DC to DC charger

[jdcellarmod]

Thinking of installing a Victron charger for those days on the road when solar is not available. Can the charger be used in conjunction with an inverter (2000 watts) to run the refrigerator on electric while on the road?

Thanks, Jeff D

[StirCrazy]

Camper_Jeff_&_Kelli wrote:
The best thing about Lithium is they always put out 13.2 volts thanks to the BMS. Lead batteries, all types, slowly drop voltage as they discharge causing brown out conditions like dim lights, slow pump motors, and weak other loads. Not so with Lithium. 13.2 volts stable all the way down to 80 or 90% discharge and then the BMS protection shuts it off till recharged. Lithium is like having your cake and eating it too.

now thats not true, at 90% discharged the voltage of a LiFePO4 battery is only 12.0V if you would have said they put out over 12V untill 90% discharged then yes that is true and still a huge advantage over a wet battery which hits 12V at about 50% discharged. an even better advantage of the LiFePO4 is the voltage level under load, you can discharge much deeper befor you get alarms from your inverter from low voltage. a flooded battery can drop to 11.5V at 100% charged if it has a C/3 load on it, so basicly a 100 amp battery with a 33amp load will dip pretty fast, which is why for big rigs people run 4 6V batteries or more. Lifepo4 doesnt have this issue to that degree as you can do a C1 discharge and stay above 12V to 90% discharge which would be a 100 amp draw on a 100amp battery. so in a way your right just your numbers are off a little.

[pianotuna]

Camper_Jeff_&_Kelli wrote:
The best thing about Lithium is they always put out 13.2 volts thanks to the BMS.

It is the nature of the LI, not the BMS.

[theoldwizard1]

Grit dog wrote:
Telecom jars is his nifty lingo for telecommunications backup batteries.

These are basically, individual lead-acid cells. Very early telephone systems ran on DC. The voltage to ring the bell somewhere between 50-100V and it was switched (mechanically) on and off.

The old versions of these batteries were HUGE! Think of a double stack full size washer and dryer. This was one cell, 2.2V ! The term "jar" refers to case/housing that contains liquid acid and the lead plates.

[Camper_Jeff___K]

All in all, life is better with Lithium Iron batteries. Better still with a dc to dc charger. Disconnect the 7 pin power wire from charging your batteries, it is no longer needed and may cause a feedback loop. Your dc to dc charger will be feeding a higher voltage back to the alternator and computer through that wire if left connected and you don't want that, weird stuff can happen. Right now, I'm in the TC with my 400 AH batteries at 80% charge because there was no sun to speak of today to charge them. Tomorrow I'll go for a drive and my 30 amp dc to dc charger will give them a good charge back up in an hours time. Enough to get a nice bacon cheese burger and walk along the beach. My 675 watts of solar on the roof and the MPPT Victron history shows I got a peak of 53 watts for a couple hours today. The redundancy of the 30 amp dc to dc charger is so nice to have. My 10 year old BoonDocker 45 amp shore power supply has something wrong with it and is only putting out 4 amps. I'm going to replace it with a Victron 3000 watt inverter power supply when I get down to Quartzite. The best thing about Lithium is they always put out 13.2 volts thanks to the BMS. Lead batteries, all types, slowly drop voltage as they discharge causing brown out conditions like dim lights, slow pump motors, and weak other loads. Not so with Lithium. 13.2 volts stable all the way down to 80 or 90% discharge and then the BMS protection shuts it off till recharged. Lithium is like having your cake and eating it too.

[pianotuna]

Grit dog wrote:
Telecom jars is his nifty lingo for telecommunications backup batteries.

It is not my acronym. It is name used by the cell companies. They are a sub variant of AGM. I like them as I no longer have to lay down in the snow to do a specific gravity test.

[ticki2]

HMS , that post should have been all caps . ?? so much partial info here

[Grit_dog]

Telecom jars is his nifty lingo for telecommunications backup batteries.

[HMS_Beagle]

pianotuna wrote:
The lead acid were replaced with telcom jars, and whoops there was no charging from the alternator to the house unless I was running the microwave or other heavy draw. In fact it regularly sent power to the alternator. I replaced the starter battery with an AGM. No improvement.

No idea what you mean by "telcom jar batteries", perhaps they have particularly high voltage.

Anyone interested in house battery charging from the alternator, or mixing battery types, needs to do some basic measurements: voltage and current with batteries fully charged and engine running well above idle, and voltage and current with house batteries discharged at least 50%. Measurements done at truck engine compartment (say at the start battery) and at the house battery. This is important in some cases to insure there is actually a charge, and in some cases to prevent a fire from overcharging. From those two measurements you can determine if the wiring is adequate, if you are getting sufficient charge, and if you are overcharging.

