Cetek d250s dc dc charger.

bobhod · Member

Cetek d250s dc dc charger.

Barboots · Senior Member

Are you certain Bob? That seems an extremely high cut-off for commencement of charging. Anyway... depending on the panel specs, an extremely cheap "make do" solution would be to connect the solar panel to the battery directly, and disconnect it before the battery voltage reaches its maximum allowable voltage. The battery will pull the panel output down. More practically, a different solar charge controller that doesn't have the same limitations could be purchased... however I honestly think there's a misunderstanding at hand.

Tony Bev · Guru

I am not an Automotive Electrician, Bobhod

You may have a faulty item, or it may not be wired correctly

I have a Cetek D250S dc to dc charger

I have a motorhome where the chassis is hollow and galvanised (or perhaps silver phos paint)
As I was not sure if I could make a permanent good earth, I used the battery earths, as per the picture below

Using an el cheapo multi/clamp meter, I can confirm that my DC/DC charger works as manufactures description
I have had it perhaps nearly two years, and purchased it because I thought, it is a fit and forget item

1. The solar and/or engine battery, charges the leisure batteries, through the DC/DC charger
2. With the engine not running, after the leisure battery is fully charged, the DC/DC charger, allows the solar side to charge the engine battery
3. At night time with no sun, and no engine running, the DC/DC charger isolates the engine and leisure batteries

I found that using 6mm square cables, I did not have enough threaded length, of the Allen head bolt, to put all three earth wires onto the DC/DC earth terminal, so I made a bus bar by flattening a larger connection and drilling a hole in it

If the DC/DC charger is working correctly, and/or the wiring is correct, you will not require anything else to charge your leisure battery/s

I have one 300 watt solar panel, and two 120 amp house batteries

Hope that this info is useful to you

D250S Dual DC charger.png

Izabarack · Guru

bobhod wrote:
...... it was because the caravan battery was below 13.3 volts which to me is near fully charged.

Statement does not make sense to me. I have three D250s and reckon they are a great bit of kit. Maybe someone who knows somthing about setting up a Solar to 250S to battery System Needs to have a look.

Iza

Warren-Pat_01 · Guru

Hi bohod,
I agree with Tony - something has failed or there's a wiring error.

I don't suppose you have a separate regulator stuck in there somewhere? Two in series will block the charge.
13.2-13.5v is the float voltage of a modern Gel/ATM battery. There is a good post called "Doing the Maths" just a little way down the Techies posts that gives the voltages you should expect.

I have a D250 DC-DC charger under the bonnet of my car - replacing the simple relay that overcharged the auxiliary battery in high temperatures, risking an explosion. It has definitely improved the life of that battery & given me peace of mind.

Check your wiring, if necessary rewire to Tony's diagram & if you still cannot get it to work, ask an auto-electrician to check it out.

All the best,
Warren

wasn_me · Guru

I have a 250s dual in my tug to charge the fridge battery. It is connected to the alternator & a 90 watt solar panel. I also have one in the van. It is only connected to a 120 watt panel. Both work fine. They bulk charge above 14 volts. They float charge around 13.3 volts. After a period of float charge they disconnect the charge, & battery voltage drops back to around 12.9 volts. This only happens if no load. As soon as any load is applied the charge reconnects. Try applying a load & see what happens maybe your battery is fully charged. I am very rarely connected to 240 volts. My batteries are always charged.

bobhod · Member

Thanks Tony I fully agree with you. cetek equipment is excellent but I believe that with the d250s they have got it a little wrong on the solar charging by not letting the solar panel charge if the battery is below 13.3 volts as this is when you need the solar panels charging. The cetek works like a normal twin battery isolator in as much as it is basically an open circuit until the starter battery reaches 13.3 volts and then it closes the circuit and lets the alternator charge the caravan battery charge, this is to prevent the starter battery going flat. But in doing this they have also created an open circuit in the solar charger section which prevents the solar panel charging the caravan battery until the battery is at 13.3 volts.

my wife ang I like to watch a bit of TVs at night and with the fridge running the batteries would generally be ar about 12.5 volts in the morning so the solar panels are prevented from charging the batteries which means that you either have to run your engine or use a generator to get your caravan battery up to 13.3 volts ln order for the solar panels to start charging.

The only way to fix the problem is to disconnect the solar panels from the cetek and cooect them via a seperate solar regulator direct to the battery.

best regards

bob Hodkinson

wasn_me · Guru

Bob, you are describing the same setup that I have in my tug. After stopping the engine, the ctek will disconnect the start battery the first time the fridge runs. I could sit for 3-4 days with out starting the engine. The solar panel keeps the fridge battery charged. If the fridge battery gets fully charged, the ctek will reconnect to the start battery & divert any solar charge to the start battery.

Tony Bev · Guru

Bob, sometimes when I travel, I am up before the dawn

I have seen my leisure batteries as low as 12.7 volts

As soon as the dawn comes, the solar panel starts charging the battery, through the Cetek D250S DC/DC Charger

The only leisure battery charger I use, is the same make and model, as the one in the picture

bobhod · Member

Thanks Tony that seems really positive and is just what I want. I have my d250s mounted in the caravan next to the caravan battery and everything is wired up as per your diagram. The only thing is that the car is parked away from the caravan so the 12v from the car is not connected to the caravan. But I believe that the solar system should still work like you said. At the moment I have fully charged the caravan battery with a seperate charger and rhen turned off the charger and turned on the frig. I note that the solar panel will not connect and start charging because the battery is fully charged but I will keep watching it all gay and see what happens. I will keep it running until the battery goes flat and let you know what happens

Bob

Tony Bev · Guru

Do not let your battery go flat, Bob

When you have dropped down to 12.4 volts, you would have taken plenty out of it

You are correct that in a normal situation, the solar side will work with no engine battery connected
I always isolate my engine battery, when doing maintenance on the engine, and the DC/DC charger still works

Below is a bit of a pic, on how I check mine with a cheap multimeter

If you do not have numbers within this ball park, you may have to get an auto sparky to look at it

Or perhaps a techi will come along and explain it better than me, as I am not an Auto Electrician

Check if DC charger is working.png

Bluey1 · Veteran Member

Also make sure polarity across solar input and negative correct from panels

Izabarack · Guru

bobhod wrote:
I believe that with the d250s they have got it a little wrong on the solar charging by not letting the solar panel charge if the battery is below 13.3 volts

Just this morning, I connected a 250S to a battery reading 11.9 volts. 300 watts of solar panel feeding in to the 250S has popped the battery up to over 13 volts already. This is completely at odds with the assertion that no charging happens until the battery to be charged is at or over 13.3 volts. A rested battery reading 13.3 volts, open circuit, does not need charging.

Iza