Do I need a DC-DC Charger for my vintage motorhome Lifepo4 solar install?

[MisterSandals]

I assumed he misread the 25v limit. Ultimately that is the reason I decided to ditch that unit and go with a stand alone MPPT controller.

No i was confused for different reasons!
I keep forgetting that when there is a single power source, it can produce 50A of power from one source. But when there are 2 sources, each source is limited to 25A production (which would be the case any time the engine is running... hmmm, unless solar disconnected).

Anyway, i think you've made the right choice going with your current 40A DC-DC, especially if it can be throttled back (that's a good feature!).

 

[MisterSandals]

I spent 2 months in NZ backpacking and hitchhiking around both islands in the early '90's. Beautiful country!

Awesome! And i agree, stunning.

Here’s what Dunedin in the lower South Island looks like

The wife and i cycle toured there for 4 months in the late 90's. Both islands, tip to tip.
For some reason I still remember coming over the wooded ridge on the north of the bay and seeing Dunedin thru a light mist.

 

[Supervstech]

Good for acceleration and spending money, not good for stinky diesel and noise/vibration.

Yeah, if you don't like da KLATTA you won't like a diesel.
If you like double the fuel economy, and better acceleration, it's a decent option.

 

[kbeefy]

Yeah, if you don't like da KLATTA you won't like a diesel.
If you like double the fuel economy, and better acceleration, it's a decent option.

Coach gets 9mpg, a 2000 k2500 w/ a 6.5 and overdrive gets 10mpg towing.
That motor in a much heavier vehicle without overdrive...
And diesel here is 25% more expensive than gasoline. ($5.65/g today, ouch!)

I have 4 turbo diesels, I've done the math. It just doesn't work out.

 

[Supervstech]

Coach gets 9mpg, a 2000 k2500 w/ a 6.5 and overdrive gets 10mpg towing.
That motor in a much heavier vehicle without overdrive...
And diesel here is 25% more expensive than gasoline. ($5.65/g today, ouch!)

I have 4 turbo diesels, I've done the math. It just doesn't work out.

Yeah, diesel is higher here as well...
My sprinter with a MUCH more modern engine and overdrive with a locking torque converter eeks out 21mpg fully loaded, higher if I try to keep it under 65...
It's a shame diesel is more expensive...
I have 4 gm 6.5's and the ease of maintenance and the load handling along with the low cost parts keeps me running them, but without skill, I'd be in bad shape with them. NOBODY knows how to work on them...

I dont guess there's any way to squeeze in a 4L80 trans in there... being transaxle if I remember right.

 

[kbeefy]

Yeah, diesel is higher here as well...
My sprinter with a MUCH more modern engine and overdrive with a locking torque converter eeks out 21mpg fully loaded, higher if I try to keep it under 65...
It's a shame diesel is more expensive...
I have 4 gm 6.5's and the ease of maintenance and the load handling along with the low cost parts keeps me running them, but without skill, I'd be in bad shape with them. NOBODY knows how to work on them...

I dont guess there's any way to squeeze in a 4L80 trans in there... being transaxle if I remember right.

Thats the transmision and final drive bolted to a LS. They did make a light duty trans with OD, but I wouldn't put it in anything larger than a car.
I'm working on getting a 3.7:1 gearset for the final drive (factory is 3.08:1), that should wake it up a bit, but probably won't help with mileage.

I have a VW 1.9 Tdi, a Ford 7.3 powerstroke and 2x Ford 6.0 powerstrokes. I can get 20 out of the powerstrokes if I'm really nice and not towing.

 

[Supervstech]

View attachment 121406

Thats the transmision and final drive bolted to a LS. They did make a light duty trans with OD, but I wouldn't put it in anything larger than a car.
I'm working on getting a 3.7:1 gearset for the final drive (factory is 3.08:1), that should wake it up a bit, but probably won't help with mileage.

I have a VW 1.9 Tdi, a Ford 7.3 powerstroke and 2x Ford 6.0 powerstrokes. I can get 20 out of the powerstrokes if I'm really nice and not towing.

Looks like a split case th400 with a differential mounted to it...
I wonder if a retrofit locking TC exists for it?
Possibly a two speed diff swapped in for OD?
Just dreaming I bet...
My dad had a 28foot RV with a 454 and a th400, we were planning to swap in a TD6.5 and a 4L80 trans... until he caught the thing on fire and had to scrap it...

 

[kbeefy]

It is based on the TH400, called a TH425.
There was a variable vane torque converter they used in the 60's, think it was called a 'split shift' or something like that. They are pretty rare these days. Unsure if a more modern lockup torque converter could be retrofit in, theres no provisions for additional hydraulic circuits to the converter or in the transmission itself, that I'm aware of.
I have a gear vendors OD on my 7.3, it's too big to fit in the space between the trans and final drive. I suspect a 2 speed rear would also be too large, but thats the easiest way I could see adding another gear. It would be cool to be able to split each gear.

 

[kbeefy]

A planetary gearset in the offset adapter (portion that turns the transmision forward) would work, but I've never heard of anyone building one.

 

[Supervstech]

In my racing days we cut and plugged the TC hydraulics, and built a bronze sprag to drive the pump, machined on a clutch face and mounted it to a steel bellhousing and raced without a TC... ultimate lockup!
Three pedals at the line, and a reverse pattern drop shifter...
Pulled our full body 68Camaro into the 9 second pack with a small block chevy... 396ci...

I really need to pull it out of mothballs and drive that sucker...

 

[lexio]

I happen to have a 40A dc-dc charger still new in the box from a previous project.

if you have this one with a server power supply you can also make a normal charger out of it

https://www.amazon.com/HP-441830-001-G5-437572-B21-438202-001-Refurbished/dp/B07GRG296X/ref=sr_1_5

just connect the 12 v output to the 12v input of the dc-dc charger it will work
i`m doing that one in my rv

 

[kbeefy]

if you have this one with a server power supply you can also make a normal charger out of it

https://www.amazon.com/HP-441830-001-G5-437572-B21-438202-001-Refurbished/dp/B07GRG296X/ref=sr_1_5

just connect the 12 v output to the 12v input of the dc-dc charger it will work
i`m doing that one in my rv

I do not have one of those, but I am also looking for an AC charger. Is that AC-DC?

 

[lexio]

yes it is a ac to dc power supply out put is 12v 1200 watt so no worry on that one. needs to be at least 1000 watt
the 12v out put is also no problem the dc-dc will make 14.0v out of it. it does not need more then 12v to work
get your self a break out board like this

https://www.amazon.com/Ethereum-Mining-Supply-Breakout-Adapter/dp/B09PLK6BJJ/ref=sr_1_1_sspa

or solder directly
server power supply's are rock solid
sorry no photos of it, but working great in my case

 

[lexio]

there it is
i have a 60 amp version made a switch between it so i can switch between 30 amp alternator and 60 amp shore charge

 

[Supervstech]

there it is
i have a 60 amp version made a switch between it so i can switch between 30 amp alternator and 60 amp shore charge
View attachment 121427

The non tinned bussbars on your build will cause issues in the future if your terminals are aluminum...

 

[lexio]

yes i know will keep a eye on it cant get nanolox in Holland
but thanks

 

[Supervstech]

yes i know will keep a eye on it cant get nanolox in Holland
but thanks

NoAlOx will help, but nickle plating is fairly easy, and works better.

 

[lexio]

maybe a winter project, my rv is now in winter storage and have removed the battery's from it
so i have a little time to work on it.
seems fun to do it.