[Col]

I am mostly trad but use the wfp once or twice a week.
Recently I fitted a voltmeter to keep an eye on the battery voltage.
I disconnect the battery in between jobs and take it in for a bench charge when it needs it.
Now go easy on me here but when I connect the battery up the reading is 12.7v but when the pump is running drops down to 12.2v then creeps back up after I switch the pump off.
Am I right in thinking it is the resting voltage I should be noting to see when it needs charging and just ignore the working voltage?

[Shrek]

My battery is 13.1 in the morning, early afternoon it’s down to 12.1 , only had it 6 months

[Don Kee]

[dazmond]

My batteries read 14.1 when I start my diesel heater with engine running first thing....

Under load(electric reel and heater running and towards the end of the day it can go as low as 12.2 but goes back up to 12.6 when I turn my heater/pump off)

My batteries are nearly 5 years old

[Spruce]

It is amazing how battery manufacturers can't agree how voltage readings and a batteries state of charge relate.

My chart says; 12.7v or higher = fully charged.
12.5v = 75% charged
12.4v = 50% charged
12.2v = 25% charged
12.0v or lower = fully discharged.
Reading should be taken after 4 hours of rest.

The o/p doesn't give us any info on his battery's capacity, make or age.

A fully charged battery reading doesn't actually tell o/p much about the remaining capacity of his battery. A fully charged 110 amph leisure battery could well-read 12.7v or higher, but might only have enough capacity to run his pump for a couple of hours. This reduced capacity is due to sulphation.

Spring and Varistream flow controllers are programmed to shut the controller off when the battery voltage under load reaches 10.5v. Under load, the battery is regarded as being fully discharged at 10.5v. Webasto and Eberspatcher diesel heaters also use 10.5v as the cut-off point.

If Col Googles NCC Verified Battery Scheme he will see some battery manufacturers who have contributed statistics to their battery's longevity in charge cycles to a 50% Depth of Discharge (DOD). It's not only recommended that our batteries are recharged as soon as possible after they have been used, we also don't use more than 50% of the batteries stated capacity. So my 105amp leisure battery only has a useable power supply of 52 amps.

Only recharging a battery when it's low on charge will reduce is capacity and battery longevity.

[Spruce]

My batteries read 14.1 when I start my diesel heater with engine running first thing....

Under load(electric reel and heater running and towards the end of the day it can go as low as 12.2 but goes back up to 12.6 when I turn my heater/pump off)

My batteries are nearly 5 years old

That's because the van's alternator is not only supplying all the current needed to start your diesel heater,  but it's also providing a higher voltage to be ready to charge your batteries.

My Peugeot Boxer's alternator has a voltage output of 13.9v. My battery to battery charger boosts that charge voltage to 14.2v which is what is recommended for maintenance free batteries. My old leisure battery was a flooded type, so I could charge that battery at 14.6v.

Your battery to battery charger is doing the same thing.

[Don Kee]

It is amazing how battery manufacturers can't agree how voltage readings and a batteries state of charge relate.

I only usually use it as a a guide to be honest Spruce (in fact I had to fish that out as I hadn’t looked at it for a long while)

Battery to battery charger tends to keep mine topped up, with a bench charge once a week when there’s two of us.
Rare that I check the voltmeter unless I think the batteries on the way out, and as you say the voltage doesn’t really give an indication on how much capacity the battery is holding.

[Shrek]

Which battery do you guys find best? Iv had this battery since December 2021 and some days it’s down to 11.8 by the end of the day. Got it from the local car shop for about £100