DC-DC charger (B2B) options and general discussion

[Zwy]

Gotcha' makes sense. Thanks. So I'm correct in understanding that the Kisae will output 50A at 12V so long as it gets fed 600W by whatever combination of voltage and current (below the 30A maximum) results in an incoming 600W to the controller? The 30A maxmium for the PV input in the manual is what had confused me.

I sent Kisae a message to see if they have the ability to step up 12v to 24v. From what I could see in the specs, it seems one can have 12v input and 24v output.

 

[fratermus]

The 30A maxmium for the PV input in the manual is what had confused me.

It confuses me too, but maybe I'm not looking at it right.

Both the 30A and 50A 12v versions specify 30A (also stated as 500w/600w overpaneled) solar input, which is weird if they had different (30A v 50A) PV charging output limits. With a max of 500w solar input it can't put more than 500w into the bank. At 12.1v output 500w would be ~40A. At 14.8v 500w out would be ~34A. Both of those, even my math-impaired eyes note, are less than 50A.

I will paypal a beer to the first person who puts one on the bench to test how much charging current the 50A model shovels into a discharged battery from 500w of mock-PV input.

 

[baipin]

It confuses me too, but maybe I'm not looking at it right.

Both the 30A and 50A 12v versions specify 30A (also stated as 500w/600w overpaneled) solar input, which is weird if they had different (30A v 50A) PV charging output limits. With a max of 500w solar input it can't put more than 500w into the bank. At 12.1v output 500w would be ~40A. At 14.8v 500w out would be ~34A. Both of those, even my math-impaired eyes note, are less than 50A.

I will paypal a beer to the first person who puts one on the bench to test how much charging current the 50A model shovels into a discharged battery from 500w of mock-PV input.

Confusing, right?! Because of the consistency in watts and inconsistency in current between ratings, my money is on "you can use any combination of panels so long as the voltage output is between 14V and 50V, the current is less than 30A, and this will be converted into a 12V nominal voltage with a maximum amperage of 50A."

 

[trevor.the.van]

That's becoming nearly analogous with my "on-demand" Trailer Mod, Although a single-unit van has no need to boost the charge Voltage as far as I do. (I boost all the way to 36V, to reduce current through the 7-pin Bargman cable to the Trailer. In the Travel Trailer, I receive power into an MPPT controller which also runs regular panels "while camping", or whenever the Tow Vehicle high Voltage conversion has not been enabled.) In Vans, you guys can simply use a heavier wire all the way from the battery - but I LIKE and I DID do exactly as you have just described to enable all of the power consumption only on demand, with the habit of only switching it on while cruising.

Here is my dashboard, the switch becomes disabled when the (1) the ignition is not turned on; AND the secondary "Voltage Switcher Power Relay" only becomes active when the switch is enabled and flipped up. Completely on-the-fly, I can also turn it off while waiting at traffic lights and crawling through slow traffic in towns along the way.https://diysolarforum.com/threads/r...charge-solar-in-the-trailer.20730/post-242550

Yes, I have previously read through your post - very nice idea which I may look at pinching in the future

 

[Zwy]

Sorry, forgot to add the link in my above post. https://diysolarforum.com/threads/h...a-dc-dc-battery-charger-with-mppt.4402/page-2

Note the following For the DMT1250: Up to 500W (600W allowable) for 12V and up to 750W (800W allowable) for 24V nominal panel arrays.

 

[Zwy]

Reading another thread about a response from Kisae regarding their chargers, I came across this:

As I understand it, the DMT1250 has a 30A solar input. That means it will still output 50A at 12V (600W), provided the current from the solar panels is less equal to or than 30A and voltage is greater than or equal to 20V (600W), right?

Compared to the Renogy DCC50S which has a measly PV input of 25V, the 50V max on the Kisae means I can use these nominally 40V panels in parallel, right? For let's say, 390W+390W = 780W at 40V and 20A. Because I am overrating here, and providing more PV input than the charger can output, I should effectively be getting 600W for longer in the day with this setup than the 600W I'd receive from the DCC50S since that system would be at 17V nominally and it can only be overrated to 660W as I understand from their manual.

I would contact Kisae for more clarification at higher voltages and what the max input amps can be. I might cap at 600w output but it might not like being overpaneled either. And if input is capped, this would mean getting closer to VOC of PV array.

