Anyone using CTEK D250SA?

KathyC · Jan 23, 2018

I'm in the planning stages for a van build and came across the CTEK D250SA. As I understand it, it's a 20A DC to DC battery charger that can accept input from alternators, solar panels or wind power. It uses MPPT to charge. This seems like an ideal system for smaller installations (manual recommends battery capacity of 40-300ah and solar panel from 50-300 watts - max of 23 volts).

Anyone have any insight or experience?

Here is a link to the product if anyone is curious:

https://www.ctek.com/products/vehicle/d250sa

D250SA

D250SA

John61CT · Jan 23, 2018

Why do you think you need a DC-DC charger rather than a simpler cheaper and higher capacity VSR/ACR?

What batt models is it connecting?

I've installed a few of the previous D250s version, with and without SmartPass add-on.

The manual is online, read that and ask Qs to clarify.

Limited amps, so your alt is ideally wired to the house bank, use the DC charger for Starter.

John61CT · Jan 23, 2018

I've never used the SC part of it, but many report it's not nearly as capable as a standalone, so don't give that aspect much weight.

Fine to keep a Starter topped up when vehicle stored outdoors though if that's all you need.

KathyC · Jan 23, 2018

Thanks for the feedback. I think I should probably do more research and possibly with the 4x4 crowd who seem to use these systems more for "overlanding" rather than full-time van/rv dwelling. Appreciate your insight.

John61CT · Jan 23, 2018

The functionality of these devices is in connecting the House bank circuit to the vehicle charging & Starter batt.

Your various other charge sources, their amps output, the distances and wire gauges involved and the chemistry type of your batteries, all play a role in choosing the optimal type of device.

Ticklebellly · Jan 23, 2018

Great bit of kit. Have one in a caravan and one in a VW camper. 300 Watt panel and Alt to 130 AH battery. About four years so far and never a problem. Simple to hook up and works for me.

Artsyguy · Jan 23, 2018

Thanks for asking this question as I've been considering the CTEK also. I won't be using solar, just my alternator to charge batteries. My understanding is when starting your vehicle the CTEK, it will not allow ANY current to the house battery UNTIL the starter battery is charging and stable. Once that happens, the CTEK kicks on and starts charging your house battery. If using an ordinary solenoid between the starter and house, it won't allow the starter battery to fully charge before drawing current from the alternator to start charging the house battery. Bottom line...this makes your alternator work less and last longer. At least that is what I THINK the difference is. If anyone KNOWS different, then please correct me.

John61CT · Jan 23, 2018

I'm not now debating whether or not it does that (it doesn't), but the issue you describe is not actually a "problem" that needs solving.

However a lot of expensive gadgets have been marketed on that basis, by companies whose other products are excellent.

DC-DC chargers are needed when the two banks have very different chemistries, and can't tolerate sharing the same charging voltages.

Or when properly large gauge wires to handle large amps over long distances are just impractical to install.

Not to be confused with the sinking feeling when a noob finds out what such a wiring job costs just in materials.

I cannot think of a third use case, 99% of the time a combiner/VSR/ACR plus robust gauge wiring, and/or changing Starter chemistry, is the better solution.

John61CT · Jan 23, 2018

Third scenario, and it is important.

New vehicle, under warranty, Euro style super energy recovery, only runs the alt while braking etc nightmare "features".

But alt staying on Starter means a higher-amp DC-DC unit is needed.

Sterling Power's BB series (batt to batt) highly recommended. Not cheap!

But fully adjustable, so 4th scenario:

proper care of LFP banks from any old-school primary charge source.

Ticklebellly · Jan 23, 2018

Artsyguy said:
My understanding is when starting your vehicle the CTEK, it will not allow ANY current to the house battery UNTIL the starter battery is charging and stable.

I see charging current to my house battery as soon as the alternator energises the Positive rail out of the alternator, that is, as soon as the alternator is turning at above its minimum rev requirement. Positive output from the alternator goes direct to the input of the D250 so I don't see any way it could every incorporate any decision making in regards to checking if the starter battery is charging and stable.

Starting most engines only draws a tiny bit of energy from a starter battery. Might be high amps but it is only for a couple of seconds. In older technology cars without smarts in the alternator, the energy drawn is replaced in a very short time. In my VW camper, the starter is only charged after the start battery falls to a set SOC. The smarts in the engine management system even disconnects charging should I give a large push on the Loud Pedal so that the full engine power is available to drive the wheels in that situation.

I like the D250 so much, I am currently experimenting with it to charge a 40Ah LiFePo battery I put together from prismatic cells.

John61CT · Jan 23, 2018

If that's a cheap science project, no worries

But otherwise best to use a Sterling for that, need to keep max charging voltage below 13.9 (3.45Vpc) for good longevity.

