LFP alternator charge, LA-dc2dc in which order

[Ballsnall]

Originally Posted by newhaul

How about spend all that extra money saved wrt special alternator belt kit and external regulator ., on improving solar capability .

I am considering an improvement by adding 2 200 watt panels for just over 300 they are only 1480mm long by 680mm wide. So not any wider just longer by 18 inches than current 100 watt pair . Will give me 300 watts at 24 volts tto charge my 12v lfp via my mppt .

Seems more and more sailors are relying on solar as their primary charging source which moves the pendulum more towards investing in solar systems and battery capacity as a better investment than engine charging systems.

[SOLAR SUPPORT]

If many people use the [C] option as a solution and do not encounter any problems for a long time, can we say that the dc2dc solution is economical and trouble-free?

For example, let's consider an LA battery connected in parallel between a dc2dc with a capacity of 30-40A operating in the [C] array. Perhaps the electrical dump loads that occurs in the alternator during the HvCutoff action of the bms can be absorbed even if the LA battery is full.

For example, if a dc2dc operating at a larger capacity in the same array had a capacity of 60-80A, would it be sufficient to increase the dimensions of the LA battery to avoid these dangerous electrical loads?

If there is a real danger, it is necessary to take realistic and effective measures. If the dc2dc manufacturers didn't even think about this as much as we did, I think there is a risk.

[newhaul]

Originally Posted by SOLAR SUPPORT

If many people use the [C] option as a solution and do not encounter any problems for a long time, can we say that the dc2dc solution is economical and trouble-free?

For example, let's consider an LA battery connected in parallel between a dc2dc with a capacity of 30-40A operating in the [C] array. Perhaps the electrical dump loads that occurs in the alternator during the HvCutoff action of the bms can be absorbed even if the LA battery is full.

For example, if a dc2dc operating at a larger capacity in the same array had a capacity of 60-80A, would it be sufficient to increase the dimensions of the LA battery to avoid these dangerous electrical loads?

If there is a real danger, it is necessary to take realistic and effective measures. If the dc2dc manufacturers didn't even think about this as much as we did, I think there is a risk.

Let's see a FLA battery that can supply up to 1000 amps at up to 15 volts . Yes I can easily handle a millisecond burst at 80 to 100 amps at 15 volts . It easily operates as a capacitor dump load.

[Ballsnall]

Originally Posted by SOLAR SUPPORT

For example, if a dc2dc operating at a larger capacity in the same array had a capacity of 60-80A, would it be sufficient to increase the dimensions of the LA battery to avoid these dangerous electrical loads?

If there is a real danger, it is necessary to take realistic and effective measures. If the dc2dc manufacturers didn't even think about this as much as we did, I think there is a risk.

80A DC/DC is not realistic for a stock alternator, I think a 30A charger is what most use to leave some headroom for charging the FLA but yes a FLA will handle any dump even at 80A.

Not sure what risk you are referring to, alt damage?
Worst case a blown diode maybe. If you want to charge at 80A constant then you will need to update to a high output alternator.

A FLA in parallel with a lifepo4 bank is sometimes used as cheap BMS disconnect protection.

[Pete7]

Originally Posted by newhaul

How about spend all that extra money saved wrt special alternator belt kit and external regulator ., on improving solar capability .

I am considering an improvement by adding 2 200 watt panels for just over 300 they are only 1480mm long by 680mm wide. So not any wider just longer by 18 inches than current 100 watt pair . Will give me 300 watts at 24 volts tto charge my 12v lfp via my mppt .

Exactly. GBN assumes that everyone is using the engine to provide the majority of charging, well we certainly don't, solar does.

Like you we have just upgraded, from 300w to 600w to enable more electric cooking and possibly water heating in due course.

[Pete7]

Originally Posted by Ballsnall

80A DC/DC is not realistic for a stock alternator, I think a 30A charger is what most use to leave some headroom for charging the FLA but yes a FLA will handle any dump even at 80A.

A FLA in parallel with a lifepo4 bank is sometimes used as cheap BMS disconnect protection.