My question is; how much more efficient is the Kisae at 40V nominally than the Renogy DCC50S at 17V if they are both outputting 600W but being fed 780W and 660W respectively? What are some rough numbers for watts-per-day that I could glean from either of these systems, considering the 40V should charge off-peak longer than the 17V panels?

 

[baipin]

I would contact Kisae for more clarification at higher voltages and what the max input amps can be. I might cap at 600w output but it might not like being overpaneled either. And if input is capped, this would mean getting closer to VOC of PV array.

Yup, I've contacted Kisae and await a response. Given your last post I think we're correct in assuming you can overpanel up to the 800W so long as you use higher voltage panels, to ensure you get the 600W output for longer off peak hours.

 

[Zwy]

Yup, I've contacted Kisae and await a response. Given your last post I think we're correct in assuming you can overpanel up to the 800W so long as you use higher voltage panels, to ensure you get the 600W output for longer off peak hours.

Got a response the other day. This looks to be my first choice.

Thank you for writing to KISAE to inquire about whether we have a 24V output DC-DC battery charger.

In fact, we do have the model DMT2430 which takes 12V input and outputs 24V DC to charge 24V auxiliary batteries. I have attached a datasheet for your review.

Please let me know if you have any questions.

Best regards,
Lawrence Neill
KISAE Technology

 

[pajarojo]

Got a response the other day. This looks to be my first choice.

Thank you for writing to KISAE to inquire about whether we have a 24V output DC-DC battery charger.

In fact, we do have the model DMT2430 which takes 12V input and outputs 24V DC to charge 24V auxiliary batteries. I have attached a datasheet for your review.

Please let me know if you have any questions.

Best regards,
Lawrence Neill
KISAE Technology

That's confusing... I had previously panned the DMT 2430 because I assumed it did require 24v nominal input (this is from the datasheet you linked):

 

[Zwy]

That's confusing... I had previously panned the DMT 2430 because I assumed it did require 24v nominal input (this is from the datasheet you linked):
View attachment 45806

My understanding is you can input solar or alternator power in the "12v range" and it outputs 24v. It is why I sent them an email. If you go to Don Rowe page here and look at specs. https://www.donrowe.com/kisae-dmt2430-abso-30a-24v-dc-dc-battery-charger-p/dmt2430.htm Note solar can be 14.5v also and it will output 24v

Input (Alternator)	10.5 - 16.0 / 21.0 - 32.0 VDC
Input (Solar)	14.5 - 50.0 VDC
Output current	5 / 10 / 20 / 30A (User Selectable)
Output voltage	24 VDC
Dimensions	9.5 x 6.8 x 2.9 in (242 x 172 x 74 mm)
Weight	4.1 lbs (1.9 kg)
Shipping weight	6.0 lbs (2.7 kg)
Warranty	1 year

 

[TRAMP]

View attachment 36560

Hey folks so I'm finally getting closer to install day for the electrical upgrade to my 2004 Lance 1161 Truck Camper. I've spent hours researching DC to DC chargers and Battery to Battery chargers and have decided all of the ones currently on the market are meant to protect low or medium output alternators and would defeat the purpose of the premium I spent to purchase my 370a high output alternator I currently have on my 2000 Ford F350 SD. So as an alternative to using DC to DC chargers, I have decided instead to isolate my 2 - 400ah LiFeON4 batteries into 2 separate battery banks using a 4-way manual switch so that my alternator will never to trying to charge 800ah of LiFeON4 batteries at once. On my previous truck camper my 370a alternator had no problems charging 3 - 150ah LiFeON4 batteries at once so am hoping this solution will work. Would welcome some feedback or suggestions. The fuses, breakers and busbar placements are random and my installer will decide where those should go. Cheers

check out a CTEK with smart pass

 

[TRAMP]

I have 2015 Roadtrek express 3500 gas chassis with dedicated under hood alternator 270amp for the 4 Lifepo4 12v battery packs at 272AH each. Nations Alternator says I have to covert alternator from internal voltage regulator to external and use Balmer Regulator with custom harness from them for $400. Can I bypass this and just use a DC to DC charger?

On Board

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[DerpsyDoodler]

My understanding is you can input solar or alternator power in the "12v range" and it outputs 24v. It is why I sent them an email. If you go to Don Rowe page here and look at specs. https://www.donrowe.com/kisae-dmt2430-abso-30a-24v-dc-dc-battery-charger-p/dmt2430.htm Note solar can be 14.5v also and it will output 24v

Input (Alternator)	10.5 - 16.0 / 21.0 - 32.0 VDC
Input (Solar)	14.5 - 50.0 VDC
Output current	5 / 10 / 20 / 30A (User Selectable)
Output voltage	24 VDC
Dimensions	9.5 x 6.8 x 2.9 in (242 x 172 x 74 mm)
Weight	4.1 lbs (1.9 kg)
Shipping weight	6.0 lbs (2.7 kg)
Warranty	1 year

im interested in the DMT 2450, myself. strongly considering it.

