I experience the same thing with my setup. My DC-DC pulls 30a and the 120/12v charger provides only 25a, so the starter batteries pick up the 5a difference. On two group 27’s the DC-DC draw drops below 25a after an hour or so the charger catches up and then tops the start batteries up. I did some starting tests on the worst case scenarios and it seems to start fine.
I’d you leave your setup long enough does it catch up and charge your starter battery? I would recommend you increase your 120v charger over decreasing your DC-DC. I am running a Victron Bluesmart IP67 12/25 charger hard mounted in the engine bay and it’s been working great. I just keep it plugged in all the time.
It was keyed originally; but I needed a solution that will allow the battery to activate the heater when the rig is parked. In the winter, I generally only use the truck for skiing so it mostly sits parked in the driveway. The keyed solution was already wired to a switch so I could turn it off once the alternator charged the system.
I think Chuck’s theory below is correct. It’s probably more financially feasible to increase the charger side. I’m going to try everything again today with a Current Limit, and see if it tops up the battery. When I’m actually using the rig I’m never in a place to have Shore Power, so non of this is a problem. When the battery gets cold I turn the truck on and turn on the DCDC charger. It’s actually rare because once I’m parked the diesel heater keeps the box warm enough for the battery to not go into charge protection.
On another note, Scott, this is why I thought I would document my woes so people could see the fuckery that goes into having a heated battery.
YES!!! Thanks dude, I’m going to look into that charger. That’s similar to my setup; the charger is under the hood. Difference being it is clearly not big enough to keep up to both batteries (as described above). Now to find the money to upgrade.
@Dignon, Thought I would share some info that might be useful for you. It’s still very early but I think I solved my issue of the Renogy DCC50S activating the low-temp cut off in subfreezing temps (need to verify once it gets back down <1*C). My goal was to see if I can turn off the low temp protection on the charge controller so it could send DCDC/solar power through to the SOK LiFePO4 heater circuit and warm the battery to take a charge. Not worried about protecting the battery because it has it’s own BMS.
I bought the Renogy BT2 Bluetooth Dongle and used the “Renogy BT” Android app to reconfigure my unit.
The other Renogy app, “DC Home” didnt have as many settings to configure. Changed the battery type to “USER” and copy and paste the Lithium configuration to “USER”. The idea is that it won’t activate the low temp protection under USER battery profile. The Lithium battery profile, the low temp cut off is baked in and can’t be turned off. I also currently have the BTS (Battery Temperature Sampling) cable disconnected. It looks like it has an internal probe. On the plus side, I can limit the charge controller output to 20A to keep the battery as healthy when fast charging isn’t needed.
Oh man, Ron! This is right up my super nerd alley…I like your style. I’m going to check out the BT app, as yes; the DC HOME app sucks! Unfortunately with the standalone DCDC charger there is no connectivity for monitoring…if you can believe that. The good thing is that if I have the truck on shore power charging the truck battery, when the voltage hits the charge request limit. The battery allows a charge to be delivered once the battery is warmed up.
Internal battery temp hit -32C a week and a bit ago, all power was dead in the truck. * I forgot all about the rig* Needless today, I posted in another thread, I’ve ordered a 20A DCDC charger and just picked up my Optima Yellow top. Theoretically, now I should be on par with what @Chuck.D has cooking. I’ll current limit the DCDC charger (10A) which is what the NOCO charger is under the hood. When the Lithium calls on charge, it’ll pull the 4A’s it needs to heat it up, then start charging at a max of 10A. This way the truck battery should be out of the Amperage equation…I think…otherwise I’ll be destroying another truck battery. I’m hopeful that it doesn’t just pull the 10A off the truck battery leaving the charger to try to keep up. I’ve thought of putting in a battery disconnect switch under the hood to switch the charger between the house and truck battery…but that’s even more f’ing around.
It’s good to know that DCC50s has a low temp cut off, I’m starting to see that renogy has some quirks that maybe Victron or redarc don’t.
If I ever redo my system down the road, I’ll be switching to Victron components. For my needs, I think it offers the flexibility of having advanced parameter controls, and is easier to source parts. Already bought their Smart Shunt and have been happy using their app. You can demo the components in the app btw!
Luckily I’ve just found your conversation! I’m experiencing similar issues with our Renogy set-up and thought that maybe you could help. We just came back from a week in our camper van, average temperature between -8°C to -17°C. It was our first time trying our new 100Ah self-heating battery and we were quite disappointed because it never turned on the self-heating function. We have a solar panel on the roof and I didn’t expect to turn on the heater with that in winter, but during several hours of driving I did expect that the heater would turn on eventually and charge the battery once over 0°C. Am I wrong?
We were lucky to have enough electricity for our hole trip, but now we have to charge the battery back in the house which we didn’t intended with our setup.
Do you have any ideas why the self-heating function never turns on? Is this due to the DCDC50 that won’t put the necessary 4A through to trickle the heater? Or could there be another problem?
I’m going to assume your DCDC is a Renogy unit? I fixed mine if you read my above post for details. A lot of things maybe applicable in your case. If so, reconfigure the Renogy DCDC controller to user battery profile and adjust settings as needed. If your using the Ethernet cable from battery to DCDC controller, you might need to disconnect it.
Thank you Ronmastas. You are right, it’s a Renogy unit. I will try to reconfigure it like you did. Everything working fine for you now?
Are you sure it won’t crush the battery when the charge comes through and it’s still below freezing? The battery says it’s “smart” but I still have my doubts
Is 20A the “healthiest” way to charge the battery? I thought the DCDC is taking care of that.
