VSR / VSS - unbalanced charging danger?

[Tintin]

If one were to use a VSR or VSS instead of a bog standard splitter diode, with an engine battery of (for example) 70a capacity and a house bank of 250 to 400a, would there be any issues regarding unbalanced charging or overcharging of the engine battery when both banks are automatically receiving charge?

My understanding is that it is an issue even when using diodes if one were to have differing capacity batteries in the same house bank e.g. 2 x100 and 1 x 60.

 

[pvb]

If one were to use a VSR or VSS instead of a bog standard splitter diode, with an engine battery of (for example) 70a capacity and a house bank of 250 to 400a, would there be any issues regarding unbalanced charging or overcharging of the engine battery when both banks are automatically receiving charge?

My understanding is that it is an issue even when using diodes if one were to have differing capacity batteries in the same house bank e.g. 2 x100 and 1 x 60.

If anything, it's less of an issue with a VSR, although it isn't a major issue anyway.
.

 

[halcyon]

If one were to use a VSR or VSS instead of a bog standard splitter diode, with an engine battery of (for example) 70a capacity and a house bank of 250 to 400a, would there be any issues regarding unbalanced charging or overcharging of the engine battery when both banks are automatically receiving charge?

My understanding is that it is an issue even when using diodes if one were to have differing capacity batteries in the same house bank e.g. 2 x100 and 1 x 60.

The charge current is set by the battery / batteries, not the charge source. That was the theory behind how a VSR works.

If say your service batteries are low, the charge voltage set by the service batteries will be lower than the charge voltage of the engine battery, so not enough voltage for chemical reaction and no charge to engine battery, until service charge voltage comes up to the engine charge voltage.

Mixing types can be a problem, and charging 2 x 12 volt batteries in series can be a big problem for miss-matched battery capacities.


Brian

 

[nigelmercier]

It only becomes a problem if you have twin (or split output) shore-power chargers. That's why I modified my VSR wiring so it only operates when the ignition is on.

 

[halcyon]

It only becomes a problem if you have twin (or split output) shore-power chargers. That's why I modified my VSR wiring so it only operates when the ignition is on.

Can be, butt depends on the charger design, with ones that have a single regulator and a diodes slitter it has no effect, same as commoning outputs for a single battery bank.

Got round the problem in the 80's by making a mains charger that interfaced with the VSR, it charged the service battery 14.2 volt, then engaged the relay to charge engine battery, then dropped to 13.6 volt float.

Brian