TheSamba.com :: View topic - Renogy DC To DC converter & 100 Ah lithium house battery

Sat Apr 18, 2020 1:40 pm

Hello Everyone! I have an 87 Westy which I bought taken apart and am slowly... putting back together. (sat in a garage for 8 yrs) I am installing a Renogy 100 amp hour house battery (2nd battery) and dc to dc converter. I wanted to see if I could wire it this way? It would eliminate the 2nd battery kit and isolator (if it works :D )
Here is my crude wiring diagram>

What do you guys think?

Sat Apr 18, 2020 2:48 pm

So looks like the DC - DC charger and start battery connection is fine. Then you’re idea is to use the relay to run appliances off the main power at the dash while the engine is running and then the lithium battery with the engine off.

I’m not sure from your diagram where the power is coming from to the Relay to operate the camper fuses While running.
Why not just have the camper fuses attached to the lithium battery all the time? The battery will get power from the dc to dc charger while driving and will not require use of a relay.

Sat Apr 18, 2020 2:52 pm

I think if you wanted to do it your way, 30 would go to the camper fuses, 87 would go to main power at dash, 87a would go to the lithium battery. Then you’re blue wire I think is your 12v running wire. And then you need a ground for the relay. Is the red/black wire the ground?

Sat Apr 18, 2020 3:23 pm

beach_creature wrote: So looks like the DC - DC charger and start battery connection is fine. Then you’re idea is to use the relay to run appliances off the main power at the dash while the engine is running and then the lithium battery with the engine off.

I’m not sure from your diagram where the power is coming from to the Relay to operate the camper fuses While running.
Why not just have the camper fuses attached to the lithium battery all the time? The battery will get power from the dc to dc charger while driving and will not require use of a relay.

Thanks for your reply! My intention is to keep the operation of the camper wiring in the stock arrangement, not sure if this accomplishes that or honestly what the original arrangement was. (power to fridge only when engine is running?) The box I labelled "camper fuses" are the 2 stock red wires from the cabinet with the fridge/stove etc.

The power to the relay is the blue wire and the red/black from the dash I think is the ground.

Sat Apr 18, 2020 8:17 pm

looks good, you can also run the DC/DC to the same relay under the driver seat, just tap the blue wire for ign+

I would also put an easily accessible switch on that line. being able to take the load off engine/alternator during cold starts, intense climbs etc is a nice feature

Mon Apr 20, 2020 5:44 am

Thanks Guys! All good ideas and I am so happy to have help with this. I think I need to revsit how to wire a relay. I am still a bit confused and since the wiring for the van is not complete, I cannot test my set up for a while.

My next step is to figure out how to maintain/charge both batteries while the van is in my garage since 1 is lithium & 1 is regular. I had 2 thoughts and am going to call Renology & pro mainer tech support today:
--I have the 2 battery Pro mainer charger from GoWesty- can I use one of the inputs from this to go directly into the Renology converter? (doubt it but I will ask them)
-- Wondering if I can keep a single 20 amp plus battery charger/maintainer on the starting battery and make the DC to DC converter turn on with it to charge both batteries that way. (again I will be asking tech support)
-- Or fins a suitable 20 am 12 volt power source to power the dc to dc converter from 120 volts.

So many ideas, I just dont want to be using too many pieces of equipment, so trying to use the dc to dc to charge the lithium instead of getting another charger for home use.

Mon Apr 20, 2020 9:52 am

It’s bad to float a lithium battery, they also self discharge slowly, just make sure they are ~80% charged when you put into storage (and make sure you don’t have any parasitic draws). Put a maintainer on your starter battery, since the dc/dc charger is wired via ignition, the lithium battery is effectively separated while the van is in storage. I think you are overthinking your charger setup