 

[pajarojo]

im interested in the DMT 2450, myself. strongly considering it.

It's actually the DMT 2430 or the DMT 1250. They have a "DMT2450" posted on their website but it is an apparent mistake. I reached out via. email and confirmed. Too bad as I would prefer the higher wattage of a 2450 model.

 

[DerpsyDoodler]

It's actually the DMT 2430 or the DMT 1250. They have a "DMT2450" posted on their website but it is an apparent mistake. I reached out via. email and confirmed. Too bad as I would prefer the higher wattage of a 2450 model.

Well that bursted my bubble. i want the higher output, but I dont want to spend double the money on 2 chargers. This is really disappointing.

 

[BrianN]

Does anyone have any experience with the National Luna DC-DC Chargers? I'm upgrading to a Lithium battery from AGM and I shall have to toss my CTEK D250SA for this reason. So far, the contenders are the Renogy DCC50 and National Luna NLDC40. Since everyone seems familiar with the Renogy I am attaching the specifications and NLDC40 User Manual

 

[Zwy]

Does anyone have any experience with the National Luna DC-DC Chargers? I'm upgrading to a Lithium battery from AGM and I shall have to toss my CTEK D250SA for this reason. So far, the contenders are the Renogy DCC50 and National Luna NLDC40. Since everyone seems familiar with the Renogy I am attaching the specifications and NLDC40 User ManualView attachment 47289

First thing is Renogy only has a Max solar input voltage of 25V. The one you show specs for has a max of 42V. Higher input voltage is always better and allows you more choices when it comes to panels or connecting in series.

You want to minimize voltage drop from your PV array to the controller. A voltage drop of 1.0V on a 24V PV array is 4.2%. A drop of 1.0V on a 42V PV array is just under 2.4%.

 

[gelmjw]

I need y'all to review my plan to charge my 24V house bank for $18USD.

Dasiter 600W High Power DC to DC Boost Converter DC 12-60V to 12-80V Boost Module Board Step-up Transformer

I have been pulling a travel trailer with a van. It is a 30A trailer. One way to describe my rig is a split 'B'.
Where most rigs have all of the electrical in the trailer, the van is my main source of VAC for the trailer.

This plan was started when my 12V inverter/charger in the van went toes up. Right now, the 600AH bank is being charged by solar and the alternator. There is a 6Ga positive cable with a 25A in-line fuse between the starting and house bank with a chassis ground return, very parallel. The current is between 20 and 25A because I blew a 20A fuse but the 25A has held up. I don't want to lose this charging source.

I am changing to a 24V house system with a Growatt 3000 24V AIO. The AIO will replace the existing SCC and Inverter/charger. The 12V, 600AH bank will be rewired to 24V, 300AH.

Defs:
House - the 24V 300AH AGM bank.

SCC - A 15A limited 24V MPPT with max 400W input draw. VOC = 60V. It will ignore excess Amps/Watts. I have this.

Boost - the $18 device I need in the link above. What I need this device to do is present a psuedo 400W(12A * 33V) panel to the SCC.

BIRD - Bidirectional, Voltage sensing relay. I have this.

The flow :
House <- SCC <- Boost <- BIRD <- alternator.

Can the Boost's Volt and Amp pots do this?
Will I have ground issues?

 

[Ram5500 CamperThing]

I am running the Sterling 60amp B2B charger with a 300ah LifeBlue battery and it has been performing flawless after a lot of testing and abuse.

Victron app shows it delivering 58amps at idle when SOC is below 50%

The manual says 6awg for install, but i went with 4awg because i had plenty of it in the garage.

NOTE: I have 3 friends i know personally that have had Renogy DCDC crap out on them, so beware of those

 

[RGIvy]

Not sure if this has been mentioned in the 14 pages of this thread, but perhaps an important column to add to the first list is whether the DC-DC charger looks after both leisure (house) and starter battery.
We just installed a Victron into my daughters van only to discover it doesn't look after the starter battery. We've had B2B (DC-DC) chargers that have done this for ten years so kinda surprised given the Victron reputation.