Voltage Regulator power/sense wire

[sailorboy1]

I have a Balmar ARS-5 regulator that I installed this year. Watching it the other day I found that it goes into float too early (reset it by turning the key off/on). It is programmed for FLA batteries and the default voltages for that match my batteries. I noted that when it was in Bulk charge and the regulator says that the voltage is 14.6V that the battery really was only at 14.1V. That voltage difference is a big difference in amps into the battery bank.

I'm thinking the problem is that the Red "power" lead for the regulator, which is also its' voltage sense, is connected as standard to the output lug of the alternator. I'm thinking it would be better to move that wire to be directly on the battery.

Any problem with doing this?

[Maine Sail]

Originally Posted by sailorboy1

I have a Balmar ARS-5 regulator that I installed this year. Watching it the other day I found that it goes into float too early (reset it by turning the key off/on). It is programmed for FLA batteries and the default voltages for that match my batteries. I noted that when it was in Bulk charge and the regulator says that the voltage is 14.6V that the battery really was only at 14.1V. That voltage difference is a big difference in amps into the battery bank.

I'm thinking the problem is that the Red "power" lead for the regulator, which is also its' voltage sense, is connected as standard to the output lug of the alternator. I'm thinking it would be better to move that wire to be directly on the battery.

Any problem with doing this?

It may be sensing the alt because of where Alt B+ goes. V-sense and alt output must go to the same bank...

The regulator black wire is also part of the v-sense circuit so both red and black should go direct to the battery bank if you want target voltage at the battery...

[sailorboy1]

I wouldn't have thought of moving the black ground wire. Does it really need to go directly to the battery instead of the ground bus (which it seems would be the same regardless).

[Maine Sail]

Originally Posted by sailorboy1

I wouldn't have thought of moving the black ground wire. Does it really need to go directly to the battery instead of the ground bus (which it seems would be the same regardless).

If you can guarantee there is no voltage drop at high current then yes. Ideally with a shunt it should be on the "load" side of it as close to the battery as possible..

[Iaangus]

The "sense" wire can be connected anywhere in the 12 volt system. If you place it farther from the alternator you will compensate for normal voltage drop so yes, you should connect it somewhere down line or possibly after some relays or switches so you can compensate for the voltage drop in those components.

[smac999]

if you are losing 0.5v between the alt and battery bank a larger alt cable might not be a bad idea either. after you move the sense wire. you are just wasting power.

[sailorboy1]

Don't think I'm "wasting" anything really far as real life practical matters (am in theory but you could never measure such a loss). At the current I was at it comes to 10 watts, what does 10 watts matter when running a 54 HP diesel engine?

I'm much more interested in charging the batteries fully.

[sailorboy1]

Tomorrow I planning on running the sense/power wires over to the battery terminals. I don't see this as a circuit that really carries much current needing to think a lot of the voltage drop in the wiring so am just planning on 16 awg wire.

But correct me if this thinking is wrong.

[cwyckham]

Originally Posted by sailorboy1

Tomorrow I planning on running the sense/power wires over to the battery terminals. I don't see this as a circuit that really carries much current needing to think a lot of the voltage drop in the wiring so am just planning on 16 awg wire.

But correct me if this thinking is wrong.

The sense wire will carry just about zero current. Just make sure it and the ground on the sense circuit are routed out of the way. My ground wire was in a bad spot and got snapped off. The regulator went nuts. Took a while to diagnose that one!

[sailorboy1]

Well moving the wire to the battery worked great and made a difference


Sent from my iPhone using Cruisers Sailing Forum

[Maine Sail]

Originally Posted by sailorboy1

Well moving the wire to the battery worked great and made a difference


Sent from my iPhone using Cruisers Sailing Forum

The red wire for the ARS-5 can carry upwards of 7A, it powers the regulator and passes the power for the field for the alt. The black wire is usually less than 1.3A..

[sailorboy1]

Well I used 14AWG wire for the power/sense as that was what the regulator used. I didn't check for voltage drop when I did it, but now have looked it up and at 7 amps it is 2.5%. I think that is marginal and may replace it later.

But I also did the calulation for the voltage drop from the alternator to the house bank not counting any connection/switch loses. It came out to be around 2%, which is about 0.3V. Which explains a lot for why the batteries were showing such a lower voltage during charging than the alternator puts out.

But is doesn't appear that the voltage drop it in the regulator sense/power wire matters as much as the regulator must just boost the field.