Battery Chemistry Battery Charging Module

Another great idea from Sterling, Patent Pending: GB1204145.5

The Problem:
Most boats or specialised vehicles have multi-battery bank installations. This type of installation can cause problems if the battery chemistries in the installation are very different from each other (i.e. gel and open lead acid etc), or the battery voltages may be different i.e. you may have a 12V charger and require 24V for 1 battery bank (or vice versa). Maybe even one battery may be 20 ft away from the charger resulting in massive voltage drops. A good example of this is a GEL battery bank for your starter battery bank and an Open Lead Acid battery bank for a secondary / auxiliary battery system and a 24V lead acid sealed for the bow thruster. This causes a problem for most multiple standard output battery chargers as they can only be set to 1 battery chemistry type and 1 voltage. The usual thing is to set the charger to the lower voltage chemistry which, in turn, reduces the potential performance of the charge on the other battery bank with different chemistries plus damaging the battery bank. For example, you could have a GEL battery requiring 14.1V and 13.5V float but also an open lead acid bank requiring 14.8V charger and 13.5V float. Obviously, the 2 charge cycles cannot be achieved at the GEL setting, the open lead acid battery bank will not charge at a high enough voltage and would end up sulphating the battery bank. This would result in premature destruction of the bank and a warranty failure on that bank as it was not charged at it’s recommended charging curve. If the 14.8V range was used to keep the open lead acid batteries happy then the premature destruction of the AGM battery bank would be assured as they would dry up. The warranty for these batteries would then be forfeited for the same reason as explained before.

There are 2 key different technical ways to do this:
1) Switch each output on for a period of time and convert that output to a different chemistry setting and scan through the outputs. This method is simple but, in effect, is a poor solution because for example, if you have a 60A charger then you can only switch on 1 output during a time frame this supplies reduced power to full batteries but starves the empty batteries of the time they need to harvest the full charger power potential during that time span. The result is, for example, a large domestic battery bank and an engine start and bow thruster bank would result in the 60A only effectively being a 20A to the main domestic battery bank in that scanning time frame.
2) 3 individually adjustable outputs, this is, by far, the best and only totally effective way of achieving this, however, in effect, you have to add an expensive output stage controller to each output resulting in a massive price rise (over 2-3 times the cost of the standard unit).  Its very unlikely that an OEM boat / vehicle builder would fit this type of product as standard due to the high initial purchase cost of such a unit.

The Sterling solution
The new Sterling module approaches this from the same angle as adding an output stage to each output. We effectively place in a box a voltage booster and the output stage from a digital charger. This means that the new device can be added to any of the output terminals of our Pro Charge Ultra (or most other competitor companies multiple output charger). This will allow the main 3 (or more) output charger to be set at the lower chemistry voltage for the likes of Gel, then, by adding the new Sterling Multi chemistry module to one of the outputs (must be connected to an output of a current limiting charger and cannot be connected direct to a battery (see fig 1 and fig 2). One can adjust that output to a totally different charging chemistry profile. The output voltage and charging curves are independent of the charger’s input voltage. This enables a totally different chemistry to be selected, this gives all the advantages of the multi chemistry charger without the huge extra cost, and can be simply retro fitted to any multi output battery charger (within the limitations of the product).

Advantages of this product

Which model suits my needs? Ensure that your current charger’s output is equal to or less than the rating of the product. I.e. a 12V 60A module can be used on any charger up to 12V 60A.
Will this product work on my multi output charger?
This unit requires there to be a live feed on the output terminal on the charger when switched on.
To Test: With the port in question, simply check there is a voltage of 13V+ (or 26V+) on that output. If there is no voltage on that output when the charger is on then the product will not work.

Note: This is a new product and a new concept, we have undergone all the tests we can think of with our products and some competitors products. However, this product constitutes a whole new era for battery charging and, as such, we are always curious with what happens in the real world. On going to press we are not aware of any multi charger this product will not work on, however, obviously we don't know, nor have we tested, every multi output charger in the world, both past and present. Therefore, to avoid disappointment please check as above. If this unit is not compatible with any product then please email us and we are happy to make a list (if any) to assist our valued customers.

