Dual Battery Systems - Article 09-2013...
It is advisable to read the first article: "Dual Battery Systems - The Beginning" before reading this article, to get a clear understanding of certain information given in this article.
What will be covered in this article?
1. Do I need a DC-DC Charger in my dual battery system?
2. What are the advantages / disadvantages
of a DC-DC charging system?
The auxiliary battery is a power source for all the appliances used while camping, without using
the vehicle engine/starting battery.
The auxiliary battery needs charging, how do we do it?
Running the fridge, lights
and other DC accessories, use the limited energy stored in the battery, and the battery will stop supplying power eventually if it
is not re-charged.
1. Do I need a DC-DC Charger in my dual battery system?
The most cost-effective system, relating to power output performance, is the
dual battery charging system fitted to the vehicle. The vehicle alternator is the powerful source used to re-charge the battery of
the vehicle while driving. The alternator can also be used to re-charge the auxiliary battery, by means of a dual battery charging
controller. Read more about the MacroMaxi Dual Battery Charging Control System. This system supplies 45 Amp (and limited to 45
- 48 Amp) from a standard 70 Amp alternator.
The theory around DC-DC charging is that it allows charging of higher voltages (in
the Boost voltage ranges) than what the normal standard alternator of vehicles can supply - although some vehicles already have smart
alternators that allows for charging up to 14.8 V for a period and then settle lower at 13.3 - 13.6 V.
In reality, if you only
use 15 - 20 Amp DC-DC system, it does not really help you, unless you are driving for 8 - 10 hours per day. In fact, the 20 Amp recharge
current supplied (if we assume that it will run at its maximum the whole period, which does not really happen) takes minimum 5 hours
of charging to get the battery above 95% full.
If you look at a standard alternator voltage of 13.8 V - 14.2 V, and you can apply
the voltage to a discharged battery at around 30% state of charge, you can charge at 40 - 50 Amp initial charge rate, for at least
the first hour, and then average 26 Amp in the second hour, meaning that you have recharged over 75 % of the battery capacity
back into the battery in the first 2 hours of charging, while the DC-DC at 20 Amp would only have done 40% maximum. The
only time a DC-DC of 20 Amp is going to benefit you, is if you run the vehicle engine for 8 - 12 hours per day, or driving very long
distances, and it will only start to benefit you after the 7th hour of charging.
So tho answer the question if you absolutely
need a DC-DC charging system;
1. Normal lead acid deep cycle battery - No
2. AGM Type batteries - No (although that there
are some claiming that the alternator can not re-charge these batteries, if you look at the datasheet, the float voltages are 13.6
volt still, and boosting from 13.8 - 14.8 V is recommended, you can still charge 95% of the battery capacity with a standard alternator.Which
in the camping application, is good, very good. You can always come back at home and boost the battery a short while and float for
a day if you really need the extra 5% back into the battery, with a proper charger working from 230 V AC mains.)
3. GEL technology
batteries - This is dependant on what battery you use, but most of these can also be charged by standard alternators.
To be continued
soon...
Key benefits of PBE Dual Battery Charging Systems (alternator charging):
Cost-effective - High power output, reliability, extremely
low maintenance, long serivce life
Very low risk - The PBE Dual Battery Charging Control system risk of failing is extremely low
High
reliability - The PBE Dual Battery Charging Control system is highly reliable
High power output - The PBE Dual Battery Charging Control
system ensures high power charging
Safety - The PBE Dual Battery Charging Control system incorporates various safety & protection
features
Alternator Protection - The PBE Dual Battery Charging Control system protects against alternator overload
The auxiliary battery is re-charged by using the following options independantly, or in conjunction with each other, working
together as a system:
4. Battery to Battery
chargers - PBE system - see PBE Energy Transfer Unit (ETU)