[goboatingnow]

Originally Posted by s/v Jedi

The comments about stock alternators being incompatible with LFP charging are correct of course. Stock alternators are designed for charging LA start batteries, so a bit of charging after start, then a long time doing very little.

By far the best method to make this suitable for charging LFP is by leaving it all stock including the start battery, and just install a DC-DC charger like the Victron Orion Smart non-isolated 12-12 30A, configure it for alternator detection and a maximum charge current of 50% of the stock alternator. If you have a 60A or better alternator, you can leave the Orion at it’s default 30A, lower it otherwise.

If you need your alternator to be a primary charge source for your LFP battery, then you need to do more: modify or replace the alternator with a model that supports an external regulator and upgrade the pulleys and belt when you go from less than 100A alternator to more than 100A alternator.
Also, you need a regulator that has LiFePO4 charging algorithm as well as a temperature sensor on the alternator to prevent overheating.
For my old Yanmar I replaced the stock Hitachi with a new 170A Balmar, the pulleys and belt with a serpentine version and a Balmar regulator with temperature sensor on the alternator.

An equally advantageous strategy is to take your standard alternator. Upgrade to a regulator with battery charging profiles including lithium.

Stock car alternators and their regulators are NOT designed to charge batteries at all. They are simple constant voltage power supplies. Your car battery merely starts the engine. The alternator is then just a power source for the car.

Of course this makes then poor battery chargers poor for both SLA and LI.

All alternators can run at a given load indefinitely. In a car they do exactly that.

Hence folks for the an engineered system
1. Upgrade to a proper battery charging profile regulator , set it for an output it can maintain given the enclosure cooling limits.

2. Then directly connect it to the battery that needs charging the most. This is inevitably the domestic

3. Dc dc trickle charge using a low current cheap converter your starter from the Li.

See Cfers there are always multiple solutions

[s/v Jedi]

Originally Posted by goboatingnow

An equally advantageous strategy is to take your standard alternator. Upgrade to a regulator with battery charging profiles including lithium.

Stock car alternators and their regulators are NOT designed to charge batteries at all. They are simple constant voltage power supplies. Your car battery merely starts the engine. The alternator is then just a power source for the car.

Of course this makes then poor battery chargers poor for both SLA and LI.

All alternators can run at a given load indefinitely. In a car they do exactly that.

Hence folks for the an engineered system
1. Upgrade to a proper battery charging profile regulator , set it for an output it can maintain given the enclosure cooling limits.

2. Then directly connect it to the battery that needs charging the most. This is inevitably the domestic

3. Dc dc trickle charge using a low current cheap converter your starter from the Li.

See Cfers there are always multiple solutions

That’s what I said: “ modify or replace the alternator with a model that supports an external regulator”. You just repeat me and make it look like you bring a new option

[goboatingnow]

Originally Posted by s/v Jedi

That’s what I said: “ modify or replace the alternator with a model that supports an external regulator”. You just repeat me and make it look like you bring a new option

Nope my advice pertains to ordinary cheap 70A stock alternators. No big case pulleys or belts needed.

[s/v Jedi]

Originally Posted by goboatingnow

Nope my advice pertains to ordinary cheap 70A stock alternators. No big case pulleys or belts needed.

That is what I wrote: modify your stock alternator. Just stop twisting my words, they are clear. Bigger pulleys and belts are required when you switch from a 60-85A alternator to a 170A alternator. That is what I wrote, so when you do not upgrade the capacity of your alternator, you don’t need bigger belts.

Why are you doing this?

[newhaul]

Originally Posted by goboatingnow

An equally advantageous strategy is to take your standard alternator. Upgrade to a regulator with battery charging profiles including lithium.

Stock car alternators and their regulators are NOT designed to charge batteries at all. They are simple constant voltage power supplies. Your car battery merely starts the engine. The alternator is then just a power source for the car.

Of course this makes then poor battery chargers poor for both SLA and LI.

All alternators can run at a given load indefinitely. In a car they do exactly that.

Hence folks for the an engineered system
1. Upgrade to a proper battery charging profile regulator , set it for an output it can maintain given the enclosure cooling limits.

2. Then directly connect it to the battery that needs charging the most. This is inevitably the domestic

3. Dc dc trickle charge using a low current cheap converter your starter from the Li.

See Cfers there are always multiple solutions

I am of the other camp stock 75 amp alternator and a 50 amp b2b charger settings specific for lfp done deal . Fla start bank lfp house bank The one I am installing also has a 50 amp MPPT controller. It regulates between solar and alternator to provide up to the full 50 amps out . So with 10 amps out of my solar then the alternator will be providing 40 amps .

Yes it is from a well established company. .

Alternately I am looking at the 60 amp b2b that doesn't have the MPPT built in .

[Ballsnall]

Originally Posted by newhaul

I am of the other camp stock 75 amp alternator and a 50 amp b2b charger settings specific for lfp done deal . Fla start bank lfp house bank The one I am installing also has a 50 amp MPPT controller. It regulates between solar and alternator to provide up to the full 50 amps out . So with 10 amps out of my solar then the alternator will be providing 40 amps .

Yes it is from a well established company. .

Alternately I am looking at the 60 amp b2b that doesn't have the MPPT built in .

With a 50A DC/DC charger you might overload your alternator if you run it when you have low solar input and the alternator is cranking out 50A or 60A with the larger one. Just something to consider. My preference is to have the solar on a dedicated charger (also good for redundancy) and size the DC/DC charger to suit the alternator, in this case a 30A DC/DC charger would be appropriate.

Alternatively, your current plan would work if you added an external temperature compensated regulator.

[goboatingnow]

Originally Posted by s/v Jedi

That is what I wrote: modify your stock alternator. Just stop twisting my words, they are clear. Bigger pulleys and belts are required when you switch from a 60-85A alternator to a 170A alternator. That is what I wrote, so when you do not upgrade the capacity of your alternator, you don’t need bigger belts.



Why are you doing this?

Relax Nick. Accept other people have good ideas too even sometimes they are forms that look like yours. ! Like the eagles says “ take it easy “

[Pete7]

Originally Posted by s/v Jedi

The comments about stock alternators being incompatible with LFP charging are correct of course. Stock alternators are designed for charging LA start batteries, so a bit of charging after start, then a long time doing very little.

Also helped as the internal resistance in LA increases as they reach fully charged. We have all seen the current drop like a stone and despaired at how long its going to take.

Originally Posted by s/v Jedi

By far the best method to make this suitable for charging LFP is by leaving it all stock including the start battery, and just install a DC-DC charger like the Victron Orion Smart non-isolated 12-12 30A, configure it for alternator detection and a maximum charge current of 50% of the stock alternator. If you have a 60A or better alternator, you can leave the Orion at it’s default 30A, lower it otherwise.

Hmm, those things get hot as well, ours cuts back to 26A after a while. The computer fan install behind it is in progress at the moment.

However, I agree. Adding one little blue box from Victron gives me a heap of extra control and a circuit breaker the option of using the Orion or not, just by flicking a switch.

Pete

[goboatingnow]

Of course adding a decent regulator would do the same thing.