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Baintech 75Amp Slim Battery with Built-in DC-DC Charger


Baintech 12V 75Ah Slimline Lithium Battery with in-built 20A DC-DC will save you on weight and space! The slimline design allows you to fit a lithium battery into tight spaces, like under false floors and behind seats. At just 50mm thick, it’s the slimmest 75Ah battery on the market.

5Ah Slimline Lithium Battery with in-built 20A DC-DC  is constructed using the latest lithium iron phosphate cells. These prismatic cells are of the highest quality in a metal hard case. The battery has an inbuilt Battery Management System (BMS).

At just 12kg, the unique slimline shape makes it the perfect battery for installations where space is a premium. Slide it behind a seat, bolt it to a wall or at the back of a cupboard.

The 75Ah Slimline Lithium Battery with in-built 20A DC-DC provides up to 100A of continuous discharge or charge and can be stacked in parallel to increase amp hour storage capacity. Charge and discharge are via the two grey Anderson plugs. Note, an external fuse must be used. The strong aluminium outer enclosure delivers a safe, lightweight, and powerful unit which is the perfect building block for next-generation battery systems.

75Ah Slimline Lithium Battery with in-built 20A DC-DC Features:

  • Internal 100A BMS
  • Strong aluminium enclosure
  • Lightweight
  • Slimline shape and size
  • Parallel connect capable
  • Designed and fully assembled in Australia

75Ah Slimline Lithium Battery with in-built 20A DC-DC Specifications:

  • Model BTLITH1275-SL-DCS
  • Capacity 75Ah
  • Nominal Voltage 12.8V
  • Charge Voltage 14.6V max
  • Charge Current 100A
  • Discharge Current 100A max cont.
  • 200A surge
  • Operating Temp 0-45oC
  • Weight 12kg
  • Life at 80% DoD 2,000 cycles
  • Life at 50% DoD 5,000 cycles
  • Size (L x D x H) 635 x 265 x 50mm




Why our lithium batteries are superior to others in the market:

  • Massive 5 Year Warranty
  • Designed and assembled in Australia
  • Custom designed BMS System by engineers in Brisbane
  • The slimmest designs on the market; 75Ah and 110Ah Slim just 50mm thick
  • In-built DC-DC Charger capability available – unlike any lithium on the market
  • Constructed using the latest lithium iron phosphate cells
  • Local after-sales support

Why Lithium?

Lithium batteries provide more usable capacity than lead acid batteries. Deep discharging does not affect the life of a lithium battery the way it does with lead acid batteries. You can use the battery longer before needing to recharge, without damage to the battery.

Cost Effective Over Life Cycle

When considering the usable capacity and lifespan of lithium batteries, they work out cheaper than lead acid. When you add the cost and inconvenience of refitting new lead-based batteries every few years the total cost of ownership over the long term is far better with lithium batteries.

Longer life

Lithium batteries are rated for 2,000 – 5,000 cycles and much more if used carefully, giving you several times the life expectancy of standard lead acid batteries.


Lithium batteries allow you to pull far more amps out of the same size battery systems.


Lithium batteries are less than half the weight of the equivalent lead acid battery. Lithium batteries can be up to a third of the weight of the equivalent lead acid AGM battery. This is an important consideration for anybody who is mobile.

A 100Ah AGM deep cycle battery can be up to 38kg in weight, whereas the same size lithium battery can be less than 12kg in weight!

That means you can at least double or even triple the stored battery capacity on a RV, or alternatively use the reduction in battery weight to bring more water, or food or luggage on your trip.

Reducing weight in a RV helps to keep you under the tare weight, reduces aerodynamic drag which improves fuel efficiency while on the road.

Fast recharge

Lithium batteries charge more efficiently, and don’t require as many stages during charging. Therefore, they will charge faster, and hold more of the energy from solar panels and other charging device.

Are all lithium batteries the same?

No. There are several types of lithium-ion chemistry on the market, including lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese cobalt oxide and lithium iron phosphate.
The cells come in different packages including cylindrical prismatic and soft pouch.

Cylindrical look like bigger AA batteries while prismatic cells are rectangular about the size of a small book. Pouch is a soft jelly-like material which needs outer casings. Lithium iron phosphate is the safest chemistry and prismatic cells are the most efficient and mechanically robust way to package the stored energy.

Beware of lithium batteries using the small cylindrical cells soldered together in plastic boxes using a cheap low quality BMS. Cylindrical cells need sometimes up to 100 spot welds to join them together whilst prismatic cells have solid metal posts that withstand vibration and are suited to be used in tough environments.

Install FAQs

Do I run a cable from the start battery to Blue Anderson on the unit?

Yes, the only thing you need to do is put a 30 amp inline fuse at the Start battery end of the joining cables.

What size cable do I need to use?

MOST IMPORTANTLY the cable Has to be 12 AUTOMOTIVE GRADE CABLE and NOT Single Core 240 V Household type of Wire.

The cable size required, depends on the Length of the Cable and the Loads it needs to carry, so the answer is the cable size you use needs to be able to carry the total amps you want to flow.

For example, a load of 50 amps over 2 meters would require a cable size of around 4 AWG the same load over a distance of 5 meters would need a cable size 2 AWG.

Do I need an isolator on the start battery or just a fuse since this has an inbuilt DC-DC Charger?

No, you don’t need an isolator as the battery has a Voltage Control Relay ( Isolator ) Built-in that Engages at 13.2 V and Disengages at 12.7 volts so as not to draw power from the starting battery when the engine is not running.

How can I put a solar input into this unit? Do I need an MPPT?

