Camper Conversion Battery issues. Over/Under charging.

[paulrichardson]

Hi Guys,
I think the charging system for my MK7 camper needs to be more intelligent.
I've got so many bits that I keep having problems.
A couple of years ago I managed to boil both batteries (cheap solar controller went wrong) and I have just discovered that with my new Victron solar controller I now have both batteries completely flat.
I built the system up bit by bit, starting with a split charge relay then adding separate CTEK mains chargers, one for each battery, then I added my Solar Panel and controller.
Has anyone got one clever bit of kit taking in mains, battery and solar power and splitting it to two batteries, sounds easy enough?
If not, why does my system keep going awry.
Paul

[mjsroofing]

What about this

https://ebay.us/m/60PAKt

[paulrichardson]

What about this

https://ebay.us/m/60PAKt

I don't think that's what I'm looking for, but thanks for the suggestion/

[bortaf]

how is your current setup wired ?
how do you charge 2 batterys with 1 charge controller?, a BtoB is better but not essential if you have lead acid batterys for both.
If you have a split charge relay there's no need for 2 chargers just charge the starter battery and the relay will kick on once the Voltage level is high enough and charge the 2nd battery, no matter where the charge comes from, be it mains, solar or alternator, just make sure the small neg wire for the split charge relay is on the main battery (the one that takes the charge) as it's the voltage sense wire, if it's not on the first battery it will alter the sitching carecteristics of the relay.

[paulrichardson]

how is your current setup wired ?
how do you charge 2 batterys with 1 charge controller?, a BtoB is better but not essential if you have lead acid batterys for both.
If you have a split charge relay there's no need for 2 chargers just charge the starter battery and the relay will kick on once the Voltage level is high enough and charge the 2nd battery, no matter where the charge comes from, be it mains, solar or alternator, just make sure the small neg wire for the split charge relay is on the main battery (the one that takes the charge) as it's the voltage sense wire, if it's not on the first battery it will alter the sitching carecteristics of the relay.

Thanks for the comprehensive reply, much appreciated.

I presently have two CTEK chargers one wired to each battery.

The two batteries are "Joined together" via a Durite Voltage Sensitive Relay (which I thought worked in both directions) with it's negative wire grounded to the chassis.

The Solar charge controller connects to the Leisure Battery. (My thinking was if we're not on hook up the main demand would be from the Leisure side.)

If I only use one mains charger what amperage would you suggest? Both my batteries are lead acid batteries about 90 ah each.

If I just have one mains charger were should I connect the Solar output? I'm guessing you would connect it to the starter battery and let it feed across.

We don't use the van all year so in the "off season" it's on our drive hooked up. if that changes anything.

[bortaf]

Yep the split charger will work in both directions if you use a common chassis earth, whichever battery reads over the threshhold it'll switch on
If it's just trickle a charge for in storage i'd only use a 5A charger, (tis what i use) Ctek are great, i have a 30A on mine for shore power, i use solar to trickle for storage but obv with no sun that's not happening, i have 400W on the roof and some days i still get nothing at all but any kind of sun for over an hour and my whole system will reach float BUT it's a lot of solar for just keeping batterys topped up in storage ! i usually use a minimum of 50W per battery just in case, you can't have too much solar, only too little but it's allways a compromise between covering your arse in winter and having way more than needed in summer, you never get it fully balenced, i strive for surviving winter and just accepting i have too much in the summer and some power is waisted.
If i was setting up similar to yours i would put solar on the leasure and charger on the starter same as you've done, with the common ground durite sharing power no matter what battery is full.
One thing i notice with the victron MPPT is it wont start to charge untill the solar input voltage is at or over 18V (5V over battery voltage) so if you have low voltage solar pannles like 18 to 25v OCV you might find on overcast days the voltage is too low to get anything, that's where a PWM charge controller wins, as soon as the panel voltage is higher than the battery voltage it'll charge, so you may need higher voltage panels with the victron MPPT ?

