VSR and CTEK MXS

Gixer

Gixer

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My rewiring Is going well and I’m ready to fit the VSR.

When charging my battery from the mains hookup I use a CTEK Charger which I connect directly to the battery. I alternate between the two batteries I have on a weekly basis.
From what I have read and understand of a VSR it kicks in when the voltage reaches a set level. So in theory should I be able to leave the CTEK connected to one battery and it keep both battery’s topped up?
 
How does the Ctek charger decide when the batteries are charged?
Will the VSR confuse this?

I think it will be OK, but if they were my batteries, I'd want to be sure!
 
If the VSR is fitted in the usual way, giving charging priority to the engine start battery, then the Ctek must be connected to that battery for it to work.
 
TernVI said:
How does the Ctek charger decide when the batteries are charged?
Will the VSR confuse this?

I think it will be OK, but if they were my batteries, I'd want to be sure!
Click to expand...
Norman_E said:
If the VSR is fitted in the usual way, giving charging priority to the engine start battery, then the Ctek must be connected to that battery for it to work.
Click to expand...

The battery which has the highest priority is the one to which the charger is / should be connected.
When it has charged sufficiently for the volts to have reached the cut in volts of the VSR it will close and connect the other battery. Both will then be charged in parallel.

Most modern VSRs are dual sensing which means they equally sense both batteries. This allows for one charging source to be connected to one battery and a another to the other battery.
The alternator will usually be connected to the engine start battery. A solar, or shorepower, charger can be connected to the house battery.
 
Contrary to common belief and some VSR manufacturers bullshit, there is no priority battery. Some manufacturers claim that the VSR does not close until the priority battery is charged, this is extremely misleading. The VSR will close as soon as it detects a voltage at either battery (in the case of a dual sensing VSR) tat exceeds the VSR voltage setpoint, this is usually very shortly after the charging source starts charging, in the case of the mains charger, within a very short time of it being switched on. In practice it often doesn't make any great difference which battery the mains charger is connected to. In extremis, if the domestic bank was large and very depleted, it might take a few minutes for a small charger to bring the terminal voltage up to the VSR setpoint, so the engine battery would have to wait for those few minutes to be getting any charge. But, the engine battery shouldn't need much charge anyway. If, on the other hand, the charger was connected to the engine battery the VSR would close very quickly and the domestics would be on charge too.

In short, in the real World, (especially for the OP) it isn't going to matter much which battery he connects his mains charger to in terms of charging and yes, it will charge both batteries.
 
I agree with Paul Rainbow the VSR senses the voltage at the battery being charged. This voltage will always be greater than the inherrent voltage of the battery and it is the inherrent voltage of the battery that is related to charge state. So yes if the first charged battery is very flat the voltage across it even on charge will be low for some time until it gets some charge. Only then will VSR operate. This of course depends on the exact voltage that VSR is set to. So mostly a VSR is set to around 13 volts so clearly defining the difference between a well charged battery and one being charged. The concept of only connecting the next battery when the first is fully charged is only true to a very limited extent. Not that it matters, because they are both being charged ol'will
 
A small caveat might be, if you have a very large capacity house bank which is very flat and your charging source is connected to the starter when the VSR makes it will drag the voltage down. There should be enough hysteresis designed into the VSR to remain made in this case but only the documentation will tell you what that is. If there isn't enough you will get a chattering VSR which isn't good. This can be negated by connecting your charger to the biggest battery bank.
 
My domestic/leisure battery is only 80ah and my engine battery when I buy it will be about the same but a start battery. They will both be new so I guess I’m eliminating must complications.

thanks again.
 
Interesting points on this thread. The only VSR that I have used said that it worked one way, and I did away with it in favour of a two output charger. One that connects if either batter is sufficiently charged looks a better idea.
 
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