New DC to DC Charger From Renogy-20 amps or 40 amps-Flooded/AGM/GEL/Lithium

[john61ct]

Since in many (if not most) scenarios, current does flow in both directions

we should only be buying two-way meters designed to totalize net flows.

If a vendor sells one-way meters that actually get harmed by two-way flows, they should be forced to pay out warranty refunds for faulty design.

 

[TommyArgh]

Im going thru the manual and its says it needs a control signal or some sort of switch connected to an ignition source. What are you guys using for a ignition source? Do you think an Add-A-Fuse to a reliable source would be sufficient enough?

 

[john61ct]

Any of your circuits nearby that only goes high with IGN live will work. Just a signal, no real current.

Or if you really want manual on-off, then use an always-on circuit with a switch in between.

If you want to use it fed by a source other than alternator, then just jumper off the power input say from your solar controller.

To automate, for any and all multiple sources, put a VSR/ACR in there.

Note every other DC-DC unit I've seen has that last functionality built in.

Personally I reco the Sterling BB series; they are pricier, but fully adjustable for any target chemistry, excellent build quality, real warranty and top CS worldwide.

 

[TommyArgh]

Any of your circuits nearby that only goes high with IGN live will work. Just a signal, no real current.

Or if you really want manual on-off, then use an always-on circuit with a switch in between.

If you want to use it fed by a source other than alternator, then just jumper off the power input say from your solar controller.

To automate, for any and all multiple sources, put a VSR/ACR in there.

Note every other DC-DC unit I've seen has that last functionality built in.

Personally I reco the Sterling BB series; they are pricier, but fully adjustable for any target chemistry, excellent build quality, real warranty and top CS worldwide.

My house battery is in the bed of the truck in a box a built to hold the battery, solar charge controller, AC Charger, 12v sockets, USB sockets, and a couple of metering components. I planned on installing the DC to DC charger in this same box so Id like to try and grab a signal for it nearby. Im trying to avoid the add a fuse to save the headache of running extra wire back. I could use a signal from the solar charger but its almost always on and Id hate to drain the trucks starter battery. I may need to go the switch route but Id hate to have to remember if I switched it on.

Im still new to this so please forgive me, what does VSR/ACR stand for?

 

[dreadlocks]

Auto Charge Relay, the DC Charger's simple minded older cousin.. just hooks everything together when car is running and disconnects when you turn it off.

The wire you run dont need to be very robust, it just sends a signal.. a 20awg or higher would do the job just fine.. tho i'm not certain all DC chargers would need an ignition source wire, they should be able to detect vehicle is running from the upstream voltage alone.. thats a case of RTFM to find out if its just an optional over-ride input or required for operation.

 

[luthj]

Tangentially related, but here is another cheap meter. Supposedly it has some type of wifi/app connection? Not used it myself.

Battery Monitor Meter Wireless DC 120V 100A VOLT AMP AH SOC Remaining Capacity | eBay

Find many great new & used options and get the best deals for Battery Monitor Meter Wireless DC 120V 100A VOLT AMP AH SOC Remaining Capacity at the best online prices at eBay! Free shipping for many products!

www.ebay.com

Do I really need solar

A mobile tent. Follow the 60's

sprinter-source.com

 

[john61ct]

Big question - your DCDC will be fed by what charge source(s)?

Im still new to this so please forgive me, what does VSR/ACR stand for?

Voltage sensitive relay

ACR is what leading vendor Blue Sea calls them

Automatic Charging Relay (ACR) Explained - Blue Sea Systems

Engineering high quality marine electrical components for safety, reliability and performance

www.bluesea.com

Making Sense of Automatic Charging Relays - Marine How To

Making Sense of the ACR WARNING: ACR's are not for use with LiFePO4 Batteries! What is an ACR? An ACR is nothing more than a fully automatic, voltage triggered, BOTH/PARALLEL switch that closes when charging voltage is present and opens

marinehowto.com

originally called "combiners", Yandina invented them

before that people used "isolators" based on diodes, problem there was voltage drop, but with the DCDC maybe not a problem

new versions use MosFETs, but not cheap

 

[john61ct]

Good price to start comparing

Yandina Combiner 100 Battery Combiner - C100

The two battery Yandina Combiner 100 battery combiner is a voltage-sensing relay (13.3 volts) which connects two batteries together when either is receiving a charge. When the charging stops the relay opens allowing each battery operates independently. Yo

www.defender.com

 

[john61ct]

Totally overkill for here, but what a bargain

Blue Sea Systems Automatic Charging Relay 7620 for sale online | eBay

Find many great new & used options and get the best deals for Blue Sea Systems Automatic Charging Relay 7620 at the best online prices at eBay! Free shipping for many products!

www.ebay.com

This is the best on the market, along with the 7622

difference is the manual override right on the unit

 

[teotwaki]

Good price to start comparing

Yandina Combiner 100 Battery Combiner - C100

The two battery Yandina Combiner 100 battery combiner is a voltage-sensing relay (13.3 volts) which connects two batteries together when either is receiving a charge. When the charging stops the relay opens allowing each battery operates independently. Yo

www.defender.com

Compare what? The Renogy is a DC-DC charger and the Yandina is a battery combiner.

