redarc manager 30

[john61ct]

Amps are a maximum, to get faster charging need to buy a higher rated unit, or if possible stack multiple units in parallel.

Note that going to a higher current does not necessarily mean you get to 100% Full much faster.

All depends on the C-rate accepted by that chemistry (CAR rating, size of the bank vs amps available).

For lead chemistries, resistance causes trailing current rates, so 6-7 hours is usually the shortest possible charge cycle to get to 100% Full, no matter how many amps the charge source.

 

[dreadlocks]

Trailers for example pretty much need a DC charger to get a house bank completely full off a tow vehicle.. after a couple dozen feet of rather low gauge wiring the trailer battery will never see full voltage.. the DC charger will boost it back up to what the battery needs to complete its absorb and stay healthy regardless of the input voltage way back in the trailer.. one just needs to take care not to overload the supporting wiring.. because a battery alone wont really overload the wiring taking a charge, the voltage would drop below its own voltage before that happens, but a DC charger will.

 

[taliv]

Within designed input limits, a DC to DC will raise or lower its output voltage to whatever its programmed to be.

If operating in parallel, just like anything else. It doubles the current available. Voltage remains the same.

thanks, that's what i was getting at on the voltage. however, I was trying to figure out how having disparate chargers would work. how do they keep from interfering with each other, if for example, one is a vehicle alternator and the other is a solar panel

I do not know which voltage you mean. If the charger voltage setting is not a fair bit higher than the battery "at rest" voltage, no effective charge current can flow.

> if there are two in parallel both trying to charge the battery, they both will put the precise charge profile without doubling it?

Voltage stays the same, amps current doubles - that is what "parallel" means.

i meant the voltage from the alternator, crossing a cable with some loss. i think verk and dread answered that though. thanks

i understand putting batteries in parallel vs series as outputs. what i don't understand is when charging a battery, particularly the last few percent til full, what happens if you have two separate chargers with separate charge profiles. in context, the manager 30 has everything connected to it. so the battery, shore, solar, alternator are all going through 1 device. if you have two chargers, say 1 solar, 1 alternator, that have different outputs, and you connect them to the same battery, is that a problem? or will one see the voltage/current from the other and think the battery is charged?

Trailers for example pretty much need a DC charger to get a house bank completely full off a tow vehicle.. after a couple dozen feet of rather low gauge wiring the trailer battery will never see full voltage.. the DC charger will boost it back up to what the battery needs to complete its absorb and stay healthy regardless of the input voltage way back in the trailer.. one just needs to take care not to overload the supporting wiring.. because a battery alone wont really overload the wiring taking a charge, the voltage would drop below its own voltage before that happens, but a DC charger will.

thanks, i think that's the answer

 

[john61ct]

however, I was trying to figure out how having disparate chargers would work. how do they keep from interfering with each other, if for example, one is a vehicle alternator and the other is a solar panel
…
what i don't understand is when charging a battery, particularly the last few percent til full, what happens if you have two separate chargers with separate charge profiles

There are many expensive devices that are promoted this way

but in fact they are solutions in search of a problem.

Disparate charge sources of all kinds can be paralleled and concurrently active

without any issue. them "interfering" with each other is from a practical POV just a common myth

yes in theory a complex set of issue

but **not** a problem IRL

Of course, each of the outputs should not be of V / A that would harm the bank.

If your battery is of a type that is susceptible to "too much current" then watch out for the total "amps available" maybe getting too high, but for lead chemistries that would be vanishingly rare, 99.99% self-regulating chemistry there.

As for the charge-termination happening right at the correct endAmps spec point for 100%

again not a problem, 99.99% of the time that doesn't happen anyway 8-D

but whichever source has the best algorithm will be "the winner", as the others drop theirs to Float they are "dropping out of the race"

and only 0.0xx C-rate is flowing at that point anyway.


BTW I highly recommend getting higher quality standalone controllers if solar is important to your overall system

Those included with the newer DCDC "combi" units are sub-par at best, IMO best used just to keep a Starter topped up if the rig is stored where shore power is not conveniently available.

 

[taliv]

Thanks!

what solar charger would you suggest?

 

[dreadlocks]

with multiple Parallel Victron SmartSolar's they can get a little wonky, but mostly from being too smart for their own good.. they measure the resting voltage when the panel wakes up and uses it as a factor in determining how long to absorb before going to float.. if one SmartSolar awakens before the other, it will start feeding charge into the battery, and when the subsequent ones fire up they will see a higher voltage thinking thats batteries resting voltage they will all hold varying absorb times.

The solution to that issue is to simply use fixed absorb times, so a simple config change.. or wait for their firmware that coordinates all the chargers via bluetooth so they all change charge stages in unison.. Ive just been using the fixed absorb anyhow cuz thats whats best for my LFP chemistry.

but yeah, multiple chargers is rarely anything to be concerned with.. thats about the only instance I've encountered with it.

