Adding a second battery

[pedro]

Hi i have one 110 leisure battery at the moment which is gell can i add a second batt which is 110 but acid along side the gell battery can anyone advise

[spospe]

pedro

 

It is not advisable to mix gel and liquid batteries in parallel because they have different charging requirements. For example the peak voltage to fully charge a gel battery is usually quoted as being 14.4 volts and for a liquid version 14.7 volts.

[Derek Uzzell]

Pedro

 

My Exide leaflet advises that SERIAL-connection of gel and 'wet' batteries is not permissible.

 

The leaflet states that gel + wet PARALLEL-connection is permissible as long as a 'separator relay' is used. (In fact, this is commonplace on many motorhomes having a gel leisure-battery and a wet engine-battery that are connected in parallel when the motorhome is being driven and both batteries receive charge from the vehicle's alternator.)

 

However, as sposne says, the optimum charging regimen is different for gel or wet batteries.

 

The instruction leaflet for the CBE-made on-board battery-charger fitted to my Hobby indicates that, when the charger's GEL-battery setting is selected, the charger operates as follows:

 

Stage 1 - Charges at 14.3V until end-charge voltage is reached.

Stage 2 - Charges for 8 HOURS at 14.3V.

Stage 3 - Charges for 10 hours at 13.8V.

Stage 4 - Ceases operation until battery voltage drops below 13V.

 

When the WET-battery setting is selected the charger operates as follows:

 

Stage 1 - Charges at 14.1V until end-charge voltage is reached.

Stage 2 - Charges for 90 MINUTES at 14.1V.

Stage 3 - Charges for 10 hours at 13.5V

Stage 4 - Ceases operation until battery voltage drops below 13V.

 

It would seem from this that one should be able to use gel and wet batteries connected in parallel as a leisure-battery system as long as the less rigorous wet-battery charging regimen were selected, the downside being that the gel battery would never be fully charged. Choosing to use the gel-battery charging regimen would risk 'cooking' the wet battery and there have been letters in MMM magazine about this happening.

 

In practice, you'd be unwise to connect your gel and wet batteries together.

 

(Exide also advises that, when parallel-connecting 'new' and 'old' batteries, the oldest battery should be no more than 1 year older than the newest. Also that, when parallel-connecting 'small' and 'large' batteries, the ratio of their capacities should be no greater than 1:3. (eg. 60Ah + 110Ah should be OK, but not 60Ah + 200Ah.) Having said that, the usual (and safest advice) is to always match like with like - same types of battery having a similar age and capacity.)