Voltage sensitive relay

[gordonmillington]

I am considering replacing spliting diodes by a voltage sensitive relay for the charging of the starter and domestic batteries. Charging rate is determined by a Driftgate X-ALT controller. Any experience or comments?

<hr width=100% size=1>Fable

 

[VicS]

Do a search on the forums as there were some arguments about their merits a month or two ago. Also one of the regulars identified a possible pitfall. I can't remember the details so I'll leave you the pleasure of searching it out.

<hr width=100% size=1><font color=purple>Ne te confundant illegitimi.</font color=purple>

 

[halcyon]

Depends on which relay you fit, thus the spec.
Voltage sensitive relays, no volt drop, bi-direction operation allows solar panel/wind gen to charge both banks ( can also include overcharge protection ), link start parallels service bank for engine start if required through charge relay, high load drop out/engine start drop out. The engine and alternator allways remains connected to the engine battery, thus any failure in the split charge system will not lose charge to the engine battery. Adjustable voltage levels to customise relay to the boat's battery type, or requirement, The engine battery allways receives priority for charging.
Blocking diodes are cheaper, basic type, but low loss or zero loss get dearer than relays. Fixed operation, not bi directional so requires a lot of seperate components to acheive the same system. A diode failure can result in lose of charge to engine or service battery if open circuit, drain from one battery to the other if short circuit failure. Has an in built volt drop, resulting in 5-10% of alternator output going up in heat.

Brian

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[steve_cronin]

Personally I don't like VSRs but that isn't the point I want to discuss. What I want to raise is the idea of charging starter batteries from meagre sources like solar panels and wind generators. We are based in the Med and our two 55watt solar panels do manage to keep the fridge running (just) so if I were to divert any of the output away from the domestics (to me seemingly un-necessarily) to the starter battery, then our current sufficiency would no longer purtain.

If you've a good charge regulator on your alternator (Mine's the Sterling Pro), then half an hour's running a day (who does less?) will keep the starter battery full or near to full, anyway.

Steve Cronin



<hr width=100% size=1>The above is, like any other post here, only a personal opinion

 

[halcyon]

To follow up, the idea for charging engine battery is intended mainly for when the boat is unattended sitting on it's mooring. It cuts in roughtly at float charge, thus surplus power can be diverted to the engine battery, a) keeping it topped up, b) by increasing load on solar panel/wind generater it acts as a power sink thus reducing/stopping over charge.
With a programmed relay the engine battery is always charged first, thus always maintaining the starter battery in a good state. Without the volt drop in the blocking diodes, a lot of cases do not need a smart alternater regulater to maintain a satisfactory charge level.

Brian

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