Charging vehicle battery.

[IPLander]

I'm converting a Mercedes Sprinter 316 mobility minibus to a camper/motorhome. The engine battery goes flat after about three weeks because tacho and other items permanently connected.

I have fitted 480w solar panels charging a bank of lithium batteries.

Ideally I would like to be able to use the alternator to supplement the solar, particularly for winter and also for the solar pv to keep the car battery ready for use. Has anyone done this?

Any advice please. Much appreciated and thank you in advance.

 

[SquirrellCook]

Use a victron battery to battery charger using the leisure batteries and solar to hold up the engine battery. Don't you just love Mercedes!
I've not needed the alternator to charge the leisure batteries, someone else (David) will be along shortly to guide you.

 

[IPLander]

Use a victron battery to battery charger using the leisure batteries and solar to hold up the engine battery. Don't you just love Mercedes!
I've not needed the alternator to charge the leisure batteries, someone else (David) will be along shortly to guide you.

Thanks for your reply. Was thinking if I were to use it in Winter a boost from the alternator may be useful in low light conditions. The bus drives like a dream!!

 

[SquirrellCook]

I have an inverter I fitted before using leisure batteries connected to the engine batteries. Just to run the odd power tool in the event of a brake down. Though not the most efficient, I can run a battery charger from this whilst driving for the leisure batteries. Again I like to use the victron chargers as you can set them to suit your battery and they virtually go to sleep when they are done.

 

[wildebus]

I had the VW LT46 Minibus - so same chassis as yours and also had a tacho.
I was concerned about the tacho drain on the starter but it really only turned out to be a knackered battery - I would suspect your battery might be knackered as well?
FWIW, I bought this battery from Alpha Batteries - https://www.alpha-batteries.co.uk/019-nordstar-car-battery/ - and I found it really excellent.
The B2B will charge the leisure from the alternator but is one-directional.
If you want to maintain the starter from the lesiure charging systems - solar and EHU, you would want to fit some kind of trickle charger. word of caution ... there are quite a few around but when you have lithium, most are not suitable. the only one I am aware of that does work and has a programme for a Lithium Leisure and Lead Starter is the Ablemail AMT-12.
I do sell these, but that is not why I am quoting these. I would also say to hold off buying one and replace the starter battery first and see if you actually need one at all (depend on how you use the van and how long laid up between trips)

 

[Nabsim]

My motorhome is built on a T1n Sprinter 316 chassis and n Winter my starter battery will go flat in 3 weeks, sooner if very cold. I solved this when I fitted a Votronic Duo solar controller that sends a 1 amp trickle charge to the starter battery when solar harvesting. It can be done other ways as well.
I fitted a 30mp B2B to charge hab battery’s from the engine when it is running so it gets proper charge cycles

 

[Deleted member 12559]

I found the tachograph in my van took a small but significant current draw over longish
layups.
I removed the circuit fuse. Tacho isn't a legal requirement with private usage.
For b2b charging of the leisure batteries I installed a low output (15A) waterproof boatie
Sterling charger. My alternator is the original 55W @ 24v low output little bleeder. But then
I only use the van where the sun always puts back the Amps used in good time, so no imperative
upgrade. Each according to their own circumstances, to each their own solutions, so
it states in the self build bible.

 

[IPLander]

Thank you all for your replies. Something to ponder for a few days. Much appreciate all your help.

 

[trevskoda]

Im 12v so a voltronic split charger/solar 200w for me and a switched relay to connect the alt/starter batt to the pleasure batts.
I have a numax 10ah smart charger on board to do all batts in winter, all I do is drop the relay switch and all batts charged together, also handy for starting with all 3 connected if they are low, mind you I have never had to do as she is a first hit starter even without the glow plugs.

 

[wildebus]

I found the tachograph in my van took a small but significant current draw over longish
layups.
I removed the circuit fuse. Tacho isn't a legal requirement with private usage.
For b2b charging of the leisure batteries I installed a low output (15A) waterproof boatie
Sterling charger. My alternator is the original 55W @ 24v low output little bleeder. But then
I only use the van where the sun always puts back the Amps used in good time, so no imperative
upgrade. Each according to their own circumstances, to each their own solutions, so
it states in the self build bible.

You disabled the Tacho by removing a fuse? And you could drive with all other functions working?
That would, TBH, very unusual as they are designed to be tamper-proof to prevent drivers doing just that.
If you mean removing supply to Tacho when not driving, yup, no problem (if laid up could even just disconnect the battery potentially!)
On the LT I don't have a specific fuse for the Tacho but identified the circuit to it when I sorted out the nest of wires onto the starter battery +ve post and could remove the fuse I added for it to stop the draw. I found also that is would be good as theft protection as the vehicle wouldn't start when that was done. In the end a decent battery fitting meant I never had to bother but the option was there none the less.

 

[Deleted member 12559]

You disabled the Tacho by removing a fuse? And you could drive with all other functions working?
That would, TBH, very unusual as they are designed to be tamper-proof to prevent drivers doing just that.
If you mean removing supply to Tacho when not driving, yup, no problem (if laid up could even just disconnect the battery potentially!)
On the LT I don't have a specific fuse for the Tacho but identified the circuit to it when I sorted out the nest of wires onto the starter battery +ve post and could remove the fuse I added for it to stop the draw. I found also that is would be good as theft protection as the vehicle wouldn't start when that was done. In the end a decent battery fitting meant I never had to bother but the option was there none the less.

You've prompted me to recall actions of 27 years ago and why! The tachograph is electro/mechanical. When stationery
removing the fuse disables the clock and tacho body rotation, the speed limit warning light comes on briefly when the fuse is
replaced? Replacing the fuse when stationery makes the clock tick tock and the tacho body rotates.
When on the move, and fuse removed, the clock remains disabled as presumably does the tacho body rotation/operation,
hardly likely to do otherwise. (although I've never put a disc in to actually check), the speed limit warning indicator light also is inoperative.


The odometer/road speed dial connections are mechanical (Bowden cable). When the van is in motion the stylus
activates mechanically or electrically so as to scribe the paper disc. Probably not relevant, but the tacho is a so called
2 person type.

Your tacho on the LT I presume is a much more modern affair, all electronics.
Don't ask how I used to charge my 12v leisure battery set up from 24v alternator and 24v starter batts.
But it did involve a 60A 4 pole changeover switch!