Batteries have become a major component of many RVs, particularly those set up for independent living and remote country travel. In some ways, batteries have changed a lot over the last decade or so but in others things have remained much the same. For instance, a lead acid battery is still a lead acid battery and things like Peukert’s Law, established way back at the end of the 19th century, are still relevant. Most RVs still have a 12V system, but at least one manufacturer has started using 24V.
There are lots of misconceptions around batteries, so here I’ll take a look at some of the ones I hear most frequently...
1. ANY CHARGER WILL DO
Naturally, any battery has to be charged up, and more frequently if being used. In the good old days just about any charger would do but that has changed considerably, particularly with the evolution of multi-stage chargers. As noted above, some battery types require specific chargers for maximum functionality.
A complication occurs when batteries are charged from more than one source, ie., a mains charger, Anderson plug or solar panels. In the latter case, a regulator is essential and, in recent times, integrated power system units have been developed that manage all solar and battery systems, as well as having inverter output.
2. STARTER AND DEEP-CYCLE BATTERIES CANNOT BE USED INTERCHANGEABLY
While it’s recommended that neither battery be used for the alternate function, in an emergency, anything can be tried. Starter batteries can be used for an extended deep-cycle function but in order to prolong battery life, they need to be recharged as quickly as possible.
3. DEEP-CYCLE BATTERIES CAN BE DISCHARGED UNTIL THE LIGHTS DIM
Yes and no. Deep-cycle batteries are designed for extended periods of discharge but the battery life can be shortened if frequently discharged below the 50 per cent level. It’s a mistake to think that a 110Ah battery will give a 10A current for 11 hours. It won’t! They are the reasons why, prior to purchase, both battery and charging capacity should be carefully considered. An extra battery may cost more in the first place but it may well be cheaper in the long run. (See the article below on Peukert’s Law.)
4. BATTERY VOLTAGE IS A GOOD INDICATION OF STATE OF CHARGE
Not always. When a battery is flat, yes it can be. However, a good battery that has been used extensively may show a slightly lower than usual voltage but still be fully chargeable. On the other hand, a dud battery may show a high voltage after being freshly charged but that won’t last for long. Unfortunately, there is no easy way to determine a battery’s state of charge, but a good battery management system and even some solar panel regulators can do this for you. Most work on the principle of measuring what energy is going in and what is coming out and doing the maths accordingly.
5. LITHIUM BATTERIES ARE TOO EXPENSIVE TO BUY
This depends very much on intended use. If, for example, extended outback touring is planned using an inverter for 240V supply then lithium batteries may well be cost effective.
Fridges, too, which have problems with low voltage operation, are definitely going to function better. In addition, the lighter weight and smaller space requirements of lithium batteries – like a third to a quarter of that required by a deep-cycle battery – makes them suitable for smaller RVs of all types.
6. LITHIUM BATTERIES AREN’T AS SAFE
In recent times there has been some publicity over lithium batteries used in Boeing 787s, of all things. For anyone with concerns about this, the good news is that those batteries (a lithium cobalt oxide) use a different chemistry to those used in an RV’s lithium ion battery.
WHAT DOES IT ALL MEAN?
After reading all this, you might just be wondering which battery system will suit you best. Without doing any serious load calculations/cost benefit analysis, I’d suggest that a well set up gel/AGM system will currently work best. But, in the next few years, development of lithium battery systems will almost certainly make them more cost viable, and even more so when considering weight and space.
Although the basics of batteries and battery charging hasn’t changed, much of the technology certainly has. For vanners, lithium batteries will continue to be an emerging field and one that I would suggest has great relevance and should be watched closely.