[83Grumman]

From Kisae Manual

3. UNDERSTANDING THE UNIT The DC to DC Battery Charger is a fully automatic multi-stage, multi-input battery charger with the ability to charge from either an alternator linked to a battery or via solar power with its built-in Maximum Power Point Tracking (MPPT) Solar Controller. With two inputs available, the house battery will be charged from either the engine while underway, or via the solar panels when stationary. The process to choose either engine or solar is fully automatic and both functions are controlled from within the unit itself without the need for external relays. During normal operation, the DC to DC Battery Charger will do a full charge cycle to float stage on the House Battery Bank with the ability to choose either GEL, AGM, Flooded, Custom Programmable or Lithium. Once the float stage is reached the charger transitions to a power supply mode to support any on-board DC loads.

 

[GaryBIS]

Hi,
The max solar input voltage on the Kisae DMT 1250 is 50 volts, so it should be fine for your panel. This is the manual: https://www.kisaepower.com/wp-conte...nual_DMT12V_24V-Series_Rev-D_190612_Print.pdf

There are pros and cons to using the combo solar charger and DC to DC charger rather than separate units. I don't look at the Kisae so much as a combination of two units, but more as a gadget that can charge the house battery from two different sources. This saves some components and money and simplifies the wiring. On the other hand, if for some reason you have a need to upgrade the solar charger or the DC to DC alone, you are stuck with getting a whole new unit.

I hate to put even more stuff on your table, but we did just get through with redoing our van electrical system after 8 years of use and we tried to make it as efficient, safe and easy to build as we could. It might be worth a look through to see if there are parts of it you can use. Its documented in mind numbing detail here...
For example, one of the things we got rid of was that Progressive Dynamics fuse box and AC distribution center - our conclusion after 8 years of use was that its a much more complicated AC distribution system than we need or want.

Gary

 

[dog_house]

Take this as my opinion and nothing more, but I am a fan of directly charging LiFePO4's through a properly set up isolator. Then you can just use a solar controller to be a solar controller. It's simple and efficient. The downside is you will need 2awg wire to hook it up. Isolator or DC to DC don't forget to have a way to shut off all of the chargers when it's below freezing unless your batteries have a reliable low temperature cutoff in the BMS's.

FYI actual testing on our 2022 with the 180a alternator proves there is between a 60 and 120 amp surplus at idle for the charging system when the alternator is hot. With an isolator (direct) system the batteries stop charging when the alternator is fully loaded and can't keep up. The DC to DC chargers pull around 120% of their rated output so this is where the 50a max charger output recommendation comes from when you have the 180a alternator.

 

[SteveSS]

The DC to DC chargers pull around 120% of their rated output so this is where the 50a max charger output recommendation comes from when you have the 180a alternator.

Renogy says 150% for theirs, although I've never seen that much (yet). 50A max for the 180A alternator (60A for the 220) is based on Renogy's guidelines, but that's probably a safe, conservative guideline for most all DC-DCs.

 

[Motor7]

Have to be honest, I am leaning towards the Kisae DMT1250.....

I do think I need a separate battery monitor though......DMTRM1201

 

[Motor7]

What is the consensus on LifePo4 batteries in really cold weather? Heating pads, or a temp monitor to turn off charging...or both? Our van could very well end up in Manitoba....in January🥶

 

[Bromaster5]

What is the consensus on LifePo4 batteries in really cold weather? Heating pads, or a temp monitor to turn off charging...or both? Our van could very well end up in Manitoba....in January🥶

Not my business, but, did you get tired of the low ballin tire kickers trying to shred your valuation to pieces??

Are you keeping the van? Did I miss something?

 

[GaryBIS]

Hi,
I used a low wattage (12 watts) heater pad under each of my 2 LiFePo4 batteries. The heaters are low enough wattage that they don't need a temperature controller to regulate their temperature.
The two pads are on a switch which I turn on manually on those rare occasions when I need them.
The most common case is that its winter and cold and the van has been cold soaking out in the driveway for days and we want to leave on a trip. I turn the heaters on when we leave or the night before and it warms up the batteries. Once the batteries and van are warmed up, the heaters are not needed even if its really cold outside.


This is the temperature plot for heaters on..

The red is under the battery near the heater.
Blue is top of battery temp.
Green is outside ambient

Looking down into the battery compartment with the heater in place.
The heater pad has paper stuck to it from a previous experiement.
The black box is one of the two SOK batteries.

