Alternator DC/DC converter spec

Just a quick question, I read that it's not possible to connect my alternator directly to my Tracer BN Series 40a
I'm charging 4 280ah lithium cells in a 12v configuration.
The alternator is 90a, what size DC-DC converter do I need for this?
Can you recommend one?

Thanks in advance

An mppt charge controller is, basically, a fancy DC to DC converter (a one-way converter).
The MPPT wants a rather higher voltage range than what an alternator would put out(8-32V for the tracer).
In addition, the output in an alternator is not a pure DC waveform, so what you probably want is a power supply conditioner.
Those crazy car audio people that like to produce hearing loss hazards probably convert poor quality alternator power into massive amounts of clean DC all the time.
Keep in mind your alternator may not be able to handle your normal load PLUS charging a larger battery pack with a low resistance (you could burn out your alternator).
it may be worth while to visit some car audiophile boards as well...
As long as the power is a clean DC output, your tracer has no idea if its a panel, or, well, anything else.

SECOND that ?

Surely some of them are using some form of Lion by now. Since the voltage you need can't be produced by the alternator, you need a DC-DC device that acts as a current to voltage converter. Victron makes one, it isn't cheap but it works.

Use the Victron B2B charger without a MPPT controller in the loop, MPPT controllers are designed to use a soft source of power, batteries are not a soft source of power. MPPT controllers are buck-boost converters but they are not designed to do what you suggest

90 amp alternator? I would go with 20 amp DC-DC charger. Depending on voltage supply etc it could take up to 30 amps to drive the charger and that is 1/3 of the alternator power. I would not go higher. Yes it could take a long drive to fully charge a low 280 Ah battery on 20 amps. Best to supplement with solar.

Yup one of the smaller Victron DC/DC chargers would be best, could probably get away with the 12/12-30 but the smaller ones more than likely best especially if you have a newer Van/RV that’s got an ECU and electric fuel pump etc

Some small controllers measure dc current from the panels on the negative dc input wire and the dc output on the negative wire so grounding both wires disturbs the controllers measurement of current. You cannot ground both the input and the output to charge the battery, My old tracer 3215 warned about that but my knowledge of those is way out of date, I use MidNite for too long to remember those older controllers now

drifty325i said:

Yup one of the smaller Victron DC/DC chargers would be best, could probably get away with the 12/12-30 but the smaller ones more than likely best especially if you have a newer Van/RV that’s got an ECU and electric fuel pump etc

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Thanks for this, I'm converting an old Sprinter 2008. I think it has an upgraded alternator as it used to run a dual battery system in a previous life as a euro master van. I wonder do Renology do an equivalent?

Alternator to B2B ratio, for marine applications, is about 50-60% of the alternators rated power. The Sterling Power BB1260 (12V 60A) may be a bit too large (would depend on the quality of OE the alternator and on-board loads). The other options would be the Sterling Power BB1230 (12V 30A) or a Victron Orion TR Smart 12V 30A... Both the Sterling and the Victron can also be run in parallel, if the alternator can handle it, on-top of the other DC loads. They are both also custom programable for LiFePO4.

On Renogy, we have already had five of their DC to DC chargers need replacement due to failures.. Renogy is nothing more than a sticker application "brand" slapping their logo on some of the least expensive products they can source. They used to answer the phone, and stand behind the products, but over the last year this has gone completely into the gutter. We now just toss it in the trash and replace it with a known quality product...

huwmcgregor said:

Just a quick question, I read that it's not possible to connect my alternator directly to my Tracer BN Series 40a
I'm charging 4 280ah lithium cells in a 12v configuration.
The alternator is 90a, what size DC-DC converter do I need for this?
Can you recommend one?

Thanks in advance

Click to expand...

I would recommend a Renogy 20A DC-DC Charger. They are approx $100 and do a good job for me.