 

[TommyArgh]

Big question - your DCDC will be fed by what charge source(s)?

If you were asking me, my charge source will be coming from the trucks start battery as the manual instructs. Is this not the correct way?

 

[teotwaki]

What I'm suggesting is the opamp may not like backward current flow making the non-inverting pin more negative than the inverting pin trying to drive to or beyond the rail. It should just go to zero but it would depend on the components whether this is damaging or not.

That "suggestion" has no basis in differential amplifiers' mode of operation nor their common failure modes. Opamp's output transistors have current limiting resistors. Operational amplifiers only respond to the difference voltage across the input terminals and not to their common potential. The "rails" don't have to be zero and +V. Etc. Etc. Etc.

Beyond the opamp input here could be a current issue in the buffer amp when the difference goes out of range. Or there might exist a damaging condition to the ADC or internal ESD or external transient protection located on the differential amp inputs.

I'm sorry, but such speculation is baseless without you providing the circuit design that you have imagined was used in the wattmeter and provide the specs of each component that is somehow threatened by such nonexistent problems. Undocumented speculation cannot be examined or disputed and is an easy out on a forum.

It's not necessarily an instantaneous stress that does the damage but repeated or allowed to exist long enough it does. When you tore into yours what is the topology, high side or low side? Was the shunt monitor self powered (floating) by chance or ground referenced?

What "stress" in this world are you talking about?? The entire meter consumes only 0.007 Amps whether it is off of the DC circuit being measured or through the external power connector. How in the world does the source of power have anything to do with an imagined failure due to reverse current?

The Watts Up device's shunt resistor is 0.001 Ohms and rated to handle 60 amps continuous and the chip resistor in the clone looked over a 1/4" square so is probably just as robust in terms of wattage.

I agree with you that it shouldn't be a problem but there are ways it could be when it was designed to achieve the 60V and 150A specifications. It might only be a problem at the top end of that range and at ~12V it's not.

Additional baseless speculation without any proof of any such problems in existence. Regardless of the voltage being 12 or 60 , at 150 Amps peak across the .001 ohm shunt we would have 0.150 volts presented to an Op-amp's inputs, forward or reverse current. Exactly what failure mode does that trigger?

The warning is unspecific and I did ruin this Drok meter apparently by running current through it backwards. It indicated zero amps as you would expect but I noticed one day it was blank and dead. It could have just been due to its relative cheapness, though, and not a design flaw.

The Drok meter's "manual" clearly states on the second page it will measure forward and reverse current without issue once the transformer is properly connected. (read the manual- https://images-na.ssl-images-amazon.com/images/I/B1pR7CPThIS.pdf ). Hall effect sensors are not damaged by reverse current flow.

The Drok unit's current consumption is only 0.010 Amps. Your unit was probably defective but it's total failure has nothing to do with reverse current supposedly damaging the Hall effect device because they aren't.

 

[john61ct]

If you were asking me, my charge source will be coming from the trucks start battery as the manual instructs. Is this not the correct way?

That is just shorthand for the engine circuit.

The actual charge source usually wired to that circuit is the alternator.

Others may include a solar controller, a mains charger, in turn powered off either shore power or a portable genset.

Which may currently be wired to that Starter circuit, or directly to the House bank.

The DCDC should **not** be configured to actually draw any power from the Starter battery itself, nor from any battery

it should only be turned on when a charge source is active.

 

[john61ct]

Compare what? The Renogy is a DC-DC charger and the Yandina is a battery combiner.

See my #153 above

If the design is feeding the DCDC from additional charge sources other than the alt, then a VSR/combiner of some sort is required to automate turning it on and off.

All other DCDC chargers on the market include that functionality.

The Renogy 20A & 40A versions do not.

Apparently the new 50A version with integrated mppt SC may or may not, it is not yet of enough interest to me to have investigated that detail.

 

[teotwaki]

My CTEK DC-DC turns itself off when the starter battery is at 12.8vdc. If the CTEK sees voltage on the solar input it uses that as needed to charge the starter battery or the house battery