There is a range of trucks here spanning 30+ years, charging strategies and regulation have changed in those 30 years and between brands. A DC-DC boost-buck charger can cover a lot of sins in a charging system, but may not be necessary, or may not be the only thing necessary, or may actually be detrimental. You need measurements to know.

[S_Davis]

theoldwizard1 wrote:

S Davis wrote:

That is not true on newer GM HD trucks, my 2019 Chevy 2500HD sits above 14 volts, when changing my batteries it will ramp up to just above 15 volts @ 50amps.

According to the above statement I should have a smart alternator, but I have yet to see this mysterious lowering of voltage a few people on here keep stating.

Check the voltage at the starting battery immediately after starting and at the house battery.

Drive for 10-15 minutes and, with the engine still running, check those voltages again.

I have voltage meters, they stay constant above 14v and if the LifeP04 are charging it’s highe.

[S_Davis]

deltabravo wrote:

S Davis wrote:
... on newer GM HD trucks, my 2019 Chevy 2500HD sits above 14 volts, when changing my batteries it will ramp up to just above 15 volts @ 50amps.

15+ volts is all the more reason for a DC to DC Charger. I don't think Lithiums will agree with that high of a charge voltage.

I am using a 50amp DC to DC charger.

[Hemi_Joel]

If I wanted to run a fridge while on the highway and not on propane, I would mount an inverter under the hood close to the battery, then run a 110 volt cord back to the fridge circuit.
Or you could plug the whole camper into it and the built-in charger in the camper would keep the camper batteries up.

[Hemi_Joel]

I agree that the really expensive batteries need more expensive fancy equipment to try to help keep them alive as long as possible.
I don't see that the original poster ever said what kind of batteries he has.
I am assuming he has FLA batteries, but that could be wrong.
I have found that the FLA batteries I use will handle a lot of abuse. I never bother to check that they are charged to 100%, I just know they are charged enough to do the job for me. I don't babysit them. If they fail in 3-5 years, I don't care, they are cheap. I'm road trips for fun, not to think about batteries.
For some people, the electrical system of their camper is an interesting hobby. The more gadgets, the more enjoyment. I get that. Those in that group, you know what you have to do.
And then there is another group, that I am not going to attempt to describe. They should just buy the 12-12 charger.
For me, I just want to have electricity when I want it. I am willing to spend money where it makes sense, but I don't want to waste it, or make things over complicated. So for me and like minded people, a pair of heavy gauge wires is fine.

[deltabravo]

S Davis wrote:
... on newer GM HD trucks, my 2019 Chevy 2500HD sits above 14 volts, when changing my batteries it will ramp up to just above 15 volts @ 50amps.

15+ volts is all the more reason for a DC to DC Charger. I don't think Lithiums will agree with that high of a charge voltage.

[theoldwizard1]

S Davis wrote:

That is not true on newer GM HD trucks, my 2019 Chevy 2500HD sits above 14 volts, when changing my batteries it will ramp up to just above 15 volts @ 50amps.

According to the above statement I should have a smart alternator, but I have yet to see this mysterious lowering of voltage a few people on here keep stating.

Check the voltage at the starting battery immediately after starting and at the house battery.

Drive for 10-15 minutes and, with the engine still running, check those voltages again.

[theoldwizard1]

Hemi Joel wrote:

theoldwizard1 wrote:

Hemi Joel wrote:
I just use a pair of 8 gauge wires from the truck battery to the camper batteries. That eliminates the voltage drop of the 7 pin and puts a nice charge into the camper batteries whenever I drive.

It has been proven 100s of times, that with modern vehicles, large gauge wires will NOT give you a 100% charge on your auxillary battery bank.

Some charge, yes. Just not 100%.

That makes no sense at all. The alternator doesn't know how many batteries are connected to it. It senses voltage. Batteries that are connected equalize over time.

Yes, batteries will equalize or time. How many hours are you willing to wait ? For heavily discharged house batteries, it could be more than 10 hours !

Why ? Because the alternator and internal voltage "regulator" no longer determine the actual voltage output !. In an effort to save fuel the engine computer goes through calculations that MINIMIZE the voltage put out by the alternator.

Don't believe me. Start your vehicle and immediately check the voltage at the battery. Drive for 10-15 minutes and, with the engine running, check the voltage again. It will be close to 13.2V, just enough to prevent a battery from discharging. Not high enough to recharge a house battery.