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These are the charging rates I have seen with an alternator-battery direct hookup to a 240Ah LiFePO4 battery. In the first case the cables/fuses/connections/shunt add up to around 10mR and in the second case the addition of a resistor bumps it up to around 20mR. The voltage from the alternator...

So far only 4 months on a 220 amp alternator -> 240Ah lifepo4 house battery. This has been winter so batteries have been in the 5-15C range. Resistance between vehicle battery and lifepo4 is 9mR. the peak charge rate I have seen is 160A at a 25ish percent state of charge (at idle!). Usually it...

As the voltage on the cells rises the difference between the alternator voltage and cell voltage drops. This leads to the drop in charging current. I used some cell voltage vs. state-of-charge vs. charge rate data to estimate the current trend and it matched quite well. Of course, I dumped the...

That is a good sized battery! Are these alternators hooked up together for 440 amps?!? I'd lean towards the bms controlled relay between the starter battery and the lithiums. That said, I don't know what start-stop parameters your bms will allow. If it has a cell based high voltage cutoff...

I like the idea of having a resistor reserved for worse case scenarios. If there actually is a danger of overloading the alternators (endlessly debatable) it only exists between 0 and maybe 10% state-of-charge. After this the rising battery voltage should limit the amps to a reasonable level. If...

Yep, the power required to charge the batteries is trivial compared to a cars engine! In my case, putting away almost 200Ah in a couple hours of driving is great and one of the main reasons I upgraded to lithium in the first place! A 40 amp DC-DC charger would almost be a downgrade to my old...

Fortunately, the voltage drop is proportional to the amps flowing. As the batteries increase in voltage the current drops, resulting in a lower voltage drop through the system. I have not had any issue hitting my high voltage cutoff at the end of charge.

It is not so good if you aren't around, but we've used a Mr Heater as both emergency heat and as a very pleasant source of radiant heat when we manage to get a chill.

I don't know where in a modern vehicle the alternator is controlled. You are right though, if you could trick the controller into seeing a different voltage you could take control of the alternator output voltage. The logical step to full alternator control seems to have been taken by Wakespeed...

I totally agree. I think of the resistor as ideal in the sense that if you want to limit current it is simple, cheap, and (with the flat voltage profile of lifepo4) should provide a fairly constant current to the batteries. So far I haven't had any issues with my straight 'non-throttled'...

I pondered this for a while for my van. I was putting in a 240Ah Lifepo4 to replace a pair of golf cart batteries. I looked at several dc-dc chargers but decided to test the current alternator-switch-battery setup that I had. Based on limited use it has not been an issue charging directly from a...

The battery is a 240Ah unit made up of 120Ah cell pairs (2p4s)? I wanted some redundancy! I suspect the alternator has protection BUT the voltage at the van battery has been more or less constant during charging, so the alternator has not entered any protection mode. The one time I saw 160...

I have followed Rod Collins' (Marine How To) advice on lifepo4 charging. He strongly asserts that with these cells the charger must STOP after achieving full charge. Unlike lead acid you aren't just boiling off water if you continue. You are permanently damaging the battery if you continue to...

Yup, this is exactly what I have seen. The 9mR resistance between the van battery and house battery keeps the charge rate at 80-100 amps and the increased 20mR setup is keeping the charge rate at 40-50 amps (so far). In both cases the 220 amp alternator has not dropped it's voltage. I do see a...

If you have 'giant alternators' maybe you can comfortably skip adding extra resistance? However, If your battery pack is massive then you might end up hoping the alternators can protect themselves. The current path to my batteries includes around 10 feet of 1 gauge, a dab of dual 6 gauge, a...

I purchased 8 120 Ah cells this summer for a 2p4s. I bottom balanced them at 2.80 volts. After charging the pack at 12 amps to a total of 238 Ah they settled down to 3.34 volts per cell. Based on this I am very happy with them! The voltages do diverge somewhat during charge/discharge but then...

We found that when it was plenty cold outside we would still freeze parts of the van with the thermostat set to 40F. We bumped the base temperature to 50F which largely solved it but when it goes to -30F the edges of the van still freeze (2" rigid foam insulation all around). If the batteries...

I ordered from Dongguan Lightning on July 18, shipping via slow boat to Calgary. The cells just arrived today which makes it 104 days. The UPS number never tracked.

Sorry, this isn't a proper reply to your question but how about 'just' using MOSFETs and skipping their control circuitry? If you have a control signal to drive the gates you should be able to make up a simple PCB containing a MOSFET and possibly a protection diode. The great thing is that they...

Sounds like you have it covered! Some sort of way to heat them up in place if things go sideways would be nice but you might be just fine for a 'normal' winter.

Yup, I hear you. If you need to protect against reverse currents this will fail, similar to the melting Victron BPs I imagine. In my case I had to use some additional circuitry to get a solid 0 (on) to 13V (off) signal to control the PNP MOSFETs. If you have a BMS that can pull this off for you...

I had the same issue with a cheap gopower inverter leading to a DIY current monitor. Similar (but different!) to Cal's solution I added an RC filter between the shunt and monitor inputs which will average out the signal. I used 4.7k resistors followed by 10uF capacitors shorted to ground...

I love back of the envelope calculations, especially when they work!

I used silicone heating pads that adhere directly to the cells (AliExpress etc...). They had built in thermistors so you could track the temperature of the pads themselves in order to keep the outsides of the cells from getting crispy. However, I ended up wiring 4 pads in series which resulted...

The more I look at the AliExpress picture the more confused I am. If this is actually an N-channel IPT015N10N5 MOSFET why is it shown here as a high side switch? The Drain is labelled Out(+) and the Source is labelled In(+)! In that case wouldn't it simply conduct via the MOSFET body diode? What...

Mine took 104 days by sea. The tracking number never tracked, which kept up the suspense.

This is the way I do it and it has handily kept the current around 70-80 amps into a 240Ah battery. It's trial and error as far as the wiring goes. I think one thing to keep in mind is that if you draw the batteries right down, say to 12 volts, the initial charging current could be quite high (I...

That is plenty to maintain a temperature. My four pads at 10W each warm the batteries 30F in a couple of hours. This is for 8 120A cells in a 2" foam enclosure.

I thought I'd throw this out there since if it happened to us it will probably happen to someone else. We noticed a low charge rate of 20 amps to the 240Ah LiFePO4 house batteries in our Ram Promaster (100A is more typical). This coincided with a check engine light. A multimeter showed around...

Whoops! Made irrelevant comments. Deleted to save confusion.