50A alternator to 60A dc2dc charger

[freshalaska]

If my alternator is putting out 50 amps into my start bat. And my dc2dc charger start bat to house is rated 60 amps, Will my start bat become depleted?
The reason I have this dc2dc charger is to not over work my alternator and it’s programmed to charge my lithium house bank properly. Hope I’m explaining this clearly.
So do you think.

 

[O C Diver]

I think you will have a problem unless your house bank isn't very low. You are probably going run your alternator into an early grave, let me explain why.

An alternator is a poor battery charger with a stock interal regulator. That's why many (including myself) use an external regulator to increase the voltage to get the alternator to charge the battery faster. With a stock internal regulator, the alternator is designed to satisfy all loads on the electrical system and put some amps back in the battery. Your DC to DC charger is a load on the electrical system that exceeds the alternator's capacity. So until the DC to DC charger reduces the output, the alternator will be running flat out. The other consideration is that none of this will take into account other electrical loads while charging the house bank.

Don't know if the DC to DC charger is programmable to reduce the output, but otherwise I think you're going to cook the alternator. Probably time to consider upgrading the alternator.

Ted

 

[freshalaska]

I don’t think I’ll cook my regulator as it’s a 100 amp deregulated to 50 amp.

 

[O C Diver]

I don’t think I’ll cook my regulator as it’s a 100 amp deregulated to 50 amp.

Do you mean your alternator? Are you saying the regulator only allows the alternator to put out 50 amps?

Ted

 

[freshalaska]

Yes my mistake yes the alternator is deregulated from 100 amps to 50 amps with a alternator temperature sensor. Balmar regulator and alternator.

 

[O C Diver]

Well if that's the case, run everything off the house battery (except the engine), set the alternator back to 100 amps, and the DC to DC charger will become your amperage limiter as it only draws 60 amps.

Ted

 

[Jeff F]

You should be able to set minimum source voltage on the charger that will protect against discharging the source battery. If the voltage falls below the specified value charging turns off.

How is your charger configured to turn on? If it's voltage based you should be protected.

Sent from my moto g play (2021) using Trawler Forum mobile app

 

[Marco Flamingo]

I'm not sure that you will get your money's worth out of a 60A DC2DC. My 100A Balmer puts out a realistic 55A when controlled by the external regulator with semi-conservative settings. That 55A going to LA will then "spill over" to the lithium through the DC2DC. But I think that the LA will continue to rob a little of that through a trickle charge. And the DC2DC sending 13.6V at the LA to charge (14.5?) lithium is going to lose some. On a good day you might send 40-45A to the lithium. So why bother with a 60A DC2DC?

I find it a little confusing that advertisements, articles, and posts about DC2DC refer to "start" batteries and "house" batteries. That is a common usage for the product, but can get confusing. I think of "primary" batteries spilling over into "secondary" batteries. "Spilling over" is probably also wrong as the beauty of DC2DC is that a "full" LA primary (12.6V) doesn't just spill into lithium. The DC2DC can "pump up" a lithium secondary to 13.4V (at a cost).

The most common criticism I found of DC2DC chargers were claims that they didn't live up to their stated amperage. Will Prowse checked the Renology DC2DC and found that it put out exactly as claimed, but one had to be realistic as to what amperage was actually sent to the charger and the inevitable internal loss of the charger. A 60A charger can't just create 60A all the time. It probably needs at minimum a 150A alternator and >200A lithium bank.

 

[Xlantic]

Would it not make more sense to charge the house batteries directly off the alternator and use the DC2DC charger to charge the start battery from the house batteries?

Start batteries normally just need a trickle charge whereas the house batteries can usually take all the Amps alternator can throw at it.

(Full disclosure, I am no expert.)