I have the SOK batteries - if I were buying them again, I'd buy the new models with built in heaters, as they don't cost much more.
Whether you need the heaters depends mostly on whether you want to be able to take winter trips in the van in cold climates - we do

Gary

 

[Motor7]

Not my business, but, did you get tired of the low ballin tire kickers trying to shred your valuation to pieces??

Are you keeping the van? Did I miss something?

Actually, I did not get an offer, but had two interested parties that I think were serious. After adding up everything, I had $10k in accessories/add on's & the wife convinced me to BUILD IT! Turns out, she was....rrrr...rrrrhhhh,,,,rrrah...rright!

 

[Motor7]

Hi,
I used a low wattage (12 watts) heater pad under each of my 2 LiFePo4 batteries. The heaters are low enough wattage that they don't need a temperature controller to regulate their temperature.
The two pads are on a switch which I turn on manually on those rare occasions when I need them.
The most common case is that its winter and cold and the van has been cold soaking out in the driveway for days and we want to leave on a trip. I turn the heaters on when we leave or the night before and it warms up the batteries. Once the batteries and van are warmed up, the heaters are not needed even if its really cold outside.


This is the temperature plot for heaters on..


The red is under the battery near the heater.
Blue is top of battery temp.
Green is outside ambient

Looking down into the battery compartment with the heater in place.
The heater pad has paper stuck to it from a previous experiement.
The black box is one of the two SOK batteries.


I have the SOK batteries - if I were buying them again, I'd buy the new models with built in heaters, as they don't cost much more.
Whether you need the heaters depends mostly on whether you want to be able to take winter trips in the van in cold climates - we do

Gary

Most excellent!

 

[RV8R]

I appreciate all the responses and info...it is a bit overwhelming at times, though. Hat's off to the pro's here that do this stuff in their sleep 😎

Looking at this dc to dc/solar chager:

Amazon.com: KISAE Technology DMT1250 Abso DC-DC Charger, 50A : Automotive

Buy KISAE Technology DMT1250 Abso DC-DC Charger, 50A: Battery Chargers - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

Rated voltage on my 310watt panel is 37.2v....and I am having trouble finding the input voltage of the Kisae & Renogy.
Victron 12/12/30 says 8-17v.

I like the Kisae ,,, do not have one, but if Inwanted a DC2DC that one is @ the tip of my list ,,, Why ? ,,, I read the manuals & it is very “User Programable”.

Not sure of the dual “alternator/solar” function, but it can be used as a DC2DC only as far as I know.

 

[RV8R]

What is the consensus on LifePo4 batteries in really cold weather? Heating pads, or a temp monitor to turn off charging...or both? Our van could very well end up in Manitoba....in January🥶

It depends on how you want to use your van & the factors.

I use AGMs as my electric needs are minimal & I am often in sub freezing temps. Not all AGMs & Lithiums are equal.

My AGMs are good anywhere I would want & how I want to use them - temperature wise. But my systems are basic & do not need the “Pros” of lithium due to the “Propane I use.

SOK factory heating batteries have “reportedly” had issues, so even though @GaryBIS seemingly has heating pad envy, think he is lucky to have created his own heating pad system;

https://diysolarforum.com/threads/sok-bms-incorrect-abc-bms-on-app-store.51920/

Also if you buy a Victron BM712 Smart ,,, it has “relays” capable of temperature controlled ,,, as far as I know.

If you want to know more about “Lithium” & Cold 🥶🥶 ,,, Check out this thread & site in general ( you might see some familiar “handles” 😁 );

https://diysolarforum.com/threads/upgrade-off-grid-cabin-in-cold-climate.54764/

 

[RV8R]

310 watts of solar, 2,000 watt inverter, 2- 100amp LifePo4 batteries.

I think I want shore power separate from the 12v solar system to power the roof air and a few outlets just for simplicity. The biggest power hog will be the Eccotemp 2.5 water heater with it's 1440 watt element, so it will plug into inverter when rolling, and plug into shore power outlet when at campgrounds.

I have looked at a bunch of wiring diagrams, and have not found one to match what I think I need. I am confident doing general electrical work, have put in two independent solar systems on other campers, but am not too confident on building a system from scratch.

So far I have:
150 amp battery isolator
12 led puck lights
2 led reading lamps
2 dimmers for pucks
Progressive Dynamics Power control Center fuse box
12v iceco fridge/freezer
diesel parking heater
Renogy Voyager 20amp charge controller
inline fuses & disconnects
10ga Anchor wire for solar panels
4ga for batteries

As to the Battery to Battery charger....what size? They start at 20amp, and go up to 60+amp. Bigger is most likely better/faster, but the larger one's seem to be overkill?

