DC-DC ON-BOARD BATTERY CHARGER WITH MPPT

[Riche2k]

Thank you for your reply.
if Friends don’t let friends buy Renogy, what do they buy instead?
Is there a DC DC charger with MPPT that has the feature of cross connecting the house battery to jump the start battery?
I currently have a Blue Sea ML ACR that charges both batteries AND allows me to cross connect the house battery to “jump” a dead start battery with the flick of a switch. It does not allow charging with solar or the various charge levels to condition a LiFePo battery like the Renogy. The only feature missing in the Renogy is the cross connect to jump the start battery.
Guess I’ll keep my jumper cables handy, unless there is a device that has ALL the features.

 

[RandyP]

I do not know of equipment that is a SCC and DCtoDC charger that also provides switching the two batteries in parallel to jump start the starter battery. But someone else may know. If You still have the ML ACR you might be able to use that, with some precautions to protect the other equipment in the scheme. I've been happy with a starting battery that is in good condition, starting the vehicle occasionally and letting it run for a while to keep the starting battery charged. I do isolate my starting battery from the DCtoDC charger with a disconnect switch at the charging battery when the vehicle is parked.

 

[RandyP]

I abandoned my renogy SCC DC-DC charger after a year of trying to make it work. Very poor customer support from renogy. Piss poor owner manual technical consistency of terminology and in many cases no explanation of equipment set point definitions, inability of the equipment I bought to work with the renogy home app.
Went the Sterling (DCtoDC) and Victron (SCC).
These two pieces of equipment function exactly as explained in their owners manuals, consistently. I am very satisfied with the change.
There are other good DCtoDC battery chargers out there, RedArc, Kisae, Enerdrive and maybe Victron. Each have their Plusses and minuses. All have better customer support than Renogy equipment.

 

[octanejunkie]

Hey guys, I'm a newb and super late to the solar/secondary charging game, but I am looking at a DC to DC system, currently Reynogy MPPT with dual AGM batteries, start and house.

My initial questions are mostly related to managing the start battery - my vehicle doesn't have a smart alternator and I'm concerned with keeping the AGM start battery conditioned properly; which I do manually now with an AGM float style charger once a month. Solar is really the least of my worries, and I have the roof space for a smaller panel, so why not?

The house battery will run a fridge, comms and some electrics when the vehicle is not running, hence solar, but an inverter and compressor will also be wired in to the house circuits to be used when the vehicle is running. Since the off-power draw on the house battery will be smaller, I was planning on a 50-100Ah battery, max, and since roof space is limited, a 50W panel.

Questions I have, for now, are:
1. will my starter battery be "maintained" using a DC to DC charger (with MPPT) ?
2. is a 50W solar panel reasonable to do anything of value to run a 45W fridge off a 50Ah battery?
3. Can I (should I) run analog type battery monitors (charge, state of charge, voltage, etc) on each battery?
4. Is this plan stupid or do I need to learn a lot more before buying and installing?

Thanks, for your patience with a Solar Novice!

 

[justinm001]

Hey guys, I'm a newb and super late to the solar/secondary charging game, but I am looking at a DC to DC system, currently Reynogy MPPT with dual AGM batteries, start and house.

My initial questions are mostly related to managing the start battery - my vehicle doesn't have a smart alternator and I'm concerned with keeping the AGM start battery conditioned properly; which I do manually now with an AGM float style charger once a month. Solar is really the least of my worries, and I have the roof space for a smaller panel, so why not?

The house battery will run a fridge, comms and some electrics when the vehicle is not running, hence solar, but an inverter and compressor will also be wired in to the house circuits to be used when the vehicle is running. Since the off-power draw on the house battery will be smaller, I was planning on a 50-100Ah battery, max, and since roof space is limited, a 50W panel.

Questions I have, for now, are:
1. will my starter battery be "maintained" using a DC to DC charger (with MPPT) ?
2. is a 50W solar panel reasonable to do anything of value to run a 45W fridge off a 50Ah battery?
3. Can I (should I) run analog type battery monitors (charge, state of charge, voltage, etc) on each battery?
4. Is this plan stupid or do I need to learn a lot more before buying and installing?

Thanks, for your patience with a Solar Novice!

1. Leave the start alone and continue the float charger. Best to keep batteries separate.
2. 50w of solar is 250w total per day IF you're lucky. 50AH battery at 12v is 50*12 is 600w so it'll take 3 days to charge over solar.
3. Get a Victron smartshunt and setup for house. I believe it has an aux battery monitor wire, can't remember but regardless your starter should be fine.
4. more solar is better. you can overload the amps just not the volts on a MPPT so more solar means more power. Also can get multiple mppts.

 

[octanejunkie]

Thanks for the speedy reply! A few questions...

1. Leave the start alone and continue the float charger. Best to keep batteries separate.

Yes, that makes sense, but I am concerned my 1999-vintage alternator will not properly charge a 2022 AGM battery...

2. 50w of solar is 250w total per day IF you're lucky. 50AH battery at 12v is 50*12 is 600w so it'll take 3 days to charge over solar.

Yeah, I suspected I would be undercharging with solar, but it's more of a secondary charge source, like when parked I get *some* charge vs leaving the car running...

3. Get a Victron smartshunt and setup for house. I believe it has an aux battery monitor wire, can't remember but regardless your starter should be fine.

Will look into it, thanks. I have another, cheaper shunt-type of battery status mon waiting to be installed.

4. more solar is better. you can overload the amps just not the volts on a MPPT so more solar means more power. Also can get multiple mppts.

I am limited with roof space, but could look into portable panels for longer stays in camp/fulltime solar... good idea!

 

[mikefitz]

Is this plan stupid or do I need to learn a lot more before buying and installing

Not stupid but you need more solar and more battery. For older vehicles with low output alternators suggest limiting the Battery to Battery charger to 30 amps.
Q1, some DC to DC B2B chargers will maintain the starter battery, Renogy DCC50 of Ctek 250S have this capability.
Q2, too small solar and battery, minimum will be 200 to 300 watts of solar and 200 Ah of AGM.
Q3, Victron Smart Shunt will monitor SOC on house battery but only voltage on starter battery, this is a practical situation.
Q4, more planing and estimation of power used and power supplied by solar and engine.

You could save on engine charging unit by using a 120 A voltage controlled battery combiner between starter and house battery,

Cyrix Battery Combiners - Victron Energy

Automatically connect batteries in parallel when one of them has reached a pre-set voltage using the Cyrix Battery Combiners. Find a dealer near you.

www.victronenergy.com

Using this with suitable quality cables will charge AGM house batteries. The AGM batteries will not overload your alternator.

The saving could be used to fund a quality Solar controller with fully programmable charge profiles, Victron Smart Solar 100/30, good for up to 400 watts of panels.

BlueSolar MPPT 100/30 & 100/50 - Victron Energy

Maximize the energy-harvest, driving it intelligently to achieve full charge in the shortest possible time using the BlueSolar MPPT 100/30 & 100/50. Find a dealer nearby.

www.victronenergy.com

 

[octanejunkie]

Not stupid but you need more solar and more battery. For older vehicles with low output alternators suggest limiting the Battery to Battery charger to 30 amps.

Okay, but why limit to 30A / DCC30A ?
Renogy felt either the 30A or 50A MPPT would work for me, especially if I upgrade alternator (amps) in the future
Current alt is 80A rated

Q1, some DC to DC B2B chargers will maintain the starter battery, Renogy DCC50 of Ctek 250S have this capability.

That's what drew my attention to Renogy, the idea of having both AGM batteries, house and start, managed/maintained

Q2, too small solar and battery, minimum will be 200 to 300 watts of solar and 200 Ah of AGM.

I realize my initial goals are very low by most's standards/needs here - I am trying to work with the space/use case I have today

Q3, Victron Smart Shunt will monitor SOC on house battery but only voltage on starter battery, this is a practical situation.
Q4, more planning and estimation of power used and power supplied by solar and engine.

Cool, looks like Victron is a standard in the industry, I will take a look

You could save on engine charging unit by using a 120 A voltage controlled battery combiner between starter and house battery,

Cyrix Battery Combiners - Victron Energy

Automatically connect batteries in parallel when one of them has reached a pre-set voltage using the Cyrix Battery Combiners. Find a dealer near you.

www.victronenergy.com

Using this with suitable quality cables will charge AGM house batteries. The AGM batteries will not overload your alternator.

I will check it out, thanks!

The saving could be used to fund a quality Solar controller with fully programmable charge profiles, Victron Smart Solar 100/30, good for up to 400 watts of panels.

BlueSolar MPPT 100/30 & 100/50 - Victron Energy

Maximize the energy-harvest, driving it intelligently to achieve full charge in the shortest possible time using the BlueSolar MPPT 100/30 & 100/50. Find a dealer nearby.

www.victronenergy.com

I will check this out, too!

Not looking to break the bank on secondary charge source, but quality components are worth the investment.

 

[justinm001]

Okay, but why limit to 30A / DCC30A ?
Renogy felt either the 30A or 50A MPPT would work for me, especially if I upgrade alternator (amps) in the future
Current alt is 80A rated


That's what drew my attention to Renogy, the idea of having both AGM batteries, house and start, managed/maintained

I realize my initial goals are very low by most's standards/needs here - I am trying to work with the space/use case I have today

Cool, looks like Victron is a standard in the industry, I will take a look


I will check it out, thanks!


I will check this out, too!

Not looking to break the bank on secondary charge source, but quality components are worth the investment.

Victron is the gold standard. Tried, trusted, proven and most reliable. Of course its most expensive so its best to start there then if cost is an issue compare to cheaper but similar models. Only real exceptions are batteries and solar.

For solar get as much as you can fit without shading issues. Move things around, put it on top, whatever you can do because capturing as much free energy is the cheapest way.

80amp alt is very small and likely you can only use 50-60amps consistently with the vehicle using the majority of it. I would only go 20 or 30a max until you upgrade the alternator.

 

[S Davis]

I have used a 50amp Redarc for about two years with no issues, one thing I will say is size your wire appropriately, I have mine sized for 120 amps as I am paralleling a second 50amp Redarc.