[Steve Weatherley]

I had a split charge relay installed (by a well known installer to this trade) into my van back in August as part of an overhaul to my van mounted equipment. The problem I seem to have is that it only appears to keep the battery charged when the battery is already fully charged. Today when I started work at 8.00 it was fully charged showing 13.1 volts. By the end of the day it was only running at 12.3 - even though I made several short journeys which I would have hoped should have re-charged the battery. I am having to plug my seperate mains charger into the battery almost every night to charge up the battery which seems disappointing when I was expecting the relay to help avoid this problem.

Whe I spoke to the installer they told me that this was normal and if the battery is anything below 12.6 it wont be able to receive the charge.

I dont think this is right but wondered if other wc's experience the same problem?

[Clever Forum Name]

Sounds right to me.

Don't be fooled with short trips and driving.

I do 30 miles a day and it's not enough to top up with what I have used.

Usually charge twice a week.

If I had a 125ah bat I wouldn't have this issue

[Steve Weatherley]

Thanks for your response. Interestingly mine is a 125ah battery

[Peter Fogwill]

You have to remember that every time you start the van you have to replace that before anything can go to the system battery.  This time of the year is worse when your using lights, heater, etc, as even less is going to top up the system battery.

[Clever Forum Name]

A guy on here called spruce done all the maths.

I think an average battery can accept around 6AH charge an hour.

So with me driving 30 miles (an hour)

I am putting in around a hours worth of on the glass.

Plus all the little trips = another 4AH

So I am using around 25AH A day I think. So by we'd my battery needs a top up

[robert mitchell]

my mileage is usually between 5 and 15 miles a day and i have never had to top up my system battery .

Ithink there are a lot of variables involved , alternated power , current draw , type of battery etc.


i use a car battery rather than a leisure battery as these can accept a higher charge rate .

the car battery is 100ah £30 secondhand off ebay .

[Spruce]

You have to remember that every time you start the van you have to replace that before anything can go to the system battery.  This time of the year is worse when your using lights, heater, etc, as even less is going to top up the system battery.

.........and in the winter your battery can be up to 25% less efficient.

[Spruce]

my mileage is usually between 5 and 15 miles a day and i have never had to top up my system battery .

Ithink there are a lot of variables involved , alternated power , current draw , type of battery etc.


i use a car battery rather than a leisure battery as these can accept a higher charge rate .

the car battery is 100ah £30 secondhand off ebay .

I'm not sure how a starter battery differs from a leisure battery as far as charging rates are concerned.

I have noted a comment made by Webasto regarding the use of their diesel engine (block) pre-heaters that they should only be used for the length of time that is going to be driven to keep the vehicle’s battery fully charged. As it takes an average of 20 minutes to warm a cold engine to 75c they are saying that the following car journey mustn’t be less than 20 minutes. This indicates to me that a starter battery doesn’t accept a fast charge.

When I put the amp/volt gauge on a Transit Connect with an 85 amph leisure battery I found it charged at the same rate as the 120 amph leisure battery in my Citroen Relay.

I have an alternator triggered relay which starts charging the leisure battery immediately the van's engine has started. It makes no difference if the headlights are on and the engine idling or engine turning over quickly on the motorway without lights on as the battery is charged at exactly the same amperage. So it’s not what the alternator will put out but rather what the battery will accept.

The other 2 vans (Ford Transit Connect and Peugeot Partner) are both fitted with intelligent SCRs. On starting the van it takes around 20 seconds for the relay to switch on the charging circuit to the leisure batteries on both vans.

Experts in the field will tell you that a vehicle's alternator is designed to supply the power to all on board accessories when the engine is running. All the battery is there for is to start the engine. Alternators don't do a good job of charging batteries. They don't have to. What they do do, no matter how badly, is good enough for most of us in everyday use.

There are expensive electronic SCR relays out there (Google Stirling Products) costing a small packet which are designed to charge banks of leisure batteries on board ambulances. They use a very sophisticated electronic method of forcing these batteries to accept a higher charge rate. They also remove the alternators voltage regulator and replace it with a better system. With the NHS ambulances, they also replace the vehicle alternator with one that has a higher output. That system used to cost the NHS a couple of grand on each ambulance before fitting.

I had to call an ambulance out to the wife one night a year ago. The ambulance crew spent about an hour stabilising her and in all that time the engine of the ambulance was ticking over in the street.