If you want to get into details on this, start a new thread so we don't derail this one.

Artsyguy · Jan 23, 2018

I have no idea about what you guys are even talking about. Let's cut to the chase and someone tell me why buying the CTEK would be a better choice than a simple solenoid for charging my house battery from my starter battery when driving?

John61CT · Jan 23, 2018

Probably you don't need to spend the extra money. IOW a solenoid will likely be fine.

A more precise definite answer requires more information, as discussed in the earlier posts above. For example what amps/volts your alt puts out, what model House bank and so on.

Anything you think relevant to you that you don't understand, google a bit, still don't, then feel free to ask detailed questions.

Stuff you think not relevant, just ignore

KathyC · Jan 23, 2018

John61CT said:
A more precise definite answer requires more information, as discussed in the earlier posts above. For example what amps/volts your alt puts out, what model House bank and so on.

Thanks, John. At this point, I haven't built anything - just wanted to hear of any first hand experience (yay/nay) with the CTEK system. In my current rig, I have a Blue Sea ACR supplemented with portable solar and it's been perfect for our needs (which are, admittedly, minimal).

Ticklebellly · Jan 24, 2018

Artsyguy said:
Let's cut to the chase and someone tell me why buying the CTEK would be a better choice than a simple solenoid for charging my house battery from my starter battery when driving?

I hate telling others what is best for them. I decided against the use of the alternator to charge the house battery because the time required is often longer than the trip before me. The D250 is best for me after testing the simple connection method, in my previous vehicle. I found that a 50% SOC battery would draw up to an initial 25 Amps supplied by the alternator for a relatively short period of time until battery plate surface charge built up. Within 15 minutes, the charge current would drop to less than 4 Amps and within 30 minutes the charge rate would be less than 2.5 amps. A battery's terminal voltage rises quite quickly when it is on charge and charge current is nearly totally proportional to the difference in voltage between charging source and instantaneous terminal voltage of the battery. Voltage drop across the cable connecting alternator to the battery can, possibly, be something to be considered. Standard voltage output of the alternator I did this testing on was 14.42. Essentially, using the alternator as the charging source required a long time to fully recharge my house battery. Establishing a charge current profile is pretty easy and might help any decisions you might make.

The situation in my VW with some smarts in the alternator makes it even worse. Initial volts are typically 14.5 and that drops off to 13.8 in a short time.

In contrast to the simple alternator to battery, the Alternator output to the D250 sets up the situation where charge current is 20 Amps until the battery is charged. In my situation and set up, I pull about 13 Ah overnight. Assuming a full charge come nightfall, an hour, or less, of driving next morning results in a topped up battery. I often confirm the SOC by resting the 130 AH battery while using the LiFePo test bed so I am quite confident that the house battery is fully charged after an hour or so of driving.

A personal foible is that I shun solenoids and prefer a high amp capable switch for the manual control and cost.

Your Q specified alternator charging. For me, another advantage or option available when using a D250 is easy connection of a solar panel as a charge source. I connect a solar panel to the D250 using a XT60 connector and often put the camper in the shade and run a flying lead to the panel in the sun.

A D250 does cost a lot more than a solenoid or a high amp capable switch. If really short of money, you can even connect the positive terminal of the started battery to the house battery with a nut and bolt.

Safety note - batteries can deliver seriously high currents and sparks can ignite charging gases, pls be careful.

John61CT · Jan 24, 2018

Ticklebellly said:
Within 15 minutes, the charge current would drop to less than 4 Amps and within 30 minutes the charge rate would be less than 2.5 amps.
…
using the alternator as the charging source required a long time to fully recharge my house battery.

Excellent points!

In fact the only time an alternator can be used to *fully* recharge a depleted deep-cycle lead chemistry bank

fully, as in 100%, using the mfg spec for trailing amps (which needs doing at least 2-3 times a week, ideally most cycles)

is for people driving all day long.

Same with a genny, impractical for the required minimum 5+ hours.

Fossil fuels are usually practical only up to 80-85% point, depending on chemistry acceptance rate, maybe just the first hour.

Solar is required for the low amps long tail, the last few % SoC can take many hours. That's why best case is fossil fuel high-amp charging early in the morning, then just a little solar is enough, long as it has the whole solar day to finish.

All these issues completely go away with LFP, an hour a day is plenty with a high-amp charge source, no solar needed at all.

Ticklebellly said:
The situation in my VW with some smarts in the alternator makes it even worse. Initial volts are typically 14.5 and that drops off to 13.8 in a short time.

Yes, such issues are getting more common even in the US.

