WHAT DCDC CHARGER DO I NEED?

First up, why do you even need one? Can't you just charge a battery straight from the alternator? 

FACTS:

• Each battery chemistry requires specific charge profiles for correct and full charge

• Alternators do not provide any control over the rate of current flowing to the battery or the voltage it receives

• Most alternators operate under 14V, where as AGM and Lithium batteries need 14.4-14.7V for a full charge 

A DCDC charger is always the right way to go.

It will charge your battery correctly whilst also protecting your starter battery. It does this by taking power from your alternator or solar system (some both at the same time) and converting the current and voltage to the correct charge profile your battery requires.

Taking power from the alternator/solar when driving ensures that by the time you get to your camp spot, your batteries will be fully charged rather than waiting to setup camp then expecting your solar to start charging behind the 8 ball.

Generally speaking the alternator can provide a lot more charge power to your DCDC than most solar systems can (unless you have a very large setup on say the roof of your van or motorhome). Which one you go for depends on what chemistry of battery you are charging, what capacity it has and where you want to install it...and then your budget.

I want my DCDC charger in the engine bay

If you plan on installing your auxiliary battery in the engine bay, then you will almost certainly be restricted to a 100ah size battery due to space limitations for most battery trays in almost all vehicles.

Lead acid batteries should be charged at a current rate equal to 20-25% max of its rated capacity or 20-25A in this example using a 100ah battery.

A 25A DCDC charger is the maximum size recommended in engine bays for a single 100ah battery.

Similar for AllSpark 100ah LiFePO4 for in engine bay use, a 25A charger is recommended to keep battery temperatures as low as possible in an already high ambient temperature location.  

Whilst there are a number of options available on the market, many do not handle the heat of an engine bay well. As we only sell products we would use ourselves, the RedArc BCDC1225D is the only in-engine bay DCDC we recommend.

The REDARC BCDC1225D is an industry leading dual input DCDC charger.

FEATURES:

• Fully sealed, water and dust proof - designed for in engine bay use

• Green/solar priority - meaning it uses the solar input first and tops up to its maximum 25A output when the engine is running, therefore putting less demand on your alternator

• Can be powered from a 12v or 24v alternator to charge a 12v battery setup

• It has charge profiles for all lead acid batteries and also LiFePO4

• Can take up to 375w of actual solar input (up to about 460w of rated solar power) 

I am running up to 150ah of battery storage in my vehicle, caravan or camper

The RedArc BCDC1225D is an industry leading dual input DCDC charger. It is fully sealed and water and dust proof and designed for in engine bay use.

FEATURES:

• Fully sealed, water and dust proof - designed for in engine bay use

• Green/solar priority - meaning it uses the solar input first and tops up to its maximum 25A output when the engine is running, therefore putting less demand on your alternator

• Can be powered from a 12v or 24v alternator to charge a 12v battery setup

• It has charge profiles for all lead acid batteries and also LiFePO4

• Can take up to 375w of actual solar input (up to about 460w of rated solar power) 

Another option is the Enerdrive EN3DC40+ DCDC.

FEATURES:

• Fully programmable in amps and volts from 5A to 50A (allowing you to take advantage of the rapid charge function on the AllSpark Lithium Battery range)

• Adjustable voltage from 13.8V to 14.6V

• Takes up to 600W using up to 20Voc panels or up to 1000W using 45Voc panels

•  Built in LCD screen for programming. It also provide the user with data on the amps and volts coming in from solar or alternator and what it is sending to the batteries

The Enerdrive also offers charge profiles for all batteries (including lithium), so if you have AGM at the moment, but are thinking of switching to lithium in the future or adding another battery in parallel in the short term, then this would be your best option.

You can set it now for your existing battery size and chemistry and adjust later if you change batteries without having to change the charger. 

Finally there is the REDARC Manager 30, which is the only true 6 in 1 unit on the market.

FEATURES:

• Charge from alternator and/or solar (MPPT) with green power priority, meaning it prioritises solar input first, then AC mains, then alternator power

• Built in AC mains powered charger

• Load disconnect controller (separate SBI12-BLD or LLD unit required to disconnect loads - contact us for details)

• Built in dual battery isolator

• Charge profiles for all battery types including Lithium.

Bare in mind this can be paired with even a small size AGM or LiFePO4 battery but the charge current must be adjusted to 20-25% of the batteries capacity as a charge current - this can be changed in the Manager 30 advanced settings.

With a max 30A charge rate larger battery banks over 200ah in size will charge too slowly if you use large portions of that storage each day. A separate REDARC BCDC charger can be added in parallel with the Manager 30 if required to provide higher charge rates from alternator and solar whilst still maintaining the mains charger, battery monitor and load disconnect functions from the Manager 30.

On the Offroad Living truck, we run a REDARC Manager 30 with RedVision TVMS and a separate BCDC 1250D in parallel to give up to 80 Amps of charge current into 450Ah of LiFePO4 batteries. Contact us for more info if you would like to know how this can be done.

I am running more than 200ah of battery storage in my vehicle or caravan

Larger battery banks can start to become a little more complicated both in how to correctly install them (potentially wired up using a busbar arrangement) and also in getting the charging needs right.

It's all well and good to install a very large battery bank to give you more days of run time, but if you can never charge it back to 100%, then all you have really achieved is adding an extra day or two of running before you hit the same problem with insufficient charging ability.

Whilst we recommend having a minimum of 2 days power consumption in storage in your batteries, you need to be able to re-charge it too if you end up using that power. Of course if you have access to mains power on a regular basis (generators or caravan parks), then you will be able to re-charge without concern with even a 30A charger overnight, but if you want to be offgrid for extended periods, then your solar and alternator will be doing the bulk of the work.

The choices for smaller battery banks in the options listed above still apply - REDARC BCDC1225D or 1240D, Manager 30, but if you are running a larger batteries or banks over 200ah, then a 50A DCDC or larger maybe prudent.

If you have 2 x 100ah LiFePO4 batteries or 2 x 120ah AGM or larger in parallel then you can go with a 50A DCDC charger. You can select from a REDARC BCDC1250D or Enerdrive EN3DC40+.

It is important to note thought that if your solar input is above 32Voc and below 45Voc then you must go for the Enerdrive option which can handle higher voltage panels. If under 32Voc then both the REDARC 1250D or Enedrive EN3DC40+ are both suitable. Both have profiles for all Lead acid options and LiFePO4 batteries.

For even larger banks of 300ah+, then a second DCDC in parallel maybe required. A REDARC Manager 30 with an extra BCDC in parallel can also work well.

On the Offroad Living truck, we run a REDARC Manager 30 with Redvision TVMS and a separate BCDC 1250D in parallel to give up to 80 Amps of charge current into 450Ah of LiFePO4 batteries. Contact us for more info if you would like to know how this can be done.

NB. Upgraded alternators with higher output current may also need to be considered if going down this path for very heavy power consumers.

No two set ups are the same, but the information here can be used as a guide to get you started. There is nothing like real world use to discover what you do and don't need in a set up, so before heading off on any larger trips away from power, we recommend having a test run or two closer to home.

You can always add to a set up, but making sure you have the right components to begin with ensures you will only be adding, not replacing (which can be costly).

Check out our other articles for information on choosing batteries or solar for your needs or if you need further help, please don't hesitate to contact us by phone or email.