Battery isolator

Hi,

Most diode based isolators don't work nearly so well as a relay. They drop the voltage too much to allow the "house" battery to fully charge.

pianotuna wrote:
Hi,

Most diode based isolators don't work nearly so well as a relay. They drop the voltage too much to allow the "house" battery to fully charge.

I have to question that remark. I've used battery isolators for over 40 years, and they have never given me a moments trouble. The one relay I had to charge the batteries got so hot it would burn your hand if you touched it after 30 minutes of charging.

X2 what Don says

Its all in battery science now for deep cycle batteries...

If you hit a deep cycle battery with 14.4VDC at around 15AMPS current you can return that deep cycle battery back to a 90% charge state in as little as three hours of charge time...

If you hit the battery with only 13.6VDC at around 15AMPS current it will take around 12 hours to charge that battery back up to its 90% charge state.

When using the DIODE BASED ISOLATOR the 14.4VDC charging voltage will be dropped by .7 VDC which becomes 13.7VDC which will take almost 12 hours again to return the state of charge to 90%.

This is why deep cycle batteries have to use smart relays instead of diode based isolators to isolate batteries from being discharged...

something like that at any rate...

look up how the BLUE SEA SIACR smart relays work...

Roy Ken

The battery on the lower stud was reading 13.5 and the battery on the top stud was reading 12.0 . They read the same when batteries were changed around.

Ok I bypassed the battery isolator and have both batteries on the bottom lug and the batteries are charging will this hurt anything or can I leave it this way.

No problem as long as they know they will both charge AND DISCHARGE together.

Basically they just have one larger battery now.

There are basically 3 times something types of isolators..

Basic Diode isolators
Improved diode isolators
Solenoid/contactor/relay based isolators (Best)

With the basic.. These are designed to be used with an alternator, if the alternator is putting out say 14 volts. the batteries may see as little as 12, this is not enough to fully charge them (NOTE I am using round figures here) a good diode isolator may only drop a few tenths of a volt.

In improved isolator has a 3rd circuit.. this is to feed the vehicle or charger's voltage regulator.. HOWEVER not all alternators and darn few converters know what to do with that signal My Alternator for example has an internal voltage regulator and there is no way to feed the reduced voltage to it.

Solenoid type.. Do not have this issue.