Battery care

[Harry Bloomfield]

My caravan's mover lead-acid battery finally died, quite suddenly, last week. I don't remember doing it, but I had written the purchase date on it - July 2011, so that's close to 13 years old, and it had 'seen' two caravans. It was nothing special, just a cheap 110ah sealed cadmium, lead-acid, liesure battery, however its long life, helps confirm my treatment of it, was the correct way to go. The treatment was....

The caravan was never used off mains hook up, apart from when the mover was used, to get it in and out of the long slope of my drive. Whilst parked and unused, the mains power and 13.8v charger/PSU was always left on, but the 110ah battery was isolated from the 13.8v, except - every couple of months, the battery would be reconnected to the 13.8v, to top it up.

 

[Wayners]

Leisure batteries are different to car batteries and you can flatten them but they will charge up again.
They won't push out loads of amps though.

 

[ericmark]

Lead acid can be split into floated with ability to top up electrolyte, and further split into traction, and vehicle starting, and leisure is half way. For sealed, it can be just a lot of electrolyte, or absorbed glass mat also called valve regulated lead acid.

Self discharge, and built up of sulphur varies a lot, but to charge with a smart charger seems to be the way to go for long life. They are not all the same, but basic design it to charge until 14.4 volt and then stop until the voltage goes under 12.8 volt, so the battery gets a pulse of charge.

However, BS7671:2008 may have changed since then, gives a maximum voltage of 14 volts (A721.55.4.1) but most stage battery chargers will exceed that, and my battery charger will not return to full output once it has dropped through the stages. The latter model will, but to get a battery charger which will allow the battery to be used while it is being charged, needs an MPPT type which in the main are only used with solar and wind turbines.

The lithium battery can charge so fast and of course discharge, that there has been a move over to them. Units like these

are replacing the leisure battery. The lead acid with a caravan needs even with a stage charger around10 hours to recharge from 10% charge, where the lithium looking at 1.5 hours.

No longer have a caravan, and I would use AGM if I did, but £80 to £250 is a huge jump.

 

[Harry Bloomfield]

Leisure batteries are different to car batteries and you can flatten them but they will charge up again.
They won't push out loads of amps though.

The wisdom suggests, not to use more than 50% of the capacity of a leisure battery, or it will drastically reduce the life.

 

[SUNRAY]

The wisdom suggests, not to use more than 50% of the capacity of a leisure battery, or it will drastically reduce the life.

In the old days they were called 'semi traction batteries'.

Traction batteries were designed for deep discharge, ie to totally flat or zero voltage and fully recover,
Semi traction batteries were built with lighter plates and not designed for the same punishment so had a minimum discharge voltage, the ones I had were 1.2V per cell but it varied between make, model & capacitiy. They also had stricter charge & discharge current limits than traction batteries.

50% is a sensible figure to aim for which I guess will be around 10V (for a 12V battery) but my deep knowledge on these things is very dated and I'm sure technology has changed since. I currently run 2 x 80AH and 2 x 115AH or so leisure batteries for portable power (public address and 2 way radio) and are all very elderly, I think I already had them as standby for a job I first did in 2013 and my 'ACT capacity meter' is now telling me they are around half capacity although all of them will successfully run radio repeaters well beyond that limit.

 

[morqthana]

A radioisotope thermoelectric generator is what you need for radio repeaters.

Or maybe not.

 

[ericmark]

I remember my early years with lead acid, there were loads of war surplus GEL batteries, and some lead acid used methods which would not allow any fast discharge, and the traction battery and batteries

used for back-up power in telephone exchanges had at least a 25-year life expectancy. In 2010, we still got milk with one of these

I asked why, and he said so much easier to get in and out of driver's seat, no doors to open, what time lost getting from depot to first/last house on the round, gained doing round faster.

 

[robinbanks]

I think you've done well. You could consider a lithium based equivalent but not sure it'd be worth paying the premium if you're getting more than 10 years out of a lead acid

 

[ericmark]

I had to change the VRLA in the mobility scooter after 15 years, one cell went short circuit and baked the rest. But with a caravan leisure battery, 20 years seems common. But in the main down to charger, my mother's stair lift needed new batteries every two years, a meter on the charger showed 30 volts, so 15 volts per battery, but father-in-law different make, showed 27 volts, and his batteries would last far longer.

Mother the more used the longer they lasted, which makes sense, as not overcharged for as long.