Q Can I keep my starter battery topped up?
I have a Shire Conversions Phoenix 2 on 3-litre Fiat Ducato Maxi LWB, 2013. I have recently replaced my lead leisure batteries with a single 230Ah under-seat lithium battery. I was advised also to fit a battery-to-battery charger, replace the mains charger with one with a lithium setting and swap the PWM solar controller for an MPPT. All done, professionally.
Knowing that lithium batteries should not be left or kept fully charged for long periods, I decided to use the solar panel to top up the starter battery over winter. The converter fitted a Victron 75/15 MPPT and I asked for a three-way changeover switch to isolate the lithium battery from solar and connect the sealed lead acid starter battery instead, using the Victron app to adjust its settings accordingly.
But the Victrons pre-programmed battery types do not include flooded or sealed lead acid, only a variety of AGM and gel types, plus smart lithium. Advice from the supplier to my converter was to set the Victron to a particular type of gel, bulk 14.4V float 13.8V and equalisation (I take that to mean desulphation) of 16.2V
I am nervous of using this setting. First, I don't want to cook the battery, especially as it is sealed.
Second, I have had to have my airbag/seatbelt module reprogrammed once already – the report said it had been exposed to a voltage of 14.7V I don't want to disconnect the starter battery long-term for charging, nor do I want to expose all the permanently connected electronics to 16.2V – indeed anything over 14.4V
The Victron has an ‘expert’ mode, so I should be able to create a ‘user’ profile – but what settings should I use? And do I need to do it anyway?
Or could I simply allow the starter battery to be topped up on the lithium setting? That is bulk 14.2V float 13.5V and equalisation disabled; although not ideal, it should mean the Van would start, compensating for the various low drains of alarms, etc.
Your expertise and advice would be much appreciated.
Mike Clark
A It sounds as if you have given your wallet a thrashing!
You need to be careful interpreting what you read, as advice for lithium-ion batteries and lithium iron (LiFePO4) batteries is not the same. They differ in several respects.
The lithium-ion batteries used in phones, electric bikes, mobility scooters, etc, provide a greater terminal voltage (3.6V to 4.2V per cell) than the LiFePO4 type we use for leisure duty in motorhomes and caravans. Also, they have a greater energy density, which is what makes them attractive.
That can be at a cost of safety as these lithium-ion batteries can catch fire if overcharged. They are not allowed on most aircraft and, when they are, they must be below 50% charge or even lower.
The LiFePO4 Lithium iron batteries in motorhomes still have a very