The Battery Chemistry Module and the Battery to Battery Charger application are such a new and exciting field which opens a lot of previously locked technical doors. We feel we should dedicate a bit more time and space to trying to portray the aspects of this technology and point out the difference between the products and what other problems they may solve for you. The applications are truly endless: vehicle tail lifts, on board wheel chair charging, boats, cars, commercial vehicles etc. Due to the space limitations of this catalogue we must pick a particular area and focus description to that area, the previous page clearly shows where you should use a battery chemistry module. The article below shows where the battery chemistry module stops and the battery to battery charger technology takes over.

What is the difference between a Battery to Battery Charger and a Battery Chemistry Module?
There is 1 major difference and that is their ability to current limit. The battery to battery charger has full current limiting. The battery chemistry module has no current limiting ability (other than a fuse).

Current limiting is the ability of the product to internally limit the current which it will allow to pass through itself. This prevents damage to the unit and also allows total control of power through the unit. This is a great but expensive feature and accounts for a large proportion of the parts / technology and hence the extra cost in a Battery to Battery Charger as opposed to its lower cost cousin the Battery Chemistry Module.

Why does the Battery Chemistry Module not have current limiting?
The simply answer is it does not need it. As long as the product is used in conjunction with its design criteria there is simply no need for current limiting. I.e. we have rated the product to 60A continuous, then, as long as the current does not exceed 60A, the unit is okay. The best way to ensure that it does not exceed the 60A is to connect it to a battery charger which is already internally current limited to 60A maximum (or less). That way we rely on the already purchased battery charger’s internal current limiting protection. This eliminates the requirement of that expensive electrical feature to be duplicated in our product, allowing us to substantially reduce the product cost to the customer.

Give me an example of why current limiting is important?
Let us imagine a simple standard setup where we have the engine alternator feeding the engine battery which is then charging the auxiliary battery. The auxiliary battery has a large inverter or anchor winch on it. To connect the starter battery and the domestic battery we have one system which uses a Battery Chemistry Module and the other system using a Battery to Battery Charger. Lets take the Battery Chemistry Module system and turn the engine on, chances are everything would be fine initially, the unit would fast charge the domestic bank, however, when the anchor winch or bow thruster is turned on, a high current (200A) shall be pulled from the primary battery bank to the secondary battery bank. This shall exceed the rating of the BCM and the fuse will blow. The Battery to Battery Charger, on the flip side, has no problem with this, it simply says I can NOT give you 200A I am only giving you a maximum of 60A and that is it.

What sort of cost savings are we talking about?
In the region of 30-40% can be saved in parts, this is reflected in the purchase price.

What aspects would I factor in to make a technical purchase decision between the 2 different products?
If the battery chemistry problem is confined to the mains battery charger only and the charger is 60A or under (at 12V) - The Battery Chemistry Module is the product for you.
If you wish to cover the same problem from various charging sources: I.e. alternator and battery charging, in which case the current limiting aspect of the battery to battery charger will be the vital aspect to swing the product to the battery to battery charger.

Other reasons for looking at a battery to battery charger over a battery chemistry module.
You have a 150A single stage battery charger but want a different chemistry on a different battery bank, again think current limiting. You may, for example, have the main battery charger power going to your domestic battery bank (like a combi inverter charger) but, you may want to charge an engine starter battery. Then, only 20A may be required, so, our battery to battery 20A (BBW1220) charger will be more than happy even though it is exposed to a 150A + charger. It is happy because it current limits and does not care about the high current source. 

Long Cable Runs: Another typical marine problem is where the bow thruster/anchor winch battery is a long
way away from the charger. This results in expensive cable runs to try to compensate for
large voltage drops. The Battery Chemistry Module can be placed close to the distant battery
as it can accept a low input voltage drops (activates at 11.0V) but boost them up so the distant batteries
can get the correct charging curve both from the point of view of chemistry profile but also voltage scale.
For instance, you may a 24V bow thruster or anchor winch but only have a 12V charge.