Alternator and LiFePo battery question

S Davis wrote:

Teleman wrote:
The Redarc also has an MPPT controller. I'm planning to add 600 watts of solar. I upgraded to LiFePo to charge the big batteries on our E-mtbs. Between the driving and solar I think we'll be fine.

I am going to add a second dedicated alternator and plan to have three of the 50 amp Redarc, two on the truck for two 280ah LifeP04 and one in the truck camper to charge one 280ah LifeP04. I talked to Redarc and they said you could parallel up to four.

why would use 2 280ah for the truck portion?

LittleBill wrote:


i also still have not read of someone burning out an alternator on here from charging.

It has been mentioned on some boating forums.

pianotuna wrote:

LittleBill wrote:


i also still have not read of someone burning out an alternator on here from charging.

It has been mentioned on some boating forums.

their environment is completely different then ours. Their engine rooms are significantly hotter, 0 ventilation. etc not even close to an apples to apples comparison

I've now got two externally regulated 120 amp alternators feeding two separate battery banks over thick cabling.

I pick and choose the voltage with external adjustable regulators with potentiometers on my dashboard, and have ammeters showing not only total alternator output but amperage the battery banks are accepting, and of course dual decimal voltmeters with sense leads on battery terminals.

I've also have voltmeters on the Field wires from regulator to alternator, and K type thermocouples on the alternators casings.

Maxed out at 50 amps hot idle, parked and the alternators get HOT quickly, as does the external voltage regulator, however at 75 amps output when moving above 25mph, they stay far cooler. Below 25mph and low engine rpms is not much better than idling parked. At 65 mph, both alternators can be nearly maxed out in the 120 amp range, and stay 155f or below, but stop at a traffic light, 50 amps max, and 220 f happens in 30 seconds or less and I have frantically lowered voltage to keep them from exceeding this, as My thermoucouples are on the exterior casing, the rectifier/ Diodes likely much hotter

Obviously underhood airflow, and alternator fan rpm have HUGE effects on alternator temperature, as of course does the load, and these are all huge variables on vehicles making direct comparisons without supporting data, and blanket statements devoid of specifics, filled with unknowns, unwise.

The voltage regulators, which are behind my dashoard, with extra heatsinking and 60mm fans attached get hottest at hot idle, low rpms. thats when field voltagwe is just shy of battery voltage. Maxing out at higher rpms field voltage is not as high and the regulators do not get as hot.

Those alternators with voltage regulators inside the alternator have that added heat load, and idling maxed out is likely even harder on them.

In the past, before I have had failed alternators which smelled like burnt varnish.

I've got a plans to force feed my alternators cold air from outside engine compartment, for when I need their full output, when parked, which admittedly would be infrequent, unless.........

landyacht318,

Nice set up!

LittleBill wrote:

S Davis wrote:

Teleman wrote:
The Redarc also has an MPPT controller. I'm planning to add 600 watts of solar. I upgraded to LiFePo to charge the big batteries on our E-mtbs. Between the driving and solar I think we'll be fine.

I am going to add a second dedicated alternator and plan to have three of the 50 amp Redarc, two on the truck for two 280ah LifeP04 and one in the truck camper to charge one 280ah LifeP04. I talked to Redarc and they said you could parallel up to four.

why would use 2 280ah for the truck portion?

Installing a 2800 watt inverter for work tools on remote job sites.

landyacht318 wrote:
. . . Obviously underhood airflow, and alternator fan rpm have HUGE effects on alternator temperature, as of course does the load, and these are all huge variables on vehicles making direct comparisons without supporting data, and blanket statements devoid of specifics, filled with unknowns, unwise . . .

Useful, realworld info in your post. Thanks. We were tempted to squeeze more out of our 220a alternator with a larger dc to dc charger or a straight charge line, but decided against it. Probably would have been fine for the most part. However, your post would seem to confirm some of the concerns we had with the possibility of extended idling in stalled freeway traffic in 110+ degree heat, while forgetting we had a very high charge load going to our camper batteries.

