Ebersapcher 24v

[jay]

For reasons that I 'd rather not go into - I have a D1L 24v unit that I want to reinstall on a yacht with a 12v system. I have 2 domestic and 1 engine battery - all 12v. There is a set of relays etc that alledgedly used to convert the 12v to 24v but its a bit of a mystery on how to connect it all up without frying myself, the boat or most importantly all my electronics.
Has anyone experience of using a 24v heater on a 12v system - or know of anywhere I can get any ideas?

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[Colin_S]

In a nutshell 2 12v batteries connected in parallel (like jump starting a car) will still give you 12v and 2 12v batteries in series (+ve on one connected to -ve on the next and the remaining 2 terminals feeding the load) will give you 24v.

Sounds like it should be fairly easily achievable with the correct switchgear but I am new to boating and have not got a clue what's available. On paper I figure you will need a maximum of 4 normally closed contacts and 3 normally open to make the changeover between 12 to 24 volts although it should be possible with 3 and 2 contacts assuming one negative stays grounded. Are the relays you have just loose relays that need wiring up or part of a pupose built bit of kit for the job?

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[jay]

The relays etc were designed by a previous owner and look like they would in theory stepup the 12v up to 24v. I am being told though that once the batteries are outputting 24v I'm likey to blow my alternator and the instruments etc that are connected to the same set of batteries. Some of old previous cabling has been disconnected and I can't figure out how it should go back togther!

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[Colin_S]

I expect it would be necessary to wire up the relays so that the batteries would be disconnected from everything else except the heater when running 24v.
From what I've read on this forum the -ve terminal is usually grounded to the boat (but stand to be corrected). With the batteries wired in series to create 24 volts the second battery -ve terminal would actually be at +12v potential compared to the first battery -ve so would definitely need to be disconnected from any grounding.

You could still run any 12v equipment from a single battery, my preference would be the first battery in the 'chain' as the -ve terminal could stay connected to any grounding.

What sort of current does the heater draw? Would it be easier to use an inverter to create 240v form your 12v batteries and than get some kind of off the shelf transformer to step this down to 24v. A bit messy but at least you can still run all your instruments and charge the batteries from the engine without having to turn off your heat.

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[Colin_S]

Or possibly even cheaper and easier - put you 24v one on ebay and buy one of the 12v ones on sale there?

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[jay]

Thanks colin I'm definetly erring to the ebay option but haven't given up yet! Thanks for your thoughts though.

The damn thing draws approx 20 amps by the way


Jay

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[TrueBlue]

Re: Eberspacher 24v

One of the problems with posting your problem on different forums is that which one should I reply to. I'm copying here a answer I made yesterday. I'm also adding today's info: which is that <A target="_blank" HREF=http://www.merlinequipment.com> Merlin Equipment </A> are doing 300W inverters at £43 (one required) and battery chargers at £70 (two required which might make option 4 affordable??

I think you're going to have insurmountable opportunities with this one...

Here are some suggestions - but which have difficulties in executing them:-

1. Switching batteries
Arrange a switching system to charge the 24V bank by connecting the two batteries in parallel for charging, and then in series when using the heater.

Downsides
1.1. The circuit is relatively simple, but as you need relatively beefy switches to carry the charging and glow plug current, you will have difficulty in obtaining a switch bank to do the job. Most commercial switches are simgle pole 'make' and switch bank systems (build your own stack) are only light current. Try Radiospares / CPC to see what's available.
1.2. Not withstanding the negatives in the above, you now have three battery banks in your system:
I. Engine start
II. Domestic battery
III. Heater battery bank
You will have to use a battery management system - and one of the top end variety to boot to do this.

Messy and expensive - forget it.

2. As you've sourced a S/h truck heater, what about getting a s/h 24V. alternator and attaching that to your engine.

Downsides
Extra belt(s) and pulleys required

positives
Simplest and possibly least expensive solution

3. 12V to 24V convertor.
I'm not aware of any available; there used to be motor generators which could do the job - some radio ham might have one - but they're going to be WWII vintage

4. inverter / battery charger (separate units, back to back)
Not quite such a potty idea as it may first appear, but wouldn't be cheap

KISS means Keep it Simple, Stupid. A reminder to us all not to let ideas run riot!

Perhaps others may run with the above suggestions - and improve on them.



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Stop what you're doing and wait my signal

 

[Colin_S]

Jay

Are you sure it draws 20 amps?

That would be 480 watts.

Don't know what size your batteries are but that would discharge a pair of fully charged 100 amp/hour batteries in five hours.

I've had a quick look at their web site and most current models draw somewhere around 40watts.

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[jay]

Re: Eberspacher 24v

True blue - can you explain in more detail (to a novice) how thw invertor/charger units would need to be hooked up?

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