So What do I do with my big alternator?

[Makr0]

Hey folks

I’ m struggling with my install plan with my Balmar xt 250 and a wakespeed ws500.

I have a 1200ah lifepo4 house bank(my boat came with all propane and tubing completely removed. Stubbornly I hung my hat on an electric Galley.. It’s great but power hungry.

The bank allows us to live normally for about 5 days or 10 if we stretch it but inevitably we have to turn the engine on to recoup serious power, but my current alternator setup only nets me 40 amps of charging. At 20% soc that’s 25 hours to get full again.

What is my best option prioritizing my house bank?

The best I’ve come up with is I connect the Alternator (via the WakeSpeed Controller) directly to the house bank and then a DC to DC charger back to my starter battery?

Is that a solid plan or is there a better way?

Thanks for any help

[Wotname]

If you can fit both alternators then small one direct to Start Battery and big one to House Battery.

If you can only fit one, then big one to House and DC-DC to Start as you have suggested.

[smac999]

Yes but it’s a bit of a gamble. If that is your only means of charging. (No gen, no big solar). Then carry a spare alt.

But there is certainly no point having a 250a alt feeding the eng bat with a small Dc to dc going to house. Which I’m guessing you have now. The other option is stacking Dc to dc converters From engine to house. For more current.

Do you have an external bms or Internal?

[RaymondR]

What's wrong with just having a battery selector switch?

[noelex 77]

Originally Posted by Makr0

I have a 1200ah lifepo4 house bank(my boat came with all propane and tubing completely removed. Stubbornly I hung my hat on an electric Galley.. It’s great but power hungry.

This is unfortunately becoming a common problem. Cruising boats are removing their propane system and then finding they don’t have enough charging input to for electric cooking, especially when cruising areas of poor solar insolation. Electric cooking is fantastic, but make sure you have enough charging capacity before removing the propane completely.

Originally Posted by Makr0

Hey folks
The best I’ve come up with is I connect the Alternator (via the WakeSpeed Controller) directly to the house bank and then a DC to DC charger back to my starter battery?

The problem with this system is that if the BMS shuts down the batteries while the engine is running, the alternator is very likely to be damaged and there is also some risk to all other electronic components.

If you have an external BMS this can potentially send a message to Wakespeed to shut down the alternator output before the batteries are disconnected. I am sure someone on the forum can help you set this up if it is feasible with your batteries. This will protect the alternator and also prevent risk of damage to other electronics. There are other simpler solutions such a lead acid battery bank buffer or stacking multiple DC to DC chargers, but each of these has some drawbacks.

This thread is well worth reading:
https://www.cruisersforum.com/forums...nks-65069.html

[sailorboy1]

Originally Posted by Makr0

The best I’ve come up with is I connect the Alternator (via the WakeSpeed Controller) directly to the house bank and then a DC to DC charger back to my starter battery?

Is that a solid plan or is there a better way?

Thanks for any help

I am not expert! But I see no reason not charge directly to the LFP HOuse (I do it)

I don't understand why people limit their alternator charging to LFP house batteries by sending it through a DC to DC charger. Is not your alternator regulator programable? Change the regulator programing to a voltage safe for the batteries and a safe alternator temp so it doesn't burn up. I am using a old Balmar ARS5 regulator and just set the charge bulk to only 14, the belt manger to B$ to reduce the output and not burn out the alternator or belt, and the temp to 95 (it has not gotten close)

[CharlieJ]

@noelex_77 #5

The problem with this system is that if the BMS shuts down the batteries while the engine is running, the alternator is very likely to be damaged and there is also some risk to all other electronic components.

The WS500 accommodates a BMS rescinding the ATC permission with a 2 second delay between loss of ATC signal, which terminates field current, and the battery bank being isolated.

[Indolent58]

Originally Posted by CharlieJ

@noelex_77 #5

The WS500 accommodates a BMS rescinding the ATC permission with a 2 second delay between loss of ATC signal, which terminates field current, and the battery bank being isolated.

True, but that function is really only available for systems using an external BMS. Most Lifepo4 installation are using internal BMS batteries with either bluetooth-only or no external communication capabilities. One possible solution is the Balmar APM-12 alternator protection module which seems to have been designed specifically to address the problem of BMS cutoff damaging the alternator. It was released last year but I haven't seen much discussion or reviews of the unit. I would assume however that Balmar knows what they are doing. I ended up not using it for my install because I elected to leave the 80 amp stock alternator in place and charge the house bank via DC-DC but if I decide to upgrade the alternator later I would want to try it.

[jt11791]

Originally Posted by noelex 77

The problem with this system is that if the BMS shuts down the batteries while the engine is running, the alternator is very likely to be damaged and there is also some risk to all other electronic components.

Wouldn't the DC-DC charger still be taking current and therefore protecting the alternator?

This fear gets posted in nearly every LFP thread and I've yet to hear of it happening to anyone.