Yes, you need some source of regulated solar either a PWM or MPPT or in some cases portable blankets and foldable panels have a regulator already built-in so you can connect directly to the Grey Anderson Plug. All Baintech Solar Blankets come with a PWM.

Do I use the Grey Anderson plug and have a split between outputs/loads and solar input?

The Grey Anderson plug in the Battery is connected directly to the internal battery cells, This means you can put power in and take power out of this connection exactly the same way as Pos and Neg terminals work on a conventional battery.

The easiest way to do this is to use an Anderson Parallel/splitter cable such as our BTA2AP0.5 which turns the single connector into TWO so you can run 1 as input and 1 as output. The other way is to run the grey Anderson to a distribution panel and connect you solar and devises to the panel.

How do I mount the battery?

The Batteries come with 1 set of Brackets included. if you require extra brackets they can be purchased separately.

The Slimline battery voltages below are a useful guide:

  1. A normal full battery open circuit voltage (Voc) with no load rests at 13.3V to 13.6V;
  2. Depending on the load voltage may dip 0.5V below the Voc;
  3. Below 13V Voc the battery is low, and should be charged to promote a long lifespan.
  4. Below 12V Voc the battery is close to empty, and should be charged straight away;
  5. Low Voltage Disconnect (LVD) is set at ~10.5V.

If the battery is unintentionally discharged flat, then it can be recovered?

First remove all loads sources and switch off the LED voltmeter. Apply a ‘dumb’ charger which charges the battery without needing to ‘see’ the battery first.

How do I look after my battery for a long battery life?

Keep it charged at above 13V at all times. Check the battery once a month.

How to care for my Lithium in storage?

All batteries, whether they are lead acid or lithium degrade faster in extreme cold and extreme hot environments. a. Do not charge battery when the ambient temperature is less than zero or above 45o C. b. Do not operate the battery in environments are -20o C or above 60o C. Doing so would reduce its life expectancy.

Will the battery be damaged if allowed to fully discharge?

Firstly, the BMS has a low voltage disconnect at around 10.5V, so the battery will never discharge to zero volts. If the battery is flattened and cuts out at LVD at 10.5V then it can be recovered without damage if on occasion. If it is done repeatedly then it will have a negative impact on longevity. Maintaining the battery charge at 13V or higher will maintain good battery life. Look after your lithium battery and it will give you many years of service.

What does my BMS do?

Your battery comes with a Battery Management System (BMS) mounted internally.

The BMS is an electronic solid-state circuit board which manages the cells and protects the battery across a range of scenarios which primarily includes over charge and over discharge protection. Unlike lead acid batteries, over charging or over discharging a lithium battery may lead to a hazardous scenario. Therefore, the BMS is the heart and soul of a lithium battery.

The Slimline battery BMS is a highly reliable solid-state device which is primarily designed to keep the cells safe and the overall pack from being damaged by excessive voltage or excessive discharge event.

How can I install my battery?

Mounting orientation: The Slimline battery can be mounted flat or on its side in any orientation, except upside down with the Anderson plugs at the top – in this configuration the internal cells are upside down which is against the manufacturer’s recommendations. This is the only orientation that is not allowed.

Longevity & Depth of Discharge

One of the advantages of lithium batteries over lead-acid batteries is longevity. If you want to realise the long life potential out of your lithium battery then consideration must be given to depth of discharge. A battery lifespan is rated by the number of cycles before the original capacity has reduced by a certain amount; a cycle is defined as discharging from fully charged, to a percentage Depth of Discharge (DOD), and then charging back to full again. So, DOD describes what percentage of the battery capacity is being used each time. Note: DOD is different to State of Charge (SOC, also known as Charge Level); in fact, they add together to 100%. So, 80% DOD equates to 20% SOC. The less DOD you use each cycle, the longer the battery will last. This fact should be considered when choosing the battery Amp hour capacity. You will have a higher return on battery investment if there is enough capacity at hand such that you are not heavily discharging the battery on every cycle. Extra capacity ensures lower DOD, extended life and a higher financial return on your investment. BAINTECH batteries have a cycle life of 5,000 at 50% and 2,000 at 80% DOD.

Temperature range

The maximum window of acceptable operation is 0-45o C. If you regularly operate outside of this suggested range, you should consider changing the battery location or actively cool or heat the environment in order to preserve battery life. If the ambient temperature that the battery operates in is greater than 60o C you should cease use immediately.

Does the battery capacity degrade over time?

Yes, all batteries degrade slowly over time, even with no load sources connected. Storage temperature is important to degradation. Roughly every 10o C above ambient 20o C doubles the degradation rate. Cool ambient conditions are better as it slows down degradation rate.

Australian Owned and Operated

With more than 30-years of experience in DC and AC Power Product Solutions, Bainbridge Technologies are the leaders in innovative 12V power solutions for leisure auto markets (4WDs, camper trailers, caravans/recreational vehicles, and boats).

As an Australian owned and operated company, Bainbridge Technologies are passionate about the great outdoors and creating more good times for Australians.

Expert Advice

Speak to the team today about your power needs.

  • Lithium Batteries
  • Off-Grid Solutions
  • Caravan Systems
  • Marine Solutions
  • Automotive and 4WD Installation Advice
  • Inverters
  • 12 Volt Accessories
  • Battery Chargers
  • Solar Blankets
  • Portable Power Solutions

Baintech has the largest range of lithium batteries available for 4WD, Caravan, and Marine use. Weight dispersion seems to be a common factor across all leisure industries. Baintech Lithium batteries are a great choice when you are concerned about excess weight in your boat, caravan, or 4WD.


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