60a DC-DC Charger only pulling about 40a

Posplayr

Solar Enthusiast
Joined
May 27, 2021
Messages
146
many people in this board are more concerned about burning out their alternators because too much current is being pulled.
You are one of the first one's to concerned about too little being pulled.
I have no idea how you could have possibly inferred the bolded statement from what I have posted other than the fact that I have said the way to much trying to explain what seems to be too complex for the layman to understand.

I'm an EE with an advanced degree and 40 years of professional experience so I am probably "out of touch" with what the layman can reasonably understand.
 

moonlitsouls

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Joined
Jan 4, 2021
Messages
421
I have no idea how you could have possibly inferred the bolded statement from what I have posted other than the fact that I have said the way to much trying to explain what seems to be too complex for the layman to understand.

I'm an EE with an advanced degree and 40 years of professional experience so I am probably "out of touch" with what the layman can reasonably understand.
lol you're a d bag
 

Posplayr

Solar Enthusiast
Joined
May 27, 2021
Messages
146
lol you're a d bag
All the self-proclaimed geniuses here can continue living in their safe spaces of delusion; for the rest:

Alternator Considerations for LiFePO4​


22-LiFePO4-On-Boats_Alternator.jpg

If you decide on LFP, it is best designed and installed as a system. A good system design will almost always include an alternator installation that is suitably designed for that part of the charging system.

Due to the extremely low internal resistance of LFP batteries, and the extremely flat voltage curve, LFP banks can easily tax an alternator to death, if not properly installed. The high acceptance rate of LFP batteries will force the alternator to be in BULK charge mode for the vast majority of the charge cycle, (depends upon amperage/size) before even attaining absorption voltage.

With a high current alternator on lead acid, you can hit limiting/absorption voltage as low as 50% SOC where the alternator begins to catch a break. Alternators for lead acid batteries don’t always need the same level of protectiong from burning out than do alternators charging LiFePO4. With LFP your alternator simply won’t catch a break.

If you cycle the LFP bank to 80% DOD this means you are in BULK charge mode for approx 75% or more of the capacity of the entire bank bank before any sort of voltage limiting even begins.

BULK CHARGE:

This means the alternator has not brought the terminal voltage of the battery bank up to ABSORPTION or the limiting voltage. In BULK the alternator is working flat out, as hard as it can in what is referred to as BULK or CC. (CC = constant current). Once the bank comes up to ABSORPTION VOLTAGE we switch to ABSORPTION or CV (CV = constant voltage). In absorption/CV is where voltage is held steady and current begins to taper off based on what the battery can accept at that SOC and voltage. This is where the alternator finally catches a break but with LFP this duration is very short and only at teh very top of charge.

In BULK / CC the alternators capacity/ability is your limit.

In ABSORPTION / CV the battery determines how much current can flow at a specific SOC and terminal voltage.


Take a 400Ah LFP bank at 80% DOD, that means 320Ah that need to go back in. With a 130A rated alternator running hot, at about 100A, this means BULK charging will be about three hours long. There is no *small-case alternator on the planet I know of or have tested that can run at full bore for three straight hours, into an LFP bank, inside the typical engine room on a boat. *Unless the rectifier has been mounted externally with its own cooling fan.

Let’s assume you’re a marathon runner, and you can do the 26 miles at a pretty good jog. This is similar to a high capacity alternator feeding a large lead acid bank. You start out strong (BULK/CC) but as the race goes on you plateau & settle in at a sustainable pace (ABSORPTION/CV).

An alternator feeding an LFP bank is like trying to SPRINT the entire 26 mile marathon. Not going to happen….

FACTORY ALTERNATORS

Some factory alternators have a built in temp compensator and it resides in the voltage regulator circuitry to reduce current / voltage as the alternator heats up. This really defeats the purpose of “charging fast” or even having an LFP bank if you want to capitalize on the fast & efficient charging LFP batteries can offer.

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“..
 

Zwy

Photon Sorcerer
Joined
Jan 3, 2021
Messages
1,727
Location
Timbuktu
I'll do you one better. Just finished my truck inverter installation. 2200w inverter mounted in back seat area of my truck, backseat is removed for DC fridge/freezer. Alternators are one OE 105a and one aftermarket 250a. They are paralleled. 2/0 battery cable from factory underhood junction to inverter input.

AC power runs from inverter thru 10ga RV cord mounted to frame and terminates at rear bumper with a TT-30R receptacle. From this receptacle, I have a short 6 foot cord that runs to input of Growatt 24V SPF 3000TL LVM.

The GW supports up to 60 amps charging off AC power (1440 watts).

I've tested this system and it works great. I can charge at 30 amps to the battery and run the roof air conditioner with no problems, no heating of alternators or connections. Basically the alternators are just idling along.

This system not only allows for using the vehicle alternator for house battery charging but also backup power in case I have an inverter failure or BMS failure.
 
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