Mppt or dcdc/mppt charger ?

[Spanners70]

Question for the gurus. Just done an order with renology, for a t6.1 2020 van. Got a 200 w solar panel with rover 20amp along with Bluetooth module. Before I start assembly, just wondering should I have gone for a renogy dcc30s dcdc with mppt rather than my rover charger? As far as I know I don’t think the van has a dc dc charger. For the real gurus, I have a cbe 300 box fitted in the space under the wardrobe. Presumably if I went with the dcc30s, I could use the terminals on the cbe300 for main and leisure battery and link to the charger rather than having to run cables to under passenger seat and engine bay to the batteries direct ?

 

[roadtripper]

Pictures of your setup will help folks understand your existing setup and advise.

If you have one of the "all in one" style of EHU charger and 12v distribution system they can sometimes be a challenge to disable the built in split charge relay and replace it with a DC-DC charger

 

[Spanners70]

Thanks road tripper. I bought the van converted so I’ve no idea what system is fitted, know there’s leisure battery under the passenger seat, in the back of the van is a cbe 300 box (just power distribution as far as I can tell) also a ds120 box next to it which I think is just for 240volt ac.beyond that I’m not sure what I have or where to look ? I’ve just got a 200w solar panel, rover 20amp mppt, fuses for both sides of it and the bt1 unit all from renogy. Wondering if it will work as is which think will. Or if need a dc dc charger as well and if so would combined unit eg dcc 30s or whether one of there 20amp dc dc separate box which could probably mount under drivers seat or in the back and hook the leads to the cbe300 terminals although the starter switch wire be a ball ache to run either way I assume

 

[roadtripper]

If you don't know what the existing installation is it's hard to advise if what you are proposing to add to it will work or indeed be safe.

As I say generally if you can take pictures folks around here can usually work out what you have and help advise, it's considerably harder to do that from just text.

 

[Spanners70]

photos as best I can. As I can tell the black box is charger when hooked to mains, the box with 3 cab in it for the mains system, the ds300 just a distribution box.the leisure battery is standard fitted by vw, pics as best I can under the seat without removing the seat, no signs of any other electrical boxes…hope that may help .

 

[ginkster]

You have the same set up as me. The ds300 has a relay in it to charge the LB when the engine is running and distributes the 12v power. It will also provide a trickle charge to the SB when you are on EHU. The black box is the mains charger for the LB (and starter via ds300) and is not lithium compatible if you plan to go that route.

The DS300 is not meant to go with a smart alternator, although it does work to a fashion. Some converters (e.g. Camper King) use the CBE kit but also fit a DC/DC charger that is hidden away behind the CBE kit. There is at least one thread about this on here. If they’ve done this it normally means a resistor in the DS300 has been snipped to disconnect the charger relay in the 300. I’ve decided I’m removing most of the CBE kit as I’m upgrading to lithium and solar and want something that is designed to work with a smart alternator.

I can post some links later tonight when I have a moment. In the meantime the instruction manuals for the CBE kit are available on 12voltplanet.

 

[Spanners70]

Thanks ginkster great reply ( and to roadtripper too) it’s not a camper king conversion. Not sure if there’s anything other side of the cbe but means unscrewing shelves I’m the wardrobe then the vertical bulkhead so not a two min job ti investigate further. I’m still 98z sure it will work as I posted above wiring the mppt into the distribution box just after reassurance !

 

[roadtripper]

Fundamental what are you trying to achieve?

You've mentioned that you've bought a solar panel and controller, but also mentioned adding a DC-DC charger.

If you are just adding solar then that should be possible without too much change.

If you are adding a DC-DC (and there are good reasons to if you need to be off EHU more often) then there is much more change that needs to be done. You'll at least need to disable the split charge relay.

Your solar panel and charger might not reach 20amps but on a good day you may well achieve 15amps and that's significantly more than just trickle charging so I wouldn't really advise piggy backing that on to existing circuits.

Ideally you would want the MPPT charger connected as directly to your leisure battery as possible and also a dedicated fuse to protect that connection (which it sounds like Renogy has included in the bundle)

 

[Salty Spuds]

Fundamental what are you trying to achieve?

You've mentioned that you've bought a solar panel and controller, but also mentioned adding a DC-DC charger.

If you are just adding solar then that should be possible without too much change.