We've already encountered limitions with our Ram's 220a alternator and 40a dc to dc charger in cold temps. Our Ram recently went into "Battery Saver" mode one 5-10f morning after a night of dry camping (and depleted camper batteries). Turned off our 40a dc to dc charger and the warning went away. Waited an hour or so to get a better charge on our truck batteries, then turned the dc to dc charger back on. All was well again.

I wonder what triggers 'battery saver mode' in a modern Ram. Does it have a ring sensor on a battery cable?

I've added hall effect ammeters to my engine compartment battery, one on feed from alternator +, and the other on the ground cable, but they said something like a 140F maximum temperature for the sensor, which helped inspire me to insulate the battery ( group 31 Northstar) from underhood engine heat and ventilate it to outside engine compartment.
My K type sensor in free air above battery rarely goes 2f above ambient. On engine shutdown the sensor just outside the battery enclosure hits 145f and takes an hour to fall below 100f, where the sensor inside enclosure was 72f the whole time on a 70f day. At speed that sensor is basically same as ambient.

My other battery bank are 2 Deka intimidator gc-2's that I pulled from a boat at 4 years old, which got new Lifelines, and while they together, have much lower cranking amp rating than the single group 31 Northstar, can still accept well over 120 amps when well depleted, as does the Northstar. The 50 amp charge limit on many drop in Lithium batteries is a bit of a deal breaker for me, with a system designed/optimized for fastest possible recharging of lead acid.

Obviously the time my existing batteries could max out an alternator is limited. I do want to be able to run a 1600 watt tablesaw from my System. I want the alternator's to be feeding ~1200 of that load, but this is when they get the hottest, Idling maxed out, parked. Only in drive foot on the brake is worse regarding heating.

I don't really have the need to do this now, nor the inverter that could power it anyway, only the desire for such capability.

While boat engine rooms are usually not greatly ventilated, at least their radiators and AC condensers are not contributing to the heatload in the engine room, like on a vehicle sitting in traffic on a 100f day.

I once made a powerpack with a 125Ah lifeline gpl-31Xt as the heart, and used 1/0 gauge cable from 2013 Rams' alternator + stud to it and ground cable to alternator mounting bolt. not sure the amp rating of that alternator but after several minutes of 100+ amps into the depleted lifeline, the alternator at idle, with hood up, shot with an IR gun was 220F, and stayed there as the voltage was lowered.

There is a difference in my vehicles rpm with it in gear, foot on the brake, as opposed to in park or neutral, that 75rpm difference in rpm makes for a significant difference in heating and output.

I've not really tested both alternators at max output into both battery banks when depleted. Generally one bank or the other is full.
I still have V belts and one chrysler alternator, and one Nippondenso. The ND alternator has 2mm more distance between the belts, and even though I got the alignment pretty good, I want the separation between belts on the ND alternator to match the Chrysler alternator and crank pulley before trying to acquire matched V belts.

My existing single V belt, is from before I removed AC compressor and replaced it with second alternator. When I did this, I found the original alternator location had its pulley 6mm out of parallel alignment with crank pulley and ac compressor pulley, yet I was still able to max out that alternator at 122 amps with just a single v belt, though if damp and cold it would slip and squeal.
I often crank my voltage regulator to about 13.2v before shutting down engine, when I know the alternator the next morning will be maxxed out feeding a depleted battery. If I dont then squealing is guaranteed until I crank down the voltage. I also like to let the engine oil circulate for a bit before the alternator adds the 2+ HP load to the engine.
My voltage regulators are switched on by oil pressure, the original VR inside engine computer is tricked with a resistor into thinking it is still attached to alternator. Other wise check engine light illuminates and engine runs crusty. I also have to keep voltage below 14.8v as 30 seconds of 14.81v will illuminate it.