Van rewire project using Renogy DCC50S and Lithium

Cheers - I think I can squeeze the DC-DC charger into where the lifepo4 is going. If I go for 6 metres of 25mm cable at 14v over the 6 metres for 60A I get a drop of 0.5v which is OK for the Renogy charger based on their specs apparently.

I've also found a chassis earth point right underneath the fitting location which the original converter was using - I can replace the current -ve cable with a bigger 25mm over a 2 metre run which is great.
 
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Another update. I can run 35mm from the starter battery to the drivers seat then 25mm from there to the renogy dc charger at the LB location as i cant fit 35mm all the way to the LB due to panel space etc.. I'll join under the driver's seat using a heavy duty junction shown below.

That should reduce voltage drop also? Would that be better?


41E-m1So1LS._AC_SL1007_.jpg
 
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I would think that any gain you’ll get from using 35mm for a couple of meters will be lost because of the junction. If you’re siting the DC-DC next to the LB then it’s not as critical. Just run 25mm all the way.
 
Deaky said:
I would think that any gain you’ll get from using 35mm for a couple of meters will be lost because of the junction. If you’re siting the DC-DC next to the LB then it’s not as critical. Just run 25mm all the way.
Click to expand...

Agree, plus running 25mm the length of the van is going to enough of a pain as it is without a 32mm chunk and join.
 
Success so far. Running 7 metres of 25mm from the starter battery to the leisure battery located right next to the rear wheel arch (lwb) gets me 14.2 volts with the engine running. Minimal voltage drop.

20220201_134245.jpg
 
You might know this already, apologies if you do, it’s in @Dellmassive excellent extensive posts about the Renogy unit. If you connect a solar panel to the unit it will restrict the alternator charge current to 25A.
You can get the full 50A by putting a switch in the solar feed and turning solar off when you want full alternator charging.
Maybe at night or a short run between campsites. From my limited testing of the one I have this works great but even if the solar panel is not generating current it will restrict you to 25A.
The one I have has been great, with a 160w panel on the roof and a 100ah TN LiPo it keeps running fridge and lights practically indefinitely. Even in the winter with a diesel heater it lasts much longer than my water and waste.
 
Just been thinking - if my dc - dc charger is pushing out 14.6v when charging the battery is this going to be a problem for my 12V cello TV?
 
Most leisure batteries will be well over 13vdc anyway so I wouldn’t worry about it. If you can find the technical specifications for the TV set it probably has a good working voltage range.
 
With too high voltage led strips will
a) have reduced life time
b) consume more power than they should
c) perhaps vary in brightness as charging comes / goes

I used 8-36V to DC12V Auto Boost Buck Power Converter Voltage Stabilizer Regulator 120W | eBay to provide stable 12v for sensitive circuits. I would definitely recommend stabilized voltage for any modern electrics that don’t specifically list input of up to 15v. Obviously products intended for use in cars *should* stand higher voltages by design.

Stabilizer itself eats some power so better also have leisure circuits switchable to prevent battery drain when not in use.
 
n10n said:
With too high voltage led strips will
a) have reduced life time
b) consume more power than they should
c) perhaps vary in brightness as charging comes / goes

I used 8-36V to DC12V Auto Boost Buck Power Converter Voltage Stabilizer Regulator 120W | eBay to provide stable 12v for sensitive circuits. I would definitely recommend stabilized voltage for any modern electrics that don’t specifically list input of up to 15v. Obviously products intended for use in cars *should* stand higher voltages by design.

Stabilizer itself eats some power so better also have leisure circuits switchable to prevent battery drain when not in use.
Click to expand...
Having slept on this - I actually think I can work around this - the TV won't be used whilst driving anyway, just like the lights and so they will be using the battery voltage when stationary. . I might actually stick with using the PMS3 unit minus it's charging system for the USB, fridge and lighting outputs as that will filter out the voltage spikes from the DC-DC charger as well as providing 12v dc when on hookup.
 
bladerunner1968 said:
Just been thinking - if my dc - dc charger is pushing out 14.6v when charging the battery is this going to be a problem for my 12V cello TV?
Click to expand...
If it is designed for Motorhomes it will possibly run off variable voltage? Up to 15?
 
bladerunner1968 said:
Success so far. Running 7 metres of 25mm from the starter battery to the leisure battery located right next to the rear wheel arch (lwb) gets me 14.2 volts with the engine running. Minimal voltage drop.

View attachment 144385
Click to expand...
This test in the photo tells you the voltage with no load connected. Volt drop only occurs when there is a load connected. You could have used 0.1sqmm cable and got this same reading.

A 25A load 7m away from the source (14m of cable in total) with 25sqmm cable will have about 0.27V dropped. If you make the -neg connection through the chassis (as @Deaky says) with VERY good connections, you could improve this a lot, the chassis volt drop should be negligible.
 
To provide an update: I've got everything connected but... There is a problem!

Something 'kill's the charge into the new lithium after 20 seconds or so when the DCC50S is on the 50A setting, 1 minute or so when on the 40A setting but is fine on the 30A setting.

Any ideas on where to look? The lithium BMS input amp is set to 100A so that shouldn't be a problem and the battery is currently at 10% charge. The DCC50s boost charge setting is set to 14.0v which is what the battery initially requires

Have I run into the limit of the VW 12v system (I have a T5 with air con)?
 
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