We have a hybrid FLA and LFP parallel house bank charged from the engine start AGM, then through a DC>DC charger to the hybrid bank, which does a bit more for us. Agreed that 80A off a stock alternator isn't going to last long, our DC>DC is an Orion at 30A, perfectly adequate to meet our needs for occasional engine charging.

The hybrid bank does a couple of other things for us too. Yes in the event of a BMS disconnect, the LA will provide power to the CP, VHF and lights etc. However, it also means we can have the bilge pumps on when not on board charged by solar, but with the LFP isolated. This means they aren't constantly being float charged a good thing. The LFP has been sitting at 61% for the past 2 months quite happily disconnected.

Pete

[newhaul]

Originally Posted by Ballsnall

80A DC/DC is not realistic for a stock alternator, I think a 30A charger is what most use to leave some headroom for charging the FLA but yes a FLA will handle any dump even at 80A.

Not sure what risk you are referring to, alt damage?
Worst case a blown diode maybe. If you want to charge at 80A constant then you will need to update to a high output alternator.

A FLA in parallel with a lifepo4 bank is sometimes used as cheap BMS disconnect protection.

Actually I can get a 120 amp stock chevy internal regulated alternator that can easily push 80 amps constant.
They are available

[Pete7]

Originally Posted by newhaul

Actually I can get a 120 amp stock chevy internal regulated alternator that can easily push 80 amps constant.
They are available

Yes, but do you need to? Would a smaller alternator and DC>DC suffice and save money for other things like more solar?

Pete

[newhaul]

Originally Posted by Pete7

Yes, but do you need to? Would a smaller alternator and DC>DC suffice and save money for other things like more solar?

Pete

I agree and iirc that is what I posted . My statement was on response to another poster .

I myself will be running a 75 amp alternator and a 40amp b2b . Plenty sufficient for topping in the morning . On the way out of the Anchorage.

[Pete7]

I make your new solar installation 600w which should be good

What are you using the extra power for?

Pete

[newhaul]

Originally Posted by Pete7

I make your new solar installation 600w which should be good

What are you using the extra power for?

Pete

Just cause. Seems a quieter choice than my air x 400.

[s/v Jedi]

Originally Posted by newhaul

Just cause. Seems a quieter choice than my air x 400.

I have used a 660W (6x 110W Shell panels) for 15 years. After that time I still saw 600W on a good day so 10% decline but also 10 years to go on a warranty of 80% still available.

The 600W is great for a DC boat with propane galley

[Pete7]

Originally Posted by s/v Jedi

I have used a 660W (6x 110W Shell panels) for 15 years. After that time I still saw 600W on a good day so 10% decline but also 10 years to go on a warranty of 80% still available.

The 600W is great for a DC boat with propane galley

Ah, well we are trying to reduce the use of gas. This summer we were getting between 4 and 4.6x the panel wattage in sunny conditions. So could be looking at 2.4Kwh which should be fine. Know more next summer.

Pete

[Ballsnall]

Originally Posted by Pete7

We have a hybrid FLA and LFP parallel house bank charged from the engine start AGM, then through a DC>DC charger to the hybrid bank, which does a bit more for us. Agreed that 80A off a stock alternator isn't going to last long, our DC>DC is an Orion at 30A, perfectly adequate to meet our needs for occasional engine charging.

The hybrid bank does a couple of other things for us too. Yes in the event of a BMS disconnect, the LA will provide power to the CP, VHF and lights etc. However, it also means we can have the bilge pumps on when not on board charged by solar, but with the LFP isolated. This means they aren't constantly being float charged a good thing. The LFP has been sitting at 61% for the past 2 months quite happily disconnected.

Pete

Sounds like a well thought out set-up which effectively addresses the main issue of over charging especially when steaming long distances or in you case when not in use .

[newhaul]

Originally Posted by s/v Jedi

I have used a 660W (6x 110W Shell panels) for 15 years. After that time I still saw 600W on a good day so 10% decline but also 10 years to go on a warranty of 80% still available.

The 600W is great for a DC boat with propane galley

I'm building for low solar in winter considering my cruising area crosses the 48°N to 55°N region