Battery Choices (House vs Start)

[Catigale]

On the economics side, it makes sense for me to buy two cheap group 24 and use the extra money for a emergency starter battery - the portable kind. You can buy one now for about 75 USD on sale with an inverter, a compressor and a worklight too!

Best part is you can buy it in the winter up here in the NE, put it in the Admirals car for NOV-MAR, and put it in the 'I look out for you' budget instead of the boat budget.....of course, after 20 years of marriage she still rolls her eyes and recognised a boat gadget right away...

[kziadie]

Catigale,

As the guy in the Guiness commercial would say... brilliant!!!

Kelly

[beene]

Part of an Admirals qualifications is to be able to see right through a Capt's motives.



G

[Boblee]

Mine learnt to doubt my motives when I bought her a cement mixer for her birthday and a wheelbarrow for her next one
Well they were for her shed and garden.
Aya
Seems young uns all round the world are exploring other countries, when travelling around we have encountered thousands of backpackers and others but not that many aussies.
Our young uns seem to want to travel extensively and are fairly laid back.
If you want to see the best ones you will have to come out here, we don't let them out, only the Elles and Olivias are allowed to travel.

[beene]

Question...

If I have all accessories wired to house batt, both starter and house batt wired to a Perko switch, leave switch on both......

.... will my starter batt be drained when using accessories in the boat, or is it isolated from the house batt

I am trying to keep the starter batt isolated by using the perko switch for charging both batts.

Tks

G

[Chip Hindes]

With the switch on "both" the batteries are both connected in parallel and there is no isolation; if you discharge them both will discharge equally and they will both be dead.

On the other hand, for both batteries to charge the switch must be on "both".

In an ideal world, you switch to one or both to start the motor, leave it on both awhile to charge the batteries, then change the switch to 1 or 2 to run your loads. If you inadvertantly kill the battery, only the one which the switch indicates will die.

The battery you're not set to will remain charged; switch to it to start the motor.

You must also remember to never switch to "off" with the motor runnning. Some alternators will instantly fry with no load. Is yours one of them? (i.e., don't try this at home).

In a real world, you will forget to switch to 1 or 2 or you will just give up and leave it on 1 or 2 all the time and the battery not switched to will eventually die from disuse.

That's the beauty of the three switch system with VSR. Normally, both switches remain on at all times, but regardless of switch position both batteries are charged.

[beene]

Thanks Chip

I was afraid of that.

Looks like I am going to have to buy that Combiner from WM.

I can't see any other way around it to make it a no brainer, where human error can't screw it up.

If I have to remember to switch from this to that all the time, I am bound to screw that up.

G

[Boblee]

Beene thats exactly why mine is on an off, 1,2 or both switch incidently even when my present setup is left on both there seems to be very little draw down because of different batteries as predicted by the experts (not here).
The biggest problem we had with batteries when we first started travelling was to get consistent advice as none of the experts who should know about battery problems gave the same advice.
I am/was an electrician for 45 years but nothing prepared me for the BS I encountered from battery manufacturers, suppliers and auto elecs.

(edited) Re the above could quote plenty of examples of the above advice but a classic was one of my best mates boats a 5.5m tinny rigged for Barramundi fishing in our top end. He had just spent over $2000 Aus on rewiring with the main concern being keeping the beer and fish cold but on it's first trip it failed dismally.

On the second trip I was invited along and finally relented after years of saying no, one quick look was all it took to see the basic problem. Despite having a solar panel, generator, battery charger and two large and expensive marine batteries with a smart regulator etc, all very expensive. The wiring to the fridge points was only one 6mm pair looped between outlets, now this is ok if the batteries are at full charge 12.8v-14.2v but once it dropped below 12.2v which is basically anytime they weren't on charge the fridges would cut out from low voltage as they were drawing about 7-8amps all up.

We had a day in Darwin packing prior to heading off so bought some gear (got out of packing ) and wired each dedicated fridge point on boat and in back of vehicle with two x 6mm pairs (couldn't get heavier) and run 2x 6mm cables between vehicle and boat for charging while travelling (1000 + klms or 2500 round trip). Very simple solution but sometimes what works in theory is not practical when applied.

Note the Beer was icy cold and the fish was frozen for the entire two weeks without exception and with no need to keep fiddling, it was interesting that over the previous seven years of doing these trips his boats despite continual rewiring (huge costs and drama) had never been able to acheive this?.

[beene]

Hi Boblee

I am no electrician, how could I test to see what drain, if any, is happening to my starter batt when switched to Both?

Say I load up all Acc's, lights, everything elec I have, switch Perko to Both, how would I read a drain on the other batt? I have a voltmeter, just never used it for anything except reading voltage levels.

G

Did I just answer my own question?

[Boblee]

If you want to check the load on individual batteries you need an ammeter in the line of each. The load will vary depending on the charge state of either battery and if they are the same type of battery.

All things being equal they should discharge at the same rate ie 1/2 full load current but if one was higher it will pump more as it also tries to equalise the other battery. If one is sick it will not contribute equally either eg crook cell.

Also you can use a voltmeter and if the battery voltage of each was the same to start with over a given amount of time with the same load they should discharge the same amount ie have same voltage. This is fairly general and it will depend on what you are trying to find. Some battery types will discharge others if left coupled for long periods but I haven't had this problem (yet).

Where there is a problem is if you are using eg calcium battery which accepts a fast charge and you are coupled to a deep cycle ie slow charge, you may initially have a higher voltage after short charging but they will eventually equalise to a lower voltage. I don't have this problem as they are constantly being slow charged by the solar panel, I have two voltmeters one on the solar regulator and one at the distribution panel with an ammeter. Hope this helps but there are a few variables and it depends what you are trying to find out.

Just reread your post again and if you wanted to check if one battery was charging another you would use an ammeter in one of the coupling leads at nil circuit (lights etc) drain.

[beene]

Thanks for the info.

G

[bastonjock]

another easy way to check the draw on a cable is to use a tong tester,its a clamp that you can just place the cable through and read out the digital meter to see what the particular piece of kit is drawing.These days they are relativley cheap,some digital meters come with an additional "tong" attachment.

[kziadie]

Up to now, I've judged AGMs too costly.
However, the fact that an AGM continues to operate when submerged ...
Might mean that an AGM comes aboard at my next opportunity;

I dont mean to dispute this, but I am puzzled as to how this is possible. Even if the battery could internally function, once the terminals are under water wouldnt they short out?

Kelly

[Boblee]

baston jock I never found a cheap tong tester but have not been actively practising for a few years, the one I have was worth over $300 AUS but you are probably correct as everything is changing. Most of the cheap little multimeters can test 10amps in line.

Probably as Frank said if you wish to keep a log etc you will always know if a battery is going down by using the odd even method but even then you would have to be sure the time used and the load is the same before being sure.

Kelly - Clean water is not a good conductor and even salt water unless the terminals are close together probably wouldn't short at least quickly, but for eg if left submerged could create a carbon track as it slowly bleeds.
Bob

[kziadie]

Interesting... one of the items on my emergency checklist in case the boat was taking on water was to disconnect the non-house battery and take it topside so that I could hot wire the radio if it came to that. I will probably still leave it on the list but assign it a lower priority.

Kelly