That's where a DC-DC charger becomes necessary if your alt is going to be a significant energy source for your setup.

gapper2 · Jan 24, 2018

KathyC said:
I'm in the planning stages for a van build and came across the CTEK D250SA. As I understand it, it's a 20A DC to DC battery charger.

I'm a super newby at this stuff and wanted to add my 2 cents. I am also in the planning stages but it's been almost 2 years now. Don't really much about the CTEK but I had already purchased a 795 Watt solar kit which I have yet to install. I'm the first to say that I have no real practical experience and I originally planned to set up my alternate charging source with only a solenoid system. But I monitored my alternator voltage output for well over a year and the voltage regulator and computer control of that regulator left me disappointed with the planned solenoid system. Voltage was determined by some mystical algorithem So I looked into battery to battery chargers. Corresponded with Sterling Power because I have a previous unit from them. Being a Newbie one of the first mistakes I made was a purchase of the wrong house batteries. I purchase 2 Odyssey PC2150 batteries on sale. Don't get me wrong they are excellent batteries!!! The problem is they want a minumum of 80 amps for a 200AH set of batteries.

So the puzzle was how to keep these happy. (Mind you this is when I had more dollars than sense )

I finally decided on the Sterling BB1260 because I got it at a 40% discount. I liked the sales pitch because it is a 4 stage charger for many battery profiles but the thing I liked the most is an option for a programmable profile for up to 60 amps. Hey that's perfect for a possible lithium house battery upgrade and or a second set of house banks. This is not a commercial just another newbie giving what I've learned.

I plan to approach this trying to emulate Sternwake as much as possible. Show me the facts!! When it warms up I'll follow up with reports. Right now it's just sitting on the desk.

D250SA

D250SA

WalkaboutTed · Jan 24, 2018

I have had the CTEK D250s and the SmartPass for over a year in my van. The best thing about it is that it's idiot proof and that all I had to do is run the cable from the front and hook it up. I have the SmartPass because I have 300ah of AGM battery that requires more power through than the 20amps that the D250S allows.

If you're not planning to use solar or wind power along with alternator charging, there's absolutely no reason to get the CTEK units. I bought it as I was going to use a portable panel and run it through the CTEK's charge controller.

Well, my plans morphed into 445 Watts of solar that go through another charge controller. But if I need to use my portable, I have a plug that hooks into my CTEK. The beauty of the CTEK units is the "set it and forget it" quality. If you're not into micromanaging your system, then the non-adjustable defaults are great.

Would I buy it again? For me, maybe not, as I've turned into a neurotic charge controller tinkerer fon both my van and travel trailer. But my husband is doing a conversion on his van and he bought the D250S and the SmartPass for his 450ah of battery. He's not interested in fine-tuning anything and just wants things to work the way they should. And the CTEK units do that well.
Ted

KathyC · Jan 25, 2018

WalkaboutTed said:
I have had the CTEK D250s and the SmartPass for over a year in my van. The best thing about it is that it's idiot proof and that all I had to do is run the cable from the front and hook it up...

This is really, really helpful. Thanks for the first-hand experience and pros and cons.

Artsyguy · Jan 27, 2018

Here is the sales pitch directly from the Amazon website:
"The CTEK D250S Dual is a 5-step charger that automatically adjusts the charging voltage and current according to the battery state of charge and temperature – reducing a battery’s charge time. This charger obtains its energy from DC sources such as alternators, solar panels or wind power and optimizes this power to meet the charging requirements of different battery banks. It automatically selects the best connected DC energy source (of 2) for the purpose and switches between these energy sources to achieve high efficiency multi-stage charging.

A sensor on the charger senses the battery temperature and adjusts the required charge by increasing the voltage in cold weather ensuring the battery is fully charged, and dropping the voltage in hot weather to avoid the problems of overcharging.

This charger has the additional benefit of an auxiliary input which can be connected directly to solar panels without the need for a regulator, offering free power from the sun and a built-in Maximum Power Point Tracker (MPPT) that helps the solar cells produce power as efficiently as possible by taking the most efficient source of energy from the solar panels automatically, and then using the power to charge the battery. The MPPT searches for the most effective combination of solar cell voltage and current, which ensures that the solar and alternator function in unison to maximize power output. This charger is perfect for boats with one battery, boats with start & service battery, boats with start & service bank, campervans, caravans, RV’s and trucks."

Now despite what I've said in previous posts, now I know why I want one of these: It should allow optimum charge cycle into house battery depending on house battery condition and temp. Not sure if there are other products that do this (again, I'm not using solar) but it sounds good to me on paper. Hope this helps...

Anyone using CTEK D250SA?

Help Support Van Living Forum:

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Similar threads

Join the conversation!

Join today and get all the highlights of this community direct to your inbox. It's FREE!