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Offroad Caravan | Smart Battery System

Discover the smart battery system used in the Kimberley Karavans offroad caravan

offroad caravans solar and lithium batteriesWhen deciding on what size batteries you'll need in your lightweight off-road caravan it is important to make sure that you don't add too much extra weight. With lithium batteries and super thin solar panels you can have large capacity with minimal weight. 

 

Even if you have a suitable generator, you will need to decide on the size of batteries. This article doesn’t cover how to size them, we have an eBook for that (see link at end of blog). It covers the weight and bulk of the batteries that impact on traveling light yet having enough power for camping for periods without a generator.

One of the critical battery power consumers in an off-road caravan is the refrigeration.LPG-fuelled refrigerators use very little battery power but they have a major problem. They take a long time to get very cold in the warm weather and take some time after traveling to settle down. Even the compressor refrigerators we use at Kimberley have modifications so that you can make ice in Darwin.

The big issue with LPG refrigerators is that they are very poor in space efficiency. They are bulky and have a short shelf size internally in most models even though the capacity looks sufficient. By adopting 12V refrigeration , you will get these benefits:

  • make ice in Darwin (assuming it has a freezer)
  • Lower and more efficient profile
  • performs well while traveling can get very cold
  • very fast deeper shelf space throughout
  • Safer: no LPG inside Lower cost to operate if using solar

The disadvantage of 12V refrigeration is that good battery capacity is required.

In addition to suitable battery capacity, you will also need:

  • Good 3-way Charging System
  • Suitable 240V Battery Charger
  • Suitable solar controller
  • Solar Panels
  • Power capacity meter (showing capacity left in batteries)

This all costs more money to do properly and is the main reason the majority of caravan manufacturers don’t offer compressor refrigeration.

Looking at weight, space and performance efficiency, compressor refrigeration is a long way ahead. However to be fair, you have to add into the weight calculation, solar panels, larger batteries and battery chargers. Are you therefore overall better off?

The common answer is that you are far more independent and capable of staying longer in a wider variety of places if you have good battery capacity and solar charging.

12V power is necessary for lighting, water pumps, LCD screens and other 12V devices if everything else is gas. So if you want this independence, then you will need larger batteries and solar anyway!

AGM Battery Capacity 
(Lead acid in an “Absorbed Glass Mat”) 
100 Ahrs   200 Ahrs  400 Ahrs    800 Ahrs 
Usable Capacity
(50% discharge)
50 Ahrs  100 Ahrs  200 Ahrs   400 Ahrs 
No. of Days Capacity
(
with Typical Off Road Daily Use* of 80 Ahrs/day and no solar)
less than 1 1 Maybe 2-3   Maybe 5
Weight of Batteries 36kg  75kg 150kg 300kg 

You can add solar to charge the batteries. The larger the battery capacity, a larger the solar bank is required to optimize the investment.

Traditional glass-based solar panels are heavy, and the roof is not the best spot for weight! So there are Traps here.

Glass Monocrystalline
Solar Panels

100 Watts  200 Watts  400 Watts  600 Watts

 Usable Efficiency on Roof-Mount
(Flat and can’t be angled as sun moves)

 50W  100W  200W  300W

 Typical Power Output
(usable efficiency with standard solar controller) 

less than 3 amps
per 
hour
 6 Amps/hr  12 Amps/hr  18 Amps/hr
 Typical Power Output 
(usable efficiency with MPPT** solar controller)
4 Amps/hr    8 Amps/hr   16 Amps/hr   24 Amps/hr 

 Weight of Solar

 10kg  23kg  46kg  60kg

*Assumes compressor refrigeration, dual water pumps
** MPPT stands for: Maximum Power Point Tracking

An alternative is the Smart Weight Saving of Lithium Batteries and Super-Thin Solar. Let’s see the Paired Weight Saving:

AGM Battery Capacity
(Lead acid in an “Absorbed Glass Mat”)

 100 Ahrs  200 Ahrs  400 Ahrs  800 Ahrs

Glass Monocrystaline Solar Panels

 100 Watts  200 Watts  400 Watts  600 Watts

Paired Combined Weight 

 50kg   100kg  200kg 

 360kg

 

 Lithium Battery at an Equivalent Size & Weight  6.8kg  13.8kg 27.5kg  55kg
 Super-Thin solar Weight  3kg 6kg 12kg 18kg
 Paired Combined Weight  9.8kg  19.8kg  39.5kg 73kg
 Paired Weight Saving 40kg  80kg 160kg  287kg

Lithium Batteries are very expensive but offer a lower cost per cycle than AGMs in most applications.

The benefit of the Lithium and the Super-Thin solar is significant weight savings as well as significant performance improvements and lower cost to operate.

Lithium Batteries have 96% charge efficiency, whereas AGM is 60%.

If you wish to run 12V Air-conditioning, there is no alternative than to use Lithium Batteries. 

Lithium Batteries and Super-Thin Solar are standard on the Kimberley Kruiser Range and the Kimberley Eco-suite.

For more information about Sizing batteries for your lightweight off-road caravan download the FREE guide below:

DOWNLOAD Solar and Battery Sizing Guide
Includes a set of lookup tables to calculate your needs.

 
Typical Power going
into Karavan
Comments
Charging While Driving
from 5A up to 35A
through Andersen plug
Charging at powered site
60A capacity
through battery charger
Charging from Generator
60A capacity
through the battery charger;
will charge whilst airconditioning is running
Charging from Solar Power
approx 15 A
from 220W Panels in peak sun
approx 20 A from 330W Panels in peak sun
approx 27A from 415W Panels in peak sun
Conditioning of Batteries

 

Typical Power going
out of Batteries
LED Lighting
0.8A
ALL LEDS ON
Refridgerator
1.6A
averaging less than 1A per hour
for normal 24 hour operation
startup is 3.6A
Diesel Cooker
0.9A (high)
average is 0.3A
Startup is 9A for less than a minute
Diesel Hot Water
1.9A (high) Average is 0.7A
Startup is 9A for less than a minute
Water Pumps
Average is 1.9A small
5amps large pump
Inverter Power
Depends on load, at 70% power, 75A
No of Days Energy Capacity with 330W solar on roof, no generator, no external 240V power with typical use calculated on average of devices power and typical hours of use
250.00 Ah Lithium Batteries
6 peak hours per day
4.75 days capacity
No of Days Energy Capacity with 415W solar on roof, no generator, no external 240V power with typical use calculated on average of devices power and typical hours of use 250.00 Ah Lithium Batteries
6 peak hours per day
5.75 days capacity