This diagram is close....good enough to work with/modify?

Ok, go slow with me...."Mongo not no how 2 spel,...Die AH Gram"

Hey @Motor7

I read you are going to draw on this diagram with your crayons 👍.

I actually think you could do getter from scratch.

The first electrical design thing to pencil out is a load chart 12vdc & 120vac. Any idea of that item?

 

[Motor7]

Hey @Motor7

I read you are going to draw on this diagram with your crayons 👍.

I actually think you could do getter from scratch.

The first electrical design thing to pencil out is a load chart 12vdc & 120vac. Any idea of that item?

I have all the appliances here, I just need to go through them and write the loads down. Homework to do for sure....

 

[RV8R]

I have all the appliances here, I just need to go through them and write the loads down. Homework to do for sure....

Yup ,,, The Homework 👍.

Post #67 here;

If you use the spreadsheet program “Excel” you can download this spreadsheet program file & plug in your loads etc.

I uploaded the file after changing it to an .pdf extension ,,, but you can download it & rename the file with a .xls & it works with “Excel”. I do n know how or The Forum does not accept .xls files.

Solar Panel, electrical system, batteries - Van build Canada

Hi @ramp Here is an under chassis tank from @Curious Campervans https://curiouscampervans.com/products/promaster-undermount-water-tank-15-gallon I agree with @GaryBIS on the Maxxair fan energy ,,, I think you are way high on the energy usage. Regarding your “Load Chart” ,,, I am following it...

www.promasterforum.com

It is really an extremely simple spreadsheet that uses the following equations;

Volts * Amps = Watts

Watts * Hours = Watt Hours or (Whrs)

And maybe an inverter efficiency % ,,, like ( 1000W / 90% efficiency = 1,111 Watts Needed )

All “Theoretical Values”


Regarding “Inverters” ,,, If you design a system that needs them to be on standby ( I am considering it for my Cabin Fridge ), you have to allow for standby energy to be wasted. In my case 20W per hour @ standby mode assuming 16 hrs out of the 24 hr period = 320Whrs. The current 12vdc Fridge I have is “rated” @ 21Ahrs per day @ 12 volts or 250Ahrs per day.

So just the 16 hrs per day of inverter standby energy is 128% of the fridge energy used 😳 ,,, for me that is significant. Also ,,, And this is just a big leap/assumption on my part & would only matter if attempting to keep your van cool in the summertime ,,, what happens to that wasted electrical energy?? ,,, I (non-researched) assume it turns into heat.

 

[Motor7]

The IceCo fridge says .545kwh(24hrs), so converting that to amp hrs I get 45.417.....so that number should be divided by 24(if it''s running 24 hrs a day)? Sooo, 1.89 ah average?

 

[RV8R]

The IceCo fridge says .545kwh(24hrs), so converting that to amp hrs I get 45.417.....so that number should be divided by 24(if it''s running 24 hrs a day)? Sooo, 1.89 ah average?

So ,,, it might math like this

545Whrs @ say running 10hrs per day so 54.5W when running with a battery voltage supplied @ fridge of 12.5 volts ,,, so might be 4.36 amps while running.

or it could be

545Whrs @ 14hrs per day so 38.9W when running @ voltage of 12.7 ,,, 3.0 amps when running.

 

[Motor7]

Oh this stuff hurts me pea brain,,,,,,,,,,

 

[GaryBIS]

Hi,
This page has some common camper van loads and how many amp-hrs they use per day - and some info on tradeoffs on using electricity to power things vs fossil fuel.

Camper Van Electrical – Planning the System – Build A Green RV

www.buildagreenrv.com

I tested my fridge over 24 hours and it used 42 amp-hrs over 24 hrs - this seems to be reasonably close for the small 12 volt compressor fridges used in a lot of camper van.

Gary

 

[RV8R]

Oh this stuff hurts me pea brain,,,,,,,,,,

https://cdn.shopify.com/s/files/1/0053/1536/2906/files/ICECO_VL_PRO_Single_Zone_144c913b-707a-49e1-a37d-050bfe10aa37.pdf?v=1662365587

Part of the “Problem” is @Motor7 the “Manufactuers” are not really “forthright” with the performance specifications. So you have to search around & research & make assumptions in regards to “All Sorts of Things Electrically”.

It is my pet pev. But in the end, just design your system not to run @ 100% ,,, & you should be fine.

What model fridge you got ??