Thinking about installing a 60a dc-to-dc charger in our truck camper. Have plans to power it with the 220a alternator in our truck. Under a worst case scenario it could load the alternator with an additional 60a load for several hours. Any chance whatsoever it could damage the alternator with this kind of load--especially if the truck's two batteries are also discharged and pulling maximum charge current at the same time?Also have a question about how most DC-to-DC chargers operate. Is the DC-to-DC charger output voltage limited to the maximum available input voltage (produced by the alternator)? Or, can/will the DC-to-DC charger step-up the input voltage from, say, 13.9v to 14.4v if need be?

DC-DC converters can put out much higher voltages than their supply voltage.Be aware that just because your alternator is rated at 220A, it won’t always supply that much. At idle there likely won’t be anywhere near 60A available for the charger even with the vehicle batteries charged.

Anyone know how many amps a 220a alternator on a Cummins is capable of producing when it’s idling (~700rpm)? I measured 80a of charge current about a year ago when the batteries were discharged quite a bit.

Your going to have to measure that one for yourself for your vehicle.It will vary a lot depending on battery age and condition, the temperature of the alternator and air around it and what accessories may be running.Generally, the alternator is "geared" to run just fast enough to handle typical operating loads at idle like engine electronics, lights, fan and perhaps A/C without drawing the battery down..Just because it may be a "220A" alternator, doe not mean it can and will produce all 220A at idle OR for LONG PERIODS OF TIME..It is intended to provide short intermittent bursts of current to cover spikes like your power windows and such. We are talking seconds to a few minutes, not hrs of heavy use.

I've been researching this myself. I have been looking at Redarc DC to DC chargers. Etrailer has a lot of information on installing which you may find helpful.

dccamper wrote:I've been researching this myself. I have been looking at Redarc DC to DC chargers. Etrailer has a lot of information on installing which you may find helpful.Renogy has a 50 amp for a lot less money than the Redarc 60 amp.

60a DC-to-DC Charger Powered by 220a Alternator

43 Replies

Gdetrailer
Explorer III
Jan 11, 2021
Your going to have to measure that one for yourself for your vehicle.

It will vary a lot depending on battery age and condition, the temperature of the alternator and air around it and what accessories may be running.

Generally, the alternator is "geared" to run just fast enough to handle typical operating loads at idle like engine electronics, lights, fan and perhaps A/C without drawing the battery down..

Just because it may be a "220A" alternator, doe not mean it can and will produce all 220A at idle OR for LONG PERIODS OF TIME..

It is intended to provide short intermittent bursts of current to cover spikes like your power windows and such. We are talking seconds to a few minutes, not hrs of heavy use.
otrfun
Explorer II
Jan 11, 2021
Anyone know how many amps a 220a alternator on a Cummins is capable of producing when it’s idling (~700rpm)? I measured 80a of charge current about a year ago when the batteries were discharged quite a bit.
jkwilson
Explorer III
Jan 11, 2021
DC-DC converters can put out much higher voltages than their supply voltage.

Be aware that just because your alternator is rated at 220A, it won’t always supply that much. At idle there likely won’t be anywhere near 60A available for the charger even with the vehicle batteries charged.

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60a DC-to-DC Charger Powered by 220a Alternator

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