12 volt to 24 volt charging.

[Malcolm Bolt]

The base vehicle is 24volt using 2x12volt batteries.
The leisure side is 12volt using 4 batteries.
The 12 volt leisure side is kept topped up by the solars.
The alarm is wired to base vehicle circuit.
When parked for lengthy periods the 24volt side drains down.
Can a battery to battery charger be used to keep 24 volt side topped up?

On line I have seen a unit to charge 12 volt from 24 volt but not the other way round.

 

[DBK]

A quick search on Amazon for "12 to 24 volt converter" threw up several. How efficient they and whether the steady drain might be an issue I can't say. Alternatively, if you can't find a reasonably priced 24 volt panel get two of the small portable ones around 20W and wire them in series and put them on the dashboard or under a skylight wired into the vehicle system through a plug and socket of some sort.

 

[SandraL]

https://rover.ebay.com/rover/1/710-...0001&campid=5338547443&icep_item=164344524714


You can set the max output voltage and current . We used one to charge a 36v bike battery and it worked ok. Not sure about leaving connected full time ?

We set max current to 2 amps and voltage to 41v, charging nominal 36v lithium battery.
Initially the full 2amps was supplied but as it neared 41v the current dropped to near zero to maintain 41v. It is capable of 900w but does have a max current, from memory 15a on either input or output.

Cost the same again for a box and leads/plugs!

 

[Raul]

You could also use a Victron Orion 12/24 dc-dc converter and set it to whatever voltage you want to keep the starter at. Also you can fit a remote switch to turn it on and off when you want.

 

[tonyidle]

What vehicle is your A class based on? Sounds interesting.

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[tacr2man]

https://rover.ebay.com/rover/1/710-...0001&campid=5338547443&icep_item=231847312872
Cheaper if you buy direct (not ebay)

 

[autorouter]

I think you don't need a large current to simply keep the vehicle 24V battery topped up. When you stop, it will already be more or less fully charged from the drive. Sterling do a 'Battery Maintainer' which functions in a similar way to a BatteryMaster, but you can get all the combinations of 12/24V input/output. The one you would want is a 12 to 24V 1.5 amp battery maintainer.

Battery Maintainer

Instruction Manual PDF Product Information PDF Battery maintainer / charger includes 1m of cable.Save money on batteries and stop them from being destroyed by discharging. A flat battery means you need an expensive replacement.The auxiliary battery charger maintainer is simple to install and is...

sterling-power.com

 

[Malcolm Bolt]

What vehicle is your A class based on? Sounds interesting.

It's a 20 year old Mercedes 814.

 

[Malcolm Bolt]

Thanks to all for the information.
I will look at them in detail and examine costs before committing.
Cheers

 

[tonyidle]

Another option is to move over to 12v completely. A new high-output alternator, a starter motor (maybe - voltage isn't usually critical) and a few bulbs for a vehicle of that age. Bonus: more batteries in parallel for 12v.

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[tacr2man]

Another option is to move over to 12v completely. A new high-output alternator, a starter motor (maybe - voltage isn't usually critical) and a few bulbs for a vehicle of that age. Bonus: more batteries in parallel for 12v.

Wiper motor , heater blower , cold start system , instruments (voltage sensitive) relays solenoids. ?

 

[tonyidle]

Wiper motor , heater blower , cold start system , instruments (voltage sensitive) relays solenoids. ?

Agreed there's more to it than I mentioned. But it's future proof, simple, and probably similar in cost to the alternatives.

 

[poppycamper]

I have followed this post with interest because I feel there is a simple solution... but nobody else has mentioned it so I am beginning to feel I am being totally stupid and if so I hope someone will put me right and explain why.
As I understand it OP wants to keep his 24v system topped up with his 12v one.
But as he says 24v is made up by 2x12v batteries in parallel so my thinking is to treat these 2 batteries seperately and connect each one individually to his solar/liesure circuits.
One possible fault with this I can see is an imbalance between batteries.