DC DC Charger for 100amp alternator

[MarcMassanari]

I have bought the Renogy DC DC Dual MPPT charger. I now understand its limits. Mainly cannot take more than 25v from solar. No big deal, I will rewire my panels so to yield 20v instead of 40v. BUT, what about charger from engine? My engine has a 100amp alternator. Most DC DC charger limits charger input to less than 1000w. What should I do??

 

[featherlite]

I commend you for asking questions before you proceed. There are many helpful discussions on the forum that can be found using the search function, including this helpful discussion that popped up with my search:

https://diysolarforum.com/threads/dc-to-dc-charger-size-questions.29692/

Do some study and report back. There are many people here who will help you.

 

[time2roll]

Not sure what the other alternator loads are but the DC-DC charger can pull 50% more than the output rating. I recommend 10 amps output and possibly 20 amps depending on load and use.

 

[mikefitz]

My engine has a 100amp alternator.

At idle speed the output will be , at best, 70 amps. Since the DCC50 50 amp output will take , say 60 amps from the vehicle, its probable the alternator will be overloaded.
Options are to replace with a DCC30, or add additional DC to DC charger for the alternator charging, a 20 or 30 amp unit.

Mike

 

[mikefitz]

DC-DC charger can pull 50% more than the output rating

Seems on the high side for most installations, however, low alternator output and/or less than ideal cables, breakers, fuses, interconnections, could reduce the DC to DC input volts, thus requiring more current. Experience suggests that the DC to DC charger would ramp down the output in this situation to protect itself from overheating.

Mike

 

[Reed Cole]

Sterling dc-dc chargers are rated by how much current they draw, rather than output. So their 30A model outputs ~22A. If changing equipment is feasible

 

[time2roll]

OK and the OP just bought a Renogy. I only see one with MPPT.

Specifications here: https://www.renogy.com/renogy-12v-24v-ip67-50a-dc-dc-battery-charger-with-mppt/

Seems a bit much for a 100a alternator unless there are virtually no other loads. Maybe there are some programming adjustments.

 

[mikefitz]

a Renogy. I only see one with MPPT.

DCC50S 12V 50A DC-DC On-Board Battery Charger with MPPT

Make sure your service battery has all the juice it needs with Renogy's DCC50S DC-DC MPPT On-Board Battery Charger. 10% off: Renogy10off. Free shipping

www.renogy.com

DCC30S 12V 30A Dual Input DC-DC On-Board Battery Charger with MPPT

Designed to give you options, the Renogy 30A Dual-Input DC-to-DC MPPT On-Board Battery Charger can charge a service battery in two different ways. The multi-stage charger can utilize connected solar panels or an alternator linked to a starting battery. While your vehicle's alternator prioritizes...

www.renogy.com

Renogy also have DC to DC without MPPT, 20, 40 and 60 amp versions,

12V 20A/40A/60A DC to DC On-Board Battery Charger

Charge your secondary batteries on-the-go with Renogy's 12V 40A DC-DC On-Board Battery Charger. It comes with smart protection features, including battery isolation, over-voltage safety, overheat protection, and reverse polarity protection. Order yours today.

www.renogy.com