If you are adding a DC-DC (and there are good reasons to if you need to be off EHU more often) then there is much more change that needs to be done. You'll at least need to disable the split charge relay.

Your solar panel and charger might not reach 20amps but on a good day you may well achieve 15amps and that's significantly more than just trickle charging so I wouldn't really advise piggy backing that on to existing circuits.

Ideally you would want the MPPT charger connected as directly to your leisure battery as possible and also a dedicated fuse to protect that connection (which it sounds like Renogy has included in the bundle)

without knowing the exact control philosophy of the CBE unit, I'm making an assumption that the relay closes when the engine is running & just connects the LB to the alternator in the same way that the stock VW second factory battery install does. If that's the case, the "new" DC-DC charger could be placed between the output of the CBE unit & the battery, the CBE unit will act as an ignition controlled supply to the DC-DC. This is all assuming that the supply cabling to the CBE and the CBE unit itself are capable of supplying the required current to the DC-DC charger.

 

[Spanners70]

Fundamental what are you trying to achieve?

You've mentioned that you've bought a solar panel and controller, but also mentioned adding a DC-DC charger.

If you are just adding solar then that should be possible without too much change.

If you are adding a DC-DC (and there are good reasons to if you need to be off EHU more often) then there is much more change that needs to be done. You'll at least need to disable the split charge relay.

Your solar panel and charger might not reach 20amps but on a good day you may well achieve 15amps and that's significantly more than just trickle charging so I wouldn't really advise piggy backing that on to existing circuits.

Ideally you would want the MPPT charger connected as directly to your leisure battery as possible and also a dedicated fuse to protect that connection (which it sounds like Renogy has included in the bundle)

Currently mid summer leisure battery goes flat after 24-48 hrs mainly the fridge even on low. Hence solar to hopefully get 3 days any more a bonus without hook up or engine going. Hence solar and the mppt. A dc dc was an after thought whilst modifying or dc dc with mppt. I’d be happy to just use mppt if it works.the positive on leisure battery goes to positive on the cbe hence looking at using the same terminal for the output from the mppt? Assuming I can do that to save running an extra wire round the van

 

[Salty Spuds]

Currently mid summer leisure battery goes flat after 24-48 hrs mainly the fridge even on low. Hence solar to hopefully get 3 days any more a bonus without hook up or engine going. Hence solar and the mppt. A dc dc was an after thought whilst modifying or dc dc with mppt. I’d be happy to just use mppt if it works.the positive on leisure battery goes to positive on the cbe hence looking at using the same terminal for the output from the mppt? Assuming I can do that to save running an extra wire round the van

What sort of fridge are you running? Compressor or thermoelectric?

 

[roadtripper]

Currently with a basic split charge your leisure battery is only going to be charged to about 80% from the engine as that capacity is left for regenerative braking on the 6.1 Start Stop system.

Switching to a DC-DC charger will add that additional 20%, which can be significant given you really shouldn't take an AGM regularly under the 40-50% region.

As you have the solar start with that, especially if it's mostly summer use. If you need more of an edge you can add DC-DC later.

At the currents batteries and chargers operate at it's best to avoid using more than one cable in the terminal as often they are sized optimally for the high current cable. When you start your van after a few days off grid and the very low leisure battery is ganged with the starter battery by the relay you will get significant current flow and you don't want an area of high resistance in your distro board. If there are additional free connectors on some sort of bus bar those could be used.

Looking at the instructions your distro board seems to use bolt terminals like a battery post. They may take two connections, but I would expect with the heavy guage cable there two connectors may splay apart like a V as the bolt is tightened and get uncomfortably close to the neighbouring terminal. Have a look with the cover off to see what your cable looks like.

If not you should be able to mount a bus bar (or maybe even a single post) very nearby and add a short ready made battery cable from there into your distribution board and move the existing cables and your MPPT cables to the bus bar.

Power Distribution | 12 Volt Planet

Power posts & busbars, cable jointing boxes and power distribution boxes with fuses. For use in cars, vans, trucks, motohomes, horseboxes, boats etc from 12 Volt Planet

www.12voltplanet.co.uk

 

[Spanners70]

Currently with a basic split charge your leisure battery is only going to be charged to about 80% from the engine as that capacity is left for regenerative braking on the 6.1 Start Stop system.

Switching to a DC-DC charger will add that additional 20%, which can be significant given you really shouldn't take an AGM regularly under the 40-50% region.

As you have the solar start with that, especially if it's mostly summer use. If you need more of an edge you can add DC-DC later.

At the currents batteries and chargers operate at it's best to avoid using more than one cable in the terminal as often they are sized optimally for the high current cable. When you start your van after a few days off grid and the very low leisure battery is ganged with the starter battery by the relay you will get significant current flow and you don't want an area of high resistance in your distro board. If there are additional free connectors on some sort of bus bar those could be used.

Looking at the instructions your distro board seems to use bolt terminals like a battery post. They may take two connections, but I would expect with the heavy guage cable there two connectors may splay apart like a V as the bolt is tightened and get uncomfortably close to the neighbouring terminal. Have a look with the cover off to see what your cable looks like.

If not you should be able to mount a bus bar (or maybe even a single post) very nearby and add a short ready made battery cable from there into your distribution board and move the existing cables and your MPPT cables to the bus bar.

Power Distribution | 12 Volt Planet

Power posts & busbars, cable jointing boxes and power distribution boxes with fuses. For use in cars, vans, trucks, motohomes, horseboxes, boats etc from 12 Volt Planet

www.12voltplanet.co.uk

Thanks for all that roadtripper looks like I was on the right wavelength with my initial solar mod. Should Be enough space on the terminal for a second from memory there about 20mm between terminals. Makes life a lot easier, although still have the battery temp probe to route tempting as it is to go with out.

It’s a vitrifrigo c51 fridge as fitted from the converters. Great info all thanks

 

[roadtripper]

Fitting the temperature sensor is ideal if you can but really only important if you regularly charge with the battery at very low temperatures but still strong sunlight. I don't think in your system the likely max 15 Amp is high enough current to warrant compensation from the heat generated by charging.

In a UK climate I doubt it will make much practical difference if you find you can't fit it. At worst the battery will charge a little slower on bright winter days.

 

[Spanners70]

Thanks roadtripper. Second battery under passenger seat so probably be ok. I shall try without and see. Thanks for all your guru gen today, been very useful

 

[ginkster]

Back! A lot has been covered while away. Great info. As mentioned, in essence connecting the MPPT to the posts in the DS300 is ok but it is tight and probably better to use some busbars to keep a single connection to the DS300. Pic of mine to show how tight it is:



It also worth having a look in the DS300 to see if the resistor has been snipped. If it has there is already a DC/DC hidden away somewhere. If it’s in one piece then the internal separating relay is doing the charging. As said above this will only give you about 80% charge due to the smart alternator. The resistor is in the bottom left corner of the DS300 and labelled ‘R37’ (some versions had a dip switch hence the on/off label too). Pic of my intact one here:



Links to the really rubbish CBE manuals:

DS300 manual

516 charger manual

Good luck and let us know how it goes.

 

[Spanners70]

What a reply ginkster thanks very much. Will be a couple of months project work and Xmas get in the way but hope to get the internal electrics in before mid jan. It goes to body shop mid jan (see another post where I asked about local places) so plan to do solar panel on its return so they don’t coat it in overspray or scratch it with sheeting. That repair leads to front and back dash cams going in as well, not sure they will get someone swapping lanes into my side but 5500 of damage on my insurance got to be worth a try. Hoping the connector 18 terminal 1 will supply ignition switched supply for it, must be one somewhere in there I hope haha

 

[roadtripper]

Having seen the bolt terminals I'd really strongly urge you to move the connection outside to a bus bar. There is not a lot of room there and it's not just "is there a bit of a gap left" when you nip them up you need to worry about but also what happens if everyday vehicle vibration loosens the nuts. Right now the cables will likely stay where they are and just hang there due to the loom, with 2 cables on the two left hand bolts in a V arrangement it's more likely the cable with more weight or tension is going to swing the cables together and short.

 

[Spanners70]

Slave fit of the boxes and it takes to my phone app Carnt be bad. Slight delay with the project now, solar panel be going up after the van returns from the body shop for new passenger, fuel filler & sliding door and minor repair to rear quarter post the idiot that swapped lanes into me with no indication or warning (double dash cams front and back now installed). Seems pointless putting the panel on when there’s going to be polythene sheets dragged over it or over spray going on a new panel.





As for dc dc charger looking at the distribution box looks like resister r37 has indeed been removed so presumably somewhere hidden away is a dc dc charger already in the van…?