[paulrichardson]

One thing i notice with the victron MPPT is it wont start to charge untill the solar input voltage is at or over 18V (5V over battery voltage) so if you have low voltage solar pannles like 18 to 25v OCV you might find on overcast days the voltage is too low to get anything, that's where a PWM charge controller wins, as soon as the panel voltage is higher than the battery voltage it'll charge, so you may need higher voltage panels with the victron MPPT ?

Thanks again for your advice.

I used to have a "cheap" PWM charger, but it went wonky and boiled both batteries.

I replaced it with the Victron for 3 reasons:- I heard they were very reliable, I can see via Bluetooth what it is doing (and what it's done) and I thought MPPT was supposed to be more efficient than PWM.

I'm not sure what voltage my panel is but it wasn't very expensive, so I suspect lower rather than higher voltage.

I'll take a look at the Victron history and see what if I can identify the panels output.

[bortaf]

Pwm are fine, victron still make them AFAIK and 3 of my car systems use PWM (renogy) controlers, mppt is more efficient but that doesn't meen PWM are no good they are fine for low W and V systems and where there's no chance of shading, mppt corrects quicker although not all MPPTs are equal, victron mppts are way quicker than the EPever and renogy to find the mppt point, IME, the main issue is cheap chinease electronics are very hit and miss, ive had a few and out of the 5 only 1 is still going fine after 5 years, the exact same make controler went tits up 4 other times like you boiled my shed batterys, i replaced it with a victron 75/10 and cos i had an 18V panel i had to change to a 25v pannel , i got less with the victron than the £4.95 cheapo PWM, i was gutted to say the least 50 sheets down the drain, then i checked the panel output and read the spec sheet on the brightside it saved me £20 buying yet another BT battery monitor as it tells me that by it's own BT, the history tab is usefull as well

[paulrichardson]

Hi again,

I only have room for the one solar panel I already have, so increasing my solar is not possible, I'll pop my starter battery back in today and connect up the Victron, so I can look at the history of the panel and try to find it's output voltage (I remember it was rated at 100 Amps)

Our usage is in 2 distinct seasons (quite common I would think) the van never gets used at all during late autumn, winter or early spring, during these times it is SORNed and never goes out.

For one month we go to Europe where we wander around staying overnight at Aires (often without hook up) during the wandering and staying at sites with a hook up for 2/3 days.

The rest of the time we might have 3 or 4 short outings 3/4 days in the UK with about 50% of our stays having a hook up.

I need to try take in all of the valuable advice you have given, and get the best setup I can for us, using the equipment I have already and replacing one dead mains charger with something??

My Split charge relay will obviously do whatever I want it to do, so the questions are:-

Which battery should I connect the Solar charger to? (I'm leaning towards the Starter Battery)

How many Mains chargers should I have? (I think I would feel more comfortable with two).

Do you think, I'm making sense?

[bortaf]

I get what your saying, there's no problem having 2 chargers, you'll get more charge into the house battery with 2, once the starter battery is full it'll add charge to the house battrey via the split charge so win win IMHO
I'd put the solar on the house battery, then the split charge relay will top up the starter battery when it's sitting about and prioritise keeping the lights on when camping.
Good news on the battery coming back , just keep it in mind it's probably not 100% any more, you could allways have folding panels to deploy over the winscreen if you find you need more or hang on the side of the van, they do cost a bit though

[Radiofence]

Have you thought about a victron inverter charge controller?
A victron smart shunt on the leisure battery. Plus an isolated b to b charger ?

I keep my leisure batteries completely isolated from the vehicle 12v.
With charging systems becoming more complex, I prefer to keep them separated.

I just top up my leisure batts with my honda inverter generator if I think it needs topping up. I know everyone says flex panels are terrible etc, but I have two glued to the roof. Had them for years and they are fine.
With the smart shunt, u can see what's going in / out etc.

Just my pennies worth...