 

[taliv]

with multiple Parallel Victron SmartSolar's they can get a little wonky, but mostly from being too smart for their own good.. they measure the resting voltage when the panel wakes up and uses it as a factor in determining how long to absorb before going to float.. if one SmartSolar awakens before the other, it will start feeding charge into the battery, and when the subsequent ones fire up they will see a higher voltage thinking thats batteries resting voltage they will all hold varying absorb times.

The solution to that issue is to simply use fixed absorb times, so a simple config change.. or wait for their firmware that coordinates all the chargers via bluetooth so they all change charge stages in unison.. Ive just been using the fixed absorb anyhow cuz thats whats best for my LFP chemistry.

but yeah, multiple chargers is rarely anything to be concerned with.. thats about the only instance I've encountered with it.

that's exactly the sort of thing i was concerned about. so, why is it just solar? could it happen to 1 solar and 1 DC charger?

 

[dreadlocks]

their Orion DC/DC charger does not have that routine, its simpler or stupider in that regard.. nor does it really need it, thats a feature to extend battery life on full time fixed solar setups that are cycling to various rates of discharge daily and rarely using other sources.. for a DC charger it has no reason to coddle the batteries in such a way, your not driving over 12h a day every day all year long like a Solar setup does.. so using a fixed absorb time is perfectly fine. For portable recreational use that feature not even needed, few of us will get anywhere near rated cycles out of our lead banks before they age out.. its a consideration for full time off the grid cabins that can get a couple thousand cycles in 5 years, not so much recreational use.

 

[sAsLEX]

How close does the DCDC have to be to the battery bank? I am looking at approx. 1.2m away with current design, I would ensure that the wiring is up to task to avoid significant losses there.

 

[dreadlocks]

As close as you can reasonably get it, you want voltage drop minimal.. like less than 0.1v, if your battery needs 14.4v to get full, 14.3v won't get it there.

The trick to keeping lead bank happy and healthy is giving it a full, complete charge to 100% SOC as much as you can.. chronically undercharging em dramatically reduces life, its like it spent all its days at a partial charge and that is ridiculously abusive to lead batteries.

 

[taliv]

does it matter if we're talking lifepo4 instead of lead?

 

[dreadlocks]

yes, LFP is the opposite.. it'll last longer if its not persistently fully charged.. storing em long term at 40-60% SOC increases lifespan.. If you left a lead battery at that SOC over the winter, it'd be useless come spring.

my LFP I have set to 14.2v maximum, my manufacturer recommends 14.6v.. I'm persistently undercharging and loosing a few AH in capacity for the sake of longevity and coddling.. I dont need those few AH to make it worthwhile.

Its same reason why Tesla can unlock extra battery capacity in natural disasters, normally they leave a bunch of capacity at both ends (full/empty) out of the users reach to prolong the pack life.. but they will unlock it to increase range if people need to evacuate a hurricane.

 

[taliv]

you're saying if you don't fully charge it, it lasts longer?

 

[dreadlocks]

yes, with a LFP bank the reason you want something like Victron over RedArc is because you can set all the custom voltages you want.. I have all my chargers feeding 14.2V to charge, and I have a BatteryProtect wired up to the relay on my BMV-712, once the calculated SOC drops below 20% it drops all loads.. this setup keeps me within about 20-92% SOC, never gets fully charged.. never gets fully discharged, if all goes well it should last decades.. I've got 72AH a day to work with which is more than what I need, my 650W of solar can recharge that back with just 2-3h of direct sunlight a day, or I run the genset for an hour or two if the sun's not cooperating.. dumping 0.4C charge current into my house battery makes daily cycling for rec use tolerable, dont need full days of sun, dont need full days of genset idling to get it back to 100%.. heck just turning on the generator for 45mins dumps enough energy into my LFP to get me through the night with furnace and fridge running so meh on spending more money for more LFP so I can go more than a day.

Its much like USB-C Phones vs Old USB Phones.. used to want a battery that could last days because it took all night to charge and if I forgot one night I needed it to last more than a day.. now my new phone w/10x the charge speed gets >1% a min.. takes an hour and a half to fully charge it, now when I wake up to a dead phone, the 20min drive to work gives me enough charge to get through most of the day, instead of putting 2% charge back in and requiring me to leave my phone tethered to the desk all day long.. Suddenly how long my battery lasts is mostly moot, charging it is no longer anywhere near as inconvenient.. it lasts over a day fully charged, thats more than enough with this device, but it was not w/my previous device.

On Lead you've got a hard limit of 6-7h to fully charge the bank, you desperately want it to get to 100% and there's nothing you can do about it.. but a LFP bank can go from flat to full in ~2.5h with 0.4C, and you dont care if it gets full or not.

 

[john61ct]

you're saying if you don't fully charge it, it lasts longer?

In fact to maximize longevity should only take its SoC up just before you need to start discharging it.

But if that is difficult don't stress, they last a long time anyway.

Stopping at 3.42V will be healthier than 3.5V

Def want all charge sources to be user-custom adjustable.