Not sure I fully agree with that Dave. Whilst voltage drop is certainly an important issue, of greater importance when using a second battery as a 'house' battery s the ability to charge it to 100% (or close to) of it's capacity. Simple alternator charging alone (via a VSR or not) will not get a battery charged beyond 70% or 80% in normal use. To achieve this a 'smart charger' is required, either in the form of a dc to dc charger, a solar regulator, or both. To ensure optimum life of the second battery it is best to keep it above 50% capacity. If charging via a VSR this only gives up to 30% useable capacity, compared to close to 50% useable capacity with a smart charger. For some who's power usage is low, this is not an issue worth paying the extra for a dc to dc charger, but for many the price paid for a VSR system is greatly shortened battery life, a result of 'over discharging'.Originally Posted by 3kids
Another issue with a VSR only system is that if the vehicle is used for most of the year without utilising the second battery regularly it can be overcharged. It is not unusual to see second batteries under the bonnet that are wet on top, a result of a battery that has become fully charged & gassing (an alternator will bring it to 100% eventually if it is not used). This is not good for the battery, or surrounding components under the bonnet. The solution is to regularly use the second battery.
On our bus I have a pair of batteries charged via VSR & topped up with solar. This has worked well for a number of years, but they have power drawn from them daily when the bus is in use.
Billy Bleed - apologies if this is a bit of a hijack of your thread, it is actually relevant, but I appreciate that you probably haven't got to the point of considering types of charging yet. Hopefully this current discussion (pun intended) will be of help when you get to that point.
Cuppa
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