Thick question 30amp or 120amp

I have a craapp quality smartcom vsr that is 30 amps want to get a durite 120amp vsr can anyone explain the difference between the amps does it mean the 120amp vsr will charge the battery quicker the the 30amp vsr?

Den said:

I have a craapp quality smartcom vsr that is 30 amps want to get a durite 120amp vsr can anyone explain the difference between the amps does it mean the 120amp vsr will charge the battery quicker the the 30amp vsr?

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All it means is that the internal electronics will handle a higher current or load.

The rate of charge going into the battery is governed by the resistance within the battery itself. I have a 90amp alternator in my van and have never seen the charge rate higher than 22 amps. This 22 amps is an initial surge current on starting the engine and drops with a few moments to around 8 amps after a full days work using a 110 amph battery.

A vehicle's alternator is brilliant at supplying all the electrical current your vehicle's accessories need. But it is a poor battery charger. It doesn't have to be good because the couple of seconds it takes to starting a diesel engine will take around 5 amph from the starter battery.

Just compare how quickly an intelligent battery charger will fully charge your leisure battery to the length of time you would need to drive to achieve the same results.

If you want to achieve a faster charge then you might need to consider a Sterling battery to battery charger, which has the attributes of an intelligent charger built into it. But limited driving  (like we do) won't be enough to recharge your leisure battery after a days work.

Nice one Spruce very well explained, you and many other forum member have honestly made my life a lot simpler, today I install an electric reel and was thinking of the battery usage that's why the original question.

thanks again.

Den said:

Nice one Spruce very well explained, you and many other forum member have honestly made my life a lot simpler, today I install an electric reel and was thinking of the battery usage that's why the original question.

thanks again.

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I see the photo. It looks good.

If you are going to add a second battery then you will need a bigger vsr. That Smartcom vsr won't handle the surge going into 2 leisure batteries imho. The other option would be to add a second Smartcom and only run the hose reel from that.

I would just see how you go first before you start upgrading the charging system.

You mentioned that you turned the adjuster pot on the relay and got it going again. Those adjusters are quite sensitive and its to adjust when the unit activates and when it cuts out. So if you know where the original setting was (position of the screw head) I would recommend to put it back there as it might mess your cut in and cut out parameters.

I don't know what the Smartcom cut in cut out parameters are (the remaining van isn't here for me to check) and they vary from manufacturer to manufacturer. My unit cut in is 13.3vdc and cutout is 12.8vdc. They are all in the vary similar range.

If you try to set it up using a voltmeter, you will find that the VSR could still be linking the batteries together for some time after the engine is switched off. This is correct. A nearly fully charged leisure battery will 'trickle' charge at between 14.4 to 14.6vdc (on my van anyway) which both batteries get. Once you switch the engine off, that voltage quickly drops to begin with as the the voltage across the battery stabilises, but it takes a while before it drops to the cutoff voltage. I find voltage stabilisation of my starter battery takes longer than my leisure battery, so there is a minimal drain of a few watts from the starter battery to the leisure battery. But its minimal.

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Going to take your advise, and see how it goes for now as tbh the split charge was keeping the battery topped up apart from one week every month where my work is quite